Gasless MIG welding

I think the thing about a good inverter welder is that they clamp the current almost instantaneously once the arc is struck. An old style transformer welder inherently controls the voltage rather than the current so by altering the arc length you have some manual control over the actual weld current and heat input. The AC output helps as the continual voltage cycling between zero and peak reduces the average heating input but still has a decent peak to make the weld. Sort of like an uber fast preheat - weld cycle I guess.

With a DC inverter what you set is what you get. If you set a bit too much it rapidly burns through due tothe continuous heat input. Strike voltage is generally higher so arc starting can be more reliable but breaking the arc harder. My Fronius needs a very quick pull back to break the arc. If you want to play silly games on higher current settings a slow, careful pull back can stretch the arc to 6 or 8 inches long before it breaks!

Good Inverter welders can work with a very short arc length. Which helps on thinner materials as the ent heat input is less. With the right balance of current and metal thickness its possible to make good welds between well prepped edges by simply dragging the rod own the joint with a little side to side movement. Handy on vertical welds. But a trick I've not yet mastered. About 50/50 good/crap ratio. The good ones are amazingly clean joins.

John is absolutely right to say that the art is getting a sufficiently capable machine able to do relaible work without too much operator compensation. The usual price performance ratio.There is only so much capability you can pack into a lower cost machine so the operator generall has to work harder. Which makes life difficult for neophytes.

Clive

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I wonder … did anyone else ‘attend’ this webinar ?

MichaelG.

I've joined quite a lot of thin steel assemblies over the last few years, mostly SHS with wall thickness around 1.2mm but also some sheet down to 0.8mm using a plain inverter MMA welder and 2mm rods. Like others have said, the trick is plenty of current and short 'stitching' beads all linked together. Too much time spent in the one spot will certainly blow a hole, but these are repairable. Sometimes i stick the bare end of another rod into the hole and weld over it, other times a spare scrap of metal from the waste bin, even ordinary nails are useful for this. Like other skills it takes time and practice to reach any level of proficiency, and a touch with the angle grinder afterwards hides most mistakes.

If your welding any sort of hs then angle the torch or rod towards the section that is not cut and allow the weld pool to flow onto the cut section. the non cut bit can absorb much more heat before problems arise allowing a good looking weld with proper penetration. I am a coded welder with 30 years experience in derbyshire....

hope above made sense..... just re read it, not so sure. ho hum

Yes, I think that makes sense Phil - thanks for your input. What I've been doing is making a series of tacks as in A in this sketch:

Sometimes (~70%) it works, sometimes it doesn't. When it doesn't it's because once I've blown through the cut edge the arc just runs away and makes it worse. Would you do something more like B? That is traverse across the 'non cut' bit without any weaving and let the pool melt the cut edge?

I've pretty much given up using stick welding for this project because I need 100% success when I make the frame and I'm not going to get there in in time.

I have now tried silver soldering, which I can do confidently, but I have never tried a joint like this before - I was worried that it would be weak because it's (sort of) a butt joint. I was surprised how strong the joins are though - after application of a FBH the tube bent and the joint just gave me a smug look. More expensive and slower than welding of course, but it'll get the job done.

Robin

Diagram b is the way to do it. Put a tack on each corner first so you have something to weld into.

I didnt want to get into a debate about stick, mig, gasless and tig welding as all have advantages and disadvantages.

I have all these machines and if i were doing your project i would mig it without a doubt. Mig welding is the easiest to control.

Dont go using pub bottles of co2 as this gas reacts with the weld pool and increases penetration. Its actually called mag welding, the i in mig stands for 'inert gas' and the a in mag is ' active gas'

I have used pure co2 many times on thick sections - above 15mm thick for ultimate strength after preheat. It is hard on your torch and consumables, produces alot of spatter and gets really hot.

As a solution to your immediate problem would you want help / allow someone else to do it for you?

I have a small gasless mig welder that could be chucked into the car and brought over to you. I also have a a pair of hands available, and a welding mask... I am not trying to muscle in on your project but the offer is there.

The gasless mig is a bit harsh but i am confident it will do the job. After a bit of clean up it will be ok.

I would bring the mig and a bottle but its big and very heavy.

Might have been suggested already, but can you hire MIG welders?

If it's only one job and you don't want to buy one.

Edited By John Doe 2 on 16/04/2022 10:50:17

If the op is near moreton in marsh he is welcome to bring it to me and I will weld it for him , although I mostly gas weld aluminium now I do still use mig a lot , as I have just finished fabricating parts and mig welded them in a R/R Shadow so I am used to mig welding thin steel.

PM me if interested Dell

welder - many thanks for your kind offer. I have sent you a PM.

John Doe 2 - I don't think the suggestion of hiring has been made earlier. It looks like I could hire a MIG for about £60 a week, but I'd have to buy or hire gas on top of that. Might as well go the whole hog and buy a welder - bound to come in handy in the future!

Dell - unfortunately I am about 100 miles away from you, but thank you for your generous offer of help. Had you been nearer I'd have been round like a shot. Aluminium would actually better for this, but I couldn't find anyone local with the skill/kit to do it for free - it's a "community project".

It might seem nuts that I'm considering buying a new welder for an unpaid one off, but that's how it works for me. My workshop activities are more about journeys than destinations I suspect.

Robin.