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DGentile

Understanding alloy banding...

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Ok in my last post I showed a blade part which clearly shows alloy banding... I've spent the last hours over my metallurgy & heat-treatment books and with web-searches to get more information about this "effect"...

 

It's not too much I have on this topic... so I hope that some of you might fill in where I either completly missed something or wrote something completly wrong...

any additional information is appreciated as well

 

I have attached the picture of the mentioned blade again... for those who "are new to this thread"...

 

thanks for the "information" :)

 

Alloy Banding

Alloy Banding only happens in hypereutectoid steels (C>0.8%).

As far as I have found information about alloy bending it says that it can be supported by carbide forming alloying elements (usually Cr, V, W, Mo).

That menas that steels similiar to 01 or even sometimes simple 108X steels could "suffer" from alloy banding...

 

And here's what I have about the "origin":

whilst the initial ingot is being cast at the mill, it sometimes happens that the emelents will seggregate into higher and lower concentratet zones.

when the product then is broke down there's a large reduction in it's cross-section...

the layers of higher / lower concentration get "streched out" and distributed with a varrying composition... That is what in the end produces the visible effect... and it explains why it follows the "forging pattern" and the more "heavy reductions" made (for example from strong drawing dies).

 

However this makes me a bit "nervous" about the product quality... I mean it's the result of an inconsistence... so any idea how that affects the blade (in a negative or even a positive way? )

 

and I've found a post from Ed Fowler where he recommends longer soaking times before the quench to get "rid" of the effect (if one wants to do so).

 

along with the information above I found an interesting document about the development of microstructural banding in low alloy manganese steels...

the document refers to artificially seggregated steel (produced by interrupted cooling) which afterwards shows microstructural alloy banding...

which brings me to another question... could an interrupted quench have an impact on this... (also I am partially aware that it would "cross" the theories mentioned above)...

 

At least I now know how it happens, yet I wonder what a smith can do to "create" or "push" this... and if the longer soak times (mentioned by Ed Fowler) relly do "equalize" the steel again...

 

If I have some time this week I'll have some experiments... and show the results (if anything worth to be mentioned turns out).

 

 

as mentioned... any information / correction is WELCOME!

 

thanks

 

 

dan

 

Picture: metal_effect.jpg

 

PS: If any here has access to a lab... where he can test the material I have and make a complete analysis (chemical)... I'd like to send him/her a bit of that steel... I'm curious about it...

Edited by DGentile

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I'll correct you if you don't mind . I have in one of my books an excellent photo of banding in a .25 % C steel !! So your hypereutectiod limit is incorrect.....Due to differences in solubility of alloying elements between liquid and solid there is a tendency to have the last part of the steel to solidify be richer in alloying elements. This and the initial cooling rates and rolling temperatures determine amount of banding.......Longer soaking times will do more damage because of grain growth than any benefit in reducing banding. Forging would tend to reduce banding......Eliminating banding entirely would require the steel be made with powder metal process such as Crucible Particle Metallurgy [CPM alloys]....As far as your blades , I think you are worrying needlessly.... Just tell your customer it's a secret process !! ;)

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Dan, you can manipulate the grain banding just like a pattern in laminated steels if you want to. Then you have the option to really confuse the customer. That's been tried by some with disastrous results.

 

It's no secret. It's not special. This is something every knife smith should know about, know how to make happen and know how to make go away. It happens in some steels more readily than others though. It's merely more for you to learn about. Have fun with it.

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Dan, you can manipulate the grain banding just like a pattern in laminated steels if you want to.  Then you have the option to really confuse the customer.  That's been tried by some with disastrous results. 

 

It's no secret.  It's not special.  This is something every knife smith should know about, know how to make happen and know how to make go away.  It happens in some steels more readily than others though.  It's merely more for you to learn about.  Have fun with it.

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Mike towards customers or fellow smiths I never had "secrets"... I don't like "trade secrets" anyway.... they don't do anyone a bit good...

if I ever get asked what "that" pattern is I just want to be able to give a simple yet correct explanation to a customer...

 

I have seen that it is possible to manipulate the pattern/flow with forgin...

the piece from which I have taken the picture actually has kind of a "ladder pattern" looks quiet cool... and I am sure it comes from the use of the strong drawing dies on my powerhammer...

(the steel originally was a rail-piece (top piece) so there was a lot of deformation going on...

 

 

and you mentione "know how to make it happen".... does that mean there is a posibility to get alloy banding after the smelting process??

 

dan

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I've not yet had sufficient quantity of the smelted material to test that hypothesis. It is ultra high carbon material (hypereutectoid), but very low in alloying additives so we might not get much segregation. Cut sections of the blooms show liquidus changes consistent with wootz-like carbide formations so there may be some segregation that can be tickled into showing themselves superficially.

 

I have not yet had the chance to send samples off for spectrography so I am still uncertain as to the mixture of materials and what it has picked up from contamination or charcoal. I can certainly attempt some of that manipulation this weekend at Harley's, if we can get a billet welded up from some of the material we are bringing along. Getting the banded pattern should be a piece of cake if it's at all possible. If that happens I'll get photos done and post them.

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Mike

If you don't mind me asking have you forged out any of this yet? I did a search but did not come up with anything yet.

 

Dan

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I will add support to what Mete said. The photo below is of a .27 carbon, 1.25 manganese steel. No other alloys. The material is in the hot rolled condition. The brown areas are pearlite and are higher in carbon and manganese than the light areas. The light areas are ferrite. When quenched and tempered, the banding will become much less pronounced but it will still be there. You really cannot get rid of the banding by heat treating.

829500_1.jpg

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I have produced patterns similar to the one Daniel produced on 5160 bar stock. So, I will reiterate the point that the steel does not have to be hypereutectoid. I am more interested in accentuating the pattern and creating it at will as it may give some additional “character” to mono steel blades.

 

I originally produced the pattern more by accident than anything else. I thermally cycled the steel about a dozen times with a decreasing heat each time and allowed it to cool to near room temp. in still air between each cycle. The first heat was above 1550f, the second perhaps 1500f, and so on, and the final heats were barely hot enough to get the steel to show color…a dull red around 1000f or so. The pattern was there but not very potent. I’d like to make it stronger and any suggestions you guys can give me to manipulate/produce this would be highly appreciated.

 

From the reading I have done recently in an attempt to get more alloy banding (Google alloy segregation and slow cooling, Daniel!) it seems as if alloy banding and microstructure segregation is a product of repeated heating into the austenitic region, followed by an extended soak to get everything into solution, and then *slow* cooling. So, theoretically, if I repeatedly heat my steel to critical and hold it, and then follow with a slow cooling rate, the various elements in the alloy will be more likely to segregate themselves. Fast cooling apparently does not accentuate the effect (quenching/fast cooling rates minimize it) and the presence of manganese seems to be decidedly advantageous….that is, if one desires to produce segregation instead of minimize it. The presence of manganese (and other alloying elements like Cr and Mo) apparently can accentuate the propensity of an alloy or microstructure to segregate. Apparently carbon will tend to migrate to areas of higher manganese/Cr/Mo concentration and cause depletion in areas of less concentration of these alloying elements. In about another month I'll be exploiting this stuff to the Nth as I'm determined to be able to produce this effect on demand. We'll see how it goes and I'll post pix and attempt to keep detailed records of how it happens.

 

Or not. :unsure:

 

I'm developing a line of tactical style knives and being able to produce this effect (in conjunction with a hamon/hardening line) in 5160 is my goal. Of course I'll share any details that don't become apparent.

 

Brian

 

 

Notes and further reading!

 

http://doc.tms.org/ezMerchant/prodtms.nsf/...pdf?OpenElement

 

http://doc.tms.org/ezMerchant/prodtms.nsf/...pdf?OpenElement

 

http://www.bladesmithsforum.com/index.php?sh...l=alloy+banding

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Nature abhors organization! Any ordered system, if left to its own, will become disordered (do you have kids?). Alloy segregation is a degree of order. Things are separated and nature doesn't like that. Nature wants to achieve maximum ENTROPY! Entropy is disorder. The more you heat the metal, the easier it is for the carbon and other elements to diffuse toward maximum entropy, or maximum distribution throughout the piece. Now having delivered that rant, you really cannot seriously affect alloy banding at normal heat treating temperatures and times. I once left a piece of steel sitting at 1950F for 24 hours just to see what would happen. Aside from a LOT of scale, not much happened to the microstructure. Soooooooooooooooooo.........if you accept all that, someone explain why metallic crystals are so well ordered? After all, crystals are NORMAL!

 

That was a bone for TAI! :lol:

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i think it would be easier to apply the elements to the surface of the blade while the blade is hot, its actually part of an idea i got a while back to apply copper and/or gold or other precious/soft metals to steel.

this way i can create designs or patterns for jewelry, fittings, or a blade.

 

but this will give you the greatest ability to reproduce an alloy banding type effect if it works.

ofcourse you are not actually causing alloy banding but it may produce the desired effect

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A bolt of lightning has just shot through my head and as usual I’m doing a big, Billy Jack to the back of my own head! Am I the last guy to understand this? You guys are all laughin’ at me, ain’t ‘cha? :unsure:

 

OK, so the pattern we are seeing as a result of the thermal cycling is not the *elements* and stuff segregating themselves, it is the differences in the resulting microstructure that we are seeing. Right? I mean, I accept the metallurgical fact that the alloying elements are not likely to be segregating. They pretty much stay where the heck they ended up when the steel was poured/rolled/hammered but the crystalline structure that results because of the location of these elements is what we are seeing. Kind of like a hamon or hardening line in a mono steel blade….we see the varying *microstuctures* in the polished/etched steel.

 

And the reason that the steel transforms into varying crystalline structures is because of the propensity of the various elements that are banded into various areas to use the available carbon that is in solution at temperatures at (or near) critical. So the manganese/chromium/molybdenum bands that have been present in the steel since its creation and tend to be segregated to some degree anyway force slightly different transformation products as the steel cools.

 

Right? :huh:

 

Throw me a bone here I’m starvin’! Do I get it? Or am I still dreaming. The alloy banding is a fact. What we are exploiting/modifying as blade makers by thermal cycling is the microstructure that shows up as lines and areas of different color/luster and light refracting qualities….the various alloying elements ain’t going nowhere.

 

Brian

Edited by Brian Vanspeybroeck

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Nature wants to achieve maximum ENTROPY! Entropy is disorder.

 

if you accept all that, someone explain why metallic crystals are so well ordered? After all, crystals are NORMAL!

 

Actually nature wants minimum energy AND maximum disorder. Crystals are highly ordered BUT are the lowest energy configuration of the atoms. So you end up with a fight between the two. AND its possible for both to win because its only the entropy of the universe that has to increase. The local entropy can decrease without violating thermodynamics.

:blink:

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drermer, you, sir are a scholar! Yep. Now go explain normalizing to Tai! :D

 

Brian, Yep. As soon as drermer gets back, YOU get to explain normalizing to Tai! :P

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Brian , yes that's what we've been telling you ! The bands that you see are bands of different chemical composition, therefore have different hardenability,therefore have different microstructure , therefore polish and etch differently, therefore people say 'what is that?'. :rolleyes:

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I have a sneaking suspicion that Tai understands normailzation quite fine. I think he likes to pretend he doesn't so he can have fun tweaking people.

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Brian , yes that's what we've been telling you ! The bands that you see are bands of different chemical composition, therefore have different hardenability,therefore have different microstructure , therefore polish and etch differently, therefore people say 'what is that?'. :rolleyes:

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Whoo hoo! Your on my resume', Mete. :blink:

 

You, Sir, are *proof* that I have actually learned something!! ;)

 

But there ain't no way I'm explainin' *Sh%T* to Tai....that guy knows more by osmosis than I'll ever figure out. I'm happy to to have a revelation of my own now and then.

 

I'm goin' to the basement shop and making tanto with a pattern *and* a hamon without having to pattern weld and wake up the neighbors. And if any of you guys ever come up to my table at a future knife show and tell people how it's done I'm gonna *SmAcK* ya so hard your babies will be born with crossed eyes!! :D Then I'll buy ya a beer.

 

Brian

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If Tai truly understands normalizing, or heat treating in general, and he obscures the issue to "tweek" people, he does an enormous disservice to the bladesmithing community.

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If Tai truly understands normalizing, or heat treating in general, and he obscures the issue to "tweek" people, he does an enormous disservice to the bladesmithing community.

22955[/snapback]

 

Well, the Dude gets results...whatever his methods or whatever he knows (or doesn't know) the pictures of his stuff and the actual knives of his I have handled are pretty shwanky. Real earthy and user friendly. Real functional and well done. They have a lot of spirit and they make you wanna hold 'em and play with 'em.

 

Disservice? Well, I feel he has served me well and given me much food for thought and perspective. I doubt he'll ever go down in history as a metallurgist but I doubt that I can pass that test. B) Blade smiths and knife crafters all seem to use what works best for them. Some of it is down right disconcerting to us edumucated

individuals but I am simply a lowly experiementer with a passion to make stuff sharp and shiny. Tai's way ahead of many of us whether is ideas about heat treat and metallury are somewhat on the, shall we say, eccentric side or not. I need tweaked now and again. Other wise I get all cocky and full of myself.

 

Tai is OK. Don't hate him 'cause he's beautiful. :lol: You don't have to be *nUtS* to make knives for a living but it helps....just look at Tai! ;)

 

Brian

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I can understand that opinion. If you have questions about metallurgy,I'm sure Tai will be happy to answer them.

Edited by RKNichols

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Hello All,

I have tried several times to respond to this tread, but have not had my messages "take" on the list.

 

I spoke to a material Science Prof at Northwestern about alloy banding and the effects of and for.

Basically he said what I had thought...that given the conditions most structures form larger structures. So given the conditions carbides will form larger groupings of carbides. What those conditons are is easy enough to find in most met texts ---alloy, cooling curves and the effects of time at temp for those alloys.

 

As to entropy and disorder and such.....well, there is a lot more order out there then not (higher math and physics aside). I say higher Math and Physics aside because the search for a unified theory of all the stuff out there is still that......a search.......and if you want to discuss string theory and the four forces we know of in the Universe then find someone else to debate with besause I am not all that conecerned (unless I get put in charge of such things....which would be a grossly poor choice should that occur).

 

Alloy banding was discussed at length during WWI and WWII when it came to producing large amounts of steel quickly with whatever could be melted down. I suggest folk who are really interested begin there as the shear weight of the texts had crushed my interest in the subject years ago.

 

As to not having banding in a steel heatied for prolonged periods at , what was it? 1950F?

I suggest heating the materila to 2400F for 30 minutes, then a step down thermocylcling from these temps to room temp with a soak of three minutes at each (1550, 1500,1450,1400,1350) and a final soak for 15 min at 1300F. Then look at the structures.

 

Alloy banding is just that......the alloys put into solid solution during the melt can and do form grounpings of themsleves and other alloys. If these groupings are not broken up then during forging or rolling or pressing they tend to allign in the direction of flow and appear to us as bands (they are actually individual clusters like the dots that make up newspaper pictures).

 

Given the right heat and duraion these same alloy elemnts can form these groupings from "correctly" make steel. I have seen them in everything from 1050 (where other products made by other smiths of the same batch of steel failed to produce the same effect) to the higher alloy materials like 52100, 5160, D2, S7, H13 and A2. I assume other steel will do the same, but those named are ones I have seen the effect in personally.

I think Kevin Cashen showed some banding in 52100 on the "Cafe" last year when it was discussed there.

 

I guess what I need to say plainly is that it is an interesting effect and can be used for adornemnt of the blade, but it should be discussed as what it is....the grouping together of the alloy additions in the steel. These additions by the way were intended to be evenly distributed in the steel to add to its properties and most of the reaseach I have foiund say it is not a "good" thing to concentrate them into such bands as it may create localized areas of weakness or areas of inconsisntant properties. Most of modern steel manufacture is geared toward making a very even distribution of all these alloys.....such as the CMP stuff.

 

Ric Furrer

Now I have to go shovel the driveway because of the snow storm that stalled over my house.

(ps. this message was not spell checked-- sorry)

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I guess what I need to say plainly is that it is an interesting effect and can be used for adornemnt of the blade, but it should be discussed as what it is....the grouping together of the alloy additions in the steel. These additions by the way were intended to be evenly distributed in the steel to add to its properties and most of the reaseach I have foiund say it is not a "good" thing to concentrate them into such bands as it may create localized areas of weakness or areas of inconsisntant properties. Most of modern steel manufacture is geared toward making a very even distribution of all these alloys.....such as the CMP stuff.

 

 

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Thanks for your input, Ric. Regardless of the research, do *you* feel that exploitation of this kind of patterning/banding of mirostructures within the blade will have a pronounced effect on the performance of the blade? I mean, in your opinion, would a normal guy (customer or blade maker) be likely to tell the difference between a 5160 blade that does not exhibit significant banding and a blade where the banding was exploited to get a more visible pattern in terms of edge holding and toughness?

 

Thanks for keeping that snow where *you* are and not letting it get at us guys further south. :)

 

Brian

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Ric,

 

Thanks for your very informative reply!

Now I got a much better Idea of what I was looking at and how it was created...

 

I'll soo try some experiments with the temperatures/holding times you have given and see wether I'm capable of reproducing the effect...

and I maybe will do some comparative destructive tests...

 

thanks

 

dan

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Thanks for your input, Ric. Regardless of the research, do *you* feel that exploitation of this kind of patterning/banding of mirostructures within the blade will have a pronounced effect on the performance of the blade? I mean, in your opinion, would a normal guy (customer or blade maker) be likely to tell the difference between a 5160 blade that does not exhibit significant banding and a blade where the banding was exploited to get a more visible pattern in terms of edge holding and toughness?

 

Thanks for keeping that snow where *you* are and not letting it get at us guys further south.  :)

 

Brian

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Brian,

I think that all things being equal the banded blade will perform to a lesser degree then one not abused in such a way.

A question I have is why anyone would do such a thing to a steel to begin with? There is far greater control of pattern and properties via pattern-welding then banding a modern steel.

Remember that industry spent a great deal of time and money to research why this occurs and prevent it from doing so.

I also fear that such a banding proces will be used to confuse and "con" the public.

 

Ric Furrer

Sturgeon Bay, WI

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Brian,

I think that all things being equal the banded blade will perform to a lesser degree then one not abused in such a way.

A question I have is why anyone would do such a thing to a steel to begin with? There is far greater control of pattern and properties via pattern-welding then banding a modern steel.

Remember that industry spent a great deal of time and money to research why this occurs and prevent it from doing so.

I also fear that such a banding proces will be used to confuse and "con" the public.

 

Ric Furrer

Sturgeon Bay, WI

23110[/snapback]

 

Well, your views have rather startled me...in a good way. It never occurred to me that the patterns produced could be used to delude the public or con buyers. I accidentally produced the pattern a while ago while playing with heat treating and always wondered if this phenomenon could be used to doll up an otherwise Plain Jane blade made of monosteel. I don't have the facilities to produce pattern welded steels and, frankly, found the random banding pattern to be pretty dang attractive as it was without being able to manipulate or control the pattern. Hell, if I ever get to the point where I *can* make my own pattern welded steel I'll probably spend a lot of time and effort folding and manipulating the pattern just to get the cool pattern that the banding provided!

 

But the risk of ending up with sub par performance takes the fun and wonder right out of it for me. And I certainly wouldn't want anyone to get the idea that I would be trying to exploit a sales angle while purveying sub par blades made of damaged or abused steel. Has this kind of thing been done before...I mean the exploitation/con aspect of it? It sounds as if others have already encountered makers using this phenomenon for evil purposes.

 

Thank you so much for your input, Ric!

 

Brian

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