As we have seen in previews website pages, defects in welds are inevitable. Nevertheless, the poor weld quality leads to collapse. Therefore, proper inspection and quality control of welded joints is essential. Some of the commonly employed methods are discussed here.
1. Magnetic particle method
When iron fillings spread over the welded joint is subjected to electric current, the forms patterns which can be utilised for interpret and locating surface cracks.
2. Dye penetration method
A dye is spread over the surface of weld in this method and then the surplus is removed. Then dye absorber is placed on the surface which oozes out the dye in the crack revealing the depth of surface cracks.
3. Ultrasonic method
Defects like flaws, blow holes, slag inclusion and porosity of the welds can be evaluated by this method. When ultrasonic waves are sent through the weld, these defects interfere with the wave propagation of the waves affecting its travel time. The defects can be interpreted by observing the travel time of the waves.
In this method, X-rays and gamma rays are used to locate the defects. This is used in groove welds only.