Effect of Contact Pressure during Quenching on Microstructures and Mechanical Properties of Hot-stamping Parts

An experimental apparatus with cooling system and pressure-adjustment assembly for simulating quenching was constructed to investigate the effect of contact pressure on the microstructures and mechanical properties of hot-stamping parts. Qualitative and quantitative analyses of the microstructures of the as-quenched parts were conducted; moreover, hardness and tensile tests were performed to measure their mechanical properties. The results indicated that contact pressure during quenching strongly affected the structures and performances of hot-stamping components. An excessive low contact pressure led to insufficient martensitic transformation. The critical contact pressure for complete martensitic transformation for 4.0 mm 22MnB5 steel was 0. 4 MPa when the temperature of the coolant was 20 °C. However, in consideration of the efficiency of practical production, a contact pressure higher than 1.25 MPa is recommended.