The surface defects of square tubes will greatly reduce the appearance and quality of products. How to detect the surface defects of square tubes? Next, we will explain the surface defect detection method of the lower square tube in detail
1、 Eddy current testing.
Eddy current testing includes conventional eddy current testing, far-field eddy current testing, multi frequency eddy current testing and pulse eddy current testing. Using eddy current sensors to sense metal, different types of signals will be generated according to the types and shapes of surface defects of square tubes. It has the advantages of high detection accuracy, high detection sensitivity and fast detection speed. It can detect the surface and lower surface of the tested pipe without being affected by the impurities such as oil stain on the surface of the tested square pipe. The disadvantages are that it is easy to judge the defect free structure as a defect, the false detection rate is high, and the detection resolution is not easy to adjust.
2.Ultrasonic testing
When the ultrasonic wave enters the object and meets the defect, part of the acoustic wave will be reflected. The transceiver can analyze reflected waves and detect defects abnormally and accurately. Ultrasonic testing is often used to test forgings. The detection sensitivity is high, but the pipeline with complex shape is not easy to detect. It is required that the surface of the inspected square tube has certain smoothness, and the gap between the probe and the inspected surface shall be filled with coupling agent.
3.Magnetic particle testing
The principle of magnetic particle method is to realize magnetic field in square tube material. According to the interaction between defect leakage magnetic field and magnetic particle, when there are discontinuities or defects on the surface or near the surface, the magnetic field lines will be locally deformed at the discontinuities or defects, and magnetic poles will be generated. Its advantages are less equipment investment, high reliability and strong visualization. The disadvantages are high operation cost, inaccurate defect classification and slow detection speed.
4.infrared acquisition
The induction current is generated on the surface of the square tube through the high-frequency induction coil. The induced current will cause the defect area to consume more electric energy, resulting in local temperature rise. Use infrared to detect local temperature and determine defect depth. Infrared detection is generally used for the detection of flattened surface defects, but not for the detection of surface irregularities.
5.Magnetic flux leakage test
The magnetic flux leakage testing method for square tubes is very similar to the magnetic particle testing method, and its applicable range, sensitivity and reliability are stronger than the magnetic particle testing method.
Post time: Aug-12-2022
