1. The Grade Structure Below 90%
Silicon carbide is available in grades below 90% SiC, typically 65%, 70%, 75%, 80% and 85%. The lower grades contain more free silicon, silica and other impurities, and they cost less per ton. For applications where the impurity load is acceptable, these grades deliver the metallurgical function at lower cost, which is why they are widely used in cost-sensitive steelmaking and foundry processes.
2. Composition Differences
As the SiC content falls, the balance is made up of free silicon, silica, iron oxide and other minerals. The fixed carbon and available silicon still provide the deoxidation and recarburization function, but more slag is generated per unit of active material, and the recovery per ton is lower. The composition should be stated on the certificate so that the buyer can calculate the usable value.
3. Uses in Steelmaking
In steelmaking, grades from 65% to 85% are used as deoxidizers and recarburizers where the steel chemistry tolerates the higher impurity load. They are also used for slag conditioning, where the silicon and carbon help control the slag and support the refining reactions. The choice of grade balances the process requirement against the cost per ton.
4. Foundry and Other Uses
In foundries, lower-grade silicon carbide is used for recarburization and silicon adjustment in gray and ductile iron, and for slag control. Outside metallurgy, lower grades serve as aggregates in certain refractory and abrasive applications where the purity requirement is relaxed. Each use should be evaluated by the effect of the impurities on the final product.
5. Cost Advantages and Trade-Offs
The main advantage is the lower price per ton. The trade-off is the lower active content, the higher slag volume and the larger charge weight needed for the same carbon and silicon pickup. The comparison should be made on the delivered cost per unit of active SiC and on the total process cost, including the slag handling and the quality effect.
6. Buying Considerations
Specify the SiC content, fixed carbon and impurity limits.
Select the particle size by the addition method.
Compare offers on the delivered cost per unit of active SiC.
Request the certificate of analysis and verify the batch.
Run a trial to confirm the recovery and slag behavior in your process.
7. FAQ
Q1: What grades of silicon carbide below 90% exist? Common grades are 65%, 70%, 75%, 80% and 85% SiC.
Q2: Why buy a lower grade? The lower price per ton suits cost-sensitive applications where the impurity load is acceptable.
Q3: What are the trade-offs? More slag, lower recovery per ton and a larger charge weight for the same pickup.
Q4: Where are lower grades used? Steelmaking deoxidation and recarburization, foundry additions and slag conditioning.
Q5: How should offers be compared? On the delivered cost per unit of active SiC and the total process cost.
Q6: How is quality verified? By the certificate of analysis reporting SiC, fixed carbon and impurities per batch.
