Steelmaking Expanded

Stage I - the blast furnace and hot blast (click to expand)

The blast furnace is a tall multiblock built mostly from refractory bricks, with its own door, two tuyeres (hot-blast intakes) low on the shaft, two gas outlets (exhaust) high up, two hoppers on top, and two molten metal taps (the upper pours slag, the lower pours iron). Place the door first - it is the control block - then Ctrl + right-click for the build outline and fill it in.

The furnace does not consume ore directly; it burns blast mix (ore, fuel and flux). Load the ingredients into the reinforced hopper and the bell hopper drips blast mix down the shaft. Ignite it with a torch and close the door. While firing the temperature climbs to about 1400 degrees Celsius on its own - not enough to smelt iron - so you feed it hot blast through the tuyeres to push past iron's melting point (about 1482 degrees Celsius) and into the melting phase, where it turns the blast mix into a reservoir of molten iron and slag.

The furnace is temperamental: opening the door, running out of blast mix, a choked exhaust, or an overflowing reservoir all put the fire out and solidify everything inside into blocks you must clear before firing again. You cannot open the door while it fires, so keep it fed through the hoppers for continuous melting.

The hoppers:

• Reinforced hopper - holds crushed iron ore, crushed coke and lime, and combines 12 crushed iron, 3 crushed coke and 1 lime into 16 blast mix at a time, stockpiling it internally. It also accepts reclaimed blast mix.
• Bell hopper - sits below and deploys blast mix into the shaft, stopping on its own when the furnace is full. Dropping is on by default; toggle it with Ctrl + right-click.

Coke is baked from coal in a vanilla coke oven, and ore and coke are crushed in a vanilla pulverizer. The furnace needs a lot of both, so prepare ahead.

The cowper stove is a multiblock heat regenerator that makes hot blast. Pipe the furnace's exhaust into its intake and the flowing gas charges the stove's internal heat sinks; then route plain pressurised air (blast, above 2.5 atm) through the charged stove and it comes out scorching, hot enough to lift the furnace's ceiling to about 1700 degrees Celsius. Run two stoves as a pair: while one charges on exhaust, the other discharges hot blast, and you swap their roles with valves as the discharging one cools. Keep exhaust and blast on separate paths - if they mix inside a stove it cannot heat up.

Blast itself is made by an Air Blower, a steam-engine sub-machine (it sits in the engine's drive cell like the fluid pump or MP generator), so it runs on steam rather than an axle. Its output pressure is capped by the engine's inlet steam pressure, so feed the engine enough steam to reach the 2.5 atm the stove needs. Burning a coal pile in the open slot under the stove's intake speeds charging (anthracite is fastest); other fuels make the stove emit some exhaust of its own.

Finally, the smoke stack is a multiblock that vents surplus exhaust to the sky so the line does not back up and choke the furnace. Because it tries to consume all the gas in its network, use directional pressure valves to route exhaust to the cowper stoves first and only the overflow to the stack.

Stage II - the Bessemer converter (click to expand)

The converter takes molten iron and blows blast through it to burn off carbon and turn it into steel. It is the most demanding machine in the mod: it costs a lot of materials, needs both mechanical power and a blast supply, and only works as the final stage of an already-running molten line.

Place the control block, then right-click it with 1 large gear and 8 iron or steel rods in your hotbar to start the build (it spawns the converter vessel), and build it up through its stages. You also place a gas intake, a transmission, an input tap and an output canal start block. The gas intake and the transmission must face the same way as the control block, or they will not couple.

Connect mechanical power to the transmission with an axle (it needs high torque, so a steam engine suits it), pipe blast into the gas intake from an air blower, and run a molten canal carrying iron into the input tap with a second canal beneath to carry steel out.

To run it: set it to Filling and pour in molten iron, switch to Normal and it refines the charge at about 1800 degrees Celsius for roughly five minutes, then set it to Pouring to drain the steel into the output canal. The conversion is exothermic, so the charge holds its heat while it works - but pour it out in time or it solidifies. If it does solidify, break the converter with a steel pickaxe to recover the metal, or chisel out a small residue from the upper hatch once it hardens.

The molten network and casting (click to expand)

Liquid metal is poured through canals, not carried by pipes. Lay a Molten Canal (Start) as the anchor of a network, then run straights, bends and junctions out from it.

• Molten Metal Taps - drain the furnace (the lower pours iron, the upper pours slag), each into the start of a canal below.
• Canal Tap - pours metal out of the network into a barrel, a large mold, or the converter.
• Mold Pedestal - holds a fired mold and fills it from the network. The mod also adds larger plate, quad rod and double ingot molds, clay-formed and fired like any tool mold.
• Molten Barrel - bulk storage for molten metal; buffer excess iron or hold slag from the upper tap.

Mind the temperature: metal in the canals cools, and if it drops too far it solidifies in place. A hardened canal stops flowing - once it has cooled enough, chisel it out with a chisel and hammer to recover most of the metal as bits, which crush back into crushed iron. Keep runs short, keep them fed, and empty them before they go cold.

You can seal an empty straight canal with 4 fire clay to use it as a manual valve; it caps over and severs the network there, handy for isolating a section. A chisel breaks the seal and recovers 2 fire clay. A freshly filled mold is dangerously hot - holding one bare-handed burns you (wear heavy leather or a blacksmith's gloves), and a still-molten mold spills if you stash or rack it before it sets.

Byproducts and vanilla overrides (click to expand)

Smelting leaves byproducts, none of them wasted:

• Slag - grinds into powdered slag, which makes mortar when mixed with slaked lime in a barrel, or acts as a phosphate fertilizer on farmland.
• Loose blast mix - behaves like a coal pile, so you can lay it back down, stack it, feed it through the hoppers, or burn it as ordinary fuel in a pinch.
• Solidified metal - chisels out of canals and barrels as bits. Per vanilla, recovering hardened metal from a ceramic mold shatters the mold.

The mod also swaps a few vanilla classes for drop-in replacements (Harmony patches) so the molten line works. None of this changes vanilla recipes or balance - it only adds the plumbing the new machines need: filled tool molds can be carried and racked while still holding metal (a molten one spills if racked before it sets), the mold rack enforces that, coal piles gain blast-mix burn-to-slag behaviour, and the larger plate, double-ingot and quad-rod mold variants are added.

Warning! Scary diagrams!

Starter iron setup:

Starter steel setup:

Advanced steel setup:

Video walkthroughs (pre steam power - blast furnace reference)