Effects of Different Slag Systems and Equilibrium Time on the Element Burning Loss and Inclusion Characteristics of the C-HRA-3 Alloy

Author of the article:LI Longfei1 , LIN Tengchang1 , HE Xikou2 , CHEN Zhengzong2 , YAO Tonglu1 , MENG Huadong1

Author's Workplace：1. Department of Metallurgical Technology Research, Central Iron and Steel Research Institute, Beijing 100081, China; 2. Institute for Special Steels, Central Iron and Steel Research Institute, Beijing 100081, China

Key Words：： C-HRA-3 alloy; electroslag remelting; slag-metal equilibrium; element burning loss; inclusion

Abstract：In this paper, the changes in element content and inclusion characteristics in C-HRA-3 alloy under three different 6-system slags, CaF2-Al2O3-CaO-MgO-TiO2-ZrO2, and five different slag-metal equilibrium times of 20~180 min were investigated by metallurgical principles, FactSage thermodynamic calculations and scanning electron microscopy. The results show that the contents of Al, Ti and Zr in the C-HRA-3 alloy decrease, while the content of Si increases, and the B content maintains a small range of fluctuations after the slag-metal equilibrium experiment. When the equilibrium reaction time is within 0~40 min, the contents of Al and Ti are 14.29% and 20.59%, respectively, lower than the original content, and the Zr content changes maximally and decreases by 54.55%. As the equilibrium time exceeds 40 min, the contents of Al, Ti and Zr fluctuate at a low level. The increase in equilibrium time can reduce the number of inclusions in the C-HRA-3 alloy and has little effect on the average diameter of inclusions and the proportion of different sizes. The inclusions mainly consist of spherical or near-spherical Al2O3 and MgO and TiN with edges and corners. Moreover, large primary carbides easily precipitate from the matrix during solidification. Through research and analysis, SiO2 and other impurities should be strictly controlled in the slag, and TiO2 and ZrO2 components should be properly added to the slag in the process of electroslag remelting of C-HRA-3 alloy. It is necessary to add Al into the metal bath, maintain a good smelting protective atmosphere and improve the cooling intensity of the electroslag ingot.