JPS61165226A - Forming device of electric welded pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of wavy edges on both edges of the material to be formed by performing a bending so that the locus surface of the straight line to connect both edges of the inside of each cross section in each bending can maintain a plane surface in case of bending the material to be formed in tubular shape. CONSTITUTION:The sectional shape of the metallic strip M is first made as F1 by the prescribed forming method in case of forming an electric welded pipe with bending in the width direction the metallic strip M of flat sectional shape. The sectional shape is formed with bending in the order of F2-F7 then. In this case the straight line to connect the both edge parts K1-K7 of the inside of each cross section of the material M to be formed is overlapped on the flower figure and the straight line is made to maintain in the plane surface or about plane face shape. The shaft center of the forming roll pair to form with bending pinching the material M to be formed from the both sides is made to be on the line of slope approx. of the locus line of the center part in the width direction of the material M to be formed. The electric welded pipe of high quality is produced thus at lower cast.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves passing a metal strip through a number of roll stands in its length direction, bending it in its width direction to form a tube, and then rolling the metal strip along its edges. The present invention relates to a device for creating electric resistance welded pipes by welding parts, and particularly to a device suitable for forming extremely thin-walled pipes.

[Conventional technology]

Generally, in the bending process in the manufacture of ERW pipes, the center part in the width direction of the material to be formed is kept at the same height throughout each bending process, as shown in the flower diagram in Figure 5. In other words, the core part is maintained on a straight line. There are many things to do.

However, this forming method has the disadvantage that both edges of the material to be formed are stretched and deformed in the length direction during the bending process, which is unique to the cold roll forming method, and as a result, green liquid is likely to occur as shown in Figure 8. There is. This phenomenon is particularly noticeable when bending thin-walled pipes9, and the green liquid causes misalignment of both edges, which has a serious adverse effect on the subsequent welding process, and even makes welding impossible.

Conventionally, as a forming method to alleviate this green liquid phenomenon, as shown in Fig. 7, the central part in the width direction of the material to be formed is bent in the direction opposite to the bending direction of the tube, and both edges are bent in the same direction. After bending, the reversely oriented central part is bent in the same direction as the intended pipe, or as shown in Figure 6, the central part in the width direction of the material to be formed is formed during the forming process. A downhill molding method was sometimes used in which the temperature was gradually lowered as the stages progressed.

[Problem that the invention seeks to solve]

However, even if the above-mentioned improved forming method is adopted, fine waves can still be completely prevented in thin-walled or ultra-thin-walled tubes with a ratio (%) of wall thickness to tube diameter of 2% to 1.5% or less. difficult or extremely difficult to weld;
These tubes were considered almost impossible to manufacture by cold roll forming.

The present invention provides a forming apparatus that is capable of producing thin or ultra-thin electric resistance welded tubes using an improved bending method.

[Means for solving problems]

The present invention is an electric resistance welded tube forming apparatus characterized in that the trajectory plane of a straight line connecting both edges in each cross section of a material to be formed is maintained in a flat or substantially flat shape.

[Function] First, the shape of the trajectory plane of a straight line connecting both edges in each cross section of the material to be formed according to the present invention will be described.

FIG. 1 is a flower diagram showing the process of forming a material to be formed in one embodiment using the apparatus of the present invention, in which the effects of the present invention have been demonstrated.

In this embodiment, the material to be formed is first formed from a band plate M having a flat cross-section, which is the raw material, by the forming method shown in FIG. F3
...Fil is bent and formed. During this time, the straight lines connecting both edges in each cross section of the material to be formed overlap on the flower diagram. In other words, the trajectory plane of this straight line is a plane.

The mechanism for preventing green liquor generation by the molding device button of the present invention has not yet been fully elucidated. However, when the molding states of the conventional and the above-mentioned embodiments of the present invention are determined on the flower diagram for each locus of a portion M slightly closer to the center from both edges, it is found that in the conventional molding state, FIGS. As shown in Figure 6, K
If the locus line k of has consistently detoured around the outside of the locus line m of M from the beginning of molding, and therefore K takes a larger path than M at each stage of molding, then the flower It can be seen from the diagram alone that there is a possibility that edge elongation may occur.

On the other hand, in the case of the example, as shown in the flower diagram of FIG. 1, the K and M points of the material are Fl, F2...
In Fl, 1. 2...F7 and Ml, M2...Ml, and the respective displacement amounts when deforming from the material to Fl are 1 and M-Ml for K-.
Comparing their sizes, we find that K~1<M−Ml
Similarly, it can be seen that 2<M-M2 for F2.

On the other hand, edge waves are thought to occur when the amount of elongation deformation at the edge is significantly larger than the amount of elongation deformation at the portion slightly closer to the center in the width direction (the amount of elongation deformation at the edge is at the center in the width direction). However, this edge elongation is caused by the fact that the material to be formed changes its cross-sectional shape immediately before the large size of the forming roll, especially at the edge. This is caused by the long travel distance i of the edge, and this amount of displacement increases when the cross-sectional shape of the edge is flat, that is, when the section modulus in the thickness direction is small.

Therefore, the green liquor generation prevention effect according to the present invention is achieved by suppressing the edge elongation caused by the sudden change in cross-sectional shape just before the roll hole mold, and by controlling the amount of edge displacement on the flower diagram when the edge is almost flat. This seems to be due to the compression force generation effect being offset by making the displacement amount smaller than that of the portion slightly closer to the center.

From the above considerations, it can be seen that in the present invention, the shape of the trajectory surface does not necessarily have to be flat, but can be changed from a flat shape to a curved shape within a range that produces a sufficient canceling effect to suppress fine waves. . Therefore, in the case of thin-walled pipes or soft metal materials that are prone to edge elongation, this trajectory plane should be directed downward in the case of the above embodiment, that is, toward the main body of the material to be formed (hereinafter, this direction will be referred to as the normal forming method). It can be seen that the curve should be downward (depending on the situation), and the opposite direction should be upward (depending on the situation).

FIG. 2 is a flower diagram when the material to be formed is not bent in the opposite direction. In this figure, K is the same as shown in Figure 1.
K-to 1<M~M1. Since there is a relationship of 2<M to M2, it is considered that the effects of the present invention occur.

In the present invention, it is desirable that the shape of the trajectory surface be maintained in a substantially planar shape from the initial stage of molding to the size of the molding roll stand immediately before the squeeze roll, etc.; The effect of the invention occurs particularly in the very early stages of molding, so that
There may be up to 6 stages up to IE 2 stage roll stand.

The apparatus of the present invention may be considered to be a form of forming apparatus that performs downhill forming. However, in conventional downhill forming such as electric resistance stitching, the widthwise central part of the material to be formed is 19. ``F is the dimension where it becomes a circular tube, and - through it, it decreases by a constant amount of y, and the maximum downhill is at the stage where it almost reaches the circular tube, and the amount is as shown in Figure 6. Dh-(1,0-0.5)XD(
D is the pipe diameter at the time of welding), which is usually about 0.8D in Dh. Therefore, since the amount of downhill per first stage of molding at the initial stage of molding is small, the locus of points as shown in Fig. 6 shows
This was a detour around the outside of the trajectory line m at point M.

In contrast, in the present invention, the trajectory surface is planar, and therefore, at a stage where the amount of rise is large, a much larger amount of downhill is provided than in the conventional downhill. This is the part M that is closer to the edge than K and slightly closer to the center than the edge.
The trajectory of 2m is completely different from that of conventional downhill molding.

Next, the relative positions of the pair of forming rolls that pinch and press the material to be formed from the front and back sides to form the bending material will be described. In the forming apparatus of the present invention, the trajectory surface of the material to be formed may be flat or may be curved downward, so that the center portion in the width direction of the material to be formed is the flower diagram in FIGS. 1 and 2, respectively. As can be seen from the diagram, there is a stage in which there is a very large displacement on the diagram.

For this reason, in the case of a normal cold roll forming apparatus, the ratio of the amount of displacement to the distance between the forming roll stands is large, and therefore the core part has a steep slope and gully, as shown in FIG. 4.

In addition, the contact points between each forming roll and the material to be formed differ greatly on the front and back sides in the thickness direction, and it may become impossible to apply sufficient rolling reduction.

Therefore, as shown in FIGS. 6A and 6B, for example, one person in a normal roll stand is tilted and fixed using the tilt table 2. In some cases, it may be necessary to use a roll stand 1B in which the bearings in the chock are placed on different centers.

〔Example〕

In addition to the flower molding shown in Figure 1, a cold roll forming machine with three stands of breakdown passes, a total of two stands of fin passes, and some side rolls was used to form the first breakdown stand as shown in Figure 7. Only the second breakdown stand was tilted as shown in FIG. 6A, and continuous forming welding was performed on the following materials. As a result, there were almost no edges in either case, resulting in beautiful welds.

(i) 5PCC equivalent material: Outer diameter 150tMRφ
× Plate thickness 1.0 (t/f) = 0.67%) (it) M alloy (tensile strength 31'CqN): Outer diameter 150
m+n (IIX plate thickness 2.0 and 1.5, 8.

self, fi=1.33chi and 1. 125mm diameter x 1.2m plate thickness (t, i) = 0, 96mm) 100mφ outer diameter x 1.2mm plate thickness (fan = 1.2%) [Effects of the invention] As stated above As described above, the forming apparatus of the present invention makes it possible to easily manufacture thin-walled or ultra-thin-walled electric resistance welded tubes, which has been difficult or impossible in the past. High quality pipes with wall thickness suitable for various fields of use are produced by cold forming.

This makes it possible to supply inexpensive electric resistance welded pipes and is extremely useful industrially.

[Brief explanation of drawings]

FIGS. 1 and 2 are flower diagrams of examples in which the effects of the apparatus of the present invention have been demonstrated and other embodiments of the present invention. Figure 3 is a diagram of an example in which the axis of the forming roll is shifted, Figure 4 is a diagram showing that it is necessary to shift the axis of the forming roll, and Figures 5 and 6 are of the conventional forming state. It is a flower diagram. FIG. 7 is an example of a cross-sectional shape when the central portion in the width direction is bent in the opposite direction, and FIG. 8 is a diagram illustrating green liquor. , 11゜茅, Fig. 3 (f3) (A) Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Claims] 1. A metal strip is passed through roll stands arranged in tandem in its length direction, bent in its width direction to form a tube, and then electrically welded between both edges. An apparatus for manufacturing an electric resistance welded tube, characterized in that the trajectory plane of a straight line connecting both edges in each cross section of a material to be formed is maintained in a flat or substantially flat shape. 2. The axial center of a pair of forming rolls for bending and pressing the material to be formed from the front and back sides thereof is arranged approximately on the normal line of the locus line of the central portion in the width direction of the material to be formed. A forming device for an electric resistance welded pipe according to scope 1.