Technical fact: The properties of carbon steels.
Low carbon steel is also called mild steel and comes in the widest choice of shapes, everything from flat sheets to structural beams.
Medium carbon steel is stronger than low carbon and trickier to form, weld and cut. It’s often hardened and tempered with heat treatment.
High carbon steel is also called carbon tool steel, and is very difficult to cut, bend and weld. When heat treated it becomes very hard and extremely brittle.