Investigation on temperature uniformity of blanks by conduction heating

Abstract

Abstract The austenitizing process of ultra-high strength steel by radiation heating occupied most of the cycle time, which would affect the application of hot stamping in automotive industry. The conduction heating had the advantages of rapid heating, high energy efficiency and good flexibility, which solved the deficiencies of radiation heating. However, the steady temperature distribution of the blanks by conduction heating in the regions closed to the copper electrodes was lower than that of the middle regions, which would affect the mechanical properties of the hot stamping parts. According to the principle of heat transfer, the unequal radiation heat transfer technology was proposed to solve the problem of the inhomogeneous temperature distribution of the blanks. The tests were carried out on the conduction heating test line to investigate the influence of the technology on the steady temperature distribution of the blanks. The results shown that the homogeneous temperature distribution of the blanks was achieved by the local and continuous unequal radiation heat transfer technologies, satisfying the requirement of hot stamping. And the material utilization ratio of the blanks was also improved. The tensile strength, elongation and the balance of strength and ductility of the high temperature regions exceeded 1490 MPa, 6% and 11 GPa•%, respectively. The technology solved the application deficiencies of conduction heating in hot stamping.