Normalizing

Should this thread be indexed?

  • Total voters
    43
I would buy one too - and I don't mean steal it via the Pirate Bay. As a matter of fact, that's one book we'd add into the store in a heartbeat. Hope it has a chapter on "troubleshooting". :les:
 
Kevin...

just to make sure I am with ya...

Normalizing is used to get the stress out of the steel from forging or a missed heat treat?
 
Doug Lester said:
I think we need a book called something like Metallurgy for Knife Makers by Kevin Cashen. Just a thought.

Doug
Click to expand...

I continue to work on my book which already has a catchy title not too far from your suggestion, but the current title is not set in stone. It has been at least ten years in the making and who knows how much longer it will take. You see I continue learning and every time I am made aware of how ignorant I still am it requires a rewrite of a chapter or two. I am also supplimenting it with data from my own testing a research so that It will be more than just a regurgitation of any metallurgy text already available, but sound information information by a knifemaker for knifemakers. Now if I can only stay home long enough to get it done!

Knifemaker.ca said:
.... Hope it has a chapter on "troubleshooting". :les:
Click to expand...

You read my mind... Or my notes! what have you been up to:3:! I am working on a system of step by step troubleshooting that will be an entire chapter. This is where all the folks who call me or send me an e-mail saying "Help!" have contributed to the work. I have seen just about every problem one can encounter and a few that have been really fascinating mysteries. I am working on one for a client right now that I believe I may have the solution to after several series of exhaustive tests and some time at the microscope, it sheds some light on some of the issues that knifemakers encounter when improvised techniques come up against industrial standards.
 
Leatherface said:
Kevin...

just to make sure I am with ya...

Normalizing is used to get the stress out of the steel from forging or a missed heat treat?
Click to expand...

It can, and probably should, do that, but it is actually a side benefit from the true purpose which is to homogenize or "normalize" the internal structures and carbon distribution. Knifemakers like to use the term "stress-free" when describing an ideal condition, when in fact very rarely is this case and often not what we want or are doing at all. For example in order for a blade to harden it must take on unbelievable amounts of stress, if a hardened blade is without stress... well then it can't be hard! The real trick is homogeneity, balancing all that stress evenly throughout the blade. When you get concentrations of stress, that is when you get distortion, stress risers and weak points. Even the word stress is a misnomer which I have to accept when using it to communicate to people on basic terms. What we are actually dealing with is energy resulting from strain within the steel. In pure engineering terms, stress is what we put on the steel to induce a change within it known as strain. The crystalline structures within the metal deform under this load and this change is known as strain. Areas of strain become points of higher energy in various transformations which happen in steel. For example, cold hammer entirely down one side of the blade, deforming the steel on the inside, and then straighten it cold with no normalizing heats to correct the "strain" effects. When the steel is heat treated the phase changes will occur at a different rate in the areas of strain and most likely result in a warped blade. But if you normalize after the cold working all of the deformed crystals inside the steel will be remade evenly along with the others and things will stay straight afterwards. So it is not really changing energy, as "stress" would imply, but remaking the physical conditions (strain) that result in that unbalance energy.

I can also give you numerous examples, and a few personal experiences, when grinding a machining can impart enormous strain into the metal, and often result in distortion later on. This is why grinding should be done evenly and with a sharp belt, and why I strongly frown on turning steel blue on the grinder. In my classes I always tell my students that we do not heat treat on a grinder, we save that for later. Clean cuts don't produce that kind of heat. This is also why a separate thread on stress relieving may be in order. a full normalizing could be overkill after grinding, in which stress relieving is just what the doctor ordered.

I have heard all kinds of bladesmith theories about how these issues can be all a result of forging techniques which you cannot undo once done, on and on, etc... and I am always screaming in my head "normalizing, NORMALIZING, NORMALIZING!" Countless other industries figured this out long ago and successfully deal with parts, much more complicated and prone to distortion than knives, every day. Anything done to the steel, short of fracture or burning, can be undone with proper follow up thermal treatments, once you know the mechanisms by which these things work. That is why I am such a stickler about giving folks all the boring details about why we do this or that, if you know that you can have complete control over the processes.

Hope this helps
 
Last edited:
It still amazes me that people insist that a forged blade records a history of every hammer blow that is struck and every heat it's taken to. If that were true then you couldn't relieve stress and you couldn't correct grain growth. They also tend to resent anyone trying to confuse the argument with facts. At the last knife show that I attended I sat next to a stock removal man who insisted that the above was true and further stated that he's seen forged knives that you could tell where the steel was struck with a hammer. No wonder beginners have problems separating the facts from the BS that abounds out there.

Doug
 
Doug Lester said:
It still amazes me that people insist that a forged blade records a history of every hammer blow that is struck and every heat it's taken to. If that were true then you couldn't relieve stress and you couldn't correct grain growth. They also tend to resent anyone trying to confuse the argument with facts. At the last knife show that I attended I sat next to a stock removal man who insisted that the above was true and further stated that he's seen forged knives that you could tell where the steel was struck with a hammer. No wonder beginners have problems separating the facts from the BS that abounds out there.


Doug
Click to expand...

I too am amazed at the amount of misinformation on this subject. That is why I value Mr. Cashens info. so much. I honestly believe that he would never pass on info. that he doesn't truly believe and can't back up with facts.
 
The trouble is that these other people very truly believe that what they are saying is true and they have their own set of "facts"-and sometimes their own reality.

Don't get me started.
Doug
 
Thank you for taking the time to write these heat treating posts and for letting us tap into your knowledge and experience. You mentioned that annealed stock can benefit from normalizing. What about CPM or particle steels?
 
Doug Lester said:
It still amazes me that people insist that a forged blade records a history of every hammer blow that is struck and every heat it's taken to. If that were true then you couldn't relieve stress and you couldn't correct grain growth. They also tend to resent anyone trying to confuse the argument with facts. At the last knife show that I attended I sat next to a stock removal man who insisted that the above was true and further stated that he's seen forged knives that you could tell where the steel was struck with a hammer. No wonder beginners have problems separating the facts from the BS that abounds out there.

Doug
Click to expand...

There seems to be an odd human affinity for dealing with absolutes, as if it lends more authority or weight to an assertion. There are a couple of anomalies that happen in steel that seem to survive subsequent heats but they are by far an odd exception, e.g. alloy banding, once exacerbated to the point of being visible will indeed be quite impressionable by deformation, just like a tight damascus pattern. But the greatest pitfall of ever dealing in absolutes is that as soon as one exception can be provided your position utterly crumbles; words like “every”, “always”, “never”, “forever” etc… are just setting yourself up to be proven wrong, particularly with steel. But the reason for these idiosyncrasies is for psychologists, and the morality of it is for the clergy, both are beyond my area of expertise; steel is far easier to understand and explain than the human mind.

The basic concept to keep in mind is the one I repeat in these posts- heat treating is as simple as rearranging carbon in iron and temperature is our too to do it. Depending on the temperature you go to and how fast to go there and leave, you can accomplish just about anything in steel. The trick is to work out the exact numbers for each, and the more you know about what is happening inside that steel the easier that will be.
 
Darrin Sanders said:
I too am amazed at the amount of misinformation on this subject. That is why I value Mr. Cashens info. so much. I honestly believe that he would never pass on info. that he doesn't truly believe and can't back up with facts.
Click to expand...

Darrin, folks really will never know how appreciative I am of such confidence that is expressed in posts like yours. But on the other hand I have never failed to remind people that who brings the information is always irrelevant to the information itself and the greatest reward for me is when people question what I write enough to verify it with their own research; it is then that I have done the greatest service in breaking the cycle if misinformation you and Doug mention.

My “beliefs” about my information are dangerous and I try to excise them myself as much as possible. I like to say that I prefer to save my beliefs for Sunday, the rest of the week I have to deal with steel and it doesn’t give a rip about what I believe, and I enjoy it when it reminds me of that almost every day. Facts are indeed where I am at, they are a safe bet, they are neither right nor wrong- they just are. When folks verify and question my information they strengthen it and help me stay on course as well.
 
Tiller said:
Thank you for taking the time to write these heat treating posts and for letting us tap into your knowledge and experience. You mentioned that annealed stock can benefit from normalizing. What about CPM or particle steels?
Click to expand...

An excellent question! The CPM steels have the huge advantage of not having remaining artifacts from the ingot molding process. It is unavoidable that different elements in traditionally made steel will solidify from the liquidus at different rates and create segregated networks within. These crystalline networks will be made of atoms larger than iron which, unlike the smaller carbon atoms, will be resistant to moving, making the segregation real ornery places where carbon will want to pool up. This is where normalizing can help steel right from the mill, and this will shed some light on the concept of forged blades being better; if one gets beyond the distraction of the hammer and thinks of forging as a series of normalizing heats there may be something to it.

But the CPM steels compact ultrafine particles together in a very even and homogenous way, sidestepping all the issues of ingot poured steel. All the monkeying around in forging could probably only ruin a pretty good thing with these alloys. I would even be careful with normalizing these steels as you would want to know where the carbon was to begin with before you put it someplace else. If it has been heavily spheroidized, normalizing could make the hardening operation easier, but if the carbides are already nice and fine, you would want to leave well enough alone.

On this subject, I have often encountered commonly used steels will not responding to heat treating the way users expect, with an annoying ceiling on maximum Rc hardness. Once the chemistry is confirmed metallography often reveals large carbide formations, in this case often adding a secret “special” step in the process frees up that carbon and allows maximum hardness. You probably guessed it, that the extra step is a thorough normalizing. Often the folks who had the worst problems with steel in this condition are the low temperature everything guys. Without ever going to the higher heats to move that carbon around it remains locked up and subcritical cycling only pools the carbon up even more, put more spheroidizing on top of this and the Rc will always remain in the low 60’s at best. It is just one of the reasons that I propose the normalizing could often be the most important heat treatment of all.
 
Kevin,

I am still using homemade lump charcoal for my heating and it works pretty good for...

Any tips/suggestions for those of us normalizing it old school?
 
Leatherface said:
Kevin,

I am still using homemade lump charcoal for my heating and it works pretty good for...

Any tips/suggestions for those of us normalizing it old school?
Click to expand...

Yep! Decalescence and recalescence. Watch for the endothermic shadows in the blade as the transformation is occurring on heating and get rid of them all and then heat a bit more until you have a nice even reddish orange throughout. On cooling you can watch for the bright bands of recalescence or use the magnet to see when things are sticking again before the next cycle.
 
Four pages now! I want to thank you folks for the interaction and asking of great questions here. This is the kind of information exchange that will help Knifedogs be successful and become a great resource for folks seeking this kind of information.
 
Kevin, I have a question touching on alloy banding and CPM steels-from what I understand they should be mutually exclusive. But I have seen a pattern similar to alloy banding appear in more than one bar of CPM 154. Any thoughts?
 
Just an observation about the CPM steels. These steels tend to be highly alloyed, air hardening, and have high carbide volumes, and have carbon contents comparable to cast irons. These traits do not lend themselves to hand forging. Since there is so much carbon and carbide formers, carbides also tend to form directly from the liquid as it cools, especially VC, WC, and some others if enough carbon and carbide former are present. What this means is that the carbides don't completely disolve until after the steel starts to melt. This makes a complete erasure of the carbide network impossible, which is one of the biggest reasons to use the CPM and similar processes in the first place. Steels like S30V, 10V, etc. would be extremely difficult to make in any useful form without CPM processes, which is not to say CPM is easy. What I'm basically getting at here is, based on the alloy content of the CPM steels, normalizing will not be as effective for them as for something like 52100 or 1095, both of which can have all the carbides dissolved and reformed in a finer and more evenly distrubuted manner. On the other hand, because of the CPM process, normalizing isn't as necessary either.
 
You must log in or register to reply here.
Back
Top