Aluminium MIG is it suitable for building up?

[AndyStobbs]

I need to build up a damaged area of alu casting on my jet ski engine. Its a tricky position that would mean torch angle would be very low - 25 degrees. I have never tried Alu welding with the Mig and my TIG set is dc only.

Essentially if it was steel I would just keeping dotting blobs onto each other, it doesn't need to be neat and it doesn't have to be any stronger than just enough to stick. Its the circular apature where the starter motor pinion pokes into the engine, someone has drilled the original starter out - badly.
So is alu mig upto the job - in that can I keep blobbing bits together or will it all go south?

Thanks.

 

[Shox Dr]

Presumably you have a mill to reinstate the hole, if so why not sleeve it

 

[AndyStobbs]

Not enough material to do it, or I would. Got the lathe set up to re finish the hole.

 

[Rig Pig]

What about using alu soldering rods to build it up and fitting a thin brass bush to take the wear?

 

[RonA]

What about using alu soldering rods to build it up and fitting a thin brass bush to take the wear?

Yes I agree with Rig Pig, if your going to weld the damaged part, I no expert but I would think you need to know the metallurgy of the casting to ensure your using the right welding wire.
On the other hand, soldering rods work well on a range of aluminium alloys. I had very good results repairing a oil filler funnel on a vintage car made of a Mazak type alloy. The repaired flanges on the oil filler funnel have proved very strong & the repair durable.
RonA

 

[Jrstainless]

Mig welding aluminium is a strong weld but not the prettiest,which in this case wouldn't matter.I'm unsure about welding a casting just set your mig up and try to spot it, then if it will work build it up. You've got nothing to loose!
Jr

 

[AndyStobbs]

Tried it with the durafix type rods last night, I was throwing heat at it with the the oxy for nearly 30 mins and it still wasn't up to temp. Still attached to the rest of the engine, so its a damn nig heatsink.

 

[Richard.]

I'm far from an expert but I have successfully repaired a couple of bike casings (tig mind) but a couple of basic rules with Ali casting. There is already enough s##t in it so don't add to it with sand blasting, don't pre heat and a consumable I found works for it is 5356 (someone may be able to suggest better). If it's any thing like the ones I have repaired it will weld quite "angry" and "flustery". It's far from easy and I suggest looking at the far better options posted above before taking it on.

 

[Richard.]

Forgot the most critical one. Clean it till you bleed. If it's been sand cast and oil has got into it I would say you stand little chance.

 

[Kent]

Just give it to a guy with an AC/DC TIG, as Richard says cleaning required this can be worked on further with TIG but mig will just lay down wire "fast" over the contaminates making it holier than the Pope

 

[AndyStobbs]

My usual TIG guy is presently unreachable or I would've just given it to him.
Well I got set up with a roll of 4043 and had a quick doodle on scrap to get the welder setup and generally get my eye in. Moved onto the engine and laid down some bloody ugly welds, will see how the deposited material looks once machined back.

This area of the casing has not seen oil so its clean in that respect. Very skittish welding process seem to have to hold a much longer arc than for steel, and you can't see the material going down (not helped by the fact I'm welding runs 25mm long axially in a 30mm dia hole) always wanted to try it so its not wasted effort. If I'm not happy with it then I will get it TIGed.

 

[Montreal]

I tried this recently. Converted my Sip 90amp to Ali to weld an oil filler cap edge that had been ground. Worked very well and near invisible I machined to match original profile.Set wire speed to very fast as it wants to burn back. It is almost like spraying the wire on very fast. 0.8mm 4043 wire and a 1.0mm tip, teflon liner.

 

[AndyStobbs]

I'm using the same nylon liner that I was using with steel wire, just standard 4mm nylon tube. I drilled out a 0.6mm tip to 1.x mm that seems to be working ok. Definitely feels like spraying, also get this wonderful effect immediately after stopping the weld, looks like a miniture flame front moving across the metal.