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•Basically, filler and base materials are heated to the point of melting by a burning a gas.

•Two common types are,

-oxygen-acetylene

-mapp gas

•These are suited to a few applications, but they produce by-products that can contaminate the final weld.

•Typically the flame is adjusted to give a clean burn, and this is applied to the point of the weld.

weld tip and gas orifice

hot point (inside blue flame)

•A welding rod will be fed in separately to melt and join the weld line.

•Flux can be used to clean the welds.

•Process variables include,

-gas and oxygen flow rates

-distance from surface

-speed

-material types

-surface preparation of materials

42.4 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,