# US 9,518,313 B2 · High strength, high toughness steel alloy

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- Number: US 9,518,313 B2
- Document ID: US9518313B2
- Status: Granted
- Kind: B2
- Application number: 13/645,596
- Filed: 2012-10-05
- Published: 2013-02-14
- Granted: 2016-12-13
- Earliest claimed: 2008-07-24
- Assignees: CRS Holdings, Inc.
- Applicants: CRS Holdings, Inc.
- Inventors: Paul M. Novotny
- Web page: https://patentgrep.com/patent/US9518313B2

## CPC

- C22C 38/42: with copper
- C21D 6/004: {containing Cr and Ni}
- C21D 7/13: by hot working
- 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 9/0068: {for particular articles not mentioned below}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/04: containing manganese
- C22C 38/34: with more than 1.5% by weight of silicon
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C21D 1/32: Soft annealing, e.g. spheroidising
- 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

A high strength, high toughness steel alloy is disclosed. The alloy has the following weight percent composition. Element C 0.30-0.47 Mn 0.8-1.3 Si 1.5-2.5 Cr 1.5-2.5 Ni 3.0-5.0 Mo + ½ W 0.7-0.9 Cu 0.70-0.90 Co 0.01 max. V + ( 5/9) × Nb 0.10-0.25 Ti 0.005 max. Al 0.015 max. Fe Balance Included in the balance are the usual impurities found in commercial grades of steel alloys produced for similar use and properties including not more than about 0.01% phosphorus and not more than about 0.001% sulfur. Also disclosed is a hardened and tempered article that has very high strength and fracture toughness. The article is formed from the alloy having the broad weight percent composition set forth above. The alloy article according to this aspect of the invention is further characterized by being tempered at a temperature of about 500° F. to 600° F.

## Claims

### Claim 1

A steel alloy consisting essentially of, in weight percent, about:
C
0.30-0.40
Mn
0.8-1.3
Si
1.9-2.5
Cr
1.5-2.5
Ni
3.0-4.5
Mo + ½ W
0.7-0.9
Cu
0.70-0.90
Co
0.01 max.
V + ( 5/9) × Nb
0.10-0.25
Ti
0.005 max.
Al
0.015 max.
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
14.5≦(% Si+% Cu)/(% V+(5/9)×% Nb)≦34.

### Claim 2 (depends on 1)

The alloy claimed in claim 1 which contains not more than about 1.2% manganese.

### Claim 3 (depends on 1)

The alloy claimed in claim 1 which contains at least about 1.0% manganese.

### Claim 4 (depends on 1)

The alloy claimed in claim 1 which contains at least about 1.7% chromium.

### Claim 5 (depends on 1)

The alloy claimed in claim 1 which contains at least about 3.1% nickel.

### Claim 6 (depends on 1)

The alloy as claimed in claim 1 which contains not more than about 2.2% silicon.

### Claim 7 (depends on 1)

The alloy as claimed in claim 1 which contains at least about 0.32% carbon.

### Claim 8 (depends on 1)

The alloy as claimed in claim 1 which contains not more than about 1.2% manganese.

### Claim 9 (depends on 1)

The alloy as claimed in claim 1 which contains not more than about 0.85% copper.

### Claim 10 (depends on 6)

The alloy as claimed in claim 6 wherein % V+(5/9)×% Nb is at least about 0.14%.

### Claim 11 (depends on 1)

The alloy as claimed in claim 1 wherein % V+(5/9)×% Nb is not more than about 0.22%.

### Claim 12 (depends on 1)

A quenched and tempered steel article formed from the steel alloy claimed in claim 1 wherein said steel article provides a room temperature tensile strength of at least about 290 ksi in combination with a fracture toughness (KIc) of at least about 70 ksi√in.

### Claim 13 (depends on 12)

The quenched and tempered steel article claimed in claim 12 wherein the article comprises a structural component for an aircraft.

### Claim 14 (depends on 13)

The quenched and tempered steel article claimed in claim 13 wherein the structural component comprises landing gear.