Hmmmm, heating that metal is not gonna expand or stretch the metal out, its gonna do the exact opposite, its gonna contract or shrink.
Spot heating metal DOES NOT CAUSE THE METAL TO EXPAND IT SHRINKS!!!!!
Besides you wont see any real difference if you anneal it,plus the annealing process takes more then just a simple heating. Not worth the time and effort.
Try reading this. You ARE dealing with the same exact principles...Eric
http://www.chevelles.com/forums/showthread.php?t=333455