# US 4,396,442 A · Ductile cast iron roll and a manufacturing method thereof

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- Number: US 4,396,442 A
- Document ID: US4396442A
- Status: Granted
- Kind: A
- Application number: 06/263,903
- Filed: 1981-05-15
- Granted: 1983-08-02
- Earliest claimed: 1981-05-15
- Assignees: Kubota Corporation
- Inventors: Shiro Nakamura; Masahiro Fukuda; Akitoshi Okabayashi
- Web page: https://patentgrep.com/patent/US4396442A

## CPC

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

## Abstract

The present invention relates to a ductile cast iron roll which is excellent in its resistance breaking and which has the chemical composition comprising 3.0-3.8% C, 1.5-2.5% Si, 0.2-1.0% Mn, 0.01-0.2% P, less than 0.06% S, 0.7-3.0% Ni, 0.1-0.6% Cr, 0.1-0.8% Mo, 0.02-0.1% Mg, balance iron and unavoidable impurities and the base structure having a fine two-phase structure of ferrite mingled with pearlite. The cast iron roll is manufactured by holding the said cast iron roll at the temperature 780.degree..about.850.degree. C. for less than 20 hours; and after that by cooling the same down to 760.degree. C. at the cooling speed 50.about.300.degree. C./Hr; and after that by holding the same at the temperature 450.degree..about.650.degree. C. for less than 20 hours.

## Claims

### Claim 1

A ductile cast iron roll having a base structure of a composition comprising 3.0 to 3.8% C, 1.5 to 2.5% Si, 0.2 to 1.0% Mn, 0.01 to 0.2% P, less than 0.06% S, 0.7 to 3.0% Ni, 0.1 to 0.6% Cr, 0.1 to 0.8% Mo, 0.02 to 0.1% Mg, all percents being weight %, the balance iron and unavoidable impurities, said base structure characterized by being substantially a two-phase structure of ferrite and pearlite.

### Claim 2 (depends on 1)

A ductile cast iron roll as described in claim 1 wherein a Al less than 0.3% is contained in the said cast iron.

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

A ductile cast iron roll as described in claim 1 or 2 wherein a total of 0.05% of rare earth elements are added to the said cast iron.

### Claim 4 (depends on 1)

A ductile cast iron roll as described in claim 1, further containing calibers, wherein the hardness of the bottom surface of said calibers is higher by Hs 1-5 than that of the flange portion which is on the same radius as the said bottom surface.

### Claim 5

A method of manufacturing a ductile cast iron roll, said roll produced from a cast iron having a composition comprising 3.0 to 3.8% C, 1.5 to 2.5% Si, 0.2 to 1.0% Mn, 0.01 to 0.2% P, less than 0.06% S, 0.7 to 3.0% Ni, 0.1 to 0.6% Cr, 0.1 to 0.8% Mo, 0.02 to 0.1% Mg, all percents being weight %, balance iron and unavoidable impurities, said method comprising holding the cast iron at a temperature of 780.degree. to 850.degree. C. for less than 20 hours, cooling to 600.degree. C. at a cooling speed of 50.degree. to 300.degree. C./Hr, and then maintaining at 450.degree. to 650.degree. C. for less than 20 hours.

### Claim 6 (depends on 5)

The method of claim 5 wherein said cast iron contains, in addition, a positive amount of aluminum of less than 0.3% by weight.

### Claim 7 (depends on 5)

The method of claim 5 wherein said cast iron contains, in addition, a positive amount of rare earth elements in an amount of less than 0.5% by weight.

### Claim 8 (depends on 5)

The method of claim 5 further including calibers, said calibers formed prior to said heat treatment.

### Claim 9

A ductile cast iron roll having a base structure of a composition comprising 3.0 to 3.8% C, 1.5 to 2.5% Si, 0.2 to 1.0% Mn, 0.01 to 0.2% P, less than 0.06% S, 0.7 to 3.0% Ni, 0.1 to 0.6% Cr, 0.1 to 0.8% Mo, 0.02 to 0.1% Mg, all percents being weight %, the balance iron and unavoidable impurities, said base structure characterized by being substantially a two-phase structure of ferrite and pearlite and having a tensile strength in the range of 54 to 62.1 kg/mm.sup.2 and an elongation percent of 1.9 to 2.9.