In our previous video on crucible steel, we had produced an ingot that was essentially
unusable.
In this video, we look how the second ingot we produced behaves when forged.
The charge for the crucible consisted of about 1400g of cast iron and 1000g of 1018.
The glass we got from a bottle of tasty single malt scotch.
The process is very similar to the one shown before.
As this is the second charge, the furnace is quite hot already and does not take very
long to come to melting temperature.
It only took 19 minutes for everything to be completely liquid.
As the lid is still very hot and putting it back on the furnace is a two person operation.
To get the furnace back going, I just slowly turn the gas back up till it is running under
5 psi.
Now, we just wait till both the cast iron which melts first and then 1018 are completely
liquid.
The fact that the brick on which the crucible was resting crumbled in the furnace meant
that we had to remove the crucible while the charge was still completely molten.
As you can see the video, the bar of steel was we used to pry the crucible from the furnace
wall did not withstand the high temperatures.
Because the crucible had to cool down outside the furnace we could watch the pretty bubbles
made by the molten glass.'
After we removed the ingot, we thermal cycled it once and then tried to spark test it.
As a base of comparison, we first spark test cast iron, followed by mild steel and then
W1 tool steel.
Now, we try forging the ingot to see how it moves under the hammer and if it develops
any cracks.
Our concern is that instead of producing crucible steel, we just produced cast iron.
It is possible that we underestimated the carbon content of the cast iron used in the
charge or how much carbon would be absorbed from the clay graphite crucible.
So far it seems to move fine and we did not notice any major cracks.
In the next step we cut up the ingot and see how it behaves when heat treated.
This also gives us an opportunity to look at how it looks inside.
The small pieces we heat treated turned out to be very hard - a file just skidded over
it - but also very brittle as can be seen here.
A small piece we annealed seemed to break rather then bend which is not a good sign.
Afterwards, we took a quarter of the ingot and started forging it under the power hammer.
The part of the ingot attached to the handle was at the bottom of the crucible.
Unfortunately that part started to crack and come apart when forging whereas the part of
the ingot at the top of the crucible seemed to behave much better.
Once possible explanation is that the cast iron melted first and collected at the bottom
of the crucible since we had to remove the crucible early not enough mixing took place.
The part that forged developed a very subtle wood grain like pattern that can be barely
seen on the video.
Clearly more work and understanding is required.
More next time.