# US 10,501,819 B2 · High-strength austenitic stainless steel having excellent hydrogen embrittlement resistance characteristics and method for producing same

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- Number: US 10,501,819 B2
- Document ID: US10501819B2
- Status: Granted
- Kind: B2
- Application number: 15/553,514
- Filed: 2016-02-19
- Published: 2018-02-01
- Granted: 2019-12-10
- Earliest claimed: 2015-03-06
- Assignees: Nippon Steel & Sumikin Stainless Steel Corporation
- Applicants: Nippon Steel & Sumikin Stainless Steel Corporation
- Inventors: Kazuhisa Matsumoto; Masaharu Hatano; Shinichi Ohmiya
- Web page: https://patentgrep.com/patent/US10501819B2

## CPC

- C21D 9/46: for sheet metals
- C21D 6/00: Heat treatment of ferrous alloys
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/00: 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)
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides}
- C22C 38/02: containing silicon
- C22C 38/06: containing aluminium
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/54: with boron
- C22C 38/58: with more than 1.5% by weight of manganese
- C21D 2211/001: Austenite
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

This high-strength austenitic stainless steel having excellent hydrogen embrittlement resistance characteristics includes, by mass %, C: 0.2% or less, Si: 0.3% to 1.5%, Mn: 7.0% to 11.0%, P: 0.06% or less, S: 0.008% or less, Ni: 5.0% to 10.0%, Cr: 14.0% to 20.0%, Cu: 1.0% to 5.0%, N: 0.01% to 0.4%, and 0: 0.015% or less, with the balance being Fe and unavoidable impurities, wherein an average size of Cr-based carbonitrides is 100 nm or less, and an amount of the Cr-based carbonitrides is 0.001% to 0.5% in terms of % by mass.

## Claims

### Claim 1

A high-strength austenitic stainless steel comprising, in terms of % by mass:
C: 0.2% or less;
Si: 0.3% to 1.5%;
Mn: 7.0% to 11.0%;
P: 0.06% or less;
S: 0.008% or less;
Ni: 5.0% to 10.0%;
Cr: 14.0% to 20.0%;
Cu: 1.0% to 5.0%;
N: 0.01% to 0.4%; and
O: 0.015% or less,
with the balance being Fe and unavoidable impurities,
wherein an average size of Cr-based carbonitrides is 100 nm or less, and an amount of the Cr-based carbonitrides is 0.001% to 0.5% in terms of % by mass.

### Claim 2 (depends on 1)

The high-strength austenitic stainless steel according to claim 1, further comprising, in terms of % by mass, one or more selected from Mo: 0.5% or less, Al: 0.3% or less, Mg: 0.01% or less, Ca: 0.01% or less, REM: 0.10% or less, B: 0.005% or less, Ti: 0.5% or less, Nb: 0.5% or less, and V: 0.5% or less.

### Claim 3 (depends on 1)

The high-strength austenitic stainless steel according to claim 1, which is used in a high pressure hydrogen gas and liquid hydrogen environment.

### Claim 4 (depends on 1)

A method for producing a high-strength austenitic stainless steel, the method comprising:
a step of hot-working a semi-finished product having a component composition according to claim 1;
a step of performing a final heat treatment at a temperature of 1000° C. to 1150° C.; and
a step of performing cooling after the final heat treatment,
wherein, in the cooling step, an average cooling rate is controlled to be less than 2.0° C/s until the temperature reaches 750° C.;
thereby producing the high-strength austenitic stainless steel of claim 1.

### Claim 5 (depends on 2)

The high-strength austenitic stainless steel according to claim 2, which is used in a high pressure hydrogen gas and liquid hydrogen environment.

### Claim 6 (depends on 2)

A method for producing a high-strength austenitic stainless steel, the method comprising:
a step of hot-working a semi-finished product having a component composition according to claim 2;
a step of performing a final heat treatment at a temperature of 1000° C. to 1150° C.; and
a step of performing cooling after the final heat treatment,
wherein, in the cooling step, an average cooling rate is controlled to be less than 2.0° C/s until the temperature reaches 750° C.;
thereby producing the high-strength austenitic stainless steel of claim 2.