Short answer: Usually, no. Ferrosilicon is commonly selected to add silicon and deoxidize steel. Calcium silicon also introduces calcium, which may be used in a controlled treatment of non-metallic inclusions. The same nominal silicon addition does not make the two products equivalent in a particular melt.
Start with the job the addition must do
If the objective is to meet a final silicon range, ask the metallurgist which silicon source and recovery assumption the process uses. If the objective includes calcium treatment or inclusion-shape control, define that separately. Osaka Special Alloy describes Ca-Si as a calcium-and-silicon deoxidizing agent and explains that calcium additions can affect inclusion shape. Elkem describes FeSi as an iron-silicon alloy used for deoxidation and alloying. Those descriptions explain why a purchasing substitution needs technical approval; they do not prescribe a universal addition rate.
What to confirm before requesting a quote
- Steel and process: State the steel grade, furnace or ladle step, and whether the material is for silicon adjustment, deoxidation, calcium treatment, or a combination.
- Required chemistry: Give the acceptable Si and Ca ranges for the purchased alloy, plus any limits on Al, C, P, S and other elements that matter to your specification. Do not infer these from a product name.
- Form and feeding method: Specify lump, granule or cored wire as appropriate to the plant equipment. A wire-feeding practice cannot be assumed from a lump-material offer.
- Acceptance: Ask how the trial will be assessed: the final steel chemistry, inclusion target, process observations and the mill’s own sampling method.
When a substitution proposal is sensible
Ask your process engineer to compare the two additions only after defining the intended result and allowed chemistry. A supplier can quote both forms and provide the actual lot specification, but the mill should decide the treatment sequence and trial acceptance limits. Requesting only “the same Si percentage” leaves the calcium addition and process effect undefined. For a comparable commercial request, see our quotation checklist.
Sources
- Osaka Special Alloy, Steel deoxidizers and calcium additives, product information, accessed 2 November 2026.
- Elkem, What is ferrosilicon?, product information, accessed 2 November 2026.
