Lost foam casting (also known as solid casting) is to bond and combine paraffin or foam models similar in size and shape to castings into model clusters. After brushing refractory paint and drying, they are buried in dry quartz sand and vibrated for modeling. The new casting method is a new casting method in which the model is gasified by pouring down, and the liquid metal occupies the position of the model, and solidifies and cools to form a casting.
Shell mold casting process is a kind of base sand with high-quality selected natural sand, through special performance resin coating system and the most ideal process technology. The most perfect combination of fluidity, surface roughness of castings, etc., are widely used in automobile engines, diesel engines, hydraulic parts and other industries.
Compared with lost foam casting, coated sand casting
has the following advantages:
1. The pollution is small, and the worksite environment is obviously improved. Since the clay sand is added with a large proportion of coal powder, which is a combustion-supporting material, it is mainly used to increase the appearance quality and air permeability of the workpiece. The coal powder added to the sand cannot be reused, resulting in a waste of resources. Ash residues after combustion have a great impact on the quality of our working environment. At the same time, the reducing gas and PM2.5 produced during combustion cause serious pollution to the atmosphere. Although the molding method based on coated sand also has a certain impact on the environment, after all, it uses a small amount of sand, and at the same time, all the waste sand after use is recycled. The worksite is clean and free of dust pollution.
2. The sand coating layer is thin, the dosage is small, the production cost is low, the waste is small, and the used molding sand can be recycled and reused. Due to the thin sand coating layer of this molding method, 5-10mm coating sand layer is usually designed according to the wall thickness of the live piece, while the minimum sand coating amount for clay sand molding is usually 30-50㎝, and the amount of sand used is 10-20 mm of coated sand. times. Although clay sand can also be recycled for the second time, the high content of coal powder, bentonite and other additional raw materials have been basically consumed, and the quality of the sand has been greatly reduced, which affects the appearance quality of the product. After the molding sand of coated sand is roasted at high temperature, the expansion is greatly reduced, the process steps of pickling are reduced in the secondary use, and the addition amount of solid resin and curing agent is also greatly reduced, which reduces the production cost.
3. Change the appearance quality of the blank, reduce the cutting allowance, the process yield is high, and the quality is stable. Due to the low hardness of the clay-sand molding sand and the large concessionality, the casting defects such as box expansion, sand expansion, sand loss, porosity, shrinkage and other casting defects are serious, which not only cause poor product appearance but also have many internal casting defects, which are serious and serious. The service life of the product is affected, and the scrap rate is high. The aggregate in coated sand molding is pickled or calcined at high temperature, which reduces the expansion of the sand mold after combustion, and has many advantages such as high strength and small gas generation after curing. Appearance quality, inherent casting defects, and product size accuracy are far superior to those produced by clay sand molding.
4. Improve the internal quality of products. Due to the fast cooling rate of the coated sand during casting, the graphite morphology of the casting is greatly improved, the mechanical properties of the product are improved, and the service life of the product is increased. The products produced by coated sand molding, especially ductile iron, are far superior to those produced by clay sand molding regardless of spheroidization level, matrix structure, hardness, tensile strength, yield strength, etc. Invisibly improve the inherent quality of the product. It increases the service life of the product and indirectly provides a strong guarantee for meeting customer needs.
5. Coated sand molding adopts automatic production line operation, which improves production efficiency, reduces the labor intensity of workers, and shortens labor time. The traditional clay sand molding adopts manual molding or molding machine molding. The labor intensity of workers is high and the work efficiency is low, which is 1/3 to 1/4 of the molding efficiency of the production line.