Welding, Brazing and Joining Techniques
Welding, Brazing and Joining Techniques
This domain tests selection and control of joining methods: MIG/MAG, TIG, spot, oxy-acetylene, brazing, adhesive bonding and riveting.
Core rules
- MIG/MAG (GMAW) is the common body-shop process for steel: DC electrode positive, wire speed and current set to suit sheet thickness, and 75% argon/25% CO2 or CO2 gas.
- TIG (GTAW) suits aluminium and thin steel; use AC for aluminium and the correct filler.
- Spot welding reproduces factory joints; plug welds through a drilled hole replace spot welds where access is limited.
- Brazing uses a brass filler at lower temperature than welding; it does not melt the base metal but is not a substitute for structural welds unless specified.
- Adhesive bonding and riveting are used on aluminium and mixed-material bodies.
- Clean bare metal, tight fit-up and correct gas flow prevent porosity and weak joints.
Worked example
A replacement sill section needs joining at a factory spot-weld location. Reasoning: drill 8 mm plug-weld holes in the new panel, clamp it tightly, and plug weld to the inner panel. The weld must penetrate both layers without burning through. A continuous seam weld would distort the panel; the plug weld mimics the original spot weld.
Traps
Welding galvanised steel without stripping and ventilating, using the wrong wire on aluminium, and brazing a high-strength steel section. Also, leaving porosity from low gas flow or a dirty surface.