CaSi lump

Calcium-Silicon Alloys are used as deoxidizer and desulfurizer in the manufacturing of high grade steel. Indeed, Calcium and Silicon both have a strong chemical affinity for oxygen. Especially calcium, have a strong chemical affinity not only for oxygen, but also for sulphur and nitrogen. The steel industry accounts for around 90 % of global CaSi consumption.


The alloy is also used for the modification of non-metallic inclusions. Calcium Silicon is used to control the shape, size and distribution of oxide and sulfide inclusions improving fluidity, machinability, ductility, and impact properties of the steel product. The calcium liquefies the suspended solid inclusions of aluminium oxide), a principal source of fatigue failure in highly stressed alloy steels, that are always present in aluminium-killed steels(Al203 is transformed by Ca into CaO:Al2O3). Furthermore, the material properties of steel are improved: the calcium aluminates formed are largely undeformable  in the solidified steel and allow high isotropy of the material properties to be maintained after working of the steel.


As a sulphide former, CaSi alloy promotes random distribution of sulfides, thereby minimizing chain-type inclusions.


Silicon-calcium alloy can replaces aluminium to accomplish the task of final deoxydation, and is used in the production of fine steel, special steel and special alloy. CaSi is indeed required in higher quality, higher strengh steels and alloy steels, which cannot tolerate the level of inclusions that remain following standard deoxidisation with ferrosilicon, silicomanganese or aluminium. For example, to turn out rail steel, mild steel, stainless steel, and special alloys such as nickel-based alloy and titanium-based alloy, which can be adopted Silicon-calcium alloy as deoxidant. Silicon-calcium alloy can also work as temperature-gaining agent in convertor steel making workshop , and as catalyst/inoculant in production of cast iron, as well as the additive in the production of nodular cast iron.

Calcium Silicon is also utilized in combination with Barium. The Barium increases the density of the alloy, thereby improving efficiency. In cast irons it is used mainly by Pipe Shops for the purpose of coating the inside of each mono cast machine.

Calcium Silicon can be obtained in lump, crushed or powder form. The most widely used method for intergrated steel applications is in the form of cored wire. This is mainly because calcium has a low density and high reactivity in the ladle making it difficult to introduce and retain in the melt. Cored wire eliminates these variables: CaSi powder is blown deep into the steel melt through immersion of steel tubes.


Fines of CaSi alloys can be used in the manufacturing of specialty pyrotechnic mixtures (component of firework or primer mix of munitions) and also as welding powder.

Prior to the 1980s, CaSi was dropped in lump form into the steel ladle. Most of the CaSi burned off into the slag on the top of the molten steel, with the CaSi only achieving a recovery of 2-5% into the molten steel.

In 1980, the European steelmaker Vallourec developed the process of adding CaSi into molten steel via the cored wire injection process

This involves enclosing CaSi powder within a hollow cored wire, and injecting it into the ladle of molten steel.  The wire penetrates the steel slag to a much more successful extent than dropping in CaSi lumps.  Recovery rates of 15-25% can be achieved by adding CaSi to steel by injecting cored wire

Certain steelmakers, notably TKS and Nippon Steel, developed an alternative method of adding CaSi into molten steel via gas injection.  This achieves a recovery rate of around 10%, but has a high capital cost

Through the 1980s and 1990s, cored wire injection of CaSi became adopted by more and more steel producers.  By the 2000s, this method has become the norm, accounting for 80% of the consumption of CaSi in steel





CaSi has been registered on its own for REACH in 2010

the position paper of the CaSi Institute can be found under Position Papers section