Main Silicon Carbide Grades
Silicon carbide is generally classified according to its SiC content and purity level. The most common grades used in metallurgy are:
| Grade | SiC Content |
|---|---|
| 88% Silicon Carbide | 88% min |
| 90% Silicon Carbide | 90% min |
| 95% Silicon Carbide | 95% min |
| 98% Silicon Carbide | 98% min |
Lower-grade silicon carbide is commonly used in metallurgical processes, while higher-purity grades are used in abrasives or advanced ceramics.
Typical Chemical Composition of Metallurgical Silicon Carbide
| Component | Typical Range |
|---|---|
| SiC | 88-98% |
| Si | 0.5-2.0% |
| Fe2O3 | 1.5% max |
| Fixed carbon | Grade dependent (low single-digit percentages for high-grade material) |
| Moisture | 0.5% max |
Fixed carbon content should be confirmed against the specific grade on the certificate of analysis, because it decreases as SiC content increases.
Silicon Carbide Particle Sizes
| Size | Application |
|---|---|
| 0-10 mm | Steelmaking |
| 1-5 mm | Foundry |
| 5-10 mm | Metallurgical additive |
| Powder | Refractory / abrasives |
Black vs Green Silicon Carbide
Black silicon carbide is produced from silica sand and petroleum coke and is widely used in metallurgy, refractory materials, and abrasive products; it is the most common type in the steel and foundry industries. Green silicon carbide is produced using higher-purity raw materials and is typically used in precision grinding, semiconductor materials, and high-performance ceramics; it usually contains higher SiC purity than black silicon carbide.
Factors Affecting Silicon Carbide Quality
Raw material purity affects the final SiC purity. Furnace temperature, with silicon carbide produced above 2000 deg C, directly affects crystal formation. Processing and grading, including crushing and screening into different particle sizes, ensure the final product meets industrial specifications.
Frequently Asked Questions
What is the most common silicon carbide grade? The most commonly used grades in metallurgy are 88 percent and 90 percent silicon carbide.
What particle size is used in steelmaking? Steel plants commonly use 0-10 mm silicon carbide for metallurgical applications.
How is silicon carbide quality verified? Suppliers usually provide a certificate of analysis (COA) to confirm chemical composition and specifications.
Q: How is silicon carbide classified by SiC content?
Metallurgical silicon carbide is graded by SiC content, typically 65, 70, 75, 80, 85, 88, 90, and 95 percent and above, with each grade having its own impurity limits.
Q: What are the two main crystal forms of silicon carbide?
The two main forms are black silicon carbide and green silicon carbide; green SiC is higher purity and mainly used for abrasives and precision grinding.
Q: Which SiC grades are selected for metallurgical use?
Metallurgical use typically selects 88 to 95 percent SiC grades for steelmaking deoxidation and foundry addition, balancing purity with cost.
Q: What impurities are specified for metallurgical SiC?
Key impurity limits cover free carbon, free silicon, iron, aluminum, calcium, and moisture; high free carbon changes the carburizing effect.
Q: What particle size ranges are standard for SiC supply?
Standard supply includes 0 to 1 mm, 0 to 5 mm, 1 to 10 mm, and 10 to 50 mm lumps, plus powder grades such as 100 mesh, 200 mesh, and 325 mesh.
