# US 9,039,961 B2 · Low-nickel austenitic stainless steel

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- Number: US 9,039,961 B2
- Document ID: US9039961B2
- Status: Granted
- Kind: B2
- Application number: 13/643,920
- Filed: 2011-04-18
- Published: 2013-02-14
- Granted: 2015-05-26
- Earliest claimed: 2010-05-06
- Assignees: Outokumpu Oyj
- Applicants: Juho Talonen; Suresh Kodukula; Tero Taulavuori
- Inventors: Juho Talonen; Suresh Kodukula; Tero Taulavuori
- Web page: https://patentgrep.com/patent/US9039961B2

## CPC

- C22C 38/58: with more than 1.5% by weight of manganese
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C22C 38/001: {containing N}
- C22C 38/02: containing silicon
- C22C 38/42: with copper
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)

## Abstract

The invention relates to a low-nickel austenitic stainless steel with high resistance to delayed cracking and the use of the steel. The steel contains in weight % 0.02-0.15% carbon, 7-15% manganese, 14-19% chromium, 0.1-4% nickel, 0.1-3% copper, 0.05-0.3% nitrogen, the balance of the steel being iron and inevitable impurities, and the chemical composition range in terms of the sum of carbon and nitrogen contents (C+N) and the measured Md3o-temperature is inside the area defined by the points ABCD which have the following values Point Md30° C. C+N % A−80 0.1 B+7 0.1 C−40 0.40 D−80 0.40.

## Claims

### Claim 1

Low-nickel austenitic stainless steel with high resistance to delayed cracking wherein the steel contains in weight % 0.02-0.15% carbon, 7-15% manganese, 14-19% chromium, 0.1-4% nickel, 0.1-3% copper, 0.05-0.35% nitrogen, the balance of the steel being iron and inevitable impurities, and a drawing ratio at least 2.0 in deep drawing is achieved to the steel without occurrence of delayed cracking, and the combination of the sum of carbon and nitrogen contents (C+N) and the austenite stability determined by experimentally measured Md30-temperature of the steel is inside the area defined by the points ABCD which have the following values
Point
Md30 ° C.
C + N %
A
−80
0.1
B
+7
0.1
C
−40
0.40
D
−80
0.40.

### Claim 2 (depends on 1)

Low-nickel austenitic stainless steel according to the claim 1, wherein the steel contains 15-17.5% chromium.

### Claim 3 (depends on 1)

Low-nickel austenitic stainless steel according to the claim 1, wherein the steel contains 7-10% manganese.

### Claim 4 (depends on 1)

Low-nickel austenitic stainless steel according to the claim 1, wherein the steel contains 1-2% nickel.

### Claim 5 (depends on 1)

Low-nickel austenitic stainless steel according to claim 1, wherein the steel contains 0.1-2.4% copper.

### Claim 6 (depends on 1)

Low-nickel austenitic stainless steel according to the claim 1, wherein the steel optionally contains at least one of the following group: up to 3% molybdenum, up to 0.5% titanium, up to 0.5% niobium, up to 0.5% tungsten, up to 0.5% vanadium, up to 50 ppm boron and/or up to 0.05% aluminum.

### Claim 7 (depends on 1)

Low-nickel austenitic stainless steel according to claim 1, wherein the yield strength Rp0.2 is higher than 260 MPa and the ultimate tensile strength Rm is higher than 550 MPa.

### Claim 8 (depends on 1)

Low-nickel austenitic stainless steel according to claim 1, wherein the elongation to fracture A80 mm is higher than 40%.

### Claim 9 (depends on 1)

Low-nickel austenitic stainless steel according to claim 1, wherein the pitting resistance equivalent PRE is higher than 17.

### Claim 10 (depends on 1)

Low-nickel austenitic stainless steel according to claim 1, wherein a drawing ratio at least 2.0 in deep drawing is achieved to the steel without occurrence of delayed cracking, and the combination of the sum of carbon and nitrogen contents (C+N) and the austenite stability determined by experimentally measured Md30-temperature of the steel is inside the area defined by the points DEFG which have the following values
Point
Md30 ° C.
C + N %
D
−80
0.40
E
−80
0.2
F
−20
0.2
G
−53
0.40.