Characteristics and applications of coated sand

       Characteristics and application of cladding sand, talking about cladding sand, we have to start from the emergence of cladding sand technology, China's cladding sand technology began in the mid-1950s, and production was discontinued in the 1960s. However, in the 1980s, due to the rapid development of the automotive industry and the need for export of machinery products, the casting quality put forward higher requirements, promoting the development of the production and application of film-coated sand technology. The development of new coated sand production technology has been close to the international advanced level in the same period. in the early 1990s, the rapid development of the cover sand plant, new products, new technologies continue to emerge, to the 21st century, China's annual production and sales of the cover sand industry has reached more than 900,000 tonnes, widely used in the production of automotive blocks, cylinder heads, intake manifolds, a variety of pipe fittings, pumps and other complex castings. Coated sand is favoured by the foundry industry, what are its characteristics? Next, I will analyse the raw material manufacturers of coated sand.

　　 Coated sand sand mould in the moulding and core making before the sand surface has been covered with a layer of solid resin film sand, core sand is called coated sand, also known as shell (core) sand. Coated sand is mainly quartz sand as raw sand, thermoplastic phenolic resin, urea ketone and reinforcing agent as raw materials. There are two kinds of processes: cold coating and hot coating. But the earlier is thermosetting resin sand, process is powder thermosetting phenolic resin and quartz sand mechanical mixing, curing after heating. Nowadays, it has been developed to prepare film sand using thermoplastic phenolic resin and potential curing agent i.e. urotropin, and by coating process and lubricant. When the coated sand is heated, the surface coated resin melts, thus curing the coated sand.

　　 With coated sand it is possible to make castings as well as cores, and coated sand and cores can be used in conjunction with each other or with other sands. It can also be used for metal gravity casting or low-pressure casting, iron clad sand casting, hot centrifugal casting, not only for steel castings, but also for non-ferrous metal castings. Compared with other resin sand, coated sand has the following characteristics.

　　 1. Coated sand has suitable strength properties, for high-strength shell and core sand, medium-strength temperature box sand, low-strength non-ferrous alloy sand can meet the requirements.

　　 2. Good fluidity, good sand moulding, clear contour, can make complex sand core.

　　 3. During the casting process, the surface quality of sand core is good, dense and not loose. Even with little or no coating, it can obtain good surface quality of castings.

　　 4. Good collapsibility is conducive to casting clean, improve product performance.

　　 5. The sand core is not easy to absorb moisture, and the storage strength is not easy to decrease in regular time, which is good for storage, transport and use.

　　 The above content is summarised by the manufacturer. With the increasingly fierce competition in the foundry industry, the requirements for castings are becoming more and more stringent. In the casting production, coated sand and its shell type (core) has become one of the important moulding materials to improve the quality of castings and production efficiency.