5.5 SOLDERING AND BRAZING
• Basically, soldering and brazing involve melting a filler material that will flow into a narrow gap and solidify. It is distinct because the base materials should not be melted.
• The main difference is,
- Soldering is done at a lower temperature, either with a propane torch, or an electric heater. It is intended for bonds with less required strength, such as electrical and plumbing applications.
- Brazing is done at higher temperatures with oxyacetylene or mapp gas torches. These bonds tend to be higher and can be used for mechanical strength.
• General process considerations include,
- Suitable for gaps from 0.001” to 0.01”
- Surfaces must be sanded and cleaned before these processes are used.
- Flux is often used to deoxidize a surface so that the filler will adhere better. Typical fluxes include,
Brazing flux - fused borax or alcohol and borax paste
Soldering flux - inorganic salts (zinc ammonium chloride), muriatic acid, resin based
- Some fluxes are corrosive and should be removed after use.
• Materials include,
- Solder is often an alloy combination of two of tin, lead, silver, zinc, antimony or bismuth.
- Brazing metals are typically alloys such as,
brazing brass (60% Cu, 40%Zn)
silver alloys (with/without phosphorous)
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