Investigations of inclusions in ferrochromium alloys

Abstract

Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si–Cr–O and Cr–O oxides as well as intermetallic Cr–Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr–Mn–S, Cr–C–N, Si–Al–Ca–Mg–O and Ca–O–P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.

Keywords:

• LCFeCr
• HCFeCr
• Inclusions
• Electrolytic extraction
• Three-dimensional investigations

Acknowledgement

The China Scholarship Council (CSC) is acknowledged for the financial support to this study.