What is nondestructive testing (NDT)? What are the methods of welding nondestructive testing?

Date：2022-04-26 14:47:29Views：1342

Nondestructive testing is to detect the internal defects and surface defects of the workpiece without damaging the workpiece by using the changes of thermal, acoustic, optical, electrical, magnetic and other reactions caused by the abnormal internal structure of the material or the existence of defects.

Welding: usually refers to the welding of metal. It is a forming method in which two separate objects are combined into a body by heating or pressurizing, or both.

Classification: according to the heating degree and process characteristics of the welding process, the welding methods can be divided into three categories.

(1) Fusion welding

The welded part of the workpiece is locally heated to the molten state to form a molten pool (usually filled with filler metal), the weld is formed after cooling and crystallization, and the welded workpiece is combined into an integral whole. Common fusion welding methods include gas welding, arc welding, electroslag welding, plasma arc welding, electron beam welding, laser welding, etc.

(2) Pressure welding

In the welding process, whether heated or not, pressure welding method is required. Ordinary pressure welding includes resistance welding, friction welding, cold pressure welding, diffusion welding, explosive welding, etc.

(3) Brazing

After melting with solder (filler metal) whose melting point is lower than that of the welded metal, the gap is filled and diffused with the welded metal to realize the connection. In the brazing process, the welded workpiece will not melt and usually plastic deformation will not occur.

Characteristics of welding production:

1. Save metal materials and light structure.

2. The combination from small to large can manufacture heavy and complex mechanical parts, simplify casting, forging and cutting processes, and obtain the best technical and economic results.

3. The welded joint has good mechanical properties and air tightness.

4. Bimetallic structures can be manufactured, so that the properties of materials can be fully utilized.

Application: welding technology is widely used in machinery manufacturing, shipbuilding industry, construction engineering, power equipment production, aerospace and other industries.

Defect: the welded structure cannot be disassembled, which brings inconvenience to maintenance; Welding structure will produce welding stress and deformation; The structure and performance of welded joints are usually uneven, and welding defects will occur.

Testing methods: common NDT methods: ultrasonic testing (UT), magnetic particle testing (MT), liquid penetrant testing (PT) and X-ray testing (RT). There is no need to repeat here. Among them, X-ray detection technology is more recommended, which is also the development trend in the future. It is sensitive to the detection of volumetric defects, and it is easier to characterize the defects. It can visually display the shape and type of defects. The image processing technology is mature, the results can be saved and traced, and it can be supported online and offline.

The above is the relevant content of "welding nondestructive testing method" brought by this core test. I hope it can be helpful to you. We will bring more wonderful content in the later stage. The company's testing services cover: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, tape braiding and other testing items. Welcome to call Chuangxin testing. We will serve you wholeheartedly.