JPS6056568B2 - Pipe making method and roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cold roll forming method in which a metal strip is passed through a number of roll stands in its longitudinal direction and bent in its width direction, particularly to a pipe forming method and rolls used therein.

When manufacturing electric resistance welded pipes etc. from metal strips, generally the material strips are bent in the same radius of curvature or with partially different radii of curvature, and in the same direction as the pipe bending direction for the entire width of the strip ( A method is adopted in which the material is bent and formed in a forward direction (hereinafter referred to as the forward direction), and as it passes through a roll stand, the radius of curvature is gradually reduced, and finally it is formed into a tubular shape with a seam.

In the case of large-diameter, thick-walled, high-tensile-strength pipes, etc., in the first to several roll stands, both edges of the strip are bent in the forward direction as described above, while the central portion of the strip is bent flat. A method is known in which a tube is formed by bending it directly or in the opposite direction to the intended bending direction, and then bending (unbending) the reversely bent portion in the forward direction. The main reason for adopting this type of forming method is that bending is difficult, and the edges and their vicinity, where the forming shape closely affects subsequent welding results, are close to perpendicular to the rolling direction of the forming rolls. By compressing and bending from the front and back, the tube is bent to the desired bending radius in order to apply sufficient bending force and to reduce the amount of bending with the fin bath roll. This is for molding. From this point of view, it is desirable to reversely bend the central portion. A method for unbending the reversely bent central portion will be explained with reference to the drawings.

As shown in FIG. 1A, the material to be formed is bent in the forward direction at both edges and its vicinity, and in the reverse direction at the center. (B) ■The entire area is bent back in parallel (B-1 condition)
and forward bend forming (C state). (Opening): Partially bent back and forward bent formed (B-2 state)
This part is enlarged and bent in the forward direction throughout the width direction (state C). (C): There are methods such as combining (B) and (Ex). The bending radius of the material to be formed, which is bent in the forward direction over the entire area, is gradually made smaller and constant, and finally it is formed into a tubular shape D having a seam e. However, conventionally, when unbending, the lateral position of the material to be formed within the roll hole mold becomes unstable, and as a result, the contact state of the edges becomes asymmetrical in the subsequent process such as fin bath rolls, and the shape of the edge surface is particularly affected. This can cause serious damage to welding results, etc.

In addition, various problems have occurred, such as twisting of the weld wire after welding. In other words, in Fig. 1 B-1, as the material is unbended, the width of the material other than the center is marked by arrows B and b.
It is necessary for the material to slide in the roll hole die in the ``direction'', but at this time, due to slight differences in the amount of reduction between the left and right sides of the rolls, the amount of sliding movement between the left and right sides is not equal, and the material to be formed is pushed to either the left or right side. In addition, in Fig. 1 B-2, the material to be formed, which is reversely bent in a convex manner at the center, is bent in the forward direction by the upper roll, which is convex in the downward direction, so that the material to be formed is biased to either the left or right. The object of the present invention is to provide a forming method that eliminates instability during unbending, and a roll used therein.

The present invention involves bending a metal strip in the forward direction at the center of its width, along with both edges and in the vicinity thereof, and in the opposite direction at the middle section between the center and both edges and the vicinity thereof. The pipe-making method and forward bending method are characterized in that the material to be formed is compressed and bent from the front and back sides.

According to the pipe-making method of the present invention, the center portion of the material to be formed is bent in the forward direction. The center part can be used as a guide surface to properly control the left and right positions of the subsequent roll stands, and when unbending and forward bending the left and right reverse bent parts of this center part, even if the material to be formed is Even if an unbalanced force acts in the left-right direction, movement in the width direction can be prevented, and instability can be prevented. In addition, the forward bending of both edges and the vicinity thereof is
By providing reverse bending parts on the sides of the central part, it is possible to perform bending in a state almost perpendicular to the rolling direction of the forming rolls, making it possible to apply strong forming force and obtain accurate bending shapes. This can have a positive effect on subsequent welding, etc. Further, since the pipe-making roll of the present invention bends and forms the forward bending portion by compressing it from the front and back, it is possible to accurately form the shape of the portion.

Next, examples of the pipe-making roll of the present invention will be described.

FIG. 2 is a partial sectional view of a cross section including both the upper and lower axes of the pipe-making roll of the present invention. The upper roll is made up of a center roll 3, spacers 5, 5, and edge rolls 4, 4 arranged concentrically in series, and is fixed to an upper roll shaft (not shown) with a key (not shown) to serve as a driving roll. The bolt/nut u is intended to facilitate roll replacement by integrating the upper roll. The lower roll 7 is an integral roll and is fixed to the lower roll shaft (not shown) by a key inserted into a key groove 7'' and driven. By employing a forming method in which the grooved roll holes provided corresponding to the rolls are compressed from the front and back and bent in the forward direction, the forward bending part can be formed into an accurate forming shape. The central part provides good results in welding in the subsequent process, and the central part plays the role of correctly guiding and holding the left and right positions of the material to be formed during subsequent forming on the stand.

In this example, the high surface pressure part that is compressed and bent from the front and back is bent on almost the same radius from the axis of both the upper and lower rolls, thereby suppressing slip due to the difference in circumferential speed and forming integrally rotationally driven rolls. is possible.

In addition, since there is no need to make the bending shape particularly accurate for the reverse bending portion, the bending shape is formed using the convex portion of the lower roll, thereby simplifying the roll. Of course, the pipe-making roll of the present invention is not limited to this embodiment, and the roll can be divided into parts to enable independent rotation. This method combines methods used for general rolls, such as arbitrarily selecting the radius from , and creating a part in the width direction of the material to be formed that is not bent and selecting this part as the dividing surface for roll division. It's okay.

Further, the pipe-making method of the present invention is not limited to the above embodiment of the pipe-making roll. As explained above, the present invention solves the instability associated with unbending, which is a drawback of the conventional pipe manufacturing method of reverse bending the central part, and is applicable to large diameter, thick wall, high tension pipes, etc. It has a remarkable effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a conventional method for unbending a reversely bent workpiece. FIG. 2 is a sectional view of an embodiment of the pipe-making roll of the present invention. A: Cross-sectional shape of the material to be formed by reverse bending the central part, B-
1; Cross-sectional shape when unbending in parallel across the entire area, B-2
: Cross-sectional shape when partially unbending, C; Cross-sectional shape during forward bending, D: Pipe cross-sectional shape, 1; Material to be formed, I
;Top roll, 7;Bottom roll.

Claims (1)

[Scope of Claims] 1. In a pipe-making method in which a metal strip is passed through a number of roll stands in the longitudinal direction and bent in the width direction, the metal strip is passed through a number of roll stands in the width direction, and the metal strip is formed at the center portion in the width direction, at both edges in the width direction, and The method includes the step of bending the central portion, the edges, and the intermediate portions of the central portion in the same direction as the intended bending of the tubular product, and bending the intermediate portions of the central portion, the edges, and the neighboring portions in the opposite direction to the bending of the tubular product. A pipe making method characterized by: 2. In breakdown rolls for pipe making, in which a metal strip is passed through a number of roll stands in the longitudinal direction and bent in the width direction, the metal strip is rolled at its center in the width direction, at both edges in the width direction, and in the vicinity thereof. The metal strip is compressed and bent from the front and back sides in the same direction as the bending of the intended tubular product, and the middle part between the center part in the width direction and both edges in the width direction and the parts in the vicinity thereof are A pipe-forming roll characterized by bending and forming in the opposite direction to the bending of the previous tubular product.