Hot tensile and expansion tests of Ductibor (R) 1000 steel

The boron steels present high mechanical properties which are of great interest for lightening the vehicle parts. But these steels, as the Ductibor (R) 1000, need to be hot formed. The hot stamping process consists of a heating/austenization step leading to an increase of the formability, followed by simultaneous forming and quenching steps. In order to understand the thermomechanical and metallurgical cycles occurring during this process, this study focuses on two different test devices at high temperatures using direct resistance heating: a Gleeble 3500 machine for tensile tests and a new bulge test device. The two different tests were performed on the Ductibor (R) 1000 steel for a temperature of 900 degrees C (with temperature holding during deformation) after an austenization step, which consists of heating up to 900 degrees C and a temperature holding stage. The stress-strain curves of the tensile tests obtained using Digital Image Correlation (DIC) are compared to the stress-strain curves of the bulge tests obtained using a laser profilometer and the membrane theory.