The direct hot forming die process is a three-stage approach. After heating up to 950 °C a blank is transferred to the pre-conditioned forming tools. Then the part is formed in an austenitic state. Afterwards the part is quenched in the colder tools. Applying a defined tonnage or engineering a specific gap between tools and the blank heat transfer conditions are adjusted.
During this process stage the temperature in the blank drops from around 950 °C initially down to 200 °C. The average temperature of the tool in use is maintained near 80 °C. During this stage the transformation to a martensitic phase is driven by controlled heat transfer conditions that lead to characteristic cooling curves and therefore to final values for yield strength (YS) and ultimate tensile strength (UTS). Trimming the blank can be executed either directly in the tool or by means of a subsequent laser trim operation.