This guy tried to make crucible steel by heating chunks of steel in a crucible in a propane / forced air furnace for four hours (and he ran out of gas from a large tank) but it did not melt ... I think melting steel in a propane furnace is not feasible. The other guy made a furnace with Kaowool on the outside lining with plaster of Paris and sand for melting aluminum and on the start of the video it says '1500 C', while he barely got 1500 F.
It's possible to cast monel which melts at around 1400 degrees C with a propane furnace, you just need a high rate of burn and a 200Kg cylinder hooked up to it. Actually now that I think of it the same person told me molten steel in the same furnace begins to foam and react with oxygen and makes a huge mess which is probably why they use bottom pour crucibles with steel
I had a go at melting ball bearing steel in my propane furnace, all the steel oxidizes and ends up as a foamy slag.
I cast the smallblock using only propane in 1997, but I had only been casting for a couple years, so I didn't know I couldn't do it. And forums like this did not exist. I'm still using the same Gingery crucible furnace, but with better insulation and in 2015 added waste oil capability.