Some problems in steel sheet forming processes

摘要

This paper deals with some problems concerning hardening, heating and softening phenomena incold forming of some steel sheets such as Hadfield steel (1.2% C and 12% Mn) mainly used in thedefense industry and low carbon steels (0.06% C and 0.30%) Mn) used in automotive industry. Theeffect on formability of strain rate and temperature arising from deformation is investigated in tensilespecimens of Hadfield steel. At high strain rate (2 S{sup}- 1), the maximum measured temperatureincrease is about 140℃ (at the specimen center). Critical strains (ε{sub}c%) are easily determinedby using temperature from deformation heating versus time curve obtained during tensile test.Industrial applications for bullet proof helmets from Hadfield steel are investigated in terms of thevariables. Strain rate and temperature dependencies of plastic strain ratio are briefly discussed for lowcarbon steel sheets.