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I need to weld a frame for my solar catamaran project.
To weld now square 30x30 mm galvanized steel. Which one is better to use?
MIG or TIG welder,
I have only experience with MMA ( stick transformer welder) so this new inverter technology is quite new for me, but I just bought new 3 in one TIG, MIG and MMA inverter welder.
Which one give me better result taking into account my limited experience ?
Do you mean better as in strength?
Or easier to get an OK result for the DIY person (seems like that is what you really mean)???
DIY? Definitely MIG. TIG takes a lot lot longer to get good at even on a really good machine.
But a 3-in-1 will never be as good as a dedicated 1 in 1 so I suspect using TIG on a 3-in-1 is even harder.
If it is 30x30x1.6 or 2.0 galv steel, you could have done it with a $100 arc welder from K-mart given some practice.
MIG. It's way faster, far easier and you don't have a hope of welding Galv steel with TIG unless you grind away all of the gal from the weld area. Welding galv is an absolute pain, it's always easier if you grind the weld area back to raw steel, even with MIG. Watch the porosity.
And as I recall from my Navy days, you will get sick from the galvy fumes, we always drank milk before we welded it, not sure if that has any real validity or it's an old wives tale.
Funnily enough, I have just borrowed my brothers TIG which he has only had a short while himself. I have had a MIG for about 7 years.
TIG is slow, and for me trying to learn it, difficult. I can't see any advantage yet, other than using it on aluminium and once I get better at it, less weld build up.
MIG on the other hand is fast, repeatable, and with a well setup machine, easy.
For your requirement, MIG is definitely better.
use the stick welder. if you use mig you need to buy a roll of wire, buy gas and hire the bottle, and learn to use a new process.
if you already know how to stick weld just buy a box of gp rods and glue it up. you can then weld outside with no issues.
still grind off the gal from the heat affected zone before you weld though.
(if you do use mig, use straight co2 gas; no need for any argon mix for what you're doing, and it's a lot cheaper)
If using the mig on mild steel as a bit of a 1 of, just get some gasless wire it not as nice as gas but much better than carting a bottle around, and still no slag.
TIG is good for thin walled tube, sheetmetal, anything fine. You can apply the filler rod as slow as you like so can get a very nice finish (stainless handrails, etc).
Personally, unless you're starting a production line or have access to free gas I would just stick to the rods. Simple, cheap. Somebody may have already said it, but make sure you grind the galvanizing back to clean steel where you're going to weld. Zinc really doesn't like to be a part of the process.
Enjoy
J-P
If i was interested in buying a mig welder what would be the cheapest/ best options? would want it suitable for doing both steel and ally?
Can you weld aluminium well with a MIG? I tried it when I was first starting out and had rubbish results.
Of course, at that point I wasn't having much luck with steel either.
Now, my brother has mentioned getting the oxide from the aluminium first before welding. Does it make that much of a difference?
yes it makes a huge difference. the oxide melts at a much higher temp than the parent metal. so in effect it's 'hard to burn through' using dc current. by removing the oxide you get a much easier and cleaner surface to weld
it depends what type of flux cored wire you are using; most is electrode negative, some is positive. it will specify on the box
also you need to drag with gasless wire (like stick welding), but push with solid gas wire. and you should run more stickout than you would with gas wire (more wire distance from the tip to the work)
DC+ for stainless
AC+ for mildsteel ali
Change over your rollers for ali and drill out the tips +2mm because the ali will heat up and cause the nosil to block (thus jamming rollers) Allways keep your mig chord as straight as possiable.
Grind of any galvanizing before welding have adequate extraction will cause metal fume fever (weld outside if possible) If it is windy you may loose your gas shielding and this will create porosity(wormholes)Galvanizing gas can also weaken a weld (mixes with your inert gas) cause once again porosity wormholes.
If you have adequate ventilation it is possible to turn the mig up to full bore and weave weld burning the galvanizing off.
Anyways dont be a cheapskate buy 316 stainless for your frame ;-) and tig it 
Why straight CO2?
I run Argosheild for my UniMig 180 and found it to be perfect.
Don't ever buy one of those disposable bottles from Bunnings. If your doing some serious welding they run out too quick and end up costing you around the same for a bottle hire.
What rates are you getting on bottle hire?
straight co2 is cheaper than migshield. it runs fine for light and medium work. the main difference is the arc characteristics when you get towards higher amp work. co2 doesn't allow spray transfer across the arc where argon mixes do. but for working up to around 10mm plate (short arc transfer) with .9 wire co2 is adequate.
before i shut my shop last year i was paying 50 cents a day for bottle hire (with g size bottles)
Back when I was welding MIG wasn't even in widespread use. It was stick or TIG.
TIG was mainly for welding sheetmetal, aluminum and SS.
This MIG seems like some kind of shortcut to me for people who don't want to keep changing rods.
The top welders in my division stick welded the effluent pipes for nuclear reactors on submarines. To get that good they had their welds x rayed for porosity.
I would think stick welding should be plenty good enough for your project.
F N said
I saidbought a bottle from a guy advertising on ebay, where you can buy the bottles, and then swap them when empty. The bottle says 'atomic' but they seem to go under the name speedgas. Recently a tool shop in Taren Point has become a distibutor for them as well. I think (a while ago now) it was $199 for a E of Argoshield. I use it that infrequently that the BOC rental was costing me more than the gas.
I have to find out about that!!!!!!!!!!!!!! I have for the past few years paid more in hire than on gas for three bottles (mig and the oxy bros)
You could make your money back on hiring a bottle for boc if you were DIY fabricating infrastructure such as patios and sheds etc on your property.
I have one safety concern about my 3 in 1 MIG, TIG MMA welder.
There are three switches on front panel to change mode of operation.
I did try to measure polarization and voltage on MIG gun. Since there is no manual to explain I had to toggle a bit different combination of this switches.
As usual in MMA and MIG voltage on the wire protruding from gun range from 20 to 54 V. That is ok.
But when I toggle the switch on front panel to TIG mode suddenly my volt meter with 1,000V range going into smoke and sparks.
I did the test again with different meter since the fist got damaged with exactly the same, then again with third meter to make sure.
All three are dead now.
Well, since the MIG gun is permanently connected to the welder ( not like some newer Euro plug) that mean that when operating as a TIG but touching MIG or MMA stick coincidently could be quite danger (if not fatal - i cant test this 
I tough for a while test on a cane toad that right now are quite abundant at my place
) . If all 3 in 1 works like that or only mine ?
I tough for a while test on a cane toad that right now are quite abundant at my place) . If all 3 in 1 works like that or only mine ? (I say 'probably', as I am guessing a scratch start unit wouldn't send HV first)
you're right formula nova- tig uses a high frequency start to initiate the arc without needing to scratch. it is high voltage but low amps so is harmless. you can start it on your fingers and it feels like a mild tingle.
