Control of MgO·Al2O3 Spinel Inclusions during Protective Gas Electroslag Remelting of Die Steel

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2013-04, Vol.44 (2), p.378-389
• Main Authors: Shi, Cheng-Bin, Chen, Xi-Chun, Guo, Han-Jie, Zhu, Zi-Jiang, Sun, Xiao-Lin
• Format: Article
• Language: English
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Exact sciences and technology; Materials Science; Metallic Materials; Metals. Metallurgy; Nanotechnology; Production of metals; Structural Materials; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-012-9780-x

The effect of calcium treatment and/or aluminum-based deoxidant addition on the oxygen control and modification of MgO·Al 2 O 3 spinel inclusions during protective gas electroslag remelting (P-ESR) of H13 die steel with low oxygen content was experimentally studied. It is found that all the inclusions in the consumable electrode are MgO·Al 2 O 3 spinels, besides a few MgO·Al 2 O 3 spinels surrounded by an outer (Ti,V)N or MnS layer. After P-ESR refining combined with proper calcium treatment, all the original MgO·Al 2 O 3 spinels in the electrode (except for the original MgO·Al 2 O 3 spinels having been removed in the P-ESR process) were modified to mainly CaO-MgO-Al 2 O 3 and some CaO-Al 2 O 3 inclusions, both of which have a low melting point and homogeneous compositions. In the case of only Al-based deoxidant addition, all the oxide inclusions remaining in ESR ingots are MgO·Al 2 O 3 spinels. The operation of Al-based deoxidant addition and/or calcium treatment during P-ESR of electrode steel containing low oxygen content is invalid to further reduce the oxygen content and oxide inclusions amount compared with remelting only under protective gas atmosphere. All the original sulfide inclusions were removed after the P-ESR process. Most of the inclusions in ESR ingots are about 2 μ m in size. The mechanisms of non-metallic inclusions evolution and modification of MgO·Al 2 O 3 spinels by calcium treatment during the P-ESR process were proposed.