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.
hot stamping quenching contact pressure microstructure mechanical property
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