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 ?

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.

Beaglebuddy said...
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.

It seems to be a consistent opinion though. I have read this a lot.

CJW said...
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.

+1 use the MIG.

**When you're welding gal, please ensure you don't breathe the fumes. Your best to weld outside, up your reg to around 25 and use a fan to remove the smoke away from your face. Upping the gas flow will compensate for the fan. Have the fan around a meter away from your welding area and strong enough to move the fumes but not too strong or you'll blow the sheilding gas causing a porus weld.

If you havn't already found it, I use this website and the set up calcualtor takes the guess work out of setting up your MIG

www.mig-welding.co.uk/calculator.htm

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.

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?

stamp said...

ok said...
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?

'cheap' and 'good' do not exist together when it comes to welders. buy a second hand lincoln, miller or kemppi before you buy a cheap new chinese welder.
check the duty cycle on the back plate, the higher the better.

if you're welding ally you need to buy oversized tips and a teflon liner, and ideally a different roller set. you will also need to run pure argon.

aluminium is dirty horrible stuff to weld and takes a lot of practice to get right. you also need to clean the oxide layer off the top with a wire brush before you weld.

I should do this but is too late. Bought this cheap Chinese MIG welder 3 in 1. Inverter technology and I could warn you guys already.
I did try flux -gass less welding first and result was terrible. Then on Youtube I found that for gas less I should reverse polarity from DC + on MIG gun to DC-.
Buth this Chinese welder doesn't have this option ! I called dealer, he don't even understand what I want from him, There is sparks , than mean it works.
So I opened the box and swith cables myself and this time the weld quality is much better in my test run.
So for gas less - the MIG gun should be on reversed polarity ( - ) negative
Are you all agree, guys ?

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

busterwa said...
<snip>

Anyways dont be a cheapskate buy 316 stainless for your frame ;-) and tig it

I couldn't be bothered changing wire spools once, and used the stainless one that was in the unit. It might be okay if you can weld well, but if you are like me, you need to do some grinding.

Stainless wire is a bugger to grind!

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)

FormulaNova said...
Can you weld aluminium well with a MIG?

Yeah you can, the mobs that build plate ally tinnies all use MIGs. I did work experience at one, and with the set ups they have, welding ally is easy.

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.

Macroscien said...
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 ?

TIG 'probably' sends a high voltage pulse to start the arc, and then goes back to low voltage. This is probably what made your meters make smoke. Try it again, just in case it was 3 faulty meters (I say 'probably', as I am guessing a scratch start unit wouldn't send HV first)

I know the one I have initiates a spark, and without even thinking about trying to use a meter, I am guessing it is high voltage. No, I won't touch it with my tongue to find out either

Edit: As you haven't shown us a picture of the front of the unit without the multimeter in front of it, please note that a lot of units have the same plug for the gun and the ground lead. This is so that you can swap them for gasless wire, and I am guessing aluminium TIG.

Does it by any chance show a picture on the front panel of a gas bottle on one side, to show which one gets used for normal wire?


Edit#2: For what its worth, I would be amazed (read - really amazed) if the unit changed its own polarity internally when you switched between modes. There would be no point when it is much simpler to change the polarity on the plugs on the front of the unit. The relays/contactors you would need for that arrangement would be huge and a waste of money.

Does it actually have a gas solenoid in the unit, or valve in the handset, or is it meant for gasless mig or TIG only?

stamp said...
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.

Not to multimeters apparently