Five detection methods for square tube surface defects

There are mainly five methods for detecting surface defects of square tubes (SHS):

1. Eddy current testing

There are various methods of eddy current testing, including conventional testing, far-field testing, multi-frequency testing, and pulsed testing. Eddy current sensors are utilised to detect metal. The differing forms and shapes of defects on the surface of square tubes will produce varying types of signal.

The test boasts the advantages of high detection accuracy, exceptional detection sensitivity, and swift detection speed. The device enables detection of the surface and sub-surface of the pipe under inspection, remaining unaffected by impurities like oil stains present on the surface of the square pipe being examined. However, it tends to classify non-defective sections as defects, yielding a high false detection rate, with the added challenge of adjusting the detection resolution.

 2. Ultrasonic testing

When ultrasonic waves are used to penetrate an object and encounter flaws, a portion of the sound waves is reflected. The reflected waves can be analyzed by the transmitter and receiver to detect defects. Ultrasonic testing is commonly employed for inspecting forged parts, providing high sensitivity to flaw detection. However, it can be challenging to inspect pipes with complex shapes. The surface of the square pipe must possess a certain level of smoothness for inspection, while the probe and surface gap must be filled with a coupling agent.

3. Magnetic particle detection

The process of magnetic particle detection involves creating a magnetic field within square-tubed material. The interaction between the leakage magnetic field at the defect and the magnetic powder causes local distortion of the magnetic field lines at surface and near-surface defects. Magnetic poles are then produced. The method offers numerous advantages, including low equipment investment, high reliability and intuitive operation. The drawbacks include steep operating expenses, inadequate defect classification, and slow detection speed.

4.Infrared detection

An induced current is created on the surface of the square tube via the high-frequency induction coil. This will result in increased power consumption and a rise in local temperature in the defective area. Infrared rays are used to detect the local temperature, which is used to determine the depth of the defect. Infrared detection is typically employed for defect detection on flat surfaces and is unsuitable for detecting metals with uneven surfaces.

5. Magnetic flux leakage detection

The magnetic flux leakage testing method for square tubes is akin to magnetic particle testing. However, it boasts greater scope of application, sensitivity and reliability than its counterpart.