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Calcium silicon alloy is an essential material in steelmaking, commonly added to enhance steel’s performance and quality through deoxidation and desulfurization. At high temperatures, impurities are removed, and oxides are reduced, improving the purity, stability, and overall quality of the steel. Calcium silicon alloy finds applications in steelmaking, casting, and smelting.
The alloy is available in various forms, such as calcium silicon lump (10–80 mm, 10–50 mm), calcium silicon granules (0–3 mm, 3–8 mm), calcium silicon powder (0–200 mesh), and calcium silicon cored wire (produced by wrapping calcium silicon powder with steel strips). The production process involves preparing the alloy using raw materials like quartz and lime and reducing agents in an electric furnace. Below is the detailed smelting process:
Steps in the Smelting Process
1. Raw Material Preparation
Quartz (SiO₂): Acts as the silicon source; high-purity quartz is essential to minimize impurities.
Lime (CaO): Provides the calcium source; high-calcium-content quicklime obtained from calcined limestone is required.
Reducing Agent: Typically carbon-based materials like coke, anthracite, or charcoal.
Auxiliary Materials: Includes electrode paste and covering agents (e.g., ferroalloys) to stabilize the arc and reduce heat loss.
2. Batching and Mixing
Accurately calculate the quantity of each raw material based on the target composition of the calcium silicon alloy.
Mix quartz, lime, and reducing agents uniformly to ensure consistency and prevent localized reactions.
3. Loading
Load the mixed raw materials into the electric furnace in layers, ensuring good permeability and uniform charge distribution.
Use electrodes to introduce current into the furnace for arc heating.
4. Heating and Reduction Reaction
At high temperatures (1,500–1,800°C) inside the electric furnace, the following key reactions occur:
SiO₂ + C → SiO↑ + CO↑
SiO + C → Si + CO↑
CaO + Si → CaSi
Silicon monoxide gas (SiO) is produced by the reaction of quartz and carbon and is further reduced to metallic silicon. Calcium from lime reacts with silicon to form the calcium silicon alloy.
5. Melting and Unloading
Once the reaction is complete, the liquid calcium silicon alloy settles at the furnace’s bottom, while slag floats on the surface, insulating heat and absorbing impurities.
The alloy and slag are separated through the furnace mouth. The alloy is poured into molds for cooling and solidification.
6. Product Processing
After cooling, the calcium silicon alloy is crushed, screened, and packaged according to user requirements.
Additional chemical analysis and adjustments may be performed to meet specific product specifications.
7. Tail Gas and Waste Treatment
The smelting process generates significant CO gas, which must be collected through a tail gas treatment system to minimize environmental impact.
The slag can be recycled or utilized as raw material for building materials.
Critical Control Points
Temperature Control: The smelting temperature significantly impacts the composition and quality of the calcium silicon alloy.
Raw Material Purity: Impurities can degrade the product’s quality, so raw materials must be strictly monitored.
Reaction Time: Proper timing is crucial to achieving the desired alloy composition.
Conclusion
The above process ensures the production of calcium silicon alloy with uniform composition and stable quality. This alloy is widely used as a steel deoxidizer and as an additive for alloying elements, playing a crucial role in enhancing steel’s properties in various industrial applications.
