Welding Cast Aluminum

[JodysTransmissions]

What is the best method to weld your typical Muncie or BW ST-10 cast aluminum case.

Thanks, Jody

[parsonsj]

Clean, clean, and clean some more. And don't get all upset if the bead rolls around a bit: it just won't look at good as welding sheet or structural aluminum.

TIG, of course. It will take lots of heat, so do what you can to minimize warping. Use a 2% thoriated tungsten, and sharpen it regularly (like every few inches).

I'm sure Matt can give more technical data ... perhaps he will have a moment between rushing around for SEMA.

jp

[Matt@RFR]

There's not a whole lot of tech for this subject aside from what John said. The only trick I know of is pre-heating to keep localised warping to a minimum (and to help it from cracking as it cools), and to run a very cold arc over the joint several times to let the AC clean the joint before running your first weld attempt.

Be prepared to weld it up to 3 times before the weld is clean.

Do NOT use grinding tools to prep the joint. All you'll do is smear the aluminum and work all the dirt/grease into the poors of the aluminum even further than they allready were. Use carbide burrs in a die grinder, a mill, or similar tools.

Cool the entire thing down slowly, and it'll be fine.

It would be nice to find out what alloy the casting is, but I doubt you'll be able to. Use 4043...it's generally used as the filler for unkown casting alloys.

If you know how to weld cast iron, this is basically the same thing.

[JodysTransmissions]

John & Matt,

Thanks for the replies.

Regards, Jody

[SShep71]

If Imay I have to add a thing or two.
Matt is right if you know how to weld cast iron you can weld cast Al. If your Tig setup has a wave balance feature set it to max clean for the first pass, then switch it to 3/4 max penetration. If the area is cracked first drill a 1/8" hole about 1/8" past the end of the crack. After you drill the hole v-notch the cracked area with a die grinder and carbide or a notching tool. Then run a small bead about 1" long perpendicular to the crack. This does 2 things: It helps to preheat the parent metal and it aids in the elongation/prevention of cracks. Try to preheat the casting from 175-250°f, and post heat the casting to relieve any stress. One more thing I can suggest is that if you are having trouble welding the casting try using DC reverse polarity with Helium as the shielding gas; its maily used when padding a surface but it has excellent penetration as well as a high feedrate. Good Luck!!

[JodysTransmissions]

What tungsten size, 3/32? filler rod diameter?

Thanks, Jody

[parsonsj]

Yes, 3/32. Either 3/32 or 1/16 filler.

jp

[Tig Man]

Makes a big difference as well as using a mixed gas of 75% Helium 25% argon!! It makes a ton of difference in welding nasty cast aluminum such as cylinder heads and intake manifolds!! Pure tungsten is the only thing to use!!


Mark

[JodysTransmissions]

Use a 2% thoriated tungsten, and sharpen it regularly (like every few inches).

jp

John,

I sometimes weld 6061 aluminum and use a pure (green) tungsten with a small ball form on the end.

By your statement, are you grinding your tungsten to a point as if you were welding stainless? Is 2% tungsten brown? I am colorblind!

Thanks, Jody

[SShep71]

Only use pure (green) tungsten. No matter what you do sharpened or not a ball will develop at the end of the tungsten, its from the negative side of the wave where the electricty flows from the work to the tungsten. If you sharpen the tungsten a small ball will develop and will aid in arc control. 2% is red, sometimes it looks maroon.

[Matt@RFR]

Only use pure (green) tungsten.

I beg to differ. Pure tungsten sucks! That big ol' ball that forms on the end basically lets the arc do whatever it damn well pleases, which usually means it will be atracted to the side of the joint you don't want it to be on. (Murphy's law)

Even with a transformer machine, alloyed tungsten can be used. It'll stay pointed for awhile, depending on where you are in the amperage range for the diamter electrode you're using, but re-grinding is too easy to not use alloyed tungsten. You get the same arc but with directional control.

Now, if you happen to be using an inverter machine (welcome to the 21st century!), depending on your AC balance setting, alloyed tungsten will stay pointed for as long as it does in DC.

Thoriated tungsten is actually on the bottom of the food chain, just above pure tungsten. Zirconiated and Ceriated are among the better alloys, and only you can determine which you should use. Talk to 5 guys, and you'll get 5 different answers as to which alloy to use, and all 5 are correct. My personal favorite is Ceriated, and it's all I have in my shop. Next up for me to try is 1 1/2% German Rare Earth alloy.

EDIT: I should clarify that the above is only my opinion, although I don't know any TIG weldors that use pure OR 2% Thoriated tungsten.

[parsonsj]

I use 2% thoriated tungsten. I sharpen it just like steel and stainless. It makes a big difference with getting the arc to go where you want it. You will have to sharpen it a lot more often, but it definitely helps a lot. I NEVER use pure tungsten anymore.

jp

[JodysTransmissions]

Thanks for the tips guys, I will take a few transmission castings the are damaged beyond repair and practice. I will try everybodys suggestions and see what works best for me.

THANK YOU All.

Regards, Jody