Calcium Silicon (CaSi) alloy is a versatile metallurgical additive widely used in modern foundry workshops. It serves as a powerful deoxidizer, desulfurizer, graphite inoculant, and inclusion modifier for both gray iron and ductile iron casting. However, different casting processes (sand casting, investment casting, die casting, and continuous casting) require different CaSi grades, sizes, and calcium-silicon ratios.Many foundry defects such as shrinkage cavities, porosity, cold shut, and poor graphite spheroidization are caused by mismatched CaSi alloy specifications.
Common Commercial CaSi Alloy Grades & Specifications
Foundry-grade calcium silicon alloys are mainly divided into three mainstream grades based on Ca and Si content. Each grade has unique metallurgical characteristics that fit specific casting production demands.
|
CaSi Grade |
Ca Content |
Si Content |
Impurity (S/P) |
Core Characteristic |
|---|---|---|---|---|
|
Ca28Si60 |
28% Min |
60% Min |
Low |
Balanced inoculation & desulfurization, universal grade |
|
Ca30Si60 |
30% Min |
60% Min |
Ultra-low |
High calcium activity, strong inclusion modification |
|
Ca20Si65 |
20% Min |
65% Min |
Standard |
High silicon, excellent fluidity improvement |
Key Selection Factors for Casting Production
Before matching CaSi alloys to your casting process, confirm these four critical factors to avoid quality instability and cost waste:
Calcium & Silicon Ratio
High-calcium grades focus on desulfurization and inclusion modification, ideal for high-purity ductile iron. High-silicon grades prioritize improving molten iron fluidity and graphite refinement, perfect for gray iron casting.
Size Matching
Size directly affects melting speed and element recovery rate. Overly fine powder causes oxidation loss; oversized lags lead to incomplete melting and uneven inoculation.
Impurity Control
Low sulfur and phosphorus CaSi alloys prevent brittle inclusions and pinhole defects, which is essential for precision and high-strength castings.
Adding Method
Different feeding methods (ladle inoculation, stream inoculation, late inoculation) require different sizes and alloy activity levels.
CaSi Alloy Selection by Different Casting Processes
This is the most practical guide for global foundries. Each mainstream casting process has targeted CaSi grade and size solutions.
Sand Casting (Gray Iron & Ordinary Ductile Iron)
Recommended Grade: Ca28Si60 | Size: 10–30mm
Sand casting is the most common mass-production casting process with moderate defect tolerance. Ca28Si60 provides balanced deoxidation and graphite refinement effects. It effectively reduces shrinkage porosity, optimizes graphite distribution, and improves casting surface finish. This grade delivers the best cost-performance for standard mechanical parts, pipe fittings, and automotive gray iron components.
Precision Investment Casting
Recommended Grade: Ca30Si60 High-Purity | Size: 3–10mm
Investment castings require ultra-low defect rates and high dimensional accuracy. High-calcium Ca30Si60 with ultra-low impurities deeply modifies molten iron inclusions, eliminates micro-pores and cold shut defects, and improves the compactness of precision castings. Fine particle size ensures rapid and uniform melting without residue contamination.
High-Pressure Die Casting
Recommended Grade: Ca20Si65 | Size: 3–15mm
Die casting demands excellent molten iron fluidity for thin-wall and complex-shaped parts. High-silicon Ca20Si65 significantly improves melt fluidity and mold-filling ability. It stabilizes solidification structure and reduces die-casting-specific defects such as insufficient filling and surface burrs.
Continuous Casting for Iron Billets
Recommended Grade: Ca30Si60 | Size: 5–20mm
Continuous casting requires stable molten iron composition and anti-clogging performance. High-calcium CaSi alloy spheroidizes hard alumina inclusions, ensures smooth continuous casting, and avoids nozzle blockage. It maintains consistent billet structure and reduces continuous casting downtime.
Process & Grade Quick Matching Table
|
Casting Process |
Best CaSi Grade |
Ideal Particle Size |
Main Improvement Effects |
|---|---|---|---|
|
Sand Casting |
Ca28Si60 |
10–30mm |
Cost-effective inoculation, fewer shrinkage defects |
|
Investment Precision Casting |
Ca30Si60 |
3–10mm |
Ultra-low impurities, high casting compactness |
|
High-Pressure Die Casting |
Ca20Si65 |
3–15mm |
Improve fluidity, perfect thin-wall forming |
|
Continuous Casting |
Ca30Si60 |
5–20mm |
Stable composition, prevent nozzle clogging |
Common Defects Caused by Wrong CaSi Selection
Poor graphite spheroidization: Using low-calcium grade for high-end ductile iron
Casting porosity & pinholes: High-impurity CaSi alloy with excessive S/P content
Low fluidity & incomplete filling: Low-silicon CaSi grade for die casting thin parts
Uneven alloy distribution: Mismatched size causing incomplete melting
Selecting the correct silicon calcium alloy depends entirely on your casting process type, casting precision requirements, and quality standards. Ca28Si60 is the universal cost-effective option for ordinary sand casting. High-purity Ca30Si60 suits precision investment casting and continuous casting that require high purity and stable inclusion modification. High-silicon Ca20Si65 is the best choice for die casting processes needing superior molten iron fluidity.
By matching targeted SiCa grades and sizes to specific casting processes, foundries can effectively reduce defective rates, improve surface quality and mechanical performance of finished castings, and optimize overall production costs.
