Simulation of heat treatment of jominy specimen to improve quality of automotive gear components

摘要

Microstructure and mechanical performance play a key role for gear box reliability. According standard quality assu- rance procedure steel grade analysis is a fundamental base to identify correct mechanical properties achievable after heat treatment cycle. With the aim to make more robust production cycle of gear box components, samples are cut from parts and Jominy test is performed on this specimen. In case of small components like gears, specimen for Jominy test cannot be obtained and the only approach to validate process is supplier certificate obtained on steel before heat treatment. Quenchability of component can be different from data reported on nominal supplier datasheet with the risk to have failure during testing or exercise of gear box; tests on failed parts demonstrated that chemical composition variation, notwithstanding inside allowed range, drove to lower mechanical performance according microstructure not properly quenched.In order to validate heat treatment cycle, microstructure and mechanical properties, Jominy test has been virtualized into heat treatment simulation software. Real Jominy tests have been transferred inside simulation software for diffe-rent steel grades used for automotive gear box application. A model to forecast microstructure and mechanical pro- perties for Jominy specimen is built and benchmarked with experimental data. Alignment between simulation results and reality allows to transfer model definition from Jominy samples to complete real components, improving quality assurance capability for real process thanks to usage of heat treatment cycle virtualization for gear box realized with different steel grades.