Calcium silicon alloys are primarily composed of calcium (Ca) and silicon (Si), with some elements such as barium and aluminum, supporting their adaptability to various applications:
Composition range: Ca 28%-35%, Si 55%-65%, impurities Al≤2.0%, S≤0.04%, P≤0.04%
Physical properties: Melting point 1250-1350℃, density 2.5-2.8 g/cm³, in lump (5-30 mm) or granular (1-10 mm) form, exhibiting strong chemical activity at high temperatures.
Core functions: Integrating desulfurization, deoxidation, alloying, and grain refinement, it is a "multi-functional composite agent" in the metallurgical industry.
Core Application Scenarios of Silicon Calcium Alloy
(1) Steelmaking Industry: Core Raw Material for Desulfurization, Deoxidation, and Alloying
Siliconcalcium alloy is a high-efficiency composite functional material in the steelmaking industry, especially suitable for the production of high-end steel and ultra-low sulfur steel. Its core applications are as follows:
Deep Desulfurization:
Mechanism of Action: Calcium reacts with sulfur with extremely low free energy, spontaneously generating CaS (melting point 2450℃, almost insoluble in molten steel) at high temperatures. Silicon simultaneously deoxidizes and optimizes the reaction environment (English: Ca + S → CaS, Si + 2FeO → SiO₂ + 2Fe);
Quantitative Effect: Adding 0.1%-0.5% can reduce the sulfur content of molten steel from 0.05%-0.08% to below 0.01% (ultra-low sulfur steel standard), achieving a desulfurization rate of 80%-95%;
Suitable Scenarios: High-end steel grades sensitive to sulfur content, such as bearing steel, spring steel, and stainless steel.
High-efficiency deoxidation:
Mechanism of action: Calcium has a stronger deoxidizing ability than aluminum and silicon. It can react with oxygen and oxides in molten steel to form CaO, and can also reduce Al₂O₃ inclusions (forming low-melting-point CaO・Al₂O₃), which are easily removed by flotation.
Quantitative effect: With an addition of 0.2%-0.3%, the oxygen content in molten steel decreases from 80-100ppm to 20-30ppm, the total amount of oxide inclusions decreases by 60%-70%, and the surface defect rate of steel billets decreases from 1.2% to 0.3%.
Suitable scenarios: Production of low-alloy high-strength steel and electrical silicon steel, improving the processing performance and service life of steel.
Alloying and Performance Enhancement:
Mechanism of Action: Calcium and silicon atoms are incorporated into the ferrite lattice, causing lattice distortion, hindering dislocation movement, and refining grain size;
Quantitative Effect: Adding 0.1%-0.2% ferro silicon calcium alloy to low-alloy structural steel increases tensile strength by 10%-15% and impact toughness (-20℃) by 20%-30%, making it suitable for engineering machinery and bridge steel;
(2) Foundry Industry: Inoculant and Spheroidizing Agent Core Components
SiCa alloy is mainly used in the production of gray cast iron and ductile iron to improve the uniformity of casting structure and mechanical properties:
Inoculant Application:
Mechanism of Action: Promotes graphitization precipitation, refines graphite grains and matrix structure, and avoids white cast iron tendency;
Quantitative Effect: Adding 0.1%-0.3% granular ferro calcium silicon alloy (1-3mm) (gray cast iron) increases the tensile strength of castings from 200MPa to 280MPa and improves impact toughness. 133%, scrap rate reduced from 8% to 3%; Suitable for: Precision castings such as engine blocks and machine tool beds.
Spheroidizing agent components:
Mechanism of action: Used in combination with magnesium and rare earth elements (such as silicon calcium barium alloys) to promote graphite crystallization into spherical shapes, improving the toughness and strength of ductile iron;
Effect: Spheroidization rate can reach over 90%, ductile iron tensile strength ≥450MPa, elongation ≥10%, suitable for load-bearing parts such as automotive crankshafts and gears;
Advantages: Compared to single magnesium spheroidizing agents, calciumsilicon alloys can reduce magnesium burn-off rate by 15%-20%, reducing production costs.
(3) Ferroalloy Production: High-Efficiency Reducing and Refining Agent
CaSi alloys, due to their strong reducing properties and low carbon content (≤0.1%), are ideal reducing agents for the production of low-carbon ferroalloys.
Core Applications:
Mechanism of Action: Reduces oxides of vanadium, titanium, niobium, etc., to prepare low-carbon ferrovanadium, ferrotitanium, ferroniobium, etc., avoiding carbon enrichment;
Suitable Scenarios: High-end ferroalloy production, used in aerospace and electronic materials fields.
Refining Function: Removes impurities such as sulfur and phosphorus from ferroalloys, improving product purity. For example, when producing high-purity ferromanganese, adding calcium silicon alloys reduces the sulfur content from 0.05% to below 0.01%, meeting the requirements of high-end steel smelting.
(4) Other Application Scenarios
Non-ferrous Metal Smelting: As a refining agent for aluminum and copper alloys, it removes oxygen and sulfur impurities, improving metal purity and fluidity; with an addition of 0.3%-0.5%, the oxygen content of aluminum alloys decreases from 50-80ppm to 20-30ppm, reducing the porosity defect rate of castings by 70%; Suitable scenarios: Aerospace aluminum alloy and precision copper alloy production.
Welding Materials: As a raw material for welding rods and flux coatings, with an addition of 20%-30%, it deoxidizes and desulfurizes during welding, improving weld strength and corrosion resistance; weld tensile strength ≥400MPa, and salt spray corrosion resistance time extended by 2 times; Suitable scenarios: Construction and machinery welding.
Application Adaptation and Selection Logic of Different Grades of CaSi Alloys
(1) Core Grades and Application Adaptation Table
| Silicon Calcium Alloy Grade | Core Components (Ca/Si) | Core Application Scenarios | Recommended Addition |
| CaSi3060 | 30%/60% | Deoxidation in conventional steelmaking, inoculation of low-alloy castings | 0.1%-0.2% (steelmaking), 0.1%-0.3% (casting) |
| CaSi3262 | 32%/62% | Desulfurization in high-end steelmaking, spheroidization in precision casting | 0.2%-0.5%(steelmaking),0.2%-0.4%(casting) |
| CaSi3560 | 35%/60% | Refining of ultra-low sulfur steel, reducing agents in ferroalloy production | 0.3%-0.5%(steelmaking),1.2-1.5 ton / ton alloy(ferro alloy) |
(2) Core Selection Principles
Performance Priority: High-grade steel and precision casting should use high-calcium grades (Ca≥32%) to ensure desulfurization and deoxidation effects;
Cost Balance: Ordinary steel and conventional casting should use medium-calcium grades (Ca 30%-32%) to balance performance and cost;
Process Adaptation: Steelmaking should use blocky (5-30mm) materials, casting should use granular (1-3mm) materials, and ferroalloy production should use blocky (10-50mm) materials.
