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Seamless steel pipe and its manufacturing method

A technology of seamless steel pipe and manufacturing method, which is applied in the direction of manufacturing tools, pipes, rigid pipes, etc., can solve the problems of easy hardening, peripheral weld toughness, and HIC resistance reduction, and achieve the effect of excellent HIC resistance

Active Publication Date: 2017-05-24
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when circumferentially welding seamless steel pipes with improved hardenability to each other, the welded heat-affected zone tends to harden, and the toughness and HIC resistance of the circumferentially welded zone decrease.

Method used

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  • Seamless steel pipe and its manufacturing method
  • Seamless steel pipe and its manufacturing method
  • Seamless steel pipe and its manufacturing method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0136] A plurality of seamless steel pipes having various chemical compositions were produced, and the strength, toughness, inner surface layer hardness, and HIC resistance of the seamless steel pipes were investigated. Furthermore, the seamless steel pipe was circumferentially welded, and the toughness, hardness, and HIC resistance of the circumferentially welded portion were investigated.

[0137] [investigation method]

[0138] Various molten steels having the chemical compositions shown in Table 1 were produced in a 40 t electric furnace. Ingots are made from molten steel. Hot forging ingots to make round billets.

[0139] In addition, "-" in Table 1 indicates that the content is below the measurement limit.

[0140] Table 1

[0141]

[0142] Each manufactured round billet is heated to 1100-1300 degreeC by a heating furnace. Next, each round billet is pierced and rolled by a piercer to form a tube billet. Next, each blank pipe was stretch-rolled by a mandrel mill....

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Abstract

A seamless steel pipe has a carbon equivalent Ceq of 0.50% to 0.58%, and contains specified carbides containing Mo at a ratio of 50 mass% or more, V, and at least one selected from the group consisting of Ti and Nb, and having a size of 20 nm or more.

Description

technical field [0001] The present invention relates to a seamless steel pipe and a method for manufacturing the same, and more specifically, to a seamless steel pipe suitable for line pipe use and a method for manufacturing the same. [0002] This application claims priority based on Japanese Patent Application No. 2012-188634 for which it applied to Japan on August 29, 2012, The content is used here. Background technique [0003] In recent years, oil wells and gas wells have been developed in harsher acid environments than before, represented by deep sea and cold regions. Submarine pipelines erected in such a severe acid environment require higher strength (pressure resistance) and toughness than conventional ones, and further require hydrogen-induced cracking resistance (HIC resistance). [0004] For submarine pipelines requiring such characteristics, seamless steel pipes are more suitable than welded steel pipes. This is because the welded steel pipe has welded portion...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C21D1/18C21D8/10C21D9/08C22C38/38C22C38/58
CPCC21D1/18C21D6/002C21D6/004C21D6/005C21D6/008C21D8/10C21D8/105C21D9/08C21D9/085C21D2211/004C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/20C22C38/22C22C38/24C22C38/26C22C38/28C22C38/38C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/58F16L9/02
Inventor 荒井勇次小林宪司长山展公
Owner NIPPON STEEL CORP
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