Bodywork - Annealing / Tempering sheet metal?
 

I'm doing rocker repair work and have cut out the entire right rocker. As part of the work, I've cut out rot inside of the rocker, within the wheel arches and about 1' of pinch weld from each wheel. While the structural "O" beam is in great shape, some of the sheetmetal between the O beam and floor pan are rotted.

I am replacing the rot with new metal. I believe these are stressed areas - should I temper them to the best of my ability? (IE heat with torch ~1 minute, spray down with water after welding) or should I just epoxy right after welding? Not sure if spot welding in panels even gets these panels hot enough to truely anneal as I am being careful to stitch around each panel I put in to avoid burn-through. All I know is, I replaced a portion of the inner rear wheel arch, and there's definitely more flexibility after I put in the replacement stock.

Learning as I go here, any advice will be much appreciated.

afaik, automotive sheet metal is low carbon and will not appreciably harden. Joints crack at welds because the weld is harder than the panels being joined, with that in mind, I would think that it would be better to anneal after wielding. in theory this would reduce cracking at the weld. in aviation, we aneal tubing after welding however, we use 4130 steel which is higher in carbon than automotive grade steel. by cooling the metal quickly with water, one would be doing the opposite. so to anneal, heat and let cool in free air. hope this helps.