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Wootz Furnace - Questions....

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Well it's this time of the year again, when winter should have died half a decade ago and lil' birds should be singing...

But it's still to cold.

Well... that makes it the ideal tool-building time for me... as I'm not too keen on getting out of the shop ;)

 

Shitty weather aside: This is something I've been pondering for a long while....

I'd like to get something like a "production" wootz-making furnace.

 

I've made wootz like three times (one time not that successful, the other too quite ok - but really just minor quantities for experimental purposes.)

So I've got a slight bit of an idea on how the process works - but of course I'll need more experience.

 

But I'd like to build a permanent furnace to make wootz.

 

I'll be using graphite crucibles... those are easy to get.

 

But what on the furnace...

 

Would you go with Gas? Oil? Electricity?

How about a controller?

What type of materials?

 

My idea / wish is a furnace large enough to make about 4-10 kg of Wootz with each run.

As the process is quite time consuming - I'd like to make enough of it for at least a couple of blades with one run.

 

Also the other thing is: the furnace should be able to last for a long time.

 

As most know I've successfully built several kilns, forges, etc. over the past 15 or so years.

So the question is not about "how do I make a furnace"... but rather specifically on one that works well for the wootz on a long run.

 

Any inout welcome!

 

thanks.

 

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Well it's this time of the year again, when winter should have died half a decade ago and lil' birds should be singing...

But it's still to cold.

Well... that makes it the ideal tool-building time for me... as I'm not too keen on getting out of the shop ;)

 

Shitty weather aside: This is something I've been pondering for a long while....

I'd like to get something like a "production" wootz-making furnace.

 

I've made wootz like three times (one time not that successful, the other too quite ok - but really just minor quantities for experimental purposes.)

So I've got a slight bit of an idea on how the process works - but of course I'll need more experience.

 

But I'd like to build a permanent furnace to make wootz.

 

I'll be using graphite crucibles... those are easy to get.

 

But what on the furnace...

 

Would you go with Gas? Oil? Electricity?

How about a controller?

What type of materials?

 

My idea / wish is a furnace large enough to make about 4-10 kg of Wootz with each run.

As the process is quite time consuming - I'd like to make enough of it for at least a couple of blades with one run.

 

Also the other thing is: the furnace should be able to last for a long time.

 

As most know I've successfully built several kilns, forges, etc. over the past 15 or so years.

So the question is not about "how do I make a furnace"... but rather specifically on one that works well for the wootz on a long run.

 

Any inout welcome!

 

thanks.

I'm realize you mean clay-graphite crucibles, but you may want to consider making single use crucibles if you don't want to risk breaking an expensive one when your experimenting. Dmitry Malakhov from art and knives uses this recipe which uses mullite if you want to have a go. http://www.artandknife.com/crucible.html

 

Everyone I've heard uses gas furnaces for wootz, most with a layer of High temp kaowool then refractory cement. Oil furnaces are possible, but are difficult to make at wrought iron melting temps, and they're mainly used for cast iron. However for 4-10 kg of wootz per run I don't know if you could make a gas one big enough without needing like five gas tanks at a time!

 

I've always wanted to build a charcoal furnace for making crucible steel, like Ric does in his Ulfberht vid, and you're more likely to get the capacity per run, but it will need a lot of charcoal, cost quite a lot and then the majority of the furnace will only last a couple of runs before needing serious maintenance.

 

You have much more experience building kilns than I do (without a doubt since I've only made 2 small ones) so I don't know if it's possible to build such a big gas furnace without spending a fortune, but gas is definitely the most practical option here.

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Tristan

 

Thank you for your reply.

 

I hadn't thought about the possibility to make my own crucibles...

I'll have to look into that and the availability of the materials locally...

I've got a good source for the graphite crucibles though - prices are "moderate" (not cheap)... and have had good results with those so far...

But of course, they break - and if I could make my own it would be even better.

 

Charcoal / coke / etc. is completely out of the question. I would need to install a completely different vent-system to the current shop and charcoal in such quantities is far more expensive than anything else I could use.

Also I'd like to go with something I can rig a controller to easily - so I can get a more controlled, repeatable process.

 

Personally I think I'll go with a Multi-Burner LPG Setup with forced Air maybe even compressed air (high pressure injection / mixing burner) as they're used in large industrial waste-combustion facilities.

 

The burners & reaching the req. temperatures aren't my concern - I've built plenty different burners over the years that were able to deliver these temps.

 

The "problem" I have at the moment is mostly about effective & lasting insulation of the thing.

 

I'm in contact with a german company who supplies fibre insulation (vakuum formed fibre boards) up to 1800°C (3270°F)... but I have not yet seen the actual technical specs... so I don't know how well they'll hold up at about 1500-1600°C over longer periods of time.

 

Also the other thing I'm not yet happy with is how I support the crucible inside the furnace at those temps.

Something that's rigid enough to hold the weight (4-10kg + crucible) at those temps...

here most of the ideas I have will not work upon closer examination and experimentation.

 

The most practical solution so far is a composite build like this:

Outer Shell from 2-4mm stainless sheet, Octagonal shape

Inner insulation, outer-level from Ceramic fibre board to 1500°C about 2" thick

Inside stable Insulation from Hight Temp Bricks (1800°C) with an included support for the crucible made from the same brick.

 

Burner from Stainless Steel & Ceramic nozzles

four Burners, Side mounted, with a 40° upwards tilt.

Pointing at the lower third of the crucible

 

Lid for the furnace made from stainless steel & 1800°C Fibre board.

 

The whole furnace housing & lid can be raised, leaving just the base & crucible & burners "exposed" for easy removal & repairs.

 

 

But again, most stones at those temps become quite "brittle" .... crack easy and don't handle weight that well...

if the mass of the holder is large enough to supprt the crucible it's going to be a huge temperature "draw"...

 

 

the other idea is electric:

... Advantage: less risk & easy to maintain. & easy to control

I can get pre-assembled blocks of insulative material & heating wire (pre-mounted to the block) - ready to assemble for temperatures up to 1650°C...

however the cost of those parts is a bit "prohibitive".

 

it's going to be a huge power-sucker though.

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take a look here, #18 there are two pics worth looking at.

http://www.messerforum.net/showthread.php?84422-Gasesse-zum-Schmelzen

 

or here: http://www.fursa-family.net/main/Vasilij_Fursa_files/Vasilij-Fursa/Wootz_files/bulat.html

he uses coal or coke for the fire

 

http://www.fursa-family.net/main/Vasilij_Fursa_files/Vasilij-Fursa/Wootz_files/crucible.html

 

mit welcher Firma stehst denn in Kontakt?

 

LG

Jokke

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take a look here, #18 there are two pics worth looking at.

http://www.messerforum.net/showthread.php?84422-Gasesse-zum-Schmelzen

 

or here: http://www.fursa-family.net/main/Vasilij_Fursa_files/Vasilij-Fursa/Wootz_files/bulat.html

he uses coal or coke for the fire

 

http://www.fursa-family.net/main/Vasilij_Fursa_files/Vasilij-Fursa/Wootz_files/crucible.html

 

mit welcher Firma stehst denn in Kontakt?

 

LG

Jokke

Danke dir Jokke,

für die Links...

(thanks Jokke for the links...)

 

Die Firma (inzw. sinds zwei):

http://berghuetten-gmbh.de/

und http://www.hightech-ceram.de/index-de.html

hab' denen mal eine mail gesendet ... mal schauen.

 

Beste Grüsse

 

Daniel

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http://www.koraat-knives.at/public_html/menu3submenu1.php

 

take a look here, Koraat has managed a smelting system with cokes,

http://www.koraat-knives.at/public_html/menu3submenu3.php

all in German pals

and a video, too:

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