Abstract
The focus of the study was to define the origin of the inclusions in production-scale electro-slag remelting, (ESR) and electro-slag remelting under a protected pressure controlled atmosphere, (PESR), ingots. The inclusion characteristics in production samples were studied using both polished sample surfaces (two-dimensional (2-D) investigations) and inclusions extracted from steel samples by electrolytic extraction (three-dimensional (3-D) investigations) using SEM in combination with EDS. The results were compared to results from previously reported laboratory-, pilot-, and production-scale trials including electrode, remelted, and conventional ingots. The results show that primary, semi-secondary, and secondary inclusions exist in the remelted ingots. The most probable inclusion to survive from the electrode is a MgO-Al2O3 (spinel). It was also found that the ESR/PESR process slag acts in a similar way to a calcium treatment modification of alumina inclusions. On the whole, the most significant finding is that the overall cleanliness of the electrode including the inclusions in the electrode has an influence on the inclusion content of the ESR and PESR ingots.
Highlights
Due to increased requirements on the final properties of high-quality steels, the limitations on the content of non-metallic inclusions (NMIs) and impurity elements in these steels are continually being tightened
The difference between the electro-slag remelting (ESR) and pressure controlled atmosphere (PESR) processes is that the ESR process here represents a multiple-electrode remelting process, which is performed in a moving mold, in an open furnace under an air atmosphere and using a continuous aluminum deoxidation
The results show that numberofofsmaller smaller oxide is is less in the electrode, (CE-300), that thethe number oxideinclusions inclusions less in the electrode, (CE-300), than in the remelted ingots, (ESR-400 and PESR-500), see Figure 2a
Summary
Due to increased requirements on the final properties of high-quality steels, the limitations on the content of non-metallic inclusions (NMIs) and impurity elements in these steels are continually being tightened. The remelting techniques of electro-slag remelting (ESR) and electro-slag remelting under a protected pressure controlled atmosphere (PESR) produce clean steels with respect to non-metallic inclusion (NMI) content. In industrial size ingots, significantly larger inclusions can be found. For reliable evaluations of the characteristics of NMI (especially larger size inclusions) in industrial-scale ingots, investigations of NMIs carried out only in laboratory and pilot experiments are not sufficient
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