Welding, Brazing, Soldering and Riveting for Sheet Metal
This domain covers the joining processes used alongside mechanical fastening. Expect questions on process selection, temperature ranges, fluxes, rivet size and distortion control.
Processes
- Shielded metal arc welding, gas metal arc welding, gas tungsten arc welding, resistance spot and seam welding, and oxy-acetylene welding are used on sheet. Clean the joint, set the current for thickness, and control distortion by balancing welds and using clamps.
- Brazing uses a filler that melts above 450°C but below the parent metal. Soldering uses filler below 450°C. Both rely on capillary action and a flux to remove oxide. Brazed and soldered joints are not fusion welds.
- Riveting uses a ductile rivet. Hole size is slightly larger than the rivet diameter; pitch and edge distance must be adequate. Buck the tail without crushing the sheet.
Worked example
Two 1.5 mm sheets are to be joined with 4 mm diameter rivets. Total thickness is 3 mm. A common rivet length rule is L = t + 1.5d = 3 + 1.5 × 4 = 9 mm. Select a 9 mm rivet, drill a hole slightly larger than 4 mm, insert the rivet, and form the tail. Reasoning: the shank must fill the hole and leave enough material to form the second head.
Traps that cost marks
Soldering without flux; confusing brazing and soldering temperature ranges; using an oversized rivet hole; and welding galvanised sheet without extracting the zinc fumes.