Casting precision casting forming technology

Generally speaking, precision casting of automobile castings mainly refers to EPC and investment casting technology. With the development of automobile casting forming technology, casting precision forming is a kind of casting forming method. The casting produced by this kind of forming method can be directly used without cutting or less cutting. With the improvement of dimensional accuracy of castings, casting precision forming technology has developed rapidly in recent years. A series of new casting forming methods, such as precision sand casting, lost foam casting, controllable pressure casting and pressure casting, have emerged.

Cosworth casting method is a method developed by the United Kingdom, which uses zirconium sand core combination and electromagnetic pump to control pouring. It has been successfully used in the mass production of aluminum alloy cylinder block, and there have been many process variations, such as using low-pressure pouring instead of electromagnetic pump pouring. The aluminum alloy cylinder with a wall thickness of 3.5-4.0mm can be produced by this kind of casting method, which is the representative process of precision sand casting at present.

Since the invention of EPC process in 1965, the main automobile castings are cylinder block, cylinder head, air inlet and exhaust pipe, etc., and a large-scale production has been formed. Since the introduction of EPC Technology in China in the 1990s, it has begun to take shape and become the most widely used high-tech in the transformation of traditional foundry industry. At present, there are three investment casting processes in China: water glass shell, composite shell and silica sol shell. The surface quality of the castings used in the production of silica sol shell for automobile products can reach Ra1.6 μ m, the dimensional accuracy can reach cT4, and the minimum wall thickness can reach 0.5 ~ 1.5 mm. Dongfeng Automobile Precision Casting Co., Ltd. adopts silica sol + water glass composite shell making process to produce complex structure integrated casting, which significantly reduces the production cost. The development trend of investment casting technology is that the distance between the casting and the final product is getting closer and closer, and the complexity and quality level of the products are getting higher and higher. The application of CAD, cam and CAE has become the main technology of product development, and professional cooperation has begun to appear.

Based on the high-pressure casting technology, vacuum casting, oxygen filling die casting, semi-solid metal rheologic or thixotropic die casting and other process methods are developed to eliminate casting defects, improve internal quality and expand the application scope of die casting. In the process of squeeze casting, the melt is filled and solidified under pressure, which has the advantages of stable, no metal splashing, less oxidation loss of liquid metal, energy saving, safe operation and reduction of casting hole defects. It has been widely used in the development and application of high-performance aluminum alloy castings such as aluminum alloy subframe.

The continuous growth of automobile production demands the development of foundry production in the direction of high quality, excellent performance, near net shape, multiple varieties, low consumption and low cost. Because about 15% ~ 20% of the parts of a whole vehicle are castings. This requires the foundry industry to continuously apply various new technologies and materials to improve the overall level of casting. The casting precision casting technology can meet the above requirements of automobile castings, and its application will also cover different casting production processes of automobile castings.

In order to adapt to the increasingly stringent requirements of environmental regulations, the automobile is developing towards lightweight. For every 10% reduction in the dead weight of the vehicle, the fuel consumption can be reduced by 5.5%, the fuel economy can be increased by 3% ~ 5%, and the emissions can be reduced by about 10%. The main way to realize the lightweight of automobile castings is to use aluminum magnesium alloy castings, develop large-scale complex structure integrated castings and widely use the casting precision forming technology. Therefore, on the basis of widely using digital technology, the R & D and production of automobile castings are required to be realized by means of high-performance casting materials and wide application of automation equipment, so as to meet the needs of modern automobile industry.