Research On Temperature Field,Stress Field And Forming Process Of The Stainless Steel Arc Addictive Manufacturing Based On CMT

The arc and wire additive manufacturing,using arc as the heat source and wire as the cladding material,fabricate metal components of high density and excellent mechanical properties rapidly.It can greatly improve the material utilization and the production efficiency.The core competitiveness was strengthen with shorter production cycle.Based on stainless steel addictive manufacturing technology using CMT,the research on the temperature field,the stress field,the addictive manufacturing process and the micro structure and properties is carried out on stainless steel straight wall structures in this paper.The temperature field and stress field during the addictive manufacturing process were studied.A finite element model is established based on SYS WELD.The temperature field and stress field of three kinds of commonly used methods of arc addictive manufacturing are compared,which are manufactured by the continuous manufacturing of the same direction,the S shaped continuous manufacturing and the time increment of the S shape.The result show that the substrate has a great influence on the cooling rate of the first four cladded layer and the number of the layer can be influenced by the substrate is irrelevant with addictive manufacturing method.The temperature of the cladded layer is stable after cladding a certain number of layers on it.The stable temperature is below the sensitizing temperature range of the austenitic stainless steel,and the lower stable temperature value can be obtained by controlling the interlayer temperature.The heat accumulating effect of CMT is not obvious.The residual stress of the austenitic stainless steel is larger than the yield strength.The residual stress and deformation of the straight wall structures is larger by the method of continuous manufacturing of the same direction.The residual stress in the S-shaped continuous manufacturing is characterized by the large stress distribution in the smaller region,while the control layer temperature is smaller in the larger area,and all exhibit symmetrical distribution.The reheating effect in the manufacturing process is equivalent to the tempering heat treatment,which reduces the residual stress in the cladding layer.The mathematic model of shielding gas flow,wire feeding speed,cladding speed with forming wall thickness was established by MATLAB software.The model shows that the higher the wire feed speed is,the bigger the wall thickness is,and when the wire feed speed exceeds 4.0m/min,the wall thickness increase rate is obviously slowed down.When the air flow rate is interacted with the wire feed speed,thick influence is more obvious.The influence of three factors on the forming wall thickness is as follows:wire feed speed =cladding speed>shield gas flow rate.The microstructures and mechanical properties of S shaped continuous addictive manufacturing and S shaped interval time addictive manufacturing are compared.The microstructures in the straight wall were divided into six regions according to the different thermal cycling processes.The first and second regions were the bottom and bottom transition regions,and the residual ferrite had more dendrites.The fusion zone formed between the cladding layers contains a small amount of austenite columnar.The ? region is the middle stable forming region with less ferrite and smaller dendrites.The ? region and the VI are the top transition region and the top region.Ferrite content is more.The residual ferrite content of the corresponding region is increased by controlling the inter-layer temperature.The tensile strength of the formed straight wall is up to 70%of that of 304 annealed stainless steel substrate,which is higher than that of cast and hot rolled state.The impact resistance reaches 65%of the substrate,and the hardness is equivalent to that of the substrate.Transverse and longitudinal pulling tensile strength,impact resistance and plasticity showed no significant difference.Controling the temperature between the layers of stainless steel had a small impact on the mechanical properties of straight wall.