Triple quench worth it?

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muzz24

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

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.
 
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.
 
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.

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...

22044904.gif
 
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 :D
 
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.
 
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 😊
 
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.
 
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
 
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?
 
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.
 
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
 
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
 
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.
 
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
 
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.
 
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
 
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?
 
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.
 
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.
 
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
 
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
 
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.
 
I'll start doing elmax with a torch, enough to get it hard :justkidding:
 
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
 
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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