The engine is called the “heart” of the automobile, and the cylinder head is one of the most important, most complex and most difficult key parts in the engine. Cylinder head is a part with large size, complex shape and high technical requirements. Its production level directly reflects the technological level of a foundry. The quality of castings requires that the water pressure and air pressure leakage test be carried out. The water, oil and air circuits shall be unobstructed. The wall thickness of cylinder barrel shall be uniform. The surface of cylinder head shall be smooth and the structure shall be uniform. The internal defects such as shrinkage cavity, shrinkage porosity and air hole are not allowed.
At present, there is still a big gap between China and foreign countries in the quality of casting engine cylinder head: the dimension accuracy is generally grade iso6-8 in foreign countries, and it has been very good to reach grade iso8-10 in China. With the continuous improvement of engine efficiency, the internal structure of engine becomes more and more complex, and the technical requirements of engine become higher and higher. There are several casting processes at home and abroad:
1) For the metal mold casting, the 12 station metal mold casting machine manufactured by mecanasa company is used in mactingen aluminum casting plant of Benz Automobile Company of Germany. In 1987, Tianjin automobile engine factory designed and manufactured the aluminum alloy cylinder head automatic metal mold casting unit and put it into production. In addition, such enterprises as FAW and Shanghai Volkswagen also used metal mold gravity casting to mass produce cylinder heads.
2) High pressure casting, in the 1990s, BMW, Renault, GM, Honda and other enterprises have used a large number of pressure casting machines to produce aluminum alloy cylinder head. In 2001, Guangzhou Dongfeng Honda engine company completed the construction of the first pressure casting production line in China.
3) For medium pressure casting, toukei company of Japan has improved the defect that sand core can not be used in pressure casting and put forward the method. The injection pressure ratio is reduced from 55-120mpa to 5-30mpa.
4) In low-pressure casting, foreign general motors and Benz automobile company adopt the casting method to produce the cylinder head with complex inner cavity structure.
5) lost foam casting, in 1958, the American H.F.Shroyer made use of volatile foam pattern to manufacture metal castings and obtained patents. In 1964, T.R.SMITH and H.Nellen of Germany published the patent of lost foam casting using binders dry sand molding. In 1984, Ford Motor Co pioneered the use of EPC technology to build an automatic production line for aluminum alloy intake pipes. In the 1990s, EPC technology was introduced into China. For example, in 1990, Beijing foundry built a 5000 ton EPC production line; in 1993, Wuxi foundry built a 1000 ton EPC production line; by 2007, China’s EPC production had reached 648kt, an increase of 42.6 times over 1995, ranking first in the world in terms of production and number of enterprises.
