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Comparison of Ceramic sand shell molding process and silica sand shell molding process


The Ceramic sand (Also called Ceramsite sand) shell molding 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 poured by the core shooting machine. Compared with the traditional shell type process with 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 casting of stainless steel, high-alloy steel and heat-resistant steel and other materials with high angular temperature. The advantages by using ceramic sand are very obvious. It can effectively reduce sand sticking and other defects caused by insufficient refractoriness of molding sand.

The high refractoriness of Ceramic sand allows the sand mold to be non-sticky without painting refractory coating, which ensures the air permeability of the molding sand and saves the cost of coating and labor cost for the process.

2. The amount of resin added and the amount of gas generated by the coated sand

The sand shape of Ceramic sand is spherical. When the coated sand is hardened, molding sands are bonding point to point. While the bonding of silica sand coated sand are with side by side way, the strength of the sand mold can increase more than 100% comparing side by side bonding silica sand with the same consumption of resin.

In the same way, if we want to get same sand strength adopting the two kinds of sands. The amount of resin added in the coated sand of Ceramic sand can be reduced by at least 30%-40%, and the amount of gas generated by 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 pearl sand coated sand shell type can effectively reduce the porosity of castings caused by the large amount of gas generated by the molding sand.

3. Consumption of molding sand

The strength of Ceramic sand coated sand is about twice that of silica sand, and the consumption of molding sand is generally reduced by about 30%-40%. According to the 1:1 ratio of iron to sand in the conventional shell molding process, to manufacture 1000 tons castings, the consumption of Ceramic sand coated sand can save 200-300 tons sand compared with silica sand coated sand, thereby effectively reducing the cost of molding sand and the amount of molding sand turnover.

4. Casting quality

Silica sand often get thermal expand during the pouring process. The thermal expansion of new silica sand is 5.5×10-7/°C (0~1000°C), which is easy to form micro-cracks on the surface of the casting, which may even lead to deformation of the casting in severe cases. The expansion rate of ceramic sand is 1.3×10-8/°C (0~1000°C), and the thermal expansion rate is much smaller than that of silica sand, which can effectively improve the quality of castings, reduce the rejection rate of castings, and reduce the time required for welding repair during post-processing.

5. Labor cost and production process

Ceramic sand is spherical sand. Compared with the polygonal sand of silica sand, it has good fluidity. The sand shell is easy to fill during shell making, sand is filled tighter with ceramic sand. Defect castings can be effectively reduced due to insufficient sand strength.

When open the sand box after casting, ceramic can shake out naturally. No need to remove sand by workers thus saving labor costs. According to the feedback from our customers, the cleaning staff can be reduced by more than 1/3,which effectively saves labor costs.

6. Clean and environmentally friendly

Silica sand has the defects of weak and making many dust, which not only causes serious pollution to the surrounding environment, but also easily causes occupational diseases such as pneumoconiosis to operators. Ceramic sand doesn’t broke at high temperature. This advantage can solve disease problems by developing working environment. In the meantime, avoids the disadvantages of finer and finer molding sand during repeated use.1-2009191P03N20.jpg

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