Why were the ingots mostly round?

Jeff Pringle · 4th April 2006, 06:50 PM

No, not slag - sometimes there are 'air' bubbles that need to be worked around, sometimes cracks appear. Typically slag inclusions in wootz are fairly minor.

Jens Nordlunde · 4th April 2006, 10:30 PM

I am rather puzzled. ‘Air’ bubbles, what is that, and how do you work your way around them? It is the first time I have ever heard about it.
The cracks are something interesting. I know of course that they appeared; most of the collectors know this, but why? One would think that when a blade is heated and worked on cracks would disappear, that the forging would make the blade more homogeneous, so why are the cracks still there?

Justin · 4th April 2006, 11:37 PM

Thanks,Jeff.

PUFF · 5th April 2006, 04:40 AM

Unlike solid state smelting, the wootz smelting turn whole thing to liquid mixture. With slow cooling, liq. slag and liq. metal separated into two distintive phases like water and oil. Most of impurities partitioned into slag phase and floated up to the surface. I don't know about air bubble. Any bubble in the ingot indicates that smelting temperature 's too low and such a low smelting temp could trap some slag either.

Cracks are not "as baked" flaw. They happened when forging stress goes beyond the material elasticity (either forging temp 's too low or hammering 's too hard). Dear Jens, forging would make the blade more homogeneous as slag inclusions were forged out. But flaws like crack (or bubble) could not be closed unless you reach forge welding temperature (~1400 C). Unfortunately, wootz pattern melt down at 900-1000 C and forge welding of cracks or two ingots 's unlikely (possible but very difficult to bring the pattern black

).

Any flaw appear during forging stage can be easily work around by either trimming out or shortening the piece. IMO,As a smith, the worst flaw 's quench crack

Jens Nordlunde · 5th April 2006, 10:17 PM

Hi Puff, thank you for the explanation, I had an idea that it may be like you described, but I was not sure. Also I knew about the heat, but it is better to hear it one more time. Also there may still be some of the forumites who have not heard about this before.
So I suppose that the temperature of 900-100C is the cherry colour Hendley writes about.
Nice to have people like Greg, Jeff and you onboard, when it comes to the construction of our collectives.

PUFF · 6th April 2006, 01:40 PM

Quote:

Originally Posted by Jens Nordlunde

Hi Puff, thank you for the explanation, I had an idea that it may be like you described, but I was not sure. Also I knew about the heat, but it is better to hear it one more time. Also there may still be some of the forumites who have not heard about this before.
So I suppose that the temperature of 900-100C is the cherry colour Hendley writes about.
Nice to have people like Greg, Jeff and you onboard, when it comes to the construction of our collectives.

Just a minor correction, 900-1000 C going to be a yellowish cherry, a bit sour for my taste. Nice sweet & sour cherry red 's around 800 C.

Jeff Pringle · 9th April 2006, 06:27 PM

To add a bit to what Puff said, regarding bubbles:
I said 'air', but really it's carbon monoxide or oxygen, and they occur for a variety of reasons - undercooked ingots mostly (the melt has not reached equilibrium), but since liquid steel can hold more gasses in solution than solid steel, you can find porosity occuring during solidification too.
Regarding cracking, it can occur from working at too high or too low a temperature, or pushing the material too fast - the as-solidified grain stucture needs to be coaxed into a finer, more forgeable state. Impurities in the steel (oxygen, sulfur, phosphorus etc.) will precipitate out at grain boundaries during solidification, and can cause cracking too.
Forging temps for wootz are not high enough for cracks to get welded back together, so they don't go away. As Puff said, "Any flaw appear during forging stage can be easily work around by either trimming out or shortening the piece", and that's how those one-sword ingots get to be multiple-knife ingots.

I have some ingot slices that demonstrate most of the flaws you can run across, here's one ingot with some probable CO bubbles - cube is 1 cm for scale:

This ingot also suffered from too much intergranular oxygen and proved to be unworkable, after a lot of work!

5th April 2006, 10:17 PM	#5
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Hi Puff, thank you for the explanation, I had an idea that it may be like you described, but I was not sure. Also I knew about the heat, but it is better to hear it one more time. Also there may still be some of the forumites who have not heard about this before. So I suppose that the temperature of 900-100C is the cherry colour Hendley writes about. Nice to have people like Greg, Jeff and you onboard, when it comes to the construction of our collectives. Last edited by Jens Nordlunde; 5th April 2006 at 10:35 PM.

4th April 2006, 06:50 PM	#1
Jeff Pringle Member Join Date: Nov 2005 Posts: 189	No, not slag - sometimes there are 'air' bubbles that need to be worked around, sometimes cracks appear. Typically slag inclusions in wootz are fairly minor.

4th April 2006, 10:30 PM	#2
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	I am rather puzzled. ‘Air’ bubbles, what is that, and how do you work your way around them? It is the first time I have ever heard about it. The cracks are something interesting. I know of course that they appeared; most of the collectors know this, but why? One would think that when a blade is heated and worked on cracks would disappear, that the forging would make the blade more homogeneous, so why are the cracks still there?

4th April 2006, 11:37 PM	#3
Justin Member Join Date: Dec 2004 Posts: 182	Thanks,Jeff.

5th April 2006, 04:40 AM	#4
PUFF Member Join Date: Feb 2006 Location: 30 miles north of Bangkok, 20 miles south of Ayuthaya, Thailand Posts: 224	Unlike solid state smelting, the wootz smelting turn whole thing to liquid mixture. With slow cooling, liq. slag and liq. metal separated into two distintive phases like water and oil. Most of impurities partitioned into slag phase and floated up to the surface. I don't know about air bubble. Any bubble in the ingot indicates that smelting temperature 's too low and such a low smelting temp could trap some slag either. Cracks are not "as baked" flaw. They happened when forging stress goes beyond the material elasticity (either forging temp 's too low or hammering 's too hard). Dear Jens, forging would make the blade more homogeneous as slag inclusions were forged out. But flaws like crack (or bubble) could not be closed unless you reach forge welding temperature (~1400 C). Unfortunately, wootz pattern melt down at 900-1000 C and forge welding of cracks or two ingots 's unlikely (possible but very difficult to bring the pattern black ). Any flaw appear during forging stage can be easily work around by either trimming out or shortening the piece. IMO,As a smith, the worst flaw 's quench crack

9th April 2006, 06:27 PM	#7
Jeff Pringle Member Join Date: Nov 2005 Posts: 189	To add a bit to what Puff said, regarding bubbles: I said 'air', but really it's carbon monoxide or oxygen, and they occur for a variety of reasons - undercooked ingots mostly (the melt has not reached equilibrium), but since liquid steel can hold more gasses in solution than solid steel, you can find porosity occuring during solidification too. Regarding cracking, it can occur from working at too high or too low a temperature, or pushing the material too fast - the as-solidified grain stucture needs to be coaxed into a finer, more forgeable state. Impurities in the steel (oxygen, sulfur, phosphorus etc.) will precipitate out at grain boundaries during solidification, and can cause cracking too. Forging temps for wootz are not high enough for cracks to get welded back together, so they don't go away. As Puff said, "Any flaw appear during forging stage can be easily work around by either trimming out or shortening the piece", and that's how those one-sword ingots get to be multiple-knife ingots. I have some ingot slices that demonstrate most of the flaws you can run across, here's one ingot with some probable CO bubbles - cube is 1 cm for scale: This ingot also suffered from too much intergranular oxygen and proved to be unworkable, after a lot of work!