Ferritic stainless steel pipe having excellent salt tolerance in gap, pipe-end-thickened structure, welding joint, and welded structure

Patent metadata

Field	Value
Publication number	US-11215299-B2
Application number	US-201816492527-A
Country	US
Kind code	B2
Filing date	Mar 27, 2018
Priority date	Mar 30, 2017
Publication date	Jan 4, 2022
Grant date	Jan 4, 2022

Abstract

This ferritic stainless steel pipe contains, by mass %: C: 0.001% to 0.100%; Si: 0.01% to 2.00%; Mn: 0.01% to 2.00%; P: 0.001% to 0.05%; S: 0.0001% to 0.005%; Cr: 10.5% to 20.0%; Sn: 0.001% to 0.600%; Ti: 0.001% to 1.000%; Al: 0.001% to 0.100%; and N: 0.001% to 0.02%, with a balance being Fe and unavoidable impurities, the ferritic stainless steel pipe includes a pipe-end-thickened portion at a pipe end portion, and a gap distance d (μm) formed at the pipe end portion satisfies a relationship of d≥Cr2/(1000Sn) (in the expression, Cr and Sn represent amounts (mass %) of respective elements).

First claim

The invention claimed is:

1. A ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion, comprising, by mass %:
C: 0.001% to 0.100%;
Si: 0.01% to 2.00%;
Mn: 0.01% to 2.00%;
P: 0.001% to 0.05%;
S: 0.0001% to 0.005%;
Cr: 10.5% to 20.0%;
Sn: 0.001% to 0.600%;
Ti: 0.001% to 1.000%;
Al: 0.001% to 0.100%; and
N: 0.001% to 0.02%,
with a balance being Fe and unavoidable impurities,
the ferritic stainless steel pipe comprising:
a pipe end portion, and
a pipe-end-thickened portion at the pipe end portion, wherein the pipe-end-thickened portion is a portion of the ferritic stainless steel pipe where the ferritic stainless steel pipe is folded inwardly or outwardly, thereby causing a folded portion,
wherein a gap distance d, in micrometers, between the ferritic stainless steel pipe and the folded portion of the ferritic stainless steel pipe, satisfies:
d ≥Cr 2 /(1000Sn)

wherein Cr and Sn represent amounts, in mass %, of Cr and Sn, respectively, and
wherein the gap distance d is 3.5 to 65.3 μm.

2. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 1 , further comprising, by mass %, one or more of:
Ni: 0.1% to 1.0%;
Mo: 0.1% to 3.0%;
Cu: 0.10% to 3.00%;
B: 0.0001% to 0.0050%;
Nb: 0.001% to 0.300%;
W: 0.001% to 1.00%;
V: 0.001% to 0.50%;
Sb: 0.001% to 0.100%; and
Co: 0.001% to 0.500%.

3. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 1 , further comprising, by mass %, one or more of:
Ca: 0.0001% to 0.0050%;
Mg: 0.0001% to 0.0050%;
Zr: 0.0001% to 0.0300%;
Ga: 0.0001% to 0.0100%;
Ta: 0.001% to 0.050%; and
REM: 0.001% to 0.100%.

4. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 1 , which is used for a pipe-end-thickened structure.

5. A pipe-end-thickened structure comprising the ferritic stainless steel pipe according to claim 1 .

6. A welded joint comprising a pipe-end-thickened portion including the ferritic stainless steel pipe according to claim 1 .

7. The welded joint according to claim 6 , further comprising:
a structure that is joined by being welded to the pipe-end-thickened portion,
wherein, when a sheet thickness of a single pipe portion of the ferritic stainless steel pipe is represented by t, a maximum penetration depth on a side of the ferritic stainless steel pipe in a welded portion is 0.3 t to 2.0 t.

8. A welded structure comprising the welded joint according to claim 7 .

9. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 2 , further comprising, by mass %, one or more of:
Ca: 0.0001% to 0.0050%;
Mg: 0.0001% to 0.0050%;
Zr: 0.0001% to 0.0300%;
Ga: 0.0001% to 0.0100%;
Ta: 0.001% to 0.050%; and
REM: 0.001% to 0.100%.

10. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 2 , which is used for a pipe-end-thickened structure.

11. The ferritic stainless steel pipe having excellent corrosion resistance against salt damage in a crevice portion according to claim 3 , which is used for a pipe-end-thickened structure.

12. A pipe-end-thickened structure comprising the ferritic stainless steel pipe according to claim 2 .

13. A pipe-end-thickened structure comprising the ferritic stainless steel pipe according to claim 3 .

14. A pipe-end-thickened structure comprising the ferritic stainless steel pipe according to claim 4 .

15. A welded joint comprising a pipe-end-thickened portion including the ferritic stainless steel pipe according to claim 2 .

16. A welded joint comprising a pipe-end-thickened portion including the ferritic stainless steel pipe according to claim 3 .

17. A welded joint comprising a pipe-end-thickened portion including the ferritic stainless steel pipe according to claim 4 .

Assignees

• Nippon Steel Stainless Steel Corp

Inventors

• Abe Masatoshi
• Hamada Junichi
• Hiraide Nobuhiko

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C22C38/60

  containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/46

  with vanadium · CPC title

• C21D8/0263

  following hot rolling · CPC title