Iron and its grades
as of 0.8.0
Iron is not one material here. Four grades exist, each made a different way, and only one of them is vanilla iron. Everything starts as pig, and which grade a player ends up with is a choice of which furnace to send the pig to.
| Grade | Melting point | Made in | Forgeable | What it is for |
|---|---|---|---|---|
| pig iron | 1150 C | Cold blast furnace | no | the shared intermediate; nothing else |
| cast iron | 1200 C | Cupola furnace | no | cast parts, plates, rods, machinery |
| wrought iron | vanilla iron | Puddling furnace | yes | vanilla iron, and rolled stock |
| crucible steel | 1600 C | Crucible furnace | yes | tools and weapons that last |
Metal is counted in units throughout. The rule is one voxel cubed is 2.5 units, so charge units, mold capacities and melt yields are all the same currency.
Pig iron
The Cold blast furnace reduces ore burden and pools molten pig iron behind its Iron Tap. It recovers 8.5 units of iron and about 1.4 units of slag per unit of ore content in the burden it melts, held at a 6 to 1 ratio. Tapped into a canal that ends at a Sand Casting Bed, the heat freezes into carriable pigs; the same bed casts a slag heat into Slag Brick instead, so a slag tap needs no second station.
| Item | Units |
|---|---|
| Pig Iron | 375 |
| Pig Iron Chunk | 25 |
| Pig Iron Shot | 5 |
A pig on an anvil does not forge. The helve hammer shatters it into chunks and bits instead, which is how a 375-unit pig becomes something that fits in a cupola pile or a smaller recipe. Pig is high-carbon, hard and brittle, and it is useless for tools by design: if it could be forged the Puddling furnace would have no reason to exist.
Cast iron
The Cupola furnace remelts pig and scrap into cast iron. It takes pigs, chunks, bits and iron or steel scrap directly, layered with fuel, with no prepared burden of any kind, and yields 5.0 units of cast iron and 0.67 units of slag per unit of charge. That is flat: a cupola remelts rather than reduces, so there is no ore share to scale it by.
Cast iron is poured, never beaten. It casts into Cast Iron Plate, Cast Iron Rod, Cast Iron Nails and Strips, a full set of cast tools, and the heavier machine parts the tier is built from: Heavy Cast Plate, Cast Shell, Cast Wheel Section, Cast Barrel (Unlined). It substitutes for vanilla iron in build recipes. See Molten metal and casting for how the casting stations work.
Wrought iron
The Puddling furnace decarburises pig into wrought iron, which is vanilla iron. It never melts iron at all: it works the bath at 1400 C, which sits between pig iron's 1150 and wrought iron's 1482, so pig melts down and the decarburised metal comes to nature and balls up instead of staying liquid.
A heat is three rows of three pigs. Each row is fettled with Puddling Fettle first, then charged. The bath melts down at 8 per cent of a full charge per cycle, on the firebox's 10-second cadence, so a full bed goes down in about two minutes of held heat. Then the work is manual: a Rabbling Bar gathers one Puddled Ball out of the bath per stroke and a Puddler's Paddle draws one off the bed, both through the small working door, with a 3-second cooldown shared between them.
| Quantity | Value |
|---|---|
| pigs per hearth | 9, three rows of three |
| metal in one heat | 3375 units |
| Puddled Ball | 200 units |
| balls per heat | 16 |
| Tap Cinder raked out when the bed is cleaned | 3 |
| balls per Shingled Bar | 2 |
The remainder that does not make a whole ball stays in the bath and comes out as Tap Cinder, which grid-crafts back into exactly the three fettlings the next heat's three rows want. A running furnace never needs ore for its bed again.
Balls go under the helve to be shingled. Two make a Shingled Bar, which is rolling stock; see Rolling and the forming shop.
Crucible steel
Crucible steel is melted whole in a sealed pot, so it comes out with no slag streaks and no soft spots. The feedstock is vanilla blister steel from the stone coffin, and the crucible process is bolted onto the end of that route rather than replacing it.
A cold blister ingot on an anvil is crushed rather than forged: one ingot comes back as 3 Crushed Blister Steel chunks and 5 bits, 100 units in total. Heat the same ingot first and it forges into shear steel exactly as it always did; the only thing choosing between the two is whether the metal is hot.
| Quantity | Value |
|---|---|
| charge per pot | 110 units |
| yield per pot | 100 units |
| melt loss | about 9 per cent |
| heats a pot gives before it breaks | 3 |
| process temperature | 1600 C |
The pot is fire clay, clayformed and fired in a pit kiln. Ordinary clay will not hold 1600 C, which is why the recipe asks for fire clay and nothing else. A finished pot is pulled with an empty hand and poured into a canal start, a Molten barrel or a Cast Iron Ingot Mold; one pot fills one mold exactly.
Slag
Slag is tapped alongside the iron and it is not waste. It casts into Slag Brick on the bed, lays as Slag Path, Slag Path Slab and Slag Path Stairs, and builds as Slag Bricks, Slag Brick Slab and Slag Brick Stairs. Ground, it becomes Powdered Slag.
What goes wrong
A pig will not forge. It is not meant to. Put it on the anvil to break it into chunks and bits, or remelt it.
A cupola is being charged with burden. Ore burden in a cupola burns, counts toward the fire and converts to nothing, and it pins the furnace in the Firing state. Charge metal, not burden.
A pot cracked. It was taken into full draught cold. The preheat is run with the damper shut for a reason; see Crucible furnace.
A blister ingot forged into shear steel instead of crushing. It was hot. Crushing needs it cold.
Tap cinder is piling up. One heat's cinder is next heat's fettle. It is a fixed 3 per heat precisely so the loop closes rather than accumulating.