I've seen the topic of hardening/tempering of metal come up here from time to time. There is an outstanding reference on this subject for knife makers who use a variety of high-carbon and stainless metals for knives and it could apply to DIY lock pick makers.
This document is over 200 pages long and was written by a University of Iowa professor and expert on materials. If you want to know about metal, how to heat treat, how to quench, and how to temper then this is what you want to read:
http://www.hybridburners.com/documents/verhoeven.pdf
Enjoy...
