Why were the ingots mostly round?

Jeff Pringle · 4th April 2006, 05:32 AM

I'm thinking that it's easier to get a crucible to maintain it's structural integrity at high heat if it is round, and not too tall.
Also, the difficulty in forging out the metal is a problem with all ingots, the first stages are the difficult ones and would exist with either round or long ones, so the benefit is not as great as it would seem.
Round, compact ingots also might be less prone to casting flaws, bubbles and/or slag inclusions, due to the surface area to mass ratio - it really sucks when you spend a bunch of hours forging something out and then find a flaw.
What do you think?

PUFF · 4th April 2006, 10:37 AM

I had tried a couple wootz smelting with no success. And what I can tell you is that button shape crucible 's much more easy to work with.

First of all, oxygen protection is a must for wootz smelting. In wootz furnace, the crucibles are required to be arranged at the combustion zone (highest heat, ~1400 C). Since atmospheric condition 's not totally reduction, molten steel surface need to be protected and minimized.

The second reason is for the crucible 's stability, as Jeff mentioned. Even modern refractory get soften a bit at that temperature. Wootz crucibles are need to be heated at 1200-1300 C for several hours. Good design 's required or crucibles will be fail (very messy, 'liv me).

Third reason 's also ceramic thing. The fact that the higher refractory materials has lower plasticity and green strength 's another major constrain for their shape. You cannot make a very complex shape. And cup-shape crucible 's difficult enough for hand-forming pieces.

The forth reason; dendritic steel 's VERY difficult to forge down, especially when heat 's required to be under 800 C. Even with annealed button, smiths may require 30-40 reds (heat cycles) to forge button flat. That 'coz of dendritic structure 's required to be broken into small. And after the button has been "forge soften", only another 10-20 reds to go to bar or other shape. If the metal was made as bar, 50+ heat cycles still need for shaping.

The metal cannot be cast to shape 'coz the "as cast" material 's too brittle for any application.

Jens Nordlunde · 4th April 2006, 01:18 PM

Hi all, sorry for my absence.

Thank you for the answers witch I find very interesting. As the one who knows little about the subject, I have an additional question.

From the answers you have written I understand, that the bigger the ingots were the more difficult it was to make them. As far as I know the ingots varied in size from a few hundred grams to about 3 kg, but most were made for making two sword blades out of an ingot. If the big ingots were so difficult to make, why did they not make the small ones only? Is it possible to forge left over from two different ingots together and get a good result? How close it the wooz pattern in the ingots made in the same furnace?

Jeff Pringle · 4th April 2006, 04:19 PM

Quote:

If the big ingots were so difficult to make, why did they not make the small ones only?

Taken as an entire process, I don't think there is a huge difference in difficulty between big and small ingots, and there are considerations such as efficiency of the furnace, and success rate of the final product.
Plus, as anyone who is making the stuff can tell you, many of the 'two-sword' ingots get to be 'one sword'- or 'several knife'-sized by the end of the forging process - if you only made ingots big enough for a sword, you'd end up with a lot of knives, and maybe not enough swords!

Quote:

Is it possible to forge left over from two different ingots together and get a good result?

They did it back in the day, I don't know if anyone has gotten the technique down in modern times.

Quote:

How close it the wooz pattern in the ingots made in the same furnace?

Very different, even within the same batch or ingot. I think Ric Furrer did a test of a Sri Lankan(?) type of crucible that was designed to be laid on it's side when the metal was molten, to give an oblong bar - IIRC, two ingots made of the same metal fired at the same time gave very different patterns in the final surface.
I find a fair degree of uniformity in patterns within an ingot, but each ingot varies in pattern depending mainly on carbon content and solidification rate.

Justin - this article explains the patterning in wootz steel -
http://www.tms.org/pubs/journals/JOM...even-9809.html

Jens Nordlunde · 4th April 2006, 05:08 PM

Hi Jeff, thank you for your interesting answer.
Since you write that a ‘two sword’ ingot easily could end up as a few daggers ingot, there must be a big difference of how much slag there it in the different ingots?

Jeff Pringle · 4th April 2006, 05:50 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, 09:30 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?

4th April 2006, 01:18 PM	#3
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Hi all, sorry for my absence. Thank you for the answers witch I find very interesting. As the one who knows little about the subject, I have an additional question. From the answers you have written I understand, that the bigger the ingots were the more difficult it was to make them. As far as I know the ingots varied in size from a few hundred grams to about 3 kg, but most were made for making two sword blades out of an ingot. If the big ingots were so difficult to make, why did they not make the small ones only? Is it possible to forge left over from two different ingots together and get a good result? How close it the wooz pattern in the ingots made in the same furnace? Last edited by Jens Nordlunde; 4th April 2006 at 02:36 PM.

4th April 2006, 05:32 AM	#1
Jeff Pringle Member Join Date: Nov 2005 Posts: 189	I'm thinking that it's easier to get a crucible to maintain it's structural integrity at high heat if it is round, and not too tall. Also, the difficulty in forging out the metal is a problem with all ingots, the first stages are the difficult ones and would exist with either round or long ones, so the benefit is not as great as it would seem. Round, compact ingots also might be less prone to casting flaws, bubbles and/or slag inclusions, due to the surface area to mass ratio - it really sucks when you spend a bunch of hours forging something out and then find a flaw. What do you think?

4th April 2006, 10:37 AM	#2
PUFF Member Join Date: Feb 2006 Location: 30 miles north of Bangkok, 20 miles south of Ayuthaya, Thailand Posts: 224	I had tried a couple wootz smelting with no success. And what I can tell you is that button shape crucible 's much more easy to work with. First of all, oxygen protection is a must for wootz smelting. In wootz furnace, the crucibles are required to be arranged at the combustion zone (highest heat, ~1400 C). Since atmospheric condition 's not totally reduction, molten steel surface need to be protected and minimized. The second reason is for the crucible 's stability, as Jeff mentioned. Even modern refractory get soften a bit at that temperature. Wootz crucibles are need to be heated at 1200-1300 C for several hours. Good design 's required or crucibles will be fail (very messy, 'liv me). Third reason 's also ceramic thing. The fact that the higher refractory materials has lower plasticity and green strength 's another major constrain for their shape. You cannot make a very complex shape. And cup-shape crucible 's difficult enough for hand-forming pieces. The forth reason; dendritic steel 's VERY difficult to forge down, especially when heat 's required to be under 800 C. Even with annealed button, smiths may require 30-40 reds (heat cycles) to forge button flat. That 'coz of dendritic structure 's required to be broken into small. And after the button has been "forge soften", only another 10-20 reds to go to bar or other shape. If the metal was made as bar, 50+ heat cycles still need for shaping. The metal cannot be cast to shape 'coz the "as cast" material 's too brittle for any application.

4th April 2006, 05:08 PM	#5
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Hi Jeff, thank you for your interesting answer. Since you write that a ‘two sword’ ingot easily could end up as a few daggers ingot, there must be a big difference of how much slag there it in the different ingots?

4th April 2006, 05:50 PM	#6
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, 09:30 PM	#7
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?