Calcium is a reactive metal that readily combines with a wide variety of other elements, including oxygen and sulphur. This property lends its use as a deoxidant and desulphuriser in steelmaking. Due to its reactivity with oxygen, it is rarely used in large scale in its pure form as the reaction can be hard to control, therefore it is largely used as an alloy with silicon as the primary carrier metal. This slows down the reaction and makes it less violent.
While this alloy can be used in the lumpy form, a better yield is normally observed when a granular form of the alloy is encapsulated in a steel sheath to form a cored wire. This is then fed into the ladle furnace at a controlled rate to achieve the desired amount of calcium in the melt. The steel sheath helps protect the alloy content until it is below the surface of the melt before the reactions start therefore ensuring a better recovery of the reactive materials as well as a more predictable recovery rate. The calcium concentration aimed for in the melt depends on several factors which include the oxygen and sulphur contents at the beginning and final stages of the melt. The oxide and sulphide products formed in these reactions have low densities and are removed via the slag.
In the case of aluminium killed steels that is continuously cast, calcium has the added benefit of converting aluminium oxide (solid) to calcium aluminate (liquid), which helps limit nozzle clogging.
The typical diameter of calcium silicide cored wire is 13mm. 9mm and 16mm wire are also available, however not popular when compared to the 13 mm wire. The wire sheath thickness is 0.35 to 0.40mm, this ensures the wire is robust enough to survive normal handling and feeding without making it so stiff that problems arise during coiling and uncoiling.
The alloy content of the wire is 30% Ca with the balance being largely Si and trace Fe.
Mineral-Loy supplies CaSi cored wire manufactured by a leading manufacturer of both the wire as well as all raw materials used in the manufacture of the wire. This ensures that quality and consistency is maintained to high standards. It available in both Eye to the Wall (EYW) and Eye to the Sky (EYS) orientation.