The effect of carbon content on the change in mechanical properties of carbon steels subjected to shock pressure.

Abstract

The effect of shock pressure on the stress-strain behavior of four plain carbon steels with 0.06, 0.17, 0.44 and 0.85 wt % C was investigated. The shock pressure was generated in water by an explosive. The shock pressure effect was compared with the effect of pressurizing or temper rolling on the stress-strain behavior. Susceptibility to twinning caused by the shock loading was also examined in the steels with different carbon content. Results obtained in this investigation are summarized as follows. The yield stress of three steels except for 0.85 wt % C steel began to decrease at the shock pressure of 300 MPa and continued to decrease to the minimum with increasing pressure. However, the yield stress of 0.85 wt % C steel was never lowered by the shock pressure. For the steel with larger carbon content, the amount of decrease in the yield stress became smaller and the shock pressure which minimized the stress became higher. Yield ratios of the steels containing 0.06, 0, 17 and 0.44 wt % C, which had the original ratios of 0.65, 0.65 and 0.53 respectively, were reduced to 0.38∼0.40 by the shock loading, On the other hand, the ratio 0.37 of 0.85 wt % C steel was not lowered. The shock pressure (Ps)t at which the mechanical twins began to be formed in the specimen increased linearly from 720MPa for 0.06 wt % C steel to 3100 MPa for 0.85 wt % C steel with increasing carbon content. The pressure (Ps)t did not always depend on the yield stress value. Twin density defined as the ratio of number of crystal grains with twins to total number of grains was smaller in the steel with larger carbon content and the density monotonously increased with increasing shock pressure. The decrease of the yield stress by the shock loading was considerably larger than the decrease in the cases of pressurizing and temper rolling.