The ceramic sand shell type process mainly uses the coated sand with the ceramic sand as the original sand, and is a special casting process in which the sand shell is casted by the core shooting machine. Compared with the shell molding process of traditional silica sand coated sand, it has the following advantages
1. Refractoriness
The refractoriness of ceramic sand is above 1800℃, and the refractoriness of silica sand is generally around 1600℃, especially in the castings of stainless steel, high alloy steel and heat-resistant steel with high angle temperature. It can effectively reduce defects such as sticky sand caused by insufficient refractoriness of molding sand.
The high refractoriness of the ceramic sand can make the sand mold not need to paint or stick to the sand, which not only ensures the air permeability of the sand mold, but also saves the cost of coating and the labor cost of the process.
2. The amount of coated sand resin added and the amount of gas generated
The shape of the orb sand is spherical, and the sand is point-bonded when the coated sand is hardened. Compared with the surface bond of the silica sand-coated sand, the strength of the point bond can reach the surface bond with the same amount of resin added. more than double the strength.
Then, under the condition of reaching the same strength, the amount of coated sand resin added to the ceramic sand can be reduced by at least 30%-40%, and the gas generation of the molding sand can be reduced by at least half (the new silica sand itself will also generate a certain amount of gas during casting). The use of the ceramic sand coated sand shell mold can effectively reduce the casting pores caused by the large amount of gas generated in the molding sand.
3. Moulding sand consumption
The strength of Baozhu sand coated sand is about twice higher than that of silica sand, and the sand consumption of the sand shell is generally reduced by about 30%-40%. According to the iron-sand ratio of 1:1 in the conventional shell molding process, Baozhu sand-coated sand can save 200-300 tons of molding sand compared with silica sand-coated sand to produce 1,000 tons of castings, thus effectively reducing the cost of molding sand and the amount of molding sand turnover.
4. Casting quality
Silica sand will thermally expand during the pouring process. The thermal expansion of new sand is 5.5×10-7/°C (0~1000°C). It is easy to form microscopic cracks on the surface of the casting, and even lead to the deformation of the casting in severe cases. The expansion rate of orb sand is 1.3×10-8/℃ (0~1000℃), and the thermal expansion rate is much smaller than that of silica sand, which can effectively improve the quality of castings, reduce the scrap rate of castings, and reduce the man-hours required for welding repairs during post-processing.
5. Personnel and production process
Baozhu sand is spherical sand. Compared with the polygonal sand of silica sand, it has good fluidity. The sand shell is easy to be filled during shell making, and the compactness of the sand shell is guaranteed. The scrap of castings due to insufficient sand mold strength can be effectively reduced.
After the casting is unpacked, it is basically possible to do without manual sanding, saving labor costs. According to the feedback of our customers, the cleaning staff can be reduced by more than one third, which effectively saves labor costs.
6. Clean and environmentally friendly
Silica sand has the defects of broken and large dust, which not only causes serious pollution to the surrounding environment, but also easily causes production personnel to suffer from occupational diseases such as pneumoconiosis. The property of the ceramic sand not breaking when heated is a good solution to this problem. It not only improves the working environment of the production personnel, but also avoids the disadvantage that the particle size of the molding sand becomes finer and finer when it is reused.