AUSTENITE-FERRITE TWO PHASE DUPLEX STAINLESS STEEL WITH HIGH STRENGTH, HIGH ELONGATION AND THE METHOD OF MANUFACTURING THE SAME

摘要

PURPOSE: Lean duplex stainless steel with high strength and excellent ductility, and a manufacturing method thereof are provided to secure more than 50% of elongation ratio by controlling the amount of plasticity organic martensite formation which is formed on an austenite phase, and the speed of the plasticity organic martensite formation according to an alloy component. CONSTITUTION: Lean duplex stainless steel with high strength and excellent ductility is composed of, in wt%: C: more than 0 to 0.08 or less; Si: more than 0 to 0.5 or less; Mn: 4-6; Cr: 19-23; Ni: more than 0 to 0.5 or less; N: 0.18 -0.40; and the remainder Fe and inevitable impurities. A phase structure includes a double phase structure which is composed of 20-65% of ferrite and 80-35% of austenite in volume fraction. An elongation ratio which is calculated by the below equation and the formed plasticity organic martensite are satisfied with the relation of the equation as below. Elongation ratio=48+80xplasticity organic martensite fraction^2>= 50. [Reference numerals] (AA) Elongation ratio[%]; (BB) Plasticity-induced martensite fraction