Steel Having Superior Rolling Fatigue Life

Patent metadata

Field	Value
Publication number	US-2016201174-A1
Application number	US-201414909795-A
Country	US
Kind code	A1
Filing date	Aug 7, 2014
Priority date	Aug 8, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

There is provided a steel, having an excellent rolling fatigue life, wherein an oxygen content in the steel is 8 ppm or less, a sulfur content is 0.008 mass % or less, and an Al content is 0.005 to 0.030 mass %, the number of non-metallic inclusions having an inclusion diameter of 20 μm or more and less than 100 μm, detected per steel material volume of 1000 mm 3 by ultrasonic flaw detection, is 12.0 or less, the number of non-metallic inclusions having an inclusion diameter of 100 μm or more, detected per steel material weight of 2.5 kg by the ultrasonic flaw detection, is 2.0 or less, the mass % ratio of (MgO)/(Al 2 O 3 ) in the average composition of MgO—Al 2 O 3 -based oxides present in the steel is regulated into a range of 0.25 to 1.50, and the number ratio of the MgO—Al 2 O 3 -based oxides to all oxide-based inclusions is 70% or more.

First claim

1 . A steel having an excellent rolling fatigue life, the steel used in a mechanical part having a surface hardness of 58 HRC or more, wherein an oxygen content in the steel is, in mass percentage, 8 ppm or less, a sulfur content is 0.008 mass % or less, and an Al content is 0.005 to 0.030 mass %;
a number of non-metallic inclusions having an inclusion diameter of 20 μm or more and less than 100 μm, detected per steel material volume of 1000 mm 3 by ultrasonic flaw detection, is 12.0 or less; a number of non-metallic inclusions having an inclusion diameter of 100 μm or more, detected per steel material weight of 2.5 kg by ultrasonic flaw detection, is 2.0 or less; a mass % ratio of (MgO)/(Al 2 O 3 ) in an average composition of MgO—Al 2 O 3 -based oxides present in the steel is regulated into a range of 0.25 to 1.50; and a number ratio of the MgO—Al 2 O 3 -based oxides to all oxide-based inclusions is 70% or more.

2 . The steel having an excellent rolling fatigue life according to claim 1 , wherein
the oxygen content in the steel is, in mass percentage, 6 ppm or less, and the sulfur content is 0.003 mass % or less; the number of the non-metallic inclusions having an inclusion diameter of 20 μm or more and less than 100 μm, detected per steel material volume of 1000 mm 3 by ultrasonic flaw detection, is 9.0 or less; and the number of the non-metallic inclusions having an inclusion diameter of 100 μm or more, detected per steel material weight of 2.5 kg by ultrasonic flaw detection, is 1.5 or less.

3 . The steel having an excellent rolling fatigue life according to claim 1 , wherein
the number of the non-metallic inclusions having an inclusion diameter of 20 μm or more and less than 100 μm is evaluated by detecting a flaw in a total volume of 1500 mm 3 or more by the ultrasonic flaw detection; and the number of the non-metallic inclusions having an inclusion diameter of 100 μm or more is evaluated by detecting a flaw in a total weight of 3.0 kg or more by the ultrasonic flaw detection.

4 . The steel having an excellent rolling fatigue life according to claim 1 , wherein
the steel is: a high-carbon chromium bearing steel specified in JIS standard; 52100 specified in SAE standard or ASTM standard A295; 100 Cr6 specified in DIN standard; a carbon steel for machine structural use specified in JIS standard; or an alloy steel for machine structural use, which is any one steel selected from chromium steels, chromium-molybdenum steels, and nickel chrome molybdenum steels.

5 . The steel having an excellent rolling fatigue life according to claim 2 , wherein
the number of the non-metallic inclusions having an inclusion diameter of 20 μm or more and less than 100 μm is evaluated by detecting a flaw in a total volume of 1500 mm 3 or more by the ultrasonic flaw detection; and the number of the non-metallic inclusions having an inclusion diameter of 100 μm or more is evaluated by detecting a flaw in a total weight of 3.0 kg or more by the ultrasonic flaw detection.

6 . The steel having an excellent rolling fatigue life according to claim 2 , wherein
the steel is: a high-carbon chromium bearing steel specified in JIS standard; 52100 specified in SAE standard or ASTM standard A295; 100 Cr6 specified in DIN standard; a carbon steel for machine structural use specified in JIS standard; or an alloy steel for machine structural use, which is any one steel selected from chromium steels, chromium-molybdenum steels, and nickel chrome molybdenum steels.

7 . The steel having an excellent rolling fatigue life according to claim 3 , wherein
the steel is: a high-carbon chromium bearing steel specified in JIS standard; 52100 specified in SAE standard or ASTM standard A295; 100 Cr6 specified in DIN standard; a carbon steel for machine structural use specified in JIS standard; or an alloy steel for machine structural use, which is any one steel selected from chromium steels, chromium-molybdenum steels, and nickel chrome molybdenum steels.

Assignees

• Sanyo Special Steel Co Ltd

Inventors

• Fujimatsu Takeshi
• Tsunekage Norimasa
• Takasu Ichiro

Classifications

• C22C38/44 Primary

  with molybdenum or tungsten · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title

• C22C38/00 Primary

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C21D9/40

  for rings; for bearing races · CPC title