[TowerTalk] Subject: Re: Cadwelding vs Silver Solder for Ground Radial, Systems

[Phil Camera]

As can be seen from the info below from Wikipedia and from Erico, 
CadWelds involved much higher temperatures and a totally different 
joining process than brazing or soldering.  This type of connection be 
design can withstand thermal cycling, repeated current carrying events, 
requires no maintenance, and can be direct buried.  This is why, in 
addition to mechanical connections (which are bad in the outdoors due to 
loosening from thermal cycling and maintenance of the interface), NEC 
only allows exothermic type of connections.  If your ground system gets 
whacked by lightning, you system may heat up and a brazed/soldered joint 
may melt and fail leaving you with less protection. My personal 
recommendation is to go with the CadWelds, they're very easy to use and 
maintenance free.  Going with any other method, you will be taking your 
chances; you've gone this far to properly protect your system, don't 
cheapen it at this stage.  Phil  KB9CRY

*
*

*Brazing* is a joining process whereby a non-ferrous 
<http://en.wikipedia.org/wiki/Ferrous> filler metal 
<http://en.wikipedia.org/wiki/Metal> and an alloy 
<http://en.wikipedia.org/wiki/Alloy> are heated to melting temperature 
(above 450°C <http://en.wikipedia.org/wiki/Celsius>; 800°F) and 
distributed between two or more close-fitting parts by capillary action 
<http://en.wikipedia.org/wiki/Capillary_action>. At its liquid 
temperature, the molten filler metal interacts with a thin layer of the 
base metal, cooling to form an exceptionally strong, sealed joint due to 
grain structure interaction. The brazed joint becomes a sandwich of 
different layers, each metallurgically 
<http://en.wikipedia.org/wiki/Metallurgy> linked to each other. Common 
brazements are about 1/3 as strong as the materials they join, because 
the metals partially dissolve each other at the interface, and usually 
the grain structure and joint alloy is uncontrolled. To create 
high-strength brazes, sometimes a brazement can be annealed 
<http://en.wikipedia.org/wiki/Annealing_%28metallurgy%29>, or cooled at 
a controlled rate, so that the joint's grain structure and alloying is 
controlled.

If silver alloy is used, brazing can be referred to as 'silver brazing'. 
Colloquially, the inaccurate terms "silver soldering" or "hard 
soldering" are used, to distinguish from the process of low temperature 
soldering that is done with solder having a melting point below 450 °C 
<http://en.wikipedia.org/wiki/Degree_Celsius> (800 °F 
<http://en.wikipedia.org/wiki/Degree_Fahrenheit>). Silver brazing is 
similar to soldering <http://en.wikipedia.org/wiki/Soldering> but higher 
temperatures are used and the filler metal has a significantly different 
composition and higher melting point than solder 
<http://en.wikipedia.org/wiki/Solder>. Likewise, silver brazing often 
requires the prior machining of parts to be joined to very close 
tolerances prior to joining them, to establish a joint gap distance of a 
few mils (thousandths of an inch) for proper capillary action during 
joining of parts, whereas soldering does not require gap distances that 
are anywhere near this small for successful joining of parts. Silver 
brazing works especially well for joining tubular thick-walled steel 
pipes, provided the proper machining is done prior to joining the steel 
parts.


*CadWeld*
The CadWeld exothermic welding process forms a molecular bond with 
current carrying capability equal to that of the conductor.  Grounding 
system incorporating this type of connection therefore operate as a 
continuous conductor with lower resistivity.  Starting and welding 
materials are exothermic mixtures and react to produce hot moltem 
materials with temperatures in excess of 2200 deg C (4000 deg F) and 
localized release of smoke.

   1. _APPLICATION_

 

The CADWELD^ exothermic welding system is used for in making electrical 
connections of copper to copper, copper to steel or copper to cast iron 
for grounding and cathodic applications.__

_ _

         1. CADWELD connections shall be suitable for exposure to the
            elements of direct burial in earth or concrete without
            degradation over the lifetime of the grounding system.

 

         2. EXOLON connections are metallurgically similar to CADWELD^
            connections but are designed primarily for indoor or
            confined spaces.  EXOLON shall use weld metal with no
            starting material.  EXOLON molds shall use a dual element
            filter system that removes 97% of the smoke.

 

   2. _MATERIAL_

 

CADWELD Molds shall be made from:__

_ _

         1. Graphite material capable of withstanding high temperatures
            that are capable of providing an average life of not less
            than fifty separate exothermic welds.__

_ _

         2. Cordierite, refractory ceramic or other material suitable
            for a single connection.__

 

Starting material (where used) shall consist of aluminum and copper and 
iron oxides.  It shall not contain phosphorous, magnesium or any 
caustic, toxic or explosive substances.

 

Low voltage battery starting (where used), shall use an electric 
ignition system that does not use starting material.

 

Weld metal used for grounding connections shall contain copper oxide, 
aluminum and not less than 3% tin as the wetting agent.  Weld metal used 
for cathodic connections shall not contain tin, but shall contain vanadium.

 




Roger D Johnson wrote:
> Phil Camera wrote:
>
> Can someone explain the difference between a CADWELDED joint and one
> that is properly brazed? The only difference I can see is the means
> of generating the heat.
>
> 73, Roger
>
>
>