Although the precision casting industry was established in the mid-1950s and gradually popularized and applied, the real rapid development has been in the more than ten years since the early 1990s, especially in recent years. At present, there are two types of horizontal casting processes in China's investment casting. The first type of enterprises adopt the medium-temperature molding method and the investment casting process of silica sol or ethyl silicate binder, which is the international common investment casting process. . The second type is a low-temperature mold and water glass binder shell-making process, and a composite process using a medium-temperature or low-temperature mold, a surface layer using a silica sol, and a reinforcing layer using a water glass shell, which can guarantee High dimensional accuracy and surface quality conditions are reduced at low cost. According to statistics, in 2001, more than 350 manufacturers of the first category were used, with an annual output of 75,000 tons and an annual output value of 3.28 billion yuan. The second type of process manufacturers (including composite processes) exceeded 1,350, with an annual output of nearly 200,000 tons. The output value is 1.5 billion yuan. In 2002, the output reached 321,000 tons and the output value reached 5.49 billion yuan. The output in 2002 was 6.4 times that of 1988. The output value was 16.6 times that of the 330 million in 1988.
2. Process level, casting quality and product category From the perspective of use and quality, the current castings produced by precision casting are mainly: castings for aviation and gas turbines produced by the first type of process, the quality has reached the international level, there are 50 manufacturers, the annual output 0.5 million tons, with an annual output value of 400 million yuan; commercial precision castings produced by the first type and composite process, the quality inspection items and standards are lower than aviation parts, there are about 300, the annual output is 70,000 tons, and the annual output value is 2.88 billion. Yuan; using the second type of process to produce the investment precision and surface roughness requirements of the investment casting blanks, there are about 1,350, the annual output of nearly 200,000 tons, with an annual output value of 1.5 billion yuan. It can be seen from the specific gravity distribution of the castings of the three quality levels that the high-level aerospace precision castings have a small output, accounting for only 1.8% of the total output, and the general commercial castings account for 25.6%, and the quality is still below the international standard. Castings accounted for 72.6% of the total output. The various aspects of China's investment casting process have made great progress. There are also many new materials, new processes and new equipment that have a great influence on the development of investment casting, such as water-soluble core, ceramic core, metal material improvement, large scale. Investment casting technology, titanium alloy investment casting, directional solidification and single crystal casting, filtration technology, hot isostatic pressing, rapid prototyping technology, computer application in investment casting and mechanized automation, etc., enable investment casting not only to produce Small castings and the ability to produce larger castings. The largest investment castings have a profile size of nearly 2m and a minimum wall thickness of less than 2mm. At the same time, the investment castings are also more precise, in addition to the linear tolerances, the parts can also achieve higher geometric tolerances. The surface roughness of investment castings is also getting smaller and smaller, reaching Ra0.4um.
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