Welding and Materials

Yetiman · #1 (**permalink**) 02-22-2006, 05:16 PM

Cleanliness IS godliness where the metal meets the metal !

mickmate · #2 (**permalink**) 02-22-2006, 08:44 PM

The stainless brush should be used only on your aluminum and not get contaminated with any other uses. MIG is good for thicker aluminum but requires at least a teflon liner or better yet a spool gun. It runs hot and fast and requires a push technique for gas coverage and a big contactor to work gap as it is actually a spray transfer process. TIG is good for control and thinner materials. It is a bit of a head game as you have to break through the oxide and make a molten puddle to get it going. Once it is going it really crackles and spits as the magnesium alloy in it burns. There are some good tips and tricks on these at the miller web site.These first two make too much heat and distortion on your freshly hand beaten body panels. For that you need to braze them together with a flame and flux (or flux core) and rod. There is some awesome Cobra and other aluminum car stuff as well as good information on the tools, tin knockers links etc at http://panel-craft.com I didn't mean to make it a sermon. I just happened to be trying to dial in a spool gun at the moment. It should be worth it and save me a lot of TIG time on a big job I'm doing. Good stuff ain't it!

Aussie Mike · #3 (**permalink**) 02-22-2006, 10:45 PM

I spent a bit of time getting my 200 Amp Mig running aluminium and I'm getting good results now. mickmate is right, you get your best results in spray transfer. That means lots of current and wire and a steady hand cause you've got to work quite fast. I've been welding thicker materials with mine and getting quite good at it. Preheating larger pieces certaily helps. I've got a portable gas stove that I sit the larger work piece on. I welded up a manifold for Bernies Cobra a while back and the gas stove worked a treat for preheating it.

Getting the teflon liner, rollers and tip right is the key I reckon. I went through 2 liners getting mine right. You need to set up the liner so it so close to the rollers that it rubs on them. This stops the wire from bunching up at the rollers if your arc goes out and the wire hits the work piece or if it sticks in the tip. You also need the brass sleeve that slides over the outside of the liner to keep it straight where it meets the roller.

U grove rollers have more surface contact with the wire and mean you don't use so much tension on the pinch roller. The wire will still drive smoothly but you can back the tension off enough that the rollers slip if the wire jams. It takes a bit of experimentation to get the pinch roller tension right.

The other trap is the tips. 0.9mm aluminium wire tips have a larger hole than a 0.9mm steel wire tip. Aluminium expands more when heated so it needs a bit more clearance or it'll jam in the tip. If you don't have any aluminium tips available just use the next size up steel tip i.e. a 1.0mm or even 1.2mm steel tip for 0.9mm aluminium wire.

You can get some great results on nice clean billet aluminium but castings can have variable results due to the porosity of the material and casting sand trapped in the pores. The weld may look good on the outside but hit it with a grinder and you may see bubbles.

Here's one of my home made quick jacks prior to polishing. They were water cut from 6mm aluminium plate.

Cheers

Michael

mickmate · #4 (**permalink**) 02-23-2006, 06:17 PM

Hey Mike, that is a beauty piece of work! I have a question as I play with dialing this spool gun in. Are you running a weave to the bead? I am going like stink across this thing and don't know if I'd even have time for a weave. It seems I have to go fast to keep it cool enough to not burn through. The push with a slight angle helped a lot on keeping it more consistent along the weld. I'm going to play and see if I can come even close to what your doing

Cheers

Aussie Mike · #5 (**permalink**) 02-23-2006, 07:25 PM

No weave for me either. It's fairly blazing in spray transfer and you have to move quick. I run my torch in at nearly a 45 degree angle with about a 1 to 1.5cm arc. If I have it too close I find I too much buildup of spatter in the nozel. With the torch at this angle you can see what the pool is doing and push it right into the root of the fillet.

I've never been much of a weaver anyway. The only time I really do is a second pass, the root run is usually straight in to try and get the best penitration. I'm just a back yard welder but I think being able to watch and carefully control the pool is the key to getting a good result.

Cheers

mickmate · #6 (**permalink**) 02-23-2006, 08:17 PM

Great advice thanks. That seems like quite the angle Miller recommended a 10-15 deg. I'll try your method and see what it does for me. I'm going for it tonight I'm even inspired to try and attach a pic.

Aussie Mike · #7 (**permalink**) 02-23-2006, 09:09 PM

It's probably more like 30 degrees now I look at it and think about it.

Nice looking weld, is that aluminium?

My next big aluminium welding project is building a blower manifold for to fit an Eaton M112 onto to my LS1. I'm looking forward to doing it but have a lot of other jobs to finish first.

Cheers