The quality of die-casting aluminium has a great influence on the performance of mechanical products. For example, the wear resistance and dimensional stability of machine tool aluminium castings directly affect the accuracy and life-span of machine tools; the dimensions, profile accuracy and surface roughness of impellers, shells and hydraulic chambers of various pumps directly affect the working efficiency of pumps and hydraulic systems, energy consumption and the development of cavitation erosion; and the cylinder block of internal combustion engines. The strength and heat resistance of aluminium castings such as cylinder head, cylinder liner, piston ring and exhaust pipe directly affect the working life of the engine.
The weight and size range of aluminium castings are very wide. The lightest weight is only a few grams, the heaviest can reach 400 tons, the thinnest wall is only 0.5 mm, the thickest can exceed 1 meter, and the length can be from several millimeters to more than ten meters, which can meet the requirements of different industrial sectors. In foundry production, the quality of aluminium castings should be controlled and inspected. First of all, we should formulate the process codes and technical conditions from raw materials and auxiliary materials to the control and inspection of each specific product. The control and inspection of each process are strictly in accordance with the process code and technical conditions. Finally, the quality of finished aluminium castings is inspected. Reasonable testing methods and appropriate testing personnel should be equipped. Generally, the surface roughness of aluminium castings can be judged by comparing the sample blocks, and the surface micro-cracks can be checked by coloring method and magnetic powder method. The internal quality of aluminium castings can be checked and judged by means of audio, ultrasonic, eddy current, X-ray and gamma-ray.