Text 21181, 88 rader
Skriven 2006-01-06 11:53:01 av Michiel van der Vlist (2:280/5555)
  Kommentar till text 21046 av Roy Witt (1:1/22)
Ärende: WTC fire         (was; La
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 MvdV>> Have you ever done any brazing or welding yourself?

 > Many times. I used to own a Miller 150 amp TIG welder. Sold it
 > when I sold my shop. I also used the MIG welders that my welders
 > used in that shop, although they owned them. After retiring in
 > 1998, up until I moved from CA to TX, I owned an Oxy/Acetaline
 > torch. I've done plenty of silver soldering and brazing with
 > that torch, not to mention a lot of heat treating of tools.
 > I still have the mixer and tips, planning on buying a
 > new set of regulators and tanks one of these days. However, a
 > MIG welder has priority for now.

Very nice.

I notice that this time you did not revert to a personal attack. Thet tells
me... no I won't give that away just yet. <evil grin>

 MvdV>> The normal brazing procees is very much like welding by wire feed.

 > No it isn't. You have to apply lots of heat to the material to
 > be joined first, then you can do the brazing. A wire feed doesn't
 > need the heat of the torch, as it's provided by the electric arc.

Language issue here. I thought hat by "wire welding" you meant welding with a
torch.

 MvdV>> You use a bronze wire instead of a steel wire. For the rest it is
 MvdV>> pretty much the same. The temperature is a lower of course.

 > Actually, in brazing, the tempurature is much higher than in
 > electric arc welding. For instance, you have to heat the materials
 > to be welded to a critical stage before you can expect any filler
 > penetration. If you don't get any penetration, the weld is weak.

In welding, you have to heat the material above the melting point of whatever
you weld. In brazing you do not want the base matrial to melt.

 > Whereas, in electric arc welding, the depth of penetration is
 > deeper and the only heat required is at the spot of the weld.

I see what you mean now. With arc welding the temperature is highe, but only a
small spot at the time is that hot. Yes, you may be right that the overall heat
rquired is less with arc welding. Depending on the size of the object, etc etc.


 MvdV>> That tells me you never did any welding or brazing yourself.

 > That tells me that you've never run into any exotic materials
 > that are impossible to weld. For instance, tell me how to weld
 > or braze together a car part or a toy made of pot metal.

Sorry, my language fails me. What is "pot metal"?

 > One degree too hot and you'll melt the entire piece. How do you
 > tell when the tempurature is correct, when the metal shows no
 > sign of being heated? It can be done, but there's a
 > trick to it that only an experienced welder would know.

I never claimed to be an experienced welder. In fact I am a lousy welder.You
may remember me and Jack Yates discussing welding and me admitting to it. I am
good at soldering though..

 MvdV>> Penetration has nothing to do with strength. In fact deep
 MvdV>> pentration may *weaken* the joint.

 > Wrong, to a certain degree. All welding is penetration. Even
 > when you're brazing, there is a minut penetration of the brazing
 > rod into the parent material

Only a few molecules deep...

 > (that's why you use a flux, heat the material and melt the rod).

The flux is to clean the surface and screen the material from the atmosphere so
that it does not oxidize.

 > Otherwise, there would be no weld. And you're right about too
 > deep penetration; that would occur if your weld burns holes
 > through joint.

Which is why I am a lousy welder. I don't know how to properly regulate it.
Especially with thin stuf, I often burn through it.


Cheers, Michiel

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