Comparison of four Nondestructive testing methods for weld

Nondestructive testing (NDT) is the general term of all technical means to detect whether there are defects or non-uniformity in the inspected object, give the size, location, nature and quantity of defects, and then determine the technical status (such as qualified or not, residual life, etc.) of the inspected object by using the acoustic, optical, magnetic and electrical characteristics.

Common nondestructive testing methods: ultrasonic testing (UT), magnetic particle testing (MT), liquid penetrant testing (PT) and X-ray testing (RT).

Ultrasonic examination

Compared with X-ray flaw detection, ultrasonic flaw detection has the advantages of high sensitivity, short cycle, low cost, flexible and convenient, high efficiency and harmless to human body;

The disadvantages are that the working surface is required to be smooth, the experienced inspectors are required to identify the types of defects, and the defects are not intuitive; ultrasonic flaw detection is suitable for the inspection of parts with larger thickness.

Magnetic particle testing

1. Magnetic particle testing is suitable for detecting the discontinuities on the surface and near surface of ferromagnetic materials with very small size and extremely narrow gap.
2. Magnetic particle testing can be used to inspect parts and components under various conditions, as well as various types of parts.
3. Cracks, inclusions, hairlines, white spots, folding, cold shut and porosity can be found. (thanks for your attention to Dingding automatic welding)
4. Magnetic particle testing can not detect austenitic stainless steel materials and welds welded with austenitic stainless steel electrode, nor can it detect non-magnetic materials such as copper, aluminum, magnesium and titanium. It is difficult to find the delamination and folding with shallow scratch, deep hole and angle less than 20 ° with the workpiece surface.

Liquid penetrant testing

1. It can detect all kinds of materials;
2. It has high sensitivity;
3. It has the advantages of intuitive display, convenient operation and low detection cost.
4. It is not suitable for checking workpieces made of porous and loose materials and rough surfaces;
5. Penetrant testing can only detect the surface distribution of defects, so it is difficult to determine the actual depth of defects, so it is difficult to make quantitative evaluation of defects. The detection results are also greatly affected by the operator.

X-ray inspection

1. It is sensitive to the detection of volumetric defects, and it is easy to determine the nature of defects.
2. The X-ray film is easy to keep and has traceability.
3. Visually display the shape and type of defects.
4. The defects can not locate the buried depth of defects, at the same time, the detection thickness is limited, the negative film needs to be sent and washed specially, and it is harmful to human body, and the cost is high.

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