tig welding cast aluminum

By gouldmotorsport Date 03-22-2007 21:54

I am having problems welding cast aluminum on a transmission case. I think I am using to small a tungsten rod. The end of the tungsten seems to ball and then start to drip. I am currently using a 3/32 puretung rod, with a size 8 alumina nozzle. As a filler material I am using a 3/32 1100 rod. I have a miller syncrowave 250 machine with water cooled torch. Also it seems like a lot of impurities are coming out of the metal as I weld. I do not have a lot of experience with this application and any machine settings or consumable advice would be greatly appreciated. Please go easy on me as I am not a professional welder, and have been out of welding school for many years. Also any tips on cleaning aluminum would be very helpful. I currently use a stainless brush and a chemical cleaner for stainless that the local welding store suggested. Thanks for all the great advise in advance. Dave

By rebekah (**)

Date 03-23-2007 12:32

Yo Motorsport

I am no expert and have only welded cast AL once but if this helps...

Most likely the metal is impregnated with crap and it is going to put out crud when you weld it no matter how much you scrub it. If you are just patching a hole--which was my experience--it wont matter.

Sounds like too small a tungston for the setting you have it on. You can use a larger pure tungston, change to a ceriated or zirconiated tungston which hold the heat better (there are some other posts about that on the forum) or turn down your machine and add Helium which makes it hotter. I play around with these options when I am welding until I find the right combination.

Consumable wise--havent the faintest about cast and cant remeber what I used but you can always search the net for more info.

Hope this helps. Cant stand to see an unanswered question hanging in the breeze, expecially one that is probably bike related. My experience with cast AL is from patching a hole on the cover of the head of my BMW but I weld aluminum for a living.

Best

By MDG Custom Weld (***)

Date 03-23-2007 13:52

We have done a few of these, the older ford trucks always seem to break the ears off. As with anyhting cast, it is very prone to having porus surface and be full of oil and such. I always heat the area up with Oxy-fuel to 150-200F. You will be amazed of the oil that boils out at that temp!! Now that it's hot and the oil has burned away to just a residue, wire brush the heck out of it. Now weld it. It will flow like crap until you get enough good alloy into cast to make the arc stable. It usually takes all of 225-250 amps. I think your Miller can get the job done, but you do need a larger tungsten to run that amperage.

By rebekah (**)

Date 03-23-2007 14:06

Is this one of those areas where peening the weld helps to set it into the material?

By Kix

Date 03-23-2007 14:17

Ok do like what was said above and heat it pretty good to around 200deg+ this is to help keep the ceriated tungsten from balling to badly when i tell you to turn your A/C balance down to around 3 or 30% or 4 or 40% and to burn some of the crap out. Switch to a 1/8 ceriated tunsten and clean the heck of the part. When you see the crap starting to come up in the metal and the porosity stop and pump the pedal to let it come to the surface. Come allmost out of the arc and then back in it again at the same time adding your filler. You should also use a dremel and bevel the crack slightly or to prep the hole you may be fixing. This works pretty good for all the harley heads and car heads i've fixed. O yeah if you are trying to do this with the cases still together it's probablt not going to work very well. You must have the cases split and be able to weld from both sides if you are fixing a hole or crack. If your just fixing a bracket then this should be an easy job! Good luck and hope this helps.

By 357max

Date 03-23-2007 14:31

Boil the aluminum in a pot/tank/barrel (ol' beer keg) big enough to hold the disassembled case. Fill with clean water and heat with a large heat source. 100# tank of propane and a "Tiger"/brush burner torch will work. Boil and skim off the oil/debris that floats to the surface. Continue to add fresh water and keep boiling until the water boils clean. Use a "Scotch Brite" pad to clean oxide and then wipe all (back side/front side and root/groove faces) surfaces with acetone soaked rags (dispose properly & safely).
Use a sharpened (1/2 - 1 1/2 X Diameter) 1/8" ceriated tungsten (don't use EWP Pure with square wave), don't ball the tungsten. If it balls (like cherry stabbed on a toothpick), use a sharpened 5/32" tungsten. Set the Syncrowave to max penetration (68% time at negative). Set the amperage.

By gouldmotorsport Date 03-23-2007 17:02

Just wanted to thank everyone for all of your advice. I will try these procedures and let you know how I make out. Thanks again.....