Effect of subcritical quenching on mechanical properties of 45 steel for gear shaft

A subcritical quenching test was carried out on 45 steel used for a reduction box gear shaft to enhance its mechanical properties and optimize the design of the reduction box. The effect of undissolved ferrite on mechanical properties of subcritical quenched 45 steel was discussed. The experimental results show that the strength and hardness of 45 steel can reach the maximums when quenched at 790°C. The higher the tempering temperature, the better the toughness of 45 steel. Tempered at 500°C, the toughness of 45 steel increases as the quenching temperature decreases from 810°C to 750°C; however, the strength keeps its high level.