Microstructural Development in AISI 4140 and AISI 1045 Steels during Tempering

This project was designed to develop a fundamental understanding of the effects of induction and furnace tempering process parameters on the microstructure and mechanical properties of induction and furnace tempered parts. In this investigation 304.8mm long by 12.7mm diameter rods of AISI 4140 steel were austenized at 850℃ for 1 hour and quenched in oil. The as-quenched rods were tempered in an atmosphere furnace and by induction at 250℃, 350℃, 450℃, 550℃ and 650℃ for times from 1min to 15hours. The Rockwell hardness of each sample was measured. It was found that Hollomon-Jaffe plots successfully described the tempering behavior of the steel. In addition, the impact toughness and tensile properties were measured. In this paper these experimental results are presented and discussed.