YIELDING BEHAVIOR OF SOME MN-MO-NB PIPELINE STEELS

Experimental laboratory heats of pipeline steels containing 0. 1% C, 1. 6% Mn, 0. 2% Mo and 0. 04% Nb were rolled to plate and properties measured. These properties were influenced by small changes in manganese content within the range 1. 5-1. 6%. Although all steels had continuous yielding stress-strain curves, the initial shape of the curve varied with microstructure. The microstructures of the higher manganese steels contained more bainite, martensite and retained austenite, which caused an increase in work-hardening rate, tensile strength and impact transition temperature.