On 3/23/2011 1:11 PM, Al Kozakiewicz wrote:
> Braising is a way of slow cooking meat! I'll bet that translated into French
> wonderfully!
>
> Brazing is a method for joining metals. Technically, it's more like
> soldering than welding, as the base metal is not melted.
You hope<:-))
Brazing is a sort of in between soldering and welding process with the
silver usually called "Silver Soldering". Silver Soldering is much
stronger and more durable than the soft soldering, but much easier than
brazing as it's done at a lower temperature. Silver alloys are available
with a wide range of melting points with the higher ones requiring a
torch instead of a soldering gun. It's also much more expensive than
soft soldering or Brazing. At least I've not seen any inexpensive
silver solders.
Brazing copper is most often done with a brass rod covered with a flux
and done at a temperature very close to the melting point of copper,
hence my "you hope" comment. I not only use a flux coated rod, but
prefer to have a can of flux at hand in which I can dip the exposed end
of the rod as the coating melts back. IOW, use lots of flux. Tip sizes
vary with the size of the work piece, but copper being a good heat
conductor can be challenging. I prefer a tip size larger than I'd use
for welding, but a much softer flame as this approach is less likely to
burn a hole in the copper. Heat the large area first, then add the wire
quickly followed by the brazing rod. I prefer to "tin" both pieces if
possible, then join them with a bit of additional brazing rod.
Like most things it takes a bit of practice and having some one show you
how can be a big help.
I use an OxyAcetylene set up for brazing rather than MapGas. It's easier
and besides I already have the torch. OTOH for some one who hasn't done
it the MapGas might be safer for the copper. LP gas will not get hot
enough, while MapGas is just sufficient meaning you will probably use a
lot of it, but run less risk of melting your work. You will heat the
copper to a point where the surface will rapidly oxidize and you can
watch the colors play around the surface. Once the copper becomes "red"
you are very close to the point where it melts and just about right for
the brazing rod to melt onto the hot copper.
The "ticklish" part of brazing is joining a relatively small wire to a
large surface without melting something other than the brazing rod.
A note: Freshly brazed copper looks like crap with all the oxide and
flux on it and needs to be washed to get rid of the flux. IF you want it
to look like copper again yo almost need to etch it and that then
requires a wash and neutralization although a thorough wash would
probably be sufficient but risky is using stranded wire. It may not be
pretty but it works well and is durable.
73
Roger (K8RI)
> Al
> AB2ZY
>
> ________________________________________
> From: towertalk-bounces@contesting.com [towertalk-bounces@contesting.com] On
> Behalf Of Rob Atkinson [ranchorobbo@gmail.com]
> Sent: Wednesday, March 23, 2011 12:51 PM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Soldering Radials?
>
> Hi Deni,
>
> The best way to bond your copper wire radials to a copper radial ring
> is by a method called braising. It is similar to welding and is done
> with a silver braising rod and MAPP gas torch at a high temperature.
> You have to learn how to do it and acquire the necessary tools and
> material. Braising is the method employed by professionals who
> rebuild ground systems for broadcast towers. It results in a bond
> that lasts indefinitely and can withstand the heat of a lightning
> strike. The copper will readily take the silver but should be
> temporarily elevated or somehow removed from any combustible material
> such as dry grass. If you simply solder the wires you will have a
> hard time heating the mass of copper without a torch and even if
> successful, a soldered connection will work for a time but not profide
> a long lasting low resistance connection. I am not sure how braising
> translates so to try to make my point I provide a French attempt
> below.
>
>
> 73
>
> Rob
> K5UJ
>
>
> Salut Deni,
>
> La meilleure façon de lier votre radiales fil de cuivre à un anneau de
> cuivre radiale est par une méthode appelée braiser. Il est semblable à
> la soudure et se fait avec une tige de braisage d'argent et la torche
> de gaz MAPP à une température élevée. Vous devez apprendre comment le
> faire et d'acquérir les outils et le matériel nécessaires. Le braisage
> est la méthode employée par les professionnels qui la reconstruction
> des systèmes au sol pour les tours de diffusion. Il en résulte une
> liaison qui dure indéfiniment et ne peut résister à la chaleur d'un
> coup de foudre. Le cuivre reprendra facilement de l'argent, mais doit
> être temporairement élevées ou en quelque sorte retirés de tout
> matériau combustible, comme l'herbe sèche. Si il vous suffit de souder
> les fils, vous aurez du mal à chauffer la masse de cuivre sans torche
> et même en cas de succès, une connexion soudée à travailler une fois,
> mais pas profide une longue durée de connexion de faible résistance.
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