Ultrasonic weld inspection methods
views：117
author：admin
source：Hiwave
time：2025-01-17
catogory：Industry News
What is a welding defect?
A welding defect refers to the incompleteness of a welded joint. The main types include weld……
What is a welding defect?
A welding defect refers to the incompleteness of a welded joint. The main types include welding cracks, incomplete fusion, slag inclusion, porosity, and surface appearance defects. These defects reduce the cross-sectional area of the weld, lower its bearing capacity, create stress concentration, lead to cracking, reduce fatigue strength, and make the welded component prone to fracture. The most harmful defects are welding cracks and porosity.
Classification of welding defects
Welding defects during the process can be diverse. They can be classified into two categories based on the location and manifestation: external defects and internal defects.
External defects: surface cracks, surface porosity, joint deformation, etc.
Internal defects: internal porosity, cracks, incomplete fusion, slag inclusion, etc.
Methods for detecting welding defects
Penetrant Testing
Application: Mainly used to detect surface-breaking defects such as cracks, porosity, cold laps, and other surface defects.
Principle: A penetrant liquid is applied to the surface of the workpiece, allowing it to seep into surface-breaking defects. After some time, excess penetrant is washed off, and a developer is applied to reveal the penetrant trapped in the defects.
Magnetic Particle Testing
Application: Primarily used for detecting surface and near-surface defects in ferromagnetic materials, such as cracks, slag inclusions, folding, etc.
Principle: A magnetic field is created around the workpiece. If defects are present, a magnetic flux leakage occurs at these points. Magnetic particles are then applied, and they accumulate at the defect locations, revealing the defect’s position and shape.
Radiographic Testing
Application: Suitable for detecting internal defects in various materials, especially effective for wall structures and welds, and can clearly show the internal shape, position, and size.
Principle: X-rays and γ-rays penetrate the sample, and the image is captured on film or other imaging devices. Since different materials absorb X-rays at different rates, the internal defects can be revealed through the varying absorption rates, visible on the radiographic film.
Each NDT (Non-Destructive Testing) method has its unique advantages and application areas. The choice of method should consider multiple factors for the most effective defect detection.
