Bearing steel material with excellent rolling contact fatigue properties and a bearing part

Patent metadata

Field	Value
Publication number	US-9394593-B2
Application number	US-201214008628-A
Country	US
Kind code	B2
Filing date	Mar 5, 2012
Priority date	Mar 31, 2011
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

Bearing steel material according to the present invention has: a properly adjusted chemical composition; an average chemical composition of oxide-inclusions which comprises 10 to 45% of CaO, 20 to 45% of Al 2 O 3 , 30 to 50% of SiO 2 , up to 15% (exclusive of 0) of MnO, and 3 to 10% of MgO, with the balance being unavoidable impurities; a maximum major axis diameter of the oxide inclusions in a longitudinal section of the steel material of 20 μm or less; and a spheroidal cementite structure.

First claim

The invention claimed is:

1. A bearing steel material, comprising:
by mass%,
from 0.8% to 1.1% of C;
from 0.15% to 0.8% of Si;
from 0.10% to 1.0% of Mn;
up to 0.05%, excluding 0%, of P;
up to 0.01%, excluding 0%, of S;
from 1.3% to 1.8% of Cr;
from 0.0002% to 0.005% of Al;
from 0.0002% to 0.0010% of Ca;
up to 0.0030%, excluding 0%, of O; and
iron,
wherein
an average chemical composition of oxide-inclusions in the bearing steel material is, by mass%: from 10% to 45% of CaO; from 20% to 45% of Al 2 O 3 ; from 30% to 50% of SiO 2 ; up to 15%, excluding 0%, of MnO; and from 3% to 10% of MgO;
a maximum major axis diameter of the oxide-inclusions in a longitudinal section of the bearing steel material is 20 μm or less; and
the bearing steel material has a spheroidal cementite structure.

2. The bearing steel material according to claim 1 ,
wherein the bearing steel material is obtained by being subjected to cold working at a working ratio of 5% or more after spheroidizing annealing.

3. The bearing steel material according to claim 1 , wherein the maximum major axis diameter of the oxide-inclusions in the longitudinal section of the bearing steel material is 18 μm or less.

4. The bearing steel material according to claim 1 , wherein the maximum major axis diameter of the oxide-inclusions in the longitudinal section of the bearing steel material is 16 μm or less.

5. The bearing steel material according to claim 1 , which comprises from 0.0007 to 0.0010 mass% of Ca.

6. A bearing part, comprising:
the bearing steel material according to claim 1 .

7. A bearing part, comprising:
The bearing steel material according to claim 2 .

Assignees

• Kaizuka Masaki
• Nagahama Mutsuhisa
• Shimamoto Masaki
• Sugimura Tomoko
• Kobe Steel Ltd

Inventors

• Kaizuka Masaki
• Nagahama Mutsuhisa
• Shimamoto Masaki
• Sugimura Tomoko

Classifications

• C22C38/02

  containing silicon · CPC title

• C22C38/18 Primary

  containing chromium · CPC title

• C22C29/12

  based on oxides · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/04

  containing manganese · CPC title