This video shows our early experiments with creating crucible steel.
Crucible steel is best known from India where it was created as early as 300 BC.
It is known as Wootz steel and was used extensively in the manifacture of swords.
This is our first experiment with a furnace that is meant to reach temperatures up to
3000 degrees Fahrenheit which is sufficient for melting wrought iron.
We charge the crucible with approximately 1130 gramms of wrought iron and 17 gramms
of pulverized charcoal.
Crushed glass is used as a flux.
Since we are using charcoal we should have completely sealed the crucible to prevent
oxygen from reaching it.
However, as this is just an experiment we left the crucible open so that we could look
into it while the contents were slowly melting.
The furnace is made form an old compressor tank and lined with high temperature ceramic
fiber blanket and a layer of high temperature concrete.
The furnace is meant to withstand temperatures up to 3200 Fahrenheit.
Operatonally we are aiming for temperature around only 3000 degrees.
Lighting the furnace is a little bit exciting since the propane enters at the bottom of
the furnace and needs to ignite there, too.
We are slowly increasing the amount of propane and air till both the air and the propane
are at their maximum settings.
For this run, we set the regulator at the propane bottle to about 5 pounds per square
inch.
Also, notice that the propane bottle is suspended in a bucket of water to prevent it from freezing
up.
It takes a while for the furnace to come up to temperature since all the concrete needs
to heat up, too.
The first ingredient that is going to melt is the glass which ends up coating the wrought
iron.
We use a mirror and welding goggles to look inside to see what is going on.
This is not easy to capture with a video camera.
At this point in time the glass is molten and bubbeling in the crucible.
However, the iron is not hot enough yet to melt.
We use a long steel rod as a probe to determine if the whole charge is fluid.
If we reach the bottom of the crucible we know that everyting has molten.
The probe is very hot once it comes out of the furnace.
Once everyting has completely molten there are a lot of reactions going on inside of
the crucible as we can see from all the activity on the surface.
At this point, we have shut down the furnace and are working on extracting the extremely
hot crucible.
First we need to lift the lid.
Then we use a special pair of tongs, lift the curcible out of the furnace and let is
cool down in a bucket of vermiculite.
We also kept a log that tells us who long it took to reach melting temperatures.
For this run, we reached a maximum temperature of about 3110 Fahrenheit.
As can be seen on the graph we had run out of propane and need to reconnect a new bottle
which explains the dip in temperature.
After the crucible has cooled down, we slowly break away the glass that is covering the
crucible till the ingot drops out by itself.
At this point we can take a look at the end result.
As this was our first experiment, the results were not perfect.
Gaseous reactions in the crucible resulted in many bubbles that were trapped in the ingot
and the carbon content is much lower than we aimed for.
However, as a first experiment, this run was successful as we reached the temperatures
we were aiming for.