| Wire electrical discharge machine(WEDM) technology plays an irreplaceablerole in mold manufacturing, hard materials processing, as well as precise, complexand irregular-shape parts processing etc. Compared with traditional processingmethods, the mold materials with WEDM technology are seldom wasted because onlylittle amount of metal corrodes due to the principle of discharge corrosion, and theprocess becomes more stable as well. Considering that the quality of mold processingdirectly affects the life of mold, selecting the electrical parameters of WEDM is veryimportant in order to ensure the surface quality of mold parts in the processing.Choosing7CrSiMnMoV steel, the normal mold material in Huangyan mold industry,as the study objects, this research investigated the influence law of the electricalparameters on the technical index, and the composition, pattern and the formationmechanism of the outer deteriorated layer.From the background of WEDM as the starting point, differences andadvantages of WEDM compared with other processing methods are detailed. Thetheory, the physical nature, the influence factors and the principle for wire selection ofWEDM processing are systematically discussed. The current research situation andfuture trends in the WEDM technology field are also concluded in the beginning ofthis paper.According to the research target, we designed four factors and three levels oforthogonal experiment regarding to the predetermined electrical parameters,analyzing the number of tube amplifiers, pulse width, pulse interval and no-loadvoltage, for the influence law of the samples dimensional accuracy, surface roughnessand white layer thickness. Through range and variance analysis, the primary andsecondary orders of each influence factors were determined and the best combinationof electrical parameters was obtained. At the same time significance analysis for eachfactor was conducted using F-test. In comprehensive consideration of themulti-process indicators, the optimal combination values of electrical parameters were ultimately determined.On this basis, proceed the comparative test research, a clad layer ofNi60+30%WC metal alloy powder with thickness of1±0.03mm was prepared in theupper and lower surfaces of7CrSiMnMoV steel by laser cladding process, AfterWEDM processing. Analyzed the relationship between processing electricalparameters and each process indicators, as well as the electrical parameters combinedvalue of single process indicators and multi-process indicators optimized, and werecompared and analyzed for each process indicators of laser cladding befor and after.At the same time, observed the binding of laser cladding layer and the substratematerial, and analyzed the microhardness and phase of cladding layer.Moreover, the surface morphology and organization of the WEDM parts wereobserved and analyzed. By X-ray diffraction analysis of processing samples it wasfound that the type of Mo compounds increased in the sample surface. Some of thesesubstances were from the material itself, while the others were partly from thecombination of the vaporized melting work piece material with the Mo elements ofthe wire electrode, since the wire electrode and the work piece surface melted andvaporized due to the instant high temperature generated by spark discharge. Byobserving the metallographic structure of sample’s cross section, we can see the whitelayer portion of affected layer, which is with clearly boundary from the matrixmaterial and is easy to be measured. It is also found that the sample surface appearedwith micro-cracks and micro-porous after WEDM. The formation mechanism of thesemicro-cracks and micro-porous were analyzed and concluded, and some appropriatepreventive measures were proposed. |
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