Mullite Sand
Product Information
Mullite sand is an aluminum silicate refractory material, generally used in stainless steel precision casting process. The refractoriness is about 1750 degrees. The higher the aluminum content in mullite sand, the lower the iron content, and the smaller the dust, the better the quality of the mullite sand product. Mullite sand is made by high-temperature sintering of kaolin.
Features:
1. High melting point, generally between 1750 and 1860°C.
2. Good high-temperature stability.
3. Low thermal expansion coefficient.
4. High chemical stability.
5. Reasonable particle size distribution allows for selection and adjustment based on different casting processes and casting requirements.
Product Index
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Specification
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Supper Grade
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Grade 1
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Grade 2
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Al2O3
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44%-45%
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43%-45%
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43%-50%
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SiO2
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50%-53%
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50%-54%
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47%-53%
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Fe2O3
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≤1.0%
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≤1.5%
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≤2.1%
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K2O+Na2O
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≤0.5%
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≤0.6%
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≤0.8%
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CaO
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≤0.4%
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≤0.5%
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≤0.5%
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TiO2
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≤0.3%
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≤0.7%
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≤0.3%
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Xaustic Soda
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≤0.5%
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≤0.5%
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≤0.7%
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Bulk Density
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≥2.5g/cm3
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≥2.5g/cm3
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≥2.45g/cm3
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Applications
The core of precision casting is mold shell manufacturing (the process of coating the wax pattern with multiple layers of refractory material to create an outer shell. After the wax pattern melts, a cavity is formed for pouring molten metal). Mullite sand is primarily used as a refractory aggregate in the mold shell and is applied to different layers of the shell, specifically as follows:
1. Surface Shell (Directly Determines the Surface Quality of the Casting)
Function: The surface layer is in direct contact with the casting and must ensure a smooth surface finish (avoiding roughness and pitting) while also withstanding the initial impact of the molten metal.
2. Back Shell (Provides Overall Strength and Breathability)
Function: The back shell is a multi-layered structure outside the surface layer. It supports the overall strength of the mold shell (preventing deformation or collapse during pouring) while ensuring breathability (discharging gases from the cavity and preventing porosity in the casting).
3. Specialized Applications for High-Demand Castings
High-temperature alloy castings: such as aircraft engine turbine blades (pouring temperatures of 1500-1600°C), require the mold shell to withstand extreme temperatures. Mullite sand's high refractoriness can replace the more expensive zircon sand (melting point 2550°C, but expensive), meeting high-temperature resistance requirements while reducing costs.
For reactive metal castings: such as aluminum alloys and magnesium alloys (which are highly reactive and easily react with the SiO₂ in quartz sand to form inclusions), mullite sand's chemical stability can reduce reactivity and prevent the formation of "oxidation inclusions" in the casting.
For large precision castings: such as wind turbine gearbox housings (which can weigh several tons), the mold shell requires higher structural strength. The backing layer formed by mullite sand and binder is high-strength, reducing the risk of mold expansion and collapse.
4. Combination with Other Refractory Materials
In actual production, mullite sand is often used in combination with other materials to optimize mold shell performance:
Combination with zircon sand: zircon sand is used as the surface layer (to ensure a higher surface finish) and mullite sand as the backing layer (to reduce costs). This is suitable for castings with extremely high surface requirements, such as aerospace parts.
Combined with quartz sand: For castings with lower temperature requirements (such as copper alloy, melting point 1083℃), it can partially replace quartz sand and use the low expansion of mullite sand to reduce shell cracks.
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Reference Process For Precision Casting Shell Making
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The general surface slurry, zirconium powder
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325 mesh+silica sol
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Sand: zirconium sand 120 mesh
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Back layer slurry
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325 mesh+silica sol+mullite powder 200 mesh
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Sand: mullite sand 30-60 mesh
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Reinforcement layer
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Mullite powder 200 mesh+silica sol
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Sand: mullite sand 16-30 mesh
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Sealing slurry
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Mullite powder 200 mesh+silica sol
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_
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Company Profile
Shandong Robert New Material Co., Ltd. is located in Zibo City, Shandong Province, China, which is a refractory material production base. We are a modern enterprise that integrates the research and development, production, sales, kiln design and construction, technology, and export refractory materials. We have complete equipment, advanced technology, strong technical strength, excellent product quality, and good reputation. Our factory covers over 200 acres and an annual output of shaped refractory materials is approximately 30000 tons and unshaped refractory materials is 12000 tons.
Our main products of refractory materials include: alkaline refractory materials; aluminum silicon refractory materials; unshaped refractory materials; insulation thermal refractory materials; special refractory materials; functional refractory materials for continuous casting systems.
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