Text 21046, 143 rader
Skriven 2006-01-04 15:59:08 av Roy Witt (1:1/22)
  Kommentar till text 20977 av Michiel van der Vlist (2:280/5555)
Ärende: WTC fire         (was; La
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04 Jan 06 12:57, Michiel van der Vlist wrote to Roy Witt:


 MvdV>>>>> there are other "solders" that result in a much stronger joint.
 MvdV>>>>> Some even stronger than welding. Popular along jewelers is a
 MvdV>>>>> mixture of silver, copper and zinc.
 >>>> Do any of you realize how tedius of a job it would be to solder
 >>>> those joints?
 MvdV>>> Not more tedious than welding or bolting.
 >> Very much so. The first thing that comes to mind would be the
 >> heat required to solder or braze those girders.

 MvdV> Ah, *brazing*, that was the word I was looking for. Over here we
 MvdV> call it "hard soldering", but I now realize "brazing" is the
 MvdV> correct English word.

Yeup.

 >> That would take more time than inserting a bolt and tightening
 >> down a nut and washer, ten times over.
 MvdV> Would it?

Yes. It takes a long time to get the material hot enough to liquify the
flux and melt the rod. That would make soldering and/or brazing too
costly.

 >> Welding by arc or wire feed would be the way to go if you're
 >> looking for speed.

 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.

 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.

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

 >> However, the need for the machines to do the welding
 >> would require more time wasted in getting them to the site.
 MvdV> Maybe. How about the machine to tighten the bolts?

An air hose attached to a centrally located compressor line will do to run
the 'air rachet'...fast and accurate. Two guys, one assembling the bolts,
washers and nuts to the girders, the other tightening them. One follows
the other.

 >>>> It's not like you're soldering a gold ring together. Not to
 >>>> mention that a 'soldered' girder joint wouldn't last 5 minutes
 >>>> in a building, even if it was possible to solder it.
 MvdV>>> If you can weld it, you can solder it.

 >> Wrong.

 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. 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.

 MvdV>>> And with the proper "solder" such a joint is just as strong
 MvdV>>> or even stronger than a welded joint.

 >> Wrong again. The key word here is penetration. Solder or even
 >> silver solder is not as strong a weld for the very fact that solder
 >> will not penetrate the parent material as deeply as an electric arc.

 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 (that's why you use a flux, heat the material and melt the rod).
Otherwise, there would be no weld. And you're right about too deep
penetration; that would occur if your weld burns holes through joint.

 MvdV>>> The main reason hard soldering is not used on a large scale is
 MvdV>>> cost. Welding is much cheaper.

 >> The main reason soldering isn't used on a large scale is
 >> because it's time consuming and has less strength than welding.

 MvdV> Not so. A good hard soldered joint is just as strong as a welded
 MvdV> joint.

Wrong again. Brazing can never be as strong as a weld (penetration again).

 MvdV> In fact making a good weld requires much more experience than
 MvdV> making a good solder or brazed joint.

Wrong again. When I started out, I learned how to use a stick welder
before I was allowed to use the torch. I found that they were all very
easy to master. I think I hated the TIG welding, because it used such
intense heat, that it scared me, but it too was mastered.

 MvdV> Use too much heat/current or stay on the same place too long and
 MvdV> you will burn a hole in whatever you try to join. With brazing or
 MvdV> soldering that does not happen so easily.

That is true, but only  in the sense that brazing doesn't penetrate as
deeply as an electric arc. Which is why the electric arc is preferable to
torch welding or brazing.

 >> Cost is a factor,

 MvdV> The main factor.

Not always. Preference comes into play when it's desirable to avoid using
an open flame or you need deeper penetration than brazing can provide.

 MvdV> Brazing is used extensively when cost is not an issue.

Which means that there is no brazing done, as material and labor cost is
too high for any kind of production welding. Brazing is ok for the
hobbyist or a quick fix when nothing else is available. But, when you
consider the costs of brazing, it's much cheaper to use electric arc
welding.


Roy
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