Try this.

"Have any of you noticed that martensite is not mentioned in the analysis of Wootz blades?"

Mr. Fowler,

It is a unique property of the internet for me to be able to address you, and I thank you for any time you may devote to this discussion. My understanding of metalurgy is very incomplete. My training in chemistry and a sometimes inconveniently inate curiosity as to why things are as they are prompts me to pursue this further.

I have read that working at too high a temperature will destroy the pattern of wootz or for that matter some other "damascus" patterns. Heating a blade to non-magnetic so that it can be cooled to promote maximum formation of martensite via quenching in the edge seems to me to fall in this area. Does it follow that desirable functional properties of the resulting blade of wootz or damascus are also lost, or is it merely a matter of appearance.?

I have seen some discussions that seem to suggest that the wootz metal could be described as a dispersion of hard carbides in in a soft matrix. This appears to me (perhaps in my ignorance) similar to the, modern, so called "dendritic steels" which have not been widely accepted so far. Please, if you can, clarify this.

I also have to wonder if the pattern of wootz and damascus as a proof of the smith's skill at some point became somewhat perverted as has in our time the current ideal of "sharp, crisp grind lines" even though the actual performance of the blade may be reduced as in the example of very thick hollow-ground blades that bind up when cutting something thicker than the blade. Perhaps the "best" (cynically most expensive) knives and swords are are/were as vulnerable to fashion as everything else? Particularly when they are are a staus symbol instead of a tool/weapon? I don't mean to denigrate collectors, but I wouldn't buy a modern knife if I didn't mean to use and sharpen it, same as I wouldn't buy a painting to lock it in a dark safe. That's what precious metal ingots are made for, and they are all the same.

Lastly, to keep somewhat in the topic of this forum, I and I suspect many others, would be greatly appreciative of any comment that you might have on the Nepali heat-treating practices. As I understand it, they take a relatively thick blade of 5160 above critical temp out of the forge, pour a measured amount of water onto the edge, which hardens it, then the residual heat in the thick spine seeps back in to temper the edge. The slowly-cooled remainder of the blade is very tough due to the slow cooling.

I appologize for throwing this all at you at once, but it seems perhaps an opportunity for us all to learn something. I thank you again for your time.
 
This is not a forum, nor even a collegium any longer, but Himalayan Imports Cantina, Stage Stop, and University.

Now that Ed Fowler and Firkin have given us a preview of a Doctoral dissertation in progress, those who understand any of it line up behind Firkin, the rest line up behind Uncle Bill, the Junior High level behind Yvsa, and the other kindergarteners follow me back to our classroom before I get completely lost.:confused: ;)
 
Firkin, so that's why Ed Fowler observed the absence of Martensite in Wootz.

Thanks.


munk


Rusty, where'd you go? You promised me Arts n Crafts before I took my nap.
 
Hey all,

Great discussion thus far. My interest as a collector is in the properties of steel so this thread has my full attention.

Does anyone know of many examples of knife sized wootz blades? Was wootz made specifically for sword sized blades that needed to be tough enough to handle great shock without breaking? Does the lack of a hardened edge infer that the blade has a reduced performance potential, or were they made for a purpose that didn't require it, such as for penetrating armor?

-Jose
 
Firkin: You ask some very interesting questions, I will do my best.
The patern of Wootz indicated a very tough blade, probably the best blade of the time. The cut part came from blade geometry, the tough from low temp forging and maybe chemistry. The pattern guaranteed tough.

Damascus means a pattern, those produced by forge welding layerers of steel, wire, and other patterns are not supreme cutting blades, they are pretty, some are tough. These do not lose any pattern by heating to critical (non-magnetic) and quenching, at least those I have worked with, sometimes blade smiths may chose to not harden blades as it can result in a distraction from the visual pattern if edge quenched.

I work with one steel, low temp forge 1625 f and lower to encourage fine grain structure along with many thermal cycles and edge quench. When it is etched a pattern appears, I call this Homogenous Damascus, (my choice of taxonomy). Heating to critical does not promote grain growth when the blades are only heated to critical for a short time, thus the benefit of multiple quench. One interesting lesson we have learned (at this time) is that ultra fine grain does not necessairly mean tough, a matrix of ultra fine grain (12 and finer) the and finer is very significant. These blades can be both tough and cut very well. A mixture of fine randomly dispersed hard chromium carbides in a softer matrix provide cut and ease of sharpening. A blade that rockwells 60 can scratch a steel that Roclewlls at 62, due to the fact that it is very hard to test a #12 carbide.

The frontier I enjoy the most at this point in time is the interaction between the martensite cone (kind of like an inverted v) that forms within the edge quenched blade and the surrounding unhardened steel at the 'temper line'. Many variables come into play, it is a dynamic ballet or symphony to witness.

I bleieve dendritic is another ball game, large dendrites that would reduce tough due to large grain boundries that would not be condusive to slip, therefor would tend to break down in flex.

The blades that win in show competition are those that please the judges, many of todays judges haven't spent much time evaluating performance. You are correct when you feel performance is not the grail sought.

I have not had the opportunity to test any blades subjected to the Nepali heat treating practices, you should be able to gain some insight into their performance qualities by examining how they test their blades. If it makes sense, they may work.

I appreciate your questions, this has been an opportunity to put a lot of thoughts for other to consider. I any resders have questions or thoughts I welcome your input.

Just for grins, it is kind of hard to keep performance ones single goal. I recently completed what I consider my all time most correct blade. The grain was as uniform, linear and symetrical as any I have ever achieved. I spent many hours studying the blade and was satisfied that it was one of my best. Later I got the thinking that it would be kind of different if I made one with a ladder pattern. I tried my idea on Angie (my bride). She didn't ban an eye, she asked "will it cut better?" I replied "probably not." She asked "will they be tougher?" I replied, "No the pattern would limit grain slip and they would not be as tough." She asked "What for?" I got to love her, she put my idea where it needs to be, I have better things to do.

Take Care
 
I recently completed what I consider my all time most correct blade. The grain was as uniform, linear and symetrical as any I have ever achieved.
Click to expand...

Here's a pic for those who are interested.

orig.jpg


-Jose
 
Just out of curiousity the blade above is mono-steel and not pattern welded correct? The activity that is appearing in the steel is from heat cycling? I had been told in the past that this occurance was alloy banding, so am I correct in understanding Mr. Fowler's explanation that this is instead evidence of the grain structure within the steel? Magnificent work by the way.
 
The steel is 52100E, forged from a 5 1/2 inch round bar. I received it as a 3" x 3 x 14 inch bar. From that bar, the blade received 18 full normalizeing heats during the forging process, all forging at 1650 f. and lower. Many forging heats were required. After the blade was forged, two flash normalizing cycles, one complet normalize, three annealing heats at 800f. for 2 hrs each, three edge hardening quenches, 24 hrs apart, cycled each time to about 0 f (outside temp), then three tempering heats for 2 hrs each at 330 f., 24 hrs apart, cooled to about 0 f. each cycle.

Banding may be present, but not visable in this etch, it would be microscopic and we have not detected it in laboratory analysis.

Thanks for the kind words, very few realize what they can see in this blade.
 
Federico,

Does this picture display the "alloy banding" you referred to?

orig.jpg


It was made by Bill Burke, Ed's student. The bands are raised on the steel and I've been told they're formed by elements in the steel that weren't "burned" out due to the low temp forging process. Does anyone know any more about this and go into more detail?

-Jose
 
Jose yes, though I felt it was more visible in the first pics. As to how I understood alloy banding, was that when forged the different alloys in the steel would sometimes clump together being visibile when etched giving a damascene look to mono-steel. I was also told that it was somewhat common in 5160 so I was not surprised to see it happening in HI khuks when I etched em. However I was under the impression that Mr. Fowler was saying that what we are seeing as far as activity in this steel (aside from the transitional zone in the differential hardening) was not alloy banding but variance in grain structure. The more I think about it, the more I like how he explained it, and the more it makes sense over alloy banding. Again beautiful knife.
 
"I work with one steel, low temp forge 1625 f and lower to encourage fine grain structure along with many thermal cycles and edge quench. When it is etched a pattern appears, I call this Homogenous Damascus, (my choice of taxonomy)."

Fascinating...

If I understand correctly, it is your opinion that the pattern and toughness of the old wootz blades in large part (or entirely) resulted from low temperature working and heat-cycling. This would imply that much of the search to "re-discover" a lost wootz "formula" has been somewhat misdirected? And that wootz blades with the finest, most subtle patterns would be the ones of highest quality? Also, the old bladesmiths would go to the trouble to etch the final product, though intended as a working blade, because a visible pattern "guaranteed" toughness and allowed him to command a higher price commensurate with the added effort of low-temperature forging?

I may be mistaken, but as I recall, analyses of wootz generally indicate a quite high carbon content, and that is the direction that many of those attempting to replicate wootz have taken. If I recall correctly many of the modern efforts have resulted in very hard, but often somewhat brittle steels. I wonder what would happen if some of these modern attempts at making wootz were forged by the methods that you advocate.

"I have not had the opportunity to test any blades subjected to the Nepali heat treating practices, you should be able to gain some insight into their performance qualities by examining how they test their blades. If it makes sense, they may work."

Rigorous testing would be interesting, folks here have on occasion wondered just what the hardened area looks like inside the blade.

I think the main test, when performed, is using a file on the edge. The blades are quite thick, and convex, or close to convex. They are certainly not the best choice for a fillet knife, unless for whales and flexability is not an intent. The test that makes the most sense is using it, and if it breaks or the edge fails, the smith owes the customer another knife. That's pretty much the way Bill operates too.


Here is a description of Nepali heat-treating from the HI website:

Water was the quenching medium for 2500 years or so. It was used in Nepal "since the beginning" and a kami's skill is largely passed down from one generation to the next. The hardening of the blade is really an art rather than a skill.

Bura was giving me a lesson in hardening a couple of years ago --"setting the pine" they call it. Pine = hardness.

Bura lectured as he did the work.

"Color is very important. See this color? The blade is not hot enough. See this color? The blade is too hot. See this color? It is just right. See the color at the tip? See the color at the cho? These all must be just right before you start to pour."

When the blade color was just right he began to pour from his pitcher.

"You cannot pour too fast and you cannot pour too slow. You must pour just the right amount at just the right speed. Watch the blade change color. You will see red, purple, green, in various shades and then black. If you do not see the color change seven times you have missed and must begin again. See it has changed three times already. There, again. And again. Again, and now it is black. It is finished and the blade pine is just where we want it to be. It is very hard here (pointing to the
chopping area) and not as hard here and here (tip and bottom of blade). This knife is perfect."

I took a file to check the blade and Bura chuckled. "You are wasting your time," he said.

And I was.

--Bill Martino, 5/2002

Here's a photo of a kami hardening an edge:
kami11.jpg


Thanks for some very interesting insights. BTW, I think your book just made it onto my shopping list.:)
 
Fed,
The bands in Ed Fowler's knife are a result of the 10 different mixes of products in the steel, different percentages of martensite,pearlite, cementite, ferrite, and possibly bainite.
Firkin,
I think any proper wootz with carbide banding and pattern will be tough, not brittle. Wootz is an entirely different material than other steels. It's difficult to compare them to each other. It really is like apples and oranges: two fruits but very different characteristics.
Nepali methods of heat treating give a very fine grained martensite at the edge and two or three other product bands depending on the smith. It's really amazing considering the conditions where they work.
 
Art I thought the contrast between the martensite, cementite, pearlite, etc... would be seen the transition zone in the differential hardening. The banding Im talking about appears throughout the zones of hardening, from the hard martensite edge, through the transition zone, and up to softer pearlite body.
 
Fed, I think I understand now. I believe the pattern is due to carbide layering, which is different from alloy banding. Carbide layering is thought by many to be the reason for "natural" pattern in wootz. Wootz is unique in that if you overheat and lose the pattern you can sometimes bring it back by thermal cycling; with 52100 when the pattern is gone I think it's gone forever.

52100 behaves a little like wootz because it has the property of carbide retention. If you heat it to about 1800F you put all the carbon into solution, then when you cool it the steel forms carbides of iron, chromium, etc. If you then heat it again to 1350-1400F you can re-austenize but the steel retains some of its carbides which pin the grain boundaries, thus preventing grain growth. In fact, cooling the steel results in smaller grain; there is some disagreement on how many of these cycles will continue to reduce grain size. This is also why, as Ed says, you can forge carefully at 1600-1650F without grain growth.

You have to take my opinions of wootz with a grain of salt. I've never made any but am going by what people like Al Pendray have said in lectures and writings.
 
Art very interesting stuff. So is the carbide retention unique only to 52100? When I first encountered this phenoma it was with blades made of 5160. At the time I was told it was alloy banding, and that was something unique to 5160. What I thought Ed was saying was that instead it was the visible grain structure of the steel. However, if Im understanding you correctly are you instead saying it is the carbides within the steel? I have seen this phenomena in a few blades with pile construction layers, and at the time just assumed it to be varying alloys within the different composing steels. So now instead it could be either the carbide layers or the grain structure?
 
Fed, first let me say that what Ed calls grain structure and what I call carbide layering showing up with etching might easily be two terms used to describe the same thing. Ed certainly knows more about this than I do and it's his blade to boot. I believe the carbides go to the grain boundaries, so an etch which shows the layered carbides would show the grain outline.
The reason I say carbide layering instead of alloy banding is because there are smalls swirls etc. in the pattern which makes me think the effect is lamellar (sp?) instead of linear. I think of alloy banding as a linear effect without specific layers through the thickness of the blade. The photo of Bill Burke's blade looks more like what I call alloy banding.
This is all further complicated by the fact that so many of us call the same thing by different names. If you showed Ed and Bill's blades to a metallurgist I'd bet money that he'd tell you he had to take the blades to a lab, break them, etch the break and use a microscope to identify the contents of the blades. If you pushed him, he'd say it might be this or it might be that and he couldn't tell which without more examination.
One of the frustrations of working steel is that a view of the surface (without any background info on how the steel has been manipulated) just doesn't tell you much about the internal structure and properties. That's why you want to deal with people like Ed and Bill, who are totally honest and who earn their reputations by selling only the blades that meet their standard of acceptability.
Maybe Ed (or Bill) will say more.
52100 is the only steel I know of that retains carbides to this extent, although some others probably do and I just don't know it. When Al Pendray was trying to make wootz, John Verhoeven (then a professor teaching metallurgy in Iowa)suggested he experiment with 52100 because its carbides behaved somewhat like those in wootz.
 
Thanks for the follow up Art. I think I am following what you mean. So the effects in Ed's blade is probably the carbide's outlining the various grain's, while the pic of the second blade (I had thought it was Ed's blade at a different angle so I guess its a different with a completely different maker) may be displaying alloy banding? I had originally had the opposite thought for the same reason you had listed for thinking that it was the opposite way around? :confused: If that makes any sense. I had thought the swirly things in Ed's knife that mimicked a lamellar pattern(I think Im using the term the same way you did) was an indication of alloy banding, versus the more linear effects in the second blade (which at the time I thought was the same knife and only had the linear effect because of lighting). Then again I suppose youre right and we could just be throwing around different terms for the same things further confusing things.
 
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