The term 'silicon metal' is used to describe alloys containing silicon as the main alloying element, which are often used in foundries. The addition of silicon to these alloys results in improved flowability, hot cracking resistance and tightness. Other elements such as copper and magnesium are added to improve the strength of the material during heat treatment.
The role of silicon metal in steel production is multifaceted.
(a) One of its key functions is deoxidation. Silicon is a powerful deoxidising agent that can effectively combine with oxygen in molten steel to form SiO₂ slag, thereby reducing the oxygen content of the steel.
b) Increasing melting point: The addition of silicon metal can result in a slight increase in the melting point of steel, which is useful in some high temperature applications.
c) Promoting graphitisation: In cast iron, the presence of silicon metal can promote graphite formation, affecting the structure and properties of the iron.