What is the difference between welding, brazing, and soldering?

The fundamental difference between welding and brazing/soldering is the melting temperature:

Welding:

• The base metal melts — there is local fusion of the assembled pieces
• Temperature: 1,500°C (steel) to 660°C (aluminum)
• High mechanical strength: the joint can reach the strength of the base metal
• Significant thermal expansion, possible distortion
• Requires a certified welder for structural applications

Brazing:

• Only the filler metal melts (above 450°C — this is the very definition of brazing, AWS A3.0); the base metal does not melt
• The joint's mechanical strength is lower than that of the base metal and depends on the filler alloy, the gap between the parts and wettability
• Minimal distortion — ideal for precision assemblies
• Used in plumbing (copper), refrigeration, and electronics

Soldering:

• Temperature below 450°C (definition of soldering, AWS A3.0)
• Used in plumbing (copper pipes with solder) and electronics
• Limited mechanical strength

In Quebec: the acronym QBQ is the label of the preparation offered by Metierium — no official source names a body with that acronym. Welding qualification falls under the real framework: CCQ (certificate issued under the Act respecting pressure vessels, or a CWB certificate), Emploi-Québec for personal qualification, RBQ and ASME IX for company qualification. Brazing in plumbing falls under the CMMTQ: plumbers use a copper-phosphorus alloy for copper piping, with an oxyacetylene or propane torch.