Latest development in the high performance 52100 blade

[Wulf]

Ed Caffrey seems to have achieved a similar pattern in a 52100 blade I just noticed on a dealer's website.

I wonder if he used the same, or similar thermal sequence, as Mr. Fowler.

 

[Kevin R. Cashen]

I think before we start delving into ancient, mystical, metal-working secrets, we need to ground ourselves again in some good clean 21st century metallurgy. I hope Ed doesn’t mind if I give some scientific reasons why what he has here is pretty cool and worthy of exploring. By now it is probably no secret that I am not always the greatest fan of Ed’s methods or conclusions, but sometimes I am, and intellectual honesty necessitates that I acknowledge the good along with the bad (e.g. I like Ed’s endorsement of proper quenching oils, and loved his article on the use of brass- it needed to be said).

There is no secret, or magic, to alloy banding, anybody who has ever performed enough thermal treatments to allow the carbon to separate on that level has seen it, the internet forums are littered with folks asking what the funny patterns are in their O1, 52100, 5160, 1095 etc…

But what Ed has here is kind of interesting. This is the first time I have seen somebody confine it to a predetermined area of the blade for a performance feature. I find his concept of using it as a buffer zone above the martensite for blocking fracture travel very intriguing. This is because of the fact that not only does banding look different, steel that has had vast amounts of its carbon locked up in the alloying sheaths in this manner have a high degree of plasticity. For more information on this, see the early work of O. Sherby* in the research of super-plasticity in heavily thermal treated (spheroidized and banded) steel. So what Ed is offering here is a super tough version of the edge quench in a mono-steel, perhaps without the annoying problem of blades easily bending, by being fully pearlitic all the way to the spine (I am not sure what the blade consists of above the banded zone). Either way it could potentially be a real tough puppy to try to break .

It is the fact that there could be something here, that I am being so picky about the terms used. It is not the word “band” or “zone” that concerns me at all; it is the liberal use of the word “wootz”. This could be a unique accomplishment and I would hate to see it cheapened by inadvertently using misleading or false terms in our excitement. It is pretty cool all on its own, and should need to borrow no hype from the wootz mystique. It is indeed wootz-like, and wootz-looking, but it is not the high carbon crucible cast steel of the ancient Hyderabad region, it is good old 52100. Sorry Ed, the swords of ancient Persia were not made from thermal cycled bearing steel, somehow I doubt that is what you were implying (I hope).

If simply banding up carbide equals real wootz then any of us working with O1, 5160, 52100, 1095, almost any tool steel, etc… have been making genuine wootz blades, and folks like Al Pendray and John Verhoeven simply wasted several years of their lives working on nothing. There are those who worked with Wadsworth or Sherby who still want to classify any banding as wootz, despite the subsequent and extensive findings of Verhoeven and Pendray, but just because a Volkswagen is small, and has wheels, that doesn’t make it an ancient Egyptian chariot.

Our business already sees enough false information from wrapping common materials in the wootz mystique. So, far from trying to be antagonistic, I am sincerely begging you, for the good of our business, not to take that route, considering the great rewards and knowledge sharing that can be had in straightforward facts and terminology.

Keep up the good work, as I am excited to see what that little super-plastic zone can do for the indestructibility of your blades.


*D. R. Lesuer, C. K. Syn, and O. D. Sherby. Fracture Behavior of Spheroidized Hypereutectoid Steels. Acta Metall. Mater., 43(10):3827--3835, 1995.
C. K. Syn, D. R. Lesuer, and O. D. Sherby. Influence of Microstructure on Tensile Properties of Spheroidized Ultrahigh-Carbon (1.8PctC) Steel. Metall. Mater. Trans. A, 25A:1481--1493, July 1994.

Just to list a couple

 

[Wulf]

A round of applause, ladies and gentlemen...

To Ed for his continued pursuit of performance in forged blades and to Kevin for his metallurgic expertise, sound objective reasoning, and respectful manner

 

[blademan 13]

Hear, hear. Simply one of the best written and itelligent posts I have had the pleasure of reading on this forum.

 

[RogerP]

A round of applause, ladies and gentlemen...

To Ed for his continued pursuit of performance in forged blades and to Kevin for his metallurgic expertise, sound objective reasoning, and respectful manner

Insert sound of two hands clapping here.

Roger

 

[Daniel Koster]

Jason - I get that exact same banding on my 1095 - what is it?


Kevin?

 

[mete]

Alloy banding is alloy banding .It is segregation of alloying elements due to the solidification of the ingot when the steel is made.Segregation occurs because of differences in solubility between liquid and solid.Other than for strange blade makers it's not desirable !!

 

[Kevin R. Cashen]

Well at least most of industry finds it undesirable. The alloy films themselves are always there, as mete said they are a natural by-product of the casting process, (heavier alloying elements separate from the pour first and form little crystalline trees that the rest of the ingot solidifies around) and mills try like heck to break them up and evenly distribute them, but those substitutional alloy atoms just don’t move as freely as interstitial carbon atoms. When you heavily cycle the steel within that range between Acm and Ac1, or slightly below, you give the carbon the opportunity to gather together on concentrations. Spheroidizing is a good example of this when there is nothing but iron carbide. But if there are carbide forming elements they will readily latch onto this wandering carbon and form chemical bonds in the form of carbides (Chromium carbide, vanadium carbide, tungsten carbide etc…) When you get heavy concentrations of carbides in those alloy streaks or bands, left over from the casting process, they become much more visible. They will obviously abrade at a differing rate and will like to etch a completely different way from ferrite. If you want the pattern to vanish, you simply heat to Acm, hold long enough to break the carbide bonds and put the carbon back into solution.

The super-plasticity is rather simple; deplete the ferrite of carbon and the steel gets soft (it is the basis of all our annealing processes), the more carbon you get out of the ferrite the softer it gets, and ductility goes up. Purposefully banding will have the same effects as spheroidizing. Ed has done a good thing in keeping it away from the cutting edge, since iron needs carbon in solution in order to form martensite and harden. An edge made up of heavily banded material would be abrasion resistant due to the carbides, and could even skate file or score other objects, but the edge would deform more when impacting harder objects. As Ric Furrer is fond of saying “think of is as diamonds suspended in pudding”.

 

[mete]

Kevin, I question the word superplasticity.Typically metals have well under 100% elongation. There are alloys and processes that will produce 1000% elongation, that is called superplasticity. I've seen that in Ti alloys where the metal was pulled right at the phase change temprature ,just like pulling taffy or bubble gum!! Pick another word.

 

[Kevin R. Cashen]

Sorry mete, it is not my word. I am merely referring to the numerous mentions of it in Sherby's work. I am not saying that I necesarrily agree with it, I certainly dissagree with him and his associates if they may imply that any banded alloy is genuine damascus, so I have no reason to blindly follow. But it is the terminaology that is continually used in the research of this phenomenon, making it almost unavoidable.

If you will forgive me, I will let the taffy/bubblegum metaphor slide

 

[Dan Gray]

If you will forgive me, I will let the taffy/bubblegum metaphor slide

sounds sweet to me...

 

[mete]

Kevin, I know it wasn't your word. When you see 1000% elongation in metal a typical comment is 'wow, that's just like bubble gum ! '

 

[Dan Gray]

Kevin, I know it wasn't your word. When you see 1000% elongation in metal a typical comment is 'wow, that's just like bubble gum ! '

I haven't figured out how you can get 1000% out of 1 (1= 100%) whole yet..
I can see 10 times or 100 times in length..
like what's 120% of one apple ,,, 100% plus 20% air? ..

 

[Laredo7mm]

The percent elongation is a ratio of the final length minus the original lentgh divided by the original length times 100.

Or:

%E=((Lf-Lo)/Lo)x 100%

For example. Your orignal sample is 1 inch in length and you strech it until it breaks, and length of your sample after it broke is 2 inches. Then ((2-1)/(1))X100% = 100% elongation.

So for 50% elongation, the material can stretch 50% of its original length before it breaks.

I hope that helps, and I hope I got that right.

 

[Tom Buchanan]

like Chris Farley said in the movie Almost Heroes......'"my God, do you want my head to explode?"

 

[Jose Reyes]

Kevin,

Does that crytalline branching form throughout the ingot or just on top, like Ice on a pond? Is it undesireable because the ingot will be used in smaller chunks and you want a more homogeneous material? Would there be any benefit if you were casting something in it's finished form? Would it act as sort of a shock absorber or anything or would it just cause the ingot to fall apart along those seams?

 

[Dan Gray]

The percent elongation is a ratio of the final length minus the original lentgh divided by the original length times 100.

Or:

%E=((Lf-Lo)/Lo)x 100%

For example. Your orignal sample is 1 inch in length and you strech it until it breaks, and length of your sample after it broke is 2 inches. Then ((2-1)/(1))X100% = 100% elongation.

So for 50% elongation, the material can stretch 50% of its original length before it breaks.

I hope that helps, and I hope I got that right.

yeah what Sean said
I think

 

[Dan Gray]

yeah what Sean said
I think

I'm trying to be comic relief here.. some of the guys on another thread are not quite sure what to think of me
I hope I don't bug you all toooo much, I'll have to get a life if I can't do this anymore..I even understand banding ,,,, some

 

[mete]

Super plasticity starts like this __ and ends up like this ____________________ before it breaks !! .....Jose, the ingot mold is a long tube closed at the bottom so the cooling occurs from the outside to center all along the length.The alloying elements are very soluble in the liquid steel but a lot less soluble in the solid state. Therefore the center of the ingot [the whole length] is richer in alloying elements as the elements are driven toward the center. Banding while present in the simple steels can cause serious problems in complex alloys like tool steels especially if the ingot has not been worked down to thinner sections. The fix is to make steel like the Crucible CPM steels .

 

[Kevin R. Cashen]

mete, thanks for reminding me that the purer metal tends to solidify first followed by segregation of more concentrated alloying elements, I always seem to get those mixed up.