JPS60124415A - Manufacture of welded pipe - Google Patents

Abstract

PURPOSE:To prevent generation of a bitten flaw, and to simplify a manufacturing process by rolling a pipe to a fixed diameter in a stage of the final side of a drawing process, in a manufacturing method of a welded pipe, having each process of forming, welding, drawing and cutting. CONSTITUTION:In a forming process, a heated skelp 1 is formed to a circular- arcuate shape by a forming roll 11 of a welding machine 10, and in a welding process, the edge of the skelp 1 is butted and welded by a welding roll 12, and in a drawing process, a welded pipe 2 is drawn and rolled to a size near a final product by an elliptical hole die of vertical rolls 13, 15... and horizontal rolls 14, 16..., also finished to the final produce size by a completely round hole die of horizontal rolls 22A, 24A and a vertical roll 23A, and in a cutting process, said pipe is cut to a prescribed length by a rotary hot saw 30. In this way, a welded pipe having no bitten flaw is obtained, and the manufacturing process is simplified.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a forge-welded pipe.

As shown in FIG. 1, in the conventional manufacturing method for forge-welded pipes, first, in the forming process, about 1,350
In the 0-order process, a skelp (steel strip) heated to ℃ is formed into an arc shape of about 270 degrees by a forming roll 11 as shown in FIG. In the forge welding process, the edges of the skeleton L formed into an arc shape are brought into contact with each other by the forge weld roll 12 as shown in FIG. Approximately 2z to 5z outer diameter drawing is applied and forge welding is performed. Next, in the drawing process, the second
Vertical rolls 13.15, 17.1 as shown in figure (C)
9.21.23 and the oval hole type of the horizontal rolls 14.16.18.20.22.24 as shown in Fig. 2(B), the forge welded tube 2 has an outer diameter reduction rate of approximately By adding I%-10% outer diameter reduction, the final product dimensions (outer diameter,
The material is sequentially reduced and rolled to a size close to that of the material (wall thickness).

Next, in a cutting step, the reduced-rolled tube 2 is cut into a predetermined length by a rotary hot saw 30.Next, in a sizing step, the cut tube 2 is cut into the first to third stands of the sizer 40. horizontal rolls 41. as shown in FIG.
43 and the perfect circular hole shape of the vertical roll 42 as shown in FIG. In addition to correcting edge deformities and nose curvature, it is also finished to the final product dimensions (outer diameter, wall thickness).

Note that the pipe 2 finished by the sizer 40 is transferred to a cooling bed 50.

However, in the above-mentioned conventional forge-welded pipe manufacturing method, when the tube 2 is cut by the rotary hot saw 30, the cracks generated at the cut end of the tube are removed during the subsequent sizing process. 43, causing jamming and flaws in the tube 2, reducing quality and walking performance. Further, the deformation of the tube end and the bending of the nose which occur when the tube 2 is cut by the rotary hot saw 30 do not cause quality problems, and correction by the sizer 40 is not particularly required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a forge-welded pipe that can prevent the occurrence of biting flaws and simplify the manufacturing process.

In order to achieve the above object, the present invention includes a forming process of forming a heated skelp into an arc shape, a forge welding process of abutting the edges of the skelp formed into an arc shape and forge welding it into a tubular shape, and @joining process. In a method for producing a forge-welded pipe, which includes a drawing step in which the reduced-rolled tube is sequentially reduced and rolled, and a cutting step in which the reduced-rolled tube is cut into a predetermined length, the tube is removed at the final stage of the drawing step. It is designed to be rolled to a fixed diameter.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a process diagram showing an embodiment of the present invention. That is, first, in the molding process, about 1.3
Skelp l heated to 50℃ is transferred to the first part of forge welding pipe making machine lO.
Forming roll 11 as shown in FIG. 4(A) located on the stand (same as forming roll 11 shown in FIG. 2(A))
Shape it into an arc shape of about 270 degrees.

Next, in the forge welding process, a forge weld roll 12 as shown in FIG.
(same as the forge welding roll 12 shown in FIG. 2(B)) to abut the edges of the skeleton 1 formed into an arc shape,
Forge welding is performed by adding an outer diameter reduction with an outer diameter reduction ratio of approximately 2z to 5χ.

Next, in the drawing process, vertical rolls 13, 15, 17, 19 as shown in FIG.
．． 21 (vertical rolls 13.15. shown in FIG. 2(C)).
17.19.21) and horizontal roll 14.16.18.20 as shown in FIG. 4(B) (horizontal roll 14.16.18.20 shown in FIG. 2(B)) The outer diameter reduction rate per stand is approximately I for the tube 2 which is forge welded using an elliptical hole type (approximately the same -)! - The outside diameter of the bow Oz is sequentially reduced and rolled to dimensions close to the final product dimensions (outside diameter, wall thickness), and the tubes are placed alternately in each of the 12th to 14th stands of the forge welding pipe making machine 10. The horizontal rolls 22A, 24A as shown in FIG. 4(D) and the vertical roll 23A as shown in FIG. Add outside diameter drawing to finish the final product dimensions (outside diameter, wall thickness).

Next, in the cutting process, the tube 2, which has been finished to the final product size, is cut into a predetermined length using a rotary hot saw 30. Note that the tube 2 cut by the rotary hot saw 30 is transferred to the cooling bed 50.

That is, in the present invention, forming,
In addition to forge welding and drawing, it also has the function of a constant diameter (sizer), and the final stand of the forge welding pipe manufacturing machine 1O finishes the pipe to the final product dimensions, making it possible to omit the conventional sizer 40. That is, in order to provide the final stand of the forge welding pipe making machine IO and several stands upstream thereof with the functions provided by the conventional sizer 40, the roll hole shape was changed from an ellipse to a perfect circle, and the outside diameter drawing ratio was changed from 0.1z to The diameter of the other squeezing rolls is set to 0.5z, and although the hole shape of the other squeezing rolls remains elliptical, the outer diameter squeezing rate is increased to such an extent that there is no quality problem. Additionally, the larger the number of stands for the rolls that have the diameter-setting function of the forge-welded pipe making machine IO, the more it is possible to make the product closer to a perfect circle. Based on the premise, about 3 stands is appropriate.

Table 1 shows the average tube outer diameter (am) of each stand in the production line for forge-welded tubes with a product size of 50A.

Implementation of the invention makes it possible to obtain final product dimensions at the final stand of a forge welding tube machine. Further, according to this example, while conventionally, the occurrence of bite flaws was observed in 0.2 parts of the product, it is recognized that according to the present invention, no bite flaws occur. Further, according to this embodiment, by simplifying the manufacturing process, that is, by omitting the conventional sizer 40, each roll stand of the sizer 40 is not required, and it is possible to reduce the roll consumption rate (3 stands) and the electric power consumption rate. It becomes possible. In addition, other product dimensions 65A
When the present invention was applied to a production line for forge-welded pipes such as , 80A, etc., the same effects as described above were observed.

As described above, the present invention includes a forming process of forming a heated skelp into an arc shape, a forge welding process of abutting the edges of the skelp formed into an arc shape and forge welding it into a tubular shape, and a forge welding process of forming a heated skelp into a tubular shape. In a method for manufacturing a forge welded pipe, which includes a drawing process in which the pipe is sequentially reduced and rolled, and a cutting process in which the reduced and rolled pipe is cut into a predetermined length, the pipe is defined at the final stage of the drawing process. It is designed to be radially rolled. Therefore, it is possible to prevent the occurrence of biting flaws and to simplify the manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a conventional method for manufacturing a forge-welded pipe;
2(A) to 2(E) are front views showing each roll hole type shown in FIG. A) to (E) are front views showing each roll hole type in FIG. 3. l... Skelp, 2... Pipe, lO... Forge welding pipe making machine, it... Forming roll, 12... Forge welding roll, 13
．． 15.17.19.21.23A...Vertical roll,
14.16.18.20.22A, 24A...Horizontal roll, 30...Rotary hot saw.

Claims (1)

[Claims] (+) A forming process in which the heated skelp is formed into an arc shape, a forge welding process in which the edges of the arc-shaped skelp are abutted and forge welded into a tube shape, and a drawing process in which the forge welded pipe is sequentially reduced and rolled. and a cutting process of cutting the reduced-rolled pipe into a predetermined length, the forging-welded pipe is characterized in that the pipe is culm-rolled at the final stage of the drawing process. Manufacturing method for connecting pipes.