Plate vs. Oil Quench

[Mobius1]

I've brought up this topic in the past, a few years back, and I kinda feel like revisiting it again, because I have never been able to get information that really satisfies me. I've spent hours and hours searching the web for information, namely, on oil quenching stainless and air hardening steels. It seems like almost all bladesmiths use aluminum plates to quench, but I have always doubted it's superiority over using oil. From my humble understanding - quenching in oil results in higher hardness and less stabilized RA.

Specifically, I have typically worked with 3V, and have recently switched to Z-Wear, and I have always oil quenched them, and have loved my results. I use Condursal Z1100, quench in oil until the blades stop glowing, and cryo using LN2. Specifically in my 3V testing, I have noticed remarkable corrosion resistance, too (Even salt water doesn't give it so much as a patina.).

My main questions I have never really been able to answer, is what are the real differences between plate and (successful) interrupted oil quenching? Is my understanding about oil quenching RA and hardness correct? If so, why don't more people oil quench?

Clearly, quenching in oil stresses the steel more, and can cause fractures and warping, but in my experience I have never had any fractures from oil quenching (I do make sure I always stress relief when heat treating.). I can even do a complete non-interrupted quench and not have any visible stress issues.

But I do often wonder if I am creating issues I might not know about - Especially if I am quenching for longer than I should be. In fact, I would love to know why the quench even needs to be interrupted - What exactly is the purpose of this?

I also wonder about quenching oils - Is a fast quench oil going to have better results, or is a slower oil the better choice?

 

[HSC ///]

- quenching in oil results in higher hardness and less stabilized RA.

Specifically, I have typically worked with 3V, and have recently switched to Z-Wear, and I have always oil quenched them, and have loved my results. I use Condursal Z1100, quench in oil until the blades stop glowing, and cryo using LN2. Specifically in my 3V testing, I have noticed remarkable corrosion resistance, too (Even salt water doesn't give it so much as a patina.).

My main questions I have never really been able to answer, is what are the real differences between plate and (successful) interrupted oil quenching? Is my understanding about oil quenching RA and hardness correct? If so, why don't more people oil quench?

Clearly, quenching in oil stresses the steel more, and can cause fractures and warping, but in my experience I have never had any fractures from oil quenching (I do make sure I always stress relief when heat treating.). I can even do a complete non-interrupted quench and not have any visible stress issues.

But I do often wonder if I am creating issues I might not know about - Especially if I am quenching for longer than I should be. In fact, I would love to know why the quench even needs to be interrupted - What exactly is the purpose of this?

I also wonder about quenching oils - Is a fast quench oil going to have better results, or is a slower oil the better choice?

I plate quench Z wear so I'm interested in your post. But I don't have answers for you.

you said - "quenching in oil results in higher hardness and less stabilized RA". How do you know this?

The Zwear I make is at the hardness I want, why chase more hardness?
It seems like at some point we are reaching past the point of diminishing returns...

Have you considered contacting Zapp? you could email the general mgr...

 

[Mobius1]

Honestly, I've been able to find very little about it, apart from comments made by Roman Landes, when he was describing his 3V heat treating process. I don't think I could even find the post online anymore, but according to my personal notes, he said that "The thin cross sections get higher hardness after quench (greater volume fraction of martensite) and a less stabilized volume fraction of retained austenite."

I am far from an expert on this, and I have tried to come to a better understanding of it, but in the end, what it really comes down to for me, is that if Roman Landes quenches in oil, why would I not want to do the same?

Now, whether this translates to Z-Wear or not, I don't know? But he specifically did say that oil quenching is suitable for any steel out of the air hardening class, and the data sheets seem to include it as an acceptable means of hardening as well.

The really unfortunate thing, is that I can find a zillion tests and comparisons of various heat treating and tempering methods very easily, but I have not found ONE where oil quenching was tested, compared, or analyzed.

 

[HSC ///]

Honestly, I've been able to find very little about it, apart from comments made by Roman Landes, when he was describing his 3V heat treating process. I don't think I could even find the post online anymore, but according to my personal notes, he said that "The thin cross sections get higher hardness after quench (greater volume fraction of martensite) and a less stabilized volume fraction of retained austenite."

I am far from an expert on this, and I have tried to come to a better understanding of it, but in the end, what it really comes down to for me, is that if Roman Landes quenches in oil, why would I not want to do the same?

Now, whether this translates to Z-Wear or not, I don't know? But he specifically did say that oil quenching is suitable for any steel out of the air hardening class, and the data sheets seem to include it as an acceptable means of hardening as well.

The really unfortunate thing, is that I can find a zillion tests and comparisons of various heat treating and tempering methods very easily, but I have not found ONE where oil quenching was tested, compared, or analyzed.

How straight are your blades from oil quenching? Do you have a straightness concern?
Are you doing folder blades or 9" kitchen knives? How many per month?

 

[Stacy E. Apelt - Bladesmith]

There are two main issues when you oil quench a stainless blade. Hardness and warp. The hardness will be a point ot two higher in an oil quench, but warp can be severe, especially in thin blades. The plates take care of the warp. Using hypothetical hardness, if the as-quenched hardness is 65 for oil and 63 for quench plates, the temper will be where to adjust the hardness for the final target of 61-62. Merely lowering the tempering from (hypothetical) 400F to 375F would be ll you would have to do.

 

[shqxk]

Well, from my experience aluminium plate quench bring the temp down as fast as oil for a thin blade. From 2000F I can easily cool it the the point touchable by hand in less than 30 seconds... I mostly do HT pre grinding for any high alloy steel tho.

And I believe the faster quench may benefit on less Cr carbide forming at around 1600F - 1300F which reduce toughness and corrosion resistance.

For most air hardening high vanadium tool steel, as long as you continuously cooling steel from austenitizing to room temp in less than 10 minute, you likely to get the max hardness.

 

[HSC ///]

Indeed we are generally doing thin flat parts, a kitchen knife at 3/32" or a little thicker, I plate quench and can deliver it at 63/64 RC.
I don't need more than that.

So I can't make a case for superiority of oil vs plate, but plate quenching works and it works very well and it's productive and efficient.
You can also stack and line up multiple blades in a foil pouch and get more done per HT cycle.

 

[Ken H>]

Sandvick engineers say to drop temperature on their 13C27, 14C28N alloys below 1100F (1200F?) in less than 2 minutes. Faster than that doesn't have any increase in hardness (so they told me). Aluminum plates drop faster than that with no problem so I've not considered oil quenching.

 

[Mobius1]

How straight are your blades from oil quenching? Do you have a straightness concern?
Are you doing folder blades or 9" kitchen knives? How many per month?

I almost never have warpage issues. I even make make knives as thin as .040" and ones that end up quite thin after a full flat grind (for small folders).

Granted, perhaps me using a Kool mister for all of my grinding helps somewhat as well. But whatever the case, I have never had any issues with getting rid of warpage, with a couple plates and a clamp either immediately after the quench, or during the temper.

Admittedly I haven't worked with blades longer than 4-5 inches, but I can't really see that making much difference. (I'll know soon enough because I plan to start making kitchen knives.). Also, I am just a hobbyist, so I certainly don't make massive quantities of blades.

There are two main issues when you oil quench a stainless blade. Hardness and warp. The hardness will be a point ot two higher in an oil quench, but warp can be severe, especially in thin blades. The plates take care of the warp. Using hypothetical hardness, if the as-quenched hardness is 65 for oil and 63 for quench plates, the temper will be where to adjust the hardness for the final target of 61-62. Merely lowering the tempering from (hypothetical) 400F to 375F would be ll you would have to do.

Why is more hardness a bad thing? Does the extra Rockwell you get from oil quenching result in less toughness? And why did Roman Landes recommend it for 3V?

Well, from my experience aluminium plate quench bring the temp down as fast as oil for a thin blade. From 2000F I can easily cool it the the point touchable by hand in less than 30 seconds... I mostly do HT pre grinding for any high alloy steel tho.

And I believe the faster quench may benefit on less Cr carbide forming at around 1600F - 1300F which reduce toughness and corrosion resistance.

For most air hardening high vanadium tool steel, as long as you continuously cooling steel from austenitizing to room temp in less than 10 minute, you likely to get the max hardness.

If plate quenching is faster, then where is the extra hardness coming from?

My main issue with plate quenching, other than what I already mentioned about doubting its superiority, is with bevel grinding. I much prefer to grind my bevels before HT, rather than fighting tempered steel, and risking getting it too hot.

I know some people grind their bevels first even with plates, but how do you do this with a full flat grind? Or near full flat? Or a saber grind even?

I just find quenching in oil to be easier, myself. And as for warpage...even if that was an issue - If oil quenching is superior, isn't it a worthwhile risk in order to get the best results possible? (Assuming it's superior, of course. Perhaps it's not.)

 

[shqxk]

I almost never have warpage issues. I even make make knives as thin as .040" and ones that end up quite thin after a full flat grind (for small folders).

Granted, perhaps me using a Kool mister for all of my grinding helps somewhat as well. But whatever the case, I have never had any issues with getting rid of warpage, with a couple plates and a clamp either immediately after the quench, or during the temper.

Admittedly I haven't worked with blades longer than 4-5 inches, but I can't really see that making much difference. (I'll know soon enough because I plan to start making kitchen knives.). Also, I am just a hobbyist, so I certainly don't make massive quantities of blades.



Why is more hardness a bad thing? Does the extra Rockwell you get from oil quenching result in less toughness? And why did Roman Landes recommend it for 3V?



If plate quenching is faster, then where is the extra hardness coming from?

My main issue with plate quenching, other than what I already mentioned about doubting its superiority, is with bevel grinding. I much prefer to grind my bevels before HT, rather than fighting tempered steel, and risking getting it too hot.

I know some people grind their bevels first even with plates, but how do you do this with a full flat grind? Or near full flat? Or a saber grind even?

I just find quenching in oil to be easier, myself. And as for warpage...even if that was an issue - If oil quenching is superior, isn't it a worthwhile risk in order to get the best results possible? (Assuming it's superior, of course. Perhaps it's not.)

Heat treating is my part time work. I do heat treating service for knifemakers in Thailand. I never found any increasing in hardness by using faster quench media even with water... I have try water quenching a scrap of D2 and N695 before to see any different in result and there is not.

I use both stainless 309 foil and Condursal Z1100 for protection. I used to heat treat blades post grinding too and believe me it's a pain in the ass when you have to straightening those M390, XHP etc. when the warpage is in the bevel.

For now I no longer heat treat any pre-ground blade... It's just far more economical to deal with hardened steel with right equipment like proper KMG and some good ceramic belt over risking with any chance of warping.

Especially for a folder blade or very expensive steel like Damacore which cost about $1,000 for a 12 x 2 x 0.16 piece , there are no rooms for any kind of warpage.

 

[samuraistuart]

When I first started getting into heat treating stainless steels, I oil quenched them after reading Roman Landes's work (and a few others). But honestly, I find plates to be WAY MORE than adequate for cooling stainless steel extremely rapidly. When using plates and compressed air, the blade goes from 1950°F down to 900°F FAST. You can even watch the color of the blade go from orange to black in a matter of seconds. So I don't use oil for stainless steel and high alloy tool steels any longer. Also, IIRC correctly, the data from Sandvick on steels like 13c26, 14c28n, (and most other stainless or tool steels like 154CM, 3V, etc), you need to cool the piece from your austenitizng temp down to 900°F within 2 minutes to get the maximum post quenched hardness. Plates with compressed air (and probably without the compressed air even) will cool the type of knives I make (hunters, chef, paring, kitchen utility, EDC, small camp, 1/16" up to 1/8") in literally seconds. I'm not so sure that oil can cool a blade that much quicker. Maybe by a little bit, but not by much if any.

 

[Mobius1]

So then why did Roman Landes say what he did?

I wish I had the means to really compare the two with thorough testing. I'm at least trying to get my hands on a good Rockwell tester which will for sure help!

 

[HSC ///]

So then why did Roman Landes say what he did?

I wish I had the means to really compare the two with thorough testing. I'm at least trying to get my hands on a good Rockwell tester which will for sure help!

If you want to send me coupons I’d be happy to test them for you on my hardness tester

 

[Larrin]

You need to read more about hardenability: https://knifesteelnerds.com/2019/02/25/how-fast-do-you-have-to-quench-hardenability-of-steel/

 

[HSC ///]

I almost never have warpage issues. I even make make knives as thin as .040" and ones that end up quite thin after a full flat grind (for small folders).

Granted, perhaps me using a Kool mister for all of my grinding helps somewhat as well. But whatever the case, I have never had any issues with getting rid of warpage, with a couple plates and a clamp either immediately after the quench, or during the temper.

Admittedly I haven't worked with blades longer than 4-5 inches, but I can't really see that making much difference. (I'll know soon enough because I plan to start making kitchen knives.). Also, I am just a hobbyist, so I certainly don't make massive quantities of blades.

you may find your warpage experience to be very different with a 9" thin kitchen knife..
I plate quench because it works, it works well and it's efficient and productive.

I grind all and always after heat treat just as S shqxk mentioned above,
I need the process to be repeatable and efficient. Plate quenching gives me that.

Even though I'm full time, I don't make a massive amount of blades and I don't want to.
But I need the process to be efficient and productive

 

[Mobius1]

You need to read more about hardenability: https://knifesteelnerds.com/2019/02/25/how-fast-do-you-have-to-quench-hardenability-of-steel/

I've actually read this already, and it didn't really satisfy me, to be honest, because it doesn't account for everything that matters with knife performance.

If my notes are accurate (It's a shame that Hyprefreeblades.com is gone, which is where the discussion originally took place. Thankfully I at least took quite a bit of personal notes based on what he said.), Roman Landes was saying that his heat treat was mainly targeted at improving aus-grain. Doing the whole process as quickly as possible resulted in smaller grain size, and also kept the RA "stressed" so that it had less time to become stabilized. According to what he was trying to say, many people put a lot of stock into things like hardness, but don't really think much, if at all, about aus-grain, which is often more important.

Forgive me for being so divergent over this, especially seeing as I am far less knowledgeable than so many here. It's just always been in my nature to question even firmly established views! But I do think I can say this much, after reading many many papers where experts have done real testing - It seems pretty common that the results defy their expectations!

Maybe I have no choice but to try and do the testing myself.

you may find your warpage experience to be very different with a 9" thin kitchen knife..
I plate quench because it works, it works well and it's efficient and productive.

I grind all and always after heat treat just as S shqxk mentioned above,
I need the process to be repeatable and efficient. Plate quenching gives me that.

Even though I'm full time, I don't make a massive amount of blades and I don't want to.
But I need the process to be efficient and productive

I totally get it. Clearly most knifemakers are in this camp. In fact, if we really wanted to get technical, salt baths are superior to all of the other HT methods, but is it worth the cost and/or potential danger to every knifemaker, for what might be limited improvements?

My completely personal opinion, is that if oil quenching is superior (and maybe it's not!), than I'd gladly ruin half my knives doing it (Granted, I have never ruined a single knife doing it.). I also don't like the idea of grinding on a tempered knife! Even using Kool Mist, I don't want to risk getting it too hot. This latter reason is probably a good 80% of why I don't want to plate quench. A warp I can fix very easily, but getting the apex of a knife too hot after it's tempered, I can't fix!

 

[JTknives]

I almost never have warpage issues. I even make make knives as thin as .040" and ones that end up quite thin after a full flat grind (for small folders).

Granted, perhaps me using a Kool mister for all of my grinding helps somewhat as well. But whatever the case, I have never had any issues with getting rid of warpage, with a couple plates and a clamp either immediately after the quench, or during the temper.

Admittedly I haven't worked with blades longer than 4-5 inches, but I can't really see that making much difference. (I'll know soon enough because I plan to start making kitchen knives.). Also, I am just a hobbyist, so I certainly don't make massive quantities of blades.

Length has just about everything to do with it. I never have much if any warp in small short blades no matter how I quench them. But once you get into the 9+ length it can be an issue. I have seen long thin blades come out of oil curved as much as a banana, not joking. bowing comes from uneven cooling and any stress or other things baked into the steel. A lot of times heat treatment will remove stress but if there is something funky going on inside like alabama damascus it will bow. Another thing is how are you pulling a 1725-2050f blade out of the oven and cutting off the foil and pulling out the blade without bending it. And then getting it into the oil faster then slamming it between 2 plates. I'm not saying it cant be done but it is tough and especially so with thin blades. I have some .0395 thick aebl that might change your mind about oil quenching and not getting bows lol. it's so sensitive that when I tried to gas shield instead of foil i would find weird warps on the tang. come to find out the cooling effect of the tongs grabbing them caused it to bow.

I also don't see how oil quenching on air hardening steels has so much less retained austenite then plate quenching that your that much harder. Maybe if your not giving the plate quenched blade a proper cryo treatment but that's a must for just about any stainless or high temp carbon steel. Also we know from papers and other research that you set up your toughness you want in the austenite phase. I think it was M4 i was reading about that stated that a blade austonited at a lower temp and tempered to say 60rc would be tougher then the same blade austonited at a much higher temp and tempered down to that same hardness. What i'm saying is final tempered toughness is affected by the temp it was austonited at.

 

[Mobius1]

Length has just about everything to do with it. I never have much if any warp in small short blades no matter how I quench them. But once you get into the 9+ length it can be an issue. I have seen long thin blades come out of oil curved as much as a banana, not joking. bowing comes from uneven cooling and any stress or other things baked into the steel. A lot of times heat treatment will remove stress but if there is something funky going on inside like alabama damascus it will bow. Another thing is how are you pulling a 1725-2050f blade out of the oven and cutting off the foil and pulling out the blade without bending it. And then getting it into the oil faster then slamming it between 2 plates. I'm not saying it cant be done but it is tough and especially so with thin blades. I have some .0395 thick aebl that might change your mind about oil quenching and not getting bows lol. it's so sensitive that when I tried to gas shield instead of foil i would find weird warps on the tang. come to find out the cooling effect of the tongs grabbing them caused it to bow.

I use Condursal so that I don't have to use foil. But if I used foil I'd just quench with the foil on, assuming you wrap it nice and tight (And put a little talcum powder in if you feel inclined.).

As you say, warpage is usually caused by stress from grinding, and is remedied by doing a stress relief before austenizing. If you stress relief, you shouldn't be having warping issues.

And maybe I'm wrong, but if a blade warps a lot after a quench, I personally would probably throw it away. I'd assume it only means the edge will have issues, and forcing it straight with a plate quench would only mask them.

As for the differences in hardness and toughness between the quenching methods, that I can't really say. It's one reason I made this post!

 

[DevinT]

Sounds like you already have your mind made up, you should keep doing what you’re doing.

Hoss

 

[JTknives]

I use Condursal so that I don't have to use foil. But if I used foil I'd just quench with the foil on, assuming you wrap it nice and tight (And put a little talcum powder in if you feel inclined.).

As you say, warpage is usually caused by stress from grinding, and is remedied by doing a stress relief before austenizing. If you stress relief, you shouldn't be having warping issues.

And maybe I'm wrong, but if a blade warps a lot after a quench, I personally would probably throw it away. I'd assume it only means the edge will have issues, and forcing it straight with a plate quench would only mask them.

As for the differences in hardness and toughness between the quenching methods, that I can't really say. It's one reason I made this post!

Im with DevenT, it seams like you already have your mind made up. But I will say your last post clearly made visible the extent of your knowledge on the subject.

I’m not a metal rocket scientist like Larrin so he’s the expert. And he is much better then I at letting sleeping dogs lie. Buuuuuuuut I do own a heat treating business based around custom knives. I have heat treated more knives then most people will ever see in a life time. Not trying to be mean but if anyone comes here (friends, family, exc) making claims thy need to be well read on the subject.