The cylinder head of a certain type is the main component of the diesel mechanism of special vehicles, which is used to seal the upper part of the engine body, form the combustion chamber space with the piston and cylinder liner, and ensure the smooth progress of the intake and exhaust process of the diesel engine. The cylinder head is a fixed part of diesel engine, which is generally cast with aluminum alloy. In order to dissipate heat, a water chamber is cast inside the cylinder head. Under the pressure of the water pump, the coolant enters the water jacket of the cylinder block from the water tank or radiator, then enters the water jacket inside the cylinder head through the water outlet hole of the cylinder head, and then discharges from the water outlet hole on the end face of the cylinder head, enters the water outlet pipe of the cylinder head, and finally returns to the water tank.
This type of cylinder head is a complex spatial structure with large heat engine load, irregular shape, large wall thickness difference and asymmetric structure. The aluminum alloy cylinder head is a 6-cylinder cylinder head, and the overall dimension of the casting is 1362 mm × 244 mm × 152 mm, weighing about 90 kg. Due to the large casting plane and curved surface, the inner cavity has two layers of water cavities and a complex curved surface structure, and there are many hot spots, which are not conducive to sequential solidification. The average wall thickness of the casting is about 10 mm, which is a thin-walled complex part. During casting, it is easy to produce air holding, cold shut, insufficient pouring and other phenomena. Therefore, the casting process is poor, and it is difficult to smooth mold filling, and the casting process is difficult. In the process of batch trial production of castings, porosity and shrinkage defects frequently occur, as shown in the figure.
This paper mainly studies the defects of a certain type of cylinder head casting in the production process, analyzes the causes of the defects, analyzes and optimizes the existing casting process. The research significance of this paper is to solve the frequent defects of a certain type of cylinder head in the process of mass production, optimize the traditional low-pressure casting curve design and casting process design, and put forward a new idea and new idea for the cylinder head casting process design.