Experimental Study Of EDM Characteristics And Surface Defects Of Nitrogenous Mould Steel

In order to meet the requirement of the development of mould, mouldmaterial industry introduced new kind of steel, which can improve theadvantages of steel evidently. The nitrogen plastic mould steel is developeddue to some deficiency in practical industrials so as to improve thetoughness and the corrosion resistance of the material. EDM is an efficientmethod to solve this problem, But with conventional EDM parameters tomachine the materials, the machining in finish stage is a big issue. Even so,sometimes, there produce some surface defects such as surface cavities,cracks, porosity, and etc. meanwhile, the problems in finish machining candecrease the cutting speed, increase electrode wear and deteriorate thequality of machining surface, therefore, cost of machining, the dimensionalprecision and the surface roughness are impacted as well. What’s more,surface defects can make the mould materials prematurely failure, thus, theservice life of the material is decreased seriously. So, it is necessary that tostudy the EDM characteristics and the surface defects of the nitrogenousmould steel.This paper mainly studied the EDM characteristics of nitrogenousmould steel by experimental method and then discussed the influence of thepeak current, pulse-on duration, parasitic capacitance, and the combinationof nitrogen and other alloyed elements on the processing surface crack andthe porosity. The research results show that the higher the nitrogen contentof the steel, the faster processing speed, the smaller the electrode wear, theworse quality of the processing surface; chromium can easily form the crackof EDMed surface, both nitrogen and chromium elements exist in the steelcan increase processing surface cracks, but the combination of nitrogen and molybdenum elements can reduce processing surface crack; under the givenexperimental condition in this paper, porosity only exists on the processingsurface of steel material that contains nitrogen, and the higher the nitrogencontent in the material, the more porosity on the processing surface; In thesubtle processing, the larger capacitance value, the more cracks and porosityon the processing surface.