Based on various thermodynamic models of phase transformation, the thermal model of acicular ferrite transformation in 10Ni5CrMoV steel weld was calculated. The driving force of weld metal transformation was calculated to reveal the mechanism of austenite transforming into acicular ferrite in 10Ni5CrMoV steel weld. The traditional diffusion model, pearlite transformation model and carbon lean zone shear model were used to explore the thermodynamic transformation mechanism. The results show that the lower the carbon contents in the original austenite, the greater the driving force of the acicular ferrite transformation. When the temperature of the austenite transforming into acicular ferrite reduces, the activity of carbon atoms in the carbon poor zone increases, and the growth driving force of acicular ferrite improves, which is conducive to the formation of acicular ferrite. The driving force of acicular ferrite transformation at 700 K was about 6.1 times of that at 950 K. Based on thermodynamic calculation, it is inferred that acicular ferrite is formed mainly in the form of shearing transition in carbon poor zone. It's a better process choice to increase the content of acicular ferrite by prolonging the residence time of medium temperature transformation during welding process.
LI Dayong，YANG Dongqing，WANG Ping，et al.Analysis of microstructure and properties of 10Ni5CrMoV steel joint welded with high chromium nickel austenitic welding wire［J］.Transactions of the China Welding Institution，2017，38（05）：87-91.