In article , drew j.
wrote:

hey guys!

i'm a novice tig welder, and have been having a lot of problems
welding mild steel. i took a class about 10 years ago, using an older
miller syncrowave, and tig was basically a snap then -- nice & slow,
clean & methodical. i've since bought a used miller econotig, and
while the unit seems to work ok, the welding is much more troublesome.
i'm generally practicing on anywhere from 1/16" to 3/16" steel plate
& angle, using argon at 20 cfm (or cfh -- i forget how it's
calibrated)

15-25 CFH is pretty standard for s standard collet body.
For a gas lens you can drop that to about 7-12 CFH.


and dc w/ electrode negative at around 80-100 amps,

1 amp per 0.001" of thickness for single pass welds in steel and
aluminum.



and
switching back & forth between 3/32" & 1/8" ceriated tungstens. i
started with thoriated, but got scared off by the radioactivity of the
thorium dust from grinding the tips (wasn't aware of it when i bought
my first tungstens).

Ceriated tungstens are fine as long as you don't push them too far.
Lanthanted is more forgiving.


i'm grinding the tungstens longitudinally to a
30 degree +/- point on an aluminum oxide wheel used only for
tungstens.


Sounds goo as long as your scratch lines are inline with the tungsten.


i'm also trying to get the base metal in the weld areas as
clean as reasonably possible.


Just make sure there is no oil, rust, paint or oxides.


i'm also preflowing the argon & using
the hi-freq-type start (i don't know if econotigs have true hi-freq or
some capacitor discharge starter).


Econotigs have a Capacitor Discharge High Freq.
However it operates just like a normal High Freq unit.


i have no idea what i'm doing wrong!! i'd appreciate it if any of you
could offer any advice with the following issues (or anything else
that seems relevant):

1. my tungstens get contaminated incredibly fast. i can weld for
maybe 2 to 4 linear inches & have it come out ok. then everything
gets screwed up. even when i don't mess up & touch the puddle or
filler rod, the electrode seems to get nasty-looking and
poorly-performing quickly. it's almost like the weld puddle spews a
spray of molten steel onto the tungsten. and sometimes the puddle
does spit. if i try to back off the foot pedal to lower the puddle
temp slightly so that the puddle doesn't spit, then the arc is less
stable. after things start going bad, often the arc starts wandering
& comes out the side of the electrode tip. i find that, if i crank
the amperage up, i can kinda "blow" the arc back out thru the
electrode tip -- forcing it, i guess, but it still performs poorly,
and everything, obviously, gets too hot. i'm ending up with welds
that have these porous spots that look kinda like the mineral pumice
(that light lava rock), although the voids tend to be angular-looking
& kinda follow the lines of the weld puddle ripples.


Either the machine is set for stick welding or something is very wrong
with your gas flow.
Maybe it is a bad bottle of gas.


2. i'm using copper-coated filler rod -- have some in 1/16" and some
in 3/32".
my welder will hardly even melt the thicker rod during the kind of
practice weld's i've been doing -- i either have to melt the rod off
with the arc directly, rather than melting it off while dipping into
the puddle (i know this is a no-no) or crank the amperage up so high
that i start melting thru the base metal. is it normal for 3/32" rod
to be too thick for the material/amperage i'm working with?


Never use a filler rod thicker than your base metal.




3. is it true that mill scale on rolled steel shapes will impede tig
welding?


Yes, all oxides must be removed.
The metal must be silver clean.


4. is one kind of tungsten better than another for mild steel?


Thoriated, Ceriated, and Lathanated will all work.



5. when you contaminate a tungsten, is it true that you have to break
off the
tip & grind a completely new point? a welding manual i read said to
do this, but a local welding supply place said no -- just grind off
the contamination & reshape the tip. i've tried it both ways, and the
break-off seems to maybe be better, but even so, it's always only a
short time before the problems mentioned in #1 above recur.


If you are doing aerospace work or nuclear reactor welding them notch
and break.
For most stuff just clean off the gunk on a belt sander.


6. i live in michigan -- pretty cold now (mid 20's-30's), and my
welding setup is in an unheated garage. i'd like to keep practicing
thru the cold weather, but will the steel act up when welded cold
(excessive thermal shock, cracking, etc.)? preheating may be
possible, but is kinda dificult for my arrangement. and i don't
understand how you could preheat stuff with an oxyacetylene torch &
then not have to clean up the base metal from the torch soot/oxidation
after preheating. while you're cleaning it up, it seems like you'd
lose your preheat.


Atmospheric temps won't make much difference for what you are doing.
On a much heavier weldment it could have drastic affects.



7. my interest in tig stems from my boyhood interest in bmx bikes.
the high-end frames have the most beautiful tig welds i've ever seen.
the thing i can't understand is how the welders get the ripples so far
apart. a lot of those welds have maybe 1/16" or even 1/8" between
ripples (on welds that are about 1/8" to 5/32" +/- wide. even when i
didn't have the troubles i'm having now, i've never been able to get
my beads to be so (for lack of a better way to describe it) laid-out &
leisurely-looking. mine tend to have the ripples a lot more
closely-spaced & busy-looking. does this nice kind of weld bead
result from some type of pulsed welding?


Pulsers make it a lot easier, but it can also be managed by when you
dip your filler rod.



8. are econotigs known to be troublesome machines? i don't know if
the problem's me or the welder.



I had one for 4 years.
It worked fine for me, but you might want to have yours checked out to
make sure the gas solenoid is firing correctly.

sorry for such a long message. thanks for any help you can offer.


That is what I am here for.
BTW the correct newsgroup for this question is

sci.engr.joining.welding