Rockwell Hardness is the Megapixels of Knife Specs

[Larrin]

In this article I described what Rockwell hardness is and what it is measuring. How well does Rockwell hardness correlate with toughness and wear resistance? When is Rockwell hardness not a good measure of strength?
https://knifesteelnerds.com/2018/11/12/ ... -hardness/

[JD Spydo]

Well "Larrin" you've given us another great piece of knowledge about the vast subject of "metallurgy" and how it relates with the requirements of what makes up a "Good Knife" versus one you buy at "Rip-Mart". I took two metallurgy courses at our local community college and after reading your stuff I feel like I just barely got my feet wet.

I think that Metallurgy and Knifemaking specifically are two areas of study that you actually have to get your hands dirty and actually do it to really learn the important aspects of it and to better understand it. I've toyed with the idea of getting a Govt grant or loan and trying out that Bill Moran school of knifemaking.

The aspects of toughness and tensile strength really put a completely different set of requirements for a good knife steel. Because take ZDP-189 for instance. It was a great steel for plain edged blades but failed miserably when they tried to make Spyderedges blades out it. And I do believe it was because there were not adequate toughness and tensile strength properties to make it a versatile blade steel. And Larrin if I'm barking up the wrong tree please call me out on it>> it wouldn't be the first time I've had to eat crow on this great forum :o

[Larrin]

Well "Larrin" you've given us another great piece of knowledge about the vast subject of "metallurgy" and how it relates with the requirements of what makes up a "Good Knife" versus one you buy at "Rip-Mart". I took two metallurgy courses at our local community college and after reading your stuff I feel like I just barely got my feet wet.

Why is my name in scare quotes?

I think that Metallurgy and Knifemaking specifically are two areas of study that you actually have to get your hands dirty and actually do it to really learn the important aspects of it and to better understand it. I've toyed with the idea of getting a Govt grant or loan and trying out that Bill Moran school of knifemaking.

The aspects of toughness and tensile strength really put a completely different set of requirements for a good knife steel. Because take ZDP-189 for instance. It was a great steel for plain edged blades but failed miserably when they tried to make Spyderedges blades out it. And I do believe it was because there were not adequate toughness and tensile strength properties to make it a versatile blade steel. And Larrin if I'm barking up the wrong tree please call me out on it>> it wouldn't be the first time I've had to eat crow on this great forum :o

ZDP-189 has very high hardness which means its "ultimate tensile strength" or at least its "ultimate compressive strength" should be high. I'm not sure what the results of the spyderedges was; I'm not familiar with that. The toughness of ZDP-189 is certainly quite low which could be a problem.

[JD Spydo]

They had at least 3 models that I know of that they did Spyderedged blades with ZDP-189 and they didn't last long at all. From the best of my memory they had severe chipping problems and from what one of my knife pals told me he literally had a couple of the teeth break on him.

The complaint was broad based from several users from what I remember. Since then ZDP-189 no longer has the fanfare it once had. Not sure how many Spyders now are offered with ZDP-189 but it's not what it used to be. And I still have two of my plain edged ZDP-189 models but I personally never tried it in SE. Glad I didn't waste my dollars.

I do find it strange because 440V which I always found to be a monster to sharpen I also found out to be a great blade steel for Spyderedges.

[Larrin]

Thanks JD.

[The Meat man]

Great article Larrin. I didn't know that the same steel at the same hardness could have such different properties depending on HT temperatures.

[JD Spydo]

Great article Larrin. I didn't know that the same steel at the same hardness could have such different properties depending on HT temperatures.

Yeah I was kind of amazed too. Hey Larrin what do other treatments like "Cryo-Quenching" with liquid Nitrogen do to change the properties of blade steel? I've heard that Liquid Nitrogen is expensive but yet effective on certain blade steels? What else do they use for quenching treatments on blade steel?

[Larrin]

Yeah I was kind of amazed too. Hey Larrin what do other treatments like "Cryo-Quenching" with liquid Nitrogen do to change the properties of blade steel? I've heard that Liquid Nitrogen is expensive but yet effective on certain blade steels? What else do they use for quenching treatments on blade steel?

The primary effect of cryogenic processing is to reduce retained austenite which gives you an increase in strength and hardness. That usually also reduces toughness though not always: https://knifesteelnerds.com/2018/06/04/ ... ar-z-wear/

There is also scientific literature suggesting there is an increase in wear resistance due to increased carbide precipitation (I can't go into that in any detail without a whole article on it). In the 154CM CATRA article there was no benefit from cryo outside of hardness: https://knifesteelnerds.com/2018/06/18/ ... retention/

That doesn't necessarily mean that there is never a benefit for edge retention with cryo but contradicts some of the wild reports like 500% increase in wear resistance with cryo.

[Bodog]

I've always believed that for a rough edc knife some amount, say 10 to 15%, of retained austenite was a good thing, if only to retain some raw toughness. Not for stupidity's sake, but just to keep things together better at the edge.

[Larrin]

I've always believed that for a rough edc knife some amount, say 10 to 15%, of retained austenite was a good thing, if only to retain some raw toughness. Not for stupidity's sake, but just to keep things together better at the edge.

I am not anti-retained austenite, but I am pro-understanding the tradeoffs.

[Baron Mind]

Yea that's the stuff

[Deadboxhero]

Larrin, that was a beautifully written article. Such a vast and complex subject but you highlighted alot of the variables and sourced them.

I really enjoyed that you explained that the steel could have the same HRC but different properties based on how it was austenized and tempered etc.

Very in depth, well sourced and directly from a Metallurgist, it doesn't get better then that. :D

Also, it was nice to see links in this article to connect the dots to the other very in-depth articles that can explain even further and really help.

I can tell these articles really take a lot of time to edit, research and to make concise, I really appreciate the work and I'm happy I support this work on patreon.

Keep them coming, I learn so much and I put it all in practice.

Shawn.

[Larrin]

Thanks Shawn.

[Cycletroll]

Thanks Larrin! Very edifying as usual! :)
This article certainly validates Shawns obsession with pounding various blade concoctions thru 16 penny nails

[Larrin]

Thanks Larrin! Very edifying as usual! :)
This article certainly validates Shawns obsession with pounding various blade concoctions thru 16 penny nails

I shouldn't encourage him.

[JD Spydo]

It's really interesting to consider all of the vital properties that make up an ideal blade steel. For a tool as seemingly simple as a knife it's interesting to consider how many things to consider to come up with a good quality tool.

I'm hoping at some point that Larrin will consider doing a study on what makes an ideal blade steel for Spyderedges and other serrated edge patterns on knives. Because there is no doubt that an ideal blade steel for Spyderedges is a somewhat different animal in many aspects.

Also I'm looking forward to knowing more about the Nitrogen based blade steels too>> i.e. H-1, LC200N ect. great stuff Larrin :)

[JD Spydo]

Larrin for future reference whenever you get around to it. I've got a few blade steels for you to consider that I've personally found that seem to do really well in Spyderedge ( or any other serration pattern for that matter). Some of them have actually surprised me and I think you'll find it most interesting when you check them out. Because for one thing there are very few blade steels I've found to be above average in both SE & PE. Two exceptions to that rule are ATS-55 and VG-10. Because I've had good results from both of those in both edge types.

The following are blade steels I've found that do really well in SE: They are 440V ( S60V), AUS-8, ATS-55, VG-10, GIN-1 ( G-2), XHP, MBS-26, and of course H-1 but my jury is still out on LC200N because I've yet to have to opportunity to test drive it in SE>> although I've heard good about it in SE.

It would be interesting to find out which properties that some of these steels may have in common or may not have in common. Take 440V for instance>> now that's one that really surprised me as being a great Spyderedge steel but I can guarantee you that it does much better than it's brother ( S30V) in SE. You just wouldn't have thought it would be up there in the rankings :confused: But there may be several properties that make up a good blade steel for SE.

Oh one more I can add to that list>> whatever the heck J.A. Henckel makes their culinary knives from is also a good performer. Last summer I scored a few J.A. Henckel culinary knives at some local thrift stores for less that $1 each in most cases and I've found it to be really good in SE>> but I have no idea of what they use and I've tried to find out with no luck. OK just something to consider?