View Full Version : Very rapid quenching

Gabe Newell
03-02-2004, 01:19 PM
I thought this was an interesting read.

Rapid Quenching (

Jerry Hossom
03-03-2004, 08:02 PM
Gabe, I read through this twice now and I'm still not certain I understand its points. I get the sense that what they're promoting is something akin to edge quenching knife blades, but in three dimensions. The intent I gather is to reduce stresses that cause dimensional distortion and surface cracking, which is certainly critical to such things as dies and molds, but knifemaking has other ways of addressing those issues. One thing's for certain, we don't want a soft center in a knife blade, at least not too much of one. The center is where the edge is.

Hopefully, Mr. Cashen will step in here and bail me out, so I don't have to embarrass myself any further. I'm responding primarily so you don't think you're being ignored. Personally, I'm thankful Paul Bos takes care of these things for me. :)

Gabe Newell
03-03-2004, 10:56 PM
Reading it made me think about:

- the temporal aspect of quenching (I had the simplistic idea that you could think of the steel as basically cooling simultaneously throughout the structure)

- other than the edge, that steel can only cool as fast as the thermal conductivity of the steel allows (which made me go to the ASM handbook and finally understand the charts about the maximum size of hardenable structures)

- the role that martensite can play in helping stabilize a quenching piece of steel

I'm going through a metallurgy phase, so you'll have to put up with me going "gee, whiz". For example, imagine how cool it would be to make fittings out of austempered ductile cast iron ... woohoo!

Jerry Hossom
03-03-2004, 11:46 PM
Originally posted by Gabe Newell
(I had the simplistic idea that you could think of the steel as basically cooling simultaneously throughout the structure)

As it relates to knife blades, I think that is generally true unless you take steps to prevent it, by edge quenching, clay packing the spine to retard cooling in that area, or some other mechanism.

Much that's written about hardenable steels relates to larger/heavier structures than knife blades, and for purposes that have requirements very different from knife blades. In most cases knifemakers have manipulated steel processing to their own purposes to make blades that are simultaneously hard and tough, using heat treating methods different from those used with the same steels fashioned for other needs. The latter however is what you usually are reading about in steel company literature and can be misleading when it comes to understanding how steel performs in knife blades.

Compounding that disconnect are the widely varied purposes to which knife blades are applied as well as the varied demands and stresses placed on knife steels in practical use. Add to that the issue of edge and blade geometry and you have a pretty complex formula, and no pat answers.

The more I learn, the less I know... :)

Kevin R. Cashen
03-04-2004, 11:01 AM
Originally posted by Jerry Hossom
...Hopefully, Mr. Cashen will step in here and bail me out, so I don't have to embarrass myself any further...

Well, I will see what I can do. After briefly reading over it I started to wonder why they were trying to make the technology sound so "new" and revolutionary, when much of the principals described were utilized in Jominy and Boegehold's work back in the late 1930's:confused: But then I looked at the home page and noticed that they seem to be a firm offering special heat treating services, so essentially I took it as an interesting sales pitch.

This is a common problem with information on the internet. Beyond the issue that anybody can publish anything in the internet, we must also always remember that the internet is one big commercial ad :( .

Not that you can't get good information from an infomercial, there is plenty to learn from in this sites information, but we need to remember that anybody would tend to embellish or dress things up a bit if they are trying to sell something. This is part of the problem with all the hype about cryo these days. Most folks are getting thier ideas of what it does, and what it doesn't do, from adverstising on the net from places trying to sell the service. We need unbiased independant research to take it really seriously.

One new or radical positions put forth here is the idea that high strength, or toughness for that matter, could be gained by quenching from Ms to Mf very quickly. It gets very complicated but this is a fairly radical deviation from much of traditional metallurgy.

They touch on another thing that perhaps I am a little confused on, since I see many knifemakers proposing the same idea. The idea that cooling quicker from Ms to Mf will give a harder martensite. This perplexes me. If you don't have any pearlite, bainite or retained austenite... all you have is martensite :confused: And alpha martensite is alpha martensite, I am not aware of any undiscovered "super- martensite" structure. I have found that if you quench a deep hardening steel (say O1) in water (and manage not to crack it) and take an identical piece in oil, they both read HRC 64.5-65 :confused: Unless somebody is proposing some funky short, time-dependant precipitation in the matrix, I don't get it :confused:

Jerry Hossom
03-04-2004, 12:26 PM
On that latter issue of faster quenches, CPM-3V and S30V do not harden, or perhaps remain hardened, if they are not quenched very quickly - i.e. a very few seconds to below 1000F. Many of the early reviews of CPM-3V panned the steel as inferior. Most were done by those who do their own heat treating and had no way of knowing what the hardness was after quench or the final hardness after tempering.

I realize you were probably speaking to oil and water hardening steels on that point, but wanted to assert that air hardening steels are somewhat different.

03-04-2004, 12:37 PM
The speed of quenching with non-conducting media like oil and water will always be limited by the media. The conductivity of the steel will always transfer heat faster than the convective process will take it out of the metal.

All of the liquid and gas quenching methods cool convectively. Boiling is also a convective process that requires a large heat input to create the change of state to the liquid, slowing down the process at the metal/ liquid interface.

This is why plate quenches are so effective-they remove heat by conduction.

In simple Carbon/Iron systems, the Austenite/Martensite transition will move through the steel at ~3000'/sec. (this from a textbook on crystal deformation from my grad school incarnation, I will supply the reference if anyone wishes). I believe this is limited by the rate of conduction. I don't have any information on transformation rates through higher alloys, although I expect them to be slightly lower, if different at all.

In a system consisting of Martensite and Carbides, the advantage that might be gained by faster quenching is to limit grain size and thus limit crystal boundaries that might serve as crack tip nucleation sites. While the hardness will not differ, the finer grained material will be tougher and have a more uniform composition.

03-25-2004, 12:29 AM
Thanks for the link Gabe.


03-25-2004, 01:22 AM
Maybe I'm reading it wrong I'm no metalurgist, but it seems to me they're also saying that by cooling it faster, the outer surface is cooled more evenly. With a solid outer shell instead of an uneven one it would hold the item in shape and prevent warping as the center cools.