Effect of Rapid Induction Tempering on the Mechanical Properties and Microstructure of Ultra-High Strength Steel

Rapid induction can be utilized to decrease the time and energy used for heat-treatment of steels. In the present study, a commercial 500 HB grade wear-resistant steel was subjected to rapid induction tempering and compared to conventionally furnace tempered samples. The martensitic ultra-high strength steel was cut to narrow thin sheets, which were tempered at 200, 300, 400, and 500 °C with both methods. The rapid tempering was applied with an in-house built induction line, in which the samples were moved through an induction coil. The velocity of the samples was adjusted to ensure constant temperature control. The applied heating rate was 1000–1100 °C/s resulting in extremely rapid tempering times. The conventionally tempered samples were heated in a pre-heated furnace for 45 min and cooled in still air. The samples were tested for tensile and hardness properties and microstructural characterization was conducted. Results revealed only minor differences between the differently treated steels. Elongation was slightly improved with the induction treatment. Therefore, the induction tempering appeared to result in similar or even slightly better tensile properties and can be considered a promising alternative for tempering processes in future steelmaking.