Sand Casting Process for Complex Diesel Engine Cylinder Head

With the rapid development of the global automotive industry, lightweight and low fuel consumption have become the main goals of domestic automobiles. Compared with cast iron, aluminum engines have many advantages and have been widely recognized in the automotive industry market. In the field of high-end weapons and equipment, the improvement of mobility and operational radius of combat vehicles has put forward an urgent demand for aluminum diesel engines that can withstand high explosive pressure and have high power and torque. The high-end aluminum diesel engine for combat vehicles, compared with the aluminum engine for ordinary vehicles, requires the engine to withstand a high explosive pressure of more than 14 MPa, ensure that the thermal load and mechanical load do not exceed the upper limit that the aluminum engine can withstand, and also need to withstand high frequency vibration under thermal shock and impact load, to meet the service life of more than 700 h. Therefore, the overall structure of aluminum diesel engine for combat vehicles is particularly complex, and the requirements for internal quality, mechanical performance and fatigue performance are more stringent than those of aluminum automotive engine.

(1) Combined with numerical simulation technology, carry out sand casting process design of diesel engine cylinder head for combat vehicles, use 3D printing to rapidly prepare cylinder head blank, and develop complex cylinder head sand casting technology in a short time, laying a foundation for later batch production and development of cylinder head.

(2) The pore in the cylinder head inner cavity is affected by the gas content of the alloy, the solidification cooling rate, the gas evolution of the sand core and the coating application. By optimizing the structure of the sand core, adjusting the alloy melting process, the coating application method and the sand casting process parameters, the pore formation can be effectively suppressed, and the internal quality of the alloy can meet the technical requirements.

(3) The properties of sand casting body are obviously affected by secondary dendrite arm distance and pinhole grade. With the secondary dendrite arm distance from 21 μ M increased to 56 μ m. The tensile strength of the alloy is reduced by 25 MPa, the yield strength is reduced by 6 MPa, and the elongation is also reduced from 8% to 4.5%; When the arm distance of secondary dendrite is 40~45 μ Within m, when the pinhole of sand mold casting rises from 0 to 5, the tensile strength, yield strength and elongation of the alloy gradually decrease, with the maximum decrease of 25 MPa, 29 MPa and 3.5% respectively.

As an important part of the engine, the cylinder head is an important working part of the engine, including the key functional space such as oil passage, cooling water jacket, air passage, etc. The upper part has a camshaft, and the lower part forms a combustion chamber with the cylinder block and piston. The working conditions are poor, and the requirements for dimensional accuracy and mechanical properties are high. In addition, the sand casting structure is complex, and the wall thickness is uneven. It is a typical thin-walled complex sand casting. Compared with the civil automobile engine, the aluminum diesel engine cylinder head for a certain type of combat vehicle adopts a more complex design scheme. The overall metallurgical quality of the cylinder head is required to meet the technical standard for Class I sand castings, and the performance of the sand castings requires that the body tensile strength is more than 330 MPa, the elongation is more than 3%, the airway wall tensile strength is more than 250 MPa, and the elongation is more than 3%. At the same time, in order to meet the fatigue strength requirements of the cylinder head, Only level 2 is allowed for air duct wall and fire surface pin hole of sand casting. In this paper, the rapid development of ZL702A complex diesel engine cylinder head is carried out.