JPS61115614A - Production of square tube - Google Patents

Abstract

PURPOSE:To enable the formation of the square tube having different peripheral length from the tube stock of a fixed outer diameter without using enormous thermal energies nor damaging the surface skin by heating only the square part forming position of the tube stock in forming a strip plate by an square forming roll after forming it in a round tube stock. CONSTITUTION:A strip plate 11 is formed in a round tube stock 14 with electro- resistance welding after its tubular shape formation by a round shape forming roll device 12. The square part forming position 17 of the tube stock 14 is then heated by the heating coil 16 of an induction heating device 15 and immediately thereafter is formed in square shape via a square shape forming roll device 18, made in a square steel tube 19 and cut in a regular size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing square tubes, such as square tubes, hexagonal tubes, etc., from a strip plate.

[Prior Art] FIGS. 4(A) to 4(C) are process diagrams showing a conventional cold-open forming method for square steel pipes. The strip l shown in FIG. 4(A) is formed into a strip shape by a plurality of breakdown rolls and side rolls, and then passed through fin pass rolls and subjected to electric resistance welding just before the squeeze roll. A round blank tube 2 shown in (B) is formed into a round shape. Furthermore, this round blank pipe 2 is square-shaped into a square steel pipe 4 by a square-forming roll device 3, as shown in FIG. 4(C).

[Problems to be Solved by the Invention] However, in the method for manufacturing a square tube using the cold-open forming method described above, the corner portions of the square steel tube 4 are poorly formed, and the corner portions of the square steel tube 4 have no. When a large roundness is formed as shown by the solid line in the figure, and each time the circumferential length of the square steel pipe 4 is different, it is necessary to adjust the outer diameter of the round raw pipe 2, and the strip plate l must be formed into a round shape. There are disadvantages in that the shaped roll device has many different types of rolls, and production is halted to replace the rolls.

In addition, in order to eliminate the disadvantages associated with adjusting the outer diameter w4 of the round blank pipe 2 due to corner defects, corners, and changes in the circumferential length of the square steel pipe 4 due to the cold forming method, the round blank A method has also been proposed in which the entire circumference of the tube 2 is heated and then molded. However, this all-circumference heating method requires a large amount of energy for heating and is accompanied by deterioration of the surface texture due to the generation of heating scales, making it unsuitable.

The present invention improves the shape of the corners of square tubes without using a large amount of thermal energy and without damaging the surface texture, and forms square tubes with different circumferences from round blank tubes with a constant outer diameter. The purpose is to make it possible.

[Means for solving problems] In the present invention, after the band plate is formed into a round tube.

In the method for manufacturing a square tube in which the round blank tube is squared into a square tube using a square forming roll device, the square forming is completed while the corner S forming position of the blank tube is heated.

[Function] According to the present invention, the heated portion of the raw pipe is formed into a corner by the corner forming roll device, and it becomes possible to obtain a good corner shape.

In addition, the circumferential length of the blank tube is reduced in the heated portion, making it possible to form square tubes with different circumferential lengths from a round blank tube with a constant outer diameter. In addition, since the above-mentioned heating of the raw pipe is partial heating of only the corner forming position, a large amount of thermal energy is not used, and the surface texture is not deteriorated due to the generation of heating scale.

[Example] FIGS. 1A to 1D are process diagrams showing a method for forming a square steel pipe according to the present invention, and FIG. 2 is a layout diagram showing a pipe manufacturing line to which this forming method is applied.

The strip plate if shown in FIG. 1(A) is rolled in a round shape! 1
At 12, after being formed into a V shape by a plurality of breakdown rolls and side rolls, it is subjected to electric resistance welding by a welding machine 13 after passing through fin pass rolls and immediately before a squeeze roll, as shown in FIG. 1(B). The round pipework 4 is formed into a round shape.

This round blank tube 14 is heated at the corner portion at17 by the heating coil 16 of the induction heating device 1115. Immediately after the round raw pipe 14 is heated at the corner forming position 17, it is formed into a square shape through a plurality of roll stands of a square forming roll device 18, and becomes a square steel pipe 19. The rectangular steel pipe 19 is cut into a fixed length by 1" by a running cutting machine 20, and is carried out to a table 21.

According to the above embodiment, the heated portion of the S-round tube 14 is rolled into a square shape! 18, and it becomes possible to obtain a good corner shape as shown by the two-dot chain line in FIG.

It is also possible to reduce the number of roll stands of the square forming roll device 18.

In addition, the circumferential length of the round blank tube 14 is narrowed at the heating part, and the circumferential length can be changed by several degrees of 10 when forming into a square. 19 can be molded. Therefore, it is possible to share the rolls of the round forming roll device 12 for square steel pipes 19 having different circumferential lengths.

Furthermore, the heating of the round material tube 14 is performed at the corner forming position 51.
Since only 17 is partially heated, a large amount of thermal energy is not used, and the surface skin is not deteriorated due to the generation of heating scale.

In addition, the above-mentioned Example explained the case where the corner forming position al17 of the round blank tube 14 is heated by the induction heating device 15. However, the round forming roll device 12 and the induction heating device i! of FIG. 115, and immediately after preforming the round blank tube 14 into a substantially square blank tube 23 as shown in FIG. The position 24 may be heated by the heating coil 16 of the induction heating device 15, and then the angular formation may be completed by the angular forming roll g118.

[Effects of the Invention] As described above, the present invention provides a method for manufacturing a square tube, in which a strip is formed into a round tube, and then the round tube is squared into a square tube using a square forming roll device. In this method, the corner forming position of the raw tube is heated to complete the corner forming.

Therefore, it is possible to improve the corner shape of a square tube without using a large amount of thermal energy and without damaging the surface texture, and to form square tubes with different lengths from a round blank tube with a constant outer diameter. It becomes possible.

[Brief explanation of the drawing]

Figures 1 (A) to (D) are process diagrams showing the method of forming square steel pipes according to the present invention, Figure 2 is a layout diagram showing a pipe manufacturing line to which this forming method is applied, and Figure 3 is a diagram showing the method of forming square steel pipes according to the present invention. 4(A) to 4(C) are process diagrams showing a method of forming a square steel pipe according to a conventional example, and FIG. 5 is a front view of a main part showing a corner shape of a square steel pipe. be. 11... Band plate, 12... Round forming roll device, 14
...Round tube, 15...Induction heating device, 16...
Heating coil, 17... Corner forming position, 18... Square forming roll device, 19... Square steel pipe, 23... Substantially square blank pipe, 24... Corner forming position.

Claims (1)

[Claims] (1) In a method for manufacturing a square tube in which a band plate is formed into a round blank tube and then the round blank tube is squared into a square tube using a square forming roll device, the corner forming position of the blank tube is heated. A method for manufacturing a square tube, characterized in that the square tube is formed under the following conditions.