Earl Brunner on sun 19 sep 04
Humm, I don't know about this, the welding class I took at Utah State, was
primarily for structural aircraft welds. The class was almost ALL gas
welding. All of our welds were tested by pulling the connected steel apart
after welding. You failed the test if the steel came apart at the weld. It
had to fail somewhere else on the steel.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Vince Pitelka
Sent: Sunday, September 19, 2004 3:38 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Types of welding - uses (Was: Welding and welding equipment)
Ken -
As I have always understood it (perhaps erroniously!), the problem with
structural integrity in gas welds is the amount of oxidation that occurs,
because the metal stays hot for so long. With an arc welder, the heating is
instantaneous, and the weld immediatley starts to cool. I'd be interested
in what your brother has to say about that. I am certainly not questioning
your brother's expertise. I am ready and willing to learn a lot more about
all of this. I find it fascinating.
Best wishes -
- Vince
logan johnson on sun 19 sep 04
[longish]
Interesting comments on welding. As Vince notes stick arc welding is the most common form of structural welding for thick steel work such as boiler making and ship building. It is messy but does lend itself to multiple passes for filling large pieces.
I recommend gas welding first because it teaches the basis for most forms of welding. Gas welding is limited primarily to mild steel with a 1/4" to 3/8" maximum thickness (bigger tips allow more heat for thicker pieces). Few applications require the ability to weld more than 1/4" thick pieces. The oxy-acetylene welding outfit can also be used for cutting, brazing, soldering, heating of metal for annealing, forming and heat treating. In some applications it is the very best form of welding where the weld must be annealed after welding because you can "torch" the weld right after the weld process is complete. If you can gas weld you can do almost anything with mild steel.
TIG (tungsten inert gas) or Heliarc (the original patent name for the process) is similar to gas welding as has been noted but the equipment is expensive running in the thousands of dollars and generally requiring 220 three-phase power. But TIG can be used for all sorts of metals. Stainless steel, titanium, aluminum and even copper can be welded using TIG. It was mentioned as being slow but it really isn't. TIG, to me, gives the best looking of all welds when properly done although good gas welding beads look very similar. TIG welding is almost identical to gas welding and a good gas welder can adapt to TIG in a matter of minutes.
MIG (mechanical inert gas) welding or wire welding is the quickest of all welding processes and perhaps needs the least amount of skill. Once the power and wire speed are set for a certain thickness it takes little skill to weld. Drop the hood and pull the trigger is about all that there is to it. MIG primarily used for mild steel, stainless steel, and aluminum. The weld is acceptible looking when done right but does not match the beauty of TIG or gas welding. MIG outfits run a few hundred dollars and up so they are reasonable to purchase and run on 110v.
So I would still recommend that gas welding is the best thing to learn first and the first outfit a person should buy. It is the cheapest form of welding and the outfit does so much more. I MIG weld most things but could not live without my oxy-acetylene outfit.
Arc is okay but it is dirty (lots of "splatter" to clean up after the weld) but admittedly is the best form of welding if you want to build a battleship. It's realitively cheap with the outfit running only a couple hundred dollars.
Just remember that penetration with a good fill of the weld is the most importanty part of welding, that welded joint is weakest next to the weld, and when you weld something it will shrinks slighty (about .030" per weld for TIG or MIG welding) when the piece cools.
Happy welding one and all.
Logan's Hubby
Logan Johnson Audeo Studios
www.audeostudios.com
"Carpe Argillam!!"
Vince Pitelka on sun 19 sep 04
Ken -
Thanks for the up date on the latest welding techniques. That is indeed
fascinating, especially the part about gas welding a branch on a
high-pressure natural gas line while it is still under pressure! Man, those
guys really do need to know what they are doing!
I am going to ammend my former post and say that anyone wanting to do very
strong structural welds with the most affordable equipment and the most
easily-accessible skills can do so with an old-fashioned arc welder. You
can buy a very good 225-amp AC buzz-box arc welder for $200, and with some
serious lessons from a good welder, you can do very strong structural
welding on anything up to and including 1/2" plate. Your brother has long
experience and access to the best and latest welding equipment, but I expect
that he would agree with the above.
As I have always understood it (perhaps erroniously!), the problem with
structural integrity in gas welds is the amount of oxidation that occurs,
because the metal stays hot for so long. With an arc welder, the heating is
instantaneous, and the weld immediatley starts to cool. I'd be interested
in what your brother has to say about that. I am certainly not questioning
your brother's expertise. I am ready and willing to learn a lot more about
all of this. I find it fascinating.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Ivor and Olive Lewis on tue 21 sep 04
Dear Earl and others interested in this thread,
Some interesting points being brought up.
<immediately starts to cool>> Yes, But Arc Temperature is of the order
of 5000=BA C which is why there are lots of fumes from vapourised metal
and flux. The temperature of the Oxy-acetylene flame is ~ 2000=BA C at
the tip of the inner cone.
<oxidation that occurs, because the metal stays hot for so long.>>
Structural integrity is based on many factors. It would be rare for
oxidation to be one of them if air is being excluded from the molten
pool of metal. Preventing Oxidation is part of the technique which
must be learned under supervision of a qualified teacher whenever
possible. There is also a need to get parts and the weld which unites
them to cool slowly so that some degree of stress relief takes place,
otherwise you can get an embrittled joint which will fail in service.
Welding, like Pottery is both Craft and Trade, has its Technologies
and Sciences, has its Professional Associations, has its Literature
and its Historic Archives.
Those who choose to buy welding kits from XXXXMART and similar retail
outlets might bear this in mind and do a little study before they
launch themselves into the task at hand, whatever that might be.
People run into problems. There are many causes. In comparison
Ceramics and Pottery seem like child's play.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
.
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