Effect of Rapid Heating on Microstructure and Tensile Properties of a Novel Coating-Free Oxidation-Resistant Press-Hardening Steel

We explored the feasibility and benefits of rapidly heating (at over 100°C/s) a novel coating-free oxidation-resistant press-hardening steel (PHS). Experiments indicated that a total heating time of 120 s was sufficient to achieve complete austenitization at 930°C with a heating rate of 100°C/s for a 2-mm-thick coating-free PHS blank. Tensile testing results showed that ultimate tensile strength of 1722 MPa and uniform elongation of 5.1% were obtained after rapid heating, soaking, water quenching, and baking, representing a significant improvement over values for the baseline PHS 22MnB5 (1583 MPa and 4.1%) subjected to the same treatment. In addition, the thickness of the oxide layer on the coating-free PHS after rapid heating and soaking (120 s) in ambient atmosphere was less than 5 μm, being much thinner than that on the 22MnB5 (36 μm). Finally, the potential benefits of adopting a rapid heating schedule for the coating-free PHS are discussed.