D2 heat treat, edge retention testing

I'm not sure this is exactly what your intention was with this thread or not, Nathan, so if this is digressing, PM me and I'll erase this post.

The folks that keep having Park's 50 thrown in their faces are being much maligned here, and needlessly so. Perhaps the zealot behavior ascribed to them is the result of something, just the same as the position many have expressed in this thread. I think what's being overlooked is that even those science guys can appreciate the 'art' as Makermook describes it... what they might take issue with is the staunch refusal for someone to accept new information because it doesn't support their own worldview.

Case in point: many moons ago a well respected knifemaker and writer produced an article providing a review of a new forging steel. Rather than considering the instructions provided by the company that made the steel, he insisted on applying his 'tried and true' old-timey methods (which, for the record, don't even approach the recommended heat treatment of the steel) and experienced questionable results with it - stunning!

When I protested his methods, and provided him with the scientific documentation (that was made available to him before his testing, unbeknownst to me), I was met with this:

I should have had a disclaimer that edge quenching in (quenchant name omitted) is only for the most experienced and certainly not recommended for those with digital controlled furnaces and real quench oil. However, I suggest that you do not blindly trust your high tech equipment. Be sure to test your blades in actual using conditions against blades of known value.
If digital controls and special quench oils were the only way to get good results I doubt that the US could have beat the British in the Revolutionary War. How about the knives that lasted Lewis and Clark through their two-year adventure? Do you know how the blades were heat treated that helped the US win WW1?


The quote in italics have been edited only to remove personal information about the writer to make a (feeble, I guess) attempt at maintaining his anonymity.

Points:
1- The author didn't follow his own advice and establish a known baseline reference by following the instructions first (thereby following known data, same as you do with your treatment of D2), unless we're required to start from scratch and ignore the wisdom of those that came before - something I find more disrespectful than calling bullshit on someone that doesn't have enough common sense to learn from others...
2- The control over alloying elements was questionable, at best when we fought the Redcoats. Simple steels have much simpler heat treat requirements - assuming you're even willing to meet even those requirements!
3- Lewis & Clark regularly injected massive quantities of mercury into their penises via a catheter to alleviate the symptoms and cure venereal disease - the cutting edge of their science, at the time. Perhaps the wisdom of their age has been surpassed a pinch?

Is this man's position in defense of his 'art'? Have you considered edge quenching your D2 blades in (quenchant name omitted)? Perhaps that's why you're not getting the same results as Mr. Dozier, although I doubt you'd consider doing that.

Quoting Mr. Dozier from a post he made years ago on another forum:

Any steel co. will give instructions on heat treating D2. Your best will be to temper at 600 t0 700 - 2hr's.- twice or three times if you feel the need to. The edge holding ability will not be as good at this hardness but will be tougher. I like the higher hardness for edge holding and high strength.
There is no secret, only close control and the need to be exact with every thing you do.


Please don't misunderstand me - it's not my goal to start the art vs. science war again. To prove my point, I'll show you a picture of my 'grail' blade... the one I'll never own, but shall forever hold in envy and awe:

YakuzaIll.jpg


The scientist in me is still capable of understanding that the art represented here is entirely intertwined with the function. I hold out no hope to ever be able to achieve something so extraordinary.
 
The purpose of this thread was to illustrate what I consider to be a practical approach to real world testing, especially when you get to the point of splitting hairs and are looking for subtle differences. I'm purposely trying to avoid discussing specifically how to heat treat D2, or where is a good place to send stuff out for heat treat, or how super duper my knives are, or (especially) the old debate around here about science.

The problem, as I see it, is that a lot of testing that involves using the knife how it was intended to be used (the most relevant kind of testing) does a poor job of evaluating the effects of subtle changes to your process. I wonder if this is how a lot of the silly stuff that people do got started. They made a change, cut twice as many leather strips or pieces of rope and decided that's a lot of cuts and therefore the change must be of benefit. However, if the change was to add a very slow ramp up to the preheat (which would actually do practically nothing) but the leather was softer than usual or the rope was cleaner than usual, they wouldn't understand the meaning of what they saw. But a group of control knives run through the cutting test at the same time would allow them to catch that change. And that, is all sighintiffick.

I agree with people who say that you shouldn't just blindly accept the industry standard heat treats, not because I don't believe that industry knows what it is doing (it generally does) but because the guidelines we're given are not always well tailored to what we're doing.

While reading about D2 and recommended techniques for processing it, I have noticed incongruities and even contradictions between texts like "the heat treaters guide" and "tool steels", for example differences in recommended cooling rates for annealing and approaches to hardening already martensitic structures. And I've noticed that some of the data changes from older editions to newer editions, such as about 5% RA in an old text for a particular austenitizing temperature, and more like 20% in a new text for the same circumstances. And the graph simply omits the temperature it was quenched to when they made their measurements, which is highly relevant.

I believe that the vast majority of the people in that industry that are using these texts simply want to harden a die to a customers HRC specification without it cracking or distorting. They couldn't care less about fine edge stability and they actually like a little RA because it reduces dimensional variations. And the more stabilized the better, because they don't want it converting later and making the ejector pins bend. Most don't really care about sharp knives.

Did you know it is possible to dramatically reduce the grain size in D2 with pre quenching? It is seldom mentioned in texts, and it sure as hell isn't mentioned in the spec sheet you get from Crucible. I think that is because a person making a stamping die couldn't care less and that is who the steel is designed for. Did you know that a rapid quench increases free chromium in D2, improving corrosion resistance and reducing chromium carbide fraction? That's another one that's hard to find. Ever wonder what is the mechanism behind the higher hardness in oil quenched D2 or 154 or 3V etc? I mean, under the nose is under the nose, isn't it?

D2 generally has vanadium in. Quite a bit actually, about 1%. But, like hotdogs at the grocery store, individual manufacturers are free to put whatever they want into it. Vanadium is spendy, chromium is cheep. A high chrome low vanadium D2 will put more carbon into solution at the higher temps, increasing problems with RA, and should probably be treated differently.

So, I'm not being anti science when I say you shouldn't trust everything you read from industry and the steel manufacturers. Just following the "instructions" for D2 could well have you tempering when warm to the touch, which I think will make a miserable knife blade. I'm saying that you should test your work and experiment and don't be afraid to step a little out of the box. And certainly we shouldn't criticize people who have come up with weird HT processes if they have done their testing and we haven't personally evaluated the results, because there is still plenty of things we don't know (or the texts would stop changing).


edit:

I've never mentioned this here before, but I'll tell you that my mother is a chemist (retired from BASF) my wife is a molecular biologist performing research for UNC Chapel Hill, my biological father was a chemical engineer, my sister has a degree in physics (though doesn't practice) and my brother is a computer scientist. I'm surrounded by scientists, geeks and nerds. I grew up with them, and I have seen both science and industry from the inside and I can say that, from my point of view, "real" science in the "real world" is not perfect and incorruptible. It is often messy, wrong and full of egos and hype, just like anything else. Our little community here actually does pretty well.
 
Last edited:
You must log in or register to reply here.
Back
Top