Steel furnace

The steel furnace is an intermediate smelting building used to convert ores into plates and stone into stone bricks. It is an upgrade of the stone furnace with double the crafting speed, and it appears as the mid-tier furnace between the stone furnace and the electric furnace in a typical tech progression.

A steel furnace can be placed directly on top of an existing stone furnace to replace it without mining first. Placing a steel furnace onto a stone furnace transfers all items from the stone furnace into the new steel furnace and immediately replaces the structure. Like all burner-type devices, the steel furnace requires fuel and cannot be placed in space.

Performance and fuel usage mirror the stone furnace but at twice the output rate: a steel furnace produces 0.625 units/second of iron plates, copper plates, and stone bricks, and 0.125 units/second of steel plates. Its coal consumption is the same as a stone furnace at 0.0225 coal/second, making it more fuel-efficient per unit of output compared with the stone furnace.

Practical notes and interactions:

• Use steel furnaces to double smelting throughput without switching to electricity; they are ideal when coal is abundant or electric power is limited.
• Replace existing stone furnaces in-place by clicking the stone furnace with a steel furnace in hand to preserve contents and layout.
• Since steel furnaces consume coal, factor fuel supply (belts, inserters, or dedicated burner inserters) into smelting arrays to avoid interruptions.
• Steel furnaces produce the same set of products as stone and electric furnaces (iron/copper plates, stone bricks, steel plates) but differ in power source and speed; they match electric furnaces in output but not in the ability to use modules or require electricity.