OMH is the only ASX listed company producing ferro-silicon as...

OMH is the only ASX listed company producing ferro-silicon as far as I know. S32 does produce some manganese ferro alloys.
Otherwise, companies in China, India, Iceland, Russia, Brazil, Egypt.

A wide range of ferrosilicon alloys are available for alloying and deoxidation purposes in steelmaking processes. Ferrosilicon is an important additive in the manufacture of steel products.
Ferrosilicon is used to remove oxygen from the steel and as alloying element to improve the final quality of the steel. Silicon increases namely strength and wear resistance, elasticity (spring steels), scale resistance (heat resistant steels), and lowers electrical conductivity and magnetostriction (electrical steels). Special FeSi like low Al, High Purity and low C ferrosilicon are used in the production of special steel qualities for transformers/motors, ball bearings and shock absorbers, tyre cord steel and in stainless steel.