Welding, Brazing and Joining Processes
Welding, Brazing and Joining Processes
This domain tests process selection, setup, joint preparation and defect avoidance for collision repair. It includes MIG/MAG, TIG, squeeze-type resistance spot welding, brazing, soldering and structural adhesive bonding.
Core rules
- MIG/MAG is common for steel body panels; match wire type and diameter to base metal, set polarity correctly and use the recommended shielding gas.
- TIG suits aluminium and thin precision work but is slower and needs clean metal.
- Squeeze-type resistance spot welding reproduces factory joints; test on scrap and maintain electrode tips.
- Brazing and soldering join at lower temperatures than welding; they do not restore full base-metal strength and must not replace a structural weld.
- Structural adhesives distribute stress and seal joints; follow primer, open time and clamp time exactly.
- Prepare joints by removing coating, fitting closely and protecting bare metal. Do not weld galvanized steel without ventilation and coating removal.
Worked example
A replacement door skin is specified as a weld-bonded panel. Reasoning: apply the approved structural adhesive in the specified pattern, fit and clamp the skin, then make the required MIG stitch welds or spot welds. The adhesive adds stiffness and sealing, but the welds still carry the specified joint function. Skipping the adhesive or using brazing instead changes the repair method.
Traps
Welding over paint or galvanizing; wrong polarity; using brazing for a structural joint; no weld-through primer; poor fit-up causing burn-through.
Key points
Match MIG wire, gas and polarity to the base metal. Spot welding reproduces factory resistance welds. Brazing and soldering are lower-strength joining methods. Structural adhesives require exact primer, open and clamp times. Remove coatings and ventilate when welding galvanized steel.