DEVELOPMENT OF HIGH STRENGTH AND TOUGHNESS MICROCOMPOSITE HSLA FE/CR/MN/C STEEL WITH AND WITHOUT NB

Microcomposite steels have been designed to consist of fine packet martensite and interlath austenite films in order to attain mechanical and corrosion properties with superior combinations of strength, fracture toughness, and formability in certain conditions. In an effort to improve these properties for on-line production in a hot mill for rounds and plates, modifications with niobium have been investigated and the CCT diagrams determined. The addition of niobium has achieved grain refinement without destroying the microcomposite morphology of packet martensite and austenite. Comparisons of properties, structure and processing are presented. 7 refs., 19 figs., 3 tabs.