Whew!, Lowell I saw your thread and thought "here we go again", since there is a whole lot of misunderstanding about that method and it often gets difficult to sort it out for many people, but your material classes served you well and you have a pretty good grasp of the general idea, and your question suggest you have some healthy doubts about some of the explanations you may have heard. Due to attempting to sort out many of the peculiar claims I have heard on this topic, I have done quite a bit of homework and research over the years to try to make heads or tails of it and this is what I have found-

You are on the right path but looking in a different direction, since it is all about carbon/iron solution. It is not that the carbon will slip out of some special state and back into solution but that it is already there. The process of hardening heats the steel from one phase which has limited solubility of carbon in iron to another which has maximum solubility of carbon in iron. In this heated phase (gamma iron) the carbon will be dissolved into a solid solution known as austenite. The levels of carbon in austenite at room temp would be a super saturated solution so under conditions of equilibrium it will go back out of solution when you cool the steel; this is why we quench it- to trap the carbon in solution under non-equilibrium conditions. Room temperature iron (alpha iron) has an atomic stacking that cannot accommodate those levels of carbon so it is heavily distorted and this distortion is responsible for the hardening of steel.

So what you have in the hardened portion of the steel is carbon that is trapped in solution; it will not need to go into solution when you reheat as it is already there.*

It is important to note the common factors with almost all the folks who find benefits from triple quenching- they very often are working with hypereutectoid steels (>.8% carbon) very often with alloying such as chrome, and they almost invariably utilize heating methods that preclude precise and controlled soak times (torch, coal forge etc…) and they often do not mention a standard regimen of pre-hardening thermal treatments.

So under these circumstances you would be working with a steel that will not tolerate overheating, but will need heat and time to get the available carbon into proper solution, time that a torch or a coal forge can’t give you at a precise steady temp. What to do? Take it in short bites that you are able to control with your methods and equipment.

Hats off to the smiths who worked out such a simple way to deal with the issue at hand, but an unfortunate error has too often been made when comparing their previous blades to their newly heat treated ones and they are a little too quick to in assuming they have found the Holy Grail of heat treating. All of us should be able to test our previous blades against or most recent ones and be pleased with our progress, it means we are still learning and improving, but it is an entirely other, and less reasonable, thing to claim we have improved on all other steel processes out there. I have researched industrial processes going back decades regarding this issue and have nothing to substantiate the claims made by guys working with the simple tools available to the average smith. I have found processes that use previous heat treatments for the purpose of carbide refinement, but none that use the methods often described my many bladesmiths, nor the results when compared to steels done in effective and controlled ways. Neither have I found instances in modern industry where they would be using these methods if it were not cost prohibitive; folks who work in aerospace heat treating say the if it produced the results cited by some bladesmiths they would be using it regardless of the cost, an yet they don’t. When we see a huge gain in the performance and properties of our blades, the reasonable thing to ask is what was wrong that we finally fixed, not assume we have revolutionized heat treating as we know it; some very sharp people have been doing this heat treating thing for a couple thousand years now so I would be very cautious with the later.

In conclusion, this method is an effective performance enhancer when getting around obstacles presented by the limitations of the bladesmith shop working with modern alloys. And if we leave it at that we can applaud its ingenuity without any reservations that come with accepting the larger claims with a clear conscience.

As for your questions on Ed Caffrey’s method with 5160, I see my good friend Ed is helping with other posts today so I will leave that portion of the question in his capable hands.

*edited to add that there is more about keeping it in proper solution on the way up with rate of heating, but how many pages do I want to type here? <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />

Kevin,

You mention:

" So what you have in the hardened portion of the steel is carbon that is trapped in solution; it will not need to go into solution when you reheat as it is already there.*

*edited to add that there is more about keeping it in proper solution on the way up with rate of heating, but how many pages do I want to type here?"

MMy question and quest to learn more has me asking: so if one performs a triple quench on 5160, forge temperature ramp rates play a vital role in keeping the hardened carbon protion in proper solution following the subsiquesnt quenches. (& initial quench too)?

Thanks

Mastersmith Cashen,

That last line is a flat out tease to a guy like me who wants to know everything he can about heat treating steel. Is there somewhere I can read up on proper heat cycling those types of steel?

Another question I had on 5160 and Ed Caffrey's method of quenching the tip for 7 seconds and then rolling the blade into the quench for another seven seconds, etc... Everything I have read prior to this on 5160 seems to indicate that the quench needs to occur withing 7 seconds to obtain maximum hardness. Ed's method would seem to leave the front of the blade hard and the flat of the blade edge softer. I don't doubt his advice or experience, I am just wondering if he chopped with the front of the blade and tested hair cutting on that area. Or, perhaps I am misunderstanding what I have been reading on 5160 and you have 15 seconds or so to complete the quench.

I know it likely won't be the answer you looking for, but the best way I can describe it is the difference between "knowledge" and "experience", or maybe a better way of saying it is the blending of knowledge and experience. I'm not trying to speak out of turn, but I get the impression that you're "knowledge hungry", which is a good thing, but I personally believe that having all the knowledge, without experience can lead you to many unfruitful conclusions. What I'm trying to say, is that if your intent is to make knives, then get into the shop and make them, and gain knowledge as you gain experience....that will allow you to more fully understand and apply all of the technical data you acquire along the way.

To try to explain the first paragraph further, the thinner a cross section of steel is (in this case the point/first 1/3 of a distal tapered blade) the faster it will heat up, and the faster it will cool down. Where as the heavier cross section (the rear 2/3 of a blade) will be slower to heat up, and likewise slower to cool down, meaning that I can get away with slightly above critical temp in the rear 2/3 of a blade, allowing it to be right at the proper temp after the tip is quenched for 6-7 seconds.

This is where we get into the "experience" aspect of it...it took me a lot of experimenting, and a lot of wrecked blades, but it works well for me, and for many who have passed their JS tests using the methodology.....I describe it in an article on my website () http://www.caffreyknives.net/journeymanarticle.html

Knowing/understanding the technical aspects of steel, and how it works with the various methodologies will often lead to discoveries that technical data and specifications sometimes cannot supply.

Guys like Kevin are at the cutting edge of the technical aspects of what we do. Whether he knows it or not, his insights and the knowledge he shares very often enable others to consider new directions and create new methodologies that when shared, benefit the knifemaking community as a whole.

Mastersmith Caffrey,

Thank you for your response. Having this level of expertise from professional smiths willing and ready to answer questions is invaluable and deeply appreciated. Being a hobby blacksmith with a wife and kids, a busy schedule and a day job leaves my shop time a precious commodity. Your article on the test blade heat treating and creation process will save me a lot of effort and failed blades. I now know where to focus my efforts which puts me a lot closer to a blade that will pass the break and edge tests.

Please allow me to add, in reference to Lowell's statement, "Everything I have read prior to this on 5160 seems to indicate that the quench needs to occur within 7 seconds to obtain maximum hardness."

This info is often not fully understood by the beginning smith, and thought to mean that the blade has only so much time to be quenched after being removed from the heat source.

Lowell, what this means is that the blade has only so much time to go from it's austenizing temp of from around 1500 degrees and get down to around 900 or so, in 7 seconds, which is the purpose of the quanchant.

When Mr. Caffrey quenches his blade tip FIRST, he is doing so because of its geometries which will allow the smaller mass of steel at the tip to cool off before the back end of the knife where it will HOLD the heat some.

He gets that thin tip down to where it needs to be, under a thousand or so, and with his expert control, has intentionally placed more heat in the thicker portions of the blade, so that after a 6-7 count of the tip being in the oil, when he lowers the rear portion of the blade, which is thicker, it is still up near the proper temp.

This works, because even after quenching the front portion of the blade, there is still enough heat in the rear portion to keep it from reverting to pearlite.

|quoted:

Guys like Kevin are at the cutting edge of the technical aspects of what we do. Whether he knows it or not, his insights and the knowledge he shares very often enable others to consider new directions and create new methodologies that when shared, benefit the knifemaking community as a whole.

Whether that be the case or not, this very useful bit of advice from you Ed should not be underestimated:

|quoted:

I know it likely won't be the answer you looking for, but the best way I can describe it is the difference between "knowledge" and "experience", or maybe a better way of saying it is the blending of knowledge and experience. I'm not trying to speak out of turn, but I get the impression that you're "knowledge hungry", which is a good thing, but I personally believe that having all the knowledge, without experience can lead you to many unfruitful conclusions. What I'm trying to say, is that if your intent is to make knives, then get into the shop and make them, and gain knowledge as you gain experience....that will allow you to more fully understand and apply all of the technical data you acquire along the way.

Many folks think that I have always just been a bookworm and am a bit of an armchair quarterback, i.e. I am good with technical metallurgical advice that lacks hands on practical application. But I didn’t even pick up my first metallurgy text until after I got my Mastersmith stamp. I had been making for over fifteen years when I started to ask questions that my experience at the time couldn’t answer.

I feel secure in saying that if I had tried to do it the other way around things would not have worked out so well. For some time now I have been handing out any technical information I can to many people who have not made more than one or two knives. This can be good or this can be bad. One example of bad, that actually scares me, are the number of new makers who tell me that they already have their salt baths built and are now asking me questions that show they actually know very little about salt baths! This is like saying you have your nuclear reactor built and are inserting the rods… now could anybody tell you how this whole “nukuler fizun” stuff works! But the allure is that salt baths will make great knives- no, only a good knifemaker can make great knives, but salt baths can make dead or maimed bladesmiths if they don’t have the skill set to use them.

Yes the technical and metallurgical end of things is the next level but a maker really needs to make it through the other levels first. Where the technical knowledge can help the new makers out there is in interpreting the process and what they see. A whole lot of bad information that has side tracked bladesmithing has resulted from misinterpretation of what we see with our own eyes or making assumptions in trying to explain it. If the new maker has some knowledge of what is happening inside that glowing steel they are much better prepared to interpret and adapt to what is happening.

But you are spot on that only experience gained through practice, and a huge bucket of trashed blades (yes we all have one or two of those <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' /> ), will allow you to make really good knives.

Now off my soapbox and back to handing out free technical information <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//biggrin.gi f' class='bbc_emoticon' alt=':D' /> .

|quoted:

... My question and quest to learn more has me asking: so if one performs a triple quench on 5160, forge temperature ramp rates play a vital role in keeping the hardened carbon protion in proper solution following the subsiquesnt quenches. (& initial quench too)?...

|quoted:

Mastersmith Cashen,

That last line is a flat out tease to a guy like me who wants to know everything he can about heat treating steel. Is there somewhere I can read up on proper heat cycling those types of steel?

Please call me Kevin, the only person who I would insist call me Mastersmith Cashen would be a PhD I made the mistake of calling "Mr." and got a stern correction about using the "Dr." they had earned, to everybody else I am just Kevin <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />, although this is the first place other than at home I have been called "a tease"<img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />

Very slow heating through the range from 900F to 1350F does put carbon in motion but it tends to ball it up in groups that are not in solution, this is how spheroidizing works. So it is important to heat quickly through this range to the temperature where you will achieve solution. An O/A torch flame is in excess of 6,000F, are you seeing these common factors appearing again? I cannot locate my papers in it, so the responsible thing to do would be to not mention it but it applies so well to this discussion, but there was a study done with 5160 once that involved the use of overheated salt baths to achieve specific properties with rapid heating.

It is worth noting that the one reason that industry has played with techniques like this is for carbide refinement, not necessarily grain refinement, or other areas that are easily controlled with conventional heat treating, for more information on this research the work of R.A. Grange and the subsequent research of C.A. Stickels. If 5160 did not have Chrome it would not respond the same since it does not have enough carbon to form carbides in a well hardened blade. But Chrome will bind up the carbon and make a soak more necessary to free it than if it were just 1060. So if you harden 5160 once with a torch and then do another blade multiple times you will probably find that the edge on the latter will hold up better than the blade heat once with a torch. Once again, heating several times at a safely lower heat is better than scorching that edge trying to attempt a proper soak with a torch.

It is also worth noting that coal forges also heat intensely fast in concentrated areas, this is why so many smiths have went to the large volume, slow heating, drum forges. It is very easy to overheat an edge or a tip, and I won’t ever get into scaling and decarb, so it is more desirable to many to limit the time at temperature in a forge, so they adapt their procedures to how they do it.

One can start to see why there are as many heat treating recipes as there are guys heat treating <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />. That is why I am not a fan of recipes, but prefer to fill people’s tool boxes with what they need to write their own recipes.