.7 Cr14mo Vacuum Stainless Bearing Steel, Organizations And Contact Fatigue Life

Small and medium high-precision sensitive stainless bearing steel requires high reliability and long life at the same time, require low noise levels and high accuracy. Stainless bearing steel G95Cr18 is commonly used in China. As the steel has containing high carbon and high chromium content, and prone to large eutectic carbide, and affect the accuracy and life of bearings. And we have developed stainless bearing steel 7Cr14Mo by reducing the content of carbon and chromium in the steel. While ensuring hardness and corrosion resistance at the same time, large eutectic carbide in the steel greatly reduced. The past, smelting process of stainless bearing steel use more the ESR to produce. In this paper, in order to obtain higher-quality materials, using VIM+VAR (double-vacuum) process was to produce stainless bearing steel 7Cr14Mo. And using two types of smelting technology that VIM+ESR(Ar)(ESR(Ar)) and medium frequency induction furnace+ESR(ESR) was comparative study. Explore ways to get it that stainless bearing steel 7Cr14Mo of high metallurgical quality and long life.Through degree of purity, microstructure, carbide, and contact fatigue life of the double-vacuum stainless bearing steel 7Cr14Mo research, results showed that:1 The double-vacuum stainless bearing steel 7Cr14Mo has high degree of purity。Its oxygen content is 0.0005% and the ESR(Ar) steel's is 3.2 times and the ESR steel's is 5.8 times of its. Oxide inclusion content of the double-vacuum steel is 0.00244%, and the ESR(Ar) steel is 1.73 times and the ESR steel is 2.19 times of it. The double-vacuum steel has fewer oxide inclusion and smaller size.2 Quenching-tempering microstructure of the double-vacuum stainless bearing steel 7Cr14Mo is out from cryptocrystalline martensitecanl+retained carbide+retained austenite formed. Sub-structure of martensite matrix is dislocation martensite and twinned acicular martensite mixture of and such organization has high hardness and contact fatigue performance.3 Carbides of the double-vacuum stainless bearing steel 7Cr14Mo is M23C6-type carbide. The maximum carbide of the longitudinal is 25.5μm, and of the lateral is 23.4μm. The average aspect ratio is 1.427. The steel has smaller size carbide and better shape.4 The double-vacuum stainless bearing steel 7Cr14Mo has a high contact fatigue life. Contact fatigue life L10 of the double-vacuum stainless bearing steel 7Cr14Mo is 0.66×107, and its 1.5 times of the ESR(Ar) steel's and 1.65 times of the ESR's.5 The contact fatigue failure mechanism studies have shown that:Contact fatigue failure is jointly controlled by two kinds of mechanism about the Surface-type origin fatigue and the sub-surface origin fatigue and the relationship of them is competition with each other. Inclusions and carbides can be the fatigue crack and affect the contact fatigue life of steel.