Ferrosilicon is one of the most widely used inoculants and deoxidizers in the foundry industry. It offers multiple benefits, including improving molten iron fluidity, enhancing mechanical properties, and optimizing graphite morphology. Proper use of ferrosilicon can significantly improve casting quality. Therefore, before using ferrosilicon, you need to be aware of the following precautions.
1. Select the appropriate ferrosilicon grade based on the casting material
Common ferrosilicon grades include FeSi75, FeSi72, and FeSi65. Different silicon contents are suitable for different applications.
Steelmaking
High-silicon FeSi75 is used for steel deoxidation. It provides excellent deoxidizing performance, and the generated SiO₂ floats up quickly, effectively purifying the molten steel.
Gray iron production
For this application, the more economical FeSi65 or FeSi72 is typically used to increase silicon content in the molten iron, enhance graphitization tendency, and reduce the risk of chilled (white) structure.
Ductile iron production
Ferrosilicon is usually used together with inoculants. Ferrosilicon with stable silicon content and low impurity levels is preferred to avoid negatively affecting the spheroidization process.
2. Control the timing and method of ferrosilicon addition
Proper timing
Steel deoxidation: Add in multiple portions before and after tapping.
Cast iron inoculation: Since inoculation fades over time, ferrosilicon should be added as close to pouring as possible.
Appropriate addition methods
Granular ferrosilicon: Suitable for ladle or furnace addition, dissolves quickly.
Lump ferrosilicon: Suitable for furnace charging, offering stable and economical melting.
Powdered ferrosilicon: Suitable for injection deoxidation or runner inoculation, but requires precautions against dust loss and oxidation.
3. Pay attention to the melting point and dissolution rate of ferrosilicon
The melting point of ferrosilicon increases with silicon content; thus FeSi75 has a higher melting point than FeSi65. If added when molten metal temperature is too low, the following may occur:
Slow dissolution
Unmelted particles floating on the surface
Reduced inoculation effectiveness or inaccurate composition control
Therefore, in low-pouring-temperature situations, finer ferrosilicon particles with faster dissolution rates should be selected.
4. Strictly control impurity levels in ferrosilicon
Major impurities in ferrosilicon include Al, C, P, and S. Excessive impurities may cause casting defects or performance issues.
Aluminum (Al):
High Al content forms large amounts of alumina inclusions, significantly affecting steel cleanliness.
Sulfur (S) and Phosphorus (P):
These elements reduce mechanical properties. High sulfur is especially unacceptable in ductile iron, as it lowers spheroidization efficiency.
Carbon (C):
High-carbon ferrosilicon influences total carbon control in the melt, which is particularly critical for thin-walled or high-strength castings.
When purchasing ferrosilicon, you should review the chemical analysis report to ensure key elements are stable and within acceptable limits.
5. Pay attention to storage and moisture protection
- Ferrosilicon easily oxidizes, absorbs moisture, or even disintegrates when stored in humid environments, reducing its effective component content.
- Store in a dry, well-ventilated warehouse
- Avoid contact with acidic materials
- Use promptly after opening the packaging
- Powdered ferrosilicon must be sealed to prevent caking and dust loss
- Proper storage conditions maintain the activity and stability of ferrosilicon.
T.F Industrial Co., Ltd. is a specialized enterprise dedicated to the manufacturing of ferroalloys and metal products, equipped with numerous comprehensive production lines. Our primary products include metallurgical silicon, ferro-silicon, calcium-silicon alloy, ferro-manganese, silico-manganese alloy, and cored welding wire. Should you require any of these products, please email us at: louisxu@ns-ferroalloy.com. We will respond to you promptly.
