When did a-36 standard wide flange beam change to a572?

The transition from A-36 standard wide flange beams to A572 occurred in the late 1960s and early 1970s. A572, which offers higher strength and improved structural properties, was developed as a specification to meet the demands of modern construction. The A572 specification was officially introduced in 1966 and became more widely adopted in structural applications over the following years.