cleaning

[snowcat]

I had a large AL manifold from a Volvo FM truck ,come in today in for a PDQ repair, as usual with these things despite steam cleaning, degressing, cleaning till bright, then using liberal amounts of brake cleaner, 7 years of filth kept appearing in the welds, this a regular problem with these sort of jobs, especially on cracks where oil just lurks, adjusting A/C balance and frequency only does so much.......

anyone have advice on a cleaning procedure and product(s)....

 

[Hitch]

We use a product for cleaning aluminium, called alishine.
As for cleaning well enough too weld, if its gone back bright ally, sure its not cleaning product in cracks?

 

[weldequip]

I'm sure there's some chemical procedure but I'm not clued up on it, have you tried abrasive polishing discs?
weldequip

 

[snowcat]

We use a product for cleaning aluminium, called alishine.
As for cleaning well enough too weld, if its gone back bright ally, sure its not cleaning product in cracks?

I think its due to the AL being porous, turbo pressure for 300K not to mention road salt, and other crap....

 

[stormin]

It's likely that the alluminium casting has a lot of Zinc alloying in it. This is may be melting sooner than the ally and oxidizing quicker during welding, causing you the problems.

 

[hotrodder]

Was it actually 'bleeding' oil during welding and /or preheat or was it just 'dirty' to weld?

Had some really old castings before that were very porous and no matter how well cleaned (degreasing tank and an industrial steam cleaner) would still bleed oil. Loads of fun sweating the oil out with oxy!

More usual to have a poor casting... lots of small porosity trapping all sorts suprises that bubble up through the puddle and pores opening up just outside the toes of the weld.

An approach i often use is to (assuming it doesn't start bleeding during preheat!) run the arc along the joint just barely melting it. This tends to pull a lot of the crap to the surface/expose porosity. Grab the die grinder again, find clean material and repeat.

Sometimes they weld nicely after that others they weld 'dirty' regardless but at least you can get a sound, air tight repair...



Done a lot of these gearboxs, always weld fairly dirty- a fair bit of porosity to chase and the alloy itself doesn't help, a silicon copper containing iron and zinc too

 

[hotrodder]

Oh, forgot something that may help/is certainly worth trying...

I've not had the pleasure of using kit capable of a high frequency pulse (> 100Hz) with AC. Supposedily the extra aggitation of the pulsed arc helps float crud to the edges of the puddle and burst any porosity bubbles.

 

[snowcat]

thats exactly the problem bleeding, with all sorts of surprises, the approach I took was exactly as you described roughed it out first ground back then a pass over the top, there was a couple of bits that despite best efforts still produced crap, as you said the purity of the original casting is dubious, but I think 95% of the problem is dirt especially oil in a porous casting.....

btw I found a very high frequency A/C cycle the lorch will wind upto 200Hz helped......not my ears tho...

 

[hotrodder]

Normal AC is bad enough without ear plugs much above 100Hz, muxt be a pretty atrocious noise with a hich frequency pulse too!

I think you've done pretty much there is to do prior to firing up the welder. Worst i've ever seen was part of a set of slip rolls that got broken- been soaking in oil/grease for longer than i've been alive. After the usual cleaning treatment it looked like new but heat it up to a few hundred degrees and oil was literally running out of it- would never have believed the amount it held if i hadn't seen it. several heatings and degreasings and it was still impossible to get a sound weld