Yeah, about that. I'm still extremely curious about the formula for steel crucibles. I've figured out or been told the formulas for almost every other aspect of the game, at least the crafting aspects. But I've asked numerous times and never received an answer about the crucibles. The temperature system is particularly perplexing since it has the possibility of being so variable throughout the process. My favorite theories are:
1) The temperature only matters at the very end of the process so you can leave it at 0% the entire time and let it drop to 100% right as the steel finishes
2) It is simply (wroughtQ + coalQ + tempA*fuelQ)/3 where tempA is the total average % that the temperature was throughout.
I'm still not sure how it would even calculate the average temperature unless it picks an arbitrary measurement of time. I suppose each fuel tick would make the most sense.