Ultrasonic inspection and closed pressure test of Die castings
Ultrasonic testing is a non-destructive testing method that quickly identifies internal defects in castings.
Ultrasonic waves are sound waves with a vibration frequency exceeding 2000 Hz. They have a very important characteristic, that is, when ultrasonic waves are transmitted from one medium to another, reflection phenomenon, especially reflection phenomenon, occurs. When ultrasonic waves are transmitted from air to metal or metal to air, almost 99% of the ultrasound waves will be reflected back from the interface. More than half of the defects such as pores and shrinkage holes in the casting are hollow, which means that the defective part has an air-metal interface, one side when the ultrasonic wave enters the reflected ultrasonic wave, and the other side has the defect, because there is no inconspicuous Under ultrasound, the projected area is similar to the "shadow" defect. Therefore, this phenomenon can be used to detect defects by measuring the ultrasonic waves reflected on the transmitting side (reflection method) or the ultrasonic attenuation on the opposite side (osmosis method).
Ultrasonic testing is widely used, high sensitivity, and harmless to the human body. However, since the requirements for castings have not been complicated, the surface is smooth and flat, and it is difficult to determine the type of defect and accurate measurement, it often depends on the experience and shortcomings of the inspectors. The popular method is to use ultrasonic testing to complete the casting. All parts of the inspection, re-occupy the radiological examination, and re-examine the suspect.
Sealing pressure test
The closed pressure test is a method for checking compactness.
The usual test method is to manufacture a test fixture based on the airtightness required for the casting (or the entire casting) of the part and the casting. After clamping the casting, the clamp is sealed and the air is filled with compressed air and immersed in the water tank. In general, when the compressed air is lower than two atmospheres, the soaking time is 1 to 2 minutes. At 4 atmospheres, the immersion time can be shortened without rigorous evaluation, but there are strict requirements in accordance with relevant regulations. The pressure in the closed pressure test typically exceeds 30-50 of the working pressure of the casting.
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