Manufacturing method of steel pipe
A manufacturing method and technology for steel pipes, applied in the field of steel pipe manufacturing, can solve problems such as inability to join, deformation of steel pipes, etc.
Active Publication Date: 2017-03-08
JFE STEEL CORP
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Problems solved by technology
Therefore, when the roundness of the UOE steel pipe is low, the pipe ends of the UOE steel pipe cannot be butted and joined during circumferential welding.
Moreover, when the roundness of the UOE steel pipe is low, when the UOE steel pipe is laid in a high-pressure environment such as deep sea, the steel pipe is easily deformed by pressure.
Method used
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Embodiment Construction
[0032] As a result of intensive research, the inventors of the present invention have found that, in the case of a forming process using a press bending method (also referred to as a press bend method) instead of U-shaped and O-shaped press molding (hereinafter referred to as a UO process), The shape of the seam-welded steel pipe is better than that of the UO process. Therefore, it was found that even if the pipe expansion R ratio is increased compared with the UO process, the pipe expansion die will not be damaged by cracks. This is considered to be due to the following mechanism. In the forming process of the press bending method, the steel plate as the raw material is divided into multiple parts in the width direction of the plate and press-formed. Therefore, even if there are small unevenness in the circumferential direction when forming into a tube shape, the undeformed part will not be deformed. Nor will it continue for a long time. On the other hand, in the UO process...
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A method for manufacturing a steel pipe includes forming a steel plate into a cylindrical shape by a bending press method that presses down the steel plate with a punch having, at a leading edge thereof, an outer circumferential surface with a circular arcuate section so that edges in a width direction of the steel plate face each other; butting and welding together the edges in the width direction of the steel plate; and expanding the steel pipe from the inside using a pipe expanding machine in which a plurality of pipe expanding dies having an outer circumferential surface with a circular arcuate section are circumferentially arranged, wherein a pipe expanding R ratio that is a ratio of a curvature radius of the outer circumferential surface of each of the pipe expanding dies to a target radius of an inner surface of the steel pipe and a punch R ratio that is a ratio of a curvature radius of an outer circumferential surface of a leading end of the punch to the target radius of the inner surface of the steel pipe are both less than 1, and the pipe expanding R ratio and the punch R ratio satisfy a predetermined conditional expression. As a result, a steel pipe with high roundness can be manufactured without cracking a pipe expanding die.
Description
technical field [0001] The present invention relates to a method of manufacturing a steel pipe including a pipe expanding step of expanding a steel pipe from inside using a pipe expander provided with a plurality of pipe expanding dies having an outer peripheral surface having an arc-shaped cross-section arranged in a circumferential direction. Background technique [0002] In general, the manufacturing process of UOE steel pipes for oil well pipes, line pipes, etc. includes the following steps: performing edge preparation on the widthwise end of a thick steel plate as a raw material; using a C-type punching machine After bending the ends of the thick steel plate in the width direction, the forming process of forming the thick steel plate into a cylindrical shape using U-shaped and O-shaped presses so that the ends of the thick steel plate face each other in the width direction; constraining the cylinder The spot welding process of butt-welding the width direction ends of th...
Claims
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IPC IPC(8): B21D39/20B21D5/01
CPCB21D5/015B21C37/0815B21D3/14B21D39/20
Inventor 三轮俊博
Owner JFE STEEL CORP