Calcium Silicon Casi Alloy

Calcium Silicon

CaSi alloy is compound alloy which is composed of silicon, calcium and ferro. It is an ideal compound deoxidizer and desulfurizer which can be used in the production of many kinds of steel such as rail steel, low carbon steel, stainless steel and other special alloy like Ni base alloy and titanium base alloy. CaSi alloy also can be applied as the heatraiser in convertor steelmaking workshop and as the inoculant or additive in producing cast iron and nodular cast iron. Our Calcium Silicon owns many advantages as follows.

1. Si and Ca can be controlled as needed.
2. Pulverization and deliquescence resistance.
3. less impurities such as C, S, P, Al.

Besides, we can offer other specifications such as Ca10-15%,Ca 20-30% Si40-50%, in one word, we can wholly meet your requirement.

Case Study

Background
A specialty steel mill in Pohang, South Korea, producing high-grade bearing and gear steels, faced persistent customer rejects due to elongated manganese sulfide (MnS) inclusions and sporadic nozzle clogging during continuous casting. Despite using conventional aluminum deoxidation, the steel lacked sufficient calcium treatment to modify non-metallic inclusions. The mill introduced Calcium Silicon (CaSi) Alloy to resolve these quality constraints.

Challenge
The mill's prior practice used only ferrosilicon and aluminum for deoxidation. This resulted in high-alumina (Al₂O₃) inclusions, which are hard and angular, causing:

Nozzle clogging in 14% of heats, leading to casting interruptions.

Poor machinability and fatigue life in the final bearing rings.

Inconsistent impact toughness, especially in large-section bars.

Calcium was absent from the inclusion engineering strategy, leaving sulfides in their undesirable elongated form rather than globular, harmless shape.

Solution
After a ladle metallurgy furnace (LMF) trial, the mill adopted Calcium Silicon (CaSi) Alloy with the following specification:

Ca 28–31%, Si 55–60%, Al ≤1.5%, C ≤0.5%

Particle size: 10–50mm (for ladle addition)

Addition method: Wire feeding (cored wire, 13mm diameter) to ensure deep calcium dissolution without excessive fuming

Implementation
The CaSi cored wire was injected during the final 8 minutes of ladle refining, at a feed rate of 2.5 m/s. Target calcium addition: 0.025–0.035% in liquid steel. After wire feeding, soft argon stirring was maintained for 12 minutes to promote inclusion flotation and modification.

Results (6-month production data)

Nozzle clogging reduced from 14% to 2.3% of heats, improving casting productivity by 11%.

Inclusion rating (ASTM E45) : Alumina-type (B) inclusions dropped from 2.5 to 0.8, while globular sulfides (Type C) became the dominant form.

Impact toughness (Charpy V-notch at -40°C) increased from 27 J to 42 J, exceeding customer specification.

Steel cleanliness index (by SEM/EDS) showed complete transformation of Al₂O₃ into liquid calcium aluminates (C12A7), which do not clog nozzles.

Economic impact
Annual savings from reduced casting interruptions: €340,000. Lower rejection rate (from 5.1% to 1.7%) added €510,000 in recovered product value. CaSi cored wire cost increased moderately, but net benefit after six months exceeded €620,000.

Conclusion
Calcium Silicon (CaSi) Alloy, when applied via cored wire with precise calcium control, is highly effective for inclusion modification in clean steel production. The South Korean mill now standardizes CaSi treatment for all bearing and gear steel grades. For steelmakers targeting high fatigue life and castability, CaSi remains an indispensable tool.

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