JP2005270982A - Method for controlling cooling of material to be rolled in hot rolling - Google Patents

Abstract

[PROBLEMS] In hot rolling to roll, cool, and wind a heated material to be rolled, the supplied cooling water is water on the material to be rolled in some parts where the shape of the tip of the material to be rolled has deteriorated. It becomes a pool, causing uneven cooling in the longitudinal direction and width direction of the material to be rolled, the winding temperature in the longitudinal direction and width direction of the material to be rolled fluctuates, and uniform mechanical properties are obtained over the entire width of the product metal plate. This prevents cracking of the material to be rolled due to local overcooling.
The shape of the tip of the material to be rolled 8 after the end of rolling is measured, and feedforward is performed for winding temperature control.
[Selection] Figure 3

Description

  The present invention relates to a cooling control method for a material to be rolled in hot rolling. Here, the cooling control of the material to be rolled in hot rolling is determined based on the material of the material to be rolled and the required mechanical properties, that is, the temperature of the material to be rolled before winding, that is, the coiling temperature (CT). This is done by controlling to a desired range.

  For example, a metal plate represented by a steel strip (including a metal strip) is a pair of rolls of metal lump (slab) heated to a high temperature of several hundred to several hundreds of degrees C and sandwiched between a pair of upper and lower rolls. It is manufactured by extending thinly by rotating.

  Several examples of the hot rolling line are shown in FIGS. 7 to 11. In addition to the type called (a) semi-continuous shown in FIG. 7, there is a type called (b) 3/4 continuous shown in FIG. Many. On the other hand, although not shown, there is also what is called complete continuous in which there are five or more rough rolling mills. In recent years, as shown in FIG. 9, (c) a type called a hot endless rolling line in which the tip and tail ends of a metal material in the middle of rolling are joined to each other while following a 3/4 continuous shape. Has also appeared. In addition, there is a type called (d) Steckel mill shown in FIG. 10 and a type called (e) Nucore type shown in FIG.

  7 to 11, 1 is a heating furnace, 2 is a roughing mill, 3 is a crop shear, 4 is a descaling device, 5 is a finishing mill, 6 is a cooling zone, 7 is a coiler (winding device), 9 Is a measuring roll. Between each facility, there are a large number of table rollers (not shown), whereby the metal material 8 (hereinafter simply referred to as the material to be rolled) 8 is conveyed.

  Since there are a plurality of rough rolling mills 2 and finish rolling mills 5, the initials of Rougher and Finisher are taken, the numbers of the respective stands are given, and abbreviated as R1, R2, R3, F1, F2,. The Similarly, there are a plurality of coilers 7, which are abbreviated as DC1, DC2, etc., with unit numbers assigned.

  (A) In the type called semi-continuous, the rough rolling by the rough rolling mill 2 performs one-pass rolling while transporting the material 8 from the upstream side to the downstream side of the hot rolling line, and stops conveying the material 8. This time, it is carried out by a reciprocating rolling method called reverse rolling, which repeats a series of operations of carrying out the one-pass rolling while conveying the material to be rolled 8 from the downstream side to the upstream side. The material to be rolled 8 after the completion of the rough rolling is sequentially finished and rolled by the finish rolling mill 5, cooled in the cooling zone 6, and taken up by the coiler 7.

  (B) In a type called 3/4 continuous, there are a plurality of rough rolling mills 2, for example, in many cases four, some of which, for example, in many cases one is reciprocating, and the remaining rolling mill is in one direction. Roll. It is not limited to the type in which 3 out of 4 machines are unidirectionally rolled.

  (C) In a type called complete continuous, each rough rolling mill having 5 or more rolls performs one-pass unidirectional rolling.

  In the type called (a) semi-continuous, the type called (b) 3/4 continuous, or the type called (c) full continuous, the finish rolling mill 5 bites the tip of the material 8 to be rolled, and rolls. Hot rolling is performed in which the operation of rolling the tail end is repeated intermittently. Such a rolling method is particularly referred to as batch rolling.

  As described above, in recent years, a type called a (d) hot endless rolling line that joins the tip and tail ends of a metal material in the middle of rolling has also appeared. This is (b) a joint that joins the tail end of the preceding rolled material and the tip of the subsequent rolled material between the most downstream roughing mill and the finishing mill while following the 3/4 continuous shape. A device 35 is installed, and a cutting device 71 is installed between the finishing mill 5 and the coiler 7 for cutting the preceding rolled material and the subsequent rolled material and winding them separately.

  Joining the tip and tail ends of a metal material in the middle of rolling and continuously finish rolling is called endless rolling, which is distinguished from the batch rolling described above.

  This (d) hot endless rolling line is provided with a coil box 25 and a joining crop shear 31 in addition to the joining device 35 in order to join the tail end of the preceding rolled material and the tip of the following rolled material. . And the cutting apparatus 71 which cut | disconnects the to-be-rolled material after joining and carrying out finish rolling continuously is installed. Alternatively, a deburring device 36, a sheet bar heater 37, an edge heater 38, a joint cooling device 39, a high-speed plate device 72, and the like may be installed as appropriate.

  (E) The type called the stickel mill has only one finish rolling mill 5, which performs one-pass rolling while conveying the material to be rolled from the upstream side to the downstream side, and stops conveying the material to be rolled, This time, a series of operations are repeated in which the material to be rolled is conveyed from the downstream side to the upstream side for one pass rolling. In order to avoid hardening due to a temperature drop of the material to be rolled, the material to be rolled after one pass is wound up by the furnace coiler 40 and heated in the furnace coiler 40.

  In what is called (f) Nucore type shown in FIG. 11, the material to be rolled 8 is directly cast by the slab continuous casting equipment 50 and supplied to the heating furnace 1.

  By the way, the rolled material to be rolled is wound up by a winding device (7) to become a metal plate product wound in a coil shape, but in order to satisfy the mechanical properties required for the product, the winding temperature In order to control the coiling temperature, the coiling temperature in the longitudinal and width directions of the material to be rolled is obtained in order to obtain as uniform mechanical properties as possible over the entire length and width of the material to be rolled. Is required to be as uniform as possible.

  In order to meet these requirements, a model consisting of the target target coiling temperature in the unsteady part between the most advanced part and the steady part of the hot-rolled steel sheet, the target plate thickness, the distance from the most advanced part to the steady part, etc. Patent Document 1 proposes a control method for correcting by adding up the winding temperature correction amount of the tip portion expressed by the equation.

  Further, from the viewpoint of poor dimensional accuracy, the surface roughness of the hot rolled steel sheet after hot finish rolling is adjusted to about 1.0 to 1.5 μm in Ra display, thereby attempting to make the coiling temperature uniform. A method is shown in US Pat.

  Furthermore, in order to make the coiling temperature of the hot-rolled steel sheet uniform, the amount of cooling water is set in the longitudinal direction of the material to be rolled by predicting the amount of supercooling at the tip and setting a target pattern in the longitudinal direction of the material to be rolled. A method of changing is described in Patent Document 3, and a method of appropriately controlling the coiling temperature by feedback control is described in Patent Document 4 even when the speed of the material to be rolled varies during rolling.

JP-A-6-71321 Japanese Patent No. 3,238,569 JP 2003-25008 A JP 2003-48012 A

  However, the technique described in Patent Document 1 is correction based on a model formula, and is not necessarily effective for all materials to be rolled.

  Patent Document 2 does not describe the unsteady portion at the tip. Here, the unsteady portion is a portion where the flatness control is not sufficiently effective after rolling the tip with a final rolling mill (final pass), or further, the shape is not flat until the tip is wound around the winding device. Refers to the part.

  The flatness control refers to feedback control by controlling the bender, roll cloth, or roll shift while running after the flatness at the tip of the material to be rolled is captured by a sensor in the final rolling mill.

  Furthermore, even if the above-described winding temperature control is performed, the material to be rolled after rolling is bitten into the winding device particularly from the tip, in view of the current level of accuracy of crown and shape control during rolling. It is not easy to make the part (unsteady part) at the tip of the material to be rolled corresponding to a flat shape at all, and the shape of the part may be deteriorated, but such a shape is deteriorated. 12, the cooling water supplied for cooling the material to be rolled 8 in the cooling zone 6 becomes a pool of water on the material to be rolled, as shown in FIG. Uneven cooling in the longitudinal direction and width direction of the material occurs, the winding temperature in the longitudinal direction and width direction of the material to be rolled fluctuates, and uniform mechanical properties over the entire length of the product metal plate cannot be obtained, or localized The material to be rolled breaks due to overcooling. That there was a need to suppress.

  The present invention has been made to solve the above-mentioned conventional problems, and makes the winding temperature of the material to be rolled uniform in the longitudinal direction and the width direction, and obtains uniform mechanical properties over the entire length of the product metal plate. It is an issue.

  In the present invention, the hot rolled material is rolled, cooled, and wound up. In hot rolling, the shape of the tip of the rolled material after rolling is measured, and feedforward control is performed for winding temperature control. The above-described problems are solved by the featured cooling control method for a material to be rolled in hot rolling.

  According to the present invention, the winding temperature of the material to be rolled can be made uniform in the longitudinal direction and the width direction, and uniform mechanical properties can be obtained over the entire length of the product metal plate, in particular, with a metal plate such as high-carbon steel. In a portion where the shape of the tip portion immediately after the end of rolling is not flat, it is possible to suppress a local supercooled portion that is thought to be caused by a pool of cooling water from cracking.

During the process of cooling the surface of the metal plate with cooling water, the boiling phenomenon changes from film boiling to transition boiling at the boundary between the cooling water and the surface of the metal plate. It is reflected in the calculation formula predicted by calculation. For this purpose, the heat transfer coefficient α at the time of cooling the metal plate surface with cooling water is a function of the metal plate surface temperature Ts as α ₀ shown in the following equation (1) at the reference cooling water temperature Tw ₀ . Suppose that it is given by f (Ts).

α ₀ = f (Ts) (1)

  Here, f (Ts) is a function representing a heat transfer coefficient having a portion that increases as the metal plate surface temperature falls below the transition boiling start temperature. This is a function that the heat transfer coefficient increases when the metal plate surface temperature falls below the transition boiling start temperature. Taking the case where the metal plate cooled by the cooling water is a steel plate as an example, in the region where the metal plate surface temperature is from 550 ° C. to 400 ° C., the heat transfer coefficient is a function that increases as the metal plate surface temperature decreases. FIG. 1 schematically shows the relationship between the metal plate surface temperature Ts and the heat transfer coefficient α when the metal plate surface is cooled by cooling water, taking the case where the metal plate is a steel plate as an example.

Apart from that, as is well known qualitatively from the past, the heat transfer coefficient when cooling the metal plate surface with cooling water increases as the cooling water temperature Tw (° C.) decreases. . This is schematically shown in FIG. 2 as the relationship between the metal plate surface temperature Ts and the heat transfer coefficient α when the metal plate surface is cooled by cooling water. In contrast to the heat transfer coefficient α ₀ at the cooling water temperature Tw _0, the heat transfer coefficient α when the surface of the metal plate is cooled by the cooling water is expressed by the following equation (2). Become.

α = kα ₀ = (1 + r ₁ (Tw ₀ −Tw)) α ₀ (2)
here,
f (Ts): function example 1 representing a heat transfer coefficient having a portion that increases as the metal plate surface temperature falls below the transition boiling start temperature 1: f (Ts) = a + b exp (c Ts)
Example 2: f (Ts) = erfc (Ts)
Ts: metal plate surface temperature Tw ₀ : reference cooling water temperature α ₀ : heat transfer coefficient Tw at reference cooling water temperature Tw ₀ : cooling water temperature r ₁ : proportionality constant. Incidentally, when the heat transfer coefficient increases by 1% every time the temperature of the cooling water decreases by 1 ° C., r ₁ = 0.01.

  And according to following (3) Formula, the temperature T of a metal plate is estimated and calculated.

T = T ₀ -α (Ts−Tw) × t / c (3)
here,
T ₀ : Pre-prediction calculation temperature t: Elapsed time c: Specific heat of the metal plate.

Then, the results of the winding temperature prediction are manually returned, and the constants such as a, b, c, and r ₁ are optimized according to the type of the metal plate so that the prediction calculation result of the winding temperature matches the results. To do.

In the example of r ₁ , when the target winding temperature is 550 ° C. or higher, r ₁ = 0.01 (the heat transfer coefficient changes by 1% per 1 ° C.), and the winding temperature is 470 ° C. or higher. When it is less than 550 ° C., r ₁ = 0.02 (changes by 2% per 1 ° C.), and when the coiling temperature is less than 470 ° C., r ₁ = 0.03 (changes by 3% per 1 ° C.) And so on.

  Hereinafter, an example of an embodiment for applying the present invention to an actual hot rolling line will be described with reference to the drawings.

  FIG. 3 is a schematic configuration diagram in which a part of the 3/4 continuous hot rolling line described with reference to FIG. 8 described above is extracted and enlarged, to which the method for controlling cooling of the material to be rolled according to the present invention is applied. . In FIG. 3, the hot rolling line 100 includes a heating furnace 1, a plurality of rough rolling mills 2 (R <b> 1 to R <b> 3), a crop shear 3, a descaling device 4, in the order from the transport direction upstream to the downstream of the material 8 to be rolled. A plurality of finishing rolling mills 5 (F1 to F7), a cooling zone 6, and a coiler 7 are sequentially arranged. A roughing side thermometer 10 is provided on the exit side of the roughing mill 2, a finishing input thermometer 11 is provided on the entrance side of the finishing mill 5, a speedometer 12 is also provided on the final F7 stand, and finish rolling is also shown. A flatness meter 13, a finishing delivery thickness gauge 14, and a finishing delivery thermometer 15 are installed on the exit side of the machine 5, and a winding thermometer 16 is installed on the entrance side of the coiler 7. In the figure, 9 is a measuring roll for tracking the material 8 to be rolled, 81 is a host computer, 82 is a computer, and 83 is a control device.

  Here, when the material to be rolled 8 roughly rolled by the roughing mill 2 is conveyed to just below the roughening side thermometer 10 and the tip thereof reaches directly below the roughening side thermometer 10, the material to be rolled 8 The temperature at the tip of the is transmitted from the roughing side thermometer 10 to the computer 82. In the computer 82, it is determined whether or not the temperature of the tip of the material 8 to be rolled is equal to or higher than a predetermined threshold value. If the temperature is equal to or higher than the threshold value, the tip of the material 8 to be rolled is roughened. It is determined that the temperature has reached directly below the thermometer 10. Then, in the computer 82, the material to be rolled 8 from the host computer 81 higher than the computer 82 is triggered by determining that the tip of the material to be rolled 8 has reached directly below the roughening side thermometer 10. Set the target CT pattern in the longitudinal direction (CT means coiling temperature), and start the calculation of the spray pattern (water injection bank pattern) of the water injection bank in the longitudinal direction of the rolled material to achieve it Is done. This water injection bank pattern calculation is also transmitted from the host computer 81, and the longitudinal target FDT pattern of the material to be rolled (target FDT. FDT is the finish rolling mill exit side temperature (also referred to as post-finishing temperature): Finisher Delivery (Temperture), longitudinal target CT pattern (target CT) of the material to be rolled, thickness of the material after finish rolling, threading speed of the material 8 shown in FIG. 4, and top speed of the material 8 to be rolled Based on.

  Here, as shown in FIG. 4, the threading speed and the top speed of the material 8 to be rolled are, in the acceleration / deceleration pattern when the material 8 is finish-rolled, the tips of the material 8 to be rolled one after another. When turning on each stand of the finish rolling mill 5, the low speed for preventing the bumping is set to the threading speed, and further, the tip of the material 8 to be rolled advances, and the acceleration is started immediately after being wound around the coiler 7. However, a high speed for temperature drop compensation for securing the material of the material to be rolled is referred to as a top speed.

  In FIG. 4, when the tip of the material to be rolled 8 is turned on to the F1 stand of the finishing mill 5, the sheet is passed at a threading speed from (a) to when the tip is wound around the coiler 7 (b). Accelerate immediately after winding on 7, and maintain the top speed until (c) when the tail end of the material 8 is turned off from the F1 stand, and further decelerate until the tail end winding is completed (d) It is threading.

  Here, the target CT pattern in the longitudinal direction of the metal material to be rolled is provided with a setting table in the host computer 81, and data such as the type of the material to be rolled 8, the thickness after finish rolling, and the width are used as keys. Set for each tip, middle, and tail. However, the present invention is not limited to this, and a setting table may be provided in the computer 82 for setting.

  When the water injection bank pattern is calculated in the calculator 82, the finish rolling mill outlet temperature FDT at the tip region of the material 8 to be rolled, the winding temperature CT at the tip region of the material 8 to be rolled, and the tip of the material 8 to be rolled A water injection length L when the region passes through the cooling zone 22 is predicted.

  Every time the calculator 82 determines that the tip of the new material 8 to be rolled has reached directly below the roughening side thermometer 10, the computer 82 sets the longitudinal target CT pattern, and then sets the new longitudinal target CT pattern. Calculate the water injection bank pattern to achieve.

  This calculation includes the longitudinal target CT pattern, the longitudinal target FDT pattern of the material 8 to be rolled, the thickness of the material 8 to be rolled after finish rolling, the threading speed of the material 8 to be rolled, On the basis of the top speed of the material 8 to be rolled (see FIG. 4), as shown in FIG. 5, for each continuous cut plate 8a virtually divided into several m pitches in the longitudinal direction of the material 8 to be rolled, It is calculated by the following calculation logic.

  Here, the finishing mill exit side temperature FDT of the tip region of the rolled material 8 predicted by the calculation of the water injection bank pattern in the computer 82 and the winding of the tip region of the rolled material 8 predicted by the calculation The difference from the temperature CT corresponds to the calculation result of the water injection start bank entry side temperature-the water injection end bank exit side temperature at the tip of the material 8 to be rolled, and is also obtained by the water injection bank pattern calculation. The distance of the water injection end bank corresponds to the water injection length L.

  Although it is the outline of the calculation logic of the water injection bank pattern, first, as shown in FIG. 5, the cut plate 8a is taken up and considered, where the cut plate 8a in the rolled material 8 is located in the longitudinal direction, and the finish Data indicating which position corresponds to the state of the rolled material 8 before the start of rolling, and how much the temperature of the roughed rolled material at that position was (measured by the roughened thermometer 10). Subsequent calculations are performed. Based on the above threading speed, top speed, and mechanical distance between each component, calculate the time required to reach the main components (F1, F7, cooling zone 6 entry and exit sides) Then, based on the required time, the temperature drop of the material to be rolled 8 due to cooling until reaching the entry side of the cooling zone 6, the descaling water by the descaling device 4, and the stands in the finishing mill 5 Temperature fluctuations such as a temperature drop of the material 8 due to cooling water injection from a cooling device (not shown) installed in the machine and a temperature rise of the material 8 due to heat generated during finish rolling are calculated for each cut plate 8a. Then, how much temperature is reached when the cut plate 8a reaches the entrance side of the cooling zone 6 is calculated. Then, based on the temperature, it is calculated which bank can be cooled to the target coiling temperature CT when the cooling water jet state is set when passing through the cooling zone 6.

  Here, which bank is used for cooling water injection when passing through the cooling zone 6, the cutting plate 8 a can be cooled to the target winding temperature CT, or when cooling water injection is performed from one bank, The time required for the cut plate 8a to pass through the zone corresponding to the bank is calculated based on the above-mentioned threading speed, top speed, and mechanical distance between each component equipment. Determine how many degrees C the cut plate 8a is cooled to, and if it is still higher than a target coiling temperature CT by a certain value, determine if the bank immediately downstream is also injected. You may obtain | require by the convergence calculation which repeats a series of calculation processes of calculating to.

  At the time of those calculations, the calculation is performed according to the above formulas (1) to (3).

  In addition, in this invention, when performing flatness control, the front-end | tip part is substantially equal to the machine length from the roll axial center of the final rolling mill F7 of the finishing mill 5 to the measurement center part of the flatness meter 13. Is preferably equal to. Substantially, the length of the material to be rolled (conveyed during the time corresponding to the time delay until the flatness control actually starts after the leading edge of the material to be rolled reaches the flatness meter 13. This also includes the case of adding the amount of (which also depends on the conveyance speed for each rolled material).

  When flatness control is not performed, the DC1 inlet (not shown, but a pinch roll is installed) of the coiler 7 closest to the finishing mill 5 from the roll axis of the final rolling mill F7 of the finishing mill 5 For this reason, it is preferable to determine a fixed appropriate value, for example, 5 m, 10 m, or 30 m, as long as it does not exceed the mechanical length up to the axis). However, whether the flatness control is performed or not is not limited to these determination methods.

  In this invention, the shape of the front-end | tip part of the to-be-rolled material after completion | finish of rolling is measured, and it feeds forward to coiling temperature control.

  For example, in the case of a 3/4 continuous hot rolling line as shown in FIG. 8, the material to be rolled measured by the flatness meter 13 installed on the exit side of the final stand F7 of the finishing mill 5 is used. The shape of the tip is transmitted to the computer 82, and in the computer 82, for example, it is reflected in the above-mentioned equation (2), for example, in the form described below, and as a result, feedforward control is performed.

As shown in FIG. 6, the shape of the tip portion of the material to be rolled is represented by a steepness λ obtained by dividing the height h of the plate wave in the longitudinal direction by the wavelength l, and r ₁ in the above equation (2). Is corrected to (1 + λ) times,
α = (1+ (1 + λ) r ₁ (Tw ₀ −Tw)) α ₀ (4)
The above equation (4) is used instead of the equation (2).

However, it is only an example, and using appropriate constants a ₁ and b ₁ ,
α = (1+ (a ₁ (1 + λ) + b ₁ ) r ₁ (Tw ₀ −Tw)) α ₀ (5)
The above formula (5) or a completely different formula not introduced here may be used instead of the formula (2).

  Such a calculated water injection bank pattern is transmitted to the control device 83, and the control device 83 controls cooling of the material 8 to be rolled by the cooling zone 6 by the transmitted water injection bank pattern. Specifically, a lot of data is transmitted to the control device 83 based on the computer setting of the bank for injecting the cooling water and the target cutting plate 8a, and the control device 83 injects the cooling water for the cutting plate 8a in real time. The arrival at each bank is determined based on tracking using both the measuring roll 9 and the speedometer 12, and the delay time from the opening and closing of the valve to the start and stop of injection of cooling water is appropriately considered, In accordance with the arrival timing, the opening and closing of the valves for starting and stopping the injection of the cooling water in each header of each bank is controlled. The command may be issued earlier by the time lag from the valve opening command to the cooling water injection and from the valve closing command to the cooling water stop.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change can be made. For example, as shown in FIG. 3, it is cut directly under each of a finishing entry thermometer 11 installed on the entry side of the finishing mill 5 and a finishing delivery thermometer 15 installed on the exit side of the finishing mill 5. The temperature of the cut plate 8a when the plate 8a arrives is calculated in advance, and the deviation between the actual finish side temperature measured by the finish input side thermometer 11 of the cut plate 8a and the calculated finish side temperature The number of cooling water injection banks in the cooling zone 6 is obtained by taking the deviation between the finished delivery side temperature record by the finished delivery side thermometer 15 of the cut plate 8a and the calculated finished delivery side temperature and multiplying by an appropriate gain. The feed forward control may be used in combination with the adjustment of the feed rate, and the temperature of the cut plate 8a when the cut plate 8a reaches directly below the winding thermometer 16 installed on the exit side of the cooling zone 6 is previously determined. Obtained by calculation, the cutting plate 8a It uses feedback control that adjusts the number of cooling water injection banks in the cooling zone 6 by taking the deviation between the actual winding temperature CT by the taking thermometer 16 and the calculated winding temperature CT and multiplying by an appropriate gain. May be. Alternatively, when the tip of the material to be rolled 8 arrives directly under the finish input side thermometer 11 instead of the roughing side thermometer 10, the correction calculation of the water injection bank pattern in the longitudinal direction of the material to be rolled is started. Of course.

  Further, the embodiment of the present invention does not limit the application target to the 3/4 continuous hot rolling line shown in FIG. 8, and is semi-continuous shown in FIG. 7, completely continuous not shown, or FIG. A hot endless rolling line as shown in FIG. 10, a stickel mill as shown in FIG. 10, or a thin slab is continuously cast and finish-rolled directly without rough rolling, a hot rolling line as shown in FIG. The present invention can be applied to other types of hot rolling lines, and the material 8 to be rolled need not be limited to steel, but may be aluminum or other metals.

  According to the present invention, the shape of the tip of the material to be rolled after rolling is measured, and feedforward is performed for the coiling temperature control. I can do it.

  The effect of the present invention was proved by taking as an example the case of rolling a low carbon steel having a thickness of 2.0 mm and a width of 1000 mm after finish rolling and having a target CT of 670 ° C. and a tolerance of ± 50 ° C.

  Table 1 summarizes the shape of the tip, whether or not the feedforward control of the present invention is performed, and whether or not cracking occurs. As shown in Table 1, it can be seen that even if the shape of the tip portion is bad, it is possible to suppress the occurrence of cracks by performing feedforward control.

  In the method of controlling the cooling of the material to be rolled in hot rolling, the present invention contributes widely to suppressing the occurrence of cracks in the material to be rolled and stably producing a high-quality product metal plate.

The figure which shows the relationship between the metal plate surface temperature and a heat transfer coefficient for demonstrating the principle of this invention. The figure which similarly shows the change with the cooling water temperature of the relation between the metal plate surface temperature and the heat transfer coefficient Block diagram for describing an embodiment of the present invention Diagram for explaining threading speed and top speed of material to be rolled Top view showing a virtual cutting board Diagram for explaining the steepness of the shape of the tip of the material to be rolled Diagram showing the outline of a semi-continuous hot rolling line Diagram showing outline of 3/4 continuous hot rolling line Diagram showing outline of hot endless rolling line Diagram showing the outline of the Steckel mill Diagram showing the outline of a Noucore type hot rolling line Perspective view for explaining problems of the prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heating furnace 2 ... Rough rolling mill 3 ... Crop shear 4 ... Descaling device 5 ... Finishing rolling mill 6 ... Cooling zone 7 ... Coiler (winding device)
DESCRIPTION OF SYMBOLS 8 ... Rolled material 9 ... Measuring roll 10 ... Roughening side thermometer 11 ... Finishing input side thermometer 12 ... Speed meter 13 ... Flatness meter 15 ... Finishing side thermometer 16 ... Winding thermometer 80 ... Control apparatus 81 ... Host computer 82 ... Computer

Claims (1)

  In hot rolling to roll, cool, and wind up the heated material to be rolled, heat measured by measuring the shape of the tip of the material to be rolled after rolling and feeding forward to coiling temperature control A cooling control method for a material to be rolled in hot rolling.

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