concerning damascus...

[J. Neilson]

One of the books I got for X-mas was Wayne Goddard's Wonder of Knifemaking. It's a great book but he makes a comment in the damascus section (page 114) that I can't stop thinking about. It states:

I welded up layers with many combinations of materials and numbers of layers. Testing showed me that strength was lost by the material becoming homogeneous after 200 layers.

Am I reading this right or missing something? Wayne is saying that damascus blades get weaker over 200 layers but, the ABS minimum for damascus is 320 layers? I'm confused.


Also,
Wayne mentions edge quenching damascus. I normally edge quench my high carbon blades and did the same thing to the first few damascus pieces I did. I got some odd looks and comments from folks because of the etch line in the blade. Since then I've been doing full quenches in damascus. Pretty's great but, if pretty don't cut what's the use. Not that the full quenches make bad blades, I just want to make the best working blades I can. Any comments or opinions would be great.

 

[indian george]

J. We all have are own opinons on such matters, the content of the statement must be interpreted in the manner in which it was intended.
HH is here.

 

[kile]

I have no idea about the layers and homogenizing, but as far as differentially heat treating a smaller blade, I just don't see the point. I have edge quenched damascus blades, and I didn't like the look. But I don't see the point in edge quenching anyblade under 4". I don't think the differentially hardened damscus looks bad on bigger blades. Just my opinion
Kyle Fuglesten

 

[B . Buxton]

I don't know J. about the strength, but I was always told that the more layers the damascus the stronger the steel. It always made sence to me, more layers meant more manipulation and combining of the differnt steels. As for the edge quenching damascus, I edge quench about all my blades, damascus or not and I like the look and the performance I get. I look at it this way, there's no one way written in stone, and we all have different likes and dislikes. If people don't like my blades then they don't have to do them like I do. Here's an edge quenched blade and I think it looks great and so did the person that bought it.

Bill

 

[mete]

If you start out with .40% carbon and 1.00% carbon in damascus and keep folding you eventually get a homogenious .70 % carbon.This .70% may have different properties than the .40/1.00% layers and thus may seem to have lower strength.

 

[MaxTheKnife]

J., I'm betting it was a typo and he actually meant 2,000 layers. It doesn't take long to get there you know. I really don't have an informed opinion about layers and homogonizing of the steel. You should write in to his column and ask him about it. Or find his email address and email him. I'm sure he'd welcome the opportunity to exlain it to you.

 

[Pinoy Knife]

Ogg i agree call or forward this to Wayne , he is a good guy and im pretty sure he would be happy to clarify any misprint . i also believe the layer count to be more like 2000 not 200. if you think about it a 320 count bar would be a homogenous ladder / raindrop . it must be a typo .

 

[Guy Thomas]

I think Mete is on the right track here, unless there is a barrier of some kind (like pure nickel), carbon migration will occur in pattern welded steel within relatively few layers of forge welding. I don't believe Wayne is saying that the PW billet of high layer count is going to be weaker becaue it has high layers, I think he is saying that the strength characteristics of the individual components of the initial billet are going to be lost as the billet approaches homogeneity and therefor has it's own unique strength characteristics.

Does that make sense?

Carbon migration is well established, but I don't recall anyone mentioning the migration of other alloying elements (such as chromium, manganese, silicon, vanadium, etc.). Do they also migrate to a greater or lesser extent than carbon?

 

[Guy Thomas]

I also meant to add my opinion on the edge quench vs. full quench on damascus. In my opinion on an average using blade the benefits of a edge quench are over-rated. Tempered martensite is extroardinarily strong (as anyone who has deliberately broken blades knows)and the breaking point is well above practically any intended use of a knife. Therefore it makes sense to fully harden damascus in order to achieve a overall continuity in the etch. I also like to edge quench mono steels (short and long blades) because I like the hardening line (hamon if you will). A proper formation of pearlite (as in the back of an edge quenched or clay coated heat treated steel)is very strong as well and additionally is resistant to breaking. A longer blade subject to heavy use such as a camp knife, sword, etc. may very well benefit from the diferential heat treat. A survival knife intended to be abused in extraordinary situations might also benefit (from an edge quench) since a bent kinfe is infinitly more useful than a broken knife.

My opinions only, but based on what I hope is common sense.

I know the ABS uses the hard edge/soft back model on it's test blades, I'm an ABS member myself and hope to test someday. However I don't see this as an advocation of the ideal heat treatment for a knife but rather requirements that demonstrate the smith's knowledge of ability to heat treat for specific results. Perhaps I'm a bit naive on that count, but then again perhaps not.

 

[Ed Schempp]

There are many factors at hand that are not addressed. The size of billet has alot to do with the finished product. The larger the billet the greater the mass to surface area, you will loose less to scale than with a large billet. How many times the billet has to go into the fire to accomplish the shaping of the piece, has alot to do with how much carbon you burn out of your billet. The forging temperature has alot to do with the quality of the finished blade. Edge quenching Damascus gives you a blade with steel in different states. Etching the material will give different effects on different states that the material exists. Martinsitic steel gives the best etch for appearance of the steel. Martinsitic steel that is etched will show the pattern well with a good etch from about 160 degrees of view. Annealled steel etched will give a good pattern from about 30-40 degrees of view. The refraction of light from the surface of the steel will be different depending on what kind of crystaline structure you reveal. A full quench on a damascus piece with a soft-back draw will give similar preformance and a uniform etched pattern. Thanks ...Ed Schempp

 

[Kevin R. Cashen]

I would like to start out by saying that I have no desire or reason to contradict Wayne. Even though I am not a $50 knife shop kind of guy, I was impressed with the amount of really good information in the “Wonders of Knifemaking”. I do not recall every little portion of it, however, so I am not familiar with the section that is being referred to here.
I am not sure what is meant by “strength” here, so the statement is open to some interpretation. Strength is usually relative to higher hardness, and is not to be confused with “toughness” which can often come with lowering the Rockwell numbers. If here, “strength” refers to hardness and the ability of the edge to resist deformation, then more welding and folding could very well result in a lessening due to more carbon loss from the extra time at temperature.

I am in the process of an ongoing series of tests involving pattern welded mixes, the first series of which I presented some of my results in a talk at the 2003 Ashokan Bladesmithing seminar. A major portion of my testing involved impact strength, both notched and un-notched blades cross-sections. After studying the data I have many more questions than answers, but one of the things that is consistent enough to be conclusive is the affects of the layering of different alloys on impact strength.

All of my tests were done at 320 layers, starting with 5, in a random pattern. There was no bending in a vice or guessing, I have the actual foot pound/Joule numbers to work with for my conclusions.

Due to the metallurgical fact of carbon diffusion, varying levels of carbon alone will have little affect on the overall performance of pattern-welded steels. The addition of low carbon steel will increase impact strength due to the increase of proeutectoiod ferrite (i.e. lower carbon has greater impact strength) but due to carbon diffusion, the process of folding to any larger amount of layers alone will not affect this. Within the first 3 to five folds you will loose the low carbon and high carbon layers, as they all equal out to medium carbon. You add impact strength at the expense of hardness and edge holding. My test were not necessary to know that adding low carbon steels to the mix did nothing more than dilute the billet as a whole. Any mix resulting in a total billet carbon content of less than .6% will start to suffer in as quenched hardness.

Furthermore the addition of softer material only seemed to add to impact strength when it was based on carbon. Pure nickel added nothing to the impact strength of 1095 and the fractured surfaces showed no signs of differential behavior in the break, i.e. one could not see the difference between the way the steel broke versus the nickel, from the broken end it appeared as solid steel.

The “toughness” added by using low carbon layers is a result of those layers depleting the higher carbon layers, and once equilibrium is achieved these affects are final.

Mixes that depended upon alloying differences, other than carbon, presented a different result. Substitutional alloys don’t move around as readily as carbon so one can get some added impact toughness from such layers, but the final steel can only be as good as the better layer added. For instance mixing L6 with 1095 will give better impact performance than pure 1095 but it will not get better than the L6 alone and it will normally not even be quite as good, I did find some anomalies in this with select steels that need more investigation.

True “homogeneity” will not be achieved with any amount of folding, due the fact that every fold introduces a weld zone of different composition. For example, katanas can have as many as 10,000 or more layers, yet we can still see a definite pattern in the steel, if it were “homogenous” it would appear as solid metal. Although the layers are very thin at 200 layers they are still fairly pronounced and individual, as far as metallic alloys (they will have lost there original carbon content, for certain). You need to go higher in the folds for the lines to begin to blur as far as the alloying in the layers.

Cutting ability, and the affects that layering can have on it, is a whole other story and so big that I won’t even touch on it here.

 

[Kevin R. Cashen]

Originally posted by Silent
I also meant to add my opinion on the edge quench vs. full quench on damascus. In my opinion on an average using blade the benefits of a edge quench are over-rated. Tempered martensite is extroardinarily strong (as anyone who has deliberately broken blades knows)and the breaking point is well above practically any intended use of a knife. Therefore it makes sense to fully harden damascus in order to achieve a overall continuity in the etch...

I couldn't agree more.

This is just my opinion, which is base solely upon a matter of personal taste, but I have differentially hardened damascus and found the resulting etch to be so unattractive to my tastes, that I now avoid it whenever possible.

I have also found enough of a difference in the etch from a heavier temper to go out of my way to work around it. I always draw my ricasso area back to facilitate the filing and fitting of the guard, but I noticed a distinct line in the etch where I had tempered, so I now save that draw until after the etch and then clean up the oxide colors later.

 

[mete]

Kevin , glad to see thast you're getting good use from your new impact tester. It's interesting that nickel doesn't change the fracture. You ought to find an expert in fracture mechanics to get an explaination........To explain "substitutional alloys " for the others - it should be sustitutional elements, that is those elements that are similar in size to iron such as nickel ,chromium etc. They will sustitute for an iron atom in the iron crystal. Carbon is an interstitial element, considerably smaller than the iron atom and will fit in between two iron atoms in the crystal......BTW assuming that you use borax for your flux between each layer you should find some oxides and some borax.Does the borax remain as a compound or does some of the boron enter the steel ? I ask that because boron has a marked influence on hardenability of steel .

 

[Kevin R. Cashen]

My first round of research was done before I had the Riehle so I used another impact tester. I am eager to get to it with the next round now that I can really zero in on the numbers. You are correct in that I should refer to them as substitutional "elements", but I have gotten into the habit of substitutional alloys versus interstitial alloys when talking about richer tool steel versus the plain carbon steels. I have got stuck on thinking in terms of the differences in the alloy as a whole as opposed to the actual position the atoms take within the lattice structure.

Although it is small the carbon atom has found a powerful place to sit with the atomic lattice of iron. I was working on some illustrative diagrams the other night on the computer, substitutional and interstitial. Just with a simple graphic, the interstitial atoms made more work for me to move all of the iron atoms to accommodate the distortion in the picture. It was then that the simple geometry of it all started to really sink in. Slipping little atoms in between big atoms can easily have as profound an influence as substituting an atom with an equal or larger one. And, of course, when you combine the two plenty of distortion can take place.

 

[Kevin R. Cashen]

Originally posted by mete
...It's interesting that nickel doesn't change the fracture. You ought to find an expert in fracture mechanics to get an explaination

I thought it was very interesting. When you combine this with the edge retention results, it becomes very obvious that that only reason to add pure nickle to the mix is to make it pretty, as nothing but decreases in performance resulted. Pretty much the same with any of the low carbon mixes I tried. 1018 and O1 only seemed to result in crippling the performance of the O1 in all categories except impact, which were inconclusive since the stuff just wanted to bend and bind in the machine, instead of breaking. To those who like the idea of a bend instead of a break, I must point out that it took very little load to bend it. Other alloys that reached full hardness, tempered well and cut like crazy, did cleanly and completely break, but it took much, much, much more force to do it. Un-notched 58HRC L6 actually challenged the limits of the machine I was using (with the Reihle 240 foot lb. capacity, this should no longer be an issue).

 

[J. Neilson]

Wow!
That's a heck of alot of info there Kevin. Makes me feel like a real knot-head. My best testing medium is usually a cow. Those are some really interesting points to consider.

I just want to point out also, that I was in no way diagreeing with anyone, I was only curious about what I had read and was interested to get the opinions of others. I realize that many have their own methods and opinions on damascus. Since I am still building mine, I thought I'd dip into the collective for maker's minds.

While I'm at it though...
Have those that have used 20 Mule Team and Anhyd. Borax noticed a significant difference between the two? This was also something mentioned in Waynes book.

 

[Kevin R. Cashen]

Originally posted by J. Neilson
Wow!Wow!
That's a heck of alot of info there Kevin. Makes me feel like a real knot-head....

You think you feel that way! When I first started compiling the numbers and the data, I never felt so lost and ignorant. I was ready to title my lecture "Is the world flat after all?!?" There were things that I just didn't want to accept because they challenged everythiugn I ever believed about this material, but that is the thing about cold numbers, they don't have an agenda, they just are. There are some other things that I observed that I want to repeat a couple more times before I am confident enough to even talk about in public or soem folks would think I have totally lost it.

...I just want to point out also, that I was in no way diagreeing with anyone, I was only curious about what I had read and was interested to get the opinions of others. I realize that many have their own methods and opinions on damascus. Since I am still building mine, I thought I'd dip into the collective for maker's minds...

I didn't see any disagreement in your questions at all, I put my disclaimer in because there a few things that I do differently than what Wayne usually writes about, but when I took time to look through his book, I found myself saying "Thats right, you tell em Wayne!"

While I'm at it though...
Have those that have used 20 Mule Team and Anhyd. Borax noticed a significant difference between the two? ...

Yes... the price! Well that is not entirely accurate since one is a purer form and is initially devoid of the expanding, foaming, moisture. I have been known to criticize my bladesmith friends for being so damned cheap to spring for good stuff on other areas, so I would deserve a good ribbing on this one if I focused so much on the cost aspect. The main selling point that I get for the anhydrous stuff is the fact that it sticks better because it doesn't have the moisture. If this is all, it is not enough for me. The worst foaming mess I have ever seen is anhydrous that was not kept sealed in a moisture free environment, all it would do is make big styrofoam like wads, I had to ask for a box of 20 mule team to finish the demo.

At home I mix a small ammount of boric acid with a box of 20 Mule Team. I haven't seen too much difference in the fluxing action, but I feel that the boric acid helps the mix "wet" the steel better on initial contact.

I would have a supply of anhydrous in my shop (I'm sure it would be cost competitive with 20 Mule Team, in bulk) but I have not found a realiable convenient source for it. Perhaps some folks here on the forum could list some suppliers.?

In the meantime 20 Mule Team is available at any local grocery store and has been working fine for me for many years now.

 

[Guy Thomas]

Thanks for the information Kevin, you have been doing some valuable research with your testing, it's great that you share it like you do. Thanks for pointing out also that what was referred to as "homogeneity" earlier in the postings was actually refering to an equilibrium of carbon content after carbon migration occurs.
You have confirmed what little I know about other alloying elements not migrating as readily as carbon through the welds but I definitly need to hit Bain's "Alloying Elements in Steel" again, though I have to take that book in small amounts together with much reference to other books when it is evident that my knowledge is lacking! Does smacking yourself with the books help to absorb and understand the information?

So have your tests turned up any interesting notes for your prefered 01/L6 damascus mix?

 

[J. Neilson]

Does smacking yourself with the books help to absorb and understand the information?

Silent, if that worked, Tess would have made a genius out of me years ago.

 

[Kevin R. Cashen]

Originally posted by Silent
Thanks for the information Kevin, you have been doing some valuable research with your testing, it's great that you share it like you do.

I am only sorry that I cannot share more, for a couple of months now I have been teasing and giving bits of information from my studies, but the majority of it (and most of the really good stuff)I must keep to myself for the time being. Not that I have and secrets, anybody who knows me knows how violently I hate that "secrets" crap! But I really insist on completely verifying the more interesting findings with repeatable results before foisting more misinformation on the knifemaking business. To many people jump to wild conclusions and, in their excitment, broadcast it to become gospel. The gospel is a pretty important thing not have right.

...I definitly need to hit Bain's "Alloying Elements in Steel" again, though I have to take that book in small amounts together with much reference to other books when it is evident that my knowledge is lacking!

Good book! I believe my copy is the sixth printing. I would also recomend his collaboration "Principles of Heat Treament". When Grossman helps out the books are easier to digest. Bain was brilliant, but I think Grossman was a better writer for the common man to understand.

... Does smacking yourself with the books help to absorb and understand the information?

It could?! Smacking your mind against ruined steel in the shop seems to really do the trick

...
So have your tests turned up any interesting notes for your prefered 01/L6 damascus mix?

... Well that is some of the stuff that I want to completely verify. My pet mix showed some of the most "interesting" results in the studies. If I were too quick to reveal some of those findings, some would say that I am a bit biased. I believe that the numbers from future testing will bear out my suspicions though. But it should be said that similar results could occurr whenever one carefully chooses his steel to mix and follows the simple rule- "don't use anything in your damascus, that you wouldn't make a knife out of all by itself"

Pick a steel that really cuts well, and pick another steel that is pretty tough and cuts well and you should have a blade that is fairly tough and cuts well.