Steel

Steel is an industrial refined material used for high-performance construction and late-game fabrication. It is produced at the Metal Refinery and becomes available to manufacture after Iron, Refined Carbon, or Lime has been discovered. The standard recipe is 70 kg Iron + 20 kg Refined Carbon + 10 kg Lime = 100 kg Steel, and it requires Duplicant operation. Because Iron and Refined Carbon can usually be mass-produced more easily than Lime, Lime is often the limiting ingredient.

As a building material, Steel raises a building’s Overheat Temperature by 200 °C, making it one of the best choices for hot environments such as the Oil Biome and Space Biome. It can be used in places where Metal Ore would normally be required, as well as in buildings that normally use Refined Metal. Its high heat tolerance makes it especially valuable for infrastructure that must survive long-term exposure to extreme temperatures.

Steel is required for several late-game and hazard-resistant constructions and recipes:

• Bunker Doors and Bunker Tiles, which are used to withstand Meteor Showers in the Space Biome.
• All Rocket buildings, including the Gantry.
• All parts of the Great Monument.
• Serum Vials in the Apothecary, at a cost of 1 kg Steel + 1 Sun Nymph Egg = 1 Serum Vial.
• Jet Suits, at a cost of 200 kg Steel + 25 kg Petroleum = 1 Jet Suit.

Before the Launch Update, this attribute’s name was Tinkering.