Welding Pot Metal

Sure, I Can Do That

My buddy John called me up and said "My edger broke. Can you weld the bracket back up?" Sure, I've been doing a bunch of mig welding lately, so I'm current. Bring it by and I can zap it back together. So he brings it by, and it really doesn't look like steel. It's all porous, and a magnet won't stick to it, and I start thinking "pot metal".

I know I can't use the mig welder, but maybe I can braze it up somehow. My acetylene bottle is empty, (make sure you turn off the valve every time), so we head over to Praxair. It's about ten blocks away. I swap the bottles, and then I ask Steve what he thinks the metal is, and what kind of rod I should use. He puts some kind of test chemical on it, and says that it's aluminum pot metal, not magnesium. We should use aluminum rods, but he only sells them by the box, and they're $40/box. I think I have one left at home, but I'm not sure. On the way out he slips me one. What a guy! Support your local welding supply store.

Let's Do This Thing

Back at the carport we get set up. John cleans the bracket with acetone, and then I bevel it with a grinder. We get it clamped together and braced with fire brick. I've used these rods before, and I remember the tough part is getting the rod to wet the parent metal. The aluminum rod is hollow, with flux inside, like flux core mig wire.

I fired up the torch, and proceded to destroy the bracket. The metal would just start to turn silvery, and then it would slump away. I kept trying to fill in with the rod, but it wouldn't flow into the pot metal. When I was all done and took the clamps off, it held together, but I didn't have a good feeling. That's why I took these pictures before we tried it out.


Oops

Is that ugly, or what? Anyway, we stuck it back on the edger, and it made it almost 20 feet before it broke off. John's going to try to find another bracket at the lawn mower repair shop. What annoys me about all this is that my tig machine is at Chris's shop. I'm waiting for him to get 220 service out there, then I'll have a big space to work in. I think I would have had better luck tig brazing this. Certainly I would have had more control.