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Problems TIG welding castings?

Classicbike

Plastic
Joined
Apr 6, 2008
Location
Southampton, UK
Wonder if anyone has experienced problems with honeycomb type blow holes appearing in and adjacent to the weld pool area, when welding relatively thin aluminium castings? I get the feeling this might possibly be hydrogen inclusions of some sort, maybe caused by shielding gas issues?

Only seems to occur on castings which are thinnish and which may well be made out of low grade material (various motorcyle parts). Be very helpful if anyone has had the same sort of problems and found a way to overcome them..........
 
Often motorcycle castings subject to heat (e.g. engine cases) are both porous and oil-soaked. Not much you can do about that except boil it in a detergent solution. That it's not high-purity aluminum is pretty much a given if it's an older Harley...
 
Oldwrench used the keywords: porous and oil-soaked. I’ve reluctantly welded engine castings for 45 years and that’s the problem even when the customer/friend says “I cleaned it really good” when you strike that arc and get that heat in the oil finds its way out.
 
Had a vapor de-grease set up at the machine shop I worked at, don't know what exactly was in it but a guy put a motorcycle head in it and you could see the oil coming out of the aluminum. It wasn't set down in the solution but on a shelf above so it was the vapors that were actually doing the work.
It blew a head gasket and ate a trough out of the gasket surface that he wanted to fill with weld and then re-machine. The welder told him he had to use that de-grease method before he'd do it and it seemed to work out.
Dan
 
There are many factors that can result in porosity when welding an aluminum casting, including, as noted, oil in the pores.
that is easy to eliminate by heating the parts with a torch to about 500 F but you will still have carbon left, depending on how much oxygen is available to burn that off.
The casting itself is going to have dissolved gassed trapped in it as well, but I don’t think hydrogen is really a critical factor here, nor is the shielding gas, it’s just a crap shoot as to how it goes welding on random castings....
 
How large of a casting? If possible, you can try soaking it in a solvent to draw out the oil, then when you pull it out, blow it down with compressed air to evaporate most of the solvent, then heat it to get the rest hiding in the pores. This isn't going to get every bit of oil out, but should help. Also, aluminum takes a large heat input to start a puddle because it transfers heat so well, so I would take advantage of that and run my torch over my intended weld path an subsequent HAZ. The holes are probably due to rapid expansion of gas from the oil vaporizing and blowing the liquid aluminum away. By essentially "pre-heating" the weld site and HAZ, you get above the oils boiling point but stay below the aluminum melting point, keeping it solid and removing the volatile components without losing base material. The only thing that should remain are solids, which will still contaminate the weld (hopefully not enough to compromise it), but wont blow away aluminum.
 
Thats awesome. While typing my response, two others posted the same things at the same time, lol. I think you have your solution.
 
Thanks for all the replies. I have welded a fair amount of oil soaked castings over the years and can easily overcome problems related to this.

Things I have experienced honeycomb inclusion issues with are flywheel covers and most recently a brake plate. Neither of these is in contact with oil.

Welded an HD head once and there were problems with that, but apparently they use a lot of zinc and was able to overcome issues which must have been related to zinc coming to the surface of the weld pool.

Honeycomb inclusion problem isnt the same thing though and seems more related to whats detailed here: Defects/imperfections in welds - porosity - Job Knowledge 42

Thanks again for all the replies...............
 
I have to say, I'm surprised no one mentioned the method I use on dirty oil soaked aluminum.
Step one, degrease it with Brake cleaner or steam clean it... depending on the size.
I have heated things in my oven to about 400 degrees ( IE... BBQ )
I then prep my joint with a carbide deburr ( Dont use grinding wheels or sand blasting... they just add additional contamination ) on thin aluminum part I dont do any vee grooving.
Now that the part is prepped, I go over the part with my tig torch, not using any filler metal, I also run my amps a little lower than what I will eventually weld it at. Now that I have run my tig torch over the entire crack ( By the way, I make sure the machine is set for good cleaning ) the crack is going to be black, I then lightly run my carbide through the crack making it shiny, I then will run my tig torch over the crack again, ( Doing so pulls the contamination to the top ) I usually do this process 2 to 3 times, every pass seems to have a little less contamination than the time prior... , now it's ready to weld, I will now turn the machine up, grab some filler metal and weld the joint.
Please note: On thin parts I will usually use a stainless wire wheel on my die grinder to minimize removing to much of the material and forgo the carbide.
 
I am with old wrench. I have had the best results boiling castings in water and dish detergent. I have tried most of the other stuff mentioned with mixed results. If the parts are die cast its almost impossible to get a pretty weld because the metal quality is poor.
 
One problem is "aluminum" is not one alloy- its a family of dozens of different alloys.
Some of which weld better than others.
Older castings seldom had very good alloy control- they can vary widely, even in two parts that are "the same".
Some stuff, as mentioned, has zinc in it. Always a bad thing.

Good cleaning is essential, but, even with good cleaning, there are some aluminum parts that are just not weldable.
 
Service Rider, I've never boiled a casting, I'm curious how good that works..., tricks of the trade.

Ries..., the zinc stuff is pretty tough, I usually use a low melting R-1100 rod, this is what I call a, get in and get out type of rod, pretty much as soon as the rod melts in, let off, wait and then do it again.
 
I ilike cooking them well with preheat. That said, older aluminium especially if its been in the elements much can get a inter-granular corrosion going on and that causes agro, best is just run some beads and grind back, plenty of clean on the ac balance and to a degree it is what it is.

That said i have also encountered some lovely aluminium castings to weld that weld nicer than fresh bar, it realy is a crap shot.
 
I have to say, I'm surprised no one mentioned the method I use on dirty oil soaked aluminum.
Step one, degrease it with Brake cleaner or steam clean it... depending on the size.

Brake cleaner before welding can kill you if there are any little bits of it left in the pores. Fumes coming into contact with the arc can be just as bad.

Arc Welding 11: Cleaning material with brake cleaner before welding - The Fabricator

In some cases it was only one strong whiff.
 
Scruffy !!!! Thanks for that warning, yes, never use chlorinated brake cleaner to clean aluminum, if you use it, use non-chlorinated and make sure its thoroughly dry.
 
Had a vapor de-grease set up at the machine shop I worked at, don't know what exactly was in it but a guy put a motorcycle head in it and you could see the oil coming out of the aluminum. It wasn't set down in the solution but on a shelf above so it was the vapors that were actually doing the work.
It blew a head gasket and ate a trough out of the gasket surface that he wanted to fill with weld and then re-machine. The welder told him he had to use that de-grease method before he'd do it and it seemed to work out.
Dan

I know an environmental engineer who cleans up superfund sites and things like that. I remember them telling me about a site that had one of these machines and apparently whatever the vapor is plus the oil and grease had completely saturated the ground around the machine and it all had to be excavated and hauled away. Can't remember how many yards it was but it was significant. Sounded like real nasty stuff, I'm sure they work great though :D
 








 
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