Triple quench secrets to be revealed?(or not)

Status
Not open for further replies.
Rick, your comments are significant, change the parameters a bit and you might change the results . However we looked at the difference of triple quench no soak to single soak and quench with the parameters we picked .Remember we started out with me asking since 5160 is said to be a steel that could be forged and heat treated easily, why a complicated triple quench .Could you get the same results of hardness and grain size with one soak and quench.I believe that this test showed we could. I fractured the samples and to get a predictable location and easier to fracture I notched the samples on three sides with a dremel cut off wheel.
 
One site indicated that
http://www.unknownplayer.com/archive/02/05/27/684.php

critical temperature of this steel "5160" is about 1550 degrees.
Click to expand...

What would be helpful here also are comments on the difference between "austenizing temperature" and "critical temperature". Critical temp being where the steel first goes non-magnetic. Austenizing temperatures can be "chosen" in some range for the heat treat. Are those "always" above critical? Why and when for what temp?
 
Originally posted by Rick Baum
Ed Fowler's name keeps being brought into this discussion as if his processes are being proven/disproven with this test. From my experiences with 5160 following Ed and Bill's instructions for forging and HT, you are comparing apples to oranges. There are a few big variables that were overlooked in this test... Was the test piece above, below or just at non-magnetic when it was quenched. Ed quenches on a rising heat just past critical (non-magnetic)
Rick
Click to expand...
Fair comment on the "disproving" thing. The experiment did get mixed in with Fowler's name, implying things, exact connections, that certainly don't exist in the experiment.

Does anyone have a material sheet that identifies the critical temp of 5160? Perhaps re-running the experiment with soak temp at that temp would be more revealing (without changing quenchant yet). (don't you love how I generously imply further use of rlinger's valuable time and talent? ;))

Rick, perhaps you could post Ed's formula for heat treating as precisely as you know it ... I've seen dribs and drabs, nothing that seemed totally definitive, although the section in Ed's book Knife Talk II seems to get a good bit of it:
from pp 114-115
The way I do [differential hardening] is using an oxy-acetylene torch to directly heat only the portion of the blade that I wish to harden to "critical temperature". (The critical temperature is the temp wher esteels become non-magnetic and will harden when quenched. I use Texaco type "A" quenching oil or a well-qualified equivalent preheated to 165deg F before quenching the blade.) By using this method, the spine and tang of the blade are never heated to critical temperature and won't harden when quenched in oil. To ensure that the spine remains soft, only the part of the blade to be hardened is submerged in oil until the entire blade has cooled till it turns black. I then submerge the entire blade in the oil and allow it to cool to room temperature.

The results of this method are very specific and dependable at providing uniform temper lines, and will enable me to specify the aspects of the blade that will be hardened. After hardening, the entire blade is tempered three times, allowing it to soak at the required temperature for two hours, then cool slowly to room temperature. Next, I cool the blades to 27deg F or less for at least 20 hours between tempering cycles. This tempering stage primarily affects only the hardened portion of the blade, as the rest of the blade was never hardened.
Click to expand...
Triple quenching is not mentioned in this section. 3 tempering steps are mentioned as you can see, but not the tempering temperature (or I need to read some more to find it). He does mention etching & brass rod testing, a 90deg flex test (bending test) in vise w/ wood blocks. Mentions not exceeding 1625 degF during forging in other chapters (called "low temp forging"), and that if heavy scale comes off during forging, "you've probably exceeded 1750 degF and are very close to the temperature where grain growth can occur."
 
Extrapolating from some tables I have handy, the Ac3 temp for 5160 is 1425-1450F. I chose 1475 to be closer to the magnetic change since many use this method ,rather than the usual recommended 1550 for hardening, and avoid any grain growth . There are lots of temperatures Ac1, Ac3, Ar1, Ar3 ,Acm ( c for heating, r for cooling [from the french]), transformation to austenite starts at Ac1 and is complete ( totally nonmagnetic) at Ac3....... The Fowler differential quench is a different story .Let me comment on this. We use this type of heat treating in industry for things like gears that are not meant for heavy service. This of course because part of it is not hardened and while this is tough it isn't very strong. Again because it's .60% carbon I'm sure that a triple quench is a waste of time ( a double quench -maybe) and a 20 hour wait is also of no benefit.
 
I also would like to see a complete account of Ed Fowlers heat treating method. I have both his books and have read all his articles in Blade but have never seen a complete from begining to end description of his heat treating method.
I also have a question for Mete. How long can a steel like 5160 or 52100 be kept at critical non-magnetic temperature before the grain begins to grow? Thanks, Tom Lewis
 
Originally posted by mete
Again because it's .60% carbon I'm sure that a triple quench is a waste of time ( a double quench -maybe) and a 20 hour wait is also of no benefit.
Click to expand...
How about for 0.98% to 1.1% Carbon content in 52100?
 
Royal 7...

I believe in his book Knife Talk, that Ed talks about a difference between his heat treatments of 52100 and 5160.

If I remember correctly it says that-

The 52100 steel is heat treated over 3 days, the 5160 does not seem to need a 24 hour waite between Heat treatments.

I also remember from someplace that Ed found that the temperings for 5160 are at a lower temp. as well as the Texaco type "A" quenching oil is not heated as high for 5160.

Ed also shows us in a knife-making film he made that he likes to only quench the cutting edge in the quenching oil.

On page 120 of Ed's new book Knife Talk II, He has a photo of the type of blade he is able to make now with a RC hardness of 60 at the cutting edge and yet only 36 at the spine with a ultra-fine grain structure of -#14.
( I have no idea what a grain structure is).
 
Royal 7, grain growth is dependent on chemical composition of the steel, time and temperature.Your question is very difficult to answer. However the recommended soak times for typical knife steels are anywhere from 15-45 minutes. Keeping at the low end of the time and temperature recommendations will prevent grain growth......Rob ,52100 is a bearing steel.It has been found that some retained austenite is beneficial for bearings. Adding a second temper reduces retained austenite and stabilizes any that remains.A third temper isn't really going to do anything and I can't remember any use of a third temper in industry......Daqotah, it's grain size not grain structure.It can be measusured through a microscope or by fracture surface.
 
DaQo'tah Forge, rdangerer and Royal 7,

The heat treatment processes (more or less) that I have been using can be found starting on page 99 of "Knife Talk". Any other tweaking to the forging and heat treating that I am doing that isn't mentioned in "Knife Talk" has been gleaned from threads here on the forum, Ed's video or were answers to direct questions to either Bill or Ed. I hesitate to list out step by step exactly as I am doing things because I don’t want to mis-represent Ed or Bill and put them or their processes (as I think I know them) in a publicly awkward situation. All that I can say about Ed and Bill’s processes, as I understand them, is that they work well. I’m very happy with the performance of my knives so far. The only other thing that I have added to the mix is a “Poor Man’s Cryo” (dry ice and kerosene). I will be experimenting with liquid nitrogen on my next knife. If Bill or Ed want’s to list their forging and ht processes for public scrutiny I’ll leave that up to them.

Mete, Do you know if edge quenching something with the cross section of a knife blade has a different effect on the grain structure as opposed to a full quench?
Rick
 
Rick , absolutely. The edge will be martensite and the spine will be pearlite, when you edge quench. In a full quench the entire blade will be martensite.
 
Originally posted by Rick Baum
DaQo'tah Forge, rdangerer and Royal 7,

The heat treatment processes (more or less) that I have been using can be found starting on page 99 of "Knife Talk". Any other tweaking to the forging and heat treating that I am doing that isn't mentioned in "Knife Talk" has been gleaned from threads here on the forum, Ed's video or were answers to direct questions to either Bill or Ed. I hesitate to list out step by step exactly as I am doing things because I don’t want to mis-represent Ed or Bill and put them or their processes (as I think I know them) in a publicly awkward situation. Rick
Click to expand...

Fair enough. My copy of Knife Talk (I) is buried in a moving box, and won't emerge onto book shelves for months (long story, renovating new/old house now).

Rick, would you be willing to post details about your modified heat treating approach here? With suitable caveats and all, like "this is Rick's way but I borrowed from others like most everyone does at some point", but including any temperatures/colors and "soak times" and such you use? Seems like Ed is (generously) willing to share details, just not where I've seen them other than the books.

I ask this out of curiosity, as I'm not a maker. I simply would like to understand exactly how these guys (and you) get such a refined grain structure, and what that translates into in terms of performance, especially edge hardness and toughness. (we can leave the spring spine vs. dead soft spine vs. full hardness debate off the table as far as I'm concerned).
 
Rick,

All temperatures were posted with the results. The target temperature for the quenching oil was 135 F..

RL
 
I am perhaps loosing my way as many of us already did. Did you smiths, wake up!

Mete said eutectic point to be 0.85 % C but my own metallurgy book says it to be 0.83, not enough, also some higly respected sources tell it to be somewhere between 0.77-0.9 !

I went to my smithy and recalibrated my sledge hammer and anvil according to the figure 0.85, the anvil horn did break!

Also
........Ar1, Ar3 ,Acm ( c for heating, r for cooling [from the french]),........
Click to expand...
seems overly difficult. For example if the steel is about 0.6 % C as we have this case, we are always over or below A3, damn Acm nothing to do with the whole matter, I guess(!)

However, metallurgy is funny, if we decide to discuss about it, couple of important interesting questions have bothered me a long time. Finally I get the answer:

I have thinking that leaving the spine totally unhardened is not good (I do not mean the case the spine is bainite-- so I probably mean it to be pearlite).

If I bend a nail (unhardened) it is stupidly easy to bend compared to even very hot tempered (blue- range) hardened steel same dimensios, I did it just for fun.

So, how can we waste our material this way, spring like spine (or even softer, not pearlite tough) is better! Why do we not harden the whole thing (smaller) and solder a piece of copper as a spine? (nice color effect too!)

Well, different tempering for edge and spine is difficult (I correct challenging) but there are means to do that.

Thanks rlinger to respect white meat!

possu (stands for pig in Finnish)
sika (stands for pig too, but a big one----perhaps I should to change my login ID)


.............
 
Pig, I think what Mete ment was 0.85% saturation. That's how I took it anyhow. I was not sure but that's how I took it.

RL
 
Rlinger, I do not know, I think both names mean the same one single damn thing......., can be wrong with advanced metallurgy tough...
Anyway, experts can explain it better.
If you are right, I broke my anvil horn for nothing, do this kind of things all the time...

One thing to be sure is that this point is too hot to my bare hands.


possu
 
Possu, I usually say about .85 but to be more precise the Fe-C diagram I have is .83%.But it's Euctectoid not eutectic ( like the difference between human and humanoid).But the important thing is that it's the point of saturation. But you have a choice in heat treating .If you started out with stock removal using a steel that was in the spherodize anneal condition and you edge hardened you would have spherodize anneal spine - not good. The same steel forged you would have pearlite spine.The same steel differentially hardened you would have pearlite spine but finer pearlite. Full hardened would give martensite spine. Know what you want and how to get it.
 
Sorry to but in again but the confusion over the eutectoid is very common and nobody here is alone in these misunderstandings.

First, the eutectic and the eutectoid are completely different points on the Fe/Fe3C equalibrium diagram. The eutectic occurs at around 4.3% carbon and 2100F. and has to do with how and when iron and carbon cool form the actual liquid state. The eutectoid ("oid" as Mete pointed out in humanoid implying that it is a eutectic-like reaction but not the eutectic) Occurs between .77 and .85 percent carbon and at around 1340F. And has to do with when all available carbon will be in solid solution in the austenite. The discrepency between the percentages that it occurs (I like to think it is .83) is due to the fact the trhe Fe/Fe3C equalibrium diagram is based upon near ideal equalibrium conditions. Any added elements that are not Iron or Carbon will change things bit, as well as heating and cooling times. Since this ideal equalibrium is so hard to achieve, different sources will give different numbers. I have even seen ASM manuals that will show it at .77 on one page and .83 on the next page!:confused:

Now I will again go about my business and let Mete do his thing.
 
Mete,
I think rlinger and I will now agree upon, even my spelling was wrong with eute- something. In fact until now, only eute-something is this saturation point.
Kevin found an other eute-somethning not discussed earlier in this thread (even almost everything probably is).

But.

I am very interested about the other problem, and believe somebody else is too. Could you comment a little bit more about "hardened and tempered a lot" versus "never hardened"- spine problem. I think that smiths want also the spine be strong not bending almost as copper (not cracking, which is good, but still!). I am seriously wondering the waste of material that way. Are there some other matters involved I do not know?
To be more specific I suppose forged blades to be in question. Must I be more specific also with "tempered a lot", roughly HRC 50, let's say. I do not mean exactly HRC 50, would it better to say "blue- range" (carbon steels). :rolleyes:


possu




----------
 
Possu, follow me. I'll try to put it all together. If you bought a hypo-eutectoid steel ( less than .85)such as 1050, It would consist of grains of pearlite and ferrite.By the time you get to a 1084 you would have all pearlite.Then you have something difficult to machine so you would generally get the steel in the spherodize anneal form where all the carbide is in the form of spheres, the matrix ferrite, much easier to machine. I would rather not have ferrite in the spine since while it's tough it's not strong. Lets leave it at that for now.
 
OK Rob, I’ll bite. Please be advised that I am very new to forging and home HT. Also, please don’t assume that any particular part of my process is exactly as Ed or Bill currently do it.

Here is a pretty much step by step process of how I forge and heat treat my blades. You will probably recognize most of the steps as Ed Fowler’s techniques as they are published in “Knife Talk I”. If you look at the index of articles in “Knife Talk I” you will notice that most of the articles that make up the book are circa 1988-1997. The article that I gleaned most of my processes from is “How to heat treat: The Spirit of the Forged Blade” and was originally published in 1992. I’m pretty sure that Ed’s approach to forging and HT have changed quite a bit in the last 11 years, especially since he has concentrated his efforts with 52100.

First I start off with a used Load Control Shaft (high quality 5160) from the local John Deere dealership. They range anywhere from 3/4” to 1-1/8” in diameter.

I forge (using a propane forge) the rough blade shape including the distal taper from this bar of steel. All of my forging heats start out slightly above critical (non-magnetic)until most of the color is gone from the steel. The scale that comes off of the steel is best described as the size of dandruff. I forge at these lower temps. to make sure that I am not growing any grain and defeating any benefits that I gain through forging. I normalize the blade at the end of each forging session.

At the end of the Forging sessions I normalize 3 more times for a total of 8-12 normalizing cycles for each blade depending on the number of forging sessions. (Normalizing for me is defined as heating to non-magnetic and allowing to cool in still air).

There usually are a couple of random quenches (in room temp. oil) of the tip of the blade during the forging sessions. I try not to get the tip overheated while I heat the thicker sections of the blade for forging.

I then anneal the blade three times. Each time I bring the blade to non-magnetic and then placed it in vermiculite to cool slowly overnight.

Next I grind, shape and polish the blade to 320 grit to prepare it for quenching.

Quenches - I bring the whole blade to non-magnetic (including the ricasso and quench approximately 1/3 of the blade in Texaco Quenchtex type A oil that is heated to 155-165 degrees. When all of the color has gone from the blade I leave it in the oil to cool to room temp. When it has cooled to room temp. I place the blade in the home freezer until the next quenching cycle. Repeat this process 2 more times for a total of 3 quench cycles.

1st temper - 2 hrs. at 330 degrees (measured by two oven thermometers in close proximity to the blade). Place in the freezer when cooled to room temp.

2nd temper - 2 hrs. at 325 degrees. Placed in freezer when cooled to room temp. I like to drop the temp a few degrees from the first tempering heat.

Cryo treatment in dry ice and kerosene for approximately 24 hrs. I figure it can’t hurt.

3rd temper - 2 hrs. at 315 degrees.

I then polish the blade to 1000 grit and etch it in a ferric chloride solution to reveal the hardening line (hammon) and surface grain structure. The hardening line (hammon) runs just into the ricasso.

I then sharpen the blade and test it for edge flexion using the “brass rod test”. I draw the full length of the blade’s edge on the brass rod 3 times on each side. (If it chips I re-temper at 20-25 degrees above my starting tempering heat of 330 degrees.)

I then re-sharpen it and test for cutting ability using 1/2” manila rope. (I’m not the best sharpener around so my results are kind of spread out).


Here is an example of cutting ability from my first forged and home heat treated blade:
First sharpening - 55 cuts before it quit shaving hair.
Second sharpening - 90 cuts before it quit shaving hair. Who knows how far it will go with a proper sharpening.

For reference I cut the same rope with a knife that I made from O-1 and had commercially heat treated to 58 rc. It only made 26 cuts before it quit. I re-sharpened and got 35 cuts.

I haven’t had my blades tested for hardness or anything of that nature, so I only have my home test methods to compare it to. I definitely can’t say that my blades are fine grained but they do give me a good point of reference to try to improve upon in the future. I’m currently working on a blade right now that will be tested to destruction. I’ll let you know how that goes if you’d like.


Rick
 
Status
Not open for further replies.
Back
Top