Effect of Post-weld Heat Treatment on the Microstructure and Mechanical Properties of 2.25Cr-1Mo-0.25V Ultra-Thick Steel Plate

Ensuring the homogeneous and excellent mechanical properties of 2.25Cr-1Mo-0.25V ultra-thick steel plate is the key to the production of hydrogenation reactor equipment. Thus, it is required to understand the heterogeneity of microstructures and properties of ultra-thick plate after heat treatment. In this work, the effect of post-weld heat treatment (PWHT) on the strength, plasticity, toughness and microstructures of the 193-mm-thick steel plate was investigated, and the formation mechanism of heterogeneity was elucidated. The PWHT decreased the room- and high-temperature yield strength (YS) and ultimate tensile strength (UTS) of the steel plate after normalizing and tempering (NT), while the room- and high-temperature YS and UTS decreased from the surface to the center of 193-mm-thick steel plate. It was attributed to the enhanced decomposition of martensite–austenite (M–A) constituents and coarsening of grains and precipitated carbides.