Craig,
You generally try and match your weld metal to the parent metal as closely as possible but when it is that old you may be out of luck in identifying the parent metal.
Your safest bet would be a nice new pack of 7018 stick electrodes and build it up with those.Don't forget your preheat.
There will quite possibly be others on the forum who have more experience with these machines and hopefully they can provide more information,
Regards,
Shane
Hi Craig, I agree with the good reccomendations above and have repaired several Champion grader rings. We built up the worn areas with mig or stick & 7018. We were also able to cut out and replace badly worn sections with a section about a foot long ( supplied by the local dealer ), although this seemed to take as much time as just building them up with mig. Then we would lay a template on top & grind off the excess weld ( oh what fun ). A few final touch ups with 7018 and the thing was good to go. We did'nt get too fussey, after all there is considerable tolerance with the mating teeth. I suppose a final layer of impact resistant material would improve the longivity of the repaired teeth, but in our case we did'nt use any. Hope this helped out some. - WS