JPS62161427A - Breakdown roll for forming resistance welded pipe - Google Patents

Abstract

PURPOSE:To prevent the incorrect shape of a weld zone, etc. by providing the projecting part which supports both edge parts of the material to be formed from the outside on the upper roll and by forming the grooved face which plastically deforms the edge face as well. CONSTITUTION:The upper roll 16 is composed by side roll pieces 20, 20 and center roll piece 21 and fixed to a shaft 25 via a key spacer. A grooved part 21d is formed at the center part in the width direction on the center roll piece 21 and the truncated cone like projecting part 21b with apex half angle is formed on the edge face thereof as well. By this mechanism, the material 15 to be formed is held from the front and back in its center part in the width direction or formed by bending in the forward direction by compression. Moreover, the both edge parts are held by the side roll piece 20 and from the edge face pressed by the truncated cone projecting part 21b. Consequently, the prevention of the incorrect shape on weld zone and the improvement in the joint efficiency are enabled because the relaxation of the shortage of forming quantity and recovery of the edge face width size are made possible.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electric resistance welded tube forming breakdown roll.

[Conventional technology]

Recently, there has been a strong demand for electric resistance welded pipes to replace high-tensile, thick-walled pipes and the like in which seamless steel pipes have traditionally been used.

The biggest technical problem in manufacturing high-tension, thick-walled electric resistance welded pipes is the irregular shape of the welded part and the resulting reduction in welded joint efficiency.

FIG. 3 is an example of a flower formed into a thick-walled electric resistance welded tube using both edge forming and circular forming.

In other words, the material to be formed is bent at both edges with the radius of curvature of the product tube or a radius of curvature approximating it (edge forming), and the radius of curvature at the center is gradually reduced from a large radius to that of the product. (Circular forming) After the pipe is formed into a tubular shape, both sides are electrically welded to form an electric resistance welded pipe.

The main shape irregularities mentioned above occur during the breakdown pass and are shown in Figures 4A and B. B shows that the extreme parts of both edges are hardly bent and formed;
It shows that crushing occurs at 0 parts and 0 parts.

After welding, the welding pad on the outer periphery of the pipe is removed by cutting or grinding as shown by the broken line in Figure A, so that the welded part is thinned as the size increases. This thinned part is created after the deburring process, and the sizing process compresses the welded pipe from the entire outer periphery to adjust the outer diameter.The thinned part and the cross-sectional shape are somewhat alleviated and improved, but the amount of each is not enough,
Coupling efficiency is still low.

The W-bend method is a well-known molding method for reducing the shape defects of the edges of these molded materials. That is, as shown in FIG. 3 1 or FIG. 4 B, one edge portion is bent by bending the central portion in the width direction of the plate in the direction opposite to the bending direction of the intended circular tube. It is held close to perpendicular to the rolling direction of the forming rolls and bent. However, the effect is not sufficient.

[Problem that the invention seeks to solve]

The present invention is an electric resistance welding method that compensates for the thinning due to insufficient bending (Fig. 4A) and crushing (Fig. 4B) of the edge of the material to be formed, and achieves a more correct weld shape and high joint efficiency. The purpose is to provide a tube forming roll.

[Means for solving problems]

The present invention provides an ERW tube forming breakdown roll characterized in that the convex roll supports both edges of a material to be formed from the side that becomes the outer circumferential surface, and has a protrusion that presses the edge surface to plastically deform it. It is.

[Effect]

As shown in FIGS. 5A and 5B in the conventional forming state, the breakdown rolls are disposed facing each other, such as upper and lower, and contact the molded materials 15a and 15b supplied therebetween with their front and back sides, respectively. 1 pair of rolls for rolling and bending
It consists of 6a engineering, 17a yu, 16b and 17b. As shown in Figure B, as the bending progresses, the distance between the two edges gradually decreases, so the upper roll L6b, which is one of the rolls that enters between the edges, has a width W is limited, and therefore the range and effect of the bending action on the material to be formed 15b is reduced.

Therefore, forming after a certain point continues with the fin pass roll shown in FIG.

The breakdown roll of the present invention improves the stress state of the edges of the material to be formed, thereby compensating for the crushing of both edges and the insufficient amount of bending.

〔Example〕

Next, the present invention will be described in detail based on drawings of embodiments to which the present invention is applied.

FIG. 1 is a sectional view of an embodiment of the present invention, in which the lower roll H
is not particularly different from the conventional breakdown roll, so the explanation will be omitted.

The upper roll plate consists of side roll pieces 20, 20 and a center roll piece 21, and is fixed to the upper roll shaft 25 using a key and a spacer. The center roll piece 21 has a hole-shaped part 21d similar to a conventional intermediate to final stage breakdown convex roll in the center part in the width direction, and has a truncated conical protrusion 21b with an apex half angle O on its end surface.

The material to be formed 15 is held at its center in the width direction from the front and back in the same manner as in the conventional breakdown path, or is compressed to bend the core in the forward direction, and both edges are
It is held by the hole-shaped surface of the side roll piece 20 from the side that becomes the outer peripheral surface, and is pressed by the truncated conical projection 21b from the edge surface. In the present invention, the edge surface of the material to be formed 15 can be compressed with a higher surface pressure than conventional fin pass rolls, and this allows the edge surface to undergo a rolling action, reducing the thickness of the edge to the inner diameter. 4A.
and B, respectively, to alleviate the insufficient amount of bending and to recover the edge surface width dimension reduced due to the crushing of the edge pole portion.

That is, since this roll is a breakdown roll, the apex half angle O of the truncated conical protrusion 21b of the central roll piece 21 of the present invention is smaller than the angle of the fin pass roll shown in FIG. Therefore, as shown in FIG. 1, with respect to the radius R from the roll axis of the protrusion 21b, the radius of uniform curvature Re of the conical surface of the protrusion is Re=R/cosθ, where 0 is small. Therefore, it is not very large compared to R. That is, the uniform radius of curvature Re' of the fin surface of the fin pass roll with which the edge surface of the material to be formed contacts (see Fig. 6)
Compared to this, the uniform radius of curvature Re of the protrusion 21b is small.

Therefore, the contact area between the protrusion 21b and the edge surface of the material to be formed 15 becomes smaller, the total rolling force decreases, and the stress distribution in the depth direction from the edge surface of the material to be formed becomes steeper. The rolling action will be limited to the shallowest part of the edge surface, ie the part where the thinning is greatest. This rolling action on the edge surface is caused by the uniform radius of curvature Re of the conventional fin pass roll.
' is large, so this effect was practically impossible to achieve. This compressive deformation of the edge surface extends to the inner periphery of the material to be formed, since the outer periphery of the material is held down.

In the present invention, since the apex half angle θ is small, the protrusion 2
Since the difference in radius from the roll axis of the portion of 1b in contact with the edge surface of the material to be formed 15 is small, damage caused by friction between the edge surface and both surfaces of the protrusion 21b due to the peripheral speed difference based on this radius difference is reduced.

Furthermore, according to the present invention, it is possible to prevent the meandering of the material to be formed, which conventionally occurred in the breakdown roll film, reducing the burden on the fin surface of the fin pass roll, and reducing damage such as wear and cracking. The effect of

In this example, the entire outer periphery of the edge of the material to be formed is held by the roll hole type, so there is no overhang in the outer radial direction, making it possible to apply strong pressure to the edge surface. A sufficient rolling effect can be provided. Furthermore, since each roll piece is integrated, the roll structure is simple.

FIG. 2 is a sectional view of another embodiment of the present invention.

This embodiment is an example applied to a small diameter pipe, and the shoulders of the lower roll 17' and side roll pieces 20', 20' are largely removed, and a relief part 22 is provided to prevent the occurrence of impressions due to mismatch between the upper and lower roll hole shapes. This was prevented.

〔Effect of the invention〕

As described above, the present invention is particularly effective in preventing irregular shapes of welded parts and the resulting reduction in joint efficiency in the manufacture of high-tension, thick-walled electric resistance welded pipes for oil country tubular goods, boiler tubes, etc. This will further promote the substitution of electric resistance welded pipes for these applications, which will have a great industrial effect.

Note that, although the above description has focused on thick-walled pipes, the present invention can also be applied to thin-walled pipes as is.

1 and 2 are cross-sectional views of breakdown rolls according to an embodiment of the present invention and other embodiments, respectively. Figure 4 is a diagram explaining the irregular shape of the welded part, A indicates the insufficient bending amount of the edge, B
5 is a diagram explaining the crushing by rolls, FIG.
The figure shows a normal fin pass roll.

Figure 5 A Procedural Amendment (Ki) Indication of Case O6-4-j 1986 Patent Application No. 1788 Name of Invention ERW Tube Forming Breakdown Roll Amendment Relationship with the case of a person who does No change)k
D A, 10 '1 Procedural amendment (voluntary) 61, tl, 19 Showa year, month, day

Claims (1)

[Claims] 1. In a pair of electric resistance welded tube forming breakdown rolls that bend and form a metal strip in the width direction while running in the longitudinal direction, the roll that contacts from the inner periphery of the center part in the width direction of the material to be formed is 1. A breakdown roll for forming an electric resistance welded tube, characterized by having a protrusion that supports both edges of a molded material from the outer periphery side and presses the edge surface to plastically deform it.