The Prediction of Ferrite Ratio in HAZ of EH36 Steel Electro-Gas Welding Joints Based on Leblond Equation

A favorable microstructure is a perquisite for ensuring the quality of welding joints, but grain coarsing inevitably occurs in the heat-affected zone (HAZ). Controlling the reduction of deterioration as much as possible is a key problem in welding engineering. Based on the welding experiment, a finite element model considering the contact heat transfer of water-cooled sliders is constructed to obtain key information about the welding heat cycle, such as T_8/5, and a prediction algorithm for the microstructure prediction of HAZ is developed based on the Leblond model. The results show that the proportion of ferrite gradually decreases with the increase in cooling rate. The evolution law of the model prediction is the same as that of the experimental results, and the maximum error is within 5%, indicating that the prediction is accurate and reliable. This observation has great significance for the optimization of the electro-gas welding process.