Influence of slag composition on the cleanliness of electroslag ingot during low frequency electroslag remelting

Electroslag remelting (ESR) experiments were performed on 304L austenitic stainless steel using a laboratory-scale low-frequency electroslag furnace with Al2O3-CaO-CaF2 and Al2O3-CeO2-CaF2 slags of varying compositions. The study aimed to evaluate the influence of slag composition on the oxygen and nitrogen content, as well as the number, size, and types of inclusions in ESR ingots under low-frequency power supply conditions. The results demonstrated that, under low-frequency conditions, increasing the CaO or CeO2 content while decreasing Al2O3 in the slag significantly reduced the oxygen content in the ingots. Among the slag components, CaO exhibited a markedly stronger deoxidation effect than CeO2 under identical conditions. Regardless of slag type, the nitrogen content in the ingots remained stable. In the Al2O3-CaO-CaF2 system, higher CaO content decreased the number and size of inclusions and shifted their type from Al2O3 to aluminum-calcium composite inclusions. Similarly, in the Al2O3-CeO2-CaF2 system, a 15% CeO2 content reduced the inclusion size and number, leading to the formation of cerium-containing composite inclusions. The micro-electrolysis of slag components under low-frequency power supply was identified as the primary mechanism influencing inclusion characteristics, with slag stability playing a pivotal role in determining inclusion distribution and number in the ingots. Consequently, careful slag composition selection is essential for optimizing low-frequency ESR processes.