Combined hot stamping and Q&P processing with a hot air partitioning device

Combining the hot stamping process and a Quench and Partition (Q&P) heat treatment can improve the mechanical properties of hot stamped automotive parts. This paper investigates using a new heating device to heat or cool a part to a given temperature. Instead of performing the partitioning heat treatment in a furnace, this work proposes using a new hot air process that performs the partitioning treatment. The new device obtains a fast heating rate and a uniform temperature distribution, necessary for Q&P. The effect of partitioning time and temperature on the mechanical properties of parts were analyzed by the new processing method, which is suitable for use in the area of industrial hot stamping. The results show that the hot air partitioning device provides more control over the partitioning temperature because convection is more efficient than radiation. Control over the quench temperature and partition is critical for the Q&P process to enable the carbon diffusion to stabilize the austenite. Furthermore, the highest product of strength and elongation (1380 MPa × 13%) using the hot air process under the authors' set-up condition is obtained when the partitioning time is 60 s and the temperature is 425 °C, thanks to the optimum ratio between martensite and austenite, which was observed through scanning electron microscopy.