Spheroidal graphite cast iron

Patent metadata

Field	Value
Publication number	US-11466349-B2
Application number	US-201816233535-A
Country	US
Kind code	B2
Filing date	Dec 27, 2018
Priority date	Jan 11, 2018
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

A spheroidal graphite cast iron having an excellent impact strength at low temperature and a method for producing the same are provided. The present disclosure relates to the spheroidal graphite cast iron comprising: C: 3.5 mass % to 4.2 mass %; Si: 2.0 mass % to 2.8 mass %; Mn: 0.2 mass % to 0.4 mass %; Cu: 0.1 mass % to 0.7 mass %; Mg: 0.02 mass % to 0.06 mass %; Cr: 0.01 mass % to 0.15 mass %; and the balance: Fe and inevitable impurities, wherein Mn+Cr+Cu is 0.431 mass % to 1.090 mass %, a graphite nodule count is 230/mm2 or less, and a pearlite fraction is 30% to 85%.

First claim

What is claimed is:

1. A spheroidal graphite cast iron comprising:
C: 3.5 mass % to 4.2 mass %;
Si: 2.0 mass % to 2.8 mass %;
Mn: 0.2 mass % to 0.4 mass %;
Cu: 0.1 mass % to 0.4 mass %;
Mg: 0.02 mass % to 0.06 mass %;
Cr: 0.01 mass % to 0.15 mass %; and
the balance: Fe and inevitable impurities,
wherein Mn+Cr+Cu is 0.431 mass % to 1.090 mass %, a graphite nodule count is 230/mm 2 or less, and a pearlite fraction is 30% to 56%.

2. The spheroidal graphite cast iron according to claim 1 , comprising Cr in an amount in the range of from 0.01 mass % to 0.035 mass %.

3. The spheroidal graphite cast iron according to claim 1 , having a tensile strength in the range of from 490 MPa to 750 MPa.

4. The spheroidal graphite cast iron according to claim 1 , having a tensile strength in the range of from 490 MPa to 644 MPa.

5. The spheroidal graphite cast iron according to claim 1 , having a 0.2% yield strength in the range of from 320 MPa to 440 MPa.

6. The spheroidal graphite cast iron according to claim 1 , having a 0.2% yield strength in the range of from 320 MPa to 369 MPa.

7. A method for producing the spheroidal graphite cast iron according to claim 1 , comprising:
(i) a preparation step of preparing a molten cast iron, and
(ii) a cooling step comprising:
(a) a first cooling step comprising cooling the molten cast iron prepared in (i) from a pouring temperature to a temperature at A1 transformation point in an iron-carbon phase diagram at a cooling rate of 15° C./min to 25° C./min; and
(b) a second cooling step comprising, upon reaching the temperature at A1 transformation point in the first cooling step, cooling from the temperature at A1 transformation point to a temperature at which no further transformation of iron takes place in the spheroidal graphite cast iron at a cooling rate of 10° C./min to 20° C./min.

Assignees

• Hijii Takumi
• Ureshino Yoshimasa
• Sakuma Hitoshi
• NAKAMURA Gou
• Zhang Zhong Zhi
• Toyota Motor Co Ltd
• Aisin Takaoka Ltd

Inventors

• Hijii Takumi
• Ureshino Yoshimasa
• Sakuma Hitoshi
• NAKAMURA Gou
• Zhang Zhong-Zhi

Classifications

• C22C37/04 Primary

  containing spheroidal graphite · CPC title

• C21C1/10

  Making spheroidal graphite cast-iron · CPC title

• C22C33/08

  Making cast-iron alloys · CPC title

• C22C33/10

  including procedures for adding magnesium · CPC title

• C22C37/06

  containing chromium · CPC title