Electric resistance welded steel pipe excellent in deformability and fatigue properties after quenching

Patent metadata

Field	Value
Publication number	US-9757780-B2
Application number	US-201013256357-A
Country	US
Kind code	B2
Filing date	Mar 25, 2010
Priority date	Mar 25, 2009
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Electric resistance welded steel pipe excellent in deformability and fatigue properties after quenching which enables working into complicated shapes without spheroidization and which improves the fatigue properties after cold working and quenching without carburization are provided. The electric resistance welded steel pipe is characterized by containing, by mass %, C: 0.15 to 0.55%, Si: 0.01 to 0.30%, Mn: 0.5 to 1.5%, Ca: 0.0010 to 0.0030%, S: 0.0005 to 0.0050%, and O: 0.0005 to 0.0050%, having contents of Ca, O, and S satisfying 0.10≦[Ca](1−124[O])/1.25[S]≦2.50, having Ca-based inclusions present at the base material and electric resistance weld zone with an average particle size of 1.0 to 10 μm and a density of 3 to 300/mm 2 , and having a difference ΔHv of the maximum hardness of the electric resistance weld zone and the average hardness of the base material part satisfying 100 to 500.

First claim

The invention claimed is:

1. An electric resistance welded steel pipe comprising, by mass %,
C: 0.30 to 0.55%,
Si: 0.01 to 0.30%,
Mn: 0.5 to 1.5%,
Ca: 0.0010 to 0.0030%,
S: 0.0005 to 0.0050%, and
O: 0.0005 to 0.0050%,
restricting
P: 0.020% or less,
N: 0.0050% or less, and
Al: 0.050% or less,
having a balance of Fe and impurities,
having contents of Ca, O, and S satisfying
0.10≦[Ca](1-124[O])/1.25[S]≦2.50,

having Ca-based inclusions present at a base material and electric resistance weld zone with an average particle size of 1.0 to 10 μm and density of 3 to 300/mm 2 , and
having a difference ΔHv of a maximum hardness of the electric resistance weld zone and average hardness of a base material part of 100≦ΔHv≦500,

wherein:
heat treatment of the welded steel pipe is not performed after pipe-making, and
the welded steel pipe is in a state of the pipe as-produced, without performing heat treatment.

2. The electric resistance welded steel pipe as set forth in claim 1 , further comprising, by mass, Mo: 0.25% or less.

3. The electric resistance welded steel pipe as set forth in claim 1 or 2 , further comprising, by mass %, Ti: 0.030% or less and B: 0.0050% or less.

4. The electric resistance welded steel pipe as set forth in claim 1 or 2 , further comprising, by mass %, one or more of Ni: 1.00% or less, Cu: 1.00% or less, Cr: 1.50% or less, Mo: less than 0.05%, Nb: 0.050% or less, and V: 0.040% or less.

5. The electric resistance welded steel pipe as set forth in claim 1 or 2 , wherein the base material has a thickness of 4 to 12 mm.

6. The electric resistance welded steel pipe as set forth in claim 1 , wherein the content of C is 0.35 to 0.55%.

Assignees

• Sakamoto Shinya
• Hara Takuya
• Terada Yoshio
• Sebayashi Takafumi
• Hiroshige Itsuroh
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Sakamoto Shinya
• Hara Takuya
• Terada Yoshio
• Sebayashi Takafumi
• Hiroshige Itsuroh

Classifications

• Y02P10/20

  Recycling · CPC title

• C22C38/04

  containing manganese · CPC title

• C21D9/08

  for tubular bodies or pipes · CPC title

• B21C37/08 Primary

  Making tubes with welded or soldered seams {(with helically arranged seams B21C37/122)} · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title