Effect of Free Cementite Morphology on Impact Property of S15A Deep Punching Steel

Material notch sensitivity was researched by Charpy impact test for S15A deep punching steel with different free cementite morphology (lamellar free cementite and particle free cementite). The results show that microstructure of S15A deep punching steel in annealing condition was ferrite and free cementite distributing along the ferrite grain boundary. The impact energy of S15A steel with lamellar free cementite was far less than that of the steel with particle free cementite. So the notch sensitivity of the former was more prominent than that of the latter, and the deep punching parts made of S15A steel with lamellar free cementite easily broke when receiving high energy impact load.