JPS6323857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing rectangular ERW steel pipes using a cold draw roll forming device and a butt seam welding method, which is a method for efficiently and inexpensively manufacturing long rectangular steel pipes. I will provide a.

Conventionally, as shown in FIG. 4a, a steel strip is roll-formed into a substantially rectangular cross section 16, and as shown in FIG. 4b, it is squeezed with a squeeze roll 17 to form a joint surface 18.
Square electric resistance welded steel pipes are manufactured by butting and electric resistance sewing, but if the square shape before the electric resistance welding process is incomplete, there may be discrepancies on the joint surface 18,
Misalignment occurs and the electrical stitching becomes defective. To avoid this, it is better to make the square shape accurate, but this requires a precision roll group. The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a method for manufacturing rectangular electric resistance welded steel pipes that has a simple roll configuration and allows accurate butting of joint surfaces of the steel pipes.

An apparatus used in an embodiment of the present invention will be described below. In Fig. 1, A is a cold drawing roll forming device, 1, 2, 3, 4, 5 are curved roll parts,
Reference numerals 6, 7, and 8 are squeeze roll parts, and 10 is a drawing device that grips and draws out the tip of the steel strip. B is a resistance welding machine equipped with a rotating electrode 11 as shown in FIG. To manufacture a rectangular electric resistance welded steel pipe using the above-described apparatus, first, a steel strip having a width narrower than that of the steel strip is connected to the tip of the steel strip 13 pulled out from the coil 12;
Further, a wire rod is connected to the tip of the narrow steel strip, and the wire rod is first introduced between the rolls of the forming device A as a pilot, and the wire rod is pulled out by being gripped by the drawing device 10, and then the wire rod is pulled out from the narrow steel strip. and finally, grasp and pull out the tip of the steel strip 13. This steel strip 1
As shown in FIG.
1b to form an arcuate cross-section from both sides, and then, as shown in FIG. The rolls 3a, 3b, 3b of the bending roll section 3 are bent into a circular arc shape, and as shown in FIG.
By giving an arcuate shape to the intermediate portion, the steel strip 13 as a whole is formed into a roughly semicircular shape. The steel strip 13 bent in this way reaches the bending roll part 4 as shown in FIG.
It is lightly curved into an F-shape. Next, as shown in FIG. 2e, the roll 5
a, 5b, 5b, the lower corner part 1 of the square
5 and 15 are slightly bent into an F-shape. More than a
The three rolls used in steps from to e are used to bend the steel strip by making point contact with both sides of the steel strip, so each roller should be small and highly accurate. There is no need to use it. The second mentioned above
The steel strip bent as shown in FIG.
b and 6b, the curved surfaces excluding the corner portions 14 and 15 are butted in a quasi-circular shape with a large radius of curvature at the portion corresponding to the four sides shown in FIG. 2 f, a small radius of curvature at the corner portion, and a slightly square cross section. The pieces are squeezed together with their mouths open. And further squeeze roll part 7
As shown in FIG. 2g, the abutting piece is held tightly by the squeeze rolls 7a, 7a, 7b, and 7b, and is pressed toward the center of the tube by the arcuate inner surface of the upper squeeze roll 7a. The joint surfaces are brought together and pressed together, and as shown in Fig. 3, the seam part 1
6 is brought into contact with the rotating electrode 11 of the anti-welding machine B, and the seam portion 16 is welded 16a. As shown in FIG. 2h, the pseudo-circular tube 13a sewn in this way is shaped into a square rectangular shape by the squeeze rolls 8a, 8a, 8b, and 8b, which create a square hugging space. It is formed into a steel pipe 13b and drawn out.

Note that when forming a steel strip with a pseudo-circular cross section, the corner portions 14 and 15 are first formed into a V-shape, and then
The four sides may be curved into an arc shape.

The method of the present invention is as described above, in which the steel strip drawn out from the coil is first formed into a steel pipe with a pseudo-circular cross section by the preceding roll of a cold drawing roll forming device, and the seam portion is electrically sewn. Since it is formed into a square steel pipe using the squeeze roll at the final stage, a long square steel pipe can be efficiently obtained in one manufacturing operation. In this case, the abutting piece is pressed against the arcuate inner surface of the squeeze roll toward the center of the tube and slides, and the joining surfaces are precisely aligned and pressed tightly. In addition, when forming a curve before a pseudo-circular cross section, each part is pressed little by little. Since it is only necessary to curve it into a circular arc shape, the rolls used need only be small and of the three-point contact type, which has the advantage that the precision of the curved rolls does not have to be good.

[Brief explanation of drawings]

Fig. 1 is a simplified side view of a cold draw roll forming apparatus used in the method of the present invention, Fig. 2 a, b, c, d,
e, f, g, h are process explanatory diagrams when forming a steel strip into a square steel pipe using the same device as above, Figure 3 is an enlarged perspective view of the main part, and Figures 4 a and b are manufacturing steps of a conventional example. FIG. In the figure, A...cold draw roll forming device, 2...
...Resistance welding machine, 1, 2, 3, 4, 5... Curved roll section, 6, 7, 8... Squeeze roll section, 10...
... Strip steel drawing device, 11... Rotating electrode, 12...
... Steel band coil, 13 ... Steel band, 13a ... Pseudo circular tube, 13b ... Square steel pipe, 14, 15 ... Corner part, 16 ... Seam part, 16a ... Seam welded part.

Claims (1)

[Claims] 1 Point contact is made at one point on the inside and two points on the outside by a cold drawing roll forming device that shapes the steel strip by gripping the tip of the steel strip introduced into a series of rolls and forcibly pulling it out. While bending the steel strip into an arcuate cross-section using three rolls, the radius of curvature at the four sides is large and the radius of curvature at the corner is small.
The butt piece is formed into an unstitched tube with a pseudo-circular cross section that maintains a slightly square shape with an open mouth, and the joint surface is sealed while pressing the butt piece toward the center of the tube using a squeeze roll with an arcuate inner surface. After butt pressurizing and welding,
A method for producing a rectangular electric resistance welded steel pipe, further comprising passing the welded portion between squeeze rolls that squeeze the welded portion into a rectangular shape.