Steel

About
Steel is a strong metal that can be used in many construction applications. It has a much higher blast resistance than aluminum, gold, and iron, the three other metals that can be used in construction.

Steel comes in blocks, slabs, and stairs (see bottom).

Types
There are 3 types of steel on AA:
 * Low-grade steel: cheap and versatile, has the lowest blast resistance of any steel, but still 2x higher than aluminum
 * Construction steel: more expensive than low-grade steel, but has a considerably higher blast resistance
 * Industrial High-Strength steel: Most expensive, but has a blast resistance 5x higher than low-grade steel

Images
Low-Grade Steel Construction Steel Industrial High-Strength Steel Bunker made from all three types of steel

All three types of steel have stair and slab variants as well: