# Effects of Basicity, MgO, and Al2O3 on Thermodynamic and Physicochemical Properties of CaO-SiO2-MgO-Al2O3 Slag System

## TL;DR

This study examines how varying slag composition affects steelmaking efficiency, focusing on a CaO-SiO2-MgO-Al2O3 system to optimize refining processes.

## Contribution

The study provides new insights into optimal slag composition parameters for improved steel refining efficiency.

## Key findings

- The CaO-SiO2-MgO-Al2O3 slag system performs best with basicity between 3 and 4.
- Optimal MgO content is between 6% and 8% for improved refining efficiency.
- Al2O3 content of 15%–25% enhances slag properties in steelmaking.

## Abstract

Ladle furnace (LF) refining is one of the most widely used secondary refining processes for producing clean steel and constitutes a key process in the steelmaking–continuous casting section. The properties of slag play a decisive role in determining molten steel quality and refining efficiency. In this study, based on the composition of refining slag from a steelmaking plant in China, the properties of a CaO-SiO2-MgO-Al2O3 slag system were investigated with respect to five aspects, the liquid phase region, sulphide capacity, melting properties, slag viscosity, and mineralogical phase precipitation, at varying temperatures, basicity, w(MgO) and w(Al2O3) using FactSage and the KTH model. Analysis of the slag properties indicates that the CaO-SiO2-MgO-Al2O3 slag system performs better when basicity ranges from 3 to 4, w(MgO) is between 6% and 8%, and w(Al2O3) is 15%–25%. These findings provide theoretical support and guidance for optimizing the refining slag system in plant trials.