In steel refining, casting inoculation, and molten iron treatment processes, calcium silicon alloy (CaSi) serves as a highly efficient composite deoxidizer, desulfurizer, and inoculant. Its selection directly determines metallurgical costs, production efficiency, and final product quality. Faced with a global market of casi alloy products of varying specifications, making precise selections based on purity, size, and specific application scenarios is a key challenge for every purchasing decision-maker and metallurgical engineer.
Purity – The Core Factor Determining Metallurgical Reaction Efficiency
1.1 Scientific Classification and Standards of Purity Grades
The purity of calcium silicon alloys mainly refers to the content of its effective elements (Ca+Si) and the level of impurity element control. International mainstream standards typically classify it into three grades:
| Grade |
Typical Components (%) |
Critical Impurity Control | Applicable Standards |
| High purity grade |
Ca: 28-32%, Si: 58-62%, (Ca+Si)≥90% |
P≤0.025%, S≤0.025%, Al≤1.0%, C≤0.1% |
ASTM A495, GB/T 3419 |
| Industrial grade |
Ca: 24-28%, Si: 55-60%, (Ca+Si)≥85% |
P≤0.04%, S≤0.04%, Al≤1.5%, C≤0.2% |
Common Business Standards |
| Economic grade |
Ca: 20-24%, Si: 50-58%, (Ca+Si)≥80% |
P≤0.06%, S≤0.06%, Al≤2.0%, C≤0.3% |
Specific Protocol Standards |
1.2 How Purity Affects Metallurgical Performance: Data Analysis
Deoxidation Efficiency:
For every 1% increase in calcium content, the average deoxidation time of molten steel is shortened by 8-12%, and the final oxygen content can be reduced by 15-25 ppm.
Desulfurization Capacity:
High-purity alloys (Ca≥30%) can achieve a desulfurization rate of 85-95%, while industrial-grade products typically achieve 70-85%.
Inclusion Morphology Control:
High-purity low-alumina alloys (Al≤1.0%) can more effectively convert Al₂O₃ inclusions into low-melting-point calcium aluminates, improving the fatigue life of steel by 20-30%.
1.3 The Golden Rule of Purity Selection
High-end Special Steel Smelting (Bearing Steel, Pipeline Steel, Gear Steel):
High-purity products must be selected to ensure the plasticity and control of inclusions.
Ordinary Steel Refining and Secondary Metallurgy:
Industrial-grade products achieve the best balance between cost and effectiveness.
Cast iron inoculation treatment:
Industrial grade or economic grade can be selected according to the grade of the casting, but the phosphorus and sulfur content must be strictly controlled.
Size – Key to Controlling Reaction Kinetics and Yield
2.1 Industrial Standard Classification of Size Specifications
Size not only affects the convenience of transportation and addition, but also directly determines its dissolution rate, floating trajectory, and reaction yield in molten metal.
| Size range (mm) | Common name |
Apparent density (g/cm³) |
Typical melting time (molten steel, 1600°C) |
|
0-1 / 0.1-1.0 |
Powder/Fine Granules |
1.8-2.2 |
10-25 seconds |
|
1-5 / 2-8 |
Medium Granules |
2.0-2.4 |
25-45 seconds |
|
5-15 / 10-30 |
Standard Blocks |
2.2-2.6 |
45-90 seconds |
|
15-50 |
Large Blocks |
2.3-2.7 |
90-180 seconds |
2.2 Precise Matching of Size Selection with Metallurgical Processes
Scenario 1: Ladle Refining (LF Furnace, CAS-OB Process)
Recommended Size: 1-5mm or 2-8mm
Principle Analysis: Medium-sized blocky alloys achieve a suitable sinking depth, avoiding rapid floating and calcium volatilization (boiling point 1484°C), with a calcium recovery rate of 15-25%. Powders are easily carried away by flue dust, with a recovery rate often below 10%.
Scenario 2: Addition during Converter/Electric Furnace Tapping
Recommended Size: 5-15mm or 10-30mm
Principle Analysis: Larger particles can withstand the impact of the steel flow, penetrate the slag layer, and directly enter the interior of the molten steel for reaction, achieving simultaneous deoxidation and desulfurization.
Scenario 3: Cast Iron In-Flow Inoculation
Recommended Size: 0.2-0.7mm or 0.5-1.5mm
Principle Analysis: Fine particles ensure rapid dissolution and diffusion within a short time during molten iron pouring, achieving uniform nucleation of graphite and avoiding inoculation fading.
2.3 Importance of Size Uniformity
A narrow size distribution range (e.g., 2-8 mm instead of 1-10 mm) results in:
More consistent dissolution kinetics, avoiding drastic reaction fluctuations.
More accurate control of the wire feeder/addition equipment, achieving process stability.
Reduced dust generation, improving the workshop environment, and minimizing material loss.
Usage Scenarios – Decision Tree for Selection Based on Needs
Decision Tree: Selection Path for Three Core Application Scenarios
Start
│
├─ Scenario A: Deep Deoxidation and Inclusion Modification of Molten Steel
│ ├─ Target: [O] < 15ppm, Plastic Inclusions
│ │ → Selection: High-purity grade (Ca≥30%), Size 1-5mm
│ └─ Target: Economical Deoxidation
│ → Selection: Industrial grade (Ca 25-28%), size 2-8mm
│
├─ Scenario B: High-efficiency Desulfurization ([S] ≤ 0.005%)
│ ├─ Process: LF Furnace Refining
│ │ → Selection: High-purity/Industrial grade, Size 1-5mm (Wire Feed)
│ └─ Process: Molten Iron Pretreatment
│ → Selection: Industrial grade, Size 5-15mm (Injection or Input Method)
│
└─ Scenario C: Cast Iron Inoculation and Modification Treatment
├─ Ductile Iron
│ → Selection: Low-alumina industrial grade (Al≤1.2%), grit size 0.5-1.5mm
└─ Gray Cast Iron/Vermicular Graphite Cast Iron
→ Selection: Economic/Industrial grade, grit size 0.2-1.0mm
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