Powered metallurgy to AEB-L?

[DeadboxHero]

AEB-L has consistently been called the finest grained stainless alloy, would the PM process make the grain even smaller?

 

[mycough]

Good question, love it for kitchen knives.
Russ

 

[Brian.Evans]

**Edited to add** I will not edit this post, I hate when people do that. I was incorrect, I learned something more about steel today, (several somethings actually) so it's a good day! Please do not believe this post. I have to figure out where I got this poor information from, or what bits of information I have jumbled in my head to come up with what I now understand to be utter nonsense. I do love AEB-L at high hardness though. I do know that to be completely true.

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides. Carbides are wider than the edge of a super fine edge, so they don't have enough steel to hold them in the edge and they tear out. Powdered steels like m390 or S35VN are high carbide so they don't take as fine an edge. There's a reason 13C26/AEB-L is used in razor blades and why custom straight razor makers use low alloy steels. Yes, they might not hold up under high abrasive cutting, but in taking a super fine, super keen edge, they outshine all others.

 

[Gator97]

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides...

I'm a bit confused, Chromium does form carbides in general, 3 types in fact, Cr3C2, Cr7C3, and Cr23C6. Are you saying they do not form during AEB-L heat treatment process? Or they do not form in sufficient amount to affect AEB-L carbide volume in any meaningful way?

 

[DeadboxHero]

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides. Carbides are wider than the edge of a super fine edge, so they don't have enough steel to hold them in the edge and they tear out. Powdered steels like m390 or S35VN are high carbide so they don't take as fine an edge. There's a reason 13C26/AEB-L is used in razor blades and why custom straight razor makers use low alloy steels. Yes, they might not hold up under high abrasive cutting, but in taking a super fine, super keen edge, they outshine all others.

So the PM process only distributes the carbides?

 

[mete]

No, the PM process makes everything more uniform including carbides , and makes carbides smaller ! However grain size is mostly independent .

 

[DeadboxHero]

Oh, I see.
thanks mete

 

[Ankerson]

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides. Carbides are wider than the edge of a super fine edge, so they don't have enough steel to hold them in the edge and they tear out. Powdered steels like m390 or S35VN are high carbide so they don't take as fine an edge. There's a reason 13C26/AEB-L is used in razor blades and why custom straight razor makers use low alloy steels. Yes, they might not hold up under high abrasive cutting, but in taking a super fine, super keen edge, they outshine all others.

Has much more to do with sharpening talent etc than the actual steel.

Sharpness is really nothing more than the actual measurement of the apex in nano meters.

After a certain point that is well beyond anything that can be done by human hands..

I personally can get steels like S35VN etc. to the same level of sharpness as steels like AEB-L without much trouble, that's actual measured sharpness using a sharpness tester.

 

[DeadboxHero]

Thanks Ankerson,

That leads to another burning question. Is carbide tear out real? If so what's the best abrasives to form and polish an apex?
Is it a game of matching the mohls of the abrasives and carbides?

 

[Ankerson]

Thanks Ankerson,

That leads to another burning question. Is carbide tear out real? If so what's the best abrasives to form and polish an apex?
Is it a game of matching the mohls of the abrasives and carbides?

It's overblown really to fuel certain people's agendas, if you drag the edge on your thumbnail and if it's smooth it's good, if not then touch it up, it is that simple.

I don't polish edges anymore, not really worth the effort IMO.

Don't use anything finer than green compound, and that's once in awhile and only for quick touch ups, like 2 or 3 passes each side.

Normally I am in the 40 Micron range.

I personally don't over complicate things, once I got that sharpness tester it confirmed what I already knew for the most part.

 

[DeadboxHero]

I admit. The effort to performance ratio is marginal and can lead to making a foil edge or rounding the apex at higher grits.



Ankerson, your the guy to ask

Is there any difference in grain size with all the high end PM steels.

For instance m390 to s90v?

Does m390 polish better because of grain size or 20% chromium?
Also how important is the proprietary melting processes from "micro clean" to "double vacuum melting" etc.
Marketing hype? Or just too marginal of a performance increase to make a real world difference?

 

[Ankerson]

I admit. The effort to performance ratio is marginal and can lead to making a foil edge or rounding the apex at higher grits.



Ankerson, your the guy to ask

Is there any difference in grain size with all the high end PM steels.

For instance m390 to s90v?

Does m390 polish better because of grain size or 20% chromium?
Also how important is the proprietary melting processes from "micro clean" to "double vacuum melting" etc.
Marketing hype? Or just too marginal of a performance increase to make a real world difference?

Depends much more on actual HT process so that will vary greatly.

 

[DeadboxHero]

Cool. Thanks

 

[Gator97]

That leads to another burning question. Is carbide tear out real?

I'm inclined to share Ankerson's point of view on that one. Purely by numbers/probability it is hard to imagine a lonely carbide hanging at the knife edge with one finger waiting to be torn out by malicious hard particle(s). It can happen yes, given their(carbide) number and depending on the medium being cut, but to happen on a large scale you have to be saw cutting sandpaper or a cinder block, which would do far worse damage to low carbide volume steels, which would be the opposite of what carbide tear out proponents predict.

 

[DeadboxHero]

Awe, I see. I was curious about tear out from sharpening though not cutting.

 

[Sunyata]

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides. Carbides are wider than the edge of a super fine edge, so they don't have enough steel to hold them in the edge and they tear out. Powdered steels like m390 or S35VN are high carbide so they don't take as fine an edge. There's a reason 13C26/AEB-L is used in razor blades and why custom straight razor makers use low alloy steels. Yes, they might not hold up under high abrasive cutting, but in taking a super fine, super keen edge, they outshine all others.

I think it would depend on sharpening tools and skills.

Why not cut the carbides?

 

[james terrio]

I'm a bit confused, Chromium does form carbides in general, 3 types in fact, Cr3C2, Cr7C3, and Cr23C6. Are you saying they do not form during AEB-L heat treatment process? Or they do not form in sufficient amount to affect AEB-L carbide volume in any meaningful way?

The stainless steel in your kitchen sink or tableware may have 20% or more chrome, but I assure you it has very few if any carbides. Because it has very little carbon. The chromium is mainly there to form a self-perpetuating oxide layer for corrosion resistance, to protect the iron.

Similarly, there's less than .7% carbon by weight in AEB-L/13C26 to begin with, and it's nearly all tied up with iron, forming good hard martensite structure. There's simply not enough "extra" carbon in AEB-L/13C26 to ever form many carbides with the chromium. That what makes it so stain-resistant; almost all the chrome is "free". It's a brilliant and very cost-effective way to make steel that's tough and fine-grained yet highly corrosion-resistant.

Understanding this explains why you see other "stainless" and tool-steel alloys with so much carbon... nearly always over 1%, many around 1.5%, some approaching 2%! The additional carbon doesn't make the steel any harder, it's there to form wear-resistant carbides with the large amounts of chrome, molybdenum, vanadium, etc.

 

[mete]

In a grinding wheel you want the abrasive particles to wear a bit , then fracture , with the fracture leaving a sharp edge..
At one point you will tear out the remainder of the particle leaving a hole or depression. Lots of variables here but D-2 has large carbides which like to pull out leaving a less sharp edge but one that will cut fairly well but not a very sharp edge . Sharpness meaning the radius of the edge . Clear ??

 

[chiral.grolim]

AEB-L is able to be sharpened to such a fine edge because the chromium doesn't make carbides.

That's incorrect, where did you read that???

As Gator97 typed, the chromium most definitely forms carbides, and they are not always small aggregates. Sandvik has measured the carbide volume of AEB-L/13C26 before HT to be ~12% and after HT it remains ~5% (probably less), which is not all that different from CPM-3V and A2 steel (depending on HT protocol).
http://smt.sandvik.com/en/materials.../strip-steel/sandvik-13c26-razor-blade-steel/

Carbides are wider than the edge of a super fine edge, so they don't have enough steel to hold them in the edge and they tear out.

Please give a reference for the measured size (in nanometers) of a "super fine edge" and the size of "carbides" to explain your assertion regarding tear-out.
I will start you off by indicating that the absolute finest edges are achieved on >90% carbide hard-metals. In comparison, CPM-10V is <20% carbide by volume.
Carbides can certainly be wider than an apex, and they can also be sculpted to form the very finest of apices... with the right tools and technique. Carbides are very hard and tend not to absorb impact-force, using poor (dull) tools or technique could knock them loose = tear-out. For removing lots of metal (low grit), that doesn't much matter, and at very fine (high) grit it is less likely to happen, depending on the size of the carbides in the steel vs the abrasive.

Powdered steels like m390 or S35VN are high carbide so they don't take as fine an edge.

Again, flatly incorrect. As Ankerson states (from experience supported by objective measurement), high-carbide steels can absolutely take as fine an edge as low-carbide steels, but achieving a fine edge on either is a matter of equipment and technique.

There's a reason 13C26/AEB-L is used in razor blades and why custom straight razor makers use low alloy steels ... in taking a super fine, super keen edge, they outshine all others.

No, it is used because of consistently good manufacture and especially low cost.
Powder steels (which include "low" as well as "high" carbide steels) are much more expensive to produce and HT. If an ingot steel gives you the qualities (performance) you require for less cost than a powder steel, why would you choose the latter?


In direct response to the OP, the PM process could better refine and distribute the primary carbides in 13C26 but not by much, it wouldn't change total carbide volume and that is already quite small and well distributed... PM process unlikely to improve it noticeably but would definitely increase the cost!

 

[DeadboxHero]

Great posts guys thank you!