So I was just starting out on a new world and was messing around in a creative world beforehand to see how to automate the crucible as low tech as possible and I think Greg gifted us the most “build it and forget it” way yet to do it when introducing the hand crank.
Behold:
4 villagers cranking when combined through custom gear boxes and a Transformer gearbox are enough to power a LV Dynamo powering an LV Heater. A fifth villager cranks to add air to the crucible. The temparature is regulated by the Temparature sensor, which lowers and raises the villagers as needed. Since there is a constant airflow there will be some steel immediately once it is hot enough preventing it from casting until everything is converted.
The dropper adds full iron blocks whenever there was a successfull cast.
The rate should work well with an Iron Golem farm.
No Aluminium needed for controlling an electric heater 
I think it should be possible to upgrade to an MV heater by quadrupling the villagers and adding a transformer. But at that point one has aluminium and properly a proper power supply, so why bother^^ Same with HV since the heater needs Kanthal containing aluminium