Fe3C, also known as cementite, is a chemical compound composed of iron and carbon. It contains 6.67% carbon by weight and is a crucial component in the structure of steel and cast iron. Cementite is hard and brittle, contributing to the strength and wear resistance of these materials. In the context of metallurgy, Fe3C plays a significant role in the iron-carbon phase diagram, which illustrates how different phases of iron and carbon interact at various temperatures and compositions. Understanding cementite helps engineers and metallurgists design alloys with desired properties for various applications, including construction and manufacturing.