Recommendation? How to D2 below 62 hrc ?

[YorKnife]

Hey
I’m a British maker trying my hand at D2, normally I use 80crv2 but for this next project wanted D2.

Anyway I used the recipe on this forum that’s pretty much universally recommended, but I can’t get my final reading below 62 rockwell? I’m looking for the 60 mark for a little neck knife I plan on making a run of around 20.

Any way the process I’m following is below

Heat kiln (paragon km24) to 1800f and let it settle for a few minutes, put the foil wrapped token in, ramp to 1877f (1025c) for 40 minutes. EDIT I realised when I was double checking the F to C that I should of been hardening at 1825f/995c tiredness plus rum plus calculator = days of wasted testing ‍

Pull token out and place h between 1.5” aluminium plates and blow with compressor air until luke warm, bring down further in water.

put in liquid nitrogen dewar for 1 hour, then remove and bring to room temp, once able to handle in bare hand (room temp) go to temper in oven

Oven tempered twice at 230c (446f) degrees for 1 hour, remove and place on aluminium plates then repeat for second temper at 230c (446f)

I then throw it on my surface grinder to take away the decarb and test it on the Wilson tester.... this is where it gets interesting as I can’t get it below 62 Rockwell! I’ve done several rounds of testing by changing the temper heats from 230c (446f) 250c (482f) 300c (572f) and 425c (797f) and it remains the same?
last night I’ve even lowered the hardening temp to 1005c (1841f) as I thought that might lower the final outcome of 62 but it came out the same with cryo and two tempers at 230c

Thought my Rockwell tester was faulty so just thrown some 80crv2 on it that I tested a while back at 59.5 and it came out at.... 59.5 so I know that isn’t the problem

What the hell am I doing wrong lol why won’t it soften down to the 60ish mark?

thanks in advance
Luke

 

[Stacy E. Apelt - Bladesmith]

One thing I see is your temper. It should completely cool to room temperature between tempers. Not sure what the "baking on aluminum plates" was about.

Raising the austenitization point a bit will lower the final hardness, so try 1035C or 1040C and see what the outcome is.
Or
Temper at a higher temperature. Try 240C or 250C.

 

[YorKnife]

Thanks for the input, predictive text as away from the laptop, Corrected.

the tokens are all cool before I move to the next stage, I often dunk it in water once it’s cool to the touch to bring it down cooler than room temp.

i didn’t realise raising the hardening Initial temperature would lower the final Rockwell count, so thanks I appreciate that nudge in the right direction

I added a pic of what I’m making to make it more interesting as it was longer than I thought it would be lol

thanks
Luke

EDIT while double checking my temps and the conversion for c to f I realised I might of made a booboo and wasted days of heat treat testing ‍ As my hardening temp is actually 1877 not 1825?