Bearing steel

Patent metadata

Field	Value
Publication number	US-10113221-B2
Application number	US-201615052883-A
Country	US
Kind code	B2
Filing date	Feb 25, 2016
Priority date	Feb 27, 2015
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

A steel alloy for a bearing, the alloy having a composition comprising: (a) from 0.5 to 0.9 wt. % carbon, (b) from 1.2 to 1.8 wt. % silicon, (c) from 1.1 to 1.7 wt. % manganese, (d) from 0.7 to 1.3 wt. % chromium, (e) from 0.05 to 0.6 wt. % molybdenum, and optionally any of: (f 1 ) from 0 to 0.25 wt. % nickel, (f 2 ) from 0 to 0.02 wt. % vanadium, (f 3 ) from 0 to 0.05 wt. % aluminium, (f 4 ) from 0 to 0.3 wt. % copper, (f 5 ) from 0 to 0.5 wt. % cobalt, (f 6 ) from 0 to 0.1 wt. % niobium, (f 7 ) from 0 to 0.1 wt. % tantalum, (f 7 ) from 0 to 150 ppm nitrogen, (f 8 ) from 0 to 50 ppm calcium, and (f 9 ) the balance iron, together with any unavoidable impurities, wherein the steel alloy has a microstructure comprising bainitic ferrite and retained austenite, and a hardness (Vickers) of at least 650 HV.

First claim

What is claimed is:

1. A method of heat treating a bearing component composed of a steel alloy composition that comprises:
0.6 to 0.7 wt. % carbon,
1.3 to 1.7 wt. % silicon,
1.2 to 1.6 wt. % manganese,
0.8 to 1.2 wt. % chromium,
0.15 to 0.4 wt. % molybdenum,
0.05 to 0.25 wt. % nickel,
0.003 to 0.01 wt. % vanadium,
0.005 to 0.05 wt. % aluminium,
0.05 to 0.3 wt. % copper,
0 to 0.5 wt. % cobalt,
0 to 0.1 wt. % niobium,
0 to 0.1 wt. % tantalum,
0 to 150 ppm nitrogen, and
0 to 50 ppm calcium,
the balance being iron and 0.3 wt. % or less of unavoidable impurities,
the method comprising:
(i) heating the steel alloy composition at a temperature of 865-900° C. for 50-100 minutes to at least partially austenitise the composition;
(ii) quenching the steel alloy composition to a temperature of 190-210° C. and holding the steel alloy composition at the temperature of 190-210° C. for 12-36 hours;
(iii) isothermally heating the steel alloy composition at a temperature of 200-280° C. until the steel alloy composition has a microstructure that comprises 5 to 10 vol.% retained austenite and at least 80 vol. % bainitic-ferrite and has a Vickers hardness of at least 650 HV; and
(iv) subjecting the bearing component having 5 to 10 vol.% retained austenite and at least 80 vol. % bainitic-ferrite to a surface finishing technique.

2. The method of claim 1 , wherein the at least 80 vol. % bainitic-ferrite is at least 80 vol. % lower bainite.

3. The method of claim 2 , wherein step (i) is performed at 865-880° C. for 50-100 minutes.

4. The method of claim 3 , wherein step (ii) is performed for 12-16 hours.

5. The method of claim 4 , wherein the steel alloy composition consists of:
0. 65 to 0.7 wt. % carbon,
1.4 to 1.6 wt. % silicon,
1.3 to 1.5 wt. % manganese,
0.9 to 1.1 wt. % chromium,
0.2 to 0.3 wt. % molybdenum,
0.08 to 0.2 wt. % nickel,
0.005 to 0.007 wt. % vanadium,
0.01 to 0.03 wt. % aluminium,
0.1 to 0.2 wt. % copper,
0 to 0.1 wt. % cobalt,
0 to 0.1 wt. % niobium,
0 to 0.1 wt. % tantalum,
0 to 150 ppm nitrogen, and
0 to 50 ppm calcium,
the balance being iron and 0.1 wt. % or less unavoidable impurities.

6. The method of claim 1 , wherein step (i) is performed at 865-880° C. for 50-100 minutes.

7. The method of claim 1 , wherein step (ii) is performed for 12-16 hours.

8. The method of claim 1 , wherein the steel alloy composition consists of:
0.65 to 0.7 wt. % carbon,
1.4 to 1.6 wt. % silicon,
1.3 to 1.5 wt. % manganese,
0.9 to 1.1 wt. % chromium,
0.08 to 0.2 wt. % nickel,
0.01 to 0.03 wt. % aluminium,
0.1 to 0.2 wt. % copper,
0 to 0.1 wt. % cobalt,
0 to 0.1 wt. % niobium,
0 to 0.1 wt. % tantalum,
0 to 150 ppm nitrogen, and
0 to 50 ppm calcium,
the balance being iron and 0.1 wt. % or less unavoidable impurities.

9. The method of claim 1 , wherein the steel alloy composition consists, in wt. %, of 0.67C, 1.53Si, 1.42Mn, 1Cr, 0.12Ni, 0.25Mo, 0.13Cu, 0.006V, and 0.028Al, the balance being iron and unavoidable impurities.

10. The method of claim 9 , wherein the at least 80 vol. % bainitic-ferrite is at least 80 vol. % lower bainite.

11. The method of claim 10 , wherein step (i) is performed at 865-880° C. for 50-100 minutes.

12. The method of claim 11 , wherein step (ii) is performed for 12-16 hours.

Assignees

• Huang Hanzheng
• Sherif Mohamed
• Skf Ab

Inventors

• Huang Hanzheng
• Sherif Mohamed

Classifications

• C22C38/44

  with molybdenum or tungsten · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C21D1/20

  Isothermal quenching, e.g. bainitic hardening · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/48

  with niobium or tantalum · CPC title