tig tig tig

[ronan]

This maybe strange but I find aluminium tig more enjoyable than steel or stainless dunno why

Nice new aluminium yes, oil impregnated old aluminium castings god no.

 

[Chris Stevens]

Never had any problems with things like sumps. As long as they are steam cleaned or properly power washed first, doesnt take long to get the oil out using TIG torch.

 

[Richard.]

Never had any problems with things like sumps. As long as they are steam cleaned or properly power washed first, doesnt take long to get the oil out using TIG torch.

Then you've simply been lucky. Although prep is very important with this stuff and removal of contaminant is vital the major reason for it's poor weldability is it's composed of lots of unfriendly stuff to aid it's strength and brittle charectoristics. Quite high in silicon and manganese but also some contain traces of zinc copper and I've even heard lead can be present in there also. The oil in the bottom of the case is quite often the least of the problem. Some are purer and nicer to weld but some are awfull and no amount of prep is gonna change that.

 

[Chris Stevens]

I have done an awful lot of casting repairs over the years, ranging from car sumps to De-Havilland aero engine crankcases, and almost everything in between. The most difficult to weld are diecast motorcycle casings which seem to have a fair amount of zinc in them, and need to be done very slowly, and being careful to reduce heat input as much as possible. Up to now only thing that has defeated me completely is a magnesium wheel hub, which was badly cracked and only going to be used on a bike which was going to be displayed in a museum. Anyone with patience and a good selection of filler rods, should be able to repair most castings, as long as they are reasonable with a TIG set.

 

[Richard.]

Don't get me wrong Chris I've done more than my fair share of Alu cast weld repairs from minor cracks to complete build ups with a 100% success rate so far so I'm not saying it's not achievable as I'm very aware of the meathods used for results. But the fact I was making is they are 9/10 not easy to weld and the oil soaked in the case is not the biggest problem. It's the s##t they are made of.

 

[ronan]

The best way to clean castings for tigging is to soak the things in acetone. Old british bike castings are usually fine to weld as they seem to be very pure aluminium compared to japanese bike bits which appear to have to have more zinc in them.

 

[addjunkie]

Dish washer, then acetone. I agree with the old stuff being easier thsn the new tiddly wink ****

 

[hotrodder]

FWIW of the common casting alloys listed here http://aluminium.matter.org.uk/aluselect/13_cast_comp.asp only two have more than trace amounts of zinc but they also have significant amounts of copper in them which typically lowers weldability... EN AC-45000 / AlSi6Cu4 is classed as weldable, 46000 / AlSi9Cu3(Fe) is classed as either poor weldability or 'non weldable' depending where you look. The later is a flavour that is/was popular with VAG for gearboxes (they thoughtfully cast the designation into the case) and FWIW i've repaired dozens* of the things for several gearbox reconditioners. They, like most gearboxes or sumps, often 'bleed oil' no matter how much acetone they've been soaked in or how long they spent inside one of those industrial part cleaners that's like a dishwasher on steroids. Like Chris i rarely if ever have problems; sweat the oil out, burn off/float out any other crud or porosity sealants with the torch, tickle with a carbide burr and have at it. Castings that fight to the bitter end are usually ancient things that've turned mostly to Aloxide IME. Off the top of my head the worst i've done was watercooled cast alloy exhausts off a boat that was being restored; lots of time spent swapping between the torch and a die grinder but a fraction of the work involved to make new ones from scratch

Wider range of casting alloys listed here http://www.foundry-planet.com/fileadmin/redakteur/Material/08-03-10-Leporello_engl.pdf Most only have traces of zinc again, 3 that are actually 'high' zinc (similar/slighter higher in Zn to some weldable flavours of mag) are classed as good to excellent for weldabilty. The flavours with poor weldability all either have lots (>4%) of copper in them or it's a combination of copper and mag probably making them extremely prone to solidification cracking.
Similar deal with the wrought alloys... 7005 / 7020 is very weldable and around 5% Zn with only trace Cu while 7075 has a touch more zinc it's upto 2% copper, has more Mg in it too and welding it will totally ruin it if it doesn't crack immediately

* VAG riveted the crownwheel on instead of using bolts, the rivets fail but can't escape until they've done a poor impersonation of a fly cutter and machined their way through the case

 

[Richard.]

I have a small DIY pre heater i use to warm them up slightly and get an even temp through them. Makes things a little nicer for getting that puddle started especially on the thicker sections. Aids a little in evaporation off contaminants too although I don't take them too hot.

 

[Chris Stevens]

Done a few VW gearbox casings. and not found them to be any real problem. Casting repair really isnt that difficult, and other than a very large cast iron pump I repaired years ago, never needed to use anything other than a die grinder and heat from the torch to prepare reasonably clean parts.

 

[Richard.]

A slow/low preheat in an oven helps a lot I find to get things flowing. I certainly couldn't/wouldn't attempt to fit a gear box in it mind but little bike cases small sumps etc it makes all the difference again when the part is nicely warmed through.

 

[Richard.]

Met spencer today. Great guy.
Natural to say the least.
Forget about the pics posted at the top of this thread after a little management of arc length and travel speed the welding was bang on. Took to aluminium like a duck to water.

 

[God mode restorations]

A big shout to Richard for taking the time to help me.and I totally enjoyed the morning and came away happy and learned a lot...a top guy with awesome knowledge. ..thank you ...some pictures posted below..

 

[God mode restorations]

Once again I can't thank Richard enough. .can't wait until after Xmas as I will be investing in a ac/dc tig machine. .definitely the way to go....

 

[roofman]

No problem mate, I calls it as I sees it

oh you do do ya...ime no mig monkey..ime a half mig monkey and a half tig monkey

 

[God mode restorations]

oh you do do ya...ime no mig monkey..ime a half mig monkey and a half tig monkey

The beauty is I now have my eye on some new pieces. Some stubby gas lenses. A new regulator as mine ain't all that..the short gas lense first as far better than the long one I have...

 

[roofman]

The beauty is I now have my eye on some new pieces. Some stubby gas lenses. A new regulator as mine ain't all that..the short gas lense first as far better than the long one I have...

ive just bought 2 gas lenses,ive yet to try them out but by all accounts they help a lot with gas flow distrubution

 

[eSCHEn]

Spencer those are lovely beads on the mild and the Al ones are frankly, gobsmacking. Excellent work buddy!

 

[Richard.]

Spencer I agree you defo need an acdc job. You got on really well with that torch in your hand. Just to clarify at just how quick you picked things up the pic of the inside corner was your second attempt at that joint and on the 1st picture of Alu welds. The run closest to one of the drill holes was the 1st Alu run you'd ever done. (4th bead down) on that pic. You'll have them manifolds and cages built to exceptional standards by the progress you made I'm sure.

 

[God mode restorations]

Spencer those are lovely beads on the mild and the Al ones are frankly, gobsmacking. Excellent work buddy!

Thanks mate...