How wootz blades were forged?

Bob A · 21st September 2019, 06:10 PM

I thought this information on production of silicon carbide was of interest.

The simplest process to manufacture silicon carbide is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F). Fine SiO2 particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material.*

Sand would obviously melt into a glass at the temperatures involved in the wootz process.

In light of above posts, I may be merely belaboring the obvious here. Nonetheless, the reference to plant material in the Wikipedia entry discussing silicon carbide was interesting.

*https://en.wikipedia.org/wiki/Silicon_carbide

Richard Furrer · 21st September 2019, 09:42 PM

Ariel, No need to notch the ingot...it folds at the top on its own during forging...for two reasons. One being that unless high forces are delivered it is the natural tendency for metals to move more at the surface that the middle and they "fish mouth" or "duck bill". After more light forging the edges of the steel touch and you get a folded appearance. The second is that the poorest part of the ingot is the top and it almost always had gas pockets from the cooling process and as such is less dense and moves differently under the hammer. Often collapsing onto its center as forging progresses.

I have yet to see a "sound surface" at the top of an ingot. All ingots have some surface irregularities in them in the form of pockets or bulges and if the porosity is not visible it exists in micro form with the most porous at the top.

Often the top of the ingot becomes the spine of the blade. I would call the folded over bit a seam and I have seen several where the seam wanders from the spine onto the flat of the blade. In one case it fell off and was cold riveted back into place.

Ariel...if that broken blade is for sale I would like to purchase it and do chemical, hardness and microscopic analysis on it to add to my database.
That goes for anyone else who has broken crucible steel blades or bits and pieces.

Edit: It is a simple matter to add silicon to the steel when it is liquid (very hard to stop if glass is present actually) and I have yet to see any glass survive in the bar once forged out to a blade. It all goes away when the ingot is being forged into bars. This is due to its liquid nature at temperatures used for forging and also that if allowed to cool on the anvil it is untempered glass which is very brittle and simply falls away when left to its own devices after a day of forging.

Edit Edit: I would guess that large grain size (and shipping abuse) was the cause of the fracture. If the break is at all black on the edges then it could also have been a flaw from the quench which waited for the stress of shipping to finally break. Cracks caused in forging or the quench or almost always black color due to high temperature oxidation. In modern blades if the crack is yellow or blue then the crack was in the tempering stage of manufacture...the color is again due to oxides, but lower temperature oxidation.

Ric

ariel · 22nd September 2019, 04:04 AM

Richard,
What sale are you talking about? :-)
Send me your address and you will get it for free. I shall only be delighted to contribute something useful to the community of wootz-smiths.
One condition: after you polish and etch the break, could you send me a pic of it, please?
And if something interesting comes up from the measurement you will be taking, please let me know. OK?

Ariel

Ian · 22nd September 2019, 06:24 AM

Ric and Ariel:

Please post the results here also.

Ian

Richard Furrer · 22nd September 2019, 05:33 PM

Absolutely Ariel, The Professors I work with have just added some new analytical tools and we can do better testing now than in the past.
I will tell you what we discover.

Let me know everything you can about the sword so we can include that in the data as well.

Ric

Bryce · 22nd September 2019, 08:41 PM

Thanks for posting your cloudy/silver lining breakage and your great explanation Ariel. Is their a wootz pattern visible on the face of the blade? Can you post a photo?
Cheers,
Bryce

ariel · 23rd September 2019, 02:31 AM

I can see islets of wootz pattern, and tried to photograph them with my iPad, but the camera was not able to catch the image: there is quite a lot of small pitting.
It has to be polished and then etched professionally (I am an amateur). I am sure Ric will be able to do it zillion times better when he gets it.

Of course, after he sends me his mailing address:-)

21st September 2019, 06:10 PM	#1
Bob A Member Join Date: Feb 2014 Posts: 435	I thought this information on production of silicon carbide was of interest. The simplest process to manufacture silicon carbide is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F). Fine SiO2 particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material.* Sand would obviously melt into a glass at the temperatures involved in the wootz process. In light of above posts, I may be merely belaboring the obvious here. Nonetheless, the reference to plant material in the Wikipedia entry discussing silicon carbide was interesting. *https://en.wikipedia.org/wiki/Silicon_carbide

21st September 2019, 09:42 PM	#2
Richard Furrer Member Join Date: Mar 2006 Location: Sturgeon Bay, Wisconsin Posts: 163	Ariel, No need to notch the ingot...it folds at the top on its own during forging...for two reasons. One being that unless high forces are delivered it is the natural tendency for metals to move more at the surface that the middle and they "fish mouth" or "duck bill". After more light forging the edges of the steel touch and you get a folded appearance. The second is that the poorest part of the ingot is the top and it almost always had gas pockets from the cooling process and as such is less dense and moves differently under the hammer. Often collapsing onto its center as forging progresses. I have yet to see a "sound surface" at the top of an ingot. All ingots have some surface irregularities in them in the form of pockets or bulges and if the porosity is not visible it exists in micro form with the most porous at the top. Often the top of the ingot becomes the spine of the blade. I would call the folded over bit a seam and I have seen several where the seam wanders from the spine onto the flat of the blade. In one case it fell off and was cold riveted back into place. Ariel...if that broken blade is for sale I would like to purchase it and do chemical, hardness and microscopic analysis on it to add to my database. That goes for anyone else who has broken crucible steel blades or bits and pieces. Edit: It is a simple matter to add silicon to the steel when it is liquid (very hard to stop if glass is present actually) and I have yet to see any glass survive in the bar once forged out to a blade. It all goes away when the ingot is being forged into bars. This is due to its liquid nature at temperatures used for forging and also that if allowed to cool on the anvil it is untempered glass which is very brittle and simply falls away when left to its own devices after a day of forging. Edit Edit: I would guess that large grain size (and shipping abuse) was the cause of the fracture. If the break is at all black on the edges then it could also have been a flaw from the quench which waited for the stress of shipping to finally break. Cracks caused in forging or the quench or almost always black color due to high temperature oxidation. In modern blades if the crack is yellow or blue then the crack was in the tempering stage of manufacture...the color is again due to oxides, but lower temperature oxidation. Ric

22nd September 2019, 04:04 AM	#3
ariel Member Join Date: Dec 2004 Location: Ann Arbor, MI Posts: 5,503	Richard, What sale are you talking about? :-) Send me your address and you will get it for free. I shall only be delighted to contribute something useful to the community of wootz-smiths. One condition: after you polish and etch the break, could you send me a pic of it, please? And if something interesting comes up from the measurement you will be taking, please let me know. OK? Ariel

22nd September 2019, 06:24 AM	#4
Ian Vikingsword Staff Join Date: Dec 2004 Location: The Aussie Bush Posts: 4,361	Ric and Ariel: Please post the results here also. Ian

22nd September 2019, 05:33 PM	#5
Richard Furrer Member Join Date: Mar 2006 Location: Sturgeon Bay, Wisconsin Posts: 163	Absolutely Ariel, The Professors I work with have just added some new analytical tools and we can do better testing now than in the past. I will tell you what we discover. Let me know everything you can about the sword so we can include that in the data as well. Ric

22nd September 2019, 08:41 PM	#6
Bryce Member Join Date: Aug 2017 Location: North Queensland, Australia Posts: 187	Thanks for posting your cloudy/silver lining breakage and your great explanation Ariel. Is their a wootz pattern visible on the face of the blade? Can you post a photo? Cheers, Bryce

23rd September 2019, 02:31 AM	#7
ariel Member Join Date: Dec 2004 Location: Ann Arbor, MI Posts: 5,503	I can see islets of wootz pattern, and tried to photograph them with my iPad, but the camera was not able to catch the image: there is quite a lot of small pitting. It has to be polished and then etched professionally (I am an amateur). I am sure Ric will be able to do it zillion times better when he gets it. Of course, after he sends me his mailing address:-)