Calling the D2 gurus! Heat treating D2 steel for maximum toughness as a tool?

Daniel Fairly Knives

Daniel Fairly Knives

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I'm making some D2 steel keychain tools and am wondering what you guys think I should do for heat treat, especially tempering.

The tools will be 1/8" thick D2 steel and feature a bottle opener, shackle opener and a screwdriver/pry tool.

I have heat treated D2 before but never for a tool without an edge, only knives.

I have 2 digitally controlled kilns and use plates for quench. Sometimes I do a sub zero with dry ice/denatured alcohol after a snap temper and the first temper cycle when HT'ing D2. I do a very standard heat treat.

So, what would be the best temper temperature considering the pry tool/screwdriver end? I have my thoughts but would like you guys to help out!
 
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Here's the design


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Heat to 1750F and quench in oil until it looses all red color ( black heat). Then air cool to room temp.
Clean up, but avoid any stress or shock.
Pack in foil.
Heat slowly to 1500F and then ramp quickly to 1850F. Hold for 15 minutes.
Plate quench or air quench. ( I think air will be fine. Just slit open the packet and dump out the tools on a big bar/sheet of aluminum)
Snap temper at 300F for 30 minutes, and then do a sub-zero or cryo.
Temper at 1000F for one hour, twice.

The pre-quench will give finer grain. The high end temper will give maximum toughness. The final Rc should be in the low to mid 50's.
 
Thanks Stacy!

Great information there, I really appreciate the help.

I am getting different information on secondary tempering temps but I understand I should likely be aiming for a lower RC than for blades.
 
1825 austenitizing temp hold @ temperature for 30-45 mins. Good fast quench between plates then double temper @ 500 degrees F for two hours per temper.
 
I would use that for a knife blade , but for a tool used to apply torque and prying, the secondary tempering range will provide maximum toughness. The regimen you proscribed would be a bit harder than I would want in a simple tool.
 
I could be mistaken, but I believe that for D2, the maximum impact toughness is frequently given at a 500 deg temper (surprisingly low. perhaps due to the typical RA and reduced carbide precipitation), but maximum torsional toughness is more like 800-900. So I would lean towards the higher tempers for this application.

The prequench Stacy speaks of is a pretty cool (and not frequently mentioned) tweak you can do with D2. However I'll warn you that a low vanadium D2 may not behave like the high vanadium D2 that research was based upon, so you might want to try it first before doing the entire batch. Double austenitization with D2 can lead to trouble, depending on the internal condition and chemistry.
 
Thanks, Nathan.

I was going on the torsion and other stresses that a tool like this will encounter.
I have seen very few people mention the pre-quench for D2. Most standard knife D2 alloys ( Crucible, Aldo) have the vanadium, IIRC.

It is similar to the grain refinement cycling done on hyper-eutectoid steels. It produces a fine grain that acts as a nucleus for a fine grain structure in the second quench. The second quench is at an austenitization temp that assures full hardness. The higher level temper assures full resistance to tearing on the grain boundaries ( torsional strength). The combo makes for a tough tool used for prying or twisting.
 
Thanks guys, this is very helpful.

I'm going to see what the specs are on the D2 when I get it, I think it is usually made by Boehler but I am not too sure about this order.
 
I have a bunch of the Boehler K110 D2 and it is great stuff. Mine has something like .95% Vanadium. They say it is also cross roll it and the grain is well controlled in the mill.
 
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