JPS603995A - Production of large-diameter welded steel pipe - Google Patents

Abstract

PURPOSE:To obtain a large-diameter welded steel pipe having a satisfactory size correcting effect and high working accuracy by relieving the residual stress generated in the weld zone and near the same after inside and outside normal welding of the steel pipe then expanding the pipe. CONSTITUTION:A steel plate is formed to a tubular body and the joint part thereof is subjected to tack welding and inside and outside normal welding. The steel pipe 5 after the normal welding is passed through a device for relieving residual stress in the weld zone consisting of a roll stand 2, a boom stand, etc. and is directly rolled by an outside bead rolling roll 21, an inside bead rolling roll 31, etc. to relieve the residual stress generated in the weld zone and near the same by plastic working. The pipe is then expanded. The large-diameter welded steel pipe of which the out of roundness in the axial line direction and the out of roundness in the circumferential direction are corrected within a prescribed size range is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates residual stress in the welded part of pipe-making material due to plastic working V in the UOE pipe-making process of large-diameter welded steel pipes,
The present invention relates to a method for manufacturing a large-diameter welded steel pipe in which the straightness in the axial direction and the circularity in the circumferential direction are corrected within a predetermined dimensional range.

Immediately after conventional large-diameter welded steel pipes are manufactured, most of them suffer from axial bending (A) or (B) or circular deformation (C) in the circumferential direction, as shown in Figure 1. is occurring.

The cause of this deformation is the non-uniform distribution of residual i-stress due to plastic deformation generated during UO press forming and thermal stress generated during welding.

Tube expansion is performed to remove this unevenly distributed residual stress and correct deformation.

For tube types where this residual stress is particularly problematic, an appropriate heat treatment is further applied.

For example, a steel pipe after welding is damaged by the thermal stress of welding as shown in Figure 1 (
As shown in A), it curves toward the bead and has a vertically elliptical shape. When this is corrected by conventional pipe expansion, the circumferential length of the steel pipe increases and it contracts in the axial direction. However, since the weld bead is stronger and thicker than other parts, it is less susceptible to deformation due to pipe expansion. Therefore, if the degree of tube expansion (tube expansion rate) is increased sequentially, the shape as shown in FIG. 1 (B) or (C) will occur.

The conventional pipe expansion method involves (1^i) releasing water pressure inside the pipe,
b) There is a hydraulic pipe expansion method and a mechanical pipe expansion method in which a plug divided into several parts is inserted into the inner surface of the pipe and expanded inside the pipe.

Expansion processing of large diameter welded 11.1 pipes is originally based on the product's if.
This is done in order to keep the +/degree, maJ'' method, etc. within a predetermined range according to standards and customer requests.

In recent years, the environment in which steel pipes are used has tended to be operated at high pressures and in highly corrosive environments. As a result, products have become stronger and thicker, but the straightening capacity of tube expansion equipment is insufficient, and there is a need to increase the capacity of tube expansion machines and make large investments.

Although residual stress can be removed by appropriate heat treatment, there are problems such as deformation of the steel pipe due to thermal expansion and heat treatment efficiency.

Therefore, an object of the present invention is to provide a method for manufacturing a large-diameter welded steel pipe with high processing accuracy and sufficient dimensional correction effect even for large-diameter welded steel pipes with high strength and thick walls.

The method of the present invention is characterized in that, in the UOE pipe manufacturing process for large-diameter welded steel pipes, after welding the inner and outer surfaces of the steel pipe, residual stress generated in the weld and its vicinity is removed by plastic working.

FIG. 2 shows the steps of the method for manufacturing large-diameter welded steel pipes of the present invention. The feature of the method of the present invention is that a welding part residual stress removal processing step is provided instead of the conventional tube expansion step VC. All other processes are the same as the conventional process.
The explanation will be omitted.

In this welding part residual stress removal process, residual stress in the welding part is removed by directly rolling it with a welding part caliper roll. The reason for using Kariba rolls is that one of the characteristics of roll rolling is that strong rolling is easy.
and that it can be rolled down continuously.

Next, with reference to FIGS. 3 to 5, an example of an apparatus for carrying out a welding part residual stress removal process will be described.

FIG. 3 is a side view of the device, and FIG. 4 is a side view of the device, and FIG.
1fii figure. As shown in FIG. 3, the device 1 is made up of a roll stand 2 and a boom stand 3.

The roll stand 2 includes an outer bead rolling roll 21, a reduction adjustment mechanism 22, a first drive mechanism 23, a conveyance roller 24,
It is made up of a second drive mechanism 25. The boom stand 3 has an inner bead rolling roll 31 and a guide roller 3.
2, a boom 33, a link mechanism 34 (Fig. 5), a lifting mechanism 35, and a hydraulic cylinder 36.

The roll stand 2 is a 0 steel pipe that moves a large diameter welded steel pipe 5 supported on a support roller 4 in the direction of an arrow 51 or 52 by sandwiching the large diameter welded steel pipe 5 with an external bead rolling roll 21 and a conveying roller 24. 5 is transported with the weld bead 53 facing upward.

The outer bead rolling roll 21 is supported by a reduction adjustment mechanism 22 to adjust its position in the vertical direction, and is connected to a first drive mechanism 23 to be rotationally driven. On the other hand, the conveyance roller 24 is connected to a second drive mechanism 25 and rotationally driven.

The boom stand 3 connects one end of the boom 33 to the lifting mechanism 35.
The other end of the boom 33, that is, the free end, is placed inside the steel pipe 5. A guide roller 32 is installed at the bottom of the other end of the boom 33.
is rotatably attached to the other end of the boom 33, and an inner bead rolling roll 31 is rotatably attached to the upper part of the other end of the boom 33 through a link (34).Link mechanism 34
is connected to the piston rod (not shown) of the hydraulic cylinder 36, and the hydraulic ring 36 is connected to the piston rod (not shown).
Therefore, as shown in FIG. 5VC, the inner bead rolling roll 31 is raised and lowered with respect to the boot 1.33.

Next, I would like to briefly explain the operation of the heavy armor f-1. Firstly, the steel pipe 5 is driven by a motor (not shown) V (therefore, the rear end is connected to the roll stand 2 by the support roller 4).
pie in the direction of arrow 51 until passing II]1. will be sent. At this time, the outer bead rolling roll 21 is F"
[It is pulled up by the lower mechanism 22 at a position I where it does not come into contact with the steel pipe 5.] In addition, the inner bead rolling roll 31
is pulled backward by the hydraulic cylinder 36F and is not in contact with the inner surface of the steel pipe 5 (Fig.
). Next, as shown in FIG. 5(B), the inner bead rolling roll 31 is raised by the hydraulic cylinder 36 and brought into pressure contact with the inner bead 1 of the steel pipe 5. At the same time, the outer bead rolling roll 21 is also lowered by the rolling down mechanism 221 to the position where the required downstream roll 11) is carried out.

The first and second drive mechanisms 23 and 25 are operated to move the steel pipe 5 in the direction of arrow 52. At this time, the circumferential speeds of the outer bead rolling roll 21, guide roller 32, and support roller 4 are controlled to be the same. In this way, the welded head 53 of the steel pipe 5 is rolled.

Outer diameter 40G, 4m1X wall thickness 450mm (equivalent to X 770)
Welded steel pipe with outer diameter 406.4+++m x wall thickness 5.0
Table 1 shows the results of the method of the present invention and the conventional method for welded steel pipes of Dragon (equivalent to 5L-B). The residual stress in the axial direction at the center of the bead is reliably reduced by the method of the present invention.

FIGS. 6 and 7 show the results of correcting the bending and straightness of a welded copper tube with an outer diameter of 406.4 mm and a wall thickness of 450 mm using the method of the present invention.

As is clear from the explanation above in Table 1, according to Method 1 of the present invention, the processing range is narrow, so it is possible to downsize the equipment, and it does not affect the strength of the material in any way.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a modified example of a single large-diameter welded pipe. FIG. 2 is a process explanatory diagram for explaining the present invention in detail. FIG. 3 is a side view of an apparatus that performs a welding part residual stress removal process. FIG. 4 is a front view of FIG. 3. FIG. 5 is a longitudinal sectional view of a part of the apparatus not shown in FIG. Figure gPJ6 is a 1' graph showing the degree of elongation at which bending occurs as a result of implementing the method of the present invention. FIG. 7 is a graph showing the incidence of roundness as a result of implementing the method of the present invention. 2: Roll stand 21: External bead rolling roll 22: Downstream regulator 174I 23: First drive groove 24. -21 25- Second drive mechanism 3: Poom stand 31: Internal bead rolling roll 32 guide roller 33: Poom 34: Link mechanism iη 35: Lifting mechanism 36: Hydraulic cylinder 4: Support roller 5: Steel pipe patent application Person Sumitomo Metal Industries, Ltd. (B) 0 5 70 75 20 25

Claims (1)

[Claims] A method for manufacturing a large diameter welded steel pipe, in which a steel plate is formed into a tubular body, the joints of the tubular body are temporarily welded, the inner and outer surfaces of the joint are welded, and then the pipe is expanded. A method for manufacturing a large-diameter welded steel pipe, which comprises performing processing to remove residual stress over the entire length of the welded portion after final welding of the inner and outer surfaces of the pipe.