Evolution of Inclusions in Steelmaking Process of Rare Earth Steels Containing Arsenic with Alumina Crucibles

Hongpo Wang,Peng Yu,Yu Wang,Silu Jiang,Lifeng Sun,Bin Bai

doi:10.3390/met10020275

Abstract

In order to determine strategies for removing arsenic from rare earth arsenic-containing steels, the evolution of inclusions in the whole steelmaking process with alumina crucibles was investigated. It has been proven that adding lanthanum has a significant effect on both the existing state and content of arsenic in steel. The content of arsenic steeply decreased after adding 0.148% lanthanum by generating La–S–As inclusions. The addition of 0.054% lanthanum did not dramatically affect the content of arsenic. Both 0.148% and 0.054% additions of lanthanum modified the existing Si–Mn–Al–O inclusions, making them first change to La-containing inclusions, and then change back to Si–Mn–Al–O inclusions. During this process, the compositions of inclusions changed from (SiO2–MnO)-rich to Al2O3-rich ones, owing to the reactions between lanthanum and alumina crucibles. The addition of 0.148% lanthanum resulted in a relatively severe reaction with the alumina crucible. This led to the decomposition of a part of the existing La–S–As inclusions and a slight increase in the arsenic content. Therefore, it is noted that choosing an appropriate holding time after adding rare earth elements to molten steel has a significant effect on the arsenic removal and saving the consumption of rare earth elements.

Highlights

The trace elements arsenic, tin, lead, antimony, and bismuth have been considered the five most harmful trace elements to steel products, especially for the high-temperature mechanical properties [1,2,3,4,5]. They come mainly from steel scrap and iron ores containing these elements, and cannot be removed from steel in the mainstream oxidation steelmaking process. This problem is serious in China because of the lack of high-quality iron ore resources; on the contrary, China has a large number of associated iron minerals instead, especially the arsenic iron ores
Few elements can react with these trace elements, owing to their weak reactivity, except for rare earth elements (REs)
The aim of this work is first to check the evaporation effect of arsenic before the addition of lanthanum in the liquid steel, and to study the evolution of arsenic- and lanthanum-containing inclusions during the whole steelmaking process, and and to discuss the effect of reactions between lanthanum and alumina crucibles on the formation of arsenic inclusions, as well as the content of arsenic in steel

Summary

Introduction

The trace elements arsenic, tin, lead, antimony, and bismuth have been considered the five most harmful trace elements to steel products, especially for the high-temperature mechanical properties [1,2,3,4,5]. They come mainly from steel scrap and iron ores containing these elements, and cannot be removed from steel in the mainstream oxidation steelmaking process. Few elements can react with these trace elements, owing to their weak reactivity, except for rare earth elements (REs). REs have been used to modify the existing state of trace elements

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Conclusion