Topic: welding gas suitability

[fuzzybutt]

i have a lincoln handler 140 mig welder and i'm going in the next few days to get a bottle and shielding gas. the question is, is there a gas or combination that i can use for steel AND aluminium? if not which is best for steel and which is best for aluminium

[droopy]

Common gas mixes for the home hobbyist and small fabricator for steel would be:

100% CO2 -Lowest price, generally greatest penetration, and higher levels of spatter. Limited to short circuit and globular transfer.

75% Argon - 25% CO2 -Higher price, most commonly used by home hobbyist and light fabricator, lower levels of spatter and flatter weld bead than 100% CO2. Limited to short circuit and globular transfer.

85% Argon - 15% CO2-Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and excellent penetration for heavier plate applications and with steels that have more mill scale. Can be used in short circuit, globular, pulse and spray transfer.

90% Argon - 10% CO2- Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and good penetration for a wide variety of steel plate applications. Can be used in short circuit, globular, pulse and spray transfer.



MIG welding aluminum is different than welding steel when it comes to shielding gas requirements. For aluminum, 100 percent argon is the gas of choice, whereas steel welding calls for a mixed gas or 100 percent CO2 gas. The good news is that no special equipment is needed - your existing regulators (with the exception of CO2 regulators) and gas hoses can be used for both pure blends and mixed gases.

[Sam Green Racing]

Well explained Droops, love your avatar

Sam.

[CaféElite]

Dont forget to fan the fumes away from you or wear a mask..

[fuzzybutt]

i have excellent ventilation in the shop and i have a small fan i use for fumes

[mystic_1]

Have you been doing flux-core welding before now?  If so you'll really appreciate GMAW.  I just started welding in the last few weeks and after doing a bunch of welds with GMAW, I ran all of two or three test beads with FCAW before deciding I hated it.  GMAW spatters less, and is much easier to watch the weld pool.  Also much less cleanup involved.

I suppose if I was welding rusty battleships outdoors, I'd go with flux-core, but in the meantime gas shielding is the only way I'll go.  I've been using C25 gas in my Lincoln HD3200, have not attempted aluminum yet.

mystic_1

[fuzzybutt]

yep all flux core welding to this point.

[troppo]

Great explanaition droopy, one thing to add if your machine is capable reverse the polarity when welding aluminium.
So for welding steel your torch would be positive and your earth would be negative. with aluminium your torch is negative and your earth is positive, one more thing with ali, you pull the weld rather than push like you do with steel.

[Steve F]

i have excellent ventilation in the shop and i have a small fan i use for fumes

Just don't have the fan blowing on the shielding gas as you weld as this defeats the purpose.  That's why flux core is better suited for outdoor work.

[Steve F]

Great explanaition droopy, one thing to add if your machine is capable reverse the polarity when welding aluminium.
So for welding steel your torch would be positive and your earth would be negative. with aluminium your torch is negative and your earth is positive, one more thing with ali, you pull the weld rather than push like you do with steel.

I was always told to use AC when welding aluminum, at least that's with TIG......I've only welded Aluminum with TIG, so having never welded aluminum with MIG, does MIG require reversed polarity???  The technique you described (pulling vs pushing) for aluminum is totally alien to me. 

[troppo]

I was always told to use AC when welding aluminum, at least that's with TIG......I've only welded Aluminum with TIG, so having never welded aluminum with MIG, does MIG require reversed polarity???  The technique you described (pulling vs pushing) for aluminum is totally alien to me. 

G`day steve
Mig and Tig are definatly different beasts, i wish i could tig to a decent standard.
Like you say a DC Tig is no good for aluminium, only for ferrous metals. My little tig is only DC so its ok for steel and stainless etc but not aluminium.
The pull thing for aluminium is something i have learned from a subby we have at work, he did his time building ally boats and says its quicker and less cleanup (not that theres much with ally welding)

You can weld ally with the normal polarity on a mig, but the conductivity of ally means it will suck the het out of the weld leaving a fairly brittle weld, if you reverse the polarity it apparently prevents this somehow, i`m no boffin so i cant give you all the techno babble but it does seem to produce a better weld.
Cheers mate
Troppo

[Steve F]

Thanks for that info, very interesting, but I don't see myself welding alum with a MIG any time soon.
Cheers!

[droopy]

Well explained Droops, love your avatar

Sam.

thank sam 

[fuzzybutt]

well i just got home with my #40 tank of 75/25

[mark]

well i just got home with my #40 tank of 75/25

That should make for some nice welding on steel projects.


My aluminum bumper got broken a coupla weeks ago. The argon bottle was dry. I picked up some 4043 rods for the stick welder and put the part back on. The welds look a lot better than the mig spew does. Go figure. $3K mig/spoolgun setup vs. $300 yard sale stick.