I am having problems achieving full hardness from 4340 bar stock from full anneal. I can achieve full hardness from a part as machined (normalized and tempered-orinally 30 HRC) to 55 HRC. However, I then fully annealed the part (to about 10 HRC)and when I went to re-harden I could not achieve higher than 35 HRC, even after 3 tries, 2 at 30 minutes and again at 60 minutes. My hardening is at 1525F and oil quenching. Any ideas?
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