Annealing of aluminum die castings is to firstly heat the work piece. Then when it is heated to an appropriate temperature, slowly cooling the die castings according to the different materials. Normalizing is to heat the work piece to a suitable temperature and then cool it in the air. It is mainly used to improve the cutting function of the material. It can also be used on some parts which do not have strict requirement. Quenching is firstly heating the work piece and then rapidly cooling it in a quenching medium such as water or other inorganic salt solutions. After this process, the steel parts produced will become hard and brittle.
Because metal aluminum and aluminum alloy have good fluidity and plasticity, aluminium die castings can be made into various complex shapes, and have high precision and surface finish. This greatly reduces the amount of machining of the castings, reduces labor intensity, and also saves electricity and metal materials.
The following methods can be used to detect whether there are cracks in the aluminum die castings or not:
1. Ultrasonic flaw detection.
Ultrasonic testing and ultrasonic thickness measurement of various metal pipes, plates, castings, forgings and welds. When ultrasonic waves encounter defects such as cracks, voids, segregation during propagation, the acoustic parameters such as ultrasonic speed, amplitude and frequency will change accordingly.
2. Magnetic particle inspection.
It is suitable for non-destructive testing of ferromagnetic material casting, forging and other machined parts.
3. Ultraviolet lamp is cheap, reliable and easy to operate.
It is suitable for sink leak detection of various pipelines, inspection of uniform coating, and detection of impurities or stains.
4. Radiographic inspection.
Radiographic inspection can be divided into three types: X-ray, Y-ray and high-energy ray inspection. X-ray radiography is based on the attenuation law of rays in substances and the actinic and fluorescent effects of certain substances. From the perspective of ray intensity, when irradiated on the work piece, the ray intensity is J0. Since the material attenuates the rays, the rays passing through the work piece are weakened to JC. If the work piece has a defect, the actual thickness of the work piece through the radiation at that point decreases, and the intensity of the rays passing through is JA, or JB which is higher than without defects. From the perspective of the actinic effect of the rays on the film, the strong part of the rays has a strong actinic effect on the film, that is, it feels that the amount of light is larger. And the lighter film becomes darker after being processed in the dark room. Therefore, the defects in the work piece produce black shadows on the negative through the rays, which is the principle of radiographic inspection.