Quench plates or oil

Doug Lester

Well-Known Member
The difference is the rate of cooling plus quench plates can help prevent warping. They can be used with complex alloys that are deep hardening. Like air hardening. Oils are quicker cooling and, depending on the oil that you choose, can be used with simpler alloys that can range from shallow hardening to deeper hardening steels that won't air quench.

Doug
 
OK so what i do now is I take my 9" .125 1075 blade heat to non magnetic in a forge then quench in 125 degree canola for 10 sec. then clamp between 1/4 '' angle iron seems to work out most of the time. Is there any reason to use quench plates instead of the angle iron after the oil quench? OK now i make a under .125 1075 blade will it harden in quench plates ?
 

EdCaffreyMS

"The Montana Bladesmith"
Is there any reason to use quench plates instead of the angle iron after the oil quench?
Aluminum or copper plates, generally 1"+ thick are preferred for plate quenching, because the transfer heat MUCH better then steel/angle iron. In some cases, the angle iron will not cool the steel rapidly enough to fully harden.

The best advise is to educate yourself on what steels are "oil quench", and what steels are "air quench", and use the method intended for the particular steel type you're using. Plate quenching non air hardening steels can be hit and miss. As other have mentioned using it for thin blades..... It is a learned skill, and those who do it, have experimented, and likely lost some blades in the process of learning how to do it. ;)

OK now i make a under .125 1075 blade will it harden in quench plates ?
What you have to realize is that there are few absolutes in Bladesmithing/Knifemaking. THEORETICALLY, yes, but there are always variables to deal with. If you were using 1" thick aluminum or copper plates, I'd say a complete YES..... but angle iron? I suspect you'd have mixed results at best.
 

Chris Railey

KNIFE MAKER
I should have mentioned that my plates are inch thick aluminum. I only use 1080-1075-15N20 and 80crv2 though I have never plate quenched 80crv2. The others do fine for me under .125”. I started using plates when attempting fillet knives at .063” 15N20. I really would not attempt a plate quench with angle iron. If you quench in oil first to a good black heat or lower then clamping in angle iron can help the blade to stay straight as it cools further but the steel angle iron will not significantly cool the steel. There are other steps you can take to avoid warps pre-HT too.
It’s easy to get overloaded when first delving into heat treating your own steel. Pick a source or two and follow what they say all the while testing your results until you are happy with your products. It sounds to me like you do simple heat treat which is HT in a forge with no exact temp control. I do simple HT, Dennis Moreland does simple HT too unless he bought an oven recently. I would go to Kevin Cashen’s website and look up his HT info for the 1075 you are using. Good luck.
 
Last edited:
Sorry my question was confusing.I was using angle iron after the oil quench only to keep the blade straight.I never ment to substitute angle iron for quench plates.
 

tkroenlein

Well-Known Member
I should have mentioned that my plates are inch thick aluminum. I only use 1080-1075-15N20 and 80crv2 though I have never plate quenched 80crv2. The others do fine for me under .125”. I started using plates when attempting fillet knives at .063” 15N20. I really would not attempt a plate quench with angle iron. If you quench in oil first to a good black heat or lower then clamping in angle iron can help the blade to stay straight as it cools further but the steel angle iron will not significantly cool the steel. There are other steps you can take to avoid warps pre-HT too.
It’s easy to get overloaded when first delving into heat treating your own steel. Pick a source or two and follow what they say all the while testing your results until you are happy with your products. It sounds to me like you do simple heat treat which is HT in a forge with no exact temp control. I do simple HT, Dennis Moreland does simple HT too unless he bought an oven recently. I would go to Kevin Cashen’s website and look up his HT info for the 1075 you are using. Good luck.
So plate quenching is as fast as "water" quenching?
 

Chris Railey

KNIFE MAKER
I suppose that I'm inferring it must be to do something like 1075 especially, that is typically quenched in P50 or water.
I can tell you that I have hardened it in thinner cross sections using my plates. The only way I have to test how hard is with a regular file because my HT's are simple in nature. I cannot debate with you on the quench rate for water vs P50 where 1075 is concerned. I made no claim that plates were faster than water so I have to be honest here I am not sure what you were trying to accomplish with you faster than water comment so what ever bone you are wanting to pick with what I said, you win.
 
Last edited:

billyO

Well-Known Member
So plate quenching is as fast as "water" quenching?
It's my understanding that water quenching is the fastest, followed by oil, then plate quenching, and lastly air.

I'll also add here that there are folks who are a lot smarter than me (ABS Master Smiths and some metallurgists I've talked to about this very question) who claim that plate quenching steels that are "oil quench" steels doesn't work consistently. But I also think these same folks might not be making a distinction between thin kitchen slicers and thicker knives (EDCs, hunters, bowies, etc.) There's also a difference between "fast oil" and "slow oil". (See Larrin's Book Table 21.1 on P 258)

Here's how I look at it. I do 1080/15N20 damascus almost exclusively, and looking at the TTT diagram for 1080 in Larrin's book, in order to "avoid the nose" of ferrite formation, I need to get below 1000F in ~5 sec or less, and the really thin cross sections of my kitchen slicers (~0.070" at the thickest) should be able to get there that fast with my 1.5" thick aluminum quench plates. (I am getting close to doing some experimentation once I nail down someone with a hardness tester to get some numbers.)
 

tkroenlein

Well-Known Member
I can tell you that I have hardened it in thinner cross sections using my plates. The only way I have to test how hard is with a regular file because my HT's are simple in nature. I cannot debate with you on the quench rate for water vs P50 where 1075 is concerned. I made no claim that plates were faster than water so I have to be honest here I am not sure what you were trying to accomplish with you faster than water comment so what ever bone you are wanting to pick with what I said, you win.
I'm not picking a bone or debating. And I didn't say faster, I said as fast. It was just a simple way of asking something much more complex. Never mind, I guess.
 

Chris Railey

KNIFE MAKER
I'm not picking a bone or debating. And I didn't say faster, I said as fast. It was just a simple way of asking something much more complex. Never mind, I guess.
If you were truly asking an honest question about which is a "faster" quench then I would assume it would be water. I do not know for sure because the thought of quenching anything .063" thick in water does not appeal to me so I have not done that. Your previous comment just read like a statement more so than a question but I will take you at your word that it was not, thanks for clarifying.
 

billyO

Well-Known Member
I don't know if it should be deleted. I just think some of the questions (no offense intended here) are a bit vague. And there's multiple questions that are related, but going in different directions.
Is there any reason to use quench plates instead of the angle iron after the oil quench?
If I'm reading correctly, for what you are doing, which is trying to avoid warping after the initial cooling/quenching of the steel, then no, I can't see any reason for you to go out and purchase aluminum of copper plates.
OK now i make a under .125 1075 blade will it harden in quench plates ?
This is where the debate/questions come in, and I don't think there's any specific information out there about this, only anecdotes of personal experience.
Again, no offense intended here, but I see a couple of references to "blades under 0.125 inch". What are we talking about? 0.124"? or 0.063"? or some specific thickness in between? I'm sure there's an answer there, it's just that nobody has done the research to find it. Yet.
 

Kevin R. Cashen

Super Moderator
It would be a shame not to help the original poster here despite the confusion. My friend Tim Zowada has a very profound saying regarding his knifemaking philosophy- “it is the things you can’t see that matter most.” There are two types of knifemakers that I have encountered over my career. There are those who make a knife they like, and if it does what they want they are happy; I envy them. Then there are those who will literally lay awake at night fretting about the things you can’t see.

Virtually every disagreement that has arisen over the years in my discussions about what may be the best heat treating method was rooted in not establishing which of the two philosophies defined the parameters of the conversation. If you ask me what the result of a particular method may be, my default mode in answering is based upon the things you cannot see, but I have spent years seeing (the worst thing I ever did for my peace of mind was slide that first piece of steel under the microscope). This does not, however, negate the views of those who are happy with their results without knowing how much of that last percent was achieved. I really do not wish to play the role of the serpent in anybody’s garden if they wish to remain in Eden, for I myself have been banished and wander the earth with the taste of the fruit forever in my mouth.

So, I will not get too deep so as to respect all present but, for the sake of the original question, help to clarify a few concepts that may help to find your own path-

Plate “quenching” would involve clamping the steel between conductive plates at austenitizing temperature, and allowing conductive cooling to supercool the blade fast enough to avoid intermediate phases forming at Ar1 (the transformation temperature on cooling).

For water quenching steels this temperature is around the 1,100°F range, but diffusion is so rapid at this temperature that you need to get through the range in less than one half (0.5) to three quarters (0.75) of a second to avoid the precipitation Fe- Fe3C phases (primarily pearlite) . This is why these steels are defined as “water hardening”.

When you add alloying to the steel, e.g Mn or, especially Cr, you begin to push Ar1 lower, suppressing the formation of those phases. The result of lower Ar1 temperatures will be slower diffusion and more time to cool it through the range to avoid the other phases (primarily pearlite). You may now have anywhere from 5 to 15 seconds to do that. This is why these steels are designated as “oil hardening.”

With oil hardening steels that have larger amounts of alloying, Ar1 can be suppressed to below 1,000°F and diffusion becomes so slow that pearlite will no longer form and other phases will become a threat (primarily upper bainite). Because of this, these steels are not truly air hardening but may appear to be able to do so. For example- air cooled L6 can give you Rockwells of 63, but it performance will be miserable due to the massive amounts of mixed phases.

Finally, we have steels that have alloying, such as Cr in excess of 12%, that push Ar1 so low that no other phases can form even when just cooling in air. We call these “air hardening” as they truly are.

Please be aware that none of this is “all or nothing”, nothing in steel is 100%, we are always trying to trim off those extra phases to the levels that are acceptable to us. There are levels that will allow the knife to do what we want, even though under the microscope, it may be shocking. We just need to find our happy spot, our Eden.

As I mentioned, true plate quenching is applied at austenitizing temperature and completes the hardening process. Cooling in oil, for a timed quench, and then plating the blade before it is hard, but after all the undesirable phases have been avoided is NOT plate quenching. It is a modified timed quench, isothermal if you will, in oil. And it will not necessarily yield the same phases as a full plate quench. But it will help keep things straight, and I have utilized the method myself.

There was a time when there were no “fast oils” because we had water hardening and oil hardening, but eventually industry desired an alternative to the pitfalls of water, and oils were developed to approach that speed, but this was later in the game and only a few needed it in a time when the rest of the world was transitioning from oil to air.

One last point to consider, plate quenching relies entirely on conductive methods of cooling, i.e. it needs direct, metal to metal, contact to work. Which knife bits have this contact, and which ones don't, is an important thing to examine.

I am not here to tell anybody what is the correct way, I just wish to give you the facts of what happens and let you decide your path to contentment.

I hope this helps.
 
Last edited:
Top