From the "Cold Rolled" thread came a question on these three terms. Here's what I know/found out.......hoping for input from anyone who would be so kind as to help us understand how each pertains to knives and knife steels:

Normalizing:
A Process in which an iron-base alloy is heated to a temperature above the transformation range and subsequently cooled in still air at room temperature.

Another definition: Normalizing is a process which involves heating steel to slightly above the hardening temperature, soaking it at this temerature and cooling to room temperature in air. Normalizing relieves internal stresses due to machining, forging and cold working. It removes all previous effects due to heat treatment. Normalizing also softens hardened steel and improves its machinability. However it does not result in the uiformity and degree of sortness which is produced by full annealing. The grain structure of normalized seel is generally somewhat harder, less ductile, and has a finer pearlitic grain structure that full annealed steel.

Sounded like "Stress Relieving" to me. Here's a definition for that:

Stress Relieving:
A process to reduce internal residual stresses in a metal object by heating the object to a suitable temperature and holding for a proper time at that temperature. This treatment may be applied to relieve stresses induced by casting, quenching, normalizing, machining, cold working or welding. This is done by heating to a temperature slightly below the lower critical temperature.

Read this about annealing, which sheds a bit more light on the subject:

Annealing:
A term denoting a treatment, consisting of heating to and holding at a suitable temperature, followed by cooling at a suitable rate, used primarily to soften, but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to, improvement of machinability; facilitation of cold working; improvement of mechanical or electrical properties; or increase in stability of dimensions. The time-temperature cycles used vary widely both in maximum temperature attained and in cooling rate employed, depending on the composition of the material, its condition, and the results desired. When applicable, the following more specific process names should be used: Black Annealing, Blue Annealing, Box Annealing, Bright Annealing, Cycle Annealing, Flame Annealing, Full Annealing, Graphitizing, Intermediate Annealing, Isothermal Annealing, Process Annealing, Quench Annealing, and Speroidizing. When the term is used without qualification, full annealing is implied. When applied only for the relief of stress, the process is properly called stress relieving.

You forgers, metallurgists and more knowledgeable people, can be much more enlightening than me. Straighten us out, please.

Steve,
I'll be glad to share what little knowledge I have on the subject, but I've got to think this out a bit to make it useful for everyone. You see the rules change from steel to steel, and to the desired end effect.

Also, the steps, times, and temps are quite different between the high alloy steels most of the stock removers use and the lower alloy or non-alloy carbon steels the hammer-boys use. Maybe a better idea will be to present generic information that more or less suits everybody.

I might mention that the stock removers who are buying annealed stock don't really have to concern themselves with normalizing and annealing. The high temperatures and hammering we bladesmith types use cause all kinds of havock within the structure of the steel and it has to be addressed.

If I get a chance tonight at work, I'll write something up and post it here.

Okay, here's my take on the terminology. I'll explain what they mean to me and how I do it. If anybody wants to jump in here and staighten me out, feel free. I wouldn't even pretend to be an expert.

The terms I'll cover are cycling (or thermo-cycling), normalizing, annealing, and stress relieving. Thermo-cycling, normalizing, and annealing all three have an affect on grain size. The fact that all three help reduce grain size leaves a lot of folks confused, but each has its own special contribution to the process. I'll explain this as best I can, or at least as best that I understand it. I have decided to keep things simple and generic.


Cycling
Cycling or thermo-cycling is step that I use while forging. It is similar to the normalizing step mentioned below. During forging, I will periodically bring the steel up to just above non-magnetic then quickly cool it down by waving it in the air. I usually do this three times. This is just another type grain refinement. It helps me keep the steel in relatively good shape as I go. At this point I am more concerned with controlling the grain size than the even distribution of carbon. I have seen some smiths refer to the normalizing step as cycling, and that may well be the case. I don't use the terms interchangeably.


Normalizing
The normalizing process actually is a form of stress relieving, homogenizing and grain refining, and annealing. After normalizing, the steel is much softer than hardened steel, and I do know some smiths that go directly to grinding after the normalizing step, bypassing the annealing step completely. But the main thing that normalizing contributes is an even distribution of the cementite (carbides) within the ferrite (iron).

The high temps and hammering used in forging steel cause grain growth, internal stresses, and a very uneven distribution of carbides. That is, one area may have more carbon than the area adjacent to it. The compositional differences have a direct adverse affect on how the steel will respond to heat treating. In its most basic form steel is a matrix of cementite and ferrite (or carbon and iron). By bringing the steel up to a high enough temperature, the carbon will diffuse fairly evenly into the iron, creating a homogenous piece of steel.

The basic form of normalizing is to bring the steel up to a temperaure slighty above critical and letting it cool in still air. The process relieves stresses, aids in the even distribution of carbon, and reduces grain size. A general practice among smiths is to perform this step three times. I do my normalizing in the heat treating furnace in my shop rather than out at the forge. This is because I'll have much more accuracy with the temps.


Annealing
There are many types of anneals. Basic annealing consists of heating the steel to slightly above critical allowing Austenite to form, then very slowly cooling in order to produce small grain size, and good ductility and machinability. The steel is either left in an insulating material to slow the cooling process, or kept in a heat treat furnace where slow cooling can be controlled.

Stress Relieving
As mentioned above, all the processes covered aid to a degree in stress relieving, but to me there are two processes that serve the primary prupose of stress relieving. That would be preheats and tempering.

Some of the higher alloy steels mention a preheat for some prescribed time prior to ramping the steel up to critical. These to the best of my knowledge are stress relieving heats to help relax the steel and prevent warpage.

With tempering, we all know that some of the brittleness from the hardening process is removed, and I am told that tempering also causes some retained Austenite transformation into Martensite. This would account for the apparent benefits of multiple tempers. If a transformation from Austenite to Martensite occurred then that would mean that the new Martensite would be untempered Martensite and additional tempering would be required. At any rate tempering is an important form of stress relief.

Is this any help or do we need more? I hope I didn't mess up too bad. I was sort of rushing this.

Thanks for all this information. You both have answered my initial question and a lot more. Great stuff.

Shawn

Lather, rinse repeat?

Not me Dogman. Lather, rinse and call it a day. That repeat stuff is just to make you use up the bottle twice as fast.

However, with things like thermo-cycling and tempering, there is a definite benefit to doing it multiple times.

Hey, talking about following directions like on the shampoo bottles, got me to thinking. How come the aspirin companies tell you to take two tablets for your headaches, then put 25 tablets in the bottle? It's only good for 12-1/2 headaches. On that 13th one you're out of luck.

Thank you, so very much, Terry. I was sure that someone would be able to give us the scoop. That was very well done and very helpful. We all appreciate your taking all that time to enlighten us. And it was very enlightening.

As far as going any further: I wonder, if you're not into forging and /or doing your own heat treating, if it would all compute. You know, not everything makes sense until you do it. Personally, however, it's very interesting and I'd love to hear more, if you have the time and can see the need.

Guys,

Thanks so much. Ive been trying to get a better understanding of this forever. Say, couple follow ups:

1) What about annealing in a kitchen oven, overnight for example? Does it produce different effect than the higher temp' annealing done at the forge and in vermaculite (or other)?

2) Terry, can you confirm that annealing will produce *smaller* grain size? After all, you're taking the blade to a fairly high temperature and by letting it cool slowly, you give time for grains to grow. Don't want to sound like I don't believe you or anything, I just want to make sure...

Thanks,

Joss

Joss,
Yes, the annealing heat is also a grain refining heat.

Grain growth occurs from having the steel at or above critical for extended periods. When you anneal, you are not holding the temp at or above critical. You are merely bringing the steel to solid solution then immediately starting the slow cool process. With the steel below critical there will not be any grain growth. Any hold times in annealing are sub-critical.

Thanks, Terry.

We appreciate your information and patience with us (me). I'm learning a lot.

I should mention that I of course am dealing with low alloy/non-alloy (such as 10xx series) carbon steels. I don't have a lot of dealings with the high alloy air hardening steels.

Be that as it may, your informatin is appreciated.

Maybe an SS or high alloy specialist can give us the low down?

Thanks Terry, I really appreciate the help here!

JD

Hello Gentlemen,

my name is Nate d. and i'm a metallurgy student here at UTEP, and we've just got through studyin' this in Pysical Metallurgy. I'll be glad to answer any questions anyone has on this. I'm simply givin' ya'll my $.02 worth on this, i've by no means got it all figured out. I havne't read anything prior thats too far off some of it i don't completely agree with but at any rate. But i do like most of what i've read i'lll give ya'll my version here avoiding all the nasty complicated vocabulary that metallurgists use to freak out business majors. ok

Normalizing is when i take a piece of steel and i heat in some manner to non magnetic or heat treat temp. and then i let it cool in STILL AIR preferrably on a brick. Now this normalized steel will have a fine grain and well be a little harder than annealed steel. I don 't want to go into what there is present in the grain cause that metallurgy stuff but it ain't the really hard martesite i will say that.

Annealing is when i take a piece of steel to non magnetic or heat treat temp and turn off the furnace and let it all cool down together like over night. Now this piece of steel will have a COURSE grain and be the softest of any state that i can think of. This is how i prefer to work with any damascus i make. anyhow.

Now on to stress relieving. What you are wanting to do here is um lets see here well needles inside the steel are very bad as far as stresses are concerned. and then after heat treat the steel is really stressed out and actually has expanded and this is what causes the stress, and so what we want to do is round the needle points and relieve the internal stresses. Now the following is my opinion. i stress relive at 350F and have never looked at the nicorstructure to see the amount of stress retained after a 45 min. treatment. If your stress relieving temp. is to hi your treatment is no longer stress relieving but tempering and as a result you trade off ductility for the hardness of the blade material.
ok hope this helps.

Thank you, Nathan, for your insight. Every little bit halps, and though it gets confusing, I'm starting to see how this all works.
Thanks again.