Study On Process And Property Of Mold By Wire And Arc Additive Manufacturing

Based on the dispersion-deposition principle,the technology of wire and arc additive manufacturing(WAAM)used arc as the heat source to melt the welding wire and deposited metal to build three-dimensional solid mold component up along the specific path in a layer by layer fashion.Compared with the traditional mold manufacturing process,WAAM not only has the advantages of lower cost,less material loss,shorter cycle of design and manufacturing,but also realize the manufacture of advanced mold with gradient materials.Therefore,it possessed great scientific significance and engineering application to study the basic process and theory of WAAM technology,and to explore the feasibility of its application in mold manufacturing.In this paper,a welding system of the digital robot based on Cold Metal Transfer welding process(CMT)is established by using ER80S-G(AWS standard)and MF6-55GP(DIN 8555 standard)welding wire as the research object.It researched the forming process,the surface quality,the microstructure and mechanical properties of the forming parts by WAAM.It laid a foundation for ensuring the stability,dimensional accuracy and component performance of the forming process.Firstly,it used MF6-55GP welding wire to investigate the influence of welding process parameters on weld forming size by orthogonal test.It optimized the mathematical model of curve profile of single seam by function fitting,calculated the optimal theoretical lap between the seams,and discussed the change rule of the seam.The influence of forming path and interlayer temperature on the surface quality of surfacing parts is also analyzed.The results shown that welding speed has the greatest influence on the width and height of weld seam,wire feed speed is the most important factor for the increase of weld height.The actual profile curve of first seam has the highest goodness-of-fit with circular curve model under different welding parameters.Affected by first seam,the actual profile curve of second seam has the highest goodness-of-fit with parabola curve model,it given the best welding surface by using the combination lap model of circular curve and parabola curve.Moreover,the increase of interlayer temperature will lead to the deterioration of surface quality,and deposition in the reverse directions can effectively improve the uplift at the arcing zone and the collapse at the arc-extinguishing zone.Secondly,it used the ER80S-G welding wire as the matrix material and the MF6-55GP welding wire as the main material.It studied the microstructure and mechanical properties of bimetal composite material by WAAM.The results shown that the microstructure of ER80S-G deposited metal is composed of pearlite,ferrite and a small amount of granular bainite.It is a plastic material which Vickers hardness is 235.1HV and yield strength of compression is 466.55MPa.The microstructure of MF6-55GP deposited metal is composed of martensite,tempered sorbite upper bainite and a small amount of retained austenite and dispersed carbides.It is a hard and brittle material which Vickers hardness is 695.5 HV and compressive strength is 3172.20MPa.The friction and wear properties of MF6-55GP deposited metal are close to Cr12MoV mold steel.The hardness of the bimetallic layer is obviously changed at the interface,the deposited metal of ER80S-G is more prone to yield deformation under compressive stress,and the deposited metal of MF6-55GP is more prone to fracture under tensile stress.There is no fatigue crack in the interface of the bimetallic layer in the yield strength of ER80S-G after 107 cycles of the compression fatigue performance tests.Finally,through the reasonable path planning and the welding process parameters,the simple mold unit component was manufactured by WAAM,and the feasibility of this technology for mold manufacturing is verified.