Ferro silicon grains are commonly used as an alloying agent in the steel and casting industry to improve the properties of the final product. The application of ferro silicon grains includes:

Deoxidizer: Ferro silicon is added to molten steel to remove dissolved oxygen and other impurities. This helps improve the mechanical properties of the steel, such as its strength and ductility.

Inoculant: Ferro silicon can be used as an inoculant to promote the formation of graphite nodules in gray iron casting, which improves the ductility and strength of the cast iron.

Alloying agent: Ferro silicon is often used as an alloying agent in the production of various steels and castings to improve their mechanical properties, such as their strength, hardness, and resistance to corrosion.

The proper grain size of ferro silicon grains depends on the specific application and the process used. Generally, finer grain sizes are used for applications where the alloy needs to be more reactive, while coarser grain sizes are used for applications where longer reaction times are required. Common grain sizes for ferro silicon range from 0-3mm to 10-50mm. The appropriate grain size should be determined based on the specific requirements of the application and the process being used.