Color casehardening is a carburizing process wherein carbon is introduced to the outer layers of the steel in order to harden the skin of the part. In this process the carbon is pulled from the charcoal pack via heat and is trapped by the subsequent quench. Carbon must be present in order for steel to harden.
To properly "re-case" a part, the previous hardening process must be "undone" via the controlled annealing process. I used to
work in a very well known shop that specializes in casehardening and we NEVER re-cased a part w/o first annealing it.
Warpage in my experience relates more to the design of the action, trigger plate, etc. L.C. Smiths, Parker's and others rarely had warpage issues because the frames and other parts were thick where they needed to be and could usually be reassembled w/o hard fitting. Every Ithaca Flues that I have
re-cased required hard fitting. The tangs and trigger plates on the Flues always move because they are thin and just tend to warp due to the heat. It just takes a little time and experience to hard fit re-cased parts back to where they need to be for final assembly.
Dan May
