Silica sol or water glass will be used in the third step of the process. It is made into a slurry with other refractory materials (zirconium powder or mullite powder), strengthening agent, defoaming agent, and wetting agent. After repeated ten times or Dozens of soaking and drying to make a mold.
First of all, both belong to lost wax precision casting. The difference is the surface quality of the mold shells made. The mold surface cast by silica sol has a better surface and higher dimensional accuracy, which is more suitable for precision casting. The products manufactured by it have good surface smoothness, small deformation, small shrinkage ratio, precise size, and no secondary processing. The corresponding cost is also higher than that of water glass casting.
Secondly, the silica sols are basically small products, while the water glass lost foam products are relatively large.
Third, the drying and hardening of shell molds are different. Sodium silicate requires ammonium chloride and other hardeners, while silica sol shell molds can be dried and hardened in a constant temperature and humidity space. Generally speaking, the production cost of the water glass process Low, short production cycle, poor product surface quality, mainly used for carbon steel and low alloy steel castings; silica sol process has a high production cost, but has a long production cycle and good product surface quality, mainly used for high alloy steel and stainless steel Products.
In summary, the castings produced by the silica sol casting process have high dimensional accuracy, which can reach the CT4-8 level specified in GB/6414-1986, the surface roughness value is low, and can reach Ra0.8-6.3um, and the machining allowance is small, even Non-cutting processing can be realized; the silica sol casting process can produce more complex castings with geometric switches. The minimum wall thickness of the casting can reach 2.5mm and the minimum aperture can reach 1mm. The weight of the casting: max. 20kg, min. 0.003kg The length of the casting: max. 500mm, min. 10mm; the cost is twice as high as the water glass precision casting process.