Spheroidize Annealed Steels

Alpha Knife Supply

Alpha Knife Supply

Always Innovating
Dealer / Materials Provider
Joined
Oct 14, 1998
Messages
2,155
I've received requests to clarify the annealed condition of the steels we stock.

We carry the following spheroidize annealed steels:
• 1080+ (80CRV2)
• 52100
• 8670
• A2
• D2 (Thinner Sizes)
• M2
• AEB-L

These steels are very soft and easy to work. All the alloys listed above do not require any special heat treatment to get hard i.e., no thermal cycling is required.

Here is a video of a chefs knife made from 8670. The knife is .100" thick at the spine. The heat treatment was non-standard because we were testing tempering times. The blade was heated to 1,600° for ten minutes and quenched in Parks 50. Then it was tempered twice at 180° for 10 minutes:

[video=youtube;Bn7u8dsS0kQ] https://www.youtube.com/watch?v=Bn7u8dsS0kQ[/video]

Chuck
 
The debate Chuck, is whether and annealed steel, say 1084, that is 95% spheroidized should be normalized (heat cycled) prior to HT in order to relieve any stress. From what your saying then, I gather, is that spheroidized steel will HT perfectly well without cycling. This makes sense to me because no matter the initial state of the steel its going to get heated to point of forming 100% austenite upon heat treating. I think that there's a perception that normalizing is a necessary step in guaranteeing a proper HT when dealing with spheroidized steels, especially in regard to 1084. I'm new to this argument and still feeling my way through it. Thanks for your input.
 
Fine soheroidizing requires no thermal cycling. Course soheroidizing needs normalizing to break up the carbides.
 
Tony, in the final austenitizing you want 100% martensite, but actually you don't want 100% of your carbon in solution, just the amount to get max hardness (around 0,7-0,8%, close to eutectoid).
If you start with a steel that is completely spheroidized (only spheroids + ferrite), normalization comes handy since you can dissolve ALL those big spheroids of carbon and finely redistribute ALL the carbon all over the matrix.
Your austenitizing temp. is not enough to "melt" more than the 0,7-0,8% of carbon from the spheroids, and after you got your 0.7-0.8% in solution, you still have the rest of the carbon in the shape of big carbide balls, a form we don't like in our final edge. Normalization will take care of it.

1084 had people scratching their heads wondering why they couldn't get max hardness at the usual target aust. temperature. It was because all the carbon was so segregate in carbide clusters, due to a coarse spheroidization, that a simple austenitization with the usual soak timing won't succeeed in snatching the necessary carbon for the solution. A simple trip to higher temperatures allowed to melt the big balls (LOL) and put the carbides in the desired form in very short time (a couple of descending heats, then... for grain refinement), way shorter than if you tryied to wait for them to evenly dissolve and diffuse at 1500 °F...problem solved.

If the steel is already finely spheroidized as supplied from Chuck, it means that the spheroids are so fine and well dispersed, that it doesn't take much time to put things back in solution in just one simple, final, austenitization, and the rest of carbon will stay in the form of finely dispersed carbides, exactly what we want!
 
Last edited:
I just got off the phone with Chuck at Alpha Knife. My main question was the state of their 52100. It is, indeed, fine spheroidized. Ready to machine, ready to harden as is. The 52100 from Alpha Knife Supply is sourced from a different mill than Aldo. Chuck said when he orders his 52100, he tells the mill, "I want it annealed for easy machining, but ready to harden as well." I'll probably normalize and cycle it anyway. OCD like that!
 
Makes sense Stezann. Then it would seem that we need to question our suppliers as to whether steel is provided as finely spheroidized or coarsely. For instance, a very popular provider in these parts that I've used myself only lists his 1084 as 95% spheroidized. This would lead me to believe that the carbon is dispersed in fine grains throughout 95% of the steel, but I'm not sure. I guess my question to the group would be what exactly does that mean to be "95%" spheroidized?
 
95% means 5 % is a bit of pearlite !
Definitely smaller spheroids are what we want -- It goes to austenite faster , requiring shorter soak time. Thus if you want small spheroids Quench ant Temper is a better way IMO.
I don'tquite understand " carbide clusters " If you have a proper uniform structure there shouldn't be any clusters whether you have large of small carbides.

While normally you get stress free it is possible to get sheroidized with stresses !
 
My opinion is that all we usually know is what percentage of spheroidite the steel is. Chuck asks his supplier to send it soft and ready to harden. That hopefully is fine spheroidite. But does he or anyone else actual know the exact structure. Does the mill know it exactly? Different mills may have different ideas of what the structure should be, too. Aldo's supplier may prefer a different baking time or cooling rate and get coarse spheroidite. Also, it depends of the pearlitic structure they start with. Steel often goes from one supplier to another several times before it gets to us. I seriously doubt they make the bulk of the steel in structures that are of the most benefit to knifemakers.

To be sure that the steel is ready for hardening, at a minimum, a single solution soak should be done at 1550-1600F.

The other way to look at it is:
"If the steel is fine spheroidite will thermal cycling hurt it?"
vs
"If the steel is coarse pearlite will it harden without thermal cycling?"
 
I'm convinced. Cycling will be a permanent part of my process. This whole debate has been painfully enlightening. :p
 
When I send a blade to be heat treated will they normally cycle it anyways or only if I ask for it or not even then?
Thank you.
 
Clusters: i chose the wrong word, i intended big balls, big carbide spheroids.

That's how i see things, a coarse spheroidization it is not a bad thing, depending. The mill will easily provide what we want (what the majority of the customers want), and we need to know what we compromise.

The more you go deep to spheroidization, the easier the machining and thus saving on toolings (it will cut like hot butter)...and you spend a bit more energy in the heating department to place carbon back where you want.

The finer the spheroidization, the quickest, straightforward HT procedure to harden the blade, at the expense of a bit of life from your tooling...drills, mill bits, files....obviously almost negligible because we are still talking annealed steel, but significant enough in mass production environments. There is also the benefit that the mill probably has better equipment/controls to properly spheroidize than we got....most of us just approximate the procedure and we do not necessarily better than steel industry
 
Stacy E. Apelt - Bladesmith said:
Chuck asks his supplier to send it soft and ready to harden. That hopefully is fine spheroidite. But does he or anyone else actual know the exact structure. Does the mill know it exactly?
Click to expand...
I ask a different question, "Does the steel get hard using normal heat treatment?" If the answer is no, we do not sell the steel.

We've rejected steel shipments because the steel did not meet our expectations. We refuse to sell other steels because of known problems. An example is Bohler Uddeholm M390 and Elmax. Both steels come from the mill with a HIP can layer on both sides of the sheet. The HIP can must be removed to get to the blade steel. We were paying to have the can ground off while we asked BU to send the steel with the can removed. When BU refused to remove the can, we refused to sell the steel. More examples are running steel and titanium through annealing cycles to make the materials more workable. If we receive any material that does not meet our specifications, we refuse to sell it.

Stacy E. Apelt - Bladesmith said:
The other way to look at it is:
"If the steel is fine spheroidite will thermal cycling hurt it?"
vs
"If the steel is coarse pearlite will it harden without thermal cycling?"
Click to expand...
As I wrote earlier, we have a different philosophy. If the steel won't get hard using normal heat treatment, we don't sell it. We will not make a knifemaker go through unnecessary steps or spend extra time because we did not fulfill our responsibility as a supplier.

We won't pass problems on to knifemakers.

Chuck
 
Thanks Stefano ...You can't sneak these things past a metallurgist !! LOL
 
Chuck, you go the extra step for knifemakers and should be applauded for it. You are a top notch supplier, sir.

I do not doubt that a regular HT regime will produce a hard blade. That said, thermal cycling spheroidized steel is a good thing that when done right, can enhance it's performance. To say "unnecessary steps" might be a true statement but it also leaves a lot on the table. You can ride a factory stock motorcycle right off the showroom floor... probably even run an amateur race with one... as long as everybody else has a stock bike and their skills are on par.
 
Rick Marchand said:
Chuck, you go the extra step for knifemakers and should be applauded for it. You are a top notch supplier, sir.

I do not doubt that a regular HT regime will produce a hard blade. That said, thermal cycling spheroidized steel is a good thing that when done right, can enhance it's performance. To say "unnecessary steps" might be a true statement but it also leaves a lot on the table.
Click to expand...


I agree with this statement, in principle, but disagree with certain parts of it. There are examples of spherodized steels out there that are in common circulation that WILL NOT respond to basic heat treat without considerable thermal cycling, and this has bitten even some of the best knifemakers. Variances from one batch to the next complicate matters further. A customer should expect a certain performance from a product, or at least have it laid out in plain terms that there are requirements for performance. Industry, which like it or not is what we're part of, would never accept some of the hoops we perceive as 'necessary'. How many bars of Starret O1 do you think would be sold if they required the tool rooms that are their primary customers to soak in a salt bath at normalizing temp for an hour before commencing descending thermal cycling for grain refinement? The vendors know this, and take steps to make certain their product is in a condition where it works efficiently for their customer base.

This is NOT to say that it is necessarily in a condition that you or I would perceive as 'pushing the performance limits' of the steel, however it does mean that the steel is, in fact, useable in the condition that it's in.

I have to applaud Chuck for demanding more for his customers. His attention to details like this is truly commendable.
 
This blade is 52100 steel , hardened on 800 C , quench in oil . Temper: 2 X 1 hour on 180 C , cold water quench between two temper . Steel before HT is as I bought it ...... And I like what I see inside ?

This picture is after hardening and little cleaned before temper ..........

mucz1g.jpg


This one is after temper cycle

ermufm.jpg


And here what is inside , but my ability to make a good macro photo is on the level of neanderthal :grumpy:

ilx152.jpg


PS . I always leave the upper part of the tang , so chances to twisted blank when HT is reduced , and if it is blank with full tang for scale i leave piece of steel on tip of blank , or on the handle side ....That way when I cut that piece I can see after HT what I got :)
 
Last edited:
Natlek, it's difficult for me to understand what you're saying. Are you saying that you are satisfied with the performance and grain structure of the steel you're using? Is there any way you can improve on the photo showing grain structure? My first thought is that it doesn't look very fine, however it's hard to say from that photo.
 
You must log in or register to reply here.
Back
Top