Improved Slags for ESR Processing of High-Carbon Chromium Bearing Steel

抄録

Freckles severely affect the quality of high-carbon chromium bearing steel ingots produced by electro-slag remelting (ESR). With conventional slags, reducing the melt rate of the electrode can prevent freckle formation, but severe surface defects can still occur. In order to design an appropriate slag for control of segregation and also improve the surface quality of the ingots, the melting temperature, heat transfer properties, and viscosity of several synthetic slags based on the system CaF₂–CaO–Al₂O₃–MgO were evaluated. As a consequence of the laboratory investigation, a slag with 50% CaF₂ and a CaO/Al₂O₃ ratio of 1.5, was selected as a candidate for validation on ESR production facilities based on the following package of attractive properties: low melting temperature, low break temperature, low viscosity and high thermal conductivity. Following evaluation of the selected slag formulation on full-scale plant trials, HSLA steel ingots were produced that were free from freckles and exhibited good surface quality.