What Is The Welding Seam Flaw Detection And Working Principle ?

  • By:Iris Liang
  • Date:2021/11/01

Weld flaw detection is to detect cracks or defects in metal materials or components in the welding machine process. Commonly used flaw detection methods are: X-ray flaw detection, ultrasonic flaw detection, magnetic particle flaw detection, penetrant flaw detection, eddy current flaw detection, gamma ray flaw detection and other methods. Physical testing is to perform non-destructive testing without chemical changes.


Physical testing is to perform non-destructive testing without chemical changes. Portable ultrasonic weld defect detector, it can quickly, conveniently, without damage, and accurately detect, locate, evaluate and diagnose various defects (cracks, inclusions, pores, incomplete penetration, incomplete fusion, etc.) inside the workpiece.


It is used not only in the laboratory, but also in the engineering site inspection. It is widely used in welding seam inspection in the manufacture of boiler and pressure vessel, welding seam quality assessment in engineering machinery manufacturing, iron and steel metallurgy, steel structure manufacturing, shipbuilding, oil and gas equipment manufacturing and other fields that require defect detection and quality control.


For some precision stainless steel welded pipes used in specific fields, customers will require us to equip their ordered stainless steel industrial tube making machinery with non-destructive testing equipment. In order to meet the needs of customers, Hangao Tech (SEKO Machinery) will customize according to the scope of pipe manufacturing proposed by customers. The common ones are eddy current flaw detectors, but there are also customers who require ultrasonic flaw detectors or laser detection.

Flaw detection inspection scope :

1. Inspection of weld surface defects. Check the welding quality of weld surface cracks, lack of penetration and weld leakage.

2. Inner cavity inspection. Check surface cracks, peeling, pull lines, scratches, pits, bumps, spots, corrosion and other defects.

3. Status check. When certain products (such as worm gear pumps, engines, etc.) work, perform endoscopic inspections according to the items specified in the technical requirements.

4. Assembly inspection. When there are requirements and needs, use the Yatai Optoelectronics Industrial Video Endoscope to check the assembly quality; after the assembly or a certain process is completed, check whether the assembly position of each component meets the requirements of the drawing or technical conditions; whether there are assembly defects.

5. Surplus inspection. Check the residual internal crumbs and foreign objects in the inner cavity of the product.


Basic principles of ultrasonic flaw detection :

Ultrasonic flaw detection is a method that uses ultrasonic energy to penetrate deep into the metal material, and when one section enters another section, the characteristics of reflection at the edge of the interface are used to check the defects of the part. When the ultrasonic beam passes from the surface of the part to the probe Inside the metal, when it encounters a defect and the bottom surface of the part, a reflected wave is generated separately, forming a pulse waveform on the phosphor screen, and the position and size of the defect are judged based on these pulse waveforms.

Advantages and disadvantages :

Compared with X-ray flaw detection, ultrasonic flaw detection has the advantages of higher flaw detection sensitivity, short cycle, low cost, flexibility and convenience, high efficiency, and harmless to the human body.


The disadvantage is that it requires a smooth working surface and requires experienced inspectors to distinguish the types of defects, and there is no intuitiveness to defects; ultrasonic flaw detection is suitable for inspection of parts with a large thickness .




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