View Full Version : Normalizing after stock removal?


rhrocker
07-04-2004, 10:51 AM
Should steel be normalized after stock removal? In other words, will steel that comes from the factory, already annealed, and then ground into a blade, suffer some form of grain growth from the grinding, that would benefit from the normalizing cycle(s), before heat treating?

Kevin R. Cashen
07-04-2004, 12:03 PM
There will be induced strain from the coarser grinding belts, and if you have a tendency to turn the steel blue (as we all do some times :o ) , you just might get some affect during the heating to quench (austenization). Nothing you do below around 1350F or higher (quite a bit higher) will grow grains. Induced strain can affect how the grains will recrystalize when that temp is reached, but if your grinding was even ... ;)

Normalizing, I think, could be overkill after the grinding. If you are really worried about it, a quick stress revlieving operation could be in order. Just heat to around 1000F and let it air cool. This should zap much of that residual strain.

If you wanted to play with different grain refining techniques (normalizing) I personally would do it to the raw bar, before the grinding and then spheroidize. But then this could be easier said than done depending upon your alloy.

rhrocker
07-04-2004, 02:43 PM
Thanks Kevin, appreciate your input on this!

AwP
07-04-2004, 03:38 PM
...will steel that comes from the factory, already annealed...
Normalizing, I think, could be overkill after the grinding.

Besides the whole stress relief and grain reduction points, I thought annealing could tie up alot the carbon into carbides, making it more difficult to harden a blade without a longer soak to make sure all the carbon is back in solution? While a longer soak would fix it, it also opens the door to grain growth if you don't have good temperature controls. Maybe I'm misunderstanding the finer points, but the way I see it is that normalization doesn't hurt and often helps, so you might as well.

Kevin R. Cashen
07-04-2004, 03:43 PM
Long complex annealing (like speroidizing) on richer alloys can tie up carbon and necessitate longer soak times, but simple lamellar anneals that can be used on shallow hardening steels don't affect things that much at all. Lamellar pearlite, particularly the fine stuff goes, into solution rather quickly.

AwP
07-04-2004, 04:03 PM
Is a lamellar anneal the sub-critical one? That's basically just tempered as much as it can be to make it fairly soft, right?

Kevin R. Cashen
07-04-2004, 07:07 PM
The lameller type annealing is the stuff that most bladesmiths do, that is, heat to nonmagnetic and then stuff in wood ashes or vermiculite. The subcritical operations would include spheroidizing. What it comes down to is if you go above critical and form austenite, that austenite will tranform into either coarse or fine pearlite (depending on the rate of cooling) when it cools. If you stay just below critical and do not form austenite the carbides will start to "pool' up. Above 900F, this will form spheroidal cementite, and the previous austenite grains will be untouched if it stays below 1350F, but it will take a longer soak to pull such widely seperated carbon back into solution.

In very general terms: 350F-800F= tempering, 800F-1000F=stress relieving, 900F-1325F= spheroidizing.

AwP
07-04-2004, 07:45 PM
Ok, I think I got it, thanks.

rhrocker
07-04-2004, 08:09 PM
I guess what I need here is a deffination of spheroidizing in laymens terms.

Hot&CoaledForge
07-04-2004, 08:16 PM
Found this, Robert:

Spheroidizing is a process in which most plain carbon steel are heated to 750 to 760 0C for one to four hours and slowly cooled in the furnace. (Higher spheroiding temperature is used for other alloys.) When the materials is subjected to spheroiding treatment, round or globular form of carbide is produced within the microstructure. Carbides are phases in the steel that are very hard. Many tool steels are subjected to spheroidizing treatment in order to improve their machinability.

http://www.eng.ku.ac.th/~mat/MatDB/MatDB/source/Proc/heat/treatment/treatment.htm

- Jim

Terry Primos
07-04-2004, 09:35 PM
Robert,
In real simple terms, here's what's going on.

Steel in the simplest form is a combination of iron and carbon. In its softened state, the base is a matrix composed of simple iron molecules (ferrite), in which are suspended molecules of iron carbide (cementite)

As Kevin stated, if you stay below what we bladesmiths call "critical", and do not form austenite, then the carbides will begin to pool up together into little globules (or spheres), hence the name. What this does is leave larger spaces (or areas) of the softer ferrite. That's why the spheroidized steels are easier to grind, drill, file, sand, etc.

rhrocker
07-05-2004, 12:09 AM
Great! Thanks guys! I also re-read Kevins great sword making tutorial real quick and found this:
"What this speroidal anneal does is causes the cementite (carbon) in the steel to gather together into an evenly dispersed collection of spheroidal globs. In this state the carbon is not interacting with the iron to give me any grief from stress or hardness and the metal will be very easy to machine, grind or shape. "
So now, between the three of you guys, plus Fitz's PM, I'm up to speed! Many thanks!

Kevin R. Cashen
07-05-2004, 10:55 AM
With the steels that I work with I have found spheroidizing to give the softest condition in the steel of any treament. It is always neccesarry for me to switch indenters and go to the "B" scale to get a rockwell reading from the stuff. Little spheres in a soft ferrite matrix move around a whole lot easier than layers or sheets of cementite and ferrite (as in pearlite). In fact I have become convinced that I do not get the life out of my zirconia belts that I could, because the speroidized material just doesn't fracture the particles as well. I have noticed a difference on harder forms.

You can spheroidize by holding at a temp below 1350F long enough for the carbon to ball up. There is another way that I have used, that is common in industry, in which the steel is heated just a hair above 1350F and held for a short time to let the carbides disolve and then the work is cooled VERY slowly through the transformation range causing the stuff to really ball up. This also does not affect austenite grain in any way and produces the most spheroidal condition, but is also involves more decarburization and requires very good temperature controls.

HEY! I have never posted this often to any thread on CKD :D . It think this forum is going to be a very good thing!

Quenchcrack
07-05-2004, 01:29 PM
There are some things about the iron-carbon phase diagram that appear to be misunderstood by a lot of people. First, no molecules in metals. Metals form crystals, not molecules, and the crystals are made of metallic atoms or alloy atoms. Second, austenite forms over a range of temperatures. Only at the eutectoid composition (.78% carbon) does it form at exactly 1333F. At all other carbon levels it forms over a temperature range that is up to 150 degrees hotter than the Curie (non-magnetic) point. Third, ferrite has a very low solublity for carbon. If you do not fully austenitize the steel, the carbides will not totally dissolve. Annealing at a temperature BELOW the fully austenitic temperature relies on DIFFUSION of carbon which is very slow at that temperature. Annealing ABOVE the fully austenitic temperature allows the carbon to dissolve into the austenite and diffuse more rapidly due to the slightly larger inter-atomic distance of face-center cubic austenite. I think there was a few more points I saw in the previous posts but, mercifully, I have forgotten them and will shut my cake hole now........... :o

Terry Primos
07-05-2004, 03:00 PM
Quenchcrack,
For goodness sake, DON'T shut your cake hole.

Yes, I remember from another discussion that I was not actively a part of, the point being brought up that with steel we are dealing with crystals and not molecules.

Shoot man, I have no problem being corrected, and in fact am grateful for it. When I participate in threads, I am not presenting the information as an expert, but rather as a layman who is explaining things as best I understand them. So I am not offended at all when corrected.

I believe that you will find about 999 out of 1000 members here will have the same attitude. We're all in this together, with varying degrees of understanding and expertise. By being corrected, we all benefit.

Let the discussions resume! :)

Quenchcrack
07-05-2004, 04:05 PM
Terry, You are a gentleman! I see so much confusion and misunderstanding about heat treating I can't pass up the opportunity to help set the record straight. I will readily admit to being a very unskilled knifemaker, however and hope to trade what I know about heat treating for some help in making a better blade. I sold my knife grinder several years ago and the only blades I make now are replica trade knives for buckskinners and trail riders. I can pretty much forge them to shape without grinding.

Spent the afternoon at the forge today but made BBQ tools instead of blades. For the time invested, I can make more $$$ on fireplace and BBQ tools than on knives.

SteveS
07-05-2004, 05:08 PM
Just a quick AMEN to what Terry said.

All of us are some where on a continuum between none and complete understanding.

I know a little more than some just behind me and I might attempt to explain what I know - if I think I can. We certainly don't want the professionals among us to spend all their time answering every question.

However, when I'm mistaken I too very much appreciate the correction.

Steve

Kevin R. Cashen
07-05-2004, 08:17 PM
There are some things about the iron-carbon phase diagram that appear to be misunderstood by a lot of people. First, no molecules in metals. Metals form crystals, not molecules, and the crystals are made of metallic atoms or alloy atoms. Second, austenite forms over a range of temperatures. Only at the eutectoid composition (.78% carbon) does it form at exactly 1333F. At all other carbon levels it forms over a temperature range that is up to 150 degrees hotter than the Curie (non-magnetic) point. Third, ferrite has a very low solublity for carbon. If you do not fully austenitize the steel, the carbides will not totally dissolve. Annealing at a temperature BELOW the fully austenitic temperature relies on DIFFUSION of carbon which is very slow at that temperature. Annealing ABOVE the fully austenitic temperature allows the carbon to dissolve into the austenite and diffuse more rapidly due to the slightly larger inter-atomic distance of face-center cubic austenite. I think there was a few more points I saw in the previous posts but, mercifully, I have forgotten them and will shut my cake hole now........... :o

To be even more precise, BCC ferrite (alpha iron) has a lower solubility for carbon; gamma iron easily takes much more carbon into solution. Austenite does form over a range, as Ac1 is a straight line across the iron-iron carbide phase diagram. Acm and A3 define the upper limits of their respective fields and thus form the range at which varying degrees of austenite solution is achieved. The Iron-iron carbide phase diagram is only applicable to ideal equilibrium conditions, and the eutectoid, depending upon the particular diagram you are looking at is a percentage from .77% to .85%.

Almost all steel transformations (with the exception of ones such as the martensitic transformation) are diffusion dependant. This would include those below Ac1 and those above it; the temperature just accelerates the rate of diffusion, due to the inter-atomic FCC spacing that you mentioned.

Below Ac1 is indeed slow, but one can play with the times a bit by starting from different microstructures. Spheroidizing martensitic steels is a much quicker process than other structures that require more diffusion.

Kevin R. Cashen
07-05-2004, 09:00 PM
Quenchcrack is correct in pointing out that there is often confusion regarding the Iron-iron carbide equalibrium diagram. It is often refered to when few have access to it visually. I happen have a version of it on my site that I was using in another discussion, involving the eutectic vs. the eutectoid, so I thought I would post it here in hopes that it could be helpful. just ignore the red arrows I added for the the other discussion.


http://www.cashenblades.com/FeC.jpg

Quenchcrack
07-06-2004, 01:07 PM
While admitting that the Fe-C diagram is good only for eqilibrium conditions, we should also remember that it is only for Iron and Carbon and the effects of all alloys and residuals is not reflected. I remember my course in Ternary Metallic Systems and I don't want to go there again! I sort of agree on the comment that almost all transformations are diffusion dependant. All except the one ones that aren't, like Widmanstatten Ferrite (shear and diffusion), Bainite (shear), Martensite (shear). That leaves carbide precipitation either in pearlite formation or in tempering as being diffusion phenomenon. Without resorting to a technical debate that would probably bore most readers, please remember what my objective was: Annealing is not the same as normalizing. It is not interchangeable and may do no good at all prior to hardening. Heating to just non-magnetic may or may not get the steel fully austenitic, depending on the carbon content. If I offended someone or came off as being a know-it-all, please accept my apologies. This forum clearly has enough metallurgists to tend the flock and perhaps my contributions are better made elsewhere.

AwP
07-06-2004, 02:12 PM
This forum clearly has enough metallurgists to tend the flock and perhaps my contributions are better made elsewhere.

Don't be silly, when you professional metallurgist types get into a contest on who can teach the most knowledge, there are no losers. It just spurs you both on to dig out even more info to share.

rhrocker
07-06-2004, 02:59 PM
Hey guys, I'm really enjoying this, and very glad I started the thread, it's gone WAY beyond where I thought it would go, and I for one appreciate it! The expertise we are seeing here is absolutely unreal. Many thanks to all who are participating, and all who are benefiting. Speaking of the Widmanstatten pattern, I'm holding in my hand right now a 4 billion year old (and no, I have no idea how they know the age) Giobeon meteorite from Namibia. Is thought to have hit the earth several thousand years ago, the meteorite strewn field was discovered by a Capt. J.E. Alexander, in 1838. I have two large slabe, that will yield at least four bolster, plus I have a 5 pound bag of meteorite powder (approx 7.93 Ni, .41 co., .04 P, 2.0 ppm Ga, .12 ppm Ge, 2.3 ppm Ir, the the remaining 90 persent (+) is Fe. I'm going to make a canned mosaic from the powder, using a combo of it, and some more "earthly" metals. Just HAD to mention that since Robert said the word Widmanstatten. I'm pretty excited about it. Will post a photo later of the etched piece if anyone wants to see what that pattern is. Again, thanks for the help guys!

RJ Martin
07-06-2004, 03:57 PM
I have been watching this thread closely as well. Some interesting points made here-I am impressed with the phase diagrams for sure!
Still, I am not sure where you guys are with an answer to the question-Stress relieve after grinding (1000/1100F) or anneal, or no treatment at all?

One question I have-Do you guys worry about Carbon loss during these long soaks/cooling cycles performed in a forge? I'm sure you can minimize it, but, I don't even like annealing in my furnace in a protected environment.........

My vote is for a 1-2 hour soak at 1100F after grinding. Safe, yet effective.

What do you guys think?

PS-Quenchcrack, this forum is for the exchange of ideas-Please don't worry about egos when you're stating facts!

Kevin R. Cashen
07-06-2004, 04:09 PM
... remember what my objective was: Annealing is not the same as normalizing. It is not interchangeable and may do no good at all prior to hardening. Heating to just non-magnetic may or may not get the steel fully austenitic, depending on the carbon content. If I offended someone or came off as being a know-it-all, please accept my apologies. This forum clearly has enough metallurgists to tend the flock and perhaps my contributions are better made elsewhere...

No, no, not at all. You misunderstand me Quenchcrack, or I misunderstood you. I took your original post as a hint to be more specific and thus a little more accurate with my terms. I am sure you well know how difficult it can be trying to walk that fine line between accurate tech talk and not going over the heads of many aspiring knifemakers. Less technical terms are easier to understand but do tend to lose their accuracy.

I would like to thank you for pointing out the oversight that this thread kind of got side tracked, as far as annealing versus normalizing. You are very much correct in reminding us that annealing IS a softening operation and normalizing is equalizing/refining, regardless of hardeness (when I normalize L6, it hardens to 61 HRC) . It is very much worth mentioning that most folks in industry find what bladesmiths call "normalizing" resembles very little what they know as such. To meet the true and exact definition of normalizing we really need to go to a complete austenitic state and this "dark red" or "barely critical" stuff doesn't seem to fit. Other than "thermal cycling" or "stress relieving", I think we resort to calling it normalizing for lack of a better term.

Keep up the good work, feel free to keep me more accurate, and in no time at all we should have $5 words used with ease here ;) .

SteveS
07-06-2004, 05:09 PM
rhrocker,

Me, humble pie Steve, will give you my 2 cent description and methods:

RE: Stress Relief

I've taken to stress relieving my S30V after grinding and before hardening. You see, on warped blades I do a full anneal and re-harden. That is a Veeeerrry long and $$ process. So if a stress relief reduces the chance of warping....

On that steel, I use 1200 for 2 hours then oven cool (as per Crucible).

RE: Normalizing for grain refinement.

I'm of the impression that CPM steels as they come are as fine grained as you need for hardening. Now if you were asking on carbon steels. I would normalize first. A full anneal creates large grains. That is not the optimum condition prior to hardening.

So, carbon steels I normalize first.
High Alloy steels I stress relieve first.

(Boy I sure hope I'm doing it right.)

Steve

rhrocker
07-06-2004, 07:38 PM
Hey Steve, thanks. I'm saving up all the valuable info here, on and off topic, this is quite a help for us all. BTW, yesterday I made your convex grinding rubber mouse pad graphite gizmo for my KMG, and used it today, Nice! Thanks for that tip also!

Quenchcrack
07-06-2004, 07:44 PM
OK. As long as I haven't P.O.'d anyone.

As far as the 4 million year old asteroid goes, the dating process is really quite simple. They know it is 4 million years old because they found it in a 4 million year old bed of rock. They know it was a 4 million year old bed of rock because there was a 4 million year old asteroid in it.

Stress relieving after grinding: Basically, the stress created by grinding will be limited to the disturbed layer of metal. I would guess this to be .010" or less but a lot more if you have been hogging metal off like you worked on Junk Yard Wars. I think you could get this taken care of with the 1100F for an hour or two as suggested.

Carbon loss during long soaks: I don't have my little heat treating book with me but I believe the diffusion rate of carbon in steel at 1750F is about .006" per hour. As the temperature goes up, the diffusion rate increases considerably. Any time the steel is at an incandescent heat, carbon loss can be a factor. At temperatures in the 1300F range, it is probably not a factor. If you heat treat with stainless foil, or if you have it done in a vacuum furnace, surface decarb is nil. Heat treating in a forge is another matter. If you are going to fine grind or polish the blade after heat treating, the decarburized layer might just go away. If you do not do any finish grinding or polishing, you might indeed have a thin ferrite layer on the surface. Ferrite is soft and weak and can start cracks that can ruin a blade.

I think I mentioned this before elsewhere but if anyone wants a more complete explanation of phase diagrams, continuous cooling curves, and blacksmith heat treating, please go to www.iforgeiron.com, click on Blueprints, and scroll down to "Metallurgy of Heat treating for Blacksmiths". It is not extremely technical but does try to explain some of what we have been discussing. Feel free to copy and distribute the information as I am the author and gave it to the website owner on the condition it could be freely used. It is based on some lecture notes I made way back when I was teaching Material Science.

Terry Primos
07-06-2004, 08:13 PM
OK. As long as I haven't P.O.'d anyone.

As far as the 4 million year old asteroid goes, the dating process is really quite simple. They know it is 4 million years old because they found it in a 4 million year old bed of rock. They know it was a 4 million year old bed of rock because there was a 4 million year old asteroid in it.

:lol

rhrocker
07-06-2004, 08:19 PM
I've read that link of yours Robert and it's good, I got a lot out of it. Just a woodworker however, and not a scientist, so it'll take me a while to digess a lot of what's being said, but I can follow it for the most part. Kevins sword making tutorial (I'd post the link here but probably should get permission from KC first) covers a lot of what you guys are saying in this thread also. This really should become a sticky eventually, it's darn near a tutorial in itself. On the meteorite dating, I was thinking that it was the patterns of the Widmanstatten crystals that gave it's date, but old rocks make sense also. I'll upload a photo of my slab here in a minute, totally off topic, but what the heck, it's steel. Incidently, I tried to rockwell test it, and it showed a big "O" on the scale. No carbon I guess. A picture will follow.

rhrocker
07-06-2004, 08:29 PM
Intermission: Here's my pride and joy for the day. This is just a quick sanding and etch to see what I had. Now I hate to cut it up!
http://www.fototime.com/59C8A70752A0642/standard.jpg

Quenchcrack
07-06-2004, 10:07 PM
Robert, that is a beautiful piece. I would strongly suggest you cut a small piece and forge it up a bit then cut, polish and etch it again. It would be a shame if you lost that beautiful crystal structure in the forge. Or are you going to grind it to shape? Didn't think about that......

Geez, I look at the stuff you guys are making and I feel like I have 6 thumbs. My big project yesterday was to cut off a piece of flat bar 3/8" x 1" x 3". I forged it into a three-legged trivet 6" in diameter. The legs were about 1/4" at the center and tapered to a point where I turned them to a nice scroll. The question was whether I could make it from one piece without any welding. It was interesting but the result was singularly unspectacular. :(

SteveS
07-06-2004, 10:24 PM
Robert don't touch it! WOWWOWOWOWOWOWO what a piece!

That's a treasure. Deserves a window box and a wall mount

Steve.

PS. Use that mouse pad platen for your handle work, it's wonderful. I can even get 3m microfinish belts to make a nice finish with that thing.

TexasJack
07-07-2004, 12:22 AM
Please excuse me for butting in with my 2 centavos, but I've been on the sidelines reading this for awhile - and in total fascination - and felt abliged to say something.

First - rhrocker, the guys are right - you need to polish up and display a piece of that meteorite! (Another possiblity would be to embed a piece in a handle or blade!!!!)

Second - Please don't ever think that we readers don't appreciate your knowledge! That willingness to share knowlege is the greatest thing about this forum. People who've been doing excellent work for years - and rhrocker is no slouch among them - still come across new ideas and better information. Those of us farther back on the curve are frequently in awe! What's also neat is the breadth of information, as it covers technical issues, marketing, artistry, materials and suppliers, and sometimes plain old horse sense.

Lastly - a bit of criticism - It sure would be nice if we could find a translator for these metallurgists. The discussion is fascinating; I only hope I'm understanding most of it!

Oh, almost forgot - the asteroid/rock layer you're talking about (with reference to the age of the meteorite), is that the iridium layer resulting from the asteroid that hit what is now the Gulf of Mexico?

Quenchcrack
07-07-2004, 01:25 PM
TexasJack, I think your "bit of criticism" is appropriate. We got a "bit" out of control there. However, I think you have to learn the language if you want to understand the science. Go back a page or two and check out the link to the page on www.iforgeiron.com. Yes, it is a bit technical but it has to be if you want to learn. There is a difference between some one telling you what fishing is like and teaching you how to fish. If you learn the basics of ferrous metallurgy and the concepts related to heat treating, you should be able to process your blades using the best and most appropriate methods. There are obviously several people here who can help when you have questions.

TexasJack
07-07-2004, 02:00 PM
I've got a couple of Wayne Goddard's books. He probably explains metallurgy for knifemakers about as well as anyone.

I don't think y'all got carried away at all. The point at which art and science interface is a most interesting place to visit.

SteveS
07-07-2004, 02:13 PM
I'm with TexasJack - I don't think you got carried away at all.

This is one of those threads that every time you read it, you understand a bit more.

Here's another great link. Explains the process with pictures of little fishies and everything.

http://swordforum.com/metallurgy/ites.html

Steve

Quenchcrack
07-07-2004, 08:38 PM
Actually, I have visited that site before, I just didn't know who created it. I have to admit, the fishies are certainly more creative and entertaining than conventional crystalography.

Don Halter
07-08-2004, 12:47 PM
If y'all live anywhere near a university, you can often find older editions of text books for a couple bucks. Students sell their books back at the end of semesters. If they changed books for the course, they only buy them back for $2. Find a student and offer them $4 for their material science text :D .


On the age of meteorites...you can do isotopic ratios similar to carbon dating, but with different elements/isotopes (K-Ar, U-Th-Pb, etc). The usual assumption is that asteroids/meteorites are the same age of the earth...4.55 +/- .02 billion years 8o . Ebay has had a lot a nice meteorite sections at decent prices in the last months or so.