Wootz steel is very high carbon steel made in clay crucibles in India two thousand years
ago.
One of the ways to create it is to carburize bloom iron with dried wood.
In our previous video we have documented our attempts at recreating Wootz-like steel.
We have made over 9 ingots so far and in this video we show the successful forging of one
of the ingots.
We start by drying out the new clay-graphite crucibles.
Instead of bloom iron won by reducing iron ore in a bloomery furnace, we use wrought
iron from old wagon tires.
In both cases, the iron has neglible carbon content.
The iron is being forged out into small strips and then cleaned to remove scale in order
to reduce gas production in the crucible.
Instead of dried wood as a carbon source, we using pulverized charcoal.
For a 2000 gram charge of wrought iron we use approximately 35 grams of charcoal.
We are aiming for a carbon content between 1 to 2%.
Wootz steel was reknown for the watered-steel sword blades that could be forged from it.
The appearance of watered-steel is due to carbides segragating along impurties caused
by alloying elements such as Vanadium.
Our source of Vanadium as well as some Chromium is from small pieces of O1 tool steel that
we add to the crucible.
We also add small amounts of calcium carbonate to help with the slag chemistry.
The calcium carbonate might help with removing some of the Sulfur from the resulting steel.
We cover the crucible with glass which acts as a flux and keeps the steel clean.
Afterwards, we seal the whole crucible with clay to help protect the charge from the furnace
atmosphere.
As a future improvement, we also plan to clay up the whole crucible since it seems to be
purous at high temperatures.
Once the furnace has been prepared, we fire it up and wait till it reaches a temperature
of about 3000 Fahrenheit.
We keep it at that tempature for 30 minutes and then let the furnace slowly cool down
to 2500 Fahrenheit before removing the crucible.
We then wait till the crucible is cold enough for us to inspect the ingot.
The crucible first needs to be freed of the clay until we can inspect the glass surface
that covers the ingot.
Just by looking at the glass we can tell how well we controlled the furnace temperatures.
Ideally, we are looking for a completely smooth surface without any bubbles as this indicates
that all gaseous reactions have completed by the time the steel became solid.
If the crucible is cooled down too fast the resulting ingot may contain a shrinkage cavity
and trapped bubbles inside of it.
We are hoping for a completely solid surface on the top.
So far everything looks very good.
Before working the ingot, we thermally cycle it to about 2000 Fahrenheit and let it cool
down very slowly.
Now comes the time to work the ingot.
Our goal is forge into a solid bar that can be used for sword blades or knives.
We forge the ingot so that the top forms the back of the blade and the bottom the cutting
edge.
The temperature at which the ingot is being forged is very important.
We want to forge above the temperature at which carbon dissolved into the iron matrix
but below the temperature at which all carbides are being dissolved.
The working range very much depends on the carbon content.
The lower the carbon content the smaller the working range.
Unfortunately, we have discovered some cracks that formed in the middle of the ingot.
Our attempts to grind them out failed and instead we resolve to cur the ingot in half.
As we can see there are small bubbles in the steel in the middle of the ingot that we need
to remove.
However, apart from that the ingot is forging very nicely and much better than our previous
attempts.
During this forging cycle on small cracks appeared that could be easily removed.
After forging the ingot out into a bar, we are eagerly looking forward to how the steel
looks.
To find out, we need to polish it to a high grit and then lightly etch it before any pattern
appears.
Here is the result.
While very difficult to see in the video, we have gotten closer to what one might consider
Wootz steel.
Now, we plan on forging the bar into a couple of beautiful knives.
While we need to get more experience, we seem to be on the right way.
More next time.