GM-20 CARBURIZING OF BIG MODULE AND LARGE DIAMETER GEARS(GEAR MANUFACTURING)

Abstract

The carburizing gears have higher strength and better life-time compared with induction-hardening or quench-tempered gears, but in big-module gears, the carburizing heat-treatment becomes time-consuming, cost-expensive and sometimes cannot achieved good hardness due to the big mass-effect, and it is not easy to reduce the distortion of gears during heat treatment. In order to achieve good surface hardness of carburizing layer, it is necessary to precisely control the carbon content distribution. Since the carburizing time is much longer for big module gears due to deeper case-depth requirement, after carburizing it is necessary to have intermediate cooling under 650℃ to get finer grain size and better mechanical properties. By using a carburizing furnace equipped with fast cooling function, the work-pieces can proceeding intermediate cooling and heat up again to quench temperature inside the same furnace. This can reduce the total heat-treatment time as well as costs remarkably. The distortion comes from heat treatment is not avoidable, by improving the arrangement of load we can reduce the distortion and then reduce the manufacturing costs.