Hi All,
I need to TIG weld inside a recess in an aluminum casting. The recess formerly held a plain bearing. The recess is approx 1" diameter and 1.200" deep. A crack formed in the wall of the recess, then the bearing fragged, and that created a gouge. This looks to be the result of abuse, rather than a flaw in the casting. It wouldn't be a difficult job to repair if not for the difficulty in getting to the lower part of the crack. Unfortunately I can't get at the backside of the recess, or I'd gouge the crack out and weld it that way. I do have enough room to get in there with a carbide burr to gouge the crack on the inside, using a burr with an extended shank.
It looks like the only way I can get in there is to use a torch without the cup, and extend the tungsten roughly 3/4" or so. Due to the thickness of the aluminum, I'll have to use ~140A or so, even after preheating the part. My idea is to create a dam around the recess using a short length of some 2.5" steel tube I have handy, then flood the area inside the dam with argon. I have a dial-indicator stand with a gas lens & large cup, I will use that to apply the gas. After a moment or to for the argon to displace the air, I'd insert the torch to do the weld. Naturally I'll do this in the most draft-free spot I can find. When I'm done with the weld I will bore the recess to the correct size using the mill.
This seems like it will work, but the piece I'll be welding is not one that I'd want to screw up. (At this point, it's scrap anyway, but still...) A new casting is > $600, so it's worth taking the time to do this right. Too bad I don't have access to a proper purge chamber - but, I'd consider making something temporary, if that's the best way to go at this. I thought I'd float this idea to the group, to see if it seems plausible, or if there is another way to approach this kind of problem. Thanks for any info or suggestions.
G.