I thought it would be harder to do.
The Rotarycraft blast furnace is just eight stonebricks around a redstone dust.
Placing it adjacent to lava will heat it enough for steelmaking unless you are in a taiga biome (snow).

Inputs are sand, charcoal/coal and gunpowder, and nine iron ingots. The coal is consumed, the sand is sometimes consumed and the gunpowder hasn't been used up yet.

There seems to be a random bonus output, you get at least 9 steel but sometimes more.

There is, if you fill all the slots with iron you can potentially get up to 15 steel. So it's always best to put at least 9 iron in each time you need some. I have enough iron to put 64 in each slot on the grid which nets me almost 2 extra stacks of steel.

You can also convert the steel to other mod steel by using the Ore dictionary block. Very handy indeed for some patterns that wont accept another mods ore of the same type. IC2 tin/mariculture tin for example.