# US 8,540,932 B2 · Ferritic spheroidal graphite cast iron

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- Number: US 8,540,932 B2
- Document ID: US8540932B2
- Status: Granted
- Kind: B2
- Application number: 13/202,782
- Filed: 2010-02-19
- Published: 2011-12-08
- Granted: 2013-09-24
- Earliest claimed: 2009-02-27
- Assignees: Toyota Jidosha Kabushiki Kaisha; Aisin Takaoka Co., Ltd.
- Applicants: Yoshikazu Genma; Go Kuramoto; Yoshihiro Hibino; Zhong-zhi Zhang; Takeyuki Sakuma
- Inventors: Yoshikazu Genma; Go Kuramoto; Yoshihiro Hibino; Zhong-zhi Zhang; Takeyuki Sakuma
- Web page: https://patentgrep.com/patent/US8540932B2

## CPC

- C22C 37/04: containing spheroidal graphite
- C22C 33/10: including procedures for adding magnesium
- C22C 37/06: containing chromium
- C22C 37/10: containing aluminium or silicon
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Ferritic spheroidal graphite cast iron includes: 3.1 to 3.5 percent by mass of carbon; 4.1 to 4.5 percent by mass of silicon; 0.8 percent by mass or below of manganese; 0.1 to 0.6 percent by mass of molybdenum; 0.1 to 1.0 percent by mass of chromium; 0.03 to 0.1 percent by mass of phosphorus; 0.03 percent by mass or below of sulfur; 0.02 to 0.15 percent by mass of magnesium; and iron.

## Claims

### Claim 1

A ferritic spheroidal graphite cast iron comprising:
3.1 to 3.5 percent by mass of carbon;
4.1 to 4.5 percent by mass of silicon;
0.8 percent by mass or below of manganese;
0.1 to 0.6 percent by mass of molybdenum;
0.1 to 1.0 percent by mass of chromium;
0.03 to 0.1 percent by mass of phosphorus;
0.03 percent by mass or below of sulfur;
0.02 to 0.15 percent by mass of magnesium; and
Iron,
wherein the mass ratio of the content of chromium to the content of molybdenum ranges from 58/30 to 3.5.

### Claim 2 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, wherein ferritizing heat treatment is applied to transform a pearlite structure of a cast iron structure into a ferrite structure.

### Claim 3 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, further comprising unavoidable impurities.

### Claim 4 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, wherein the sum of the product of the content of silicon multiplied by ⅓ and the content of carbon ranges from 4.5 to 5.0 percent by mass.

### Claim 5 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, wherein
the content of manganese is higher than or equal to 0.16 percent by mass, and
the content of sulfur is higher than or equal to 0.002 percent by mass.

### Claim 6 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, wherein the content of molybdenum is higher than or equal to 0.15 percent by mass.

### Claim 7

A manufacturing method for ferritic spheroidal graphite cast iron, comprising:
preparing raw material that includes carbon, silicon, manganese, molybdenum, chromium, phosphorus, sulfur, magnesium and iron;
melting the raw material;
applying graphite spheroidization by adding Fe—Si—Mg alloy to the melted raw material;
inoculating the raw material, which has been subjected to the graphite spheroidization, using Fe—Si; and
casting the inoculated raw material at 1400° C. or above, wherein
the inoculated raw material includes 3.1 to 3.5 percent by mass of carbon, 4.1 to 4.5 percent by mass of silicon, 0.16 to 0.8 percent by mass of manganese, 0.1 to 0.6percent by mass of molybdenum, 0.1 to 1.0 percent by mass of chromium, 0.03 to 0.1percent by mass of phosphorus, 0.002 to 0.03 percent by mass of sulfur, and 0.02 to 0.15 percent by mass of magnesium, and
wherein the mass ratio of the content of chromium to the content of molybdenum in the inoculated raw material ranges from 58/30 to 3.5.

### Claim 8 (depends on 7)

The manufacturing method according to claim 7, further comprising:
maintaining the cast raw material at 750° C. to 950° C. for 2 to 3 hours;
maintaining the raw material, which has been maintained at 750° C. to 950° C., at 500° C. to 750° C. for 3 to 6 hours; and
cooling the raw material that has been maintained at 500° C. to 750° C.

### Claim 9 (depends on 7)

The manufacturing method according to claim 7, wherein the sum of the product of the content of silicon in the inoculated raw material multiplied by ⅓ and the content of carbon in the inoculated raw material ranges from 4.5 to 5.0 percent by mass.

### Claim 10 (depends on 7)

The manufacturing method according to claim 7, wherein the content of molybdenum in the inoculated raw material is higher than or equal to 0.15 percent by mass.

### Claim 11 (depends on 1)

The ferritic spheroidal graphite cast iron according to claim 1, wherein the mass ratio of the content of chromium to the content of molybdenum ranges from 1.97 to 3.45.

### Claim 12 (depends on 7)

The manufacturing method according to claim 7, wherein the mass ratio of the content of chromium to the content of molybdenum in the inoculated raw material ranges from 1.97 to 3.45.