Research On Process And Numerical Simulation Of Flux Cored Wire And Pulsed TIG Arc Additive Manufacturing

Wire arc additive manufacturing(WAAM)has the advantages of high forming efficiency,high material utilization,and small part size limitation,and has been widely used in the manufacture of large and complex parts.In this paper,the commercial core wire YJ507-1 with good process and metallurgical properties is selected as the filling wire,and the pulsed TIG arc is the heat source.WAAM platform was designed and built for additive manufacturing experiment.Three groups of low,medium and high heat input parameters are designed for additive manufacturing on the WAAM platform,and the effect of heat input on the macro morphology,microstructure and mechanical properties is studied.The thermal process of additive manufacturing was analyzed and studied by numerical simulation method.Process experiments show that heat input can change the macroscopic morphology and size of the formed part by affecting the interlayer temperature.The layer width of the formed part with high heat input conditions is 5.09 mm and the layer height is 1.73 mm,while the layer width and layer height of the low heat input forming part are 6.49 mm and 1.14 mm.The surface waviness of the formed part is controlled between 2.41 mm and 2.62 mm.The higher the heat input,the better the wettability of the deposited layer and the lower the surface waviness.In the three heat input conditions,the macroscopic morphology quality of the additively manufactured parts is good.The analysis of the microstructure shows that the microstructure is ferrite and pearlite with different morphologies,and the changes in the microstructure are due to differences in the thermal cycles experienced by different layers.The bottom microstructure of low heat input and medium heat input forming parts is acicular ferrite,proeutectoid ferrite and pearlite;while the bottom microstructure of high heat input forming parts is transformed into fine-grained ferrite and pearlite due to thermal cycling.The thermal cycle in the middle region will cause the microstructure to undergo a sufficient solid phase transformation and transform into fine-grained ferrite and pearlite.The top layer has not undergone thermal cycling,and the microstructure is acicular ferrite,proeutectoid ferrite and pearlite.The greater the heat input,the more conducive to the growth of the microstructure.The analysis of mechanical properties shows that the change of microstructure causes the microhardness in the longitudinal section to show a trend of decreasing and then increasing from bottom to top.The maximum microhardness of the low heat input and medium heat input samples at the bottom exceeds 270 HV,and the high heat input sample only reaches 210 HV;the microhardness of the middle area of the three samples is 155 HV?210 HV;The top area has risen compared to the middle area.The shear strength with different heat input conditions are all higher than 260 MPa,and the shear strength of the XY section under the same heat input conditions is about 10% higher than that of the XZ section.With the increase of heat input,the microhardness and shear strength will decrease,but overall the performance of additive manufacturing forming parts in terms of mechanical properties is better.The numerical simulation of additive manufacturing shows that the maximum temperature of the molten pool is stable in the range of 2000 ??2500 ? in different heat input conditions,and the interlayer temperature does not exceed 320 ?.The increase in heat input will lead to an increase in the maximum temperature of the molten pool and the temperature between layers.The thermal cycle of different layers is quite different.As the number of layers increases,the residence time above the austenitizing temperature increases,and the cooling rate decreases,so the solid phase transformation becomes more sufficient.