Forming Mix Structure Of High Nitrogen Steel And 316L Stainless Steel By Wire Arc Additive Manufacturing

Wire Arc Additive Manufacturing is based on arc as the heat,welding wire as the adding material,rapidly and directly forming structure parts of high density and accuracy,also excellent mechanical properties,they has the characteristics of high efficiency,short production cycle,high efficiency,etc.The thesis is based on the double wire PMIG welding robot and focuses on high nitrogen steel and 316L stainless steel to analyze the forming characteristics of the materials and the control of the macro geometry size,to develop a multi-bead overlapping stacking test and optimum process parameter selection,and to do research in the forming of the mixed structure of different materials by wire arc additive manufacturing.Firstly,the two kinds of materials were studied on the characteristics of single weld bead forming process,which determined the process parameters of two kinds of materials were determined and found the effect law of process parameters on the macro geometry size of the single weld bead was also studied.For geometric dimensions of single weld bead of high nitrogen steel,the influence of travel speed on the width of single weld bead is greater than that of wire feeding speed;the influence of travel speed on the height of single weld bead is slightly larger than that of wire feeding speed.In terms of geometric dimensions of single weld bead of 316L stainless steel,the influence of wire feeding speed on the width of single weld bead is so much more significant than that of travel speed;the influence of travel speed on the height of single weld bead is more remarkable than wire feeding speed.Secondly,a multi-bead overlap test and optimum process parameters were carried out.The defects of high nitrogen steel multi-bead overlapping stacked were analyzed,and additive manufacturing parameters of high nitrogen steel were further reduced,then analyzing the matching total value of error of the different materials single weld bead geometry and cross sectional area,in order to obtain the most suitable parameters to forming mix structure of different materials by wire arc additive manufacturing,optimum spacing of multi-bead overlapping stacking of different materials is d1*=4.3mm,optimum spacing of multi-bead overlapping stacking of one material is d2*=4.2mm,d3*=4.4mm.Thirdly,the microstructure and mechanical properties of the four kinds of forming mix structure were analyzed.In the interface of different materials,the high nitrogen steel grew along the heat flow direction in the columnar crystal form,and the 316L stainless steel grew by dendrite growth;the microstructure of the remitting zone was affected by the heat twice,and the direction of growth changed twice.To sum up,the larger hardness value of 316L stainless steel gets at the interface of the mix structure,the smaller hardness value of high nitrogen steel will get.If the mix structure maintains high tensile strength,the elongation will increase greatly,and the plastic deformation ability will be improved.For the impact of mix structure,the different orders of the two materials will cause the different ability to absorb impact energy;the different interior of the mixed structure in material distribution and the same proportion of composition results in the same ability to absorb the impact.When the impacts of the front and the side of the hard and soft complex parts have the similar ability,the impact resistance is the strongest.Finally,a 3D model of typical mix structure is established,the divided layer of the proportion of the material composition is designed.A closed planning path was proposed to reduce the arc extinction times,the forming precision of part and entirety of the mix structure is improved,the need of dealing with the processing of waste materials is reduced.The typical mix structure by wire arc additive manufacturing meets the requirements of the specific geometry size.