Phase transformations in a simulated hot stamping process of the boron bearing steel

• We experimentally simulate a hot stamping process by a deformation dilatometer.
• We investigate the phase transformations and hardness changes due to hot stamping.
• The effect of hot stamping on transformation is strongly dependent on cooling rate.
• The CCT and DCCT diagrams of elaborated steel were constructed and compared.

A hot stamping process was experimentally simulated by a hot deformation dilatometer to investigate phase transformations and final properties of 22MnB5 boron\bearing steel. For this purpose, the phase fraction in the microstructure of boron bearing steel with and without hot deformation was evaluated. The results showed that mechanical stabilization of austenite during the deformation process led to decreased amount of military phases while bainite and reconstructive transformations, especially ferrite were promoted. But, when there was no martensite in the final microstructure, the effect of deformation on ferrite formation was negligible. Also, due to deformation, total hardness was decreased in cooling rates of higher than 6 °C/s. But, on the contrary, in cooling rates of lower than 6 °C/s, remarkably reverse results were achieved. Finally, the CCT and DCCT diagrams of elaborated steel were constructed.

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