On the plastic region produced by an impact compression in a quenched and tempered steel specimen.

Abstract

Steel prismatical specimens were struck by a falling weight of 5.19 kg under a constant drop height of I m in order to determine the effects of heat-treatment and length of specimens on the appearance of the plastic zone and plastic strain in a specimen of finite length by an impact compression. Length of specimens used were 20, 40 and 60 mm. All specimens were quenched after heating at 850°C for 0.5 hr and tempered at 400, 500, 600 and 700°C, or annealed at 650°C for 1.5 hr. The theoretical relation between the plastic zone length and plastic strain in a specimen were estimated based on the plastic wave propagation in a specimen, and the influences of specimen length and of strain hardening on plastic strain were discussed. The plastic strain values measured experimentally coincide well with the values calculated by the equation with the plastic zone length measured for a large strain hardening specimen. Swelling over the plastic zone and microhardness distribution along the centre line of the specimen surface were studied. According to the morophorogic observation on the plastic zone which appeared on a specimen surface using a SEM, it was determined that there existed not only a slip in a ferrite grain but also a gap along the grain boundary between two pearlite grains near the top end of the annealed specimen.