Brazing and Welding Fillers

Descriptions, composition in mass percent, application examples and properties of welding fillers and hard solders.

Brazing
Brazing is different from welding in that it uses filler (solder) that has a lower melting point than the basic materials; therefore the basic materials are not melted. As a result, basic materials and solder may have different compositions.

The characteristic properties of the solders are their melting ranges as well as their operating temperatures. Above liquidus temperature there is only melted mass, below solidus there is no liquid mass. Operating temperature is the lowest surface temperature at the soldering point where the solder is wetted or forms a fusible phase by means of interfacial diffusion.
The operating temperature may be in the melting range of the solder. Liquidity temperatures of hard solders are above 450°C. For fusion brazing, the surfaces to be joined are at a constant distance of ) 0.23 mm. For braze welding, the distance of the surfaces to be joined is 0.50 mm.

Welding
Large-surface or local melting of basic material and weld material. Joint-welding (fusion welding), most of the time with similar weld materials with identical or almost identical melting range.
Build-up welding (weld-cladding) e.g. for corrosionresistant surfaces with similar or different weld materials. In literature, fillet brazing of e.g. CuSi3Mn1 on ferritic-pearlitic steels in automobile construction are often erroneously referred to as build-up welding.

Common procedures for copper-based alloys are: MIG (metal inert gas), TIG (tungsten inert gas) and less commonly manual arc welding. Rarely, gas welding (acetylene welding) is used.