cast aluminum

What are the options to welding cast aluminum? Is high freq mandatory for TIG here?

welding aluminum

nmaineron said:

What are the options to welding cast aluminum? Is high freq mandatory for TIG here?

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with aluminum and tig welding a high frequency is needed with sine wave AC to keep arc stable on old machines.
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new square wave welding machines often do not use or need a high freq because they switch the current so fast before arc would go out
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you can use a flux covered stick SMAW rod to stick weld aluminum or DC tig weld with it flux and all. the flux sticks strong to aluminum and is like glass. very hard to remove but hot water usually works or a powered wire wheel.
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alumiweld works like a brazing or solder rod
Aluminum repair kits, repair any aluminum metal by welding with a Propane Torch - Alumiweld
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i do not recommend spending $2000 - $4000 on a square wave welding machine and a heavy duty air cooled and water cooled tig torch for occasional welding. even if it takes 10 extra minutes to remove flux from aluminum stick welding rod weld , so what, you save thousands of dollars.

nmaineron said:

What are the options to welding cast aluminum? Is high freq mandatory for TIG here?

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What is it that needs welding?

Stick welding AL--let alone cast AL will be an adventure all by itself

Soldering AL leaves much to everything to be desired in the repair.

It just may be practical and economical to take the AL casting repair to
a shop that's actually set up to do such and has the requisite experience---as an option.

I have an old Harley transmission case that I need to have welded.

I have TIG just not HF. I am curious though,about using TIG with a flux rod! I will have to try it! Does any particular rod work better?

nmaineron said:

I have an old Harley transmission case that I need to have welded.

I have TIG just not HF. I am curious though,about using TIG with a flux rod! I will have to try it! Does any particular rod work better?

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You need AC with HF for tiggin' AL

If this is an experiment with tigging a case using coated AL stick rod--then go for it;
the results will be disappointing, the case trashed, the user...maybe a little wiser

If the case needs to be repaired and not scrapped--then it's 4043 and AC tig.
Most cases, including HD leave something to be desired in the casting quality,
which is dealt with by one who's actually done cases-prior and successfully.
IOW-case work isn't really a learner project.

I mig weld Harley cases all the time with 4043 wire. Some older Harley cases are the best cast that i have ever welded. My buddy just did a Honda case with the wire i gave him...Bob

Whilst case works supposedly not a learner project, 99% of my know how on tig came from watching you tube. Make sure its clean, preheat it with a torch (as much to burn off anything else as to preheat. I set the tig just like i do for aluminium normally just with a bit more clean (more time torch positive). Mines a inverter set and does not sustain Hf during ac welding, it simply changes polarity faster than the plasma arc can cool enough to no longer be plasma. Ergo the arc sustains does not go out, hence no hf to restart it!

Oh the cracked case i done came just fine customer paid, and i saw him a few weeks latter, holding fine not leaking. Heck he even polished it up darn nice. That was done with argon, ac, air cooled torch and one of em er new fangled blue electrodes. Never needed more than 150 amps :-)

As above though cast alu is some of the worst crappy stuff going to weld. That said some of it can be darn nice to weld too! all depends on what its soaked in and how good the casting + its silicone levels are.

Do your self a BIG favor. Take it to some one who knows what they are doing. Not trying to put a terd in your punch bowl but If you have never done it before or are even thinking about touching it with a mig welder you will only make it worst. The right person can do it right for a reasonable cost, if not it will cost three times as much to repair it properly after being monkey'd with ! Keep in mind that when you weld on cases they move around and distort. If you don't controll the warpage and preheat it properly you are looking at other problems down the road. Send it to me if you can't find anyone local that knows they they are doing, I do HD cases and trans cases weekly.

thanks for the replies,my attempt to broaden my horizons came up with a few ideas that I would never had thought of as a reliable fix for this problem!Hi Freq would be the only way that I would attempt this fix but at the time I didn't have Hi Freq available to me,now I do but my experience is in an industrial setting where cast aluminum wasn't something that came across the bench often.I have a few guinea pigs to practice on before I destroy the good case,which is really someones throw away cause it has a big crack in it, so...I have to make it right or find another victim :-) I will keep you posted as soon as I have figured out to make my new to me Hi Freq unit work!!

You can also use reverse polarity DC to weld aluminum... that's how they originally did aluminum heliarc welding, but using helium for the inert gas. I have done it and it works amazingly well. Only deal there is that on reverse polarity (DCEP) you are putting the heat to the torch instead of the work, so your duty cycle and torch amperage capacity is about cut in half.

Main thing when TIGing aluminum is CLEANLINESS. You absolutely MUST remove all ALL traces of oil and grease (tough on a part that is filled with oil). No traces of paint, no clearcoat, no little pocket of black goo in the corner. Any contamination will result in a black porous weld.

You must also scour the area to be welded with a STAINLESS steel brush to remove the oxide coating and scuff the brand new squeaky clean rod with scotchbrite, stainless steel wool or fine sandpaper to remove the oxide coating. The oxide melts at around 5000 degrees F, aluminum at 1100F. If the oxide isn't removed your work falls out on the table instead of laying a nice bead, as the aluminum melts out from under the oxide layer. Usually get a nasty black smoked up looking gob of weld, as well. Aluminum is not like steel in that impurities float to the surface. Aluminum oxides and other contaminates readily sink into the puddle, so if it starts looking bad, quit while you are ahead, grind out the crap and start over.

Wipe everything down with a clean rag soaked in isopropyl alcohol to remove fingerprints and any other trace oils before you start. Now, you need a pair of spotlessly clean TIG gloves, as any grease or oil on a pair of gloves will also ruin the weld.

When starting the weld, you can't put a glob of rod down and melt it in for the start like with steel. You HAVE to start a good puddle and then add filler. Putting down a glob gets you into the oxide problem and you get a black, porous weld at the start.

As you can see, your welding has to be almost surgically clean. Being very clean always helps with TIG, but it is absolutely essential with aluminum. Get all those things done right and aluminum is fun to weld. Don't, and your life will suck.

As mentioned above, cleanliness is of the utmost importance when welding any aluminum. The difficulty with old Harley transmission and primary cases is that they are often quite porous and will be full of oil. If you can get the oil out of them, you will probably have some luck.

Try baking it at 650 F. I've never tried it with aluminum, but it works great with oil soaked cast iron.

ChipHeadWayne said:

Try baking it at 650 F. I've never tried it with aluminum, but it works great with oil soaked cast iron.

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650 F---is waaaay to hot for cast AL....It's obvious that you have never tried it-as you admit.

Baking old Harley castings will bring the oil oout at around 350 degrees F. Problem is, it then turns to a dark crud. The cylinder heads are quite easily welded on outside areas such as exhaust ports. I've repaired numerous Panhead cylinder heads by adding new exhaust stubs. The early aluminum heads are almost pure aluminum and weld very nicely. The transmission cases and primary covers are usually pretty well soaked with oil.

What is needed would be a vapor degreaser with trichloroethylene. That would clean them up nicely but I don't think you can get trichlor much anymore since it's a Hazmat. not sure, but I think that's the case.

dave powelson said:

650 F---is waaaay to hot for cast AL....It's obvious that you have never tried it-as you admit.

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Thanks for clarifying - worked so good on CI, I just thought I'd throw it out there.

Newman109 said:

What is needed would be a vapor degreaser with trichloroethylene.

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I would be very careful using trichloroethylene and welding. Chlorinated solvents can create phosgene gas when welded. I'm not an expert but reading the article below made me think.
Brake Cleaner = Phosgene Article

ChipHeadWayne said:

Thanks for clarifying - worked so good on CI, I just thought I'd throw it out there.



I would be very careful using trichloroethylene and welding. Chlorinated solvents can create phosgene gas when welded. I'm not an expert but reading the article below made me think.
Brake Cleaner = Phosgene Article

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Of course, it's dangerous. It's not used very much anymore anyway. It does evarporate fairly well in any case. That said, it's No. 1 in eliminating grease and oil. We used it routinely when I was at Rocketdyne for cleaning parts to be used with liquid oxygen.

If you can get an industrial strength, water based degreaser ( Mobil used to have one in NZ , Mobilsol 77 from memory ), soak the parts for a day or so, rinse in hot soapy water and then " boil " the parts in a large pot with some detergent in the water. The heat opens the porosity and can help float the remaining oil/solvent out. Give the part some time in an oven around 200F to dry throughly, they are going get a preheat anyway, unless you are going the DC negative/helium route.

Getting back to this..thanks for all the replys,lots of knowledge...curious though..why helium over argon for DC negative?

Helium is better because it makes a more focused hotter arc. Works just as well - better on a Ac modern inverter too, but is excessively costly in practice!

A dishwasher can do a pritty good job on casting clean up too! The ones i really hate are those some one has already tried something like a epoxy resin to repair, there a frigging nightmare to get clean!

I have done a lot of cast aluminum repairs for parts on formula ford cars and similar race cars.
The part that holds the wheel bearing is called an upright and they get broken all the time.

The problem with these is the castings are not always the greatest quality and they are constanty exposed to grease which can find its way into the casting.

Cleaning is important, gouging out the crack large enough to fill is also important. This will significantly soften the aluminum where ever the weld so depending on where the damage is you might want to heat treat this piece. If you do need to heat treat you will want to use a filler rod that responds to heat treating similar to the casting.

Perhaps someone else can chime in as my memory is a bit fuzzy but there are two alloys that come to mind, A356 and 5356.
One is for heat treating purposes and the other is better for welding disimilar alloys together, such as needing to weld a 6061 sleeve into a cast upright that will no longer hold a wheel bearing as it should. Which is which I can not remember at the moment.

On dirty castings some times baking will not get the oils and contaminates out. In this case you will be doing a lot of gouging and welding, gouging the weld back out and welding again and again until you get a clean repair weld. This can result in a lot of time and perhaps even heat treating a peice that had it been a clean casting would not have needed the process if you could only have welded for a short time.

An upright holding a wheel bearing has to deal with a lot of forces and that is before there is even a crash. Your part might be just to cover some gears and may not need heat treating, good luck with that. Remember not all castings are the same, some of them weld up with no problems and some have contamination through out the material making it a nightmare.