# US 4,395,284 A · Abrasion resistant machinable white cast iron

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- Number: US 4,395,284 A
- Document ID: US4395284A
- Status: Granted
- Kind: A
- Application number: 06/340,053
- Filed: 1982-01-18
- Granted: 1983-07-26
- Earliest claimed: 1981-02-20
- Assignees: Falconbridge Limited
- Inventors: Robert J. Dawson
- Web page: https://patentgrep.com/patent/US4395284A

## CPC

- C22C 37/08: with nickel
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A cast iron alloy composition comprising 2.5-3.5% carbon, 0.5-1.0% manganese, 0.25-1.5% silicon, 13-19% chromium, 0.8-3.0% nickel, balance essentially iron which is machinable in the annealed condition and abrasion resistant in the hardened condition. The alloy may be annealed by furnace cooling, at a rate between 100.degree. C. and 350.degree. C./hr., from the austenitizing temperature, and hardened by air cooling from the austenitizing temperature.

## Claims

### Claim 1

A cast iron alloy consisting essentially of about 2.5-3.5% carbon, 0.5-1.0% manganese, 0.25-1.5% silicon, 13-19% chromium, 0.8-3.0% nickel, balance iron and incidental impurities; which is abrasion resistant in the hardened condition and machinable in the annealed condition.

### Claim 2 (depends on 1)

A cast iron alloy as claimed in claim 1 consisting essentially of about 2.8-3.25% carbon, 0.65-0.80% manganese, 0.4-0.75% silicon, 15.2-15.7% chromium, 1.0-2.5% nickel, balance iron and incidental impurities.

### Claim 3 (depends on 1, 2)

An abrasion resistant white cast iron alloy as claimed in claim 1 or 2, heat treated to provide a hardness of at least 60 Rc.

### Claim 4 (depends on 1, 2)

A machinable cast iron alloy as claimed in claim 1 or 2 in an annealed condition and having a hardness of not more than 45 Rc.

### Claim 5

A method of heat treating a cast iron alloy consisting essentially of about:
2.5-3.5% carbon
0.5-1.0% manganese
0.25-1.5% silicon
13-19% chromium
0.8-3.0% nickel
balance iron and incidental impurities,
comprising cooling said alloy at a rate between 100.degree. C. and 350.degree. C. per hour from a temperature above the austenitizing temperature so as to produce an annealed machinable alloy having a hardness of less than about 45 Rc.

### Claim 6

A method of heat treating a cast iron alloy consisting essentially of about:
2.5-3.5% carbon
0.5-1.0% manganese
0.25-1.5% silicon
13-19% chromium
0.8-3.0% nickel
balance iron and incidental impurities,
comprising air cooling said alloy from a temperature above the austenitizing temperature so as to produce an abrasion resistant alloy having a hardness of at least 60 Rc.

### Claim 7 (depends on 5)

A method of heat treating as claimed in claim 5 including heating said annealed alloy to a temperature above the austenitizing temperature and air cooling so as to produce an abrasion resistant alloy having a hardness of at least 60 Rc.

### Claim 8 (depends on 5, 7)

A method of heat treating as claimed in claim 5 or 7 including machining said alloy in said annealed condition.