The lowest Technology Readiness Level (TRL), where scientific
research begins to be translated into technology’s basic
With the mass industrialization of structural steel welding for
shipbuilding in World War II, the quest for high-strength steels with good
weldability was a motivation for metallurgical research that continued through
the post-war era. Carbon strengthening and alloying that resulted in high
strength was counter to weldability. The fundamental metallurgical tools for
steel alloy design (e.g., phase transformation, phase diagrams, relationship
of microstructure to properties, precipitation strengthening, and so forth)
were developing at a dramatic rate along with the U.S. steel industry.
In the 1930s, the unique property of precipitation hardening
induced by alloying of copper in steel was established. The phase diagrams for
the Fe-Cu system were formulated, the solubility limits of Cu in low carbon
steel were explored, and laboratory studies of copper steels were conducted.
However, the benefit of Cu-strengthening as a means toward optimum strength,
toughness, and weldability was not recognized.
Smith, C.S. and E.W. Palmer, “The Precipitation-hardening of
Copper Steels,” Trans. AIME, Vol. 105 (1933).