Why did steel replace cast iron for many structural uses in the late 19th century?

In the late 19th century, steel replaced cast iron for many structural uses primarily because it offered superior mechanical properties. While cast iron was an early structural metal capable of bearing loads, it is brittle and possesses significantly more compressive than tensile strength, making it less effective for beams and complex structural applications.12

In contrast, steel is more uniformly strong, elastic, and workable, with high resistance to all types of stress that can be precisely calculated. The mass production of steel, facilitated by innovations such as the Bessemer process, made it a cost-effective and abundant alternative to iron. Furthermore, the ability to roll steel into versatile shapes—such as I-beams, angles, and channels—allowed for the creation of stronger, taller, and more rigid structures. These advancements in construction technology enabled engineers to achieve greater unsupported spans and fundamentally transformed architectural design.1345