# US 10,119,185 B2 · Low specific gravity steel for forging use excellent in machineability

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- Number: US 10,119,185 B2
- Document ID: US10119185B2
- Status: Granted
- Kind: B2
- Application number: 13/138,534
- Filed: 2010-04-08
- Published: 2011-12-29
- Granted: 2018-11-06
- Earliest claimed: 2009-04-14
- Assignees: Nippon Steel & Sumitomo Metal Corporation
- Applicants: Hiromasa Takada; Suguru Yoshida
- Inventors: Hiromasa Takada; Suguru Yoshida
- Web page: https://patentgrep.com/patent/US10119185B2

## CPC

- C22C 38/001: {containing N}
- C22C 38/02: containing silicon
- C22C 38/06: containing aluminium
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Steel for forging having high strength and superior machinability due to controlled cooling immediately after shaping by hot forging followed by tempering and having a lower specific gravity than ordinary steel for forging use, the steel containing C: 0.05 to 0.50%, Si: 0.01 to 1.50%, Mn: 3.0 to 7.0%, P: 0.001 to 0.050%, S: 0.020 to 0.200%, Al: 3.0 to 6.0%, Cr: 0.01 to 1.00%, and N: 0.0040 to 0.0200% and having a balance of Fe and unavoidable impurities.

## Claims

### Claim 1

A steel for forging consisting of, by mass%,
C: 0.05 to 0.50%,
Si: 0.01 to 1.50%,
Mn: 5.1 to 5.5%,
P: 0.001 to 0.050%,
S: 0.020 to 0.200%,
Al: 3.6 to 6.0%,
Cr: 0.01 to 0.20%,
N: 0.0040 to 0.0200%, and
having a balance of Fe and unavoidable impurities,
wherein the specific gravity of the steel is 7.44 or less.

### Claim 2

A steel for forging consisting of, by mass%,
C: 0.05 to 0.50%,
Si: 0.01 to 1.50%,
Mn: 5.1 to 5.5%,
P: 0.001 to 0.050%,
S: 0.020 to 0.200%,
Al: 3.6 to 6.0%,
Cr: 0.01 to 0.20%,
N: 0.0040 to 0.0200%, and
one or more of
V: 0.05 to 0.30%,
Nb: 0.05 to 0.30%,
Ti: 0.005 to 0.050%, and
having a balance of Fe and unavoidable impurities,
wherein the specific gravity of the steel is 7.44 or less.

### Claim 3

A forged product obtained by hot-forging a steel ingot consisting of, by mass%,
C: 0.05 to 0.50%,
Si: 0.01 to 1.50%,
Mn: 5.1 to 7.0%,
P: 0.001 to 0.050%,
S: 0.020 to 0.200%,
Al: 3.0 to 6.0%,
Cr: 0.01 to 0.20%,
N: 0.0040 to 0.0200%, and
having a balance of Fe and unavoidable impurities,
wherein −3.3×% C+0.2×% Si−0.31×% Mn+0.17×% Al+0.62≤0 (formula 1), and
wherein the specific gravity of the steel is 7.44 or less.

### Claim 4

A forged product obtained by hot-forging a steel ingot consisting of, by mass%,
C: 0.05 to 0.50%,
Si: 0.01 to 1.50%,
Mn: 5.1 to 7.0%,
P: 0.001 to 0.050%,
S: 0.020 to 0.200%,
Al: 3.0 to 6.0%,
Cr: 0.01 to 0.20%,
N: 0.0040 to 0.0200%, and
one or more of
V: 0.05 to 0.30%,
Nb: 0.05 to 0.30%,
Ti: 0.005 to 0.050%, and
having a balance of Fe and unavoidable impurities,
wherein −3.3×% C+0.2×% Si−0.31×% Mn+0.17×% Al+0.62≤0 (formula 1), and
wherein the specific gravity of the steel is 7.44 or less.