Delayed Fracture Behavior of CrMo Type High Strength Steel Containing Vanadium

摘要

The effect of microalloying element vanadium on hydrogen-induced delayed fracture behavior of quenched and tempered low alloy CrMo type steel in Walpole aqueous solution was investigated. The sustained load tensile test was carried out by using notched tensile specimens. The experimental results show that the suitable addition of vanadium is effective in improving delayed fracture resistance. The finely dispersed precipitation of vanadium carbide causes a significant secondary hardening, so the tempering temperature of steel containing vanadium is higher than that of the base steel at the same strength level. This homogeneously distributed carbide acts as strong hydrogen trap, thus retards the diffusion and accumulation of hydrogen and avoids the entering of hydrogen into stress concentration site. These beneficial effects of vanadium carbide are the main reasons for the improvement of delayed facture resistance of steel containing vanadium. Furthermore, the fine prior austenite grain of steel with suitable addition of vanadium is also an important factor for the improvement.