Metallic silicon 553 represents that the industrial silicon contains iron less than or equal to 0.5%, aluminum content is less than or equal to 0.5%, and calcium content is less than or equal to 0.3%;

Metallic silicon 441 Industrial silicon means iron content is less than or equal to 0.3%, aluminum content is less than or equal to 0.3%, calcium content is less than or equal to 0.1%, and so on, due to customary reasons.

Metallic silicon 2202 is also abbreviated as 220, which means that calcium is less than or equal to 0.02%. The industrial silicon at the beginning of 2 is generally called chemical silicon.