MIG Welding Gas vs No Gas

I recently found myself wishing I'd invested in a small welder (yet again*) when trying to make something. So, I'm looking at the options of
buying a simple one, suitable for basic 'fabrication'.
I'm looking at one from Machine Mart which gets good reviews, seems to cope with 4mm mild steel (I can't see myself wanting to weld anything thicker) and from the comments, others have used it for car panels so it does thin stuff (although I don't expect to be doing cars).
local gas cloud around the weld).
wise' (although it seems to have extra cooling so probably will do longer sessions). However, it has the facility to also use gas.
Being a beginner (I did some arc welding in 6th form and a few times since but, essentially, I'm a novice), I'm not sure if the gas facility is worth it, ie what do I gain?
One thing that would be a 'nice to have' would be the ability to weld aluminium (not something I've done before). Will a gasless Mig welder weld aluminium or do I need gas or some other welder entirely?
*I've always found a work around in the past, as I did this time but I can't help thinking of the time the work arounds consume.
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I have never seen flux cored aluminum wire and even if it was made I'm pretty sure it wouldn't work with a small machine because of the high amperage requirements. Even with gas, aluminum welding with a small MIG machine is problematic because of the high amperage required to weld aluminum. This means only thin stuff (about 1.5mm max) can be welded which means only the thinnest wire can be used and it doesn't feed well. With shielding gas you have many options for wire and gas combinations. this allows you to weld many fifferent materials, from plain old steel to stainless steel to silicon bronze. You can even braze steel with silicon bronze wire. Using only flux cored wire pretty much limits you to welding steel. And flux cored wire has lots more spatter than gas shielded wire. But flux cored wire has its place. Welding in windy conditions for example. There is even made a flux cored hard facing wire for low amperage machines. I have a spool of it that I use to hard face coat various earth moving equipment surfaces. I think you would be better off looking for a used Lincoln, Miller, or Hobart machine. My little 140 amp Lincoln SP 125+ welder is over 20 years old and has never had any problems. I bought it used about 15 years ago and it gets regular use. The controls allow much more flexibility in voltage and wire speed control than the cheap Chinese machines. Eric
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On 03/09/17 10:42, Brian Reay wrote:



I don't know that much about MIG (I mostly do TIG, and occasional stick), though from watching a friend gasless/flux core MIG is good for outside rough steel work when windy.
Indoors, gas generally gives a much better result - better formed welds, less spatter, no horrible post-weld cleaning, etc..
If you get a beefy 200A plus welder (250 plus for ali) you can do spray MIG, which afaik gives the best results MIG can do. But it will cost quite a bit.
Apart from that, if you are getting a small cheap one for short-circuit/droplet transfer use on smaller thinner stuff, up to say 4mm steel, 3mm ali, don't worry quite so much about maximum amps, watch for the welder's duty cycle - you want at least 30%, and 50% or more is better, at the current you are going to be using.
"Duty cycles are rated over a 10 minute period, so (in theory) a 60% duty @160A machine may be used for 6 minutes (60%) at 160A in any 10 minute period." In practice, it may not work out quite that way ...
Variable inductance can be especially useful in smaller MIGs, but it is not always available - and some consider it just another knob to get right (or get wrong...).
While it is theoretically possible, as a matter of practicality I don't think you can MIG weld ali with a gasless wire.
You may want a spool gun for ali, especially with a lower-powered machine. You also need about 25-33% more power than for a similar thickness of steel. And a cylinder of 100% argon for ali, the bigger the better.
Gas can be an expensive consumable, it's cost needs to be figured in. Pure CO2 is cheaper than 100% argon (essential for ali) or 75% argon/25% CO2 (best for mild steel s.c./droplet transfer MIG), but pure CO2 is best kept for thicker steel and where spatter doesn't matter. There are other gas mixtures for special purposes.
Thankfully, nowadays the monopoly on rented gas cylinders is breaking, and you can now get a large steel cylinder on a returnable deposit basis. I do not recommend the disposable gas cylinders except for emergencies.
It may help is someone can eg show you how to set up your machine, or give a few initial lessons, but practice is the best way to learn the skill. It is quite feasible to learn to MIG weld from eg youtube videos.
-- Peter Fairbrother
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On 03/09/17 10:42, Brian Reay wrote:



My experience with the low end welders is that they do work but can be troublesome to set-up. I've been given 3 over the years and was asked to look at another, the owners bought them and found they couldn't get them to work properly so they sat under the bench till I got them. They all worked but some required fettling or just adjusting correctly. I see the main problem is the wire feed motors are marginal on power and various things can lead to varying wire feed rates such as poorly moulded wire spools and the D threaded wire spindle jamming, the varying speed made setting tricky. Another had a knurled feed roller, maybe intended for flux core, and it wouldn't slip leading to bird nesting if the wire stuck to the tip. I would suggest if you can find someone in your area with a similar machine ask if you can try it and buy them some beers and see how you get on with it.
If you can find a decent 2nd hand machine of better quality that would be my suggestion. My Eland 160A I bought in 1985 is still going strong with only the power lead having failed, i suspect I dropped something on it at some point, it's a light industrial welder bought new.
I have the bits to weld aluminium but have never needed to do it as I have TIG. I have been told the low end welders will weld thin aluminium with gas shielding by someone that tried and failed but a mate of his worked at British Aerospace IIRC as a welder and came in and did the welding fine with the low end MIG welder, again a matter of set-up and skill.
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On 04/09/17 20:22, David Billington wrote:



Thank you, and everyone, who has replied.
I think I will 'shelve' the aluminium idea- it was just a 'nice to have' but is seems like is may be more than can be achieved with a basic(ish) machine.
As for the welder, I will see about either a second hand one or if I can find someone with a machine they know and can demonstrate locally- I know a few people with welding machines, I just tend not to see them as often as I once did due to travelling etc.
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