Introduction
In the process of steel casting and special alloy production, the purity of molten steel directly affects the mechanical properties, fatigue life and surface quality of the final product. Non-metallic inclusions (such as oxides, sulfides, slag, etc.) are one of the main sources of casting defects, which may cause cracks, pores or reduced mechanical properties. Therefore, molten steel filtration technology has become an indispensable key link in modern casting technology.
As a professional supplier of casting refractory materials, SF-Foundry is committed to providing efficient and reliable filtration solutions for the steel casting industry. This article will systematically introduce the core technology, material selection, application cases and future development trends of molten steel filtration to help customers optimize production processes and improve casting quality.
Necessity of molten steel filtration
Common inclusions in molten steel
Molten steel is easily mixed with the following inclusions during smelting, transportation and pouring:
Deoxidation products (such as Al₂O₃, SiO₂)
Slag and refractory erosion particles
Oxides formed by secondary oxidation
The size of these inclusions ranges from a few microns to hundreds of microns, and it is difficult to completely remove them by traditional static or slag methods.
Harm of inclusions to castings
Degradation of mechanical properties: inclusions become stress concentration points, reducing the strength and toughness of the material.
Processing difficulties: hard inclusions (such as Al₂O₃) accelerate tool wear.
Surface defects: microcracks or pores may appear after polishing or plating of castings.
Solution: Use foam ceramic filters to precisely filter molten steel, which can effectively intercept inclusions ≥20μm and significantly improve the purity of molten steel.
Comparison of molten steel filtration technology
The commonly used molten steel filtration methods in industry include:
| Filtration method | Principle | Advantages | Disadvantages |
|---|---|---|---|
| Ceramic foam filter | Porous ceramic interception inclusions | High efficiency, strong applicability | Preheating required, high cost |
| Straight hole honeycomb ceramic | Regular channel mechanical filtration | Large flow, high strength | Easy to clog, low precision |
| Fiber filter | fiberglass adsorption | Low cost, easy to install | Temperature difference resistance |
| Electromagnetic filtration | Magnetic field separation of non-metallic particles | No contact, continuous processing | Complex equipment, limited applicable steel types |
Conclusion: Zirconia foam ceramic filter has the best comprehensive performance, especially suitable for high-end applications such as high-temperature alloy steel and stainless steel.
Core performance of foam ceramic filter
Material selection
Zirconium oxide (ZrO₂)
Temperature resistance: above 1700℃ (suitable for ultra-high temperature steel)
Advantages: strong thermal shock resistance, chemical inertness
Application: stainless steel, nickel-based alloy
Key parameters
Pore density (PPI): 10-40 PPI (pores/inch), the higher the value, the higher the filtration accuracy, but the flow resistance increases.
Compressive strength: ≥3 MPa (to ensure the impact of molten steel).
Apparent porosity: 75-85% (balance filtration efficiency and flow rate).
Industrial application cases of molten steel filtration
Case 1: Inclusion control of stainless steel castings
Problem: A company produces 304 stainless steel valve bodies, and the Al₂O₃ inclusions in the castings exceed the standard, resulting in a machining pass rate of only 82%.
Solution: Use SF-Foundry 30 PPI zirconia foam ceramic filter.
Effect: Inclusions were reduced by 70%, and the qualified rate was increased to 95%.
Case 2: Optimization of high carbon steel continuous casting process
Problem: Frequent cracks on the surface of continuous casting billets, and detection found that CaO-SiO₂ inclusions were aggregated.
Solution: Install a 20 PPI silicon carbide filter at the pouring port of the tundish.
Effect: The crack rate decreased by 50%, and the quality of continuous casting billets was significantly improved.
Conclusion
Steel filtration is a key process to improve casting quality and reduce production costs. As a professional supplier of casting refractory materials, SF-Foundry provides a full range of foam ceramic filters (zirconia, silicon carbide, alumina) and supports customized solutions. If you need technical consultation or sample testing, please contact our engineering team.