Influence of thermal properties on KIHTC in hot forming

Abstract:

To study the factors which can influce the thermal properties of both die and specimen, calculate the Interfacial Heat Transfer Coefficient(KIHTC) during hot stamping process is very important. A round table test and Beck′s inverse estimation method were used to study the relationship between the thermal properties and the KIHTC. The dies were made of materials with different thermal conductivity and heat capacity. The thermal properties in terms of martensite transformation were obtained by using specimen made of 22MnB5 sheet. Specimen made of stainless steel AISI-304 that does not have martensite transformation during quenching were tested as well for comparison. The results show that the KIHTC between boron steel specimen and die of ＃45 Steel is larger than that of H13 Steel (approximately twice as much) and the thermal conductivity plays a significant role; the martensite transformation yields a positive gain on KIHTC (approximately by 30.2％) and the change in thermal conductivity before and after phase transformation is a major contributor.