CN1980751A - Rolling control method, rolling control device, control program and seamless tube of mandrel type seamless tube rolling mill - Google Patents

Abstract

A rolling control method of a mandrel mill, in which when rolling a pierced blank (S) in a finishing stand (# i) in each stand constituting the mandrel mill (M) is completed, the rolling position of first grooved rolls disposed in the finishing stand (# i) is moved outward, wherein, even when the pierced blank is rolled in an upstream stand (# i-2) in the vicinity of the finishing stand (# i) in the same rolling direction as the finishing stand (# i), the rolling position of second grooved rolls disposed in the upstream stand (# i-2) is moved outward, whereby a part or all of the ends and the like of the pierced blank can be rolled with high precision to a desired thickness or the like when the pierced blank is manufactured using the mandrel mill.

Description

Rolling control method, rolling control device, control program and seamless tube of mandrel type seamless tube rolling mill

technical field

The present invention relates to a mandrel capable of pressing a part or all of the longitudinal direction of a blank such as the end to a desired thickness with high precision without deteriorating the surface properties of the blank when manufacturing a seamless tube using a mandrel mill A rolling control method, a rolling control device and a control program of a bar-type seamless tube mill, and a seamless tube produced by the method.

Background technique

In the manufacture of seamless pipes by the Mannesmann-mandrel mill method, first, round steel or square steel as a raw material is heated to 1200 to 1260° C. in a rotary hearth type heating furnace. Then, use a piercer to pierce and roll the heated round steel or square steel through plugs and rolls to produce a hollow tube. Then, the mandrel rods are inserted into these hollow tube blanks like string brazing, and the outer surface of the hollow tube blanks is rolled with grooved rolling rolls by a mandrel-type seamless tube rolling mill consisting of 5 to 8 stands. Restraining and elongation rolling are performed, thereby reducing the thickness of the tube blank to a specified thickness. Then, the mandrel rod is pulled out from the reduced-thickness tube blank, subjected to sizing rolling, and the tube blank is shaped into a specified outer diameter by a reducing machine, thereby obtaining a seamless tube product.

Conventionally, each stand of a mandrel mill is provided with a pair of grooved rolling rolls arranged opposite to each other. In particular, a two-roll mandrel mill in which grooved rolling rolls are alternately arranged in different directions at 90° to the rolling direction between adjacent stands is most used. In addition, there are also 4-high mandrel mills that are equipped with four grooved rolling rolls at 90° to the rolling direction on each stand. Furthermore, it is also proposed to arrange three grooved rolling rolls that are 120° to the pressing direction on each stand, and to arrange three rolling rolls that are 60° to the pressing direction between adjacent stands. A proposal for a 3-roller mandrel mill for seamless tubes with alternate pass rolls.

Generally speaking, when a particularly thick billet is sizing-rolled by a reducing machine, there may be a thinning phenomenon in which the thickness of the end portion of the billet in the axial direction is slightly thinner than the thickness of the central portion. Therefore, in order to prevent end portion thinning caused by sizing rolling, Patent Document 1 discloses a rolling control method in which the mandrel mill In the elongation rolling process, the thickness of the end of the billet is controlled to increase, specifically, the pass rolling provided on the finishing stand of the mandrel mill The gap is set on the roll, so that the thickness value of the end of the tube after passing through the finishing stand of the mandrel mill is offset by the reduction in the thickness of the end of the tube in the axial direction caused by sizing rolling after the value.

However, when the present inventors carried out a tube rolling test according to the method described in Patent Document 1, they found that the axial end thickness of the tube could not be accurately adjusted to the desired thickness, and the surface properties deteriorated.

On the other hand, Patent Document 2 discloses a method for manufacturing a seamless pipe, in which the actual thickness value of the billet on the exit side of the mandrel mill is adjusted by matching the The opening amount of the gap of the grooved rolling rolls on the finishing stand of the rolling mill, etc. is adjusted, so that the billet can be rolled to the desired thickness with high precision. Specifically, for example, use a thickness gauge arranged on the exit side of the mandrel mill to measure the thickness of the tube blank on the exit side of the mandrel mill. When the thickness is small, according to the difference, the opening of the gap of the grooved rolling roll is adjusted to be larger, even if the pressing position of the grooved rolling roll is changed to the outside relative to the previous position, thereby improving the accuracy of the thickness of the seamless pipe .

However, when the present inventors carried out the billet rolling test according to the method described in Patent Document 2, they found that if the opening of the gap between the grooved rolling rolls is enlarged infinitely, the grooved rolling rolls will move outward infinitely. , so that the desired thickness cannot be obtained.

Patent document 1: Japanese Patent Laid-Open No. 6-190406

Patent document 2: Japanese Patent Application Laid-Open No. 8-71616

Contents of the invention

The present invention aims to solve these existing technical problems, and its object is to provide a mandrel-type seamless pipe rolling mill that can roll part or all of the end of the billet with high precision when manufacturing seamless pipes. A rolling control method to obtain a desired thickness, a rolling control device, a control program, and a seamless pipe manufactured according to the rolling control method.

The inventors of the present invention conducted intensive studies on the reasons why the billet tube cannot be accurately rolled to a desired thickness even by the method described in Patent Document 1, and the surface properties of the billet tube deteriorate. As a result, it was found that, in general, in the finishing stand of the mandrel mill (the stand on which the last grooved rolling roll is arranged at the same position in the circumferential direction of the billet), in order to make the The surface quality of the billet is good, and the reduction of the grooved rolling roll is set to be small. Under such rolling conditions, when the grooved rolling rolls equipped on the finishing machine stand must open a gap, that is, when the pressing position must be changed to the outside, relative to the finishing machine stand, it is arranged on the tube blank. If the pressing position of the grooved rolling roll on the upstream machine stand on the upstream side of the conveying direction is not adjusted in any way, and the initial setting based on the pass schedule is still used, there will be a gap at the bottom of the groove. Empty rolling phenomenon occurs.

The so-called empty rolling phenomenon at the bottom of the groove refers to the thickness of the groove bottom of the tube blank on the entrance side of the finishing stand of the mandrel type seamless pipe rolling mill (the so-called groove bottom thickness of the tube blank on the entrance side of the finishing stand refers to The thickness of the flange of the rolling stand on the upstream side of the finishing stand, the so-called flange, for the two-roll mandrel mill, is the thickness of the groove bottom of the groove rolling roll. The part where the 90° intersects; for a mandrel mill with more than 3 rolls, it is the middle part of the bottom of the groove adjacent to the groove rolling roll), because it becomes smaller than the core on the finishing stand The gap between the rod and the grooved rolling roll is small, so there is a state that it cannot be rolled on the finishing stand of the mandrel mill.

The reason why the idle rolling phenomenon occurs at the bottom of the groove will be described below. The rolling of the plate, because its pressing direction is only one direction perpendicular to the plate, so if the gap between the rolling rolls on the upstream stand is set as the rolling roll on the downstream stand If the gap between them is larger than that, the plate will not be empty-rolled when it is pressed down by the rolling rolls installed on the downstream stand. In contrast, in the mandrel mill for rolling pipes, whether it is the above-mentioned 2-roll, 3-roll or 4-roll type, the position of the tube blank, that is, the hole, is pressed between adjacent stands. The position of the bottom of the groove of the groove of the groove is different in the circumferential direction of the tube blank. At the same time, not only the thickness of the part opposite to the bottom of the groove of the groove of the groove, but also the thickness of the groove of the groove of the groove that is not directly subjected to the downward pressure The thickness of the portion opposite to the flange portion of the rim will also be reduced to a certain extent. Since the portion opposite to the flange portion is not directly subjected to the downforce, it is difficult to control the amount of reduction in thickness, and the thickness of this portion is only an estimate. Therefore, if the thickness reduction of the portion facing the opening of the grooved rolling roll is greater than the estimated value, even if the gap between the grooved rolling rolls arranged on the upstream stand is set to the downstream stand Above the gap between the grooved rolling rolls on the upper stand, the thickness reduction of the grooved rolling rolls on the upstream stand is relatively large, and the grooved rolling rolls on the finishing stand When the bottom of the groove is rolled, its thickness may also be smaller than the gap between the mandrel rod and the grooved rolling roll. Therefore, empty rolling occurs at the bottom of the groove.

When the empty rolling phenomenon occurs at the bottom of the groove, the tube blank cannot be rolled to the desired thickness with high precision on the finishing stand. In other words, the more idle rolling occurs on the finishing stand, the thickness of the portion facing the flange portion of the grooved rolling roll disposed on the upstream stand will excessively decrease, so the thickness of the outlet side of the finishing stand The thickness of the blank tube becomes lower than the desired thickness. In addition, the original purpose of the finishing stand of the mandrel mill is to make the inner surface and the outer surface of the billet smooth by light rolling with a small reduction. However, when the idle rolling phenomenon occurs at the bottom of the groove, there will be a part that is not pressed at all, resulting in deterioration of the surface properties of the seamless pipe.

In this way, the present inventors have found that the cause of the inability to accurately roll the billet to the desired thickness and the deterioration of the surface properties of the billet is the empty rolling phenomenon at the bottom of the groove, and it is necessary not to cause the empty rolling phenomenon at the bottom of the groove. Methods for performing elongation rolling are discussed in depth. The results show that, during finish rolling, when the pressing position of the grooved rolling roll arranged on the finishing stand is changed outward, not only the grooved rolling roll, but also the pressing position of the finishing stand will be affected. In the same direction, the grooved rolling rolls arranged on the immediately adjacent upstream machine stand also make it move to the outside, so that the empty rolling phenomenon at the bottom of the groove can be prevented. The present invention is based on this knowledge.

That is, in the rolling control method of the mandrel mill according to the present invention, in each stand constituting the mandrel mill, when rolling the billet in the finishing stand, the Rolling in a mandrel mill in which the pressing position of the first grooved rolling roll arranged on the finishing stand changes outward from the pressing position initially set according to the rolling table The control method, wherein, when the tube blank is rolled on the immediately upstream stand which is the same as the finishing stand and the reduction direction, the reduction of the second groove rolling roll arranged on the upstream stand The position is also changed in the outward direction from the reduction position initially set according to the rolling table, similarly to the first grooved rolling roll.

According to the present invention, the tube blank is rolled on the immediately adjacent upstream stand which has the same pressing direction as the finishing stand, that is, on the upstream stand which is only 2 stands apart from the finishing stand At the same time, the pressing position of the second grooved rolling roll arranged on the upstream machine stand is also changed to the outside like the first grooved rolling roll. Therefore, when the second groove rolling roll rolls the tube blank, the reduction amount of the bottom of the groove is reduced, thus, it is possible to prevent the upstream machine located at the upstream and only one stand away from the finishing stand. The thickness of the portion facing the flange portion of the grooved rolling roll on the seat is excessively reduced. Therefore, when rolling with the first grooved rolling rolls arranged on the finishing stand, empty rolling phenomenon will not occur at the bottom of the groove. Therefore, the blank tube can be accurately rolled to a desired thickness, and at the same time, the surface quality of the tube blank can be prevented from deteriorating.

In addition, in the present invention, "moving outward like the first grooved rolling roll" means that when the pressing position of the first grooved rolling roll is moved outward with respect to a part of the end portion of the billet, etc. For a part such as the end of the billet, the pressing position of the second grooved rolling roll is also changed to the outside. When the reduction position is changed outward, the reduction position of the second grooved rolling roll is also changed outward over the entire length of the blank tube. The expressions "moving outward similarly to the first pass roll" in this specification have the same meaning.

The present invention can be applied to a mandrel type seamless pipe rolling mill equipped with a pipe that can be rolled on the immediately upstream stand having the same pressing direction as the finishing stand. The position of the billet (front section, middle part or rear end) and the mechanism that changes the pressing position of the second groove rolling roll. However, among the mandrel mills, there are also mandrel mills that do not have such a mechanism on the stands other than the finishing stands. When such a mandrel-type seamless pipe rolling mill is used, instead of changing the pressing position corresponding to the position of the billet, the pressing position of the second pass rolling roll is changed outward before rolling the billet. Can.

That is, in the rolling control method of the mandrel mill according to the present invention, in each stand constituting the mandrel mill, when the billet is rolled on the finishing stand, the Rolling control method of a mandrel mill in which the pressing position of the first pass rolling roll provided on the finishing stand is changed outward, wherein the finishing machine is controlled in advance before rolling the tube. The seats have the same pressing direction, and the pressing positions of the second grooved rolling rolls arranged on the immediately upstream stand are changed to the outside.

In addition, in the rolling control method of the mandrel mill of the present invention, in each stand constituting the mandrel mill, when rolling the billet on the finishing stand A rolling control method of a mandrel mill in which the pressing position of the first pass roll arranged on the finishing stand changes outward, wherein, on the exit side of the finishing stand, a Set up a thickness gauge to measure the thickness of the tube blank along the pressing direction of each machine base, and compare the preset target thickness of the tube blank with the actual thickness measured by the thickness gauge on the finishing machine base. When the thickness is smaller than the target thickness, the change of the reduction position of the first-groove rolling roll is suspended for the billet to be rolled next time.

According to the present invention, a thickness gauge is arranged on the outlet side of the finish machine base, and the target thickness of the tube blank preset on the finish machine base is compared with the actual thickness of the tube blank measured by the thickness gauge. As a result, when the actual thickness If the thickness is smaller than the target thickness, empty rolling may occur at the groove bottom. Therefore, in this case, if it is judged that idle rolling occurs at the bottom of the groove, the variation of the reduction position of the first groove rolling roll for the next rolling of the billet is suspended. In this way, for the tube blank to be rolled next time, because the outward movement of the first grooved rolling roll is interrupted, the reduction of the first grooved rolling roll will not decrease, which can prevent the The empty rolling phenomenon occurs at the bottom of the groove.

Said in the present invention " interrupt the change of the reduction position of the first groove rolling roll ", comprise following two examples (i) and (ii):

(i) Basically, the outward variation of the first pass roll is a preset value that has nothing to do with the actual thickness value measured by the thickness gauge. In this case, the so-called "stopping the change of the rolling position" means: (a) when rolling a part (end portion, etc.) of the billet, the rolling position of the first groove rolling roll is also maintained; At the same position as when rolling the remaining part (central part, etc.) same location.

(ii) The amount of outward fluctuation of the first grooved rolling roll is preset as mentioned above, but the set value can be changed according to the actual thickness measured by the thickness gauge (for example, when the actual thickness is larger than the target thickness, Just reduce the amount of variation according to the amount of the difference), so that it is suitable for the tube blank rolled next time. The term "interrupting the change of the pressing position" in this example means that the set value is not changed according to the actual thickness measured by the thickness gauge, and the tube blank to be rolled next time is also changed according to the current setting. The value makes the rolling roll of the first groove move outward.

In particular, if a configuration in which the set value of the outward fluctuation amount of the first pass rolling roll is changed correspondingly based on the actual thickness measured by the thickness gauge is adopted, when the empty rolling phenomenon occurs at the bottom of the groove, the actual thickness is smaller than the target thickness , it may lead to unlimited movement of the pass rolling rolls to the outside. However, according to item (ii) of the present invention, the movement of the first grooved rolling roll to the outside is interrupted (interruption of the change of the set value corresponding to the actual thickness measured by the thickness gauge), so this problem can be solved. .

In the present invention, by comparing the target thickness with the actual thickness, it is determined whether the empty rolling phenomenon occurs at the bottom of the groove. Compare the actual thickness variation of the measured tube blank along the direction of variation of the first-groove rolling roll, if the actual thickness variation is smaller than the variation of the first-groove rolling roll’s pressing position , it is judged that the rolling phenomenon occurred at the bottom of the groove. The variation of the actual thickness is smaller than the variation of the pressing position of the rolling roll of the first pass, and the bottom of the groove of the rolling roll of the first pass after the change of the pressing position cannot touch the outer peripheral surface of the tube blank, and it is possible to The idle rolling phenomenon occurred at the groove bottom, and thus, it can be judged that the idle rolling phenomenon occurred at the groove bottom.

In the rolling control method of the mandrel mill of the present invention, in each stand constituting the mandrel mill, when rolling the billet on the finishing stand, the The rolling control method of the mandrel mill in which the pressing position of the first groove rolling roll on the finishing stand changes outward, wherein a measuring tube blank is arranged on the exit side of the finishing stand The thickness meter compares the variation of the rolling position of the first pass rolling roll with the change of the actual thickness of the tube blank measured by the thickness meter along the direction of the change of the first pass rolling roll, if If this amount of change is smaller than the amount of variation in the reduction direction of the first grooved rolling roll, the variation of the reduction position of the first grooved rolling roll is suspended for the next rolled tube.

Furthermore, instead of judging whether empty rolling occurs at the bottom of the groove based on the comparison between the target thickness and the actual thickness, the sum of the position and the upper position after the change of the first pass rolling roll of the tube billet rolled this time is calculated. The position difference of the first pass rolling roll of the tube billet rolled for the second time is changed, and at the same time, the position measured by the thickness meter along the moving direction of the first pass roll roll of the rolled tube blank this time is also calculated. The actual thickness, and the difference between the actual thickness measured by the thickness gauge and the actual thickness of the last rolled tube along the rolling direction of the first pass roll, compare the calculated difference between these reduction positions and the actual thickness difference , if the calculated actual thickness difference is smaller than the calculated reduction position difference, it can also be determined that empty rolling has occurred at the groove bottom. In other words, when the calculated actual thickness difference is smaller than the calculated reduction position difference, for this rolling, the groove bottom of the first pass rolling roll after the reduction position has changed cannot touch the tube blank Therefore, it can be judged that empty rolling phenomenon occurs at the bottom of the groove.

In the rolling control method of the mandrel mill of the present invention, in each of the stands constituting the mandrel mill, when the tube blank is rolled on the finishing stand, the The rolling control method of the mandrel mill in which the pressing position of the first groove rolling roll on the finishing stand changes outward, wherein a measuring tube blank is arranged on the exit side of the finishing stand The thickness meter of the thickness is used to calculate the reduction position of the rolled tube blank after the change of the first pass roll and the press position of the tube blank rolled last time after the change of the first pass roll. At the same time, it also calculates the actual thickness of the tube billet rolled along the first pass rolling direction measured by the thickness gauge, and the actual thickness of the tube billet rolled along the first groove measured by the thickness gauge. The difference between the actual thickness of the grooved rolling roll in the direction of change, compare the calculated difference between these reduction positions and the difference between the actual thickness, if the difference between the calculated actual thickness is smaller than the difference between the calculated reduction positions , just interrupt the variation of the rolling position of the first groove rolling roll for the tube blank rolled next time.

In addition, in the rolling control method of the mandrel mill of the present invention, in each stand constituting the mandrel mill, when the billet is rolled on the finishing stand, the matching A rolling control method of a mandrel mill in which the pressing position of the first grooved rolling roll provided on the finishing stand changes outward, wherein a measuring device is installed on the exit side of the finishing stand. The thickness gauge of the tube blank thickness along the pressing direction of each machine base compares the target thickness of the tube blank preset on the finishing machine base with the actual thickness measured by the thickness gauge, and when the actual thickness is smaller than the target thickness In the case of the case, on the upstream stand which is located in the position next to the finishing stand and has the same reduction direction as the thickness measurement direction in which the actual thickness can obtain a small result, the tube blank for the next rolling When rolling, either the pressing position of the second grooved rolling roll arranged on the upstream machine stand is also changed outward like the first grooved rolling roll, or the rolling position of the second grooved rolling roller arranged next to the finishing process is changed. The reduction position of the second groove rolling roll on the position of the stand and on the upstream stand having the same reduction direction as the thickness measurement direction in which the actual thickness can obtain a small result, in the next rolling The prepared tube blank is moved outward in advance before rolling.

According to the present invention, a thickness gauge is arranged on the exit side of the finish machine base, and the target thickness of the tube blank preset on the finish machine base is compared with the actual thickness of the tube blank measured by the thickness gauge. As a result, when the actual thickness is smaller than the target thickness, there is a possibility that empty rolling phenomenon occurs at the bottom of the groove in the thickness measurement direction, and thus it is judged that empty rolling phenomenon occurs at the bottom of the groove. (iii) On an upstream stand located immediately adjacent to the finishing stand and having the same pressing direction as the thickness measurement direction in which the actual thickness can obtain a small result, the next rolled tube blank is During rolling, either the pressing position of the second grooved rolling roll arranged on the upstream stand is also moved outward, or (iv) the rolling roller arranged at a position adjacent to the finishing stand and The reduction position of the second groove rolling roll on the upstream machine stand with the same reduction direction as the thickness measurement direction where the actual thickness can obtain the smallest result is pre-rolled before rolling the tube blank for the next rolling. Move outward.

Therefore, regardless of any of the above items (iii) or (iv), for the tube rolled next time, it is possible to reduce the pressure in the same direction as the direction in which it is judged that the empty rolling phenomenon has occurred at the bottom of the groove. The amount of reduction on the upstream stand in the downward direction can increase the thickness of the billet in the reduction direction, so it is possible to prevent empty rolling at the bottom of the groove when rolling on the finishing stand. In addition, the structure of item (iii) can be well applied to the position (front end, center or rear end) corresponding to the tube blank being rolled in the upstream stand, and can make the reduction of the second groove rolling roll A mandrel mill with a variable position. Also, the configuration in item (iv) can be suitably applied to a mandrel mill that does not have a mechanism for changing the pressing positions of stands other than the finishing stand.

In this way, the present invention judges whether empty rolling occurs at the bottom of the groove by comparing the target thickness with the actual thickness. Instead of this method, the variation of the rolling position of the first pass rolling roll is compared with the value of the tube billet measured by the thickness gauge. If the actual thickness variation along the movement direction of the first grooved rolling roll is smaller than the variation in the pressing position of the first grooved rolling roll, it can also be determined that the empty rolling phenomenon.

In the rolling control method of the mandrel mill of the present invention, in each stand constituting the mandrel mill, when rolling the billet on the finishing stand, the The rolling control method of the mandrel mill in which the pressing position of the first groove rolling roll on the finishing stand changes outward, wherein a measuring tube blank is arranged on the exit side of the finishing stand The thickness meter compares the variation of the rolling position of the first pass rolling roll with the change of the actual thickness of the tube blank measured by the thickness meter along the direction of the change of the first pass rolling roll, if If the amount of change is smaller than the amount of variation in the reduction direction of the first grooved rolling roll, on the upstream stand that is located next to the finishing stand and has the same reduction direction as the thickness measurement direction , when rolling the tube blank for next rolling, or the pressing position of the second grooved rolling roll arranged on the upstream stand is also moved outward like the first grooved rolling roll, Or make the pressing position of the second groove rolling roll arranged on the position close to the finishing stand and on the upstream stand having the same pressing direction as the thickness measuring direction, in the opposite next time The rolled tube is moved outward in advance before rolling.

Furthermore, instead of judging whether empty rolling occurs at the bottom of the groove based on the comparison between the target thickness and the actual thickness, the position sum of the changed position of the first-gauge rolling roll of the billet rolled this time and that of the last time is calculated. The position difference of the rolled tube blank after the change of the first pass roll is also calculated, and the actual thickness of the rolled tube along the first pass roll change direction measured by the thickness meter is also calculated , and the difference between the actual thickness measured by the thickness gauge and the actual thickness of the last rolled tube along the rolling direction of the rolling roll of the first pass, compare the calculated difference between these reduction positions and the actual thickness difference, if If the calculated actual thickness difference is smaller than the calculated reduction position difference, it can be determined that idle rolling has occurred at the groove bottom.

In the rolling control method of the mandrel mill of the present invention, in each of the stands constituting the mandrel mill, when the tube blank is rolled on the finishing stand, the The rolling control method of the mandrel mill in which the pressing position of the first groove rolling roll on the finishing stand changes outward, wherein a measuring tube blank is arranged on the exit side of the finishing stand The thickness meter of the thickness is used to calculate the reduction position of the rolled tube blank after the change of the first pass roll and the press position of the tube blank rolled last time after the change of the first pass roll. At the same time, it also calculates the actual thickness of the tube billet rolled along the first pass rolling direction measured by the thickness gauge, and the actual thickness of the tube billet rolled along the first groove measured by the thickness gauge. The difference in the actual thickness of the grooved rolling rolls in the direction of change, compare the difference between the calculated reduction position and the difference in the actual thickness, if the difference in the calculated actual thickness is smaller than the difference in the calculated reduction position, then On the upstream stand that is located close to the finishing stand and has the same pressing direction as the thickness measurement direction, when rolling the tube blank to be rolled next time, or it is arranged on the upstream stand The pressing position of the second grooved rolling roll on the top is also moved outward like the first grooved rolling roll, or it is arranged at a position close to the finishing stand and has the same thickness measurement The reduction position of the second grooved rolling roll on the upstream machine stand in the same direction as the reduction direction is changed to the outside in advance before the tube blank to be rolled next time is rolled.

From another point of view, the rolling control device of the mandrel mill according to the present invention includes: among the stands constituting the mandrel mill, arranged on the finishing stand, The first reduction position adjustment device for adjusting the reduction position of the groove rolling roll; it has the same reduction direction as the finishing stand, and is arranged on the nearby upstream stand, for the groove rolling The second reduction position adjustment device that adjusts the reduction position of the roll; the calculation control that issues the instruction of the reduction position adjustment amount of the groove rolling roll to the first reduction position adjustment device and the second reduction position adjustment device The device, wherein the calculation control device sends an instruction of the adjustment amount of the rolling position of the rolling roll with a predetermined groove to the first pressing position adjusting device and the second pressing position adjusting device according to the current position of the tube blank, so as to implement the first invention Or the rolling control method of the present invention described in the second claim.

The rolling control device of the mandrel mill according to the present invention includes: in each stand constituting the mandrel mill, a device for adjusting the rolling pass is arranged on the finishing stand. A reduction position adjustment device for the reduction position of the roll; a calculation control device for sending an indication of the reduction position adjustment amount of the groove rolling roll to the reduction position adjustment device, wherein the calculation control device is connected to the On the exit side of the finishing machine base, on the thickness gauge for measuring the thickness of the tube blank along the pressing direction of each machine base, according to the output of the thickness gauge, the pressing position is interrupted by sending the pressing position adjustment device Instructions for adjustment implement the rolling control method described in any one of the third invention to the fifth invention.

The rolling control device of the mandrel mill according to the present invention includes: in each stand constituting the mandrel mill, a device for adjusting the rolling pass is arranged on the finishing stand. The first reduction position adjustment device for the reduction position of the roll; it has the same reduction direction as the finishing stand, and is arranged on the nearby upstream stand to adjust the reduction position of the groove rolling roll The second pressing position adjusting device; the calculation control device for issuing adjustment amount instructions to the first pressing position adjusting device and the second pressing position adjusting device, wherein the calculation control device is connected to the finishing machine On the outlet side of the seat, on the thickness gauge for measuring the thickness of the tube blank along the pressing direction of each machine base, according to the output of the thickness gauge and the current position of the tube blank, send a signal to the second pressing position adjustment device An instruction of the adjustment amount is prescribed, and the rolling control method of the present invention according to any one of the sixth invention to the eighth invention is implemented.

From another point of view, the control program of the present invention is used to operate a calculation control device that is connected to each stand constituting a mandrel mill and arranged on a finishing stand. , the first reduction position adjusting device for adjusting the reduction position of the rolling roll of the pass type, and the counter-pass type provided on the nearby upstream stand having the same reduction direction as the finishing stand The second reduction position adjusting device for adjusting the reduction position of the rolling rolls sends instructions to the first reduction position adjustment device and the second reduction position adjustment device of the adjustment amount of the reduction position of the grooved rolling rolls, Among them, according to the current position of the pipe blank, by issuing a predetermined adjustment amount of the reduction position to the first reduction position adjustment device and the second reduction position adjustment device, the calculation control device is operated, and the first invention or the second invention is implemented. The rolling control method of the present invention described in the invention.

In addition, the control program of the present invention is used to operate the calculation control device. The calculation control device is connected to each stand constituting the mandrel-type seamless pipe rolling mill, and is arranged on the finishing stand for adjusting the pass type. The pressing position adjustment device for the pressing position of the rolling roll, and the thickness gauge installed on the exit side of the finishing stand to measure the thickness of the tube blank along the pressing direction of each stand, The lower position adjustment device issues an instruction of the adjustment amount of the reduction position of the grooved rolling roll. According to the output of the thickness gauge, the calculation control device is operated by issuing an instruction to stop the adjustment of the reduction position according to the output of the thickness gauge, and the third step is implemented. The rolling control method of the present invention according to any one of the invention to the fifth invention.

In addition, the control program of the present invention is used to operate a calculation control device which is connected to each stand constituting the mandrel mill and connected to the finishing stand provided on the finishing stand. The first reduction position adjustment device for adjusting the reduction position of the groove rolling roll, and the first reduction position adjustment device arranged on the nearby upstream stand having the same reduction direction as the finishing stand. The second reduction position adjustment device for adjusting the reduction position of the roll, and the thickness gauge installed on the exit side of the finishing stand to measure the thickness of the shell along the reduction direction of each stand , sending an instruction of the adjustment amount to the first pressing position adjusting device and the second pressing position adjusting device, wherein, according to the output of the thickness gauge and the current position of the tube blank, the specified adjustment amount is sent to the second pressing position adjusting device instruction to operate the arithmetic control device to implement the rolling control method of the present invention described in any one of the sixth invention to the eighth invention.

From another point of view, the seamless pipe of the present invention is produced by a mandrel mill using the rolling control method of the present invention according to any one of the first to eighth inventions.

According to the present invention, when a seamless pipe is manufactured using a mandrel mill, a part or all of the longitudinal direction of the blank such as the end can be accurately rolled to a desired thickness without compromising the surface texture of the blank. Deterioration occurs.

Specifically, according to the present invention, when the tube blank is rolled on the adjacent upstream stand having the same pressing direction as the finishing stand, since the second groove rolling mill installed on the upstream stand The rolling position of the roller changes to the outside, and when the tube blank is rolled at the second groove rolling roller, the reduction amount at the bottom of the groove is reduced, thereby preventing the groove from collapsing with the groove arranged on the stand below. The thickness of the portion facing the flange portion of the rolling roll is excessively thinned. Therefore, when rolling with the first groove rolling roll arranged on the finishing machine stand, the empty rolling phenomenon at the bottom of the groove can be eliminated, and the tube blank can be accurately rolled to the desired thickness, and at the same time It can prevent the deterioration of the surface properties of the billet.

Description of drawings

Fig. 1 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a first embodiment.

Fig. 2 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a second embodiment.

3 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a third embodiment.

Fig. 4 is a schematic view showing an example of a reduction position variation pattern of a grooved rolling roll arranged on a finishing stand.

Symbol Description

1 rolling control device

11 The first pressing position adjustment device

12 second pressing position adjustment device

13 calculation control device

M mandrel seamless pipe mill

S tube blank

131 First pressing position setting unit

132 Second pressing position setting unit

Detailed ways

The best mode for carrying out the present invention will be described below with reference to the attached drawings. In addition, in the description of the present embodiment, when rolling the end portion of the blank pipe on the finishing stand of the twin-roll type mandrel mill, the finishing stand arranged on the An example in which the pressing position of the grooved rolling roll is shifted outward is taken as an example. However, this is only an example of the present invention, and the present invention is also applicable to a form in which the pressing position of the grooved rolling rolls arranged on the finishing stand is changed outwards over the entire length of the billet, or a double-roller type is used. Other forms of mandrel mills.

<First Embodiment>

Fig. 1 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a first embodiment.

As shown in FIG. 1 , the rolling control device 1 of this embodiment includes a first reduction position adjustment device 11 , a second reduction position adjustment device 12 , and a calculation control device 13 .

The first reduction position adjusting device 11 is used to adjust the reduction position of the grooved rolling roll arranged on the finishing stand #i among the stands constituting the mandrel mill M. cylinder etc. The second pressing position adjustment device 12 is provided on the immediately upstream stand whose pressing direction is the same as that of the finishing stand #i, that is, it is located upstream of the finishing stand #i at an interval of only 2 It is composed of a cylinder and the like to adjust the pressing position of the grooved rolling roll on the stand #(i-2) at the first stand. Furthermore, the calculus control device 13 is connected to the first pressing position adjusting device 11 and the second pressing position adjusting device 12, and according to the current position of the end of the tube blank S, the first pressing position adjusting device 11 and the second pressing position adjusting device 12 are adjusted. The second pressing position adjustment device 12 issues an instruction of the adjustment amount of the pressing position.

In addition, in this embodiment, both the first reduction position adjusting device 11 and the second reduction position adjustment device 12 have positions that can be adjusted according to the position (front end, central part, or rear end) of one billet S during rolling. end) to change the pressing position of the grooved roll accordingly.

The arithmetic control device 13 is constituted by a computer having hardware such as a CPU, a memory, an external storage device, and an external input panel. And, by appropriately driving these hardware according to the built-in control program, the functions of the first depressing position setting unit 131 and the second depressing position setting unit 132 are exhibited.

To the first pressing position setting unit 131 , for example, an end detection signal displayed when an end of the blank pipe S is detected by a detection sensor (not shown) provided on the entrance side of the mandrel mill M is input. Further, the distance between the detection sensor and stand #i, the conveying speed of the billet S, and the mandrel rolling mill are input to the first pressing position setting unit 131 from, for example, the aforementioned process control computer (not shown). The elongation of the tube blank S in M, etc. The first pressing position setting unit 131 calculates the current position of the end portion of the blank pipe S based on the input signal and data. Specifically, the timing at which the end portion (front end and rear end) of the blank pipe S reaches the stand #i and the timing at which it is pulled out from the stand are calculated.

The first reduction position setting unit 131 sets the adjustment amount of the reduction position of the first grooved rolling roll arranged on the finishing stand #i based on the calculated timing, and sets the set reduction position The position adjustment amount is sent to the first pressing position adjustment device 11 . Specifically, in the first reduction position setting unit 131, the reduction positions A of the first grooved rolling rolls when the end portion of the shell S is rolled on the finishing stand #i are respectively stored. , and the pressing position B of the first grooved rolling roll when rolling the central part of the billet S. The first reduction position setting unit 131 sets the first groove rolling roll from the reduction position B to the reduction position A until the front end of the shell S reaches the finishing stand #i. The deviation (A-B) is set as a depression position adjustment amount and the adjustment amount is sent to the first depression position adjustment device 11 .

Similarly, the first pressing position setting unit 131 moves the first grooved rolling roll from the pressing position from A to the pressing For position B, the deviation (B-A) is set as the pressing position adjustment amount and sent to the first pressing position adjusting device 11 . Then, when the rear end portion of the blank pipe S reaches the finishing stand #i, the deviation (A-B) is set as the pressing position adjustment amount and sent to the first pressing position adjusting device 11 .

Furthermore, from the timing when the rear end portion of the steel pipe S is pulled out from the finishing stand #i to the timing when the front end portion of the next rolling pipe S reaches the finishing stand #i, the first The grooved rolling roll moves from the reduction position A to the reduction position B, and the deviation (B-A) is set as the reduction position adjustment amount, and is sent to the first reduction position adjustment device 11 .

Therefore, in this embodiment, when the end portion of the shell S is rolled by the finishing stand #i, the pressure of the first grooved rolling roll arranged on the finishing stand #i can be made The lower position moves outward, that is, the lower position B. In addition, the values of the reduction positions A and B vary depending on the size, thickness, and material of the rolled shell S, so the first reduction position adjustment device 11 stores values corresponding to various sizes, thicknesses, and materials. A plurality of pressing positions A, B, for example, according to the size, thickness and material of the tube S input into the process control computer, the appropriate pressing positions A, B can be selected.

Similar to the first pressing position setting unit 131, detection signals etc. are input from the outside to the second pressing position setting unit 132, and it is calculated that the ends (front end and rear end) of the shell S reach and pull out upstream. Timing for seat #(i-2).

In addition, similar to the first reduction position setting unit 131, the second reduction position setting unit 132 sets the second pass rolling position arranged on the upstream stand #(i-2) based on the calculated timing. The adjustment amount of the pressing position of the roller, and send the set adjustment amount to the second pressing position adjustment device 12 . In addition, the adjustment amount of the reduction position sent to the second reduction position adjustment device 12 is the same as when the end of the billet S is rolled on the upstream machine stand #(i-2), and the amount of the adjustment of the position of the second reduction is configured on the upstream machine stand # (i-2). The amount corresponding to the amount of movement of the reduction position of the second grooved rolling roll on the seat #(i-2) to the outside is not necessarily set to be the same as the pressure sent to the first reduction position adjustment device 1. The same value as the lower position adjustment amount. For example, it may be set as a value multiplied by a predetermined coefficient (for example, 0.8) greater than 0 and less than 1.

According to the rolling control device 1 of the present embodiment, not only the finishing stand #i but also the upstream stand #(i-2) is installed on the upstream stand #(i-2) when rolling the end of the billet S The pressing position of the first grooved rolling roll on the stand #(i-2) changes to the outside. Therefore, when the billet S is rolled with the second grooved rolling roll, the reduction amount at the bottom of the groove decreases, and the flange portion of the grooved rolling roll arranged on the next stand #(i-1) The situation where the thickness of the opposite part is excessively reduced is eliminated. Therefore, when rolling is performed with the first grooved rolling rolls arranged on the finishing stand #i, it is possible to prevent idle rolling from occurring at the bottom of the groove. Thereby, the end portion of the raw pipe S can be accurately rolled to a desired thickness, while preventing the surface quality of the raw pipe S from deteriorating.

In addition, in this embodiment, it is assumed that the first reduction position adjusting device 11 is not limited to the case where the second reduction position adjustment device 12 also has a mechanism for changing the reduction position during rolling of one shell S. example. However, there is also a mandrel mill M without such a mechanism other than the finishing stand #i. Therefore, for this mandrel type seamless pipe rolling mill, instead of changing the pressing position according to the position of the billet S, the stand #(i -2) It is only necessary to change the pressing position of the grooved rolling roll to the outside.

In this embodiment, the second pressing position setting unit 132 adjusts the amount of pressing position, that is, the pre-stored pressing position, according to the timing of inputting the detection signal of the front end of the billet S from the outside, for example, to make the pressing position A necessary adjustment amount for the outward change is set, and the set pressing position adjustment amount is sent to the second pressing position adjusting device 12 . The second reduction position adjusting device 12 moves the reduction position of the second grooved rolling roll to the outside according to the transmitted reduction position adjustment amount. The changed pressing position is maintained at the same value through the rolling process of the billet S.

<Second Embodiment>

Fig. 2 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a second embodiment.

As shown in FIG. 2 , the rolling control device 2 of the present embodiment includes a reduction position adjustment device 21 and a calculation control device 22 .

The pressing position adjusting device 21 is composed of an air cylinder for adjusting the pressing position of the grooved rolling roll, which is arranged on the finishing stand #i among the stands constituting the mandrel mill M. etc., and has a mechanism capable of changing the pressing position of the grooved rolling rolls according to its position (front end, center, or rear end) during rolling one billet S.

Similar to the first embodiment, the arithmetic control device 22 is constituted by a computer having hardware such as a CPU, but is arranged on the exit side of the finishing stand #i (in this embodiment, a mandrel mill On the exit side of the tube), it is connected to the device that measures the thickness of the tube blank S along the pressing direction of each stand (for example, when the mandrel mill M is a twin-roll type, it is the thickness in 4 directions) The thickness gauge 1 is different from the first embodiment in this point.

The calculation control device 22 drives the hardware appropriately according to the built-in control program, thereby playing the role of the reduction position setting part 221 and the empty rolling determination part 222, and setting the reduction position to the reduction position on the basis of the output of the thickness gauge I. The part 221 issues a command to interrupt the adjustment of the pressing position. More specific description will be given below.

Similar to the first pressing position setting unit 131 described in the first embodiment, the end detection signal of the raw pipe S and the like are input to the pressing position setting unit 221, and it is calculated that the end of the raw pipe S reaches the finishing stand. Timing of #i and timing of pulling out. In addition, similarly to the first embodiment, in the finishing stand #i, the reduction positions of the grooved rolling rolls when the end portion and the center portion of the billet S are rolled respectively are stored in the reduction position settings. Section 221. The reduction position setting unit 221 sets the adjustment amount of the reduction position of the grooved roll arranged on the finishing stand #i based on the calculated timing and the stored reduction position of the grooved roll. The set pressing position adjustment amount is sent to the pressing position adjusting device 21 . Thereby, when rolling the end portion of the blank pipe S in the finishing stand #i, the pressing position of the grooved rolling rolls arranged on the finishing stand #i can be moved outward only by the corresponding pressure. The amount of down position adjustment.

The output of the thickness gauge I (the actual thickness of the end portion of the steel pipe S) is input to the dummy rolling determination unit 222 . In addition, the target thickness of the end part of the shell S is stored in the dummy rolling determination part 222 in advance. The empty rolling determination unit 222 compares the target thickness of the blank tube S with the actual thickness, and when the actual thickness is smaller than the target thickness, that is, in the actual thickness obtained by measuring the rolling direction of the finishing stand #i, at least any When the actual thickness of one was smaller than the target thickness, it was judged that the idle rolling phenomenon occurred at the groove bottom, and in other cases, it was judged that the idle rolling phenomenon did not occur. In addition, since the target thickness value of the end portion of the steel pipe S is different in accordance with the size of the steel pipe S to be rolled, the target thickness of the center portion, and the material, etc., the first reduction position adjustment device 11 stores the A plurality of target thicknesses corresponding to various sizes, thicknesses of the central portion, materials, etc. can be appropriately selected based on, for example, the size of the blank tube S, the thickness of the central portion, and materials input from a host process control computer.

When it is judged that idle rolling has occurred at the bottom of the groove in the idle rolling judging section 222, the pressing position setting section 221 sends an interruption to the rolling blank S to be rolled next time to change the pressing position of the rolling roll. instructions. That is, when rolling the end portion of the material pipe S, an instruction to maintain the same reduction position as when rolling the center portion of the material pipe S is issued to the reduction position adjusting device 21 . Specifically, the reduction position adjustment amount at the time of rolling the end portion of the steel pipe S is set to 0 and sent to the reduction position adjustment device 21 .

On the other hand, when it is judged in the dummy rolling judging section 222 that the dummy rolling phenomenon does not occur at the bottom of the groove, the billet S to be rolled next time is also rolled according to the pre-stored schedule for rolling the billet S separately. The reduction positions of the grooved rolling rolls at the end and the center are set and the reduction position adjustment amount is sent to the reduction position adjustment device 21 .

According to the rolling control device 2 of this embodiment, for the billet S to be rolled next time, since the movement of the grooved rolling rolls to the outside is interrupted, the reduction amount of the grooved rolling rolls will not decrease, and it can Prevents empty rolling at the bottom of the groove in finishing stand #i. Thereby, the end part of the raw pipe S can be rolled to a desired thickness with high precision, and deterioration of the surface quality of the raw pipe S can be prevented.

In addition, in the above description, an example of the following form was given: when no empty rolling phenomenon occurs at the bottom of the groove, regardless of the actual thickness of the end of the tube S measured by the thickness gauge 1, it will be compared to the bottom The amount of variation toward the outside of the grooved rolling rolls of the next billet S is used as a value to realize the setting, that is, when it is judged that the dummy rolling phenomenon does not occur at the bottom of the groove in the dummy rolling judging section 222, for the next time For the billet S to be rolled, the reduction position adjustment amount is also set according to the reduction position of the grooved rolling rolls when rolling the end part and the center part of the pre-stored billet S respectively, and this is sent to the reduction position Adjustment device 21.

However, the present invention is not limited to this form. For example, when there is no empty rolling phenomenon at the bottom of the groove, the amount of variation of the grooved rolling rolls to the outside relative to the next tube blank S is carried out corresponding to the actual thickness of the end of the tube blank S measured by the thickness gauge 1. To change, more specifically, for example, when the actual thickness is greater than the target thickness, the rolling position of the grooved rolling rolls when rolling the end of the billet S can be changed only to the inside of the difference between the actual thickness and the target thickness. and stored, for the next rolled tube S, according to the pre-stored pressing position when rolling the central part of the tube S and the changed stored position when rolling the end of the tube S The depressing position setting depressing position adjustment amount is sent to the depressing position adjusting device 21 . At this time, when it is determined that empty rolling has occurred at the bottom of the groove, the change of the set value corresponding to the actual thickness measured by the thickness gauge I is interrupted, and the set value of this time can also be applied to the tube blank S to be rolled next time . Therefore, it is possible to prevent unlimited movement of the grooved rolling rolls to the outside.

In addition, in this embodiment, an example is given in which the target thickness of the blank pipe S in the dummy rolling determination part 222 is compared with the actual thickness, and whether the dummy rolling phenomenon occurs at the bottom of the groove is determined based on the size. However, the method of judging whether the dummy rolling phenomenon occurs at the bottom of the groove in the dummy rolling determination part 222 is not limited thereto, for example, it may also be adopted by comparing the fluctuation amount of the reduction position of the grooved rolling roll with the thickness gauge. I measure the variation of the actual thickness along the fluctuating direction of the grooved rolling roll, if the variation of the actual thickness is smaller than the variation of the pressing position of the grooved rolling roll, it is determined that a fault has occurred at the bottom of the groove. Method for empty rolling phenomenon.

In this case, first, the empty rolling determination unit 222 refers to the adjustment amount of the reduction position set by the reduction position setting unit 221, that is, when the end portion of the billet S is rolled, the grooved rolling roll The amount of variation of the depressing position to the outside. Comparing the adjustment amount of the reference reduction position with the change amount of the actual thickness calculated from the actual thickness of the ends and the center of the shell S input by the thickness gauge I (the actual thickness along the fluctuating direction of the grooved rolling roll) (The difference between the actual thickness of the end and the actual thickness of the center). If this amount of change is smaller than the reference reduction position adjustment amount, it is determined that idle rolling has occurred at the groove bottom. In addition, instead of comparing the change amount with the reference depressing position adjustment amount, the value obtained by multiplying the change amount or the depressing position adjustment amount by a predetermined coefficient (for example: 0.5, etc.) greater than 0 and less than 1 may be increased. For comparison, if the amount of change is still small at this time, it can be judged that empty rolling has occurred at the bottom of the groove.

Furthermore, as another method for the dummy rolling judging unit 222 to judge whether or not a dummy rolling phenomenon has occurred at the bottom of the groove, for example, calculate the reduction position of the grooved rolling rolls for the billet S rolled this time after the change. The difference between the rolling position of the rolling roll after the change of the first pass of the tube blank S rolled last time, and calculate the pass profile measured by the thickness gauge I for the tube blank S rolled this time The difference between the actual thickness of the changing direction of the rolling roll and the actual thickness of the tube blank rolled last time along the changing direction of the grooved rolling roll measured by the thickness gauge I, and compare the difference between the pressing position and the actual thickness. The difference in thickness, if the difference in actual thickness is smaller than the difference in the pressing position, it can also be determined that empty rolling has occurred at the bottom of the groove.

In this case, the empty rolling determination part 222 refers to the pass rolling position stored in the rolling position setting part 221 (including the case of storing after updating as described above) for the last rolled shell S. The depressing position after the change of the roll, that is, the depressing position when rolling the end of the tube blank S, is stored, and at the same time, it is stored or updated in the depressing position setting with reference to the tube blank S rolled this time. The reduction position of the grooved rolling roll in the fixed part 221 after the change, that is, the reduction position when rolling the end of the shell S, is calculated by subtracting the former from the latter to calculate the current rolling and the previous rolling position. The difference in rolling reduction position. In addition, the empty rolling determination unit 222 stores the actual thickness (the actual thickness after the fluctuation of the rolling roll along the groove) of the end portion of the last rolled shell S input by the thickness meter I, and calculates the actual thickness Subtract from the actual thickness of the end portion input by the thickness meter I (the actual thickness after the change along the groove rolling roll) for the tube blank S rolled this time, thereby calculating the current rolling and the last time The difference in actual thickness as rolled. The empty rolling determination unit 222 compares the difference between the reduction position and the actual thickness difference, and if the actual thickness difference is smaller than the reduction position difference, it is determined that the idle rolling phenomenon has occurred at the groove bottom. In addition, instead of comparing the difference between the pressed position and the actual thickness difference, the actual thickness difference or the pressed position difference is multiplied by a predetermined coefficient (for example: 0.5, etc.) greater than 0 and less than 1. If the actual thickness difference is still small at this time, it can be judged that empty rolling has occurred at the bottom of the groove.

<Third Embodiment>

Fig. 3 is a schematic block diagram showing a schematic configuration of a rolling control device for implementing a rolling control method for a mandrel mill according to a third embodiment.

As shown in FIG. 3 , the rolling control device 3 of the present embodiment includes a first reduction position adjustment device 31 , a second reduction position adjustment device 32 , and a calculation control device 33 .

The first reduction position adjusting device 31 controls the reduction position of the groove rolling roll arranged on the finishing stand #i among the stands constituting the twin-roll type mandrel mill M. Adjusted cylinder and other components. The second pressing position adjusting device 32 is composed of adjacent upstream stands in the same pressing direction as the finishing stand #i, that is, stands #( i-2) Consists of air cylinders and the like to adjust the pressing position of the grooved rolling rolls arranged on the top. The calculation control device 33 is connected to the first pressing position adjusting device 31 and the second pressing position adjusting device 32, and sends a predetermined pressing position to the first pressing position adjusting device 31 and the second pressing position adjusting device 32. Indication of adjustment amount. In addition, the first and second rolling position adjustment devices 31 and 32 of the present embodiment each have a function to adjust the position (front end, center, or rear end) of one billet S during rolling. A mechanism that changes the pressing position of the grooved rolling roll.

Similar to the first embodiment, the arithmetic control device 32 is constituted by a computer having hardware such as a CPU, but is disposed on the exit side of the finishing stand #i (in this embodiment, a mandrel mill On the exit side of the tube), it is connected to the device that measures the thickness of the tube blank S along the pressing direction of each stand (for example, when the mandrel mill M is a twin-roll type, it is the thickness in 4 directions) The thickness gauge 1 is different from the first embodiment in this point. The calculation control device 32 drives the hardware appropriately according to the built-in control program, plays the role of the first pressing position setting part 331 and the second pressing position setting part 332, based on the output of the thickness gauge I and the The current position of the end portion can be used to instruct the first depressing position adjusting device 31 and the second depressing position adjusting device 32 of a predetermined depressing position adjustment amount. More specific description will be given below.

Similar to the first reduction position setting unit 131 described in the first embodiment, the end portion detection signal of the raw material pipe S and the like are input to the first reduction setting unit 331, and the end portion (tip portion) of the raw material pipe S is calculated. and rear end) to the timing of finishing machine base #i and the timing of pulling out. In addition, similarly to the first embodiment, the first grooved rolling rolls (disposed on the finishing stand #i) when rolling the end portion and the central portion of the billet S respectively in the finishing stand #i The pressing positions of the first grooved rolling rolls above are stored in the first pressing position setting part 331 respectively. The first reduction position setting unit 331 sets the reduction position of the first grooved roll arranged on the finishing stand #i based on the calculated timing and the stored reduction position of the grooved roll. The adjustment amount is to send the set pressing position adjustment amount to the first pressing position adjusting device 31 . Thereby, when rolling the end portion of the blank pipe S in the finishing stand #i, the pressing position of the first grooved rolling roll arranged on the finishing stand #i can be made only to the outside. The amount of variation corresponds to the adjustment amount of the pressing position.

The output of the thickness gauge I is input to the first pressing position setting unit 331 . In addition, the target thickness of the end part of the blank pipe S is stored in the 1st pressing position setting part 331 in advance. The first pressing position setting unit 331 compares the target thickness of the blank tube S with the actual thickness, and when the actual thickness is smaller than the target thickness (that is, in the actual thickness measured in the pressing direction of the finishing stand #i, When at least any one of the actual thicknesses is smaller than the target thickness), it is judged that the empty rolling phenomenon has occurred at the bottom of the groove.

In addition, instead of the method of judging whether idle rolling occurs at the groove bottom by comparing the target thickness and the actual thickness, as described in the second embodiment, it is also possible to apply the method of determining whether idle rolling occurs at other groove bottoms. Measure to judge. If the first reduction position setting part 331 determines that empty rolling has occurred at the bottom of the groove, the second reduction position setting part 332 refers to the result, and as will be described later, for the next rolled tube S, In the upstream stand #(i-2) which is located in the vicinity of the finishing stand #i and which has the same pressing direction as the thickness measurement direction and which results in a small actual thickness, adjust the device to the second pressing position 32 issues an instruction of a predetermined pressing position adjustment amount.

In addition, the first reduction position setting unit 331 may change the outward variation of the first pass rolling roll for the next round of the billet S based on the actual thickness of the end portion of the billet S measured by the thickness gauge 1. quantity. More specifically, for example, when the actual thickness is greater than the target thickness, the pressing position of the first pass rolling roll when rolling the end portion of the billet S is updated and stored inward according to the difference. Furthermore, for the next rolling of the billet S, the pre-stored pressing position when rolling the central portion of the billet S and the updated stored pressing position when rolling the end of the billet S may be used. , set the pressing position adjustment amount, and send it to the pressing position adjusting device 31 .

Similar to the first pressing position setting unit 331, the end detection signal is input from the outside to the second pressing position setting unit 332, and it is calculated that the ends (front end and rear end) of the shell S reach the upstream stand. Timing of #(i-2) and timing of pulling out.

The second reduction position setting part 332 refers to the first reduction position setting part 331, and when the first reduction position setting part 331 judges that the idle rolling phenomenon occurs at the bottom of the groove, it sets the configuration according to the calculated timing. The reduction position adjustment amount of the second grooved rolling roll on the upstream stand #(i-2) sends the set reduction position adjustment amount to the second reduction position adjustment device 12 . In addition, the adjustment amount of the reduction position sent to the second reduction position adjustment device 12, that is, as the sum when rolling the end portion of the billet S in the upstream stand #(i-2), is configured to Various forms can be adopted for the amount corresponding to the amount of variation of the reduction position of the second grooved rolling roll on #(i-2) to the outside. For example, a value obtained by multiplying the difference between the target thickness calculated by the first pressing position adjusting device 12 and the actual thickness by a coefficient of about 0.8 to 1.2 can be used. Alternatively, a constant value (for example, 0.2 mm) is adopted until the difference between the target thickness and the actual thickness becomes equal to or less than a predetermined value (for example, 0.1 mm).

According to the rolling control device 3 of this embodiment, when it is judged that the idle rolling phenomenon occurs at the bottom of the groove due to the output of the thickness gauge I, not only the finishing stand #i but also the The reduction position of the second grooved rolling roll arranged on the upstream stand #(i-2) and having the same reduction direction as the direction in which the idle rolling phenomenon is judged to occur at the bottom of the groove is shifted outward . Therefore, the amount of reduction in the upstream stand #(i-2) is reduced, the thickness of the billet in the direction of reduction is increased, and it is possible to prevent empty rolling at the groove bottom during rolling with the finishing stand #i. Thereby, the end part of the raw pipe S can be rolled to a desired thickness with high precision, and the surface quality of the raw pipe S can be prevented from deteriorating.

In addition, in this embodiment, regardless of the first reduction position adjustment device 31 or the second reduction position adjustment device 32 , a case where the reduction position can be changed while rolling one shell S is taken as an example. However, except for the finishing stand #i, for a mandrel mill that does not have such a device, instead of changing the pressing position according to the position of the billet S, the upstream The pressing position of the second grooved rolling roll of stand #(i-2) may be changed outward.

Example 1

Hereinafter, the characteristics of the present invention will be further described by citing examples and comparative examples.

The rolling control method of the present invention is applicable to a two-roller mandrel type seamless pipe rolling mill consisting of 6 stands (finishing stands are #5 and #6 stands), and a rolling test was carried out under the following conditions .

(1) Dimensions of the tube blank at the entrance side of the mandrel type seamless tube mill: outer diameter 190mm, thickness 16mm, length 4600mm

(2) Dimensions of the tube blank at the exit side of the mandrel type seamless tube mill: outer diameter 168mm, thickness 5mm, length 1500mm

(3) Mandrel Rod Outer Diameter: 158mm

(4) The target thickness (thickness of groove bottom) at the exit side of each stand initially set according to the rolling table

#1 base: 10mm #2 base: 9mm #3 base: 6mm

#4 base: 5.5mm #5 base: 5mm #6 base: 5mm

<Example 1-1>

In #5 stand and #6 stand, when rolling the end portion of the blank pipe, the pressing position of the grooved rolling roll is changed outward in the pattern shown in FIG. 4 . Also in #3 stand and #4 stand, rolling was performed after changing the pressing position of the grooved rolling roll to the outside with the same pattern. In addition, in #1 stand and #2 stand, rolling was carried out according to the rolling position set initially.

<Example 1-2>

In #5 stands and #6 stands, rolling was performed by changing the pressing positions of the grooved rolling rolls outward in the pattern shown in FIG. 4 as in Example 1-1. In #3 stand and #4 stand, rolling was carried out after reducing the variation amount of the pattern shown in FIG. 4 by 0.8 times (ie, maximum 0.4 mm). In addition, in #1 stand and #2 stand, rolling was carried out according to the rolling position set initially.

<Example 1-3>

In #5 stands and #6 stands, rolling was performed by changing the pressing positions of the grooved rolling rolls outward in the pattern shown in FIG. 4 as in Example 1-1. In #3 stand and #4 stand, in order to make the target thickness respectively 6.5mm (#3 stand) and 6mm (#4 stand) before the rolling of the tube blank, the groove rolling rolls Rolling was performed after changing the pressing position to the outside respectively. In addition, in #1 stand and #2 stand, rolling was carried out according to the rolling position set initially.

<Comparative example 1>

Only in #5 stand and #6 stand, when rolling the end portion of the billet, the rolling was carried out after changing the pressing position of the grooved rolling roll to the outside in the pattern shown in FIG. 4 . In stands #1 to #4, rolling was carried out at the initial set reduction position.

<Evaluation>

The defect rate of the shell thickness after rolling of Example 1-1 - Example 1-3 and the comparative example 1 was evaluated. Here, regarding the end of the rolled tube, if there is a difference between the actual thickness and the target value of the thickness (for example, in the case of Example 1, the target thickness of the end is 5.5mm), relative to the target value of thickness If there is a measurement position exceeding the range of ±0.2%, it is determined that the thickness is defective. The thickness defective rate is defined by the following formula.

Thickness defect rate = number of defective thickness pieces/total number of rolling pieces×100(%)

The evaluation results are summarized in Table 1.

[Table 1]

Wall thickness defective rate Example 1-1 0% Example 1-2 0% Example 1-3 0% Comparative example 1 10%

As shown in Table 1, unlike Comparative Example 1, in all of Examples 1-1 to 1-3, it can be seen that the end portion of the blank tube can be rolled to a desired thickness with high precision.

Example 2

<Example 2-1>

In #5 stand and #6 stand, when rolling the end of the next tube blank, the pattern shown in Figure 4 is changed according to the actual thickness of the previous tube blank measured by the thickness gauge, According to the changed pattern, the pressing position of the grooved rolling roll is changed outward. That is, in order to bring the actual thickness close to the target thickness, only the set value (pressing position fluctuation amount) is changed by an amount corresponding to the difference between the actual thickness and the target thickness. However, if the actual thickness is less than the target thickness, it is determined that empty rolling occurs at the bottom of the groove, and the change of the set value corresponding to the actual thickness (the above-mentioned pattern change) is interrupted. The setting value is rolled. In stands #1 to #4, rolling was carried out at the initial set reduction position.

<Example 2-2>

In #5 stand and #6 stand, rolling was carried out in the same manner as in Example 2-1. By comparing the variation of the pressing position of the grooved rolling roll with the variation of the actual thickness measured by the thickness gauge along the direction of variation of the grooved rolling roll, if the variation is less than 0.5 times the variation , it can be determined that the empty rolling phenomenon occurs at the bottom of the groove.

<Example 2-3>

In #5 stand and #6 stand, when the end of the tube blank to be rolled next time is rolled, the pattern shown in Figure 4 is changed according to the actual thickness measured by the thickness gauge, and the pattern shown in Figure 4 is changed according to the changed The rolling is performed after the pattern moves the pressing position of the grooved rolling roll to the outside. Also in #3 stand and #4 stand, rolling was performed with the same pattern as #5 stand and #6 stand, after changing the pressing position of the groove rolling roll to the outside. In #1 and #2 stands, rolling was carried out according to the initial set reduction position.

<Example 2-4>

In #5 stand and #6 stand, rolling was performed in the same manner as in Example 2-3. In the #3 stand and the #4 stand, the variation amount of the pattern of the #5 stand and the #6 stand was reduced to 0.8 times, and rolling was performed. In #1 and #2 stands, rolling was carried out according to the initial set reduction position.

<Example 2-5>

In #5 stand and #6 stand, rolling was performed in the same manner as in Example 2-3. In #3 stand and #4 stand, before the rolling of the tube billet, in order to make the target thickness into 6.5mm (#3 stand) and 6mm (#4 stand) respectively, the pass rolling Rolling was performed after changing the pressing position of the rolls to the outside. In #1 and #2 stands, rolling was carried out according to the initial set reduction position.

<Example 2-6>

In #5 stand and #6 stand, rolling was performed in the same manner as in Example 2-3. When the actual thickness is smaller than the target thickness, it is judged that the empty rolling phenomenon occurs at the bottom of the groove. The upstream stand (at least any one of #3 and #4) in the downward direction is also the same as #5 and #6 stands, after changing the pressing position of the groove rolling roll to the outside with the pattern rolled. In #1, #2 stands and #3, #4 stands where the reduction positions of the grooved rolling rolls were not changed, rolling was performed at the initially set reduction positions.

<Example 2-7>

Rolling was performed in the same manner as in Example 2-6. However, the presence or absence of idle rolling at the bottom of the groove is judged as follows: through the variation of the reduction position of the grooved rolling rolls, and the change of the actual thickness along the direction of the variation of the grooved rolling rolls measured by the thickness gauge If the variation is less than 0.5 times of the variation, it can be judged that empty rolling occurs at the bottom of the groove.

<Comparative example 2>

Only in #5 stand and #6 stand, when rolling the end of the tube blank to be rolled next time, the pattern shown in Figure 4 is changed according to the actual thickness measured by the thickness gauge, so that after the change The pattern makes the pressing position of the grooved rolling roll move outward. For stands #1 to #4, rolling was carried out according to the initial settings.

<Evaluation>

The defect rate of the shell thickness after rolling of Example 2-1 - Example 2-7 and the comparative example 2 was evaluated. The thickness defective rate was calculated by the above-mentioned formula. In addition, the frequency with which the rolling position of the grooved rolling rolls arranged on the finishing stands, that is, #5 and #6 stands, fluctuates outward from the initial setting value to 1 mm or more was evaluated. This frequency is an evaluation index corresponding to the frequency at which the grooved rolling rolls of the finishing stand move outward without restriction when the empty rolling phenomenon occurs at the bottom of the groove and the actual thickness is smaller than the target thickness.

The evaluation results are shown in Table 2.

[Table 2]

Wall thickness defective rate Press position change frequency Example 2-1 4% 4% Example 2-2 4% 0% Example 2-3 0% 0% Example 2-4 0% 0% Example 2-5 0% 0% Example 2-6 1% 0% Example 2-7 1% 0% Comparative example 2 5% 0%

As shown in Table 2, compared with Comparative Example 2, it can be seen that in Examples 2-1 to 2-7, the end portion of the blank tube can be rolled to a desired thickness with high precision. In addition, unlike Comparative Example 2, it was possible to prevent the grooved rolling rolls of the finishing stand from moving outward without restriction.

Industrial Utilization Possibility

When manufacturing a seamless pipe using a mandrel mill, it is possible to roll a part or the whole of the end portion of the billet to a desired thickness with high precision.

Claims (15)

1. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, with described fine finishining support depress direction identical near the upstream support in when pipe is rolled, the depressing position and the described first pass Rolling roller that are equipped on the second groove rolling roller on this upstream support are changed equally laterally.

2. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, before pipe is rolled, makes in advance to be provided in and change laterally with the depressing position of depressing the second groove rolling roller near the identical upstream support of direction of described fine finishining support.

3. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, when on the fine finishining support, pipe being rolled, the depressing position that is provided in the first pass Rolling roller on this fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets along the thickness meter of the measurement pipe thickness of depressing direction of each support, compare to the target thickness of predefined pipe on described fine finishining support with the actual (real) thickness of the pipe of described thickness instrumentation amount, described actual (real) thickness is during less than described target thickness, to rolling pipe next time, interrupt the change of the depressing position of described first pass Rolling roller.

4. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets the thickness meter of measuring pipe thickness, the variation of the depressing position of more described first pass Rolling roller and by the pipe of described thickness instrumentation amount variable quantity along the actual (real) thickness of the change direction of described first pass Rolling roller, when described variable quantity during less than described variation, for rolling pipe next time, interrupt the change of the depressing position of described first pass Rolling roller.

5. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets the thickness meter of measuring pipe thickness, calculate the depressing position after the change of described first pass Rolling roller of this rolling pipe, poor with depressing position after the change of described first pass Rolling roller of rolling pipe last time, and calculate the actual (real) thickness by described thickness instrumentation amount of this rolling pipe along the change direction of described first pass Rolling roller, poor along the actual (real) thickness of the change direction of described first pass Rolling roller with rolling pipe last time by described thickness instrumentation amount, the difference of described depressing position and the difference of described actual (real) thickness are compared, when the difference of described actual (real) thickness during less than the difference of described depressing position, for rolling pipe next time, interrupt the change of the depressing position of described first pass Rolling roller.

6. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets the thickness meter of measurement along the pipe thickness of depressing direction of each support, relatively at the target thickness of the predefined pipe of described fine finishining support with the actual (real) thickness of the pipe of described thickness instrumentation amount, when described actual (real) thickness during less than described target thickness, be arranged in described fine finishining support near and the identical upstream support of depressing direction of thickness measure direction with result little with having obtained described actual (real) thickness, when next time, rolling pipe was rolled, the depressing position that is provided in the second groove rolling roller on the support of described upstream is also changed equally laterally with the depressing position of described first pass Rolling roller, perhaps before the pipe rolling to next time is rolled, make in advance to be provided near the depressing position that is positioned at the described fine finishining support and has second a groove rolling roller on the identical upstream support of depressing direction of the result's little thickness measure direction and to change laterally with having obtained described actual (real) thickness.

7. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets the thickness meter of measuring pipe thickness, variation to the depressing position of described first pass Rolling roller, with compare by the pipe of described thickness instrumentation amount variable quantity along the actual (real) thickness of the change direction of described first pass Rolling roller, when described variable quantity during less than described variation, be arranged in described fine finishining support near and have a upstream support of depressing direction identical with described thickness measure direction, when next time, rolling pipe was rolled, the depressing position that is provided in the second groove rolling roller on the support of described upstream is also changed equally laterally with the depressing position of described first pass Rolling roller, perhaps before the pipe rolling to next time is rolled, make in advance to be provided near the depressing position that is positioned at the described fine finishining support and has second a groove rolling roller on the upstream support of depressing direction identical and to change laterally with described thickness measure direction.

8. the control method for rolling of a mandrel mill, in each support that constitutes mandrel mill, the depressing position of the first pass Rolling roller that is provided on the fine finishining support is changed laterally, it is characterized in that, outlet side at described fine finishining support sets the thickness meter of measuring pipe thickness, calculate the depressing position after the change of described first pass Rolling roller of this rolling pipe, poor with depressing position after the change of described first pass Rolling roller of rolling pipe last time, and calculate the actual (real) thickness by described thickness instrumentation amount of this rolling pipe along the change direction of described first pass Rolling roller, poor along the actual (real) thickness of the change direction of described first pass Rolling roller with rolling pipe last time by described thickness instrumentation amount, the difference of described depressing position and the difference of described actual (real) thickness are compared, when the difference of described actual (real) thickness during less than the difference of described depressing position, be arranged in described fine finishining support near and have a upstream support of depressing direction identical with described thickness measure direction, when next time, rolling pipe was rolled, the depressing position that is provided in the second groove rolling roller on the support of described upstream is also changed equally laterally with the depressing position of described first pass Rolling roller, perhaps before the pipe rolling to next time is rolled, make in advance to be provided near the depressing position that is positioned at the described fine finishining support and has second a groove rolling roller on the upstream support of depressing direction identical and to change laterally with described thickness measure direction.

9. the rolling control device of a mandrel mill possesses: be used for being adjusted at each support that constitutes mandrel mill, be provided in the first depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support; Has the second depressing position adjusting device that the depressing position of the groove rolling roller near the same upstream support of depressing direction is adjusted to being provided in described fine finishining support; Send the calculation control device of indication of the depressing position adjustment amount of groove rolling roller to the described first depressing position adjusting device and the described second depressing position adjusting device, it is characterized in that, described calculation control device is according to the present position of pipe, by the indication of sending the depressing position adjustment amount of regulation, and implement the control method for rolling described in the claim 1 or 2 to the described first depressing position adjusting device and the described second depressing position adjusting device.

10. the rolling control device of a mandrel mill possesses: be used for being adjusted at each support that constitutes mandrel mill, be provided in the depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support; Be used for sending the calculation control device of indication of the depressing position adjustment amount of groove rolling roller to described depressing position adjusting device, it is characterized in that, described calculation control device is connected the outlet side that is equipped on described fine finishining support, on the thickness meter of measuring along the pipe thickness of depressing direction of each support, output according to this thickness meter, interrupt the indication that depressing position is adjusted by sending, and implement claim 3 each described control method for rolling to the claim 5 to described depressing position adjusting device.

11. the rolling control device of a mandrel mill possesses: be used for being adjusted at each support that constitutes mandrel mill, be provided in the first depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support; Has the second depressing position adjusting device that the depressing position of the groove rolling roller near the same upstream support of depressing direction is adjusted to being provided in described fine finishining support; Be used for sending the calculation control device of the indication of adjustment amount to described first depressing position adjusting device and the described second depressing position adjusting device, it is characterized in that, described calculation control device is connected the outlet side that is equipped on described fine finishining support, on the thickness meter of measuring along the pipe thickness of depressing direction of each support, according to the output of this thickness meter and the present position of pipe, the indication of sending the regulation adjustment amount to the described second depressing position adjusting device, thus claim 6 each described control method for rolling to the claim 8 implemented.

12. control program, it makes the running of calculation control device, this calculation control device is connected and is used for being adjusted at each support that constitutes mandrel mill, be provided in the first depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support, with have on the second depressing position adjusting device that the depressing position of the groove rolling roller near the same upstream support of depressing direction adjusts being provided in described fine finishining support, the indication of sending the depressing position adjustment amount of groove rolling roller to the described first depressing position adjusting device and the described second depressing position adjusting device, it is characterized in that, present position according to pipe, the indication of sending the depressing position adjustment amount of regulation to the described first depressing position adjusting device and the described second depressing position adjusting device, thereby make described calculation control device running, to implement the control method for rolling described in the claim 1 or 2.

13. control program, it makes the running of calculation control device, this calculation control device is connected and is used for being adjusted at each support that constitutes mandrel mill, be provided in the first depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support, with the outlet side that is provided in described fine finishining support on the thickness meter of measuring along the pipe thickness of depressing direction of each support, send the indication of the depressing position adjustment amount of groove rolling roller to described depressing position adjusting device, it is characterized in that, output according to described thickness meter, send the indication of interrupting the depressing position adjustment to described depressing position adjusting device, thereby make described calculation control device running, to implement each described control method for rolling in the claim 3 to 5.

14. control program, it makes the running of calculation control device, this calculation control device is connected and is used for being adjusted at each support that constitutes mandrel mill, be provided in the first depressing position adjusting device of the depressing position of the groove rolling roller on the fine finishining support, with have the second depressing position adjusting device that the depressing position of the groove rolling roller near the same upstream support of depressing direction is adjusted to being provided in described fine finishining support, with the outlet side that is provided in described fine finishining support on the thickness meter of measuring along the pipe thickness of depressing direction of each support, the indication of sending adjustment amount to the described first depressing position adjusting device and the described second depressing position adjusting device, it is characterized in that, according to the output of described thickness meter and the present position of pipe, the indication of sending the regulation adjustment amount to the described second depressing position adjusting device, thereby make described calculation control device running, to implement each described control method for rolling in the claim 6 to 8.

15. a seamless pipe is characterized in that, forms by the mandrel mill manufacturing of adopting each described control method for rolling in the claim 1 to 8.

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