There are two most common non-destructive testing methods for resistance spot welding machines: the first is visual inspection, seal inspection and joint strength testing, etc.; the second is some physical inspection methods, i.e. X-ray inspection, ultrasonic inspection, eddy current inspection, thermal image method inspection, toner inspection, etc.
1. Visual inspection:
Defects in geometric shapes can be inspected by observation (allowing the use of a magnifying glass of no more than 20 times) and actual measurement methods, and can be observed in external cracks, surface burns, burn-throughs, spattering, edge swelling and other defects.
2. Seal inspection:
Pneumatic method (0.1-0.2mpa) pillow-shaped test pieces or the structure itself in water, but also can be used hydraulic method. Helium mass spectrometry and halogen leak reduction method, mainly for gas-tight，oil-tight and water-tight seam welding.
3. Joint strength inspection under the application of prescribed loads:
For example, after flash butt welding automobile rims, it is necessary to use expansion machine for flaring test. This inspection method is determined according to the product requirements, production characteristics and conditions. For example, after flash butt welding automobile rims, it is necessary to use expansion machine for flaring test, so as to test the quality of the joint.
4. X-ray inspection:
When X-ray fluoroscopy is performed, shrinkage holes, porosity, cracks and spatter in the plate seam inside the joint can be detected. Also, molten core size and imperfections in the weld penetration can be detected in welded joints with area deviations.