Effect of Austempering and Tempering Temperature on Microstructure of 60Si2CrVA Spring Steel

The effect of austempering temperature and tempering temperature on the microstructure of 60Si2CrVA spring steel was studied by metallurgical microscope observation and analysis under the same experimental conditions of material and heat treatment time.The results show that the undissolved carbides reduce in experimental steel and the content of retained austenite increases with the increase of austempering temperature.The final structure is the upper and lower bainite,residual austenite and a small amount of martensite.The grains of the steel obviously become coarse after quenched at 960 ℃.With the increase of tempering temperature,the microstructure of the tested steel changes from coarsening bainite,residual austenite to tempering flexor,sorbite.The integrated structure morphology is relatively better when the heat treatment process is heating at 910 ℃ for 30 min + isothermal at 300 ℃ for 30 min in molten salt medium + tempering at 420 ℃ for 40 min,oil cold.