Why were the ingots mostly round?

galvano · 9th April 2006, 10:57 PM

Here two ingots.
One with bubbles.
One with cracks. galvano.

Rivkin · 10th April 2006, 01:05 AM

I don't really know metallurgy, so a stupid question: what if one "on purpose" adds some localized impurity - can it be a seed for the pattern to grow, i.e. the pattern will nicely grow from this point?

Like, for example in the sample above it seems that the pattern "grows" from the sample's surface and is much sparser in the sample's middle; it also nearly absent on the sample's bottom. Could one add something to the sample so it will be an artificial centre of the pattern's growth.

Jeff Pringle · 10th April 2006, 01:38 AM

I think the pattern difference above is a lighting artifact, with different lighting the pattern should look uniform across the surface.
Patterns in wootz come from the fact that when the steel starts to solidify, the first crystals 'want' to be pure iron/carbon - the impurities in the melt become concentrated in the areas of secondary crystalization, in between the networks of already solid metal. So the impurites do get localized to a degree.
Theoretically, you can control the grain orientation, and hence ultimate pattern, by manipulating the shape of the solidifying metal (by casting into a mold of varying thickness), but I don't think anyone is working on this yet.

galvano · 10th April 2006, 07:34 PM

it is not a artéfact.
Surface was attacked with ferric chloride.
galvano

Rivkin · 10th April 2006, 08:05 PM

Quote:

Originally Posted by Jeff Pringle

I think the pattern difference above is a lighting artifact, with different lighting the pattern should look uniform across the surface.
Patterns in wootz come from the fact that when the steel starts to solidify, the first crystals 'want' to be pure iron/carbon - the impurities in the melt become concentrated in the areas of secondary crystalization, in between the networks of already solid metal. So the impurites do get localized to a degree.
Theoretically, you can control the grain orientation, and hence ultimate pattern, by manipulating the shape of the solidifying metal (by casting into a mold of varying thickness), but I don't think anyone is working on this yet.

Pattern's orientation is going to depend on the sample's size/shape if it is comparable to the grain's thickness, however imho since the interaction between particles here is a short range, the thickness of grains mostly going to depend on chemical composition of the sample.
What I was thinking is that if one locally introduces an impurity, preferrably such that an energy bonding to the pattern if favorable over bonding to the matrix, one can probably create really nice patterns, not very practical, but very nice indeed.

Jens Nordlunde · 10th April 2006, 10:35 PM

Jeff/Galvano, thank you for showing the ingots, I think they illustrate what you are describing.

Not all the iron ores could be used for ingots, and the Indians knew it. Some ores could only be used for tools while others could be used for weapons and ingots, maybe that is why some of the Arabian merchants had their own people stationed in India to check the ingots before they were exported. If I have understood you correctly, they could however not check if the ingots had ‘bubbles’ inside, and maybe not all cracks could be seen – or could they?

Jeff Pringle · 11th April 2006, 02:40 AM

If an ingot has a bad bubble problem, it usually is visible on the outside. Occasional small bubbles are easy to work around, so even if they can't be seen they are not a problem. Cracks that mean an ingot is no good usually show up right away, and in descriptions of historical ingot testing that I've read, that's the first thing they checked - how they responded to the first few hammer blows.
The ingot pictured above started cracking (in an ominous fashion) right away, but I kept at it to see if I could coax some useable metal out of it - no such luck!

Jens Nordlunde · 11th April 2006, 02:55 PM

Jeff, it is interesting what you write about the ingots. I have never, although it may sound strange, had an ingot in my hand. When I started to collect many years ago, there were not many for sale – but that has improved a lot in the last years, like discussed on another thread. I should have remembered the sound test, which can be used on metal, glass, porcelain and probably on many other things.

You write, “Occasional small bubbles are easy to work around, so even if they can't be seen they are not a problem.” Does this, ‘work around’ mean, that you cut the bubbles out when you have flattened the ingot? Or how do you ‘work around the problem’?

9th April 2006, 10:57 PM	#1
galvano Member Join Date: Jan 2006 Posts: 178	ingots Here two ingots. One with bubbles. One with cracks. galvano. Attached Images

10th April 2006, 07:34 PM	#4
galvano Member Join Date: Jan 2006 Posts: 178	jeff pringle it is not a artéfact. Surface was attacked with ferric chloride. galvano

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10th April 2006, 01:05 AM	#2
Rivkin Member Join Date: Dec 2004 Posts: 655	I don't really know metallurgy, so a stupid question: what if one "on purpose" adds some localized impurity - can it be a seed for the pattern to grow, i.e. the pattern will nicely grow from this point? Like, for example in the sample above it seems that the pattern "grows" from the sample's surface and is much sparser in the sample's middle; it also nearly absent on the sample's bottom. Could one add something to the sample so it will be an artificial centre of the pattern's growth.

10th April 2006, 01:38 AM	#3
Jeff Pringle Member Join Date: Nov 2005 Posts: 189	I think the pattern difference above is a lighting artifact, with different lighting the pattern should look uniform across the surface. Patterns in wootz come from the fact that when the steel starts to solidify, the first crystals 'want' to be pure iron/carbon - the impurities in the melt become concentrated in the areas of secondary crystalization, in between the networks of already solid metal. So the impurites do get localized to a degree. Theoretically, you can control the grain orientation, and hence ultimate pattern, by manipulating the shape of the solidifying metal (by casting into a mold of varying thickness), but I don't think anyone is working on this yet.

10th April 2006, 10:35 PM	#6
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Jeff/Galvano, thank you for showing the ingots, I think they illustrate what you are describing. Not all the iron ores could be used for ingots, and the Indians knew it. Some ores could only be used for tools while others could be used for weapons and ingots, maybe that is why some of the Arabian merchants had their own people stationed in India to check the ingots before they were exported. If I have understood you correctly, they could however not check if the ingots had ‘bubbles’ inside, and maybe not all cracks could be seen – or could they?

11th April 2006, 02:40 AM	#7
Jeff Pringle Member Join Date: Nov 2005 Posts: 189	If an ingot has a bad bubble problem, it usually is visible on the outside. Occasional small bubbles are easy to work around, so even if they can't be seen they are not a problem. Cracks that mean an ingot is no good usually show up right away, and in descriptions of historical ingot testing that I've read, that's the first thing they checked - how they responded to the first few hammer blows. The ingot pictured above started cracking (in an ominous fashion) right away, but I kept at it to see if I could coax some useable metal out of it - no such luck!

11th April 2006, 02:55 PM	#8
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Jeff, it is interesting what you write about the ingots. I have never, although it may sound strange, had an ingot in my hand. When I started to collect many years ago, there were not many for sale – but that has improved a lot in the last years, like discussed on another thread. I should have remembered the sound test, which can be used on metal, glass, porcelain and probably on many other things. You write, “Occasional small bubbles are easy to work around, so even if they can't be seen they are not a problem.” Does this, ‘work around’ mean, that you cut the bubbles out when you have flattened the ingot? Or how do you ‘work around the problem’?