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Re: [PSUBS-MAILIST] Re: Pressure vessel welding
Thanks for that Frank. What about 1/4inch rod? Is it logical to think
that 1/4 rod would produce results twice as fast as 1/8 rod (assuming
all other things equal), or does it just not work like that? I'm sure
1/4 rod requires more amperage to cause an arc which is one drawback,
but if you have the power available, does 1/4 rod make for faster work?
Also, I hate to sound dumb, but somebody has to take that role so it
might as well be me. Can someone explain "backgrinding" and why it is
necessary? Let's say I've got the rolled cylinder for my main hull.
There's an open seam running longitudinally which essentially is a
"butt" joint, correct? So I put down a root pass which I hope is going
to fill the void between the two sides of the seam at least on the inner
side of the cylinder. I likely won't fill the entire seam on the
outside of the cylinder depending on the thickness of the material (if
it's 1/6 thickness I will, but if its 3/4 thickness I won't). So let's
assume I'm working with 1/2 inch material and need multiple passes
because I'm using 1/8 rod. What am I backgrinding on the root pass?
The inner side, or the outer side? And assuming my root pass is
perfect, is "backgrinding" necessary on the build-up passes that go over
the root pass?
I'm going to take a welding course, but these questions have bugged me
for some time and I can't wait for the class. :)
Jon
ShellyDalg@aol.com wrote:
Miller makes good machines but definitely you want a DC machine. AC
"buzz boxes" are OK for some small farm quality welding, but not much
use beyond that. ( like fences or gates.)
A good DC machine ( and they also have an AC switch on them) can be
used for TIG as well. A cheap TIG torch runs about $80 and a flow
meter about $75. Those two items with a bottle of argon mix and you're
all set to TIG just about anything. As for magnetizing the metal,
that's not a problem. A 250 amp machine is enough for what we're
doing. The "duty cycle" relates to how long you can burn rod at the
maximum setting, based on a 10 minute cycle. 50% duty cycle means you
can burn rod on maximum for 5 minutes, then let the machine cool down.
It's pretty hard to "smoke" a stick weld machine. The older or better
machines have copper windings on the transformer, the newer or cheaper
machines have aluminum wire on the transformer. Get a copper wound one
if you can. You won't be welding at max power anyway. 3/32 and 1/8
size rod is the most common. Typically running at 90 to 125 amps.
Make sure you keep the rod DRY or use new rod. I buy my welding rod
in small batches ( 5 pound box ) so it's always new. Frank D..
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