STEEL WITH STRUCTURE COMPOSED ESSENTIALLY OF FINE FERRITE, AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a ferritic steel having high strength and long fatigue life. SOLUTION: This steel with a structure composed essentially of fine ferrite has a fine ferritic structure of <=5μm average grain size, in which wide-angled grain boundaries of >=15 deg. comprise >=60% of the ferritic grain boundaries. As to the method of manufacturing the steel with a structure composed essentially of fine ferrite, a steel capable of forming ferritic phase is worked at a temperature not higher than Ac1 and then recovered and recrystallized, by which the steel with a structure composed essentially of fine ferrite, which has a fine ferritic structure of <=5μm average grain size and where wide-angled grain boundaries of >=15 deg. comprise >=60% of the ferritic grain boundaries, can be manufactured.