MIG Brazing

MIG Brazing - anyone tried it and can you do it without a special MIG/MAG welder, gas etc.

BobH

Yes, but not easy.

You need pure argon and not argon CO2 mix.

How To

Biggest drawback is the cost of the wire. I pay about £24 for a 15Kg reel of 1.0mm steel wire which believe me is cheap as I use a lot.

R-Techwelding list theirs at £38

Brazing wire in 12.5Kg reels is £354 inc vat, it's that expensive you can buy it on hire purchase at £53 per month !!

Even the small mini reels at 4kg are £172 per pop.

Audi use(d) it on their aluminium bodied vehicles. Seems you can (could) buy the machine.

Looks as if it's quite an interesting process but from what JS says, it seems to be rather expensive. I'd love to try it - it's possibly more difficult to blow through?

I used it some years ago and found it very good, did stainless tube and end caps, also very thin car body work (2CV). Not so easy on the thin stuff. I can not remember what it was exactly but looks like braze. I bought mini-reels for about £30 I think, can't find them now, and has been said very expensive

MIG (metal inert gas) and TIG (tungsten inert gas) are welding processes not brazing. They totally ignore the fundamental principle of brazing i.e capillary flow. Joint strength is dependent on the filler metal used not so with brazing.

You can weld with brass filler. You can also braze.Different techniques leading to different results.

Hi there, CuP,

(I ought to be able to remember your name, sorry!)

Your post is very interesting but tantalisingly brief! Please could you elaborate a bit?

Thanks and best regards,

Swarf, Mostly!

Re Cup Alloys -I hear what you say, but what is this ?
http://www.gys.fr/pdf/datasheet/uk/032002.pdf

Having said that , I think it is a very expensive way of achieving a brazed joint for MEs as others have said already.
BobH

My old arc welder has a high current output tapping (>200amps) that claims to be for brazing using a carbon rod as heat source and requires the use of gas welding goggles due to brightness. I have not tried brazing with it but have used it to locally harden motorbike clutch push rod ends many years ago. I can't remember whether it was case hardening or silver steel hardening though. Perhaps somebody has more knowledge of these processes? Colin

Colin, is that an Oxford or Olympic welder ? I have one also and did many feet of welded (Brazed) joints when I re-built my Austin 7. You need special bronze filler rods.
BobH

Very true.

Where it comes into it's own is on MODERN car body work where the modern metal panels are Boron Steel which cracks when you weld it and also looses it's high tensile strength.

Basically is a process that is led by the insurance companies, quite a niche market as regards a process.

Now TiG brazing of steel and cast iron is perfectly good enough and cheap enough using more or less standard rods.

Possibly what CuP alloys was talking about ?

TIG arc is simply a highly controllable (and completely inert) source of concentrated heat. Ideal for brazing as well as welding. If you have TIG gear already, TIG brazing is a lot quicker and cleaner than messing with flux and gas torches. The only cost is the argon - as opposed to fuel gas, flux etc.

I'd love to try MIG brazing some sheet steel bodywork to see how it works out but the reality is that beyond interest, I am unlikely to ever use it in anger. Another tool for the chest?

Murray

Just for interest-the MIG brazing wire I used is SIFMIG 968, dia. 0.8mm. None left now, if anyone does find a supplier of 0.5 kg reels I will be interested. This is used in a standard mig welder, not anything very special. No idea what the composition is, but as Jhon said it was developed to repair modern cars with high-tensile steel bodies and is accepted where brazed repairs are not.

Perhaps slightly off topic but for my 21st (late 1970's) I was given a 180 amp arc welder with a carbon arc torch. Still have it somewhere and seem to remember that brazing with it was easy. Very like an electric flame with no gas to worry about.

Welder was probably from Youngs of Twickenham.

Hi Bob, my arc welder is an oil cooled one made by Motorcraft of Middlesborough in Yorkshire. Can't remember when I bought it but must be more than 45 years ago. Colin

I bought an arc welding kit some 40 years ago to do some car repairs. It was made by Oerlikon (is that how you spell it?) and had a variable current output up to about 160amps. I could blow some seriously big holes in just about any bit of steel I tried to weld, so I bought a brazing attachment which used a couple of carbon rods to generate a fairly controllable "flame" à la carbon arc light. It used brazing rods as a filler and these were available in the local DIY store in France, along with the flux. I think I've used it twice in the last 12 years, so, in preparation for our return to the UK next month, I've just given it away to a friend's son and I'll be looking to replace it with a mini gas set, when I find a need for a welding/brazing kit.

John

John, be prepared to pay lots of pocket money for the gas. I prefer propane torches and MIG welding.
BobH

Brazing with carbon arcs is like using a ginormous great blowlamp. You also need flux or flux coated rods and it's damned hot work. In comparison, TIG (and presumably MIG) concentrates the heat exactly where it is needed, doesn't need flux and is highly controllable. If you have access to TIG, the choice is your classic no-brainer.

My TIG is a Miller Interlas 300BP, dating from the 80s I suspect. From a technical point of view, its actually a switched mode power supply operating at 50Hz. It has the minimum number of power semiconductors you can get away with (2 or 4 massive stud diodes depending on the mode) and 2 enormous magnetic amplifiers with a giant output choke. The whole thing weighs about 1/3 tonne but is controllable from a few amps up to over 300A in AC or DC with a foot pedal. They don't make them like they used to (thank god). I really ought to buy a modern inverter source one day...

Murray

Edited By Dave Halford on 03/06/2015 14:25:30

Edited By Dave Halford on 03/06/2015 14:26:22

Dave,

Actually, I had more in mind something like this:

http://www.weldairsupplies.co.uk/gas-cylinders-1-w.asp

I had a set before I moved to France, but sold them back to the above suppliers when we moved.

John