Brazing & Soldering
Brazing and Soldering are joining processes that use a combination of heat, filler metal, and typically a flux to join many similar and dissimilar materials.
The essential difference between brazing and soldering is the melting temperature of the filler metal.
In Brazing filler metals melt above 450°C while in soldering filler metals melt below that temperature.
In all cases filler metal melting temperatures are below the melting
temperatures of the workpieces being joined.
Joining is accomplished by the flow of filler metal between closely fitted joints ranging from 0.025 to 0.13 of a mm in brazing and 0.08 to 0.15 of a mm in soldering.
The result is a joining of the parts by capillary action as the liquid filler metal exhibits a stronger attraction to the base materials than itself.
( Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.)
A common term for capillary action is “wetting.”
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To facilitate this wetting action a fluxing agent is commonly employed. The flux lowers the molten filler metal surface tension and prevents the formation of oxides between the joint surfaces and the filler metal.
However, flux residue is corrosive, requiring a separate post-joining cleaning operation.Soaking in hot water and/or wire brushing are common methods.
As a joining process brazing has certain advantages over mechanical fastening and welding.
These advantages include:
* The joining of dissimilar metals and materials
* Very thin material can be brazed which would otherwise be damaged by welding
* Inaccessible joints can more easily be brazed
* Brazing is easily and more economically automated than many welding processes
Soldering is one of the oldest methods of joining metals. Because filler metals melt at low temperatures there is minimum part distortion and heat damage to sensitive parts.
Many combinations of metal to metal, ceramic to metal, and glass to metal may be joined.
Soldering is used extensively in the electronics industry where it’s limited mechanical strength is not a major factor.
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Originally published at http://ashvinipawar.wordpress.com on January 3, 2017.
