JPH01205822A - Forming method for welded pipe - Google Patents

Abstract

PURPOSE:To prevent torsion in a roll forming time and to prevent indentation flaw by forming parts except plate edges with an upper and a lower roll, a right and a left roll, then, forming the edges with guide rolls. CONSTITUTION:Outside rolls consist of these rolls 5, 4b and a locking roll 4a is arranged inside, these four rolls are arranged in the same section to make a group of forming devices and they are arranged at a forming middle stage. Then, two groups of guide rolls 6, 7 are arranged to compose forming allocation. In a forming device assembling upper/lower roll and right/left roll, a large forming allocation is given except plate edges and the forming of the plate edge part is allotted by the succeeding guide rolls. Since the guide roll is made larger in roll diameter than a general gauge, the indentation flaw is prevented. As a result, excellent effects are obtained for torsion in large thickness and for reduction of indentation flaws.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an electric resistance welded pipe, a forge welded pipe, or a welded pipe in which a strip is continuously KO roll-formed and welded by other welding methods. It is something.

[Conventional technology]

When manufacturing welded pipes, as shown in Fig. 6, conventionally, etch forming, center bending, etc. are performed using Nizu Lake Town Roll 1 in the first stage of forming, and side rolls and
It is manufactured by forming with an O-ru 2 called a cluster, cage, etc., and drawing and bending with a fin bath roll 3 in the latter stage of the forming. However, there are the following problems when molding these.

■　Molding using dimensional rolls and clusters.

When forming a comparatively thick strip 4 using rolls 2 called clusters or clusters, the forming reaction force becomes large, and even a slight imbalance on the left and right can cause large torsion. 1. As shown in FIG. 7, twisting becomes a problem.

■Cage molding.

Cage forming is a process in which small O-luns are closely lined up as shown in Fig. 8(a) K, for example, as disclosed in Japanese Patent Application Laid-open No. 61-42427, and even cage rolls do not twist when forming thick walls. However, since the cage has a large degree of freedom in setting the rolls, the rolls can be placed in appropriate positions as shown in Figure 8 (
Twisting can be prevented by appropriately setting the roll inclination θ in b). However, since cages are formed by closely arranging a large number of rolls, the diameter of the rolls must be small.

Therefore, if the wall thickness is large, the surface pressure will be high because the rolls are small, and there will be problems such as press scratches caused by the rolls.

[Problem to be solved by the invention]

When forming welded pipes, there is a problem in forming relatively thick pipes.

The object of the present invention is to provide a welded pipe forming method that prevents such twisting during roll forming and also prevents press damage.

[Means to solve the problem]

The present invention solves the above-mentioned problems, and the gist thereof is as follows:
In a welded pipe production line where strips are continuously roll-formed and welded, upper and lower o-ru and left and right rolls are used to form the strips, excluding the edges, followed by guide rolls to perform edge forming. This is a welded pipe forming method characterized by the following.

That is, in the present invention, in a line for continuous KO roll forming of strips, the middle stage of forming is carried out using a forming device having a set of upper and lower O-ru and left and right rolls, followed by guide rolls. As shown in FIG. 1, which shows an embodiment of the present invention, a forming device having a pair of upper and lower and left and right rolls 4 and 5 is used to ensure a large amount of forming, excluding the edge of the plate.
In addition, to prevent twisting, the following guide rolls 6.7 are also shaped mainly at the edge of the plate to ensure the effect of preventing twisting. In addition, the guide roll is smaller than a normal cage.
- By increasing the diameter of the ring, it is possible to prevent pressure damage.

The present inventors have discovered that the occurrence of twisting due to side rolls, etc.
It was discovered that twisting is likely to occur when the contact between the roll and the material begins at the edge and is not constrained at the center. One solution, therefore, is to equalize the onset of contact by increasing the number of roll divisions from the current normal two of the side rolls. In the present invention,
By placing three or more O-rules on the outer surface of the tube,
This makes the O-ru contact start uniform and prevents twisting. In a normal side roll 2, the roll diameter is 20 mm as shown in FIG.

On the other hand, when arranging three rollers on the outside as shown in Figure 9(b), the distance from the roller axis to the roll contour line is equalized, so the contact start of the rollers becomes uniform. and can therefore be prevented from twisting.

Further, since the shape of the material immediately before entering the hole has an edge due to the slitting back, contact occurs from the etch, and the start of contact at other portions in the circumferential direction is delayed. Therefore, another possible solution is to prevent twisting by changing the roll hole shape so that it does not touch the edges and avoiding contact from the etch.

In the present invention, even if it is a hole type that hits the etch as shown in the conventional 0-hole hole type shown in FIG. 2(a), the hole type is directly etched so that the edge does not get damaged as shown in FIG. 2(b). or large curvature etc.
Twisting can be prevented by forming a hole shape that avoids edges.

In order to increase the restraint and hold the material against the twisting force to prevent twisting, in addition to forming with three or more rollers on the outer surface, large rolls 4 are used on the inner surface as shown in Figure 3. ′
Twisting can be prevented by restraining the material with upper and lower O-rules. In the present invention, twisting is prevented by a combination of three or more outer rolls, a change in the hole shape of the outer roll, and a large inner restraint roll. In the one set of molding equipment described in detail so far, it is not finely divided into a large number of holes like a cage, so
Since the O-ru diameter can be made sufficiently large, there is no problem of pressure scratches.

Furthermore, the present inventors have found that the larger the amount of side roll molding, the greater the occurrence of twisting.

Therefore, by providing a forming distribution to the side roll or the guide roller placed after the above-mentioned set of forming devices and reducing the forming amount of the side rolls or the above-mentioned set of forming devices, twisting can be prevented. We have found a way to prevent this.

Since this guide roller does not have a large forming distribution, it does not cause twisting unlike the side roller, and by making the roll diameter larger than that of the cage, it is possible to prevent the occurrence of press scratches.

Note that when the present invention is applied to a thin material, edge buckling can be reduced for the following reasons.

In 0-roll forming, the material is brought into contact with the roll so that it wraps around the roll, so the edges of the material are greatly elongated as the material is repeatedly bent in the longitudinal direction. However, in the present invention, since the edges do not come into contact with each other at the 40-rule portion instead of the side roll, the etch elongation is kept low and edge buckling can be effectively prevented.

〔Example〕

FIG. 1 shows an outline of a molding apparatus used for molding in an example of the present invention. There are three O-ru on the outer surface (5, 4b), a restraining O-ru 4a is arranged on the inner surface, and these four O-ru are arranged in the same cross section to form one set of molding equipment, and the molding Placed in the middle. W: Board width RO: Radius of curvature of the final product R: Radius of curvature at the relevant position in the width direction The forming distribution in equation (1) of the above pair of forming devices is 020, and the forming amount of the edge of the plate is slurry tab. The molding distribution of the two-stage guide roll was only for the edge of the plate, and the size was 0.06×3. Figure 4 shows a molding distribution diagram. The horizontal axis of the figure shows the position in the plate width direction, and the vertical axis shows the molding curvature. When it is 0, the curvature is 0, that is, it is a flat plate, and when it is 1, it shows that the product has been molded to the curvature of the tube. As shown in FIG. 5, in the present invention, a forming device combining upper and lower rolls and left and right rolls is used to provide a thick forming distribution except for the edge of the plate, and a subsequent guide roller is used.

It is characterized by sharing the shaping of the plate edges. Guide 0-
The diameter of the tube was 1.2 times the tube diameter of the product. The roll diameter of the outer surface of the above-mentioned set of molding devices was 1.5 times the pipe diameter.

With this type of molding equipment, the outer diameter is 89.1 wm and the wall thickness is 8 m.
The steel pipe was formed. In the conventional molding method, the twist at the entry side of the fissipass was 60 to +60 degrees, whereas in the present invention, the twist was sufficiently small at 15 to +5 degrees. FIG. 5 representatively shows the measurement results of torsion.

Further, when steel pipes with the same outer diameter and wall thickness were formed using a cage, press marks were observed, but no press marks were observed using the method according to the present invention.

〔Effect of the invention〕

By employing the method of the present invention, it is effective in preventing twisting in thick-walled welded pipes such as electric resistance welded pipes and forge-welded pipes.

It also has a remarkable effect in reducing pressure damage caused by O-ru in thick walls.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a molding apparatus for carrying out the present invention, and FIGS. 2(a) and (b) are explanatory diagrams of a conventional hole mold and a 0-hole mold with a lower molding distribution of the plate edge. FIG. 3 is an explanatory diagram showing the contact situation between the side rolls and the plate edge in the forming apparatus according to the present invention, FIG. 4 is an explanatory diagram showing the forming distribution according to the present invention, and FIG. 5 is an explanatory diagram showing the actual measurement results of torsion in the example. Explanatory diagram,
Figure 6 is an explanatory diagram of the conventional molding method using side zero,
Figure 7 is an explanatory diagram of twisting in the same id O-ru, and Figure 8 (a
) and (b) are explanatory diagrams of the cage forming method and cage roll setting, and FIGS. 9(a) and (b) are explanatory diagrams showing the difference in the contact situation between the material and the roller depending on the number of roll divisions. 1... Plaque roll 2... Roll 3, which refers to side rolls, clusters, cages, etc. 4... Upper and lower rolls 5...
・Dimension roll 6,7...Guide O-ru Figure 1 Figure 3 Figure 4 Figure 5 Distance

Claims (1)

[Claims] In a welded pipe production line where strips are continuously roll-formed and welded, upper and lower rolls and left and right rolls are used to form the plates except for the edges, and then guide rolls are used to perform edge forming. Characteristic welded pipe forming method.