Getting started
Everything below works today.
This is the order to build things in, from prospecting to a cast part. Each stage is worth finishing before the next one is started: every one of them is useful on its own, and each feeds the one after it.
1. Prospect for bituminous coal and iron ore
Coal type is a real constraint here. The coke oven takes bituminous coal and nothing else, and coke is the fuel the whole tier runs on, so finding a bituminous seam is part of getting into iron rather than a detail. Iron ore is crushed in a vanilla pulverizer.
2. Bake coke
Build a Coke oven and raise its two chambers. Charge a chamber through its Charge Door, shut the door and the Charge Lid above it, and light the oven. A bake takes an hour of real time per chamber, and the two chambers run on their own clocks so one can be drawn while the other works. See Coke and fuel.
3. Make burden
Build a Burden Maker. It needs no power at all, so it can be built before there is an axle anywhere on the map. Crushed iron ore goes in the wide hopper and lime in the narrow one, and opening the gate drops both into the basin as Blast Burden. Aim for the standard grade, about one part lime in twenty. See Ore handling and burden.
4. Build the blast furnace
Build a Cold blast furnace: place its core and raise the stack from that. It wants two Tuyere ports low on the shaft, an Iron Tap and a Slag Tap in the hearth course, and a Tall Hopper over the mouth. The shaft inside stays hollow.
5. Blow it
Set a Twin-Tub Blower on an axle line driven by a vanilla waterwheel or windmill, and run Plated Piping (Straight) from it to both tuyeres on one network. Cap every other opening in the run or it will never build pressure. See Pipe networks and pressure.
6. Plumb the taps
Put a canal start under each tap spout and run a canal to a Sand Casting Bed. Pig cast on the bed comes out solid and carriable; slag cast on the same bed comes out as Slag Brick. The canal can wait if it has to, because metal that sets at the tap can be chiselled free by hand, but it is much less work to plumb it first. See Molten metal and casting.
7. Blow in and tap
Charge the shaft in rounds through the hopper, fuel then burden, until it is full. Start the blower. Break the plug out of a tap with an empty hand and hold a torch to the open tap. Out comes Pig Iron. See Furnaces and heat for what decides how hot the furnace gets.
8. Remelt into cast iron
Build a Cupola furnace. It takes pigs, chunks, bits and iron or steel scrap directly, layered with fuel, and pours cast iron. This is the point where iron stops being an intermediate and starts being parts. See Iron and its grades.
9. Cast a part
Build a Design Table and draft a Diagram, then carve it into a Pattern. Mix Green Sand from sand and blue clay. Build a Sand Casting Cell, ram it with green sand, press the pattern into it, and let the cupola's run fill it. What comes out is a Cast Iron Plate, a Heavy Cast Plate or whichever part the pattern named, and those are most of what every machine after this is built from. See Diagrams and the design table.
Where to go next
Wrought iron. A Puddling furnace turns pig into vanilla iron, one white-hot ball at a time.
The forming shop. A Rolling Mill, a Crop Shear and a Heating furnace on a line of Cast Iron Shaft turn stock into plate, rod and fasteners. No roll set is craftable in survival, so the mill cannot finish a schedule. See Rolling and the forming shop and Shaft power and the flywheel.
Steam. A Fluid Intake, a Manual Fluid Pump, a Cornish Boiler and a Watt Beam Engine with an Engine Fluid Pump under it close a water loop that feeds itself, and a Engine Crank instead of the pump turns axles. See Steam and boilers and Steam engines and sub-machines.
Crucible steel. A Crucible furnace melts vanilla blister steel into the best steel the works makes. It gates nothing; it is simply the better one.