High-strength stainless steel pipe

Patent metadata

Field	Value
Publication number	US-2016355901-A1
Application number	US-201615241722-A
Country	US
Kind code	A1
Filing date	Aug 19, 2016
Priority date	May 7, 2009
Publication date	Dec 8, 2016
Grant date	—

Abstract

A stainless steel material having compositions which contain on the basis of percent by mass, C from 0.04 to 0.12%, Ni from 0 (including a case of no addition) to 5.0%, Cr from 12.0 to 17.0%, N from 0.0 to 0.10%, Si from 0.2 to 2.0%, Mn at 2.0% or less, Cu from 0.0 to 2.0%, P at 0.06% or less, S at 0.006% or less, with residue being Fe and unavoidable impurities. Further, a parent phase has any one of a single phase structure of ferrite phase or martensite phase and a diploid phase structure of ferrite phase and martensite phase. An end of the base material is melt-welded as a joint to form a pipe. The parent phase is provided with carbide uniformly separated at grain boundaries and within grains, with a dissolved amount of C being 0.03% by mass or less.

First claim

1 . A method for manufacturing a high-strength stainless steel pipe comprising the steps of:
performing a first heat treatment on a base material at a material temperature of 600° C. to 850° C. for a soaking period of 0 to 24 h; performing a second heat treatment on the base material at a material temperature within 50° C. different from that of the first heat treatment for a soaking period of 0 to 1 h; and melt-welding ends of the base material to form a joint for pipe formation, wherein the base material is a stainless steel material containing on the basis of percent by mass, C from 0.04 to 0.12%, Ni from 0 to 5.0%, Cr from 12.0 to 17.0%, N from 0 to 0.10%, Si from 0.2 to 2.0%, Mn at 2.0% or less, Cu from 0 to 2.0%, P at 0.06% or less, S at 0.006% or less, with residue being Fe and unavoidable impurities, in which a parent phase comprises any one of a single phase structure of ferrite phase, a single phase structure of martensite phase and a diploid phase structure of ferrite phase and martensite phase, the first and second heat treatments allows the parent phase to have carbide uniformly separated at grain boundaries and within grains and adjusted to be 0.03% or less in a dissolved amount of C, and the joint has a molten structure resulting from melt welding.

2 . The method according to claim 1 , further comprising the step of performing a third heat treatment on the pipe to dissolve separated carbide in the parent phase and the joint.

3 . The method according to claim 2 , wherein the parent phase and the joint after the third heat treatment comprises a single phase structure of a martensite phase or a diploid phase structure of a martensite phase and a ferrite phase.

Assignees

• Nisshin Steel Co Ltd

Inventors

• Isozaki Seiichi
• Hideshima Yasutoshi
• Fujimoto Hiroshi
• Suzuki Satoshi

Classifications

• C21D8/10

  during manufacturing of tubular bodies · CPC title

• C21D6/004

  containing Cr and Ni · CPC title

• C21D2211/008

  Martensite · CPC title

• C21D9/50 Primary

  for welded joints · CPC title

• C22C38/04

  containing manganese · CPC title