JPS61165225A - Forming device of electric welded pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of wavy edges on both ends of the material to be formed by including the stage to form with bending in the same direction as the aimed pipe around the both edge parts of the material to be formed and in the reverse direction the parts besides that and by keeping in a plane the locus surface of the straight line to connect both edges of the material to be formed during the formation. CONSTITUTION:The sectional shape of a strip plate M is bent as per F1 with bending so as to make the vicinity of both edge parts K of the strip M in the same direction to that of the aimed pipe and the parts excepting both edges parts in the reverse direction to that of the aimed pipe first in case of forming electric welded pipe with bending the strip M is flat sectional shape in the width direction. A bending is then performed in order so that the sectional shape of the strip M becomes as per F2-F7. In this formation, the locus surface of the straight line to connect both edge parts K1-K7 of the strip M is made to become plane or nearly in a plane shape. The generation of wavy edges on the edge part SK of the strip M is thus prevented and the electric welded pipe of high quality is produced at low 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 tubular shape, and then rolling the metal strip along its edges. The present invention relates to an apparatus for manufacturing an electric resistance welded tube that welds parts, and particularly to an apparatus suitable for forming extremely thin-walled tubes.

[Conventional technology]

Generally, in the bending process in the manufacture of ERW pipes, as shown in the flower diagram in FIG. It is often maintained in

However, in this forming method, 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.
As a result, there is a drawback that green liquor is easily generated as shown in FIG. This phenomenon is particularly noticeable when bending thin-walled pipes, and the green liquid causes misalignment of both edges, which has a serious adverse effect on the subsequent welding process, and even makes it impossible to weld.

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 center part is bent in the direction of the intended pipe, or as shown in Figure 6, the center part in the width direction of the material to be formed is bent during the forming process. A downhill molding method was sometimes used in which the temperature was lowered in successive stages.

[Problem that the invention seeks to solve]

However, even if the above-mentioned improved forming method is adopted, green liquid is still used for thin or extremely thin-walled pipes with a wall thickness to diameter ratio (t/D) of 2 inches to 1.5 inches or less. Unable to be completely prevented, 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 can manufacture thin or extremely thin electric resistance welded tubes using an improved bending method.

[Means for Solving the Problem] The present invention is a process of bending the vicinity of both edges of a material to be formed in the same direction as the target pipe, and bending the parts other than the vicinity of both edges in the opposite direction to the target pipe. This 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 the material to be formed is maintained in a flat or substantially flat shape.

[Effect]

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, to have a cross-sectional shape Fl by the forming method shown in FIG. 7, and then to have a cross-sectional shape F2. 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 locus plane of this straight line is a plane.

The mechanism for preventing green liquor generation by the molding apparatus of the present invention has not yet been fully elucidated. However, flower diagram, 3.

-H indicates the molding state of the conventional and present invention 10=r=Example,
When calculating the trajectories of both edges K and a portion M slightly closer to the center from both edges, it is found that in the conventional molding state, the 5th
As shown in Fig. 6, the movement of K.

The trace line k has consistently detoured around the outside of the trace line m of M from the beginning of molding, and therefore, K has a larger path distance than M at each stage of molding. Therefore, it can be seen that edge elongation may occur even when considered only from the flower diagram.

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 M
l, M2...Ml, and when the material is transformed into Fl, the respective displacement positions are 1 in K- and M~M1, and when comparing their sizes, 1<M- in K- Similarly, it can be seen that -2<M-M2 for F2.

On the other hand, green liquor is thought to occur when the amount of elongation and deformation at the edge is much larger than the amount of elongation and deformation at the portion slightly closer to the center in the width direction. When the amount of deformation is larger than that 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, especially at the edge, by a large distance just before the large forming roll, which lengthens the travel distance of the core. 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 effect of generating compressive force, which is offset by making the displacement amount slightly smaller than that of the portion closer to the center.

From the above considerations, 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 countervailing effect to suppress green liquor. I understand. Therefore, in the case of thin-walled pipes or soft metal materials that are prone to edge elongation,
Rather, this trajectory surface should be curved downward in the case of the above embodiment, toward the main body of the material to be thinned (hereinafter, this direction will be referred to as downward as in the case of a normal forming method, and the opposite direction will be referred to as upward). I understand that.

DETAILED DESCRIPTION OF THE INVENTION FIG. 2 is a flower diagram when the material to be formed is not bent in the opposite direction. Also in this figure, as shown in FIG. 1, -K 1 <M-M 1 , K-K 2 <M-M
Since there is a relationship of 2, it is considered that there is an effect of preventing the occurrence of edges due to the above-mentioned cancellation.

However, compared to the case where the center part of the material to be formed in the width direction is bent in the opposite direction to the target pipe, it is necessary to make the forward bending part of the edge part wider and have a large curvature. It is difficult to obtain a large section modulus. Therefore, as can be seen from the above discussion, the edges of the material to be formed are largely displaced just before the large-sized forming roll, and a thick outer edge elongation occurs due to the difference in travel distance.

In the present invention, the range in which the shape of the trajectory surface should be maintained in a substantially planar shape is preferably from the initial stage of forming to the forming roll stand immediately before the seam guide roll, etc.; The effect of the invention is that this occurs especially in the very early stages of forming, so the material, the first roll stand, the second stage
It is also possible to use three sizes in a corrugated 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 welding, the center part in the width direction of the material to be formed is reduced by the amount of - from the material stage until it becomes a round pipe, and the maximum downhill is the stage when the pipe has almost reached a circular shape, and the amount is as shown in Fig. 6, Dh = (1,0~0.5)XD (D is the pipe diameter at the time of welding), and usually 0. It is about 8D. Therefore, since the downhill amount of one forming step in the early stage of forming is small, the trajectory line of points detours around the outside of the trajectory line m of point M, as shown in Fig. 6. On the other hand, in the present invention, the trajectory surface is planar, so that at the stage where the amount of rise is large, the curve is 7.

Compared to conventional downhills, it provides a very large amount of downhill by -1. As a result, the trajectory k + m of the edge and the portion M slightly closer to the center than the edge becomes completely different from that obtained by 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 curved downward, so that the center portion in the width direction of the material to be formed is as shown in the flower diagram of FIG. , there is a stage where there is a very large displacement on the diagram. For this reason, in the case of normal cold roll forming equipment, the ratio of the amount of displacement to the distance between the forming roll stands is large, resulting in a steep slope at the core, as shown in Figure 4. The contact points will be significantly different on the front and back sides in the thickness direction, and it may not be possible to apply sufficient pressure. Therefore, Figure 6A.

As shown in B, for example, a normal roll stand 1A is fixed at a slope 1 to 8 using a slope table 2.

In some cases, it may be necessary to use a roll stand 1B with the bearings located on different sides within the roll stand.

〔Example〕

In addition to the flower molding shown in Figure 1, the first breakdown stand is molded as shown in Figure 7 using a cold roll forming machine with three stands of breakdown baths, a total of two stands of fin passes, and some side rolls. Only the second breakdown stand was tilted as shown in FIG. 3A, 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 compatible material: outer diameter 150mφ×
Plate thickness 1.0mm (/6=”-67%) (it) kL alloy (tensile strength 3 q-): Outer diameter 150
String φ x plate thickness 2.0 and 1.5 Haki = 1.53% and 1.0%) Outer diameter 125 Kasumi φ x plate thickness 1.2 system (Extension - 0.96 inch) Outer diameter 100 wI + + Iφ x Plate thickness 1.2m (,6=1゜2
%) [Effects of the Invention] As described above, the forming apparatus of the present invention easily makes it possible to manufacture thin-walled or ultra-thin-walled electric resistance welded pipes, which was previously difficult or impossible, and which was particularly necessary in the past. High-quality pipes made by cold-open molding are used to produce thick-walled pipes that can be used in a variety of applications.

This makes it possible to use inexpensive electric resistance stitching, etc., and is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a flower diagram of an example in which the effects of the apparatus of the present invention have been demonstrated and another embodiment of the present invention. FIG. 2 is a diagram showing that green liquor is likely to be generated because the center part in the width direction of the material to be formed is bent in the direction opposite to the intended tube. Fig. 3 is a diagram of an example in which the axis of the forming roll is shifted, Fig. 4 is a diagram showing that it is necessary to shift the axis of the forming roll, and Figs. 5 and 6 are flower diagrams of the conventional forming state. It is. 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.

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 an electric current is applied to weld the two edges thereof. The apparatus for manufacturing a sewn pipe includes the step of bending a portion near both edges of a material to be formed in the same direction as the intended tube, and bending a portion other than the portion near the both edges in the opposite direction to the tube, and An apparatus for forming an electric resistance welded pipe, characterized in that a trajectory plane of a straight line connecting both edges in each cross section of a fatigue forming material is maintained in a flat or substantially flat shape. 2. Claims characterized in that the axes of a pair of forming rolls for bending and pressing the material to be formed from the front and back sides thereof are disposed approximately on the normal line of the locus line of the central portion in the width direction of the material to be formed. 2. The electric resistance welded tube forming apparatus according to item 1.