I welded the hub of one of my wheels about a year and 1000 miles ago....seems OK...I welded it on the inside....at the same time I also welded one of the spokes back onto the rim......if you weld on the rim,take the tire and tube off!
I've drilled a hole where the spoke broke loose from the hub or rim, then welded the spoke from the backside. This will leave the spoke attachment neat as original, and when the weld cools it will pull the spoke tight.