Generally speaking in the world of sheetmetal shaping, it is now believed that low-carbon steel really does not "work harden" per se' to any appreciable standards where you would ever notice it. Granted, Mild Steel can be hardened (somewhat) if carborized, but generally speaking in the world of mediablasting, if the metal has been that hot due to the media friction, then the warpage is going to be the bigger issue.