SOME PROBLEMS IN STEEL SHEET FORMING PROCESSES

This paper deals with some problems concerning hardening, heating and softening phenomena in cold forming of some steel sheets such as Hadfi eld steel (1.2% C and 12% Mn) mainly used in the defense industry and low carbon steels (0.06% C and 0.30% Mn) used in automotive industry. The effect on formability of strain rate and temperature arising from deformation is investigated in tensile specimens of Hadfield steel. At high strain rate (2 s(-1)), the maximum measured temperature increase is about 140 degrees C (at the specimen center). Critical strains (ep silon(c)%) are easily determined by using temperature from deformation heating versus time curve obtained during tensile test. Industrial ap plications for bullet proof helmets from Hadfield steel are investigat ed in terms of the variables. Strain rate and temperature dependencies of plastic strain ratio are briefly discussed for low carbon steel sh eets. (C) 1998 Elsevier Science S.A. All rights reserved.