How to check the welding quality of the butt welder?

1. Appearance inspection:
1. Direct observation: Observe the surface of the welded joint with the naked eye to see if there are obvious defects, such as cracks, pores, slag inclusions, undercuts, weld bumps, incomplete penetration, etc. For some smaller defects, you may need to use a magnifying glass (no more than 20 times) to assist in observation.
2. Dimension measurement: Use tools such as welding inspection rulers to measure whether the dimensions of the weld, weld bumps, depressions, misalignment, etc. meet the requirements. At the same time, check whether the weldment is deformed.
2. Destructive test:
1. Tear test: Tear, torsion, compression and other experiments are carried out on site to test the spot welding core diameter, seam welding weld width, joint destruction characteristics and the stability of welding specifications.
2. Low-power inspection: By making macro test pieces (less than 100 times), observe the incomplete penetration, overheating and oxide inclusion content of the butt welded joint.
3. Strength test: Including positive tension test, shear test, torsion test, bending test, fatigue test, etc., to evaluate the strength, plasticity and fracture characteristics of the joint.
4. Metallographic and chemical composition analysis: Use a metallographic microscope to observe internal cracks, shrinkage cavities, beard tissues where the weld line extends into the weld line, etc., and perform chemical composition analysis to detect weld zone tissue, loose shrinkage of welds, delamination and thermal cracks, burnout of alloy elements in joints, harmful inclusion content, etc.
3. Nondestructive testing:
1. X-ray inspection: It can detect defects such as shrinkage cavities, pores, cracks in the joints, and splashing (spot and seam welding) in the gaps between plates. At the same time, for welds with regional segregation, it can also detect the size of the nugget and the defect of incomplete penetration.
2. Ultrasonic flaw detection: It can determine the complete incomplete penetration (when there is a gap between parts), pores, shrinkage cavities and cracks, etc., but it is difficult to detect adhesion (incomplete penetration) because the thickness of the oxide film that forms adhesion is much smaller than the size that can be detected by ultrasonic flaw detection.
3. Eddy current flaw detection: By comparing the established relationship between the diameter of the nugget and the conductivity of the weld zone, the size of the nugget and the defect of incomplete penetration can be inspected.
4. Magnetic particle inspection: suitable for defect detection on the surface or near the surface of ferromagnetic materials. The weldment is magnetized in a strong magnetic field so that the magnetic lines of force pass through the weld. When encountering defects on the weld surface or near the surface, leakage magnetic field is generated to attract the magnetic iron oxide powder sprinkled on the weld surface. The position and size of the defect can be determined based on the traces of iron powder adsorption.
5. Penetrant testing: often used to check surface open defects. Spray a penetrant with fluorescent dye or red dye on the surface of the weldment to penetrate into the defect. Then wipe the surface of the weldment clean and apply a layer of white display liquid. The colorant that penetrates into the weldment defect is adsorbed by the white display agent due to capillary action, and the red trace of the defect appears on the surface.
4. Other detection methods:
1. Surface contact resistance measurement: used to evaluate the quality and conductivity of the weldment surface.
2. Joint air tightness test: detect the air tightness of the weld. For some weldments that require sealing, a certain pressure of gas or liquid can be filled into the weldment to check whether there is leakage.
3. Electron probe and electron microscope inspection: These methods can provide more microscopic structural and composition information for analyzing the organization and performance of welded joints.
4. Fracture analysis: Observe and analyze the fracture of welded joints to understand the cause and mechanism of fracture, which helps to evaluate welding quality.