Effect of electrical parameters on type and content of non-metallic inclusions after electro-slag-remelting

This paper describes the effect of different electrical parameters on the type and content of non-metallic-inclusions in the ESR material X38CrMoV5-1. For these investigations, six ingots were remelted with two DC polarities (cathodic and anodic) and with low frequency (1 Hz) AC power supplies under otherwise comparable remelting conditions, in an open laboratory ESR plant. The investigations included automated SEM-analysis combined with EDX. The results show that the cleaning effect of both DC polarities is lower than the one with a low frequency AC power supply, whereas the cathodic DC polarity results in better cleanliness levels than the anodic one. In addition, the oxygen content of the ingots shows a strong increase when remelting with anodic DC polarity. A strong relation between the electric parameters and the types and sizes of inclusion of the ESR ingots could be found. The most pronounced differences occur with the oxide-type inclusions. Thereby, the amount of the originally dominating (Al,Mg)-spinel-type-oxides is further increased when remelting under DC- and AC conditions, but were rather eliminated in favor of Al ₂ O ₃ -type inclusions when DC+ polarity is used. All oxysulfides, except Al-oxysulfides, were strongly decreased or eliminated. Furthermore, a significant reduction of sulfides, especially CaS took place under all electrical parameters. This paper describes the effect of different electrical parameters (DC-, DC+, 1 Hz) during electro-slag-remelting on the type and content of non-metallic-inclusions in the material X38CrMoV5-1, determined by automated SEM-EDX-analysis. Anodic polarity (DC+) leads to an increase in oxygen content and in the size and amount of inclusions, especially of Al ₂ O ₃ -type. One hertz-AC-currents provided the best results with lowest contents in oxides, oxysulfides, and especially sulfides.