Research On The Forming Process Of MAG Arc Additive Manufacturing Variable Thickness Parts For Low Carbon Steel

MAG Wire Arc Additive Manufacture(WAAM)technology has unique advantages in forming large parts with medium complexity and low yield due to its high deposition efficiency and low cost.Arc stability and molten pool stability,as direct factors controlling the MAG-WAAM forming quality,are affected by many process parameters.The influence of process parameters on the shape quality and mechanical properties of the forming parts was studied,which can guide the design of MAG-WAAM forming process.In this thesis,the forming process characteristics of MAG-WAAM were studied using ER50-6 low carbon steel wire as raw material.Firstly,the effect of process parameters on the shape quality and section profile of single-layer single-channel forming parts was studied.The results show that the substrate temperature has little effect on the morphology and size of the weld channel,and the layer height and layer width of the single-pass forming parts increase with the increase of the stacking current and the decrease of the stacking speed.By measuring and fitting the section profile,it is found that WFS/TS(wire feeding speed/stacking speed)< 11.68,best trigonometric function fitting,When WFS/TS>13.69,the fitting result of quadratic function is better,and based on the above fitting results,the optimal pass spacing in single layer multi-channel forming is obtained.Based on the experimental results of single layer and single channel,the circular inclined variable wall thickness parts were formed by alternating stacking of two currents,and the regression equation between variable and response value was established by orthogonal experiment.The results show that the surface quality of circular inclined variable thickness forming parts is the best when the large packing current is 120 A,the small packing current is100 A,and the packing speed is 0.3/min.On this basis,the multi-layer and multichannel circular inclined variable thickness forming parts are successfully prepared with good surface quality.The effect of process parameters on the microstructure and mechanical properties of the forming parts was studied.The microstructure of the single-pass forming parts is mainly strip or block pre-eutectoid α-Fe distributed along the grain boundary,and the internal microstructure of the grain is needle-like α-Fe and a small amount of side strip α-Fe.Single-channel multilayer forming a distinct layers can be observed in the direction of the stacking height with organization,multilayer multichannel forming a cross section is designed in hierarchical organization,the microstructure on the cross section is composed of coarse grain structure,incomplete recrystallization organization and fully recrystallization organization appear alternately,a certain periodic characteristic,and macro morphology in the layer with phenomena and designed corresponding hierarchical organization.With the increase of the packing current and the decrease of the packing speed,the grain size and hardness of the single layer single channel forming parts increase obviously when the other process parameters remain unchanged.When the other process parameters are fixed,the microstructure of the single channel multilayer forming parts has no obvious change with the change of interlayer temperature,and the average grain size increases and the hardness decreases slightly with the increase of the stacking current and the decrease of the stacking speed of the small current.Under different process parameters,forming a uniform mechanical properties,within the scope of the selected forming parameters,as the change of process parameters,forming a no significant changes in mechanical properties,and verified the rationality of single-layer single-channel process parameters and the circular inclined variable thickness forming parts with optimized pass spacing are formed by alternating high and low stacking current.