MIG Welding.

Firstly, I'm a welding novice (if that) so some of what I say could well be nonsense. What I say below has been picked up over the years,
from reading, YouTube, etc. It could be wrong.
My understanding of normal arc welding is that, in simple terms, you match the diameter of the rod to the thickness of the metal, at least up to a point. Obviously for thin metals, this is practical and you 'lay down' welds in layers. However, I'm thinking of reasonably thin metal, maybe 4 or 5 mm max. (Obviously you vary current etc. as well.)
Also, for thin material, like a car body, I understand normal arc welding is not really the way to go, and a MIG welder is the tool.
The conventional MIG welder, as I understand it, uses a thin 'wire' electrode which is fed to the weld and there is a bubble of inert gas (CO2) around the weld to keep it 'clean' etc.
I've seen a (new?) gasless MIG welder which has flux up the centre of the wire, it is rate at up to 90A and uses 0.9 mm wire. It is claimed to weld up to 5mm metal.
Now my confusion, I suppose you could lay down several welds but 90A for 0.9 mm wire seems a lot of current.
Can anyone help clear up my confusion, please?
I'm half contemplating getting a welder, from time to time it would be useful. My interest would be for semi-structural metal work, not car body work. Making metal brackets etc. Up to 5mm would be nice but I wouldn't need to do thin stuff like car panels. A gasless MIG appeals as it SEEMS more controllable and my dexterity can be a bit off at time. The idea of waving an ARC welder with a stick around doesn't appeal.
The beast I'm looking at is the Clarke one, probably their smallest gasless MIG.
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On 09/08/16 21:42, Brian Reay wrote:

I'm not a MIG person, but what's your confusion?
If it's 90A for 0.9mm wire, that's not really enough for MIG unless the steel is very thin.
You can't equate MIG wire thickness with arc electrode thickness, the process is different.

I have a friend who uses one of those, and it pretty much sucks. Only useful if you are doing small jobs on thin metal.
For thicker stuff, eg up to 5mm, you want a 200A or more welder. With a big bottle of gas (probably an argon/CO2 mix, not straight CO2).
-- Peter Fairbrother
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On 09/08/16 21:42, Brian Reay wrote:

For a start 90A and 0.9mm wire is nothing as my 160A gas MIG runs 0.6mm or 0.8mm wire, and I use 1mm wire when welding stainless but to some extent you're talking apples and oranges. A gas less MIG uses a hollow core wire so the wire size isn't the same as on a gas MIG as the conducting area is smaller for the same OD and the polarity is reversed which gives more heat at the item being welded which can mean it can weld thicker material for the same current but not as good on thin material. My experiences with a number of low end gas and gas less MIGs tells me that the wire drive is marginal power wise and various factors can lead to poor results which often leads the owner to ditch it or hide it under a workbench in disgust. I have been given 2 such units and with a bit of fettling and adjustment they run fine. My best advice at this point would be to find someone locally who has something like what you want and give it a test drive if possible and see how you get on.
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Thank you to you and Peter.
I know someone who, I believe, has a gas MIG, I can ask him.
I've also spotted a larger, more capable, machine, which does both gas and gasless, rated to 160A.
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Greetings Brian, Gas and gasless are two different animals. Gasless wire, otherwise known as fluxcore, is good for outside work where wind might blow shielding gas away from the weld. It is also good for places where weld appearance is not so important and for metal thicker than autobody sheet metal. Even with a small machine thicker steel can be welded if pre-heated first. When using shielding gas (MIG) the wire used in the low amperage (about 90 amps) machines is about .6mm. On thin metal the polarity should be opposite that when welding thicker stuff, say 1.5mm. I use a Lincoln SP125+ mig welder for steel up to about 9mm but I have to preheat anything over about 7mm. The machine is a low amperage machine. I use both gas and gasless wire depending on the application. But mostly I use gas because of the better weld appearance and because there is no slag to clean off. I don't know if Lincoln sells machines over where you are but I'd be surprised if they didn't. My machine is at least 15 years old and still keeps running well. You might be better off buying a used high quality machine. I did and it has been trouble free. The main reason low amperage machines are so numerous here is because they run on 115 volts. Since you have 220 volts available as the standard wall receptacle I would imagine 220 volt machines would be more popular there than here. And the 220 volt machines here all have higher amperage ratings. Eric
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On 10/08/16 17:17, snipped-for-privacy@whidbey.com wrote:

Thank you Eric.
I can't see me welding anything over 5mm. My interest is simple fabrication for projects, things like brackets etc. I would imagine most would be a 3mm at most. As for the appearance, I would think the limiting factor would be my skill, at least initially ;-) I have no illusions than welding is something that you can just 'do' without a lot of practice.
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You're Welcome Brian. There are some more things to consider. First of all, MIG welding is the easiest to learn. Learning to get good looking welds happens fast, having these welds actually be good welds takes a little longer. So after a while pretty welds will be in your skill set and if that matters then gas shielding is the way to go. Gas also allows welding of aluminum, silicon bronze, and stainless steel. The low amp welders can only weld about 1.5mm max aluminum though. And different gasses are needed for different metals. Fluxcore wire smokes a lot so if that matters then ya better get gas. You will probably find that wirefeed welding is fun and fast. The first time I used my machine I started laughing while welding because it was so much fun. When I bought my machine it came with a 10 pound spool of wire that was a little rusty in places. I couldn't use it for welds that matter but I could use it for practice. Since the bucket on my backhoe was worn thin in places I just practiced there. Another name for MIG welders is squirt guns. And the name fits. Making brackets and the like will go fast and you will be looking for other things to weld just because it is so much fun. Cheers, Eric
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On 11/08/16 00:27, snipped-for-privacy@whidbey.com wrote:

Thank you again, and to all those who have responded.
Being able to weld aluminium would be nice but I'm not sure I could justify the investment.
The suggestion made by another poster to attend a course is a good one. Being retired, I should be able (in theory) to spare the time, although (like others who have retired), I sometimes wonder how I ever found the time to go to work ;-), especially as we tend to travel quite a lot.
I will do some more research, including contacting a friend who does some welding (I'm pretty sure gas mig), and see what I think.
Regards Brian
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I've currently got a 90 amp MIG welder that I normally use with gas. It's perfectly OK with steel up to a couple of millimetres, but takes a lot of thought above that. With flux core wire, one can go a bit thicker, but cleaning of the slag on multiple passes is not a nice thing to have to do.
If you want to go MIG, seriously consider if you can invest in a higher current machine. With argon (instead of CO2 or AR/CO2 mix) you can get into spray transfer rather than short circuit transfer, which makes MIG welding really come into it's own.
Also, look around the local colleges to see what they are charging for Part 1 City&Guilds welding courses. they're normally 20 weeks of evenings or 10 weeks
Coventry in 2004. Didn't finish it due to severe work related depression, but what I learned has stood me in good stead for gluing lots of bits of steel together since then, I'm booked into Northampton college for doing the same with ARC and TIG at the Part 1 and Part 2 levels over the next year because I'm getting laid off and the company have allowed us a training budget as part of the package:-).
Regards Mark Rand
--
RTFM

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