Why steel is preferred over copper, brass and aluminium in heavy-duty machines and in structural designs.

To increase the length of a thin steel wire of 0.1 cm² cross-sectional area by 0.1%, a force of 2000 N is required. The force required to produce the same strain in aluminium, brass and copper wires having the same cross-sectional area are 690 N, 900 N and 1100 N respectively. It means that steel is more elastic than copper, brass and aluminium. It is for this reason that steel is preferred in heavy-duty machines and in structural designs.