Ferritic stainless steel sheet exhibiting small increase in strength after aging heat treatment, and method of producing the same

Patent metadata

Field	Value
Publication number	US-10513747-B2
Application number	US-201414773988-A
Country	US
Kind code	B2
Filing date	Mar 14, 2014
Priority date	Mar 14, 2013
Publication date	Dec 24, 2019
Grant date	Dec 24, 2019

Abstract

A ferritic stainless steel sheet containing, by mass %, C: 0.020% or less, Cr: 10.0% to 25.0%, N: 0.020% or less, Sn: 0.010% to 0.50%, and one or more of Ti: 0.60% or less, Nb: 0.60% or less, V: 0.60% or less, and Zr: 0.60% or less so as to satisfy Equation (1): (Ti/48+V/51+Zr/91+Nb/93)/(C/12+N/14)≥1.0, wherein a difference between a stress σ1 (N/mm2) after prestrain imparting tensile deformation with 7.5% of strain, and an upper yield stress σ2 (N/mm2) when the steel sheet is subjected to heat treatment at 200° C. for 30 minutes and then to tension again after the tensile deformation is 8 or less.

First claim

The invention claimed is:

1. A ferritic stainless steel sheet comprising, as a steel composition, by mass %:
C: 0.020% or less;
Si: 0.01% to 2.0%;
Mn: 2.0% or less;
P: less than 0.050%;
S: less than 0.010%;
Cr: 10.0% to 25.0%;
N: 0.020% or less;
Sn: 0.010% to 0.50%;
Ca: 0.0003% to 0.0030%;
Ga: 0.0003% to 0.0021%;
one or more of Ti: 0.60% or less, Nb: 0.60% or less, V: 0.60% or less, and Zr: 0.60% or less so as to satisfy the following Equation (1); and
a balance being Fe and inevitable impurities,
wherein a stress σ1, in N/mm 2 , when 7.5% of strain is applied and an upper yield stress σ2, in N/mm 2 , after the steel sheet is subjected to a heat treatment at 200° C. for 30 minutes satisfy the following Equation (2), and the stress σ1 and the upper yield stress σ2 are measured by a method which includes, in series: taking a tensile test piece from the steel sheet in a direction parallel to a rolling direction; subjecting the tensile test piece to tensile deformation with 7.5% of strain to measure the stress σ1; subjecting the tensile test piece to the heat treatment at 200° C. for 30 minutes; and subjecting the tensile test piece to tensile deformation to measure the upper yield stress σ2:
(Ti/48+V/51+Zr/91+Nb/93)/(C/12+N/14)≥1.0  Equation (1)

σ2−σ1≤8  Equation (2),

wherein in Equation (1), each element name represents the amount, in mass %, thereof and the amount of an element not contained in the steel is substituted by 0.

2. The ferritic stainless steel sheet according to claim 1 , further comprising, by mass %,
Al: 0.003% to 1.0%.

3. The ferritic stainless steel sheet according to claim 1 , further comprising, by mass %, one or more of,
Ni: 0.01% to 2.0%,
Cu: 0.01% to 2.0%, and
Mo: 0.01% to 2.0%.

4. The ferritic stainless steel sheet according to claim 1 , further comprising, by mass %, one or more of,
B: 0.0003% to 0.0025%,
Mg: 0.0001% to 0.0030%,
Sb: 0.001% to 0.50%,
REM (rare earth metal): 0.002% to 0.2%, and
Ta: 0.005% to 0.50%.

5. The ferritic stainless steel sheet according to claim 2 , further comprising, by mass %, one or more of,
Ni: 0.01% to 2.0%,
Cu: 0.01% to 2.0%, and
Mo: 0.01% to 2.0%.

6. The ferritic stainless steel sheet according to claim 2 , further comprising, by mass %, one or more of,
B: 0.0003% to 0.0025%,
Mg: 0.0001% to 0.0030%,
Sb: 0.001% to 0.50%,
REM (rare earth metal): 0.002% to 0.2%, and
Ta: 0.005% to 0.50%.

7. The ferritic stainless steel sheet according to claim 3 , further comprising, by mass %, one or more of,
B: 0.0003% to 0.0025%,
Mg: 0.0001% to 0.0030%,
Sb: 0.001% to 0.50%,
REM (rare earth metal): 0.002% to 0.2%, and
Ta: 0.005% to 0.50%.

Assignees

• Nippon Steel & Sumikin Sst

Inventors

• Kimura Ken
• Hamada Junichi
• Ishimaru Eiichiro
• Yamagishi Akihito
• Hansaki Naoto

Classifications

• C21D8/00 Primary

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/004

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

• C22C38/001

  containing N · CPC title

• C22C38/24

  with vanadium · CPC title

• C22C38/26

  with niobium or tantalum · CPC title