Calcium silicide and calcium iron cored wire both exist to do the same job: deliver calcium deep into the ladle so it can modify inclusions rather than vaporise at the surface. The choice between them comes down almost entirely to what else arrives with the calcium.
The two wires
| CaSi (calcium silicide) | CaFe (calcium iron) | |
|---|---|---|
| Calcium | 28–32% | varies by product, commonly 10–30% |
| Other elements | 55–60% silicon | balance iron |
| Adds silicon? | Yes, significantly | No |
| Typical cost per unit of Ca | Generally lower | Generally higher |
CaSi is the more widely used of the two, and for most steel grades it is the default. It is the more economical source of calcium, and for the large majority of steels the silicon it brings is either wanted or harmless.
CaFe exists for the cases where that silicon is neither.
The silicon calculation
As with silico manganese versus ferro manganese, the deciding question is how much of the secondary element rides along.
Work it out for your own treatment. Take the mass of CaSi powder you feed, at roughly 57% silicon, apply your silicon recovery, and divide by the heat weight. For typical calcium treatment rates the silicon contribution is small — often a few hundredths of a percent — because the calcium addition itself is small.
For most grades that is immaterial, and this is why CaSi dominates. It becomes material in two situations:
- Very low silicon grades. Some interstitial-free, electrical and ultra-low silicon grades have ceilings tight enough that even a small, variable silicon input is unwelcome.
- Where silicon must be held precisely. If silicon is a controlled alloying element at a tight target, having it move with your calcium addition adds a variable you would rather not have. CaFe decouples the two.
What does not separate them
It is worth being clear about the things that are often claimed as differences and largely are not.
Recovery. Calcium recovery is low and variable with both — it is dominated by feed speed, ladle depth, sheath thickness, stirring practice and how quickly the ladle is covered after treatment. Neither wire has an inherent advantage large enough to decide the choice. If your recovery is poor, the fix is in your practice, not in switching wire type.
Inclusion chemistry. The calcium does the same work either way. What matters is hitting the right calcium-to-aluminium window — under-treat and you get partially modified, high-melting-point calcium aluminates that clog nozzles just as badly as untreated alumina; over-treat and you form solid calcium sulphide, which also clogs. That window is a function of your steel chemistry, not of which wire delivered the calcium.
Density effects. Sometimes raised as a point in CaFe's favour, since iron is denser than silicon. In practice sheath thickness and feed speed control the release depth far more than core density does.
How to decide
- Check your silicon ceiling and how tightly you need to hold silicon. If there is comfortable headroom and no precision requirement, CaSi is almost certainly the better commercial choice.
- Compare cost per unit of calcium delivered, not per tonne of wire or per metre. Fill weight varies between products, so per-metre pricing is not comparable across suppliers.
- Credit the silicon honestly. If it is silicon you wanted, it is a genuine credit. If it is silicon you now have to work around, it is a cost.
- Confirm the fill weight tolerance. Your dosing is metres fed multiplied by grams per metre. A wire with an inconsistent fill weight makes that calculation unreliable regardless of which type it is — this is the most common real-world quality problem with cored wire, and it applies equally to both.
Other wires in the same decision
Solid calcium wire is a third option where the highest calcium concentration per metre is wanted and neither silicon nor additional iron is welcome. It is generally the most expensive route per unit of calcium and demands careful feed control, but it has its place on tightly specified grades.
For anything beyond calcium — carbon trimming, sulphur addition for free-machining grades, titanium or boron — the wire type follows from the element, not from this comparison. Our guide to cored wire in ladle treatment covers the full range and the feeding practice that determines results.
In short
Use CaSi unless the silicon is a problem. It is the cheaper source of calcium and suits the large majority of steel grades. Use CaFe when your silicon ceiling is tight or when silicon must be held to a precise target independently of your calcium treatment.
Beyond that, the two behave similarly enough that the decision should be made on the silicon question and the delivered cost per unit of calcium — and your attention is better spent on feed speed, stirring and the calcium-to-aluminium ratio, which is where the real variation in results comes from.
We manufacture cored wire in both types and in the diameters and fill weights your feeder requires. Tell us your grade and ladle practice and we will recommend a specification.
Frequently asked questions
Which gives better calcium recovery?
Neither has an inherent advantage large enough to decide the question on its own. Recovery is dominated by feed speed, ladle depth, sheath thickness, stirring and how quickly the ladle is covered after treatment, rather than by the choice between CaSi and CaFe.
When should I choose CaFe over CaSi?
When the grade cannot accept the silicon that CaSi contributes, or when you want to keep silicon under independent control rather than have it move with your calcium addition. Low silicon and some ultra-low silicon grades are the usual cases.