# US 4,391,635 A · High Cr low Ni two-phased cast stainless steel

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- Number: US 4,391,635 A
- Document ID: US4391635A
- Status: Granted
- Kind: A
- Application number: 06/280,237
- Filed: 1981-07-06
- Granted: 1983-07-05
- Earliest claimed: 1980-09-22
- Assignees: Kubota Corporation
- Inventors: Shinichi Murakami; Toshiaki Morichika; Hisashi Hiraishi; Hiroyuki Shiokawa
- Web page: https://patentgrep.com/patent/US4391635A

## CPC

- C22C 38/44: with molybdenum or tungsten
- C22C 38/42: with copper
- C22C 38/48: with niobium or tantalum
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Ferrite-austenitic two-phased stainless steel with high corrosion resistance and toughness containing the following, which may be manufactured easily by furnace melting in the atmosphere composition (by weight %) ______________________________________ C less than 0.10% Si less than 1.5% Mn less than 1.5% P less than 0.04% S less than 0.04% Cr 22-30% Ni 3-6% Mo 0.5-1.5% Cu 0.4-1.0% N less than 0.1% Nb 0.1-0.24% Fe Balance and Creq/Nieq is 3-4.5 Ferrite content is 50-80% ______________________________________

## Claims

### Claim 1

A ferrite-austenitic two-phased cast stainless steel having an impact strength of at least 3 kg-m/cm.sup.2 and containing the following (weight %):
______________________________________ C less than 0.10% Si less than 1.5% Mn less than 1.5% P and S less than 0.4% each Cr 22-30% Ni 3-6% Mo 0.5-0.9% Cu 0.4-1.0% N less than 0.1% Nb 0.1-0.24% Fe balance ______________________________________
wherein values of Ni equivalent and Cr equivalent are calculated by the following equations:
Cr eq=Cr%+Mo%+1.5 Si%+0.5 Nb%
Ni eq=Ni%+0.5 Mn%+30 C%
Cr eq/Ni eq being 3 to 4.5 and ferrite content being 50 to 80%.

### Claim 2 (depends on 1)

The stainless steel of claim 1 containing the following (weight %):
______________________________________ C 0.07% Si 1.18% Mn 0.85% Cr 25.6% Ni 4.1% Mo 0.6% Cu 0.4% N 0.04% Nb 0.12% Fe balance ______________________________________
wherein the Cr eq/Ni eq is 4.2 and the ferrite content is 75%.

### Claim 3 (depends on 1)

The stainless steel of claim 1 containing the following (weight %):
______________________________________ C 0.06% Si 1.05% Mn 0.82% Cr 25.5% Ni 5.1% Mo 0.6% Cu 0.5% N 0.03% Nb 0.24% Fe balance ______________________________________
wherein the Cr eq/Ni eq is 3.7 and the ferrite content is 66%.

### Claim 4 (depends on 1)

The stainless steel of claim 1 containing the following (weight %):
______________________________________ C 0.08% Si 1.10% Mn 0.87% Cr 23.4% Ni 5.2% Mo 0.7% Cu 0.5% N 0.03% Nb 0.22% Fe balance ______________________________________
wherein the Cr eq/Ni eq is 3.2 and the ferrite content is 58%.

### Claim 5 (depends on 1)

The stainless steel of claim 1 containing the following (weight %):
______________________________________ C 0.06% Si 1.08% Mn 0.85% Cr 26.5% Ni 4.5% Mo 0.7% Cu 0.4% N 0.03% Nb 0.23% Fe balance ______________________________________
wherein the Cr eq/Ni eq is 4.3 and the ferrite content is 77%.

### Claim 6 (depends on 1)

The stainless steel of claim 1 containing the following (weight %):
______________________________________ C 0.06% Si 1.02% Mn 0.75% Cr 24.0% Ni 3.8% Mo 0.7% Cu 0.5% N 0.04% Nb 0.20% Fe balance ______________________________________
wherein the Cr eq/Ni eq is 4.4 and the ferrite content is 78%.

### Claim 7

A ferrite-austenitic two-phased cast stainless steel having an impact strength of at least 3 kg-m/cm.sup.2 and containing the following (weight %):
______________________________________ C less than 0.10% Si less than 1.5% Mn less than 1.5% P and S less than 0.04% each Cr 22-30% Ni 3-6% Mo 0.5-0.9% Cu 0.4-1.0% N less than 0.1% Nb 0.1-0.24% Al or Ca or both less than 0.1% Fe balance ______________________________________
wherein values of Ni equivalent or Cr equivalent are calculated by the following equations:
Cr eq=Cr%+Mo%+1.5 Si%+0.5 Nb%
Ni eq=Ni%+0.5 Mn%+30 C%
Cr eq/Ni eq being 3 to 4.5 and ferrite content being 50 to 80%.