Numerical Simulation of Temperature Field in Cold Metal Transfer Arc Additive Manufacturing High-Strength Steel

Based on the high-frequency extinguishing characteristics of cold metal transfer (CMT), a dynamic heat source model was established on the basis of the double ellipsoid heat source model. The finite element model of high-strength steel CMT arc additive manufacturing single-pass ten-layer formed part was established by ABAQUS software. The temperature field during the forming was simulated and compared with test results. The influence of interlayer cooling time (30, 60, 90 s) and substrate preheating temperature (20, 200, 300 ℃) on the temperature field was studied by the simulation method. The results show that the trend of the thermal cycle curve at the position 20.5 mm from the center of weld bean on surface of the substrate was basically consistent with the test results, and the relative errors of peak and valley temperatures were both less than 10%, which proved the accuracy of the model. Only the previous layer remelted when the next layer was deposited. During the deposition, the peak temperature of the arc extinguishing end was higher than that of the arc starting end, but the temperature difference between the two ends decreased during cooling. With the extension of interlayer cooling time, the maximum temperature of the molten pool decreased and the existing time of the molten pool became shorter; the cooling rate increased in the cooling stage, but the increase degree decreased the temperature difference between the two ends of the formed part was reduced. The optimum interlayer cooling time was 90 s. With the increase of substrate preheating temperature, the maximum temperature and the size of the molten pool increased, and the maximum valley temperature difference decreased first and then increased. Under the condition of preheating 200 ℃ of the substrate, the maximum valley temperature difference of the formed parts was the smallest, and the temperature distribution was more uniform.