Triple quench secrets to be revealed?(or not)

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Dave did it again!
There are a few too kind persons on this forum. Dave Larsen and John Andrews first in my mind.

Dave is saying nice things about my knifes. In fact I think I have some good designs, but I can't do perfectly finalized knifes to the last detail (as Dave and many others do). This is only good because this way I have lot of interesting learning ahead (and I am not trying to get my living making knifes).

John Andrews once did send me a post asking am I all right, when I was a long time away from forum!

Link to one of my pictures:

http://www.evitech.fi/~tk/3.jpg


Thanks Dave: pig
 
Hey Pig, very excellent topic. Thanks!

Yes, I have often wondered the true value of a triple-quench, and even the triple temper. Seems like myth and mysticism attached to what really is a simple chemical property of the particular steel we are using.
 
Smiths love mysteries. I think that it is due to the fact that from ancient times human people have been thinking that there are four basic elements: fire, earth, water and air.

Smiths are connected to this tradition:

(fire- heating steel)
(earth- steel and carbon)
(air- keep the fire)
(water- quenching)

Old phrase:
Of the elements, air, earth, water and fire, man stole only one from the Gods. Fire. And with it, man forged his will upon the world (Anonymous).

This seems really talk of a mystery lover!

I think I have created some wrong ideas with my talk. To be more clear:

I have just a theory. A theory is quite different thing as a true fact!!!!!!

A theory is fact only after it is proven. I hope proof to my theory (a planned controlled test).

I do not think that we can solve every problem ever. But if we have a logical contradiction so that fact x is proven to be right and proven to be wrong same time, we can do and should do something.

I do not either agree with metallurgists with all things as "hammering do not help to get better blade", because I have myself experimented this.

On the other hand we can use sometimes the knowledge of metallurgy.

It is nice to know exactly (at least to me) for example why we need high carbon steel for razor, even tradition suggest us to use it without any scientfical facts.

(As to tempering many times (I do not know about 3 but at least 2), it is accepted and explained also by metallurgists)

pig
 
Pig, maybe there has been something lost in the translation or a misunderstanding. Let me restate things. A proper soak time is always important otherwise you will not get full hardness of the martensite. A .60% C steel will need less soak than a .85% C since the .60% has less carbon. A .85% will have about the same soak time as a 1.00% C because at .85% saturation is reached and no further carbon can be dissolved. And I must restate that a proper soak will be complete before there is any fear of grain growth so it would be better to soak more than necessary rather than to try to get the absolute minimum, especially when so many smiths don't have the most accurate temperature control.
 
Thanks mete,
as I did say I am not a metallurgist and I hope that nobody thinks that I pretend to be.

However, what I did mean that soak time is not "so important" is that if the soak time is not perfectly correct we get decent knife but if we overheat (old methods, not oven, this is easy) we can completely ruin the blade. So I did even before mean that soak time is important to make a superior blade but not to make a some kind blade.

If fact also I was not trying to talk about amount of soak times but about that if we have lot of carbon in the steel we do not need it hungy for example Cr- carbides to create martensite and are able to keep wear resistant carbides if needed. And if we do not need carbon from Cr- and V- carbides we do not need so much heat and time?

Anyway, I do not know am I righ even with this, am I?


I did say earlier that mill specs do not always tell about the proper soak time. Am I right? How to find some collected information about soak times? Have you any? Or what about a some general guidelines of the proper soak time according to steel type? Early I did say: "I do not know is the low bound of 52100 2,3,4 or 5 minits".

I am fully aware of my limited metallurgy knowledge. But I did start the discussion because many observations did seem to support "my theory" and triple quench problem is really funny to try to reveal from the dust of mystery.

I think some collaboration with metallurgists is invaluable to smiths, not to take "a fighting standpoint".

Many thanks once more to mete to tolerate "old mystery black dirty workmen"!


pig
 
Pig, alloying elements do more than one thing . Chromium for example will form carbides but some of it will also be in the martensite strengthening it. Regardless of which carbide or mixture of carbides the carbon comes from we must have enough soak time to dissolve carbides and saturate the martensite. We want a matrix that is also homogenious as far as carbon content. Steel suppliers or mills can give you details of heat treating .I just bought my first knife of S30V, and looking at the specifications from Crucible Steel they recommend a soak time of 15-30 minutes. I would expect that steel, since the carbides are smaller and more numerous would have a shorter soak time than if it were made in a conventional way. S30V is a CPM steel ( Crucible Particle Metallurgy). Anyway when you look at the 15-30 min recommendation do you see why I get nervous when someone says 5 minutes ?
 
Thanks mete!
However, your answer was not what I was aiming to. Now you talk about fancy CPM and give (a correct) very high soak time.

This presents a problem. The blade smith work started with carbon steels (short soak) and continues also often with low alloy steels as 25100, 5160 ...(short soak).

If we give as an example only very high soak time (CPM), smiths think we are talking nonsense as a whole. They have got good blades with short soak times with steels they have used so far!

For this reason I must say that according to my best knowledge also metallurgists accept a short soak time as 5 minits for bare carbon steel and also low alloy steels as 52100.
Also thickness of the material may have a role.

pig
 
Pig, Crucible also gives soak times of 30-45 min for D2 ,A2 and 30-60 for 154cm. I find the comments of Kevin McClung on heat treating of interest. He illustrates the difference between the science of heat treating and other methods . www.mdenterprise.com/articles.htm. After all they used to quench in the body of a slave or in the urine of an unweaned goat taken at the full moon. The finns probably did it with reindeer urine, right ?
 
PIG,
Very interesting thread. It raises a question in my mind... It would be interesting to see if there is a difference in performance between a single quenched blade with a soak time and a triple quenched blade with the same soak time prior to each quench. Another question that I would have in regards to this experiment would be... How is the overall perfomance affected by the soaking? In other words, Ed Fowler uses a torch to bring just the desired portion of the blade to critical leaving the spine below critical. By soaking the blade at temp., the whole blade is at critical prior to the quench. Will this have an effect on the toughness (flexibility) of the blade in a positive or negative way? The reason that I ask this question is because my first forged blade was not heated with a torch to isolate the edge from the spine in regards to critical temp. prior to the quench. It was heated in the forge which caused the whole blade to reach critical before I quenched it. Being my first forged blade, I tested it for edge flex and edge holding but did not bend the blade (I'm kind of sentimental, and wanted to keep my first forged blade). The blade performed very well as far as I tested it, but I have always wondered what the difference would be in flexibility if just the edge had been brought to critical instead of the whole blade.

Rick
 
To Rick Baum: An important quesion. Very many new topics involved. I think (I/you) should open a new thread soon.

To mete: I admire your good sense of humour! I am not too serious either, because I am only a hobby smith for fun.
I also know that earlier swords of kings were quenched into a slaves belly (a nice idea about salt water- not to the slave stil).

For more serious readers I must say that you are not answering to my question about 52100 but listing more super hyper fancy fasionable steels.

Unfortunately I do not know about the reindeer urine quenchig. Must try sometimes. I use mostly polar bear urine, because many bears use a bucket outside my forge to get relief (bears are tidy and walk far to my house).


pig
 
Pig,

To add some in-shop perspective to the soak time importance:

I soak 1045 for 10 minutes, just barely above Ac3, then it gets quenched. I get a hard, fine grained blade that performs superbly.
S90V I soak for 30 minutes on the lower end of the austenitizing temps, but the entire HT includes a pre-heat and a smooth, nicely timed and gradual ramp to final aus temp. Aus temps are accurate +/- 3°F. I give a +/- 5° leeway (sp?) for tempering.

Prior condition also effects things: My 1045 is fully annealed by myself after forging, befor final HT as where S90V remains spheroidized annealed straight from Crucible, before final HT.

Just some things that come into play. :cool:
 
RE: Soak times on data sheets.

I 'believe' that listed soak times on data sheet assumes a 1" cross section. It makes sense that they would have to assume some thickness.

Therefore, if Crucible listed 30 min soak on 1" material, then 7.5 minute soak would work for 1/4" material.

Yes? No?


The other possibility is that soak time is listed AFTER the sample has reached temperature. In that case we should have to know the thermal properties of the steel to know how much time to add. In this case, if Crucible listed a 30 min soak time, we would have to have an oven time even longer! And that doesn't jive with the results bladesmiths give.


Steve
 
Pig and Jason, I've been searching for the info but can't find it .But Jason's info is usefull. If it takes 10 minutes ( Ac3 - 1440 F ) to soak 1045 ( starting with pearlite ? ) it would take longer with the higher carbon 52100 ( Ac3 - 1440 F ) higher temperatures of course would reduce soak time. Rick - I would much rather see you bring the entire blade to full temperature then either differentially quench or differentially temper.
 
Hi this is DaQo'tah

I have been reading everyone's post from the first when the topic was started. This topic is very very important to me,,,I want to know what you guys think is the best way to heat treat 52100 and 5160 steels that I use. However, most of what you guys are talking about is way over my head.

I only have a coal forge to heat my steel, I do have a torch to heat treat as Ed Fowler has showed how to do....and there is no way i will ever own a knife making oven that can reach 2000 deg.

so,,,,is the way I heat treat, (3 times over 3 days , heating only the cutting edge) worth the trouble?

if you dont think so,,,,(given my lack of a knife oven) what would you suggest I do?

I seek to make a good knife, that holds an edge a reg. amount of time, but I need to be sure my knives can never break,,,,,I need to be SURE that that cant break!

suggestions?
 
Crucible gives the critical temp of 52100 as 1385 degrees F. they also recomend a 10-30 minute soak time saying to use the higher soak times for oil or vacuum hardening and the lower soak times for for water hardening. They also say that the steel should be brought to 1200-1250 and equalized then raised to 1500-1550 and the soak time started. use the higher temps with the longer soak times.

Rex Walter has done some testing as to the triple quench, in which he took a piece of 52100 with a cross section similar to that of a knife blade. He heated it to critical and quenched imeadiately in Mobile Vactra quenching oil and then tested it. The rockwell (64-65) and the amount of carbon loss due to heating >.0002 and grain size about 10-12, ( very fine by industry standards). He then repeated the test and found that although the the grain size was now 12-14 the hardness was very uneven throughout the steel and varied by as much as 15 points. The test was repeated a third time and the result was a steel with very even hardness (65+/- .5) with grain size that was off the scale 14 and smaller. carbides were small and very evenly distributed through out the test piece. Total carbon loss was was less than .002 for all three heats and there was at least a 99% transformation with no retained austenite.
this was all done with less than a total five minute soak time for all three hardening cycles.

I may be a little off on some of my numbers so I will dig through my stuff and find the paper that Rex sent to me and review them and edit this post to make any needed corrections.
 
DaQo'tah,

You'll have to experiment to see what works with the equipment you have available. No matter what information you get that gets you started, there's no substitute for testing your own blades.

That said, I have a couple suggestions. You can heat treat 52100 with a torch but it's dicey work and Ed Fowler has worked for years to get consistency with a torch and I'm sure he can do it well. But, it's not easy to do with a steel like 52100 that's picky about temperature. One idea is to place a heavy steel square tube in your forge. The tube needs to be longer than your knife. Build your fire so that, if possible, the hot spot is as long as the tube. Put your knife in the tube and let the whole thing come up to temp slowly. Presto! Your very own 2000 deg oven!

At first, you can check the blade with a magnet as it comes up to temp, but you will soon be able to see the color change when it reaches critical and be able to identify the temperature of the knife from that.

By doing it this way, you are more likely to have consistent results. When you start testing your blades, it will be easier to make small adjustments to temperature or soak time.
 
mete,

Yeah, your 1045 info is right, prior would be coarse pearlite. Well that and proeutectoid ferrite mixed in as well.

itrade,
Yes, cross section does play a big part. That whole balance thing. High alloy steels though, do need a little more time to put the essentials into solution. So, a smaller "scale" to balance things on. I hope I'm making sense? :cool:
 
This is a very good thread. Although I have been too tied up in other directions lately to keep up with it completely, I have been pretty much following what mete has said here. Maybe its just me but all he says makes sense. RL
 
Bill, Good to know that you are still alive!

Did Rex compare the triple quenched "blade's" numbers to a textbook quench with soak times? Seems like that would clear things up nicely for everyone. If you get a chance maybe you could direct Rex to this thread.

Mete, Why would you rather see me bring the whole thing up to critical rather than differentialy quench or temper? Do you mean to bring the whole blade to critical and then edge quench rather than just heat the portion of the blade that is to be quenched? Just curious. I don't want to sidetrack this thread. Maybe you can email me unless it has a bearing on the original subject.

Rick
 
I will again tank to all participants to my thread!

Most of them are more experienced smiths than I am. We are perhaps, however, getting too many details and going too far from the initial point forgetting it (, even all new details and info is invaluable).

My initial idea really was to ask: Can we prove by test that proper soak time can replace triple quench with 5160 (Ed Fowler used)? Or is it the case nothing can't?

Really any reasoning or talk can't replace real controlled reliable test!

Ed Fowler is an highly respected name (by reason) and as far as any other method is not really proven to give similar results as triple quenching almost nobody (smith) will trust on the possibility (and for a good reason by the way).

One more argument to get you believe this is that Ed Fowler do not even bother to participate this kind of pure speculation.


pig
 
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