is normalization a must?

G

GMBlades

Joined
Apr 27, 2014
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Hi all
I just received some 1084 steel from Canadian Knifemaker supply limited and started my second blade.
Rough grind is finished just need to bring down to 320 or so before hardening. I use a charcoal forge.
The question I have is, Do I need to ( have to) normalize this before I begin the hardening process, or just bring a shade past non magnetic and quench in canola.
I hope the quenchant is good enough for a blade this size. Its 5/32 x 1 3/8 x10 1/2. I've read that 1084 and canola will be ok for smaller blades but that is a relative term.:cool:

Cheers,
Grant
image_zps8bc4b3dc.jpg
 
General knife discussion is geared more towards discussing the knives when they are finished and discussion revolves around production and mid-tech knives. Shop talk might be a much more valuable resource for this topic. Let's see if we can get someone to move this over there for you. It would also be helpful if you filled out your profile information a bit more, get to know the knife makers you are asking help from and have them get to know you a bit.
 
Since you didn't forge your blade, you haven't had any grain growth in your steel, so you don't have to normalize, so you will be fine by a normal hardening procedure. In case of a thin blade, or to much heat applied when grinding, a stress relieving anneal might be wise prior to hardening.
 
First off, I think you'll be fine to heat treat your blade without normalizing. Chances are that it is in decent shape(grain structure) from the mill. That being said, I like to leave nothing to chance. You really have no idea of the true structure in the bar you have. Even the mill can't be sure of every piece they let out of the facility. Was it cold rolled or hot rolled? There may be stresses present that will make your blade warp during the quench.

I would at least heat it once to dull red(still magnetic) and let it cool to black prior to the final quench heat. That would be a simple stress relieving cycle.

If you were to start normalizing your steel... I would do 3 reducing cycles(1650F,1500F,1425F... or bright red/orange, cherry red, red ) before you work on it(while it is still a bar).
 
Rick, would you explain how normalization "happens?"
I imagine everything relaxing while the metal is at or above critical, but apparently the cooling is a vital part of normalization.

I know the procedure, but it would be good to understand what is actually happening to the steel during different stages.
Thanks!
 
Rick really knows his stuff. He has helped me re-vamp my heat treat procedure, as I was normalizing right before hardening. It is a good idea to get the normalizing done before the shaping is done, right after the blank has been cut out and cleaned up around the edges. And as he said.....you really have no idea what condition the steel is in when you receive it. More than likely, steel from reputable sources, like where you got your bar, it is "good enough" to go right to hardening.

So what is normalizing? It really does....normalize....the steel. Imagine the steel as a matrix of clay (iron) with glass particles (carbides) scattered throughout. You may have big carbides...small carbides.....alot in this one place.....not hardly any at all over here.....just a jumbled up mess with no order. We need to put that stuff in order....normalize it.....so the carbides are evenly dispersed with a small grain structure. To do that....we need to take the steel up to a temp where the carbides can move freely about the matrix...so we can distribute them evenly. For carbon steels we use, take 1084 for example, that would be around 1650F for knife sized cross sections. But while 1650F does a great job breaking those carbides free so they can move....it also blows up the grain size....which we do not want. That is why we do it again...only at a reduced heat....maybe 1500F on the 2nd go around. And on the third go around....even less temp....maybe 1400F...to further reduce the grain size. After the proper normalizing has been done....we have evenly distributed carbides....and the grains are all nice and even and small. Perfectly set up for a hardening procedure.

I hope that helps explain normalizing somewhat. Rick can certainly do a better job than myself, and I'm sure I've left out some important points. And I would like to give credit for the clay/glass matrix analogy to Kevin Cashen. When it comes to heat treat....he is really knowledgeable and helpful, and along with Rick and a few other great guys here, have helped me tremendously.

Almost forgot.....canola oil. Yes, canola oil does work well for 1084 as a quenchant. I HIGHLY recommend canola be warmed to 130 deg F, as this thins out the viscosity, making it a touch faster. 1084 really should take a fast oil for the best quench, like Parks 50, but 130F canola does come close, and in knife sized cross sections does indeed perform well for 1084 and 1080. Anything thicker than 3/16" and it may not fully harden through, however. One thing to keep in mind tho with canola....if you are going to be a knifemaker, and will be doing this again and again.....canola oil becomes expensive. It is not formulated to last a long time like commercial oils, so you really can't call canola a substitute for proper quench oils....but it can and will get the job done....within limitations.
 
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thanks Samauri.
Yes Rick and many others others are very knowledgeable and thanks to them sharing on the forum they have undoubtedly helped many new (and old alike) knife makers. I'll see how the next few blades go and if I am still keen on making more then I can get a gallon for $20.00 at McMaster Carr.
I'll be sure to post a few pics when its done.

Thanks to all who helped me out so far. You guys are great!
 
elementfe said:
Rick, would you explain how normalization "happens?"
I imagine everything relaxing while the metal is at or above critical, but apparently the cooling is a vital part of normalization.

I know the procedure, but it would be good to understand what is actually happening to the steel during different stages.
Thanks!
Click to expand...

I'm not Rick, thank heavens, but I'll try none the less. When one has forged a blade, the grains size can be different in different areas, depending on the amount of hammering done, and how different it was from one place to another. If this condition persists during hardening it can lead to nonuniform response to the hardening cycle, ie some areas will react differently than others. One thing that happens is large grains adjacent to small ones will absorb the small ones and get even bigger. Another is grain size has a significant influence on the quench speed needed for full hardening. Small grains require a faster quench to fully harden. So, to even this all out, it's usually recommended that one normalize the blades after forging, but before hardening.

Normalizing requires the steel be heated to a fully austenite phase, with all carbides dissolved. It's not that they can move around really, but they disappear and then reform on cooling. The steel is then air cooled. This allows a relatively even cooling compared to quenching in oil or water, so the risk of cracking is minimal. However, it's still fast enough that the carbides cannot clump together or grow to large size. In fact, with simple steels, even 1095, all the carbide may be in the carbide/ferrite layers of pearlite. It's also fast enough the the pearlite grains that form out of the austenite during cooling will be relatively fine, and more importantly, more uniform in size. Finer initial grain size encourages finer still grain size during the next cycle, which is further enhanced by the lowered temperature. This is the reason for the reducing temperatures on sequential normalizing steps. The final cycle that is done at 1450 F or so isn't technically normalizing, since all the carbides won't be dissolved, but it has the same intent, so there is no reason to split hairs there. If everything works the way it's supposed to, you get nicely distributed and very small carbides (0.2 microns or less diameter in some cases), and small, uniform grain size all at the same time. There are a couple more reasons to normalize, but I already have a wall of text, so I won't go into it unless asked, and they don't all apply to knives. Specific to the OP's steel, there won't be much if any carbide left after hardening, so the major reason is to refine and even out the grain size, assuming it wasn't before. He didn't say if he forged or not, or what condition the steel is in when he buys it (hot rolled, cold rolled, annealed, etc.)
 
Thank you, Me2 and Samurai!

I understand the procedure but wish I really comprehended what's happening on a structural level.
So, even though the carbides go into solution as austenite, the crystalline structure doesn't entirely disappear. My brain wants it to turn into pudding at austenite temps and have no grain at all, but it sounds like grain structure is maintained to some extent.
For myself, my homework is to try to understand just what the grain is.
That's part of the fascination of working with this stuff- it's that floating state where it's neither solid nor liquid where so much of the interesting stuff happens.
 
Specific to the OP's steel, there won't be much if any carbide left after hardening, so the major reason is to refine and even out the grain size, assuming it wasn't before. He didn't say if he forged or not, or what condition the steel is in when he buys it (hot rolled, cold rolled, annealed, etc.)
Click to expand...
Thanks Me2
I did not forge, only reduction. The supplier does not indicate what kind of steel it is. My next purchase of steel will be from Jantz and I'm not even sure if they indicate it...do they?
 
elementfe said:
That's part of the fascination of working with this stuff- it's that floating state where it's neither solid nor liquid where so much of the interesting stuff happens.
Click to expand...

Uh, I'm not sure what you mean here? It's still solid, just softer. No, the crystal structure is still very much there, it's just different than when it is below the transformation temperature. Ferrite (room temperature steel with very low carbon in it) has the atoms arranged in a cube with a prize atom inside, eight corners and one in the middle. These are all iron atoms. The carbon atoms fit in between, since they are MUCH smaller than iron.

Austenite is different, in that the atoms are arranged in a cube, with another atom in the center of each face, eight atoms, one at each of the corners, and 6 more in the center of each cube face.

These are the crystal structures, and even if the grains were 1" across, which they can be under certain conditions, each grain would be the same pattern repeated over and over. When the carbides dissolve, it is directly analogous to salt in water. Put too much salt in water at room temperature, heat it, and all the salt will dissolve. Cool it down and at some point, some of the salt will reform into salt crystals on the bottom of the glass. The main difference is salt water is a liquid/solid interaction, and carbide/iron is a solid/solid interaction. Salt can move where ever it wants in the liquid as it precipitates from the water during cooling. Carbide is very restricted in how far it can move during the air cool during normalization.

Wait, I have pictures!!!
 
monkeypuke said:
Thanks Me2
I did not forge, only reduction. The supplier does not indicate what kind of steel it is. My next purchase of steel will be from Jantz and I'm not even sure if they indicate it...do they?
Click to expand...

I have only bought cold rolled annealed (CRA) 1095 from Jantz. That was indicated when I bought it. If you dig around, they should tell you what they're selling. If not, and it has a nice smooth surface finish, it could be cold rolled annealed (CRA) or just cold rolled. If it has scale/black oxide flakes on the surface, it's probably hot rolled (HR). It might also be precision ground (PG) for the more expensive tool steels like O1, A2, etc.
 
The link below is to Kevin Cashen's web site. He has some good pictures of steel in the various stages of heat treatment, all polished and photographed by him. If your not suitably impressed, try getting a mirror/scratch free finish and then imagine doing it at 1000x magnification. Then wreck all that work by dipping it in acid.

http://www.cashenblades.com/metallurgy.html
 
Buddyleet said:
What is the average time for the 3 normalizing procedures?
Click to expand...
Maybe 20-30mins if your forge is at heat.

Heat to 1650F, cool to magnetic.
Heat to 1500F, cool to magnetic.
Heat to 1450F, quench in warm oil.
Heat to dull red(not past magnetic!) and cool to black three(3) times.

You will have a very soft, workable bar of steel with great grain structure just itchin' for that final quench at 1475-1500F. The last "3x's heat to dull red" does a decent(though, unorthodox) sub-critical anneal or "redneck spheroidizing". You can do a much more thorough job of it in a controlled kiln with long soaks and slow cool programing. With steels like L6, you pretty much have to.

Stuart gives me far more credit than I deserve. I'm stumbling my way through this right along side him. Threads like these help us collaborate our efforts and serve to give us more options. The best advice I can give you is to keep reading and to not get discouraged when you find out that everything you think you know is wrong. It WILL happen. Every mistake you make only helps you to troubleshoot later on.

Good judgement comes from experience, and experience comes from poor judgement. Not so long ago, I tried to quench fully sharpened, clay-backed, yellow-hot O1 tool steel in a bucket of icewater.:cool: I will never forget the sound it made... I'm sure Kevin C. was abruptly awoken by a disturbance in the "force" that night... oh, the suffering. :thumbup:
 
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