The quality of aluminum casting has a great influence on the performance of mechanical products. For example, the performance and dimensional stability of aluminum castings of machine tools directly affect the accuracy and maintenance life of machine tools; the accuracy and surface roughness of impeller, shell and inner cavity of hydraulic parts of various pumps directly affect the working efficiency, energy consumption and cavitation development of pumps and hydraulic systems; the quality of aluminum castings such as cylinder block, cylinder head, cylinder liner, piston ring and exhaust pipe of internal combustion engine is directly affected Strength and resistance to chilling and heat shock directly affect the working life of the engine. In a word, the quality of aluminum casting has a great influence on the performance of mechanical products. Therefore, in the process of manufacturing casting products, each process is strictly controlled and inspected in accordance with the process rules and technical conditions to produce qualified products.

According to the investigation, the following methods can help to solve the oxidation problem of castings: high voltage and high current density impact method. In other words, high voltage electric shock is used in the early stage of casting oxidation, so that the oxidized parts are connected into pieces by electric shock. Surface grinding method. This method is to fill the gap left by the oxidized part with the polished aluminum mill, so that the generated gaps are connected together as a bridge. Third, surface shot peening. This method is to knock the gap with a round head hammer and close it by knocking, so as to achieve the purpose of connecting into pieces. The practice shows that the above three conditions can avoid the phenomenon of cracks in the aluminum casting due to oxidation, so that the quality can be achieved.

The mirror effect of aluminum casting aluminum alloy castings comes from two aspects: one is that the substrate itself should be mirror like, the other is that the oxide film should be highly pure and transparent. Oxalic acid oxide film and chromic acid oxide film have color, which are not clear and transparent, naturally not considered.

For sulfuric acid oxide film, the main factors affecting the transparency are: purity of oxide film / thickness of oxide film / porosity of oxide film / sealing quality. If there are too many impurity ions (or atoms) such as Si / Mn / Fe / Cu / Cr in the oxide film, the purity of the oxide film will be low and the transparency will be reduced.

Although the oxide film is transparent, there will be some light scattering loss. When the thickness of the oxide film increases, the transparency will also decrease.

Annealing treatment of cast aluminum parts: the process of heating aluminum alloy castings to a higher temperature, generally about 300 ℃, and cooling to room temperature with furnace after holding time is called annealing. During the annealing process, the solid solution decomposes and the phase particles gather, which can eliminate the internal stress of the casting, stabilize the casting size, reduce the deformation and increase the plasticity of the casting. Common defect characteristics of aluminum casting: oxide slag is mostly distributed on the upper surface of the casting, in the corner of mold ventilation. The fracture surface is mostly gray white or yellow, which can be found by X-ray fluoroscopy, mechanical processing, alkaline washing, acid pickling or anodizing. The experimental results show that adding appropriate additives into NaOH solution can produce good polishing effect. The exploratory experiment also found that the reflectivity of aluminum surface can reach 90% after DC constant voltage electrolytic polishing with glucose NaOH solution under certain conditions. However, due to the unstable factors in the experiment, further research is needed.

The quality of cast aluminum includes appearance quality, internal quality and service quality. Appearance quality refers to surface roughness, surface defect, dimension deviation, shape deviation and weight deviation of castings; internal quality mainly refers to chemical composition, physical properties, mechanical properties, metallographic structure, as well as holes, cracks, inclusions and segregation inside the castings; service quality refers to the working durability of aluminum castings under different conditions, including, and chilling resistance Heat shock, fatigue, shock absorption and other properties, as well as machinability, weldability and other process properties.

Due to the influence of many factors, the defects such as air hole, pinhole, slag inclusion, crack and pit often appear. The commonly used repair equipment is argon arc welding machine, resistance welding machine, cold welding machine, etc. For casting defects with low quality and appearance requirements, argon arc welding machine and other welding machines with high heat and high speed can be used to repair the defects.

The quality of aluminum casting has a great influence on the performance of mechanical products. For example, the performance and dimensional stability of machine tool castings directly affect the accuracy and maintenance life of machine tools; the accuracy and surface roughness of impeller, shell and inner cavity of hydraulic parts of various pumps directly affect the working efficiency, energy consumption and cavitation development of pumps and hydraulic systems; the strength of aluminum castings such as cylinder block, cylinder head, cylinder liner, piston ring and exhaust pipe of internal combustion engine is strong The working life of the engine is directly affected by the performance of the engine.