Investigation of nitrovanadium effect instead of ferrovanadium in steel on electrical discharge machinability

Vanadium is used as an alloying element in steel which limits the growth of austenite grains. Moreover, it is a strong carbide and nitride constructor. Vanadium improves yield strength, toughness, hardness and resistance to softening at high temperatures of the material during tempering. Weakens strain aging when combined with Nitrogen. FeV as an additive in steel, is an expensive ferro-alloy. NV composed of nitrogen and vanadium which enhances the strength of the steel. Electrical Discharge Machining (EDM) is a non-traditional production process especially used for machining very hard materials with complex geometries. This processing technique is based on consecutive thermal and energy transition between the work piece and the electrode by electrical sparks in dielectric liquid. Material is removed from the surface through thermal effects of electrical discharges. There are many process parameters like pulse current, pulse duration, pause duration, open gap voltage, pulse form, workpiece, tool electrode and dielectric liquid properties which affect the resultant surface roughness and machinability. Eregli iron and steel works co. carried out trials on sheet steel and coil products to investigate the use of Nitro vanadium instead of FeV for manufacturability of high strength steel and cost savings. In this thesis, two types of alloyed steels are investigated comparatively according to the effect of electrical discharge machining. The effective parameters in electrical discharge machining method and determination of functional surface characteristics are intended. FeV and NV are compared according to analysis. It is observed that, yield and tensile strength of NV alloyed steels are high and percent elongation is low partially. Independently de-iyonized water or kerosene dielectric liquid, alloying technique of steels are not effective on surface roughness when surface roughness of EDM'ed samples are investigated. In SEM analysis, big differences are not observed in terms of surface morphology. It is observed that electrical parameters cannot cause phase change according to XRD analysis. The most important observed result in section microstructure of FeV and NV alloyed steel is the hardness variations on layers which are occurred during EDM. Also, material transition is determined in GDOES measurements according to depth.