Appropriate Rockwell for D2 fixed blade?

S

SterlingHammer

Joined
Jul 19, 2007
Messages
49
Hiya folks,

I made my first really good fixed blade in D2 using stock-removal, b y hand. :rolleyes: I didn't have any machines, save a grinder, and had no idea about blade geometry, etc. It's flat a ground blade, but it's perfectly symetrical, etc. (Someday I'll do a nice hollow ground.)
I sent it off to "O&W Heat Treating" in either Ct. or Mass., I don't remember where, and specified a Rockwell of 58-59.
The thing came back at 63!
Is it going to shatter on me? I mean, I'm unlikely to ever actually use it, but it has this ring to it like Stueben glass!

-edit- The blade came back with really large "X"s, I assume Martensites? Is that a characteristic of highly polished heat treated D2, or did O&W heat it to high/long?

The other thing is that I had stamped my initials where the blade meets the tang, and when I got it back, it was bowed by a few thousandths. I honed it down on both sides, and basically reground the whole damn thing, but my signature is gone.
This was about five years ago, and I've been busy with silver and gold smithing since then. I'm all fired up to kick out another knife, or ten, as I now have an Arboga Maskiner milling machine I can play with. I want to make some folders.
How do I stamp my signature on the blade and not have it distort during heat treatment? do I have to anneal and "set" the mark? -This is a process in silversmithing where you flatten the area around your maker's mark; I dunno what you knifesmiths would call it.

Thanks, all.
 
I wouldn't stamp D2, especially after HT. You should etch your logo on.

Try tempering at 400 F for two hours. If that doesn't lower the HRC, then send it to someone who knows what they're doing (eg. Paul Bos) for reheat treat.

The ideal HRC is 61 for D2.
 
"large Xs " ??? you can't see martensite without a microscope. I have no idea what you saw ,perhaps nothing was done to insure no scale was formed .Send the next one to someone who knows how !!!
 
I didn't stamp it after treating, I stamped it before.
The x's are part of the grain within the steel. The blade has been re-lapped since it was treated (due to the slight bow [presumably] from stamping).
I can clearly see a grain with random criss-cross crystaline structures.

I could try to photograph it, but I think it will be very difficult to capture. Perhaps using software to exagerate contrst, it would come out.
 
Welcome to Bladeforums!

moving-van.jpg
 
In my opinion, 515 F is a good temper for D2. The hardness will probably be around 60 (unless it had cryo, then it will be perhaps 62), and the impact strength is pretty optimal. D2 is kinda unusual I think in that, past a certain point, the toughness actually goes down with the hardness the hotter you temper. 515 is a sweet spot.
 
Thank you for the welcome, Cougar Allen.

Nathan, are you suggesting that they must have cryoed my blade to achieve that Rockwell?

You guys all talk like you harden all your own stuff. It's unusual for someone to send it out for that?

I have an electric kiln, just not the knowledge & confidence, I guess. (I'll hang out here for a while. ;) )
 
D2 peaks in impact strength at HRC 60. If you go much higher it wiil be subject to edge chipping, while lower you may see edge rolling. D2 is very good at optimum heat treat, but if not tweaked for best performance, it would be better to buy cheaper steel.
 
SterlingHammer said:
Thank you for the welcome, Cougar Allen.

Nathan, are you suggesting that they must have cryoed my blade to achieve that Rockwell?

You guys all talk like you harden all your own stuff. It's unusual for someone to send it out for that?

I have an electric kiln, just not the knowledge & confidence, I guess. (I'll hang out here for a while. ;) )
Click to expand...


It is possible they froze it. In my opinion, the best heat treat for D2 includes cryo as part of the quench. The steel retains austenite (by design, to prevent dimensional changes in tooling made of it) so you need to freeze it to complete the martensite conversion.

Tempering to the secondary hardening hump probably converts most of the retained austenite, but there are good reasons, IMO, not to go to the second hump. Hence the freeze.

I HT and freeze my own D2. Lots of folks do.
 
Please forgive my ignorance, and not to digress too far, but how does one go about cryo freezing? Does that not require very special equipment and material?
 
SterlingHammer said:
but how does one go about cryo freezing? Does that not require very special equipment and material?
Click to expand...


It requires a small beer cooler, five bucks and a trip to the Harris Teeter for dry ice.

You fill a steel bowl half way with acetone, break your dry ice into pieces and fill the bowl up with ice. The acetone will get down around -100F, which is potentially dangerous if you spill it on you. And acetone is kinda dangerous by itself. It is wildly flammable and fumes aren't good for you (it doesn't fume much while this cold BTW). So I do this in a shed away from everything.

It ought to soak at least an hour.
 
Or, if you can get some LN nearby, you can always get a good stainless
steel thermos - in a size that would accommodate your blade and do the
Ultimate Cryo (TM) - for bragging rights, if nothing else :)

The LN will prolly evaporate in a day or 2, so it is essential you get it at
a decent price and may do few blades while on it .
 
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