Basic knowledge of nondestructive testing four common methods for weld nondestructive testing

Date：2022-04-20 17:43:09Views：1147

Nondestructive testing is a test method to check the surface and internal quality of the inspected parts without damaging the working state of the workpiece or raw materials. Use the acoustic, optical, magnetic and electrical characteristics to detect whether there are defects or non-uniformity in the tested object, give the information such as the size, location, nature and quantity of defects, and then determine the general name of all technical means of the technical state of the tested object (such as qualified or not, remaining life, etc.). In order to help you have an in-depth understanding, this paper will summarize the relevant knowledge of weld nondestructive testing. If you are interested in what this article will cover, read on.

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

1、 Ultrasonic flaw detection

It is a nondestructive testing method to detect defects by using the reflection property of ultrasonic wave at the interface in the medium and the attenuation law when it propagates.

Scope of application:

1. Longitudinal wave can be used to detect inclusions, cracks, shrinkage, white spots, delamination and other defects in metal ingots, billets, medium and thick plates, large forgings and products with simple shape;

2. Transverse wave can be used to detect circumferential and axial cracks, scratches, pores, slag inclusion, cracks, incomplete penetration and other defects in the pipe;

3. Surface defects on castings with simple shape can be detected by surface wave;

4. Defects in thin plates can be detected by plate wave.

2、 Magnetic particle inspection

It is a nondestructive testing method that uses the interaction between magnetic leakage field and magnetic powder to show the surface and near surface defects of ferromagnetic materials.

Scope of application:

1. Detect the discontinuities on the surface and near surface of ferromagnetic materials that are very small and the gap is very narrow (for example, cracks with a length of 0.1mm and a width of micron can be detected), which are difficult to be seen visually;

2. It can detect raw materials, semi-finished products, finished products and parts in service, as well as plates, profiles, pipes, bars, weldments, steel castings and forged steel parts, and can find defects such as cracks, inclusions, hair lines, white spots, folding, cold insulation and looseness.

3、 Radiographic inspection

It is a nondestructive testing method to detect defects by using the different absorption of penetrating rays by the tested workpiece.

Radiography has been widely used in the internal quality inspection of welds and castings, such as welds of various pressure vessels, boilers, ship hulls, oil and gas pipelines, pressure castings in various cast steel valves, pump bodies, petroleum drilling, chemical and oil refining equipment, precision cast turbine blades, various aluminum magnesium alloy castings for aviation and automobile industries, etc.

4、 Penetrant flaw detection

It is a nondestructive testing method for detecting open defects on the surface of materials based on the principle of capillary action.

Scope of application:

1. Detect the surface opening defects of (steel, heat-resistant alloy, aluminum alloy, magnesium alloy, copper alloy) and non-metallic (ceramic, plastic) workpieces, such as cracks, porosity, pores, slag inclusion, cold insulation, folding and oxidation scars. These surface opening defects, especially subtle surface opening defects, are generally difficult to find by direct visual inspection.

2. It can detect magnetic materials, non-magnetic materials, ferrous metals, non-ferrous metals, non metals, weldments, castings, calendered parts, forgings, machined parts, etc.

In conclusion, ultrasonic and X-ray flaw detection are applicable to detect internal defects; Among them, ultrasonic is applicable to parts with regular shape and more than 5mm. X-ray cannot locate the buried depth of defects and has radiation. Magnetic particle and penetrant flaw detection are applicable to detect surface defects of parts; Among them, magnetic particle flaw detection is limited to the detection of magnetic materials, and penetrant flaw detection is limited to the detection of surface opening defects. Shenzhen Chuangxin Online Testing Technology Co., Ltd. is a well-known professional testing institution for electronic components in China, with 3 standardized laboratories covering an area of more than 1000 square meters. The scope of testing services covers: testing and verification of electronic components, identification of IC authenticity, product design, material selection, failure analysis, function testing, factory incoming material inspection, X-ray testing of components, tape braiding and other testing items.