| Bearing and gear is key components in mechanical manufacturing equipment. Thetraditional heat treatment is carburizing and quenching. In the surface with high hardnessand high carbon martensite structure,and low carbon martensite with high toughness in thecenter.The toughness of bainite is better than martensite structure.A method was proposedto obtain bainite in low-carbon steel. The samples were carburized in a gas carburizingfurnace.The carbonized samples were heated for austenitization and then austempered insalt bath.The holding time for austemper is from2h to48h. The microstructures withindifferent depth of carburized steel were investigated by optical microscopy.With thepotential use of bearing and gears,the samples were shotted peening.Firstly,in this article, seven kinds of carburizing bearing steel20Cr2Ni4SiMoAl waschosed as the research object. by adopting different carburizing process and heat treatmentprocess, according to the hardness distribution of seeping layer, the carbon contentdistribution, the depth of effective hardening layer, organization and mechanical properties,the best carburizing heat treatment process and the optimum composition was selected,which provide important basis for the application in bearing.In this paper，a method was proposed to obtain bainite after isothermal quenching inlow-carbon carburized heavy-load gear steel, and shot peening in the bainite steelsurface. The microstructure and properties of the bainite also have been investigated. Withthe potential use of heavy-load gear, the property of wear was also tested.The samples of20H after isothermal transformation at200℃for8h and230℃for4h was shotted peening,the microstructure and properties also have beeninvestigated.The result show that shot peening can increase the surface hardness between50~70HV, effective hardening layer is about0.5mm, organization is more small, theresidual austenite content is significantly less.Accordingly, shot peening has obviouseffects for increasing surface strength and comprehensive mechanical properties. |
