d-2 h.t. question

JB Knives

JB Knives

Joined
Apr 18, 2007
Messages
327
I just spent two days cursing at this piece, but it's finally finished.
Before I send it to the great Mr. Bos to have it heat treated, I was wondering what the best hardness was for a blade this size.
Normally, I have my d-2 blades hardened to 59-61rc-however, all of my blades until now have been 10 inches or under. This monstrosity measures 18 1/4" long by 1 1/2" wide, and is make of 1/8" thick d-2 tool steel.
I was unsure if I should harden this (big knife? Short sword?) to my
usual hardness, or if I should harden it around the 57-59rc range to allow the long blade a little flex- I am not sure how much of an issue this is w/ d-2, but better safe than sorry! Pic posted below if they are of any help. Thanks!
bigun.jpg
 
Hey there JB! D-2 is a very tough steel. But not a pry bar. If used with respect, it will be fine at either Rc. what worries me is the holes in the blade. These cause stress risers. They may look racy, cool but Will cause more problems that Rc.ever will. Even if there is no micro cracks started in any of them during heat treat, they will act like a notch cut into a tree limb when bent. They are almost guaranteed to fail. Mike
 
Camfer (bad spelling) the holes before HT. I try to end up at about HRc 60 - 61 on D2. I believe the data sheets specify good toughness there. Temper well.

rlinger
------
 
It's chamfer , Roger !.. I agree that holes are not a good idea and chamfer will reduce the problem a bit....Flex is dependent on thickness not hardness.
 
Not trying to pee in your pool, but you have more cussin' at this blade to come. When I looked at the photo the first thing I saw was those holes. Then I read the specs and saw 1/8" and 18" long. Sorry to say, but this will have to be a wall hanger. If it survives HT it will surely fail in any field use. As the others said, chamfer (round the edges) of the holes....that will help it survive HT, but a blade this thin in D-2 will very likely break at any lateral stress where those holes are.
Sorry - Stacy
 
Well, the literature shows the highest toughness for D2 around a 500 deg temper, which I believe equates to around 62 hrc (with cryo). That is hard D2, but also the highest published toughness, so it is a nice sweet spot. I've cut nails with it at that hardness.

I broke an A2 machete yesterday. It failed at a stress riser on the first whack on something over an inch. I'd tempered (two times for two hours) at 515, the "toughness peak". It was around 60 hrc. In retrospect, perhaps I should have run it down to the mid to low 50s where the toughness is coming back up again. D2 doesn't come back up again, it just keeps going down at softer tempers. IMO D2 at soft temper sort of defeats the purpose of D2, and at hard temper, on a long thin blade subject to impact, I suspect it may fail on the first good whack.

I love D2 on pocket knives.
 
Thanks for all the great answers, everyone. This piece was, in fact, just "for show"- it is a larger version of one of my small dagger designs, and I thought it would get a lot of looks. The d-2 steel was simply handy, and I was desperate for something to do while my blades are being heat treated. As long as it will hold an edge and survive the occasional fall, I will be happy! I was thinking of making a few other large knives out of D-2 (without the holes, of course- I use them in all my smaller knives, but I imagine it doesn't work so well with blades of this length, which everyone has now confirmed). Thanks to everyone's advice, I now know that a different steel may be a better choice for my long blades- perhaps A-2( my favorite) or O-1 would be better?
 
Nothing wrong with D-2 at all. It is a fantastic steel. I'm afraid that folks confuse toughness with shear strength. Toughness is what keeps the edge from rolling over. This is reached at high hardness. Shear strength however is what you are wanting for impact strength. (Not denting the edge, but rather not having half or the blade go ringing off in the air). This is reached at higher draw temps. You want a lower Rc. Here. 55-56 is good. I like 56-57 for a battle blade in D-2. 60-61 for a fighter, or hunter. I have a prototype hunter that I made for Ted Nugent back in the early 90's. The blade is only 3/32 thick, and ground like a straight razor. While preforming a flex test in the vice, the edge broke. It now has a 1/4 inch crack running from the edge up toward the spine. I still use it for deer hunting. Now thats shear strength. It is 60-61 Rc. Mike
 
You must log in or register to reply here.
Back
Top