JPH01309731A - Method for forming resistance welded pipe - Google Patents

Abstract

PURPOSE:To uniformize a thickness of a small diameter thick walled pipe by disposing edge upset rolls preceding break-down rolls and increasing the radius of the end part of the prescribed upper break-down rolls by specified % of the wall thickness. CONSTITUTION:On the upstream of plural break-down roll stands 3, the edge upset rolls 2 with formed tapered parts are disposed. Further, the end part radius RET of the upper roll 32 of the break-down roll 31 is expanded by a range of 1-5% of the thickness (t) of a steel loop 1. By this method, the steel loop 1 is enlarged in its thickness of both end parts, then, formed by the break- down rolls 31 of the preceding stage, succeedingly, formed by stands 4, 5 of cage rolls and fin pass rolls. Because the thickness is thickened by rolls 2, further, the forming is reinforced by rolls 31, the thickness of the pipe is formed uniformly. Therefor, the thickness of the small diameter thick pipe is uniformized.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for forming a thick-walled, small-diameter electric resistance welded tube.

[Prior Art] Electric resistance welded pipes are manufactured by cutting a hot-rolled coil into steel strips, forming the steel strips into a circular shape through breakdown rolls and fin pass rolls, and then pressurizing and welding them with a welding machine. With the conventional forming method, when forming a thick-walled tube as shown in Figure 6, ■
During the thinning of the edge portion of the steel strip that occurs during coil cutting, (2) thinning of the edge portion and the initial breakdown forming process, the edge portion of the steel strip 1 comes into strong contact with the lower roll 12, and the upper roll 11 Since the edge part (A>) is not in contact with the other parts, the thickness of the edge part (A> is reduced and the forming is insufficient. Also, as shown in FIG. 7,
■Because the difference in circumference between the inside and outside of the pipe is too large, the butt shape immediately before welding tends to be V-shaped instead of the ideal T-shape.For this reason, weld bead B (C stands for welding) is formed on the inner surface. line)
becomes abnormally large, making it difficult to cut the bead and making it impossible to obtain a sound welded part quality, making it difficult to manufacture thick-walled ERW pipes, especially thick-walled, small-diameter ERW pipes. na 1
．． Among the problems listed in E, Japanese Patent Application Laid-Open No. 62-2 is a method for increasing the thickness of the edge of the steel strip that occurs when cutting the coil.
There is 52685. In this method, a thickened portion is formed at the edge using a tapered roll.

[Problem to be solved by the invention] Even if the thickness of the edge of the steel strip that is thinned during coil cutting is increased using a tapered roll, the thinning of the edge of the steel strip that occurs during the initial breakdown forming process and insufficient forming. Because of this and because the difference in circumferential length between the inside and outside of the tube is too large, the butt shape immediately before welding becomes V-shaped, resulting in the problem that a thick-walled electric resistance welded tube cannot be manufactured.

[Means and effects for solving the problem] The present invention aims to solve the above-mentioned problems, and provides an electric resistance welded pipe in which a steel strip is formed into a circular shape through a plurality of breakdown rolls and fin pass rolls. In the forming method, an edge upset roll is attached prior to the breakdown roll, and the upper roll of the pair of upper and lower rolls constituting the pre-stage breakdown roll has an end radius of 1 to 5 times the thickness of the steel strip. %, both ends of the steel strip are thickened with the edge upset rolls, and then the steel strip is passed through the preceding breakdown roll to form an electric resistance welded tube. It's a method. That is, in this method, both ends of the steel strip are thickened using an edge upset roll, and the end faces of both ends are tapered. Thereafter, in the front stage of the breakdown stand, the upper roll of the pair of E lower rolls constituting the breakdown stand is used as a roll with an enlarged end radius in the range of 1 to 5% of the thickness of the steel strip. The structure is such that the clearance between the upper and lower rolls becomes smaller as the formed caliber approaches the edge of the steel strip. Therefore, although the edge portion of the steel strip is slightly thinned through the upper and lower rolls, the space between the upper and lower rolls is completely filled, and the steel strip is formed according to the caliber of the upper and lower rolls. Furthermore, the thinning caused by the breakdown roll is increased by squeezing in the subsequent fin pass roll stand, and the thickness is restored to the original board thickness.

In the present invention, as described above, it is necessary to increase the thickness of both ends of the steel strip and to form the steel strip through rolls whose diameters are expanded to a range of 1 to 5% of the thickness of the steel strip. If the expanded diameter portion of the roll is less than 1% of the thickness of the steel strip, the object of the present invention cannot be fully achieved. On the other hand, if it exceeds 5%, the steel strip becomes too thin, and as a result, the thickness of the steel strip becomes uneven, which adversely affects the quality.

[Embodiments of the Invention] Examples of the present invention will be described below. Fig. 1 is a diagram of the manufacturing process of the electric resistance welded pipe of the present invention. Fig. 0 shows an edge upset roll 2, a breakdown roll stand 3 composed of a plurality of breakdown rolls, a cage roll stand 4, and a plurality of fin pass rolls. A fin pass roll stand 5, a heating machine 6, and a squeeze roll 7 are arranged in this order. Here, the edge upset roll 2 forms a taper 21 as shown in Fig. 2, and this taper angle (θ) is set to 10 to 20 degrees in order to form an I-shaped groove at the weld. As shown in FIG. R, end radius RE↑
The following formulas (1) and (2) are used between
) is necessary.

RT=RB-t...(1)RET=
REB t + α...
2) Here, t indicates the thickness of the steel strip, and α
indicates the enlarged diameter portion. And α is the thickness of the steel strip (
It is necessary to keep it within the range of 1 to 5% of 1). As mentioned above, if the enlarged diameter portion of the roll is less than 1% of the thickness of the steel strip, the object of the present invention cannot be fully achieved as in the past. On the other hand, if it exceeds 5%, the steel strip becomes too thin, and as a result, the thickness of the steel strip becomes uneven, which adversely affects the quality.

Using the apparatus shown in FIGS. 1, 2, and 3, the steel strip 1 is thickened at both ends with edge upsetting rolls 2, and then the steel strip 1 is subjected to pre-breakdown. It is formed through rolls 31. The steel strip 1 that has passed through the breakdown roll stand 3 is then further shaped in a cage roll stand 4, and then shaped into a circular shape in a fin pass roll stand 5, as well as forming a butt portion. During forming of this abutting portion, the thickness reduced by the breakdown roll 31 is increased and the plate thickness is restored. Thereafter, it passes through a heating machine 6 and a squeeze roll 7 to be pressurized and welded.

In the above device, edge upset roll 2
The taper angle (θ) of this is set to 15 degrees, and the front breakdown roll 31 of the breakdown roll stand 3
An electric resistance welded tube (size: 42.7 mm outer diameter x 11
．． 0 mm wall thickness), and was pressurized and welded to produce an electric resistance welded tube. The cross section of the product in this case is shown in Figure 4, and the measurement results of the wall thickness distribution in the circumferential direction of this ERW tube are shown in Figure 5.
In the figure, the vertical axis shows the wall thickness, the horizontal axis shows the position from the welding part in the circumferential direction from left to right, and the wall thickness of the electric resistance welded pipe in the circumferential direction is plotted.

As is clear from the figure, it is clearly seen that an electric resistance welded tube with uniform wall thickness in the circumferential direction is manufactured.

[Effects of the Invention] According to the present invention, both ends of a steel strip are thickened by an edge-up roll, and then, at the front stage of a breakdown roll stand, the end radius of the upper roll is set to 1 to 1 of the thickness of the steel strip. 5%
Since both ends of the steel strip are sufficiently formed using a roll with an expanded diameter in the range of It has become possible to manufacture thick-walled electric resistance welded tubes with uniform wall thickness in various directions, especially thick-walled electric resistance welded tubes with small diameters.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the manufacturing process of the present invention, Fig. 2 is a diagram showing the shape of the edge upset roll used in the method of the present invention, and Fig. 3 is a diagram showing the shape of the upper and lower rolls used in the method of the present invention. , FIG. 4 is a cross-sectional view of a small-diameter thick-walled ERW tube manufactured by the method of the present invention, and FIG. 5 is a graph showing the distribution of the circumferential wall thickness of the small-diameter, thick-walled ERW tube manufactured by the method of the present invention. 6
The figure shows how a steel strip is formed by a conventional breakdown roll, and FIG. 7 shows how an inner bead is formed in a thick-walled electric resistance welded tube produced by a conventional method. 1... Steel strip body, 2... Edge upset roll,
21... Taper, 32... Upper roll, 33...
Lower roll, C...welding line.

Claims (1)

[Claims] In an electric resistance welded pipe forming method in which a steel strip is formed into a circular shape through multiple breakdown rolls and fin pass rolls,
An edge upset roll is attached prior to the breakdown roll, and the end radius of the upper roll in a pair of upper and lower rolls of the preceding breakdown roll is expanded to a range of 1 to 5% of the thickness of the steel strip. and thickening both ends of the steel strip with the edge upset roll,
A method for forming an electric resistance welded pipe, characterized in that the steel strip body is then passed through the pre-stage breakdown roll and formed.