mig/tig welding/brazing?

[DaveH]

Hi

What I want to do is join some scrap metal together to make a sculptural object for the garden (don't ask). A mix of sheet, rod and lumps. I won't be able to accurately identify the type of metal - probably steel, iron maybe some brass? (no aluminium). I need to get acquainted with the methods I could use to do this. So far the likely methods seem to be mig welding, tig welding or brazing. A quick search show some tools that are basically electric and a different type using 2 bottles of gas. Since I will be joining lots of different objects I need a method that's as versatile as possible. Is there a dummies guide somewhere. Which of these methods should I be learning about?

[BigWallop]

An arc welder with rods that are Indiscriminate will do this. The rods are a touch more expensive than normal ones, but they will allow you to use differing metals with no problems.

Great on stainless steel to other metals as well. :-)

[Grunff]

WTF are you on about?? I've never, ever come across rods that can be used to weld steel to anything other than other steel. You can get dissimilar rods, which allow you to weld different types of steel together, including mild/stainless combinations. But welding steel to copper alloys??

[BigWallop]

Oh right. I better take these ones back to the shop then. Thanks for the heads up.

LOL :-)

[Grunff]

Good plan.

[BigWallop]

Well, they do work beautifully between Aluminium Drop Forged Brackets to Stainless Steel Camera Housings, so I think I'll keep a couple on hand for now, if you don't mind that is?

:-)

[Grunff]

ROFL - love it - so you're saying you've been arc welding aluminium to stainless?

[Dave Plowman (News)]

If you stick to steel, then ordinary arc welding is cheap. If you need to join two different metals, and they're compatible, you'll need brazing. And brazing sets are as you say two types of gas and much more expensive to buy and run.

[Steve Walker]

You're just jealous, cos you can't do it..... :o)

[Grunff]

Damn right I am.

[BigWallop]

I ain't no metallurgist or chemist, but I was told by a bloke in Nu Fab UK to use these types of rods. They are called "Indiscriminate" with a code of "TLD 3.4is" and are not the dis-similar ones you speak of. The don't burn in like a normal rod, but they sort of melt and pour. All I know is they work, and work well for what we needed.

We wanted to stop the locking nuts from being un-done on camera housings, and when we asked around for ideas on what to use, the guys at Nu Fab UK came up with this idea. The rods are expensive, but when we worked out how many of the little welds we would get from one rod, the concept was just what we needed.

The locking nut is stainless steel and the bracket is drop forged aluminium, so it's quite tough, and the weld is done on two or three faces of the hex where it touches the bracket. The whole thing seems to melt together quite nicely and leaves a strong bond so the nut can't be un-screwed. They work, and we like them.

[Grunff]

Noo!

Do you even know what arc welding is?

[Chris Bacon]

Why can't you use carbon pencils and an arc welding set?

[BigWallop]

Yes. I've been doing it for a few years.

[Dave Plowman (News)]

It can't be a weld obviously since that can only be between identical metal.

But this sounds interesting. Some form of 'braze' that works on stainless but doesn't melt ally?

[BigWallop]

And they work on quite low settings, though the ones we have are thin rods, on a small arc welder. The rods are definitely called "indiscriminate" and don't arc like a normal rod. As I said to Grunff, they sort of arc to a point of melting and pouring from the end of the rod. The flux coating seems more rigid than the normal rods as well, and more green than the bluey tinge of other rods.

Watching them is great fun and has me fascinated watching the three metals sort of pour together. They give a redder glow through the filter glass rather than the normal yellowy glow of a normal rod, if that gives any more ideas on what they're made from.

Al I know is they work, and work well. We've used them for copper to ali', steel to ali' and copper to tin, though that failed because it was thin sheet pieces that kept blowing through, but I think it still would have worked.

I've tried a web search but can't find anyone who sells them. I could have showed a picture or description of them. We get them through a fabricating company (shhhhhh) to get the discount on them.

[dingbat]

They _might_ be "Lumiweld" or similar, which are a solder and not a welding process. They won't work between aluminium and stainless (simultaneously) either, unless you use a non-standard flux, which is a little on the hazardous side (fluorides) and the heat control is tricky too.

There are no electric-arc processes for welding stainless to aluminium.

Oh, and your aluminium isn't "drop forged" either.

Why _do_ you bother posting your rubbish?

[dingbat]

There are plenty of heterogeneous welding processes around. They're somewhat obscure, but they're common enough when you need them. All you need is a filler material that is easily dissolved in the parent material - nickel rods for arc welding cast iron are one, some of the gas-torch bronze welding processes are another. Then there are the non-filler process like explosive welding to laminate plates together, some friction weld process for spin-welding fastening studs onto sheet, or even an 18th(?) century technique like making Sheffield Plate by diffusion welding silver foil onto copper sheet (heat, time and pressure).

[dingbat]

Don't buy the kit, borrow it or find a course somewhere. It'll be cheaper, plus the other advantages.

If you just "want something welded", pay someone to do it. If you're in Bristol or South Wales, mail me.

Gas welding costs a fortune because UK bottle rental is a rip-off. It applies on a smaller scale to MIG welding too. OTOH, oxy-acetylene kit would let you use welding for steel-steel joins and brazing for steel-brass/copper, all with the same kit.

Electric welding is cheap for manual stick (1/4" steel and upwards, maybe 1/8" if your hand is good, but not really much lower thickness). Wire-feed (MIG) welding is great for sheet and thicker stuff too, but it's not cheap equipment if you want to do it right. Don't buy any new MIG machine for under =A3300 (Cebora, Murex) - if you're getting a Clarke or similar, buy it S/H and save some money - they're all a bit rough at that price range.

You can't afford TIG.

You can't electric weld anything other than steel. Cast iron with difficulty and expense. Forget it for non-ferrous cuprous, aluminium, stainless or mixtures.

Stainless steel with silver solder beautifully with O-A, or even propane, but the materials are pricey. For other methods it gets difficult - wire-feed will do it, if you do it right (right wire, right gas, right machine).

Welding is the easy bit. There's also the cutting and shaping first. This is harder and takes a ridiculous amount of time (it has just taken me 3 days to make two sets of hinges!)

There's no "dummies guide", because this isn't a process for dummies. The best single book I know is Gibson's "Practical Welding"

[Dave Plowman (News)]

But isn't that more akin to brazing?