JP2013066940A - Method and equipment for manufacturing small diameter metal pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform accurate molding into a cylindrical shape without lubrication by using a large diameter roll stand in which rolls having diameters clearly larger than the outer diameter of a pipe to be molded are arranged so as to manufacture a small diameter welded pipe with good production efficiency.SOLUTION: The roll stand including a pair of right and left side rolls is used. The roll stand uses the large diameter side rolls which are designed so that the outer diameter ratio φ/φof the outer diameter φof the molding roll to the outer diameter φof the pipe to be molded is 10 or larger, as the pair of side rolls. After a metal band is molded into a cylindrical shape through the roll stand in a single stand, abutment portions of edges of the metal band are welded and joined to each other. A three roll-type or a four roll-type can be used as the large diameter side roll. Since manufacturing in the single stand is enabled, this can reduce labor and time for roll exchange, so as to contribute to cost reduction.

Description

  The present invention relates to a method for manufacturing a metal pipe, in particular, a weld pipe having a small diameter such that the outer diameter is less than 20 mm, and an apparatus therefor.

In general, a weld metal pipe is manufactured by welding a metal band edge butt while continuously forming it into a cylindrical shape by a plurality of roll forming stands having ten or more stages arranged in tandem. The law is adopted. For example, as seen in Patent Document 1.
However, in the roll forming method, there are many roll forming stands when changing the size of the metal tube to be manufactured, so the work load associated with roll replacement work and dimensional adjustment by the operator is large, and the line down time is increased, resulting in increased production efficiency. Decreases. Furthermore, when manufacturing a small-diameter pipe whose outer diameter is less than 20 mm, for example, in pipe making with a multi-stage stand as in Patent Document 1, there are many adjustment points, and the steel strip meanders unless strict adjustment is performed on each stand. As a result, molding defects such as twisting and twisting occur, resulting in a significant reduction in production efficiency. When manufacturing small-diameter pipes, it is desirable to make pipes with as few stages as possible, and thus with a single stand, in order to improve work efficiency and productivity.

Further, a die draw forming method in which a metal strip is continuously drawn into a cylindrical shape by passing through a metal strip is also employed (see, for example, Patent Document 2).
However, in the die draw forming method, the die can be formed into a cylindrical shape with one stage, but the friction between the die and the tube material is significant, and the metal powder that has fallen from the metal bandage even when manufactured while using lubricating oil is accumulated, If the dies are not maintained frequently, the welding quality cannot be maintained, and furthermore, the surface flaws are so remarkable that a surface polishing treatment is required after pipe making.

JP-A-6-134525 JP-A-8-267150

By the way, regardless of the roll forming method or the die draw forming method, when manufacturing a welded pipe by welding a butt portion of a metal strip edge formed into a cylindrical shape, productivity and workability of the manufactured welded pipe are not affected. From the viewpoint, it is preferable to adopt a laser welding method as a welding method.
As described above, the roll forming method not only has a large work load associated with roll replacement work and dimension adjustment, but also when a small-diameter pipe is manufactured, a trouble is likely to occur in the butt portion due to slight adjustment errors.
Further, since the die draw forming method uses a large amount of lubricating oil, laser welding cannot be performed as it is.

  The present invention has been devised to solve such problems, and uses a large-diameter roll stand in which a roll whose diameter is clearly larger than the outer diameter of the pipe to be formed is used, and is lubricated. It is an object of the present invention to provide a method for manufacturing a welded pipe and an apparatus therefor by forming a cylindrical shape with high accuracy and then welding and joining the butt portion of the metal band edge.

In order to achieve the object, the method for producing a small-diameter metal tube of the present invention is a roll stand provided with a pair of left and right side rolls, with respect to the outer diameter φ _{1 of the} pipe formed as the pair of side rolls. Using a roll stand using a large-diameter side roll designed so that the outer diameter ratio φ ₂ / φ ₁ of the outer diameter φ ₂ of the roll to be molded is 10 or more, After forming into a cylindrical shape through a roll stand, the butt portion of the metal band edge is welded and joined.
The outer diameter ratio φ ₂ / φ ₁ is preferably 25 or more.
After bending the metal band edge by an edge bend roll stand, it is preferable to pass a large-diameter side roll.

In addition, you may shape | mold, adding a fin roll on the upper side as a four-way roll system, and maintaining the butting position of an edge with high precision.
Further, a fin roll may be arranged on the upper side immediately before the squeeze roll where welding is performed, and pipe formation may be performed while suppressing the occurrence of twisting. At this time, if a fin roll having a concave surface and a fin having a radius of curvature larger than the radius of the pipe to be obtained as the fin roll disposed immediately above the squeeze roll is used, the steel strip edge is pressed. However, since the shape of the abutting portion can be corrected to make a pipe, a small-diameter metal pipe with excellent forming accuracy can be obtained.

  In the present invention, the number of stands required for molding can be reduced by using side rolls having an outer diameter that is clearly larger than the outer diameter of the pipe to be molded, and a metal strip is formed into a cylindrical shape with a single stand. It becomes possible to do. In addition, the work load on the operator can be reduced by drastically reducing the number of stands, and a small-diameter pipe having excellent surface properties can be manufactured with high efficiency. In addition, through the appropriate use of fin rolls, small diameter tubes with excellent forming accuracy can be stably produced.

The perspective view which shows schematic structure of the large diameter side roll used by this invention Diagram showing the relationship between the outer diameter ratio φ ₂ / φ ₁ and the equivalent plastic strain at the edge of the steel strip The figure which shows the outline of the manufacturing line using the manufacturing method of the small diameter metal pipe of this invention. Sectional view showing the schematic structure of the edge bend roll Sectional drawing which shows schematic structure of large diameter side roll Diagram explaining the occurrence of problems when passing through side rolls Sectional drawing which shows the structure of the three-way roll type side roll which has arranged the bottom roll Top view showing the normal bottom roll installation position of the three-way roll side roll Top view showing the position of the bottom roll when the bottom roll of the three-way roll type side roll is offset to the line entry side Sectional drawing which shows the structure of the 4-way roll system side roll which has arranged the bottom roll and the fin roll The figure explaining the arrangement situation of a fin roll The figure explaining the difference of the shape of the open pipe butt part by the difference of the pipe diameter The figure explaining the desirable shape of the 2nd fin roll

1: Plate holder 2: Guide
3: Edge bend roll stand 4: Large diameter side roll stand
5: Squeeze roll stand 6: Pulling device
7: Welded pipe 8, 8 ': Fin roll
9: Bottom roll 10: Metal strip

In forming by the roll forming method, generally, it is gently formed by multi-stage forming using 10 or more roll forming stands arranged in tandem. For this reason, when changing the diameter of the welded pipe to be manufactured, it is necessary to replace all of the rolls of the plurality of stands to be used with those corresponding to the outer diameter of the manufactured welded pipe. And since it takes a lot of labor and a long time to change the roll, the cost is increased.
Therefore, it is possible to gently roll-form without using a large number of roll-forming stands, and at the stage where we are studying means that can reduce the strain that occurs during roll-forming, the strain that occurs slowly and with a single-stand roll-forming stand. The present invention has been found out that it can be molded so as to be small.
Details will be described below.

In the present invention, the roll formed into a cylindrical shape is not a multi-stage stand but can be formed with a single stand, so that the outer diameter of the roll formed with respect to the outer diameter of the pipe to be formed as shown in FIG. A large-diameter side roll designed to have a considerably large outer diameter ratio is used. Specifically, it is 10 or more.
Large-diameter side rolls designed so that the outer diameter ratio of the outer diameter of the roll to be molded to the outer diameter of the pipe is considerably large can be considered as a die, and it is a single stand, non-lubricated cylindrical molding Is now possible.
The large-diameter side roll is suitable for manufacturing a small-diameter welded pipe having an outer diameter of less than 20 mm because it requires a large roll diameter according to the shape of the cylinder to be molded. Requires a side roll with a suitable diameter, which is not realistic.

Here, a preferable relationship of the outer diameter ratio φ ₂ / φ ₁ will be described.
By using a side roll having a large outer diameter ratio φ ₂ / φ _1, which is a ratio of the outer diameter φ ₂ of the forming roll to the outer diameter φ _{1 of the} pipe to be formed, roll forming can be performed gently, that is, it occurs during forming Molding is possible while reducing strain.
FIG. 2 shows the relationship between the outer diameter ratio φ ₂ / φ ₁ and the equivalent plastic strain at the steel strip edge. By setting the outer diameter ratio to 10 or more, the strain generated at the steel strip edge is much smaller. And can be molded in a state where the cross-sectional shape when the edge is curved is good and there is no warpage. The outer diameter ratio is more preferably 25 or more. The upper limit of the outer diameter ratio does not need to be specified in particular, but it is practical to set it to about 80 considering that the effect of reducing the strain generated in the steel strip edge portion is saturated at about 80, the roll cost, and the like.

Cylindrical forming is possible with a single stand of large-diameter side roll, but in order to smooth the bending state of the edge of the metal strip to be formed, the edge bend roll stand is passed before passing the large-diameter side roll. It is preferable.
A practical line configuration to which the method of the present invention is applied is shown in FIG.
The rewound metal band 10 is passed by the edge bend roll stand 3 with the side edges aligned by the guide 2 while being pressed by the plate presser 1. The metal band whose side end is bent is formed into a cylindrical shape by the large-diameter side roll stand 4, and then the positional accuracy of the butt contact portion is increased by the fin roll 8, and when passing through the squeeze roll stand 5, a laser welding method or the like The welded pipe 7 is formed by welding. Reference numeral 6 denotes a drawing device.

As shown in FIG. 4, the edge bend roll stand 3 is a pair of upper and lower rolls provided with a concave groove with a side end R attached to one roll and a ridge with a side end R attached to the other roll. It is composed of
A metal strip having a bent side end through this roll stand is formed into a cylindrical shape when passing through the large-diameter side roll stand 4 shown in FIGS.

By the way, as shown to Fig.6 (a), shaping | molding to a cylindrical shape with a large diameter side roll is performed in the form which presses the board | plate material after edge bend roll from right and left with a large diameter side roll. At this time, since a gap is formed between the large-diameter side rolls, the material escapes into the lower gap (see FIG. 6B), and a defect may occur in the formed cylindrical shape.
In order to prevent this material from escaping downward, it is preferable to place a so-called “receiver” between the lower rolls.

As shown in FIG. 7, a bottom roll 9 is inserted between large-diameter side rolls whose lower side is cut to become “receiving”. It is preferable to arrange the bottom roll 9 and make the large-diameter side roll stand 4 a three-way roll system.
However, when the center line of the bottom roll 9 is arranged so as to coincide with the center line of the large-diameter side roll as shown in FIG. 8, a problem may occur when forming into a cylindrical shape. If the center line of the large-diameter side roll and the bottom roll are matched, the steel strip is constrained in the circumferential direction immediately below the roll, so it is presumed that the distortion occurs excessively and causes a problem. At the same time, when the center line is matched, the steel strip is formed so that the bottom of the pipe is bent downward and bent at the part that is not supported by the bottom roll slightly before the center of the roll, and the part that sinks after that is the bottom This is presumed to be caused by excessive distortion caused by bending and unbending that occurs when the roll is supported by a roll and causing a malfunction.
Therefore, the bottom roll is arranged offset to the line entry side (see FIG. 9). This allows the steel strip to escape without being constrained all around in the circumferential direction, and because there is little extra deformation due to bending and unbending, the amount of strain generated can be greatly reduced and molded. The shape and quality of the metal tube are greatly improved.

The butt portion of the metal band formed in a cylindrical shape is welded to form a metal tube. As shown in FIG. 3, the butt portion is held in a state where the metal band formed in a cylindrical shape is held by the squeeze roll stand 5. Although welded, the laser welding method is preferably used as the welding method from the viewpoint of productivity and workability of the manufactured metal pipe.
The welding method is not limited to the laser welding method, and arc welding methods such as TIG welding and plasma welding, high frequency welding methods, and the like may be used.
Not only the laser welding method, but also when welding the butt portion of the metal strip, it is preferable that the positioning accuracy of the butt contact portion is high and the weld line extends in a straight line.
In order to increase the positioning accuracy of the butt contact portion, in the present invention, roll molding is preferably performed by a four-way roll method in which fin rolls are added during side roll molding (see FIG. 10).

By the way, as shown in FIGS. 3 and 10, even if the fin roll 8 is provided immediately above the large-diameter side roll and roll forming is performed, as shown in FIG. 11A, for example, it is conveyed to the squeeze roll. In the meantime, twisting may occur in the circumferential direction, causing problems in welding. It is thought that the eccentricity of the material centering position and the eccentricity of the roll center at the time of feeding the steel strip are affected, but it is difficult to manually adjust such eccentricity, which increases costs. Is also not realistic.
Therefore, in the present invention, as shown in FIG. 11B, a second fin roll is also provided immediately before the squeeze roll.
That is, as shown in FIG. 3, the two fin rolls 8 and 8 'are arranged in series, and the positioning of the abutting portion at the time of pipe making is performed with high accuracy, and a shape in which the weld line extends in a straight line is obtained. Stable continuous pipe making becomes possible.

In addition, when steel strip is continuously formed by roll forming, the strain applied to each part of the steel strip is not uniform, and it is biased by various factors, so the shape of the left and right steel strip edges is unstable. Thus, a difference is likely to occur in the butt portion. Even if the step does not occur, for example, as shown in FIG. 12B, a butt failure of the edge portion is likely to occur and welding may be difficult. This phenomenon becomes more prominent as the diameter of the tube to be obtained becomes smaller. That is, as shown in FIG. 12A, if the diameter of the tube to be obtained is relatively large, the shape of the butt portion is I-shaped and can be butt welded without any problem, but the diameter of the tube to be obtained is a small Kunar, as seen in FIG. 12 (b), the shape of the butt portion causes causing welding defects become V-shaped.
Therefore, in the present invention, as the fin roll disposed immediately before the squeeze roll, as shown in FIG. 13, a pressing surface and a fin having a shape with a radius of curvature larger than the radius of the tube to be obtained are provided. A fin roll was used to correct the shape of the abutting portion while pressing the steel strip edge to make a pipe.

Example 1;
Next, we will introduce an example of manufacturing a welded pipe with an outer diameter of φ6.5 mm (φ ₁ ) using a stainless steel strip with a thickness of 0.5 mm having an 18Cr-1Mo-Ti-LCN composition.
As the production line, the line introduced in FIG. 3 is used, the roll having the profile and size shown in FIG. 4 as the edge bend roll, and the size shown in FIGS. 5 and 7 (φ ₂ = 300 mm, outside as the large-diameter side roll. A roll having a diameter ratio φ ₂ / φ ₁ = 46) and a bottom roll having an outer diameter of 62 mm arranged 10 mm offset on the line entry side was used. In addition, pipes were also made using rolls arranged 12 mm, 14 mm, 15 mm, 16 mm, 18 mm, and 20 mm offset on the line entry side. In addition, the fin roll was arrange | positioned only above the large diameter side roll.
The raw steel strip was passed through under the condition that the line speed was 4 m / min, and the fiber tube was welded on the squeeze roll under the conditions of an output of about 900 W and a beam diameter of 0.6 mm to produce a welded tube.

Example 2;
Similarly, using the line introduced in Fig. 3, so that a welded tube with an outer diameter of φ3.7 mm (φ ₁ ) can be obtained from a stainless steel strip with a thickness of 0.3 mm having a 16.5Cr-Ti-LCN composition, using an edge bend roll of 100 mm in diameter, phi ₂ is 100 mm, the large-diameter side roll 300 mm (outer diameter ratio _{φ 2 / φ 1 = 27,81)} , the roll offset arranged a bottom roll having an outer diameter of 62mm to the line entry side A welded tube was manufactured under the conditions of a line speed of 4 m / min, a fiber laser output of about 500 W, and a beam diameter of 0.6 mm.
In this case as well, seven types of pipes using rolls with 10 mm offset on the line entry side and rolls with 12 mm, 14 mm, 15 mm, 16 mm, 18 mm, and 20 mm offset are all located above the large-diameter side roll. Only fin rolls are placed on the top.

Example 3;
We will also introduce an example of manufacturing a welded pipe with an outer diameter of φ6.5 mm (φ ₁ ) using a 0.3 mm thick stainless steel strip with the same 16.5Cr-Ti-LCN composition.
As production lines, edge bend rolls having the same shape and size as those introduced in Example 1 above, large-diameter side rolls, and bottom rolls arranged offset on the line entry side were used.
In this example, 7 types of pipe making using 5mm offset rolls on the line entry side and 7mm, 10mm, 12mm, 15mm, 18mm, 20mm offset rolls, all above the large diameter side rolls. In addition, a fin roll having a pressing surface with a radius of curvature of 5 mm and 10 mm in FIG. 13 was also arranged in front of the squeeze roll immediately before the squeeze roll for a total of 14 types of pipe making.
Then, the steel strip was passed through under the condition that the line speed was 10 m / min, and a fiber tube was welded on the squeeze roll under the conditions of an output of about 1500 W and a beam diameter of 0.6 mm to produce a welded tube.
Although each of the above manufacturing conditions was manufactured without lubrication, a large-diameter side roll having an outer diameter ratio of 10 or more was used, and thus a metal tube having a good cross-sectional shape was obtained under any conditions.

Claims (14)

A roll stand having a pair of left and right side rolls, wherein an outer diameter ratio φ ₂ / φ _{1 of} an outer diameter φ ₂ of the roll formed with respect to an outer diameter φ _{1 of} a pipe formed as the pair of side rolls is Using a roll stand using a large-diameter side roll designed to be 10 or more, after forming a metal strip into a cylindrical shape through the roll stand of a single stand, weld the butt portion of the metal strip edge A method of manufacturing a small-diameter metal tube, characterized by joining. The manufacturing method of the small diameter metal tube of Claim 1 using the large diameter side roll designed so that outer diameter ratio (phi) ₂ / (phi) ₁ may be 25 or more.   The manufacturing method of the small diameter metal tube of Claim 1 or 2 which passes a roll stand, after bending a metal strip edge with an edge bend roll stand.   The production of the small-diameter metal tube according to any one of claims 1 to 3, wherein the roll stand to be used is a three-way roll type roll stand in which a bottom roll is disposed below a pair of left and right side rolls. Method.   The manufacturing method of the small diameter metal tube of Claim 4 which uses the roll stand of a four-way roll system by which a fin roll is further arrange | positioned above between a pair of right and left side rolls as a roll stand to be used.   Furthermore, the manufacturing method of the small diameter metal pipe of Claim 5 which arrange | positions a fin roll also in front upper side of the squeeze roll in which welding joining is performed, and suppresses generation | occurrence | production of a twist.   As a fin roll arranged just above the squeeze roll, a fin roll having a pressing surface having a shape with a radius of curvature greater than the radius of the tube to be obtained is used to press the steel strip edge. 6. The method for producing a small-diameter metal pipe according to claim 5, wherein the shape of the abutting portion is corrected to make the pipe. A roll stand having a pair of left and right side rolls, wherein an outer diameter ratio φ ₂ / φ _{1 of} an outer diameter φ ₂ of the roll formed with respect to an outer diameter φ _{1 of} a pipe formed as the pair of side rolls is A small-diameter characterized by comprising one stand of a roll stand in which a large-diameter side roll designed to be 10 or more is used, and a squeeze roll and welding equipment arranged on the downstream side of the roll stand. Metal tube manufacturing equipment. The apparatus for producing a small-diameter metal tube according to claim 8, wherein a large-diameter side roll designed so that the outer diameter ratio φ ₂ / φ ₁ is 25 or more is used.   The apparatus for producing a small-diameter metal tube according to claim 8 or 9, wherein an edge bend roll stand is disposed upstream of the roll stand.   11. The apparatus for producing a small-diameter metal tube according to claim 8, wherein the roll stand is a three-way roll type roll stand in which a bottom roll is disposed below a pair of left and right side rolls.   12. The apparatus for producing a small-diameter metal tube according to claim 11, wherein the roll stand is a four-way roll type roll stand in which a fin roll is further disposed above a pair of left and right side rolls.   Furthermore, the manufacturing apparatus of the small diameter metal pipe of Claim 12 by which the fin roll is arrange | positioned also just before the squeeze roll in which welding joining is performed.   The small-diameter metal according to claim 13, wherein the fin roll disposed immediately above the squeeze roll includes a fin and a pressing surface having a radius of curvature larger than the radius of the tube to be obtained. Pipe manufacturing equipment.

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