How to determine if a weld is satisfactory?

Determining whether a weld is acceptable hinges on these four steps: visual inspection, non-destructive testing, mechanical property testing, and metallographic analysis. Let me break down the specific methods for you:

I. Visual Inspection
Weld bead formation: Check for uniform height and width using the naked eye or a magnifying glass.
Surface defects: Focus on checking for cracks, undercut, and porosity.
Dimensional measurement: Measure the weld reinforcement and width using a template or measuring ruler.
II. Internal Defect Detection
Radiographic testing (RT): Suitable for thin welds (<30mm), used to detect porosity and slag inclusions.
Ultrasonic testing (UT): Use a probe to detect lack of fusion and cracks.
Penetrant testing (PT): Fluorescent or dye penetrant testing, suitable for materials with smooth surfaces.
III. Mechanical Property Testing
Tensile test: Measures strength.
Bending test: Measures plasticity.
Impact test: Measures toughness.
IV. Microscopic Metallographic Analysis

Cut a sample and observe it under a microscope to check for overheating structures, slag inclusions, etc.

V. Special Scenarios
Electric resistance welding: Check if the resistance wire is extruded and observe whether there is molten material overflowing from the observation hole.
Leak testing: Water pressure test, air pressure test, or kerosene test.