It is Saturday morning in the quiet San Jose mountains where we continue our search for
Wootz steel.
This is our third attempt at creating a high carbon ingot that is forgeable and exhibits
dendritic patterns.
These patterns result from carbides segregating around certain impurities in the charge.
For this experiment, we are preparing two clay-graphite crucibles that will be charged
with wrought iron, charcoal powder, O1 tool steel and glass.
As you notice we use only the highest quality ingredients.
We are aiming for 1.4% carbon for the first ingot and 1.6% carbon for the second ingot.
We do not know how much carbon will be absorbed from the crucibles themselves.
The reason for adding O1 tool steel into the mix is to provide a source of Vanadium and
Chromium.
It is around these impurities that the carbides with segegrate and create visible patterns
on the surface of the steel.
The glass acts as a flux and will completely cover the surface of the ingot protecting
it from oxygen.
We also add a little bit of Borax which may help with cleaning the steel.
As our source of carbon is from charcoal powder we need to completely seal the crucible that
the charcoal does not get burned up.
In this case, we use Satanite and the bottom of an old crucible to provide this seal.
In our previous experiments, we had run the furance inside of the shop.
As this resulted in a measurable increase of the ceiling temperature, we have set it
up to run outside today.
To ignite the propane, I place a burning paper at the bottom of the furnace where the propane
air mix enters.
The noise made by the furnace is quite impressive but is difficult to convey on the video.
For the first run in which the whole furnace needs to be heated up, it took about 35 minutes
to reach melting temperatures above 2800 degrees Fahrenheit.
In the mean time, the second crucible has been prepared and is setting in the sun for
the clay to dry.
The setup of the furnace is fairly simple.
We run at about 4.5psi of propane and the nozzle opening in the furnace has a diameter
of about 1 1/2in.
After we believe the charge to be completely molten we cool down the furnace a little bit
and wait another 30 minutes so that the liquid steel can solidify slowly.
Now it is time to remove the first crucible and place it in a bucket of vermiculite where
it can slowly cool down further.
The air from the furnace is very hot and face protection helps with the operation.
In this case we not only removed the crucible but also the pedestal it was resting on.
We need to rescue that for the next crucible.
Later in the evening, the crucible has cooled down enough for us to retrieve the ingot.
This is almost like unwrapping a Christmas present since we do not know what we will
find inside.
Here we have removed the refractory mortar and are about to remove the layer of glass
ontop of the ingot.
Some vigorous shaking is going to reveal it.
To get an idea how much carbon the ingot might have absorbed we do a quick spark test in
comparison with W1 tool steel which has a carbon content of about 1%.
However, a look at only the top already shows as segragation of carbides forming the dendritic
pattern we expect from a Wootz-like ingot.
Before starting to forge the ingot, it is time to look at what we got in the second
crucible.
Looking at the glass on top of the ingot reveals a very smooth surface indicating that at the
time the glass solidified there were no gaseous reactions happening.
While this ingot does not show as clear dendritic patterns as the first ingot some can still
be discerned.
Now, it is time to start working the first ingot.
The hope is that after some thermal cycling, it will deform without cracking or breaking.
For the first few operations, I very lightly employ a hydraulic press.
Unfortunately, the ingot is not behaving and big cracks developed which I am trying to
grind out without much success.
The subsequent operations just show how difficult it is to work this ingot.
The colors in the video do not correspond to the colors in reality.
While I am working with frustration on the first ingot, the second ingot is being thermally
cycled many times.
To make the best of this failure, I am going to take samples from the first ingot and get
their chemical composition analyzed.
Ultimately, all of this is a learning experience that will allow for improvements in the future.
However, before finishing this episode, here is a spectacular example of the challenges
posed by this ingot.
A light etch of it shows some very light patterning but experimenting with bringing out the pattern
first requires workable material.
As such, our search for Wootz continues.