Tig Welding Cast Aluminum

     There seems to be a stigma around the word "cast" when it comes to welding repairs. When people hear "cast" they think, "Crap, it has to be preheated, welded with a special rod, peened, posted heated and cooled in a particular way". While that is true with cast iron, castings can be made with any material, aluminum, stainless, brass, steel, etc. Iron can be difficult to weld regardless of its form because of the high amount of carbon.
      Here I'm going to walk you through an aluminum repair that seems pretty common.The mounting ear on this TH-350 has snapped off and needs to be built back up and then match drilled. I have no idea what grade these transmission cases are made of but I haven't run across a trans case that is impossible to weld.

You can see there should be a little more flange here, oops.

Perhaps the most important step, the case was ground clean with a grinding wheel dedicated to aluminum then brushed with a stainless brush then wiped down with acetone. NO BRAKE CLEANER! I cleaned about a two inch perimeter so the dirty aluminum wont bleed into the clean stuff.

I cut a piece of .25"x1"  6061 aluminum bar to back the welds and provide good starter to absorb some of the heat.

No preheat required here, it was welded with a transformer based machine on AC, continuous high frequency. Somewhere around 130 amps, it welded great with 5356 filler rod. I use 5356 over 4043 because its less sensitive to contamination and has a harder face.

More is more in this situation. The customer will grind the flange flat and match drill the housing.

Voila. Its not a beauty queen but its better than digging through the yard for a good case.

      If you have any questions, comments or concerns let me know with the comment link.