JPH11226868A - Method and device for smoothing inner surface of welded pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To press and crush the whole inner surface of a welded pipe including an inner surface welding bead, manufacture the welded pipe smoothing the inner surface with reduction in cost. SOLUTION: A metal band is molded continuously into a cylindrical shape, plate width direction both end parts are welded together, in the case of manufacturing a welded pipe 4, in a position where an inner surface welding bead 5 is placed in a high temperature condition of 200 deg. or more, the inner surface welding bead 5 is crushed by a pair of press rollers 10 in contact with the inner surface welding bead 5 and a base material part inner surface on the opposite side to the inner surface welding bead 5 and backup rollers 40 interposing the welded pipe 4 to confront the press rollers 10, and successively the whole inner surface of the welding pipe is crushed by an inner metal mold 20 in contact with the whole inner surface of the welding pipe 4 and an outer metal mold 50 in contact with an outer surface of the welding pipe 4. In this way, a burden of the metal mold is reduced, as a substitute for a seamless pipe, a pipe material usable for a cylinder or the like is manufactured by reducing a cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for smoothing an inner surface of a weld pipe including an inner weld bead by a pipe-making line.

[0002]

2. Description of the Related Art Generally, a welded pipe is manufactured by continuously forming a metal strip into a cylindrical shape by a pipe-forming machine and welding both ends in a sheet width direction. Since the both ends in the width direction are welded to the weld inside the welded pipe,
An inner surface weld bead is formed in which the weld metal hangs slightly. For this reason, the welded portion is thicker than the base metal plate by the thickness of the inner surface weld bead, and the inner surface is not smooth. In some applications, the welded pipe is used with an uneven inner pipe surface. However, a sanitary pipe, a heat exchanger, a pipe for a small boiler, a pipe for a cylinder, and the like, through which a fluid passes, require a smooth inner surface in order to ensure smooth operation in the pipe. For example, seamless steel pipes are conventionally used for small boiler piping and cylinders that require a smooth inner surface, but seamless steel pipes are an expensive material, so switching to welded pipes will reduce costs. Is being promoted. However, the use of a welded pipe as a replacement for a seamless steel pipe requires a smooth inner surface.

[0003] In order to smooth the inner surface of a welded pipe, first, it is necessary to smooth the inner surface weld bead, and various methods have been conventionally proposed. For example, JP-A-56-109
In Japanese Patent Publication No. 113, at the position of a sizing roll stand of a tube forming machine, a mandrel to which two rotatable upper and lower rollers are attached is arranged inside a welding pipe, and the inner surface welding bead is smoothed by the rollers and the sizing roll. . However, since the inner surface weld bead is crushed at a position far away from the welding position, cold working is required, and a very high pressure is required to crush the inner surface weld bead, and the roller and the sizing roll are likely to be overloaded. In Japanese Patent Application Laid-Open No. 62-246760, a pressing roll is disposed inside a welding pipe at the position of a squeeze roll, and the inner surface weld bead is crushed by the squeeze roll and the pressing roll. However, since the upper and lower surfaces of the squeeze roll are used for crushing, it is difficult for a sufficient crushing force to act on the inner surface weld bead. Further, JP-A-1-306
In Japanese Patent Publication No. 176, after the metal body before being formed into a tubular shape is heated and pressed at both ends in the plate width direction, the inner surface weld bead is scraped off with a shoe, and the inner surface of the welded portion is shaped with a pressure roll. However, since a preheating device, a shoe, a pressure roll, and the like are required, the equipment configuration is complicated, and the equipment cost is likely to be high.

[0004]

As described above, there are various problems in the conventional method for smoothing the inner surface weld bead. Therefore, the present inventors set the internal weld bead after welding to 200 ° C.
At the stage in the above high temperature range, the inside welding bead and the pressing roll contacting the inside of the base metal part facing the inside welding bead are inserted into the inside of the welding pipe, and the position where the pressing roll comes into contact with the inside of the welding pipe. A method of arranging a pair of backup rolls on the outside of the welded pipe and crushing the inner surface weld bead by a pressing roll and a pair of backup rolls was developed and filed as Japanese Patent Application No. 9-142370. According to the method of the prior application, there is no need to separately provide a heating device, and the inner surface weld bead can be crushed at a low pressure. When the inner surface of the welded tube that has crushed the inner surface weld bead is polished, a smooth flow is secured in a sanitary tube or the like through which various fluids flow.
However, when used as a substitute for a seamless steel pipe in applications such as cylinders, even if the inner weld bead is crushed at a low pressure, irregularities may occur on the inner surface of the pipe at the crushed position, and the pipe may be brought to the product stage. It is difficult to use a tube having an uneven inner surface for a cylinder or the like, and further smoothing is required.

[0005] As a method of smoothing not only the inner surface weld bead but also the entire inner surface of the pipe, an as-cast welded pipe is annealed and pickled, and then a lubricant is applied to the inner and outer surfaces of the pipe and dried, and the inner and outer surfaces of the pipe are dried. 2. Description of the Related Art There is known a core drawing process in which a core is pulled out with a contacted and pressed mold. However, a number of steps are required before the centering, and annealing and pickling are required again after the centering. As a result, the manufacturing cost is very high and the use of the product tube is restricted. The present invention is a further improvement of the method proposed in the prior application in order to solve such a problem. The present invention provides a supporting device equipped with a pressing roll for crushing an inner surface weld bead and an inner mold for crushing the inner surface of a welded pipe. The rod is placed inside the welding pipe, and the backup roll and the outer die are brought into contact with the outer surface of the welding pipe in opposition to the pressing roll and the inner die, so that the pressing roll, the backup roll, and the inner and outer dies are not excessively contacted. An object of the present invention is to crush the entire inner surface of a welded pipe without burden, and to manufacture a welded pipe having a smooth inner surface at low cost.

[0006]

In order to achieve the object, a method for smoothing the inner surface of a welded pipe according to the present invention is to continuously form a metal strip into a cylindrical shape and to weld both ends in the sheet width direction to form a welded pipe. When manufacturing the inner surface welding bead at a position where the inner surface welding bead is in a high temperature state of 200 ° C. or more, a pair of pressing rolls that contact the inner surface of the inner welding bead and the inner surface of the base material opposite to the inner surface welding bead, and a pressing roll sandwiching the welding pipe The inner surface of the weld bead is crushed by the backup roll opposite to the inner surface of the weld tube, and the inner mold that contacts the entire inner surface of the weld tube and the outer mold that contacts the outer surface of the weld tube continuously crush the entire inner surface of the weld tube. Features. Further, the inner surface smoothing device used in this method includes a pair of pressing rolls that come into contact with the inner surface welding bead and the inner surface of the base material portion on the side opposite to the inner surface welding bead, and faces the pressing roll across the welding pipe. The backup roll, the inner mold that contacts the entire inner surface of the welded pipe, the outer mold that contacts the outer surface of the welded pipe, and the pressing roll on the upper side in the running direction of the welded pipe, and the inner mold on the lower side. And a support rod inserted into the welding pipe from the upstream side. The amount of the support rod inserted into the welded pipe is adjusted so that the pressing roll comes into contact with the inner surface weld bead in a high temperature state of 200 ° C. or higher.

[0007]

When the inner weld bead is crushed at room temperature, a toe line is generated between the inner weld bead and the base material. By increasing the rolling reduction, the toe line becomes shallower, and the inner surface of the welded pipe becomes smoother. However, an increase in the amount of reduction not only increases the load on the pressing roll, but also causes a change in wall thickness near the inner surface weld bead. In this regard, as proposed in the prior application and Japanese Patent Application No. 9-142370, when the inner surface weld bead in a high temperature state of 200 ° C. or more is crushed, the toe line disappears with a lower load compared to the reduction at room temperature. Also, the amount of change in wall thickness under a load at which the toe line disappears is smaller than that at room temperature. However, only by crushing the inner surface weld bead, the thickness of the portion becomes thinner than the thickness of other portions. That is, the inner surface of the welded pipe has an uneven shape and is not completely smooth. Therefore, in the present invention, immediately after the inner weld bead is crushed by the pressing roll, the entire inner surface of the weld pipe is crushed, thereby eliminating the uneven shape caused by the crush of the inner weld bead and removing the inner surface of the weld pipe. The whole is smoothed. Immediately after crushing the inner weld bead, the entire inner surface of the welded pipe is crushed, which, combined with a small amount of wall thickness variation when crushing the inner weld bead, places an excessive burden on the inner and outer dies. The entire inner surface of the welded pipe is smoothed without application.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a smoothing device according to the present invention, for example, as shown in FIG. 1, a metal band 1 formed into a cylindrical shape is constrained by a squeeze roll 2 and both ends in the sheet width direction are welded. It is used in a pipe making line which is welded by a torch 3 to form a welded pipe 4. In this smoothing device, a support rod 30 equipped with a pressing roll 10 and an inner mold 20 is inserted into the inside of a welding pipe 4 from an upstream side. The insertion length of the support rod 30 into the welding pipe 4 is adjusted so that the inner surface weld bead 5 (FIG. 7) in contact with the pressing roll 10 is in a high temperature range of 200 ° C. or higher.
The temperature of the inner surface welding bead 5 at the position where the inner surface welding bead 5 is in contact with the pressing roll 10 is set to 200 ° C. or higher in order to reduce the rolling force required to crush the inner surface welding bead 5. However, when the pressing roll 10 is pressed against the inner surface welding bead 5 having an excessively high temperature, the heat load applied to the pressing roll 10 increases. Therefore, it is preferable to set the upper limit temperature to 600 ° C.

As shown in FIG. 2, the press roll 10 has an upper roll 11u and a lower roll 11d as a pair. The shaft 11s of the upper roll 11u is pivotally supported by the upper roll holder 12u (FIG. 3A), and the bolt 14u inserted into the bolt insertion hole 13u of the upper roll holder 12u is screwed into the bolt hole 31 of the support rod 30, thereby supporting the support rod 30.
, The upper roll 11u is rotatably mounted. The lower roll 11d is also rotatably mounted on the support bar 30 via a similar lower roll holder 12d. As the upper roll 11u and the lower roll 11d, the inner weld bead 5 of the welding pipe 4 is used.
A barrel-shaped roll (FIG. 3b), a spherical roll (FIG. 3c), or the like having a convex crown on the peripheral surface pressed against is used.

The upper roll 11u and the lower roll 11d mounted on the support rod 30 partially protrude from the opposite side surface of the support rod 30, as shown in FIG. 2, and are pressed against the opposing inner surfaces of the welding pipe 4. . Depending on the size of the welded pipe 4 to be manufactured, it is necessary to adjust the distance between the upper roll 11u and the lower roll 11d. In this case, the upper roll holder 12
u and the lower roll holder 12d, and spacers 15u and 16u of required thickness are interposed on the surface where the upper and lower roll holders 12u and 12d and the shoulder 32 of the support rod 30 oppose each other. Adjust the distance to 11d.

On the opposite side of the support rod 30, a mold holder 21 is fixed to the upper and lower roll holders 12u and 12d. The die holder 21 has a bolt hole 22 formed at an end thereof, and is integrated with the upper roll holder 12u by screwing a bolt 18u inserted into the bolt insertion hole 17u of the upper roll holder 12u into the bolt hole 22. Is done. Similarly, when integrated with the lower roll holder 12d, the mold holder 2
1 is firmly connected while being sandwiched between upper and lower roll holders 12u and 12d. Also in this case, a spacer 16u is interposed between the upper and lower roll holders 12u and 12d and the shoulder 23 of the mold holder 21 as necessary.

On the opposite side of the roll holders 12u and 12d, a male screw 24 is engraved on the peripheral surface of the mold holder 21. After the substantially cylindrical inner mold 20 is inserted into the mold holder 21, the fixing nut 25 is screwed into the male screw 24, so that the inner mold 20 is prevented from being removed from the mold holder 21. On the outer peripheral surface of the inner mold 20, a ring-shaped pressing portion 26 having an outer diameter capable of performing a required crushing process on the weld pipe 4 protrudes in a radial direction. As the inner mold 20, as shown in FIG. 4, molds having various shapes such as a cylindrical shape (a), a conical shape (b), a barrel shape (c), and a partially convex shape (d) are used. It is possible. In order to prevent the inner surface of the welded pipe 4 from being subjected to pressure flaws, the shape (c, d) having no corner on the side that first comes into contact with the inner surface is preferable.

A backup roll 40 and an outer mold 50 are arranged outside the welded pipe 4 at positions facing the pressing roll 10 and the inner mold 20 inserted into the welded pipe 4, respectively. The backup roll 40 is provided as a pair of rolls sandwiching the weld pipe 4. The backup roll 40 rotates while supporting the pressurized point of the weld pipe 4 pressurized from the inner side by the pressing roll 10 from the outside. As long as the pressing force necessary for smoothing No. 5 is given, the roll profile is not restricted. For example, a concave crown roll (FIG. 5A) or a flat roll (FIG. 5B) having a radius of curvature larger than the radius of the weld pipe 4 can be used as the backup roll 40.

The outer mold 50 applies a forming pressure from the outside to the weld pipe 4 shaped from the inside by the inner mold 20, and cooperates with the inner mold 20 to form a perfect circle of the weld pipe 4. Ensure the degree and straightness. The outer mold 50 is not limited in its shape as long as a molding pressure is applied to the outer surface of the welded pipe 4, and for example, as shown in FIG.
A mold (a) having a hollow 1 formed therein, a vertically or horizontally split mold (b) having a round groove, a three-way split mold (c) having a similar round groove, and the like are used. The long hole 51 and the round groove 52 correspond to the outer peripheral surface shape of the welded pipe 4, and rub the outer surface of the welded pipe 4 traveling downstream to adjust the outer shape of the welded pipe 4. Further, a rotatable forming roll (not shown) having an operation surface for shaping the outer surface of the welded pipe 4 while rolling the outer surface can also be used as the outer mold 50.

Press roll 10 and backup roll 40
The inner mold 20 and the outer mold 50 face each other with the weld pipe 4 interposed therebetween as shown in FIG. The upper roll 11u is pressed against the inner surface welding bead 5 of the welding pipe 4. Lower roll 11
d presses the inner surface of the weld pipe 4 located on the opposite side to the inner surface weld bead 5. Further, at positions where pressing force is applied by the upper and lower rolls 11u and 11d, the backup roll 4
0, 40 presses the welding pipe 4 from the outside. Therefore, when the inner weld bead 5 is crushed by the upper roll 11u, a pressing force is also applied to the inner surface on the opposite side of the weld pipe 4, so that irregular deformation of the weld pipe 4 due to the crush of the inner weld bead 5 is prevented. Is done. The position where the pressing force is applied by the upper and lower rolls 11u and 11d is as described in the prior application / Japanese Patent Application No. 9-142370.
As in the case of No. 2, the inner surface welding bead 5 is set in a region where the temperature is 200 ° C. or higher. Thereby, the pressing force required for crushing the inner surface weld bead 5 is greatly reduced.

Immediately after the inner weld bead 5 is crushed, the inner mold 20 contacts the entire inner surface of the weld pipe 4, the outer mold 50 contacts the outer surface, and the entire inner surface is crushed. As a result, the uneven shape caused by the crushing of the inner surface weld bead 5 is eliminated, the vicinity of the inner surface weld bead 5 and the base material have substantially the same thickness, and the welded pipe 4 whose inner surface is completely smoothed is obtained. Further, since the pressing force is applied to the weld pipe 4 in a high temperature state immediately after the inner welding bead 5 is crushed by the pressing roll 10, the welding is performed without applying an excessive load to the inner mold 20 and the outer mold 50. The smoothing of the tube 4 becomes possible. As a result, a welded pipe 4 having a smooth inner surface can be manufactured at low cost without the need for troublesome centering.

[0017]

[Example] SUS304 having a width of 239 mm and a thickness of 2 mm
A stainless steel strip was used as the metal strip 1, and a welded pipe 4 having an outer diameter of 76.3 mm and a wall thickness of 2 mm was produced at a line speed of 2.6 m / min during pipe making. When the inner welding bead 5 was not crushed by the pressing roll 10, the inner welding bead 5 having a height of 75 μm protruded from the welded portion into the weld pipe 4. Therefore, the support rod 30 equipped with the pressing roll 10 and the inner mold 20 was inserted into the welding pipe 4 from the upstream side. In order to press the pressing roll 10 against the inner surface welding bead 5 in the high temperature range of 200 ° C.,
The insertion length of the support rod 30 into the welding pipe 4 was adjusted so that the pressing roll 10 was positioned 1.7 m downstream from the welding position. The inner die 20 was set at a position 150 mm downstream from the center of the pressing roll 10. As the pressing roll 10, a barrel type having a radius of curvature of 36.1 mm and a width of 24 mm (FIG. 3)
b) Using the upper roll 11u and the lower roll 11d, the minimum distance between the outer peripheral surfaces of the upper roll 11u and the lower roll 11d is 73.3.
mm. A radius of curvature of 100 m is provided at a position facing the upper roll 11 u and the lower roll 11 d with the weld pipe 4 interposed therebetween.
m, a concave crown roll having a body length of 150 mm (FIG. 5 a) was disposed as a backup roll 40.

The inner mold 20 includes a ring-shaped pressing portion 2.
A mold with 6 (FIG. 4d) was used. The pressing portion 26 for crushing the inner surface of the weld pipe 4 was set to have an outer diameter of 72.4 mm in consideration of a change in wall thickness when the inner surface weld bead 5 was crushed. As the outer mold 50 facing the inner mold 20, an upper and lower two-part mold (FIG. 6B) having a semicircular round groove 52 with a curvature radius of 38.15 mm was used. When the inner weld bead 5 was crushed under the above conditions, the inner weld bead 5 was crushed.
The inner surface weld bead 5 could be crushed without generating a toe line between the base material and the base material. At this time, the load by the pressing roll 10 is 1.5 tf, the thickness change amount around the inner surface weld bead 5 is 0.04 mm, and the thickness change amount of the inner surface of the base material portion located on the side opposite to the inner surface weld bead 5 is 0.
01 mm. Furthermore, after the entire inner surface of the weld pipe 4 was crushed by the inner mold 20 and the outer mold 50, there was no difference in thickness between the periphery of the inner surface weld bead 5 and the base material. In this way, a welded pipe having an entirely smooth inner surface was produced.

[0019]

As described above, in the present invention, the entire inner surface of the welded pipe is smoothed immediately after crushing the inner surface weld bead having less deformation resistance by utilizing the high temperature state after welding. . Therefore, the inner weld bead is crushed at a low pressure without the need for a separate heating device and the toe line is not generated, and the wall thickness fluctuation caused by the crush of the inner weld bead is also eliminated. A welded pipe having a smooth inner surface is manufactured. In addition, the burden on the mold is reduced, and a pipe material used for cylinders and the like is provided at low cost as an alternative to the seamless pipe.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a welding pipe inner surface smoothing device according to the present invention.

FIG. 2 is an exploded view of a pressing roll for crushing an inner surface weld bead.

FIG. 3 is a sectional view (a) of a pressing roll mounted on a roll holder, a barrel type (b), and a spherical (c) pressing roll.

FIG. 4 shows several examples of inner mold profiles.

FIG. 5 shows a concave crown roll (a) and a flat roll (b) used as backup rolls which are arranged opposite to a pressing roll with a welded pipe interposed therebetween.

FIG. 6: Several examples of outer molds

FIG. 7 is a sectional view when the inner surface is crushed following crushing of the inner surface weld bead.

[Explanation of symbols]

1: Metal band 2: Squeeze roll 3: Welding torch 4: Weld tube 5: Inner surface weld bead 10: Pressing roll 11u: Upper roll 11d: Lower roll 12u: Upper roll holder 12d: Lower roll holder 13u, 17u: Bolt insertion hole 14u, 18u: Bolt 15u, 16u: Spacer 20: Inner die 21: Die holder 22: Bolt hole 23: Shoulder 24: Male screw 25: Fixing nut 26: Pressing part 30: Support rod 31: Bolt hole 32: Shoulder 40: Backup roll 50: Outer die 51: Slot 52: Round groove

Claims (2)

[Claims] When a metal strip is continuously formed into a cylindrical shape and both ends in the sheet width direction are welded to produce a welded tube, the inner surface weld bead is located at a high temperature of 200 ° C. or more. And, the inner surface weld bead is crushed by a pair of pressing rolls that contact the inner surface of the base material part on the opposite side to the inner surface welding bead and the backup roll that faces the pressing roll with the welding tube interposed therebetween, and subsequently contacts the entire inner surface of the welding tube. A method for smoothing the inner surface of a welded pipe, wherein the entire inner surface of the welded pipe is crushed by an inner die to be formed and an outer die contacting the outer surface of the welded pipe. 2. A pair of pressing rolls which are in contact with the inner surface welding bead and the inner surface of the base material opposite to the inner surface welding bead, a backup roll which faces the pressing roll with the welding tube interposed therebetween, and an entire inner surface of the welding tube. The inner mold that contacts the outer tube of the welded pipe, and the outer mold that contacts the outer surface of the welded pipe, the press roll is attached to the upper side in the running direction of the welded pipe, the inner mold is attached to the lower side, and inserted into the welded pipe from the upstream side An inner surface smoothing device for a welded pipe, comprising: a support rod to be inserted; and an insertion amount of the support rod to the welded pipe being adjusted so that the pressing roll comes into contact with the inner surface weld bead in a high temperature state of 200 ° C. or higher.