Influence of Second Thermal Cycle on Reheat Cracking Susceptibility of Welding CGHAZ in Vanadium-Modified 2.25Cr1Mo Steel

The welding coarse grained heat affected zones (CGHAZ) of Vanadium-modified (V-mod) 2.25Cr1Mo steel are prone to reheat cracking because of its poor ductility in the temperature range of intermediate stress relief treatment (650∼680 ̊C). Considering the multiple-pass welding procedure of V-mod 2.25Cr1Mo steel, the microstructure, high temperature ductility and reheat cracking susceptibility of the CGHAZ subjected to second welding thermal cycle with different peak temperatures (Tp2) were studied by the thermal simulation technique. The results show that the high temperature ductility of double-cycle CGHAZs with all second peak temperature (730 ̊C, 890 ̊C, 1020 ̊C, 1250 ̊C) exhibits recovery in comparison to the single-cycle CGHAZ. Under the condition of Tp2=890 ̊C and Tp2=1020 ̊C, the recrystallization of prior austenite grains in CGHAZ results in a remarkable elevation of the high temperature ductility and a significant reduction of the reheat cracking susceptibility.