# US 8,540,933 B2 · Stainless austenitic low Ni steel alloy

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- Number: US 8,540,933 B2
- Document ID: US8540933B2
- Status: Granted
- Kind: B2
- Application number: 13/146,221
- Filed: 2010-01-28
- Published: 2012-02-09
- Granted: 2013-09-24
- Earliest claimed: 2009-01-30
- Assignees: Sandvik Intellectual Property AB
- Applicants: Lars Nylöf; Anders Söderman
- Inventors: Lars Nylöf; Anders Söderman
- Web page: https://patentgrep.com/patent/US8540933B2

## CPC

- C22C 38/42: with copper
- C22C 38/001: {containing N}
- C22C 38/02: containing silicon
- C22C 38/58: with more than 1.5% by weight of manganese
- C21D 2211/001: Austenite
- 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

An austenitic stainless steel alloy having the following composition in percent of weight (wt %): 0.02≦C≦0.06; Si<1.0; 2.0≦Mn≦6.0; 2.0≦Ni≦4.5; 17≦Cr≦19; 2.0≦Cu≦4.0; 0.15≦N≦0.25; 0≦Mo≦1.0; 0≦W≦0.3; 0≦V≦0.3; 0≦Ti≦0.5; 0≦Al≦1.0; 0≦Nb≦0.5; 0≦Co≦1.0; the balance Fe and normally occurring impurities, wherein the contents of the alloying elements are balanced so that the following conditions are fulfilled: Nieqv−1.42*Creqv≦−13.42; and Nieqv+0.85*Creqv≧29.00 wherein Creqv=[% Cr]+2*[% Si]+1.5*[% Mo]+5*[% V]+5.5*[% Al]+1.75*[% Nb]+1.5*[% Ti]+0.75*[% W] Nieqv[% Ni]+[% Co]+0.5*[% Mn]+0.3*[% Cu]+25*[% N]+30*[% C]; and −70° C.<MD30<−25° C., wherein MD30=(551−462*([% C]+[% N])−9.2*[% Si]−8.1*[% Mn]−13.7*[% Cr]−29*([% Ni]+[% Cu])−68*[% Nb]−18.5*[% Mo])° C.

## Claims

### Claim 1

An austenitic stainless steel alloy having the following composition in percent of weight (wt %):
0.02≦C≦0.06
Si<1.0
2.0≦Mn≦6.0
2.0≦Ni≦4.5
17≦Cr≦19
2.0≦Cu≦4.0
0.15≦N≦0.25
0≦Mo≦1.0
0≦W≦0.3
0.035≦V≦0.05
0≦Ti≦0.5
0≦Al≦1.0
0≦Nb≦0.5
0.025≦Co≦0.04
the balance Fe and normally occurring impurities,
wherein the contents of the alloying elements are balanced so that the following conditions are fulfilled:
Nieqv−1.42*Creqv≦−13.42; and
Nieqv+0.85*Creqv>29.00
wherein
Creqv=[% Cr]+2*[% Si]+1.5*[% Mo]+5*[% V]+5.5*[% Al]+1.75*[% Nb]+1.5*[% Ti]+0.75*[% W]
Nieqv=[% Ni]+[% Co]+0.5*[% Mn]+0.3*[% Cu]+25*[% N]+30*[% C];
and
−37° C.<MD30<−25° C.
wherein
MD30=(551−462*([% C]+[% N])−9.2*[% Si]−8.1*[% Mn]−13.7*[% Cr]−29*([% Ni]+[% Cu])−68*[% Nb]−18.5*[% Mo])° C.

### Claim 2 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein the contents of the alloy elements in the steel alloy are balanced such that the following condition is fulfilled:
Nieqv−1.42*Creqv≧−16.00.

### Claim 3 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein the contents of the alloy elements in the steel alloy are balanced such that the following condition is fulfilled:
Nieqv+0.85*Creqv≦31.00.

### Claim 4 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein the contents of the alloy elements in the steel alloy are balanced such that the following condition is fulfilled:
Nieqv+0.85*Creqv≦30.00.

### Claim 5 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 0.2≦Si≦0.6 wt %.

### Claim 6 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 2.0≦Mn≦5.5 wt %.

### Claim 7 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 2.0≦Mn≦5.0 wt %.

### Claim 8 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 2.5≦Ni≦4.0 wt %.

### Claim 9 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 17.5≦Cr≦19 wt %.

### Claim 10 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein 0≦Mo≦0.5 wt %.

### Claim 11 (depends on 1)

The austenitic stainless steel alloy according to claim 1 wherein each of W, V, Ti, Al, Nb is ≦0.2 wt %.

### Claim 12 (depends on 1)

The alloy according to claim 1, wherein the amounts of each of the elements W, V, Ti, Al, and Nb≦0.1 wt %, and where
(W+V+Ti+A1+Nb)≦0.3 wt %.

### Claim 13 (depends on 1)

An article comprising the austenitic stainless steel alloy according to claim 1.

### Claim 14 (depends on 13)

The article according to claim 13 wherein the article is a wire, a spring, a strip, a tube, a pipe, or a bar.

### Claim 15 (depends on 13)

The article according to claim 13 wherein the article is an article manufactured by cold-heading or forging.