# Triple quench worth it?



## muzz24 (Jan 22, 2018)

Hi all, my first post so hope I get it right and the video works. In the video green beetle does a comparison (which he admits is not scientific) between single, double and triple quenches both with a gas forge as well as an electric kiln.

At the end of the video the steel that had gone through the process three times using an electric kiln showed the finer or tighter grain structure.

So now that I've taken the long way round explaining, is repeating the process three times to get the tighter packed grain structure worth the effort? 

https://youtu.be/CC7ndSOUEgE


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## Wdestate (Jan 22, 2018)

I'm no bladesmith but I have a few blades that were quenched like this and they have some amazing retention to them .


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## muzz24 (Jan 22, 2018)

Wdestate said:


> I'm no bladesmith but I have a few blades that were quenched like this and they have some amazing retention to them .


Yip I've made one like this and it holds a good edge but whether it's worth the extra work compared to a single quench I'm not sure.


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## Dan P. (Jan 22, 2018)

muzz24 said:


> Hi all, my first post so hope I get it right and the video works. In the video green beetle does a comparison (which he admits is not scientific) between single, double and triple quenches both with a gas forge as well as an electric kiln.
> 
> At the end of the video the steel that had gone through the process three times using an electric kiln showed the finer or tighter grain structure.
> 
> ...



I'm not a metallurgist but from my personal experience and my understanding of the scientific method, the method, and thus results (and in my opinion premise), of the "tests" done in that video are essentially useless.


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## milkbaby (Jan 22, 2018)

Why do a triple quench when you can achieve fine grain by normalizing above austenitizing temp then treating with descending heats at about aus temp then below? This has been shown multiple times by multiple people to produce fine grain. If your google-fu is good, you can probably even find the scientific rationale behind it.

Edited to add: If you do thermal cycling as outlined above, you also avoid the chances of fractures from the stress of quenching. Also, fine grain is not the be all and end all, as too fine grained lowers the hardenability of the steel.


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## Kippington (Jan 22, 2018)

I agree with milkB and Dan.
I found the video somewhat interesting, but honestly there's very little to learn from it.

The triple quench can be beneficial for people that don't have accurate temperature control because it can simulate a longer 'soak' at the correct temp, which allows the right amount of carbon to go into solution. It's trying to make up for the inability to do this by using a method that isn't as effective.
To reduce the grain size you'd have to decrease the temp for each heat cycle, which starts to cancel out the 'soak' effect.

Seriously though, a proper temperature controlled heat treatment beats doing it by eye - _every time_.



milkbaby said:


> If you do thermal cycling as outlined above, you also avoid the chances of fractures from the stress of quenching.



You don't need to do the full quench for what we're talking about here. Quenching in water and aiming for the pearlite nose (above 500°C) is pretty safe because the steel would still be austenite, and we all know how difficult that stuff is to crack...


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## RDalman (Jan 23, 2018)

milkbaby said:


> Why do a triple quench when you can achieve fine grain by normalizing above austenitizing temp then treating with descending heats at about aus temp then below? This has been shown multiple times by multiple people to produce fine grain. If your google-fu is good, you can probably even find the scientific rationale behind it.
> 
> Edited to add: If you do thermal cycling as outlined above, you also avoid the chances of fractures from the stress of quenching. Also, fine grain is not the be all and end all, as too fine grained_ forces a more aggressive quench_



Ftfy


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## muzz24 (Jan 24, 2018)

Thanks for the responses guys. I had to spend a bit of time looking up some of the stuff you mentioned. I'm going to try normalizing and reducing temp as I go. Ive just bought a electric oven so getting accurate temp is going to be a lot easier now.


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## comet_sharp (Jan 24, 2018)

milkbaby said:


> Why do a triple quench when you can achieve fine grain by normalizing above austenitizing temp then treating with descending heats at about aus temp then below? This has been shown multiple times by multiple people to produce fine grain. If your google-fu is good, you can probably even find the scientific rationale behind it.
> 
> Edited to add: If you do thermal cycling as outlined above, you also avoid the chances of fractures from the stress of quenching. Also, fine grain is not the be all and end all, as too fine grained lowers the hardenability of the steel.



Ive always had best luck with normalizing, decending thermals amd first quench. I also only do 52100 in medium speed oil, fairly safe quench &#128522;


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## inferno (Jan 24, 2018)

I have never read in from anty steel maker or in any book that a triple quench is recommended. Just do it right in the first place instead imo.
Read the data sheets, or get real books, and email the steel producers for additional data, usually whats in the datasheets is like 1/100 or so of the data the steel makers has on the steel.
And most datasheets are simply laughable.
I think this might just be mumbo jumbo, like edge packing.


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## DevinT (Jan 24, 2018)

Multiple quenches is not new, there has been considerable research on the subject. Pre-quenching has been used to refine the grain of lots of different steels. 

The most common conditions to quench from are ferrite, pearlite, martensite, or tempered martensite. The best condition to quench from is tempered martensite. It also has the most distortion after the quench causing the most risk. 

Finer grain = greater toughness = better edge holding.

Most of a steels properties come from the chemical composition, the toughness, wear resistance, stain resistance etc. will fall within a certain range. To get the most from a steel, an optimal heat treat is necessary. For every steel there is an optimum condition to quench from, the optimum temperature to quench from, optimum quench speed, optimum tempering temperature, sub-zero quench etc.

Bad heat treating can cause irreparable damage. Great heat treating takes research, practice and testing.

Hoss


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## Kippington (Jan 25, 2018)

DevinT said:


> The best condition to quench from is tempered martensite. It also has the most distortion after the quench causing the most risk.



I have no doubt you know your stuff, but I can't work out what you mean.
Are you saying that (for grain refinement) you can cool tempered martensite in a sub-critical quench? This is what I think I'm reading, but I'm not sure.

Or are you talking about quenching austenite and aiming for auto-tempered martensite?


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## scott.livesey (Jan 25, 2018)

if you buy a known steel from a known maker from a good seller, you don't need to do any of this. in the 600+ pages of ASTM Tool Steel by Roberts et al, there is not one mention of this sort of HT. this whole form of HT is backed with the same science as edge packing and molecule fracturing. if one has a furnace with accurate temperature control, properly heated quench oil, and a good watch, HT is not that hard.


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## DevinT (Jan 26, 2018)

Kippington said:


> I have no doubt you know your stuff, but I can't work out what you mean.
> Are you saying that (for grain refinement) you can cool tempered martensite in a sub-critical quench? This is what I think I'm reading, but I'm not sure.
> 
> Or are you talking about quenching austenite and aiming for auto-tempered martensite?



Oops, poorly worded. It should say condition of the steel before taking up to austenitizing. Its the phase the steel is in at room temperature prior to heat treating. Annealed steel is ferrite, normalized steel is pearlite, quenched and tempered is tempered martensite, for the most part.

Hoss


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## DevinT (Jan 26, 2018)

scott.livesey said:


> if you buy a known steel from a known maker from a good seller, you don't need to do any of this. in the 600+ pages of ASTM Tool Steel by Roberts et al, there is not one mention of this sort of HT. this whole form of HT is backed with the same science as edge packing and molecule fracturing. if one has a furnace with accurate temperature control, properly heated quench oil, and a good watch, HT is not that hard.



Which edition do you have? Ill give you a few page numbers to look at.

Hoss


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## 42537703 (Jan 26, 2018)

How about Ed Fowler's heat treating method? He does normalisation and triple quenches on 5160 and 52100. He claims that he is able to achieve ultra fine grain on these steels. By the way, he put the blade in the fridge overnight inbetween each quench. He said that the result is even better by doing so. I know some blacksmiths that use this method on 52100 and have good result.


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## scott.livesey (Jan 26, 2018)

DevinT said:


> Which edition do you have? Ill give you a few page numbers to look at.Hoss



4th in paper and 5th in PDF.


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## DevinT (Jan 26, 2018)

scott.livesey said:


> 4th in paper and 5th in PDF.



4th=537-538, 675-681, 5th=208-209

Look for grain coarsening, prequench, second quench, second austenitizing, grain refining etc.

These pages only talk about D2 and M2, the mechanisms apply to other steels also.

Hoss


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## scott.livesey (Jan 26, 2018)

DevinT said:


> 4th=537-538, 675-681, 5th=208-209
> 
> Look for grain coarsening, prequench, second quench, second austenitizing, grain refining etc.
> These pages only talk about D2 and M2, the mechanisms apply to other steels also.
> Hoss



sorta kinda maybe. 4th pg 500, not recommended for O1, O2, O7(to include 1.2519 and Blue#2) because of cracking, reduction of Ms temperature, and increase of RA. nothing about 2nd hardening mentioned for W series(1095, W1, W2, or White) or L series (80CrV2 or 52100). for M and T series, 4th pg676, "Once hardened, HSS can not be be reheated for quenching without the formation of very large grain size and 'fish scale' fractures".
as always, do what you want, you will no matter what is said or written.


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## DevinT (Jan 26, 2018)

I know you like to argue so it is what it is. If you go back and read it more carefully it says that quenching from a lower temperature first, there is significant grain refinement. Look at the graph of the D2 and M2 and it shows the different prequench temps and the grain refinements or grain coarsening that results.

With every steel, the greater volume and more even distribution of fine carbides going into hardening, the finer the resulting grain size.

Me and my son Larrin (metallurgist, PhD) have done considerable research into this subject. Industry does not like multiple quenching because it takes more time and more money. 

In the middle of the last century, they did a bunch of reasesrch into grain refinement of 52100. While Larrin was still in school getting his PhD, he had access to every paper ever written on the subject, Im pretty sure we read every one of them. Ed Fowlers claims have caused considerable controversy on the subject. For that reason, weve looked into it heavily. 

Most of any steels potential comes from the chemical make up and not the heat treatment. Proper heat treatment will maximize a steels performance.

Hoss


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## inferno (Jan 26, 2018)

What grain size reduction could theoretically be achieved compared to the "regular" methods for fine grain like using correct temps, and austenitizing with middle of the road temps?
I guess this will be different for different types of steel and possibly also different for pm/ingot/esr and so on? or?

And also is it worth it??
If yes, _when_ is it worth it?


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## scott.livesey (Jan 26, 2018)

inferno said:


> What grain size reduction could theoretically be achieved compared to the "regular" methods for fine grain like using correct temps, and austenitizing with middle of the road temps?
> I guess this will be different for different types of steel and possibly also different for pm/ingot/esr and so on? or?
> And also is it worth it??
> If yes, _when_ is it worth it?


hard to tell. i don't have the equipment to do a proper grain study, I can't imagine the cost of a metallograph with 1000x magnification. i don't have the chemicals to do a proper etch. you look at a sample that has been magnified onto a screen, draw a line 5" long that shows 0.005" of the actual sample, and count the grains the line crossed. do that with 10 different lines, then average. i come up with 8, Joe counts 9 and you come up with 10 and we are all right as the test is +/-1.0. then move to a different area of the steel and do it again. I would think at least 5 spots would need to be looked at.
use of proper temperature, verifying how evenly the furnace heats, finding the best times for your equipment, using proper quench oil, finding best tempering temperatures should be done before wandering into multiple quench. I do find it interesting that for basic high carbon low alloy steels, to include White, Blue, O1, O2, O7, 80CrV2, 52100, 1095, you start with 1485*F/800*C, minimum soak, quench in proper oil(white and 1095 need fastest oil), temper at 350*F for 2 hours and you have pretty good steel performance.


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## Kippington (Jan 27, 2018)

DevinT said:


> Oops, poorly worded. It should say condition of the steel before taking up to austenitizing. Its the phase the steel is in at room temperature prior to heat treating. Annealed steel is ferrite, normalized steel is pearlite, quenched and tempered is tempered martensite, for the most part.
> 
> Hoss



Ah that makes more sense.
I'm gonna guess that the tempered martensite is high in precipitation carbides, causing a high number of nucleation points for the new grains plus maybe some solute drag on the growing ones.
Or maybe the higher level of defect density in it lowers the recrystallization temperature...
Let me know if I'm wrong. 

Interesting that you called it 'austenised from tempered martensite'. I always considered it to be sphoroidise annealed once you get martensite hot enough to squeeze all the carbon out. I'm guessing you'd have to use a pretty fast ramp to get the most out of this kind of quench.


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## DevinT (Jan 27, 2018)

Tempered martensite has a pretty big range from normal tempering temps to sub-critical anneal. Some old metallurgists and European metallurgists sometimes use the words annealing and tempering interchangeably. 

Sub-critical annealed material is, like you said, fine spheroidite. This produces the smallest and most evenly distributed carbides pinning the grain boundaries during hardening. The finest grain is attained austenitizing and quenching from this condition.

Hoss


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## DevinT (Jan 27, 2018)

With proper prequench and rehardening, Tool Steels 4th edition shows a reduction in grain size from 12 1/2 intercept to 17 for D2 and M2 going from intercept grain size of 14 to 21, quite a reduction. (the bigger the number the smaller the grain)

Verhoeven shows that 1086, a very simple steel, going from ASTM grain size 11 down to 15 which is about as fine as one can get. 

Fracture and ASTM grain sizes closely follow the same number scale, from 1-16 or so, and intercept grain from 1-25 or so. 

Hoss


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## Dan P. (Jan 28, 2018)

inferno said:


> And also is it worth it??
> If yes, _when_ is it worth it?



I sometimes wonder if the propensity of some makers or commentators to hold forth on the benefits of (usually complicated and expensive) heat treatments might exist in inverse relation to the confidence they had in their process before they spent $3k on new HT kit? Not referring to anyone on this forum, just something I sometimes wonder.


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## RDalman (Jan 29, 2018)

I'll start doing elmax with a torch, enough to get it hard :justkidding:


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## Dan P. (Jan 29, 2018)

RDalman said:


> I'll start doing elmax with a torch, enough to get it hard :justkidding:



Do you triple quench the low alloy carbon steel you use?


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## scott.livesey (Jan 29, 2018)

only during full moon and when I have an ample supply of ewe's urine to quench in :justkidding:
I am from the opposite school. for low alloy high carbon, harden at 800C, minimum time, fast quench, low temperature temper. typical finished hardness is Rc62-64. this is for kitchen slicers and utility knives


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## RDalman (Jan 29, 2018)

Dan P. said:


> Do you triple quench the low alloy carbon steel you use?



I don't share recipes or processes I use. I do think it's always "worth it" though. I try to HT for the best performance I can, always.


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## Dan P. (Jan 29, 2018)

RDalman said:


> I don't share recipes or processes I use. I do think it's always "worth it" though. I try to HT for the best performance I can, always.



Lol Robin! I am not especially interested in *secret processes*, but can I deduce from your answer that you don't triple quench?


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## Kippington (Jan 29, 2018)

He'd tell you, but then he'd have to kill you! :biggrin:



DevinT said:


> Sub-critical annealed material is, like you said, fine spheroidite. This produces the smallest and most evenly distributed carbides pinning the grain boundaries during hardening. The finest grain is attained austenitizing and quenching from this condition.



Very interesting, thanks for the info.
Pinning the grain boundaries with precipitation carbides is something I've never thought to try, I'll give it a shot and see how it turns out.


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## scott.livesey (Jan 29, 2018)

RDalman said:


> I don't share recipes or processes I use. I do think it's always "worth it" though. I try to HT for the best performance I can, always.



why not? I will tell you the make of my furnace, where I buy my quench oil, where to buy the same tongs and thermocouples I use, the brand name of the steel and sanding belts, the total time to the second the steel is at temperature. I am always trying to pay forward for the help I received when I started.


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## RDalman (Jan 30, 2018)

Lol Dan. Kip I'm a fairly friendly guy 
Scott, because I have invested into my processes. What matters and speaks for itself is quality of product. If my customers feel I do something good, and I do something of my own, why would I give that away? There's plenty of great information out there on heat treatment, and it's better help to point to such resources which I regularly do. Whether it's "worth it" to try to achieve some specific, maybe consistent results, is up to each to decide.


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## Dan P. (Jan 30, 2018)

I would second what Robin says. The knowledge and skills a maker accumulates belongs to them.


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## inferno (Feb 11, 2018)

thats a substantial amount of reduction imo. I wonder what the tradeoffs are? if any. I'm thinking this is a zerosum game kinda (compared to by the book correct ht, conventianal way) so there must be something youre giving up by doing this. could be money only though.


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## Kippington (Feb 11, 2018)

For the most part, we're simply trying to avoid large grains. Chasing super small grain sizes is like sharpening at higher and higher grits. The *cost/time-to-benefit* ratio starts to really drop off after a certain point.
The industry has gotten grains small enough without having to chew through extra time and money to work towards a 'substantial amount of reduction'.

That being said; it's fun to mess around with, for people like me with time to waste.






It's worth mentioning that there's also the method of growing a (turbine) blade out of one single giant crystal/grain, eliminating all grain boundaries (and their problems) in the process. This seems to be the preferred method that science and industry take in some highly demanding applications.


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## inferno (Feb 16, 2018)

DevinT said:


> With proper prequench and rehardening, Tool Steels 4th edition shows a reduction in grain size from 12 1/2 intercept to 17 for D2 and M2 going from intercept grain size of 14 to 21, quite a reduction. (the bigger the number the smaller the grain)
> 
> Verhoeven shows that 1086, a very simple steel, going from ASTM grain size 11 down to 15 which is about as fine as one can get.
> 
> ...



I just read your sons larrin threads over on BF about the charpy testing. and also one on triple quenching cruforge V i think. It seems triple quenching yeilded almost nothing in the toughness department and only like half a hrc on that one. but I guess it yoeilded some kind of grain reduction. Maybe there is a point in grainsize where it simply doesn't get "better" overall? whats your take on this? Maybe its like being rich? Once you get 1 to billion then does it really matter how much more you get on top of that?


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## Larrin (Feb 20, 2018)

Kippington said:


> It's worth mentioning that there's also the method of growing a (turbine) blade out of one single giant crystal/grain, eliminating all grain boundaries (and their problems) in the process. This seems to be the preferred method that science and industry take in some highly demanding applications.


Those are made for a specific application, as the image shows they are designed for creep resistance. Having a single crystal knife blade is not something you are going to want. OK, you might want it, but that's not the point.


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## Larrin (Feb 20, 2018)

inferno said:


> I just read your sons larrin threads over on BF about the charpy testing. and also one on triple quenching cruforge V i think. It seems triple quenching yeilded almost nothing in the toughness department and only like half a hrc on that one. but I guess it yoeilded some kind of grain reduction. Maybe there is a point in grainsize where it simply doesn't get "better" overall? whats your take on this? Maybe its like being rich? Once you get 1 to billion then does it really matter how much more you get on top of that?


It could be that the grain size of CruForgeV with its vanadium addition is already very fine. Or it might be that other types of toughness testing would show an improvement but not impact testing. Or that the procedure needs to be optimized to ensure that the grain size is actually reduced. It does show that not all "multiple quench" heat treatments will lead to an improvement in properties. But that doesn't mean that an improvement isn't possible.


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## Kippington (Feb 20, 2018)

Larrin said:


> Those are made for a specific application, as the image shows they are designed for creep resistance. Having a single crystal knife blade is not something you are going to want. OK, you might want it, but that's not the point.



Hell yea I want one! What else am I going to use when even the High Speed Steels can't handle the heat in the kitchen? :biggrin:


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