Jump to content
Klaas remmen

Georgian 'Bulat' technology by Zaqro Nonikashvili

Recommended Posts

Hi Ric, sorry to hear about the good Dr's passing... i remember reading the paper about corrosion resistance of the pillar ...and thought is was very cool

 

the task of replicating would be immense... from what i remember, they said the pillar was possibly forgewelded on its side..

 

which makes some sense as you could use a sorta battering ram on ropes to hammer sideways..

- still.. moving chunks of iron that size at weld heat would be interesting

 

the amount of charcoal fuel would just boggle the mind :o

 

i don't remember the elemental analysis of the iron but it should be there...

 

if the project has leg's... i'm positive the community will kick in and help... why i'd even jump in my clunky saturn and risk being exposed to the miasma's of the world to help out ;)

 

 

take care

Greg

 

ps.. i'd avoid the charcoal ... deforesting half of Wisconsin might be frowned upon by the PC Green people

 

 

Pillar:

Actually Greg, about a year before his death Bala was in my shop and we were talking about that very thing http://www.iitk.ac.in/mme/obituary/. It would have occurred in India though. Since his death I have considered the forging of such a thing here with a dedication to him.

 

The glass color always semmed to come out various shades of green for me if I used sand or clear or green at the start. I have not used brown glass. When I use Borax it always comes out the bottom of the crucible. :(

 

Ric

Share this post


Link to post
Share on other sites

I managed to make some metallographic pictures of the bulat of the workshop.

It's etched with Nital.

 

Here you have my bulat, it's the other piece from which I made the little knife. the worktemperature was too high, resulting in quite small cementite groups.

The matrix is hard to see, but I think completely pearlitic.

breedteklaas1.jpg

breedteklaas2.jpg

 

this is Zaqro's piece, his steel had some alloying elements like W and Cr in it (XRF analysis)

Hist structure had nicer banding, but I think I see a lot of former-austenite grain boundry cementite around the cementitegroups.

 

BreedteZaqro2.jpg

BreedteZaqro4.jpg

 

I don't know for sure, but I think that this grainboundrycementite in Zaqro's piece will be more brittle than the 'normal' pearlitic structure in mine.

Also, wouldn't a piece with quite small carbide groups be less brittle than the ones with large groups (and thus large pattern)?

The black dot is a little dirt or something on the lens, it's not part of the structure.

 

 

What do you guys think?

Share this post


Link to post
Share on other sites

the worktemperature was too high, resulting in quite small cementite groups.

 

Really? can you be sure that is the reason, is there a metallurgical explanation? The carbides all look too chunky to me, as if the chrome (or something) is causing them to grow too large. But what magnification are these photos at?

 

I don't know for sure, but I think that this grainboundrycementite in Zaqro's piece will be more brittle than the 'normal' pearlitic structure in mine.

Also, wouldn't a piece with quite small carbide groups be less brittle than the ones with large groups (and thus large pattern)?

That sounds reasonable to me ;)

These photos are great, we should all get reflected light scopes for our wootz! B)

Share this post


Link to post
Share on other sites

the picture should be made at around 650X, the more zoomedpictures are additional 3,5X with the camera optical zoom...

 

Really? can you be sure that is the reason, is there a metallurgical explanation? The carbides all look too chunky to me, as if the chrome (or something) is causing them to grow too large. But what magnification are these photos at?

 

This comment was on my Bulat, there is nothing but Carbon and a little bit of Mn in the steel...

Are the carbides supposed to be smaller?

Share this post


Link to post
Share on other sites

If you look at micrographs of antique blades, for instance fig. 3 in the article “The Key Role of Impurities in Ancient Damascus Steel Blades” by Verhoeven et al. (JOM, 50 (9) (1998), pp. 58-64), you can see that even when closely packed, they stay as separate spheroids (mostly) –these photos are at less magnification than yours, but if you check average carbide size against the band spacing, you’ll see there is a difference in morphology. Significant? Who knows? :huh:

Share this post


Link to post
Share on other sites

Yes, the photo's in the aticle are from high quality antique blades. their spacing is bigger, and their packing in bigger groups. I think the individual cementiteparticles of the Bulat might be equal in size. I am going to try and take a picture with another microscope later on, their I can print a scale onto the image...

Share this post


Link to post
Share on other sites

the picture should be made at around 650X, the more zoomedpictures are additional 3,5X with the camera optical zoom...

 

 

 

This comment was on my Bulat, there is nothing but Carbon and a little bit of Mn in the steel...

Are the carbides supposed to be smaller?

 

Klaas, Jeff,

 

Pleaese correct my math if I am confused.

 

Very interesting pictures...I see a 7 inch disc on my computer screen...converting to micrometers and a 650 magnification that is 270 micro-meters of sample I am looking at...the banding is about 1/5th of that and seems pretty similar to Verhoevens finding of band spacing at about 50 micrometers. Most of the carbide sizes do as well, but this is a very small sample. I have seen photographs of other wootz microstructure which showed a surprising amount of of cementite which had been fractured and showed angular edges.

Your studies of wootz may lead you to document what contributes to some of these variations...I am a bit jealous of your project ( for school credit..wow)...but based on my own experience you better set some clear limits on what the endpoints are...as this can go on forever.

 

Klaas the blades you have posted are quite beautiful ( even though your pattern is faint it is a very nice pattern )

Jan

Share this post


Link to post
Share on other sites

Hey Jan, It's dangerous to make a calculation like that.. The magnification on the Reichert microscope was 65X, the tubus for the photo's was probably 10X, but that is not certain (it is not written on it, and no one knows the exact enlargement of the tubus anymore).

Furthermore, the camera automaticly zooms a little bit to focus.

 

I will post other pics with a scale on them!

 

I have seen photographs of other wootz microstructure which showed a surprising amount of of cementite which had been fractured and showed angular edges.

Is that what they refer to as 'needle-like cementite'?

Do you happen to remember where you saw these pictures?

Thanks!

Edited by Klaas remmen

Share this post


Link to post
Share on other sites

Hey Jan, It's dangerous to make a calculation like that.. The magnification on the Reichert microscope was 65X, the tubus for the photo's was probably 10X, but that is not certain (it is not written on it, and no one knows the exact enlargement of the tubus anymore).

Furthermore, the camera automaticly zooms a little bit to focus.

I will post other pics with a scale on them!

Is that what they refer to as 'needle-like cementite'?

Do you happen to remember where you saw these pictures?

Thanks!

 

Klaas,

It is fun making those estimates and if I am wrong no problem. I have the article somewhere in my "wootz" file and will link it here in a day or two.

 

Jan

Share this post


Link to post
Share on other sites

Klaas,

It is fun making those estimates and if I am wrong no problem. I have the article somewhere in my "wootz" file and will link it here in a day or two.

 

Jan

 

Klaas,

this is the article I was thinking of..there may be others.

 

Jan

Share this post


Link to post
Share on other sites

i alway thought that the long type, drawn out carbides are resulting from the forging..that the direction of flow is making them look this way... and the nice round ball type carbides are made through heat treatments at the end of forging ...

- i remember reading an account of a heat treatment where the blade was coated in clay/dung/alum etc and left in the smoldering coals of a fire for two days... so there was some heat treatments at the end, when sword was finished..... or maybe this is just another observer account to lead us on a wild goose chase :lol:

 

ah if i'm wrong.. it wouldn't be the first time.. hahaha ;)

 

 

Greg

Share this post


Link to post
Share on other sites

Nice article.. And other evidence for the nanowire story.. seems very interesting to me as I read somewhere that these nanowires are 20 times as strong as steel... time to set an endpoint here :blink:^_^

 

The structures in this article are not needle-like cementite, that's for sure. the cementite appears (just like in the bulat) morge elongnated than the spherical cementite in the Verhoeven article.

As I am told, the spheriodising of the cementite occurs due to the cohesive powers of the cementite, just like why water is standing 'conical' on top of a glass. Maybe the elongnated cementite is starting- on it's way to become more spheriodised?

Share this post


Link to post
Share on other sites

Nice article.. And other evidence for the nanowire story.. seems very interesting to me as I read somewhere that these nanowires are 20 times as strong as steel... time to set an endpoint here :blink:^_^

 

The structures in this article are not needle-like cementite, that's for sure. the cementite appears (just like in the bulat) morge elongnated than the spherical cementite in the Verhoeven article.

As I am told, the spheriodising of the cementite occurs due to the cohesive powers of the cementite, just like why water is standing 'conical' on top of a glass. Maybe the elongnated cementite is starting- on it's way to become more spheriodised?

 

Klaas,

I am not familiar with the needle like cementite you are describing...flat plates will look like needles when intersected by polishing a sample.

 

Jan

Share this post


Link to post
Share on other sites

Hi.

 

Just my thought...

 

Sounds like Widmanstätten cementite in side the grain?

But I have seen these only in raw ingots...not in a blade.

 

 

 

 

 

Niko

Share this post


Link to post
Share on other sites

I'll have to look it through. But I think you might be right about the Widmanstatten Niko.

 

here are two more of Zaqro's blades, one was made during the workshop and is rapidly forged, ground and etched. The finished knife is of his earlier work, and a littlebit over-etched.

 

IMG_0477.jpg

DSC02853.jpg

 

I am waiting for pictures of his other work, including swords.

Share this post


Link to post
Share on other sites

I'll have to look it through. But I think you might be right about the Widmanstatten Niko.

here are two more of Zaqro's blades, one was made during the workshop and is rapidly forged, ground and etched. The finished knife is of his earlier work, and a littlebit over-etched.

 

Klaas,

Thank you for posting those, the knife blade is beautiful...I am not sure what is meant by over etching ( I etch deep and like it ). Photographing wootz is tricky and all the pictures I see ( Figiel Excluded...he had to hire two photographers to get it right..I suspect he was doing multiple exposures using different light sources, on film ....maybe moving a light source during a long exposure ) hide the true beauty of this material.

 

One question haunting me is ...out of 800...how many were made into a finished object and how many were part of the learning process?

 

Jan

Share this post


Link to post
Share on other sites

Note that the sword in Jan’s article is the same #10 sword from the Verhoeven paper in JOM.

Just to play devil’s advocate a bit, are you sure that is not ferrite in the bulat photos? Could you see the pattern before you etched the material?

 

Here are a couple photos of needle cementite from Alan William’s recent Ulfberht article in Gladius.

williams 2009 fig4.JPG williams 2009 fig10.JPG

Share this post


Link to post
Share on other sites

Jan, a lot of Zaqro's melts were experiments. He is really into studieing the technology and has several students (at this moment he has seven(!))

He also finished a few hundred knives of them, including some sabres and Kilnjars.

 

Jeff, the fattern was slightly visible as change in light reflection, but I did not check under the microscope. I shall check it next week by polishing it again.

in the photo's with the name (klaas bulat' I can surely see some 'fingerprint' pattern, so surely some pearlite.

 

Can anyone tell me how a hypereutectoïd steel have a ferrite matrix? are the cementitebands depleting the matrix of carbon to form pearlite?

Share this post


Link to post
Share on other sites

as i hinted at earlier... the end heat treatment could be a place to look

 

"Prolonged annealing induces greater ductility at the expense of strength, owing to the tendency of the cementite in the strained pearlite to "ball-up" or spheroidise, as illustrated in Fig. 1c. This is known as "divorced pearlite". The ferrite grains also become larger, particularly if the metal has been cold worked a critical amount. A serious embrittlement sometimes arises after prolonged treatment owing to the formation of cementitic films at the ferrite boundaries. With severe forming operations, cracks are liable to start at these cementite membranes."

 

http://www.keytometals.com/Articles/Art15.htm

 

so this could be the reason less pearlite is shown and more ferrite.... or it maybe very fine pearlite and hard to see

 

 

 

 

 

 

 

Jan, a lot of Zaqro's melts were experiments. He is really into studieing the technology and has several students (at this moment he has seven(!))

He also finished a few hundred knives of them, including some sabres and Kilnjars.

 

Jeff, the fattern was slightly visible as change in light reflection, but I did not check under the microscope. I shall check it next week by polishing it again.

in the photo's with the name (klaas bulat' I can surely see some 'fingerprint' pattern, so surely some pearlite.

 

Can anyone tell me how a hypereutectoïd steel have a ferrite matrix? are the cementitebands depleting the matrix of carbon to form pearlite?

Share this post


Link to post
Share on other sites

I think if hypereutectoid you can only have pearlite matrix, no? hyper gives you cementite/pearlite banding, hypoeutectiod you get ferrite/pearlite....

Share this post


Link to post
Share on other sites

Thanks Greg and Jeff. If I understend correctly Greg, The elongnated pearlite can split up in globular cementite and ferrite grains? But the cementite balls would have to dissolve again and settle in line (at segregated impurity's as Verhoeven discribes)?

 

I got some new pics from Zaqro's work which I would like to share with you. This is an example of the 'Konasamudram' process. Usualy gives relatively big hockey-puck shaped ingots, which, according to Zaqro, were flattened further, and then cut into a spiral and stretched out.

 

The ingot was 480g, the finished Yataghan weighs 260 grams.

The pattern is nice but not clearly to see on this pics. I am waiting for better pictures.

Enjoy!

 

got4.jpg

 

Got2.jpg

 

Got3.jpg

 

got1.jpg

 

got5.jpg

Share this post


Link to post
Share on other sites

Now that's not a crucible shape you see every day. Given the amount of bubbling at the surface, I'm a little surprised it could hold a molten charge.

 

Does anyone have a blade type they prefer for cutting these ingots? Have bandsaw, will travel...

Share this post


Link to post
Share on other sites

Does anyone have a blade type they prefer for cutting these ingots? Have bandsaw, will travel...

That's easy. It is called a "cutoff disk". Personally I prefer DeWalt 1/16" thick. :rolleyes:

Share this post


Link to post
Share on other sites

Hey, never tried a shizzle? :ph34r: Maybe too hard?

Edited by Klaas remmen

Share this post


Link to post
Share on other sites

I meant to spiral-cut one. Unless you're suggesting a short cut, then forge out the tab, the short cut again, then forge straight...

 

I was thinking to bandsaw it cinnabon style.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...