METE - Tempering D2

Mar 29, 2002

I ran across a tech note suggesting D2 should not be tempered lower than 900 - 960 F. The sheet's accompaning table indicates it secondary hardening at that tempering range (targeting 58 - 60 HRc); as the tempering goes from 400 F to 900 F the hardness drops and comes back up at about 900 F. I have been tempering D2 at about 400 F, targeting about 60 - 61 HRc. Can you advise about this and suggest it better not for our D2 knife blades be tempered at the lower ranges or are we okay at tempering lower than 900 F??


D2 exhibits secondary hardening especially at higher hardening temperatures. The higher hardening temperatures of course produce more retained austenite.I wouldn't go above 1850 F for hardening and at that point secondary hardening is not that significant .Stick to the 1850 and 400F.
Thanks Mete. I do have a slight difficulty in sticking strictly with 1850 F on long blades because of my furnace depth. Beyond the thermocouple, toward back of furnace I am a little high (about 25 F). For long D2 I have been setting the control for 1840 F, expecting about 1865 F at tip of blade.

Thanks for the 400 F tempering being okay, and I presume on D2 we should still aim for 60 -61 HRc for best toughness(????).

400-600F gives you the best toughness so pick whatever hardness you want in that range.