I always meet the problem about hardening 4140 steel at my work. I used to induction or flame harden 4140 heat treaded and stress released (HTSR) steel to HRC 54-56 but someone told me I should use 4140 annealed steel because if I use pre-hardened material, I need anneal it first and then re-harden it. I knew that the core of annealed 4140 likes mild steel, which is not I wanted. My past experience also told me that it does not need to anneal 4140 preharden steel before re-hardening. I am looking for suggeston that what is the adventage and what is application for hardening each material. Thanks for you help.