JPH02229671A - Structure for connecting steel strips for manufacturing resistance welded steel tube - Google Patents

Abstract

PURPOSE:To reduce the factor of rupture of a connection of steel strips by providing a through hole on a butt weld zone of the steel strips. CONSTITUTION:The end faces of the steel strips 1 are abutted on each other and a weld bead 2 is formed on the connection part 3 produced by welding a butt part by flash butt welding, MIG welding, etc. The weld bead 2 is cut off and the connection part 3 is finished to the same thickness as the steel strips 1 to form a plane. The oblique line part 4 is heated and subjected to postheating treatment with the connection part 3 as a center. The through hole 5 is perforated by a punch 6 on the connection part 3. The stress applied on the connection part 3 at the time of forming the resistance welded steel pipe can be concentrated on the base metal part of the steel strips and rupture of the connection part 3 is prevented. Since the factor of rupture is reduced remarkably, the shutdown of operation and lowering of yield are prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a connection structure for steel strips for manufacturing electric resistance welded steel pipes, comprising:
This article relates to a connection structure that prevents the joints of steel strips from breaking during forming of copper strips. [Prior Art] In the production of ERW steel pipes, as shown in FIG. 4, from the viewpoint of improving yield and production efficiency, the steel strip 31 for producing ERW steel pipes is rolled using a plate down roll 32 or a fin pass roll. 33 (in the direction of the arrow in the figure) is a welding machine 35 installed before the forming process 34.
Then, the rear end of the leading steel strip and the leading end of the trailing steel strip are abutted against each other, and the abutted parts are welded and connected, so that the steel strip 31 is fed in an endless state. To explain the work steps in detail, as shown in FIG. 5, there is a connection step 351 of welding the steel strips together, a weld bead cutting step 352 of the welded portion following this step, and a post-heat treatment step 35 of the welded portion.
It consists of 3. Then, in the connecting step 351, the steel strip 3
The joint obtained by welding two pieces together has a raised weld bead. The raised weld bead at this joint is removed in the next weld bead cutting step 3.
52, it is removed to the same thickness as the steel strip 31. Next, in a post-heat treatment step 353, heat treatment is performed to improve toughness by heating using heating means such as electric resistance heating or electric induction heating. In this way, the connection work of the connection part is completed. [Problems to be solved by the invention] However, the conventional connection structure of steel strips for manufacturing electric resistance welded steel pipes has the following problems. In other words, the toughness of the joints of copper strips has decreased due to rapid cooling during welding, so these welds are post-heat treated to create a ductile structure and prevent breakage. However, it is extremely difficult to create a structure with ideal ductility that is uniform over the entire length of the weld because the shape of the heat conduction is different between the widthwise center and both ends of the copper strip. As a result, especially as the plate thickness/outside diameter ratio of ERW steel pipes increases, the strain added during forming also increases, and the probability of the copper strip connection breaking increases. come. As described above, it was not possible to completely prevent the copper strip from breaking due to the difficulty of creating a structure with uniform ideal ductility over the entire length of the weld. The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a connection structure for steel strips for manufacturing ERW steel pipes that does not break during the forming of ERW steel pipes. [Means for Solving the Problems] A connecting ellipse for steel strips for manufacturing electric resistance welded steel pipes according to the present invention is provided by abutting the rear end end face of the leading steel strip and the leading end end face of the trailing steel belt. This is a connection structure for steel strips for manufacturing ERW steel pipes, in which a through hole is provided in the connection area obtained by welding the butt parts. [Function] The connection structure of steel strips for manufacturing electric resistance welded steel pipes according to the present invention is obtained by butting the rear end end face of the leading steel strip and the leading end face of the trailing steel strip, and welding the abutted portions. Since a through hole is provided in the connected portion, the stress applied to the connected portion during forming of the tm steel pipe can be concentrated on the base material of the copper strip, and breakage of the connected portion can be prevented. [Example] An example of the connection structure for steel strips for manufacturing ERW steel pipes according to the present invention will be described based on the drawings. Figure 1 shows a connection structure of steel strips for manufacturing electric resistance welded steel pipes according to an embodiment of the present invention. A connecting part 3 obtained by abutting the end faces of the steel strip 1 and welding the abutted parts has a through hole 5 in its center. Such a connection part 3 can concentrate the stress applied to the connection part during forming of an electric resistance welded steel pipe onto the base material of the steel strip, thereby preventing the connection part from breaking. next,
The procedure for creating the connection part 3 described above will be explained. First, Figure 1 (a
), a weld bead 2 is formed in a joint 3 obtained by abutting the end surfaces of the steel strip 1 and performing flash butt welding, MIG welding, or other welding methods on the abutted portion. Next, as shown in Fig. 1(b), the weld bead 2 is shaved off to form a flat connecting part 3 with the same thickness as the steel strip 1. Next, as shown in FIG. 1(c), a post-heat treatment is performed by heating the shaded area 4 centering on the connection part 3. Finally, as shown in FIG.
Formed by punching and perforating. The through hole 5 is bored in the center of the steel strip 1 in the width direction, has a diameter larger than the width W of the connecting portion 3, and is circular. FIG. 2 shows the weld breakage rates of the conventional connection structure without through holes and the connection structure of the present invention, where the component is C: 0.20%.
This is a graph diagram organized in terms of the relationship between tube thickness and tube outer diameter for Mn: 1.10%. As is clear from this figure, in the connection structure of the present invention, the rupture rate is almost zero, which is extremely high. Good results were obtained, and the rupture rate was 10 to 10% lower than conventional
This is an improvement of about 20%. Note that the through hole 5 may be formed by cutting by drilling or the like. Moreover, it is a design matter that a person skilled in the art can make, such as making the shape of the through-hole 5 elliptical or polygonal with rounded corners, and arranging a plurality of through-holes in parallel. [Effects of the Invention] According to the present invention, the rupture rate of the joints of steel strips for manufacturing electric resistance welded steel pipes is significantly reduced, resulting in excellent results such as eliminating operation stoppages due to joint ruptures and yield reductions due to loss of ruptures. It has an effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a connection structure of a steel strip for manufacturing an ERW steel pipe according to an embodiment of the present invention, and FIGS. 2(a) to (d) show a steel strip for manufacturing an ERW steel pipe according to an embodiment of the present invention. An explanatory diagram showing the procedure for creating a band connection structure, Fig. 3 is a graph showing the connection breakage rate of the connection structure of the present invention and a conventional connection structure, and Fig. 4 is a partial schematic diagram of the electric resistance welded steel pipe manufacturing process. , FIG. 5 is an explanatory diagram showing the procedure for connecting copper strips. 1... Steel strip, 2... Weld bead, 3... Connection part,
4...Post heat treatment section, 5...Through hole. (b) Figure 1 (C) Figure 2 (d)

Claims (1)

[Claims] ERW steel pipe manufacturing characterized by abutting the rear end end face of the leading steel strip and the leading end face of the trailing steel belt, and providing a through hole in the connection obtained by welding the butted parts. Connection structure for steel strips.