Heat treat for D2 dive knife

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sealpup

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Apr 27, 2013
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I've recently began dive school, and I want to forge my own dive knife (not my first knife, I have previously been taught by Chris Moss). Chis has advised me to use D2 tool steel for the blade, since it has good resistance to rust (most commercially available dive knives are made from stainless or titanium, neither of which I feel comfortable working with). Chris has never actually needed to use D2, so besides telling me that it is an air hardening steel, He couldn't give me much advise on the heat treat.

I've done some research online, and these are the questions that I still have. Unless otherwise stated, they all are in relation to heat treating.

First, I've seen that the temperature I should heat it to is around 1800-2000 degrees. Great, I don't have a thermometer capable of reading that. What color am I looking for? Should it be about the same as most tool steels?

Second, I've heard of people actually wrapping the blade in foil to help keep it from oxidizing. This seems kinda ridiculous to me, partly because I would assume that the foil would melt off in the forge, and partly because it seems unnecessary. All my other knives oxidize, I just sand it right off. Is there some reason why I actually need to do this?

Third, I've also heard of laying the blade between two large pieces of metal to help it cool faster. I really don't know what to think of this, except that it would result in uneven cooling.

Anyway, What are your thoughts?
 
I would suggest stock removal using stainless, then sending it out for heat treat, after which continue doing research, the answers to all your questions will start to become clear after 50 or 60 hours of reading ;0)
 
I disagree with using D2 for a variety of reasons, mostly because it isn't a true stainless steel, hence it will require MUCH more attention.

Diving knives get BRUTALLY abused so strength would be more important then edge-holding ability IMHO and incorporating a well designed, and decent length, serrated edge would be another consideration to keep in mind. Once upon a time I made a 2' diver's crowbar with a 7" blade incorporated under a screw on handle (much more a tool then a weapon or cutting instrument). I made a call and asked the guy who I thought still owned it if he'd take a pic and send it to me. Alas he lost it some years ago. Mysteriously..................... Imagine my surprise at a goodie like that disappearing.

Just a couple of my thoughts for you to consider.

Corey "synthesist" Gimbel
 
D2 would not be my first choice for a dive knife.

D2 isn't stainless, and salt water will rust just about anything.

I would go with the most stain resistant steel that I could find.
 
Greetings,

D2 is some of the best knife steel out there. If you take good care of your equipment like most divers do... D2 would be a good choice.
As far as heat treating... sending it out is a good idea, but it can be done with good results. Heat the steel until a magnet will not stick... about 1800deg. Soak the piece for about 15+ min. When you remove it you have a couple of options, air cooling or plate cooling, a little reading will show you what that is. If you wish to reduce the amount of decarb... you can invest is heat treating foil... made from stainless steel... if you choose to air quench... find a location where there is little or no air movement... to temper evenly. As soon as the piece has cooled, put it in a oven at 450deg for 1 hour for a 58-60 hardness.

There is a lot of science to tempering, and because of the cost of the equipment it is cost effective to send it out for heat treating.

I recommend practicing on a scrap or two first... When I try a new steel I will grind an edge on a piece, harden and temper it, then test it...

The test I use on D2, 5160, S90V... is to cut a 1/2 bolt with the blade and a hammer... I don't do this with every blade, only when I temper the first time.

Good luck... and remember, it you don't try it, you haven't learned anything.
 
Dive knives are perhaps the best example of the old "sharpened pry bar" in that they are actually supposed to be. well, a sharpened pry bar. One steel that is apparently popular now for such use is H1 which, by all accounts is only moderately suitable as a fine cutting steel but it basically just won't rust. With a dive knife, you are talking about submerging the blade not sweater for extended periods of time.
 
Way more experienced makers have given very good advice, I would heed their advice. I do not think that D2 would be a very good choice for a dive knife. My own research concerning such a knife leads me to steels like Z-FiNit Nitrogen Stainless Steel or 14C28N (if it can be found in 5/32, AKS had some in that size but not currently). Both of those stainless steels have Nitrogen added to aid in corrosion resistance, specifically salt corrosion IIRC. Not all corrosion is the same and different steels are more or less resistant to different corrosive agents.
 
+1 on the Z-FiNit. Spyderco is re-introducing their Aqua salt in H1 and it would make a great little dive knife.
 
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