Influence of subcritical quenching process on microstructure and mechanical properties of 45 steel

Influence of pre-heat treatment and subcritical quenching temperature on microstructure and mechanical properties of 45 steel was investigated through pre-heat treatment+subcritical quenching+tempering.The results show that mechanical properties of the steel depend on shape and quantity of retained ferrite after subcritical quenching.If quenching+high temperature tempering was used for pre-heat treatment,the retained ferrite became fine and needle-shape and mechanical properties of the steel increased after subcritical quenching.If annealing was used for pre-heat treatment the retained ferrite became coarse and mechanical properties of the steel decreased.With the subcritical quenching temperature increasing,the quantity of retained ferrite reduces and the strength and hardness of the steel are enhanced and the plasticity and toughness are decreased.Comparing with the conventionally quenching process,higher mechanical properties of 45 steel can be obtained by proper subcritical quenching process.