Ferrite-based stainless steel with high resistance to corrosiveness caused by exhaust gas and condensation and high brazing properties and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-10752973-B2
Application number	US-201916368260-A
Country	US
Kind code	B2
Filing date	Mar 28, 2019
Priority date	Oct 31, 2014
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

This ferritic stainless steel contains, by mass %, C: 0.001% to 0.030%; Si: 0.01% to 1.00%. Mn: 0.01% to 2.00%, P: 0.050% or less, S: 0.0100% or less, Cr: 11.0% to 30.0%, Mo: 0.01% to 3.00%, Ti: 0.001% to 0.050%, Al: 0.001% to 0.030%, Nb: 0.010% to 1.000%, and N: 0.050% or less, with a remainder being Fe and inevitable impurities, wherein an amount of Al, an amount of Ti, and an amount of Si (mass %) satisfy Al/Ti≥8.4Si-0.78.

First claim

The invention claimed is:

1. A ferritic stainless steel, comprising, by mass %:
C: 0.001% to 0.030%;
Si: 0.01% to 1.00%;
Mn: 0.01% to 2.00%;
P: 0.050% or less;
S: 0.0100% or less;
Cr: 11.0% to 30.0%;
Mo: 0.75% to 3.00%;
Ti: 0.001% to 0.026%;
Al: 0.001% to 0.030%;
Nb: 0.010% to 1.000%; and
N: 0.050% or less,
with a remainder being Fe and inevitable impurities,
wherein an amount of Al, an amount of Ti, and an amount of Si (mass %) satisfy Al/Ti≥8.4Si-0.78,
a rolling direction is represented by an L direction, a direction perpendicular to the rolling direction is represented by a C direction, a direction inclined at 45° with respect to the rolling direction is represented by a V direction, and arithmetic average roughness values of a steel surface in the respective directions are respectively represented by R aL , R aC , and R aV (unit: μm), then (R aL +R aC +2R aV )/4≤0.50 and |(R aL +R aC −2R aV )/2|≤0.10 are satisfied.

2. The ferritic stainless steel according to claim 1 , further comprising, by mass %, any one or more of:
Ni: 0.01% to 3.00%;
Cu: 0.050% to 1.500%;
W: 0.010% to 1.000%;
V: 0.010% to 0.300%;
Sn: 0.005% to 0.500%,
Sb: 0.0050% to 0.5000%,
Mg: 0.0001% to 0.0030%,
B: 0.0002% to 0.0030%;
Ca: 0.0002% to 0.0100%;
Zr: 0.010% to 0.300%;
Co: 0.010% to 0.300%,
Ga: 0.0001% to 0.0100%,
Ta: 0.0001% to 0.0100%, and
REM: 0.001% to 0.200%.

3. The ferritic stainless steel according to claim 2 ,
wherein an amount of change in grain size number (GSN) before and after a thermal treatment at 1,150° C. for 10 minutes in a vacuum atmosphere of 50 Pa or lower is 5.0 or less.

4. The ferritic stainless steel according to claim 3 which is used in automobile mufflers, exhaust heat recovery devices, and EGR coolers that are automobile parts exposed to exhaust gas-condensate environments.

5. The ferritic stainless steel according to claim 2 which is used in automobile mufflers, exhaust heat recovery devices, and EGR coolers that are automobile parts exposed to exhaust gas-condensate environments.

6. The ferritic stainless steel according to claim 1 ,
wherein an amount of change in grain size number (GSN) before and after a thermal treatment at 1,150° C. for 10 minutes in a vacuum atmosphere of 50 Pa or lower is 5.0 or less.

7. The ferritic stainless steel according to claim 6 which is used in automobile mufflers, exhaust heat recovery devices, and EGR coolers that are automobile parts exposed to exhaust gas-condensate environments.

8. The ferritic stainless steel according to claim 1 which is used in automobile mufflers, exhaust heat recovery devices, and EGR coolers that are automobile parts exposed to exhaust gas-condensate environments.

Assignees

• Nippon Steel & Sumikin Sst

Inventors

• Abe Masatoshi
• Hamada Junichi
• Hiraide Nobuhiko
• Kanno Norihiro
• Fukumoto Shigeo
• Kaneko Shigeru
• HAYASHI Atsutaka

Classifications

• C21D8/02

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

• C22C38/004 Primary

  Very low carbon steels, i.e. having a carbon content of less than 0,01% · CPC title

• C22C38/002

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

• C21D9/46 Primary

  for sheet metals · CPC title

• C21D8/0236

  Cold rolling · CPC title