The engine is known as the “heart” of the automobile, and the cylinder head is one of the most important, complex and 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 process level of a foundry. The casting quality requires water pressure and air pressure leakage inspection test. The water, oil and gas circuits are required to be unobstructed, the wall thickness of the cylinder barrel is uniform, the surface of the cylinder head is smooth and the structure is uniform, and casting defects such as shrinkage cavity, porosity and air hole are not allowed inside.
At present, there is still a big gap between China and foreign countries in the quality of cast engine cylinder head: the dimensional accuracy is generally iso6-8 in foreign countries and iso8-10 in China. With the continuous improvement of engine efficiency, the internal structure of the engine becomes more and more complex, and the technical requirements of the engine become higher and higher.
There are several casting processes at home and abroad:
1) For metal mold casting, the mettingen aluminum foundry of Mercedes Benz adopts the 12 station metal mold casting machine manufactured by mecanasa company. In 1987, Tianjin automobile engine manufacturing plant designed and manufactured an automatic metal mold casting unit for aluminum alloy cylinder head and put it into operation. In addition, enterprises such 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 widely used pressure casting machines for the production of aluminum alloy cylinder heads. In 2001, Guangzhou Dongfeng Honda engine company led the construction of the first pressure casting production line in China.
3) Medium pressure casting is proposed by toukei company of Japan through improving the disadvantage that sand core cannot be used in pressure casting. The injection ratio is reduced from 55-120mpa to 5-30mpa.
4) Low pressure casting is used by foreign general motors and Mercedes Benz to produce cylinder heads 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 of the United States and h.nellen of Germany issued patents for the production of EPC Castings by using binder free dry sand molding; In 1984, Ford took the lead in using EPC technology to build an automatic production line of aluminum alloy intake pipe. In the 1990s, EPC technology was also introduced in China. For example, in 1990, Beijing Songzhuang foundry built a 5000 ton lost foam casting production line; In 1993, Wuxi Yongxin foundry built a 1000 ton lost foam casting production line; By 2007, China’s production of lost foam molds had reached 648kt, an increase of 42.6 times over 1995. Its production and the number of enterprises ranked first in the world.