PURPOSE:To obtain the super fine grain ferrite steel consisting of metallographical structure including many equiaxed ferrite grain surrounded with great inclination grain boundary, by working, in a hot state, low alloy steel by regulating C content without alloying any special element. CONSTITUTION:The steel slab containing not more than 0.3% C, alloy content excepting C of not more than 3%, and not practically containing Nb, Ta, Mo and W, is rolled within a range of temperature practically consisting of austenite range near the transformation point Ar3 with continuous rolling, etc. When processed in this hot rolling, the transformation and recrystallization of austenite are promoted and the grain size is reduced. The super fine grain ferrite steel of metallographical structure including not less than 70% of equiaxed ferrite crystal surrounded with great inclination grain boundary of not more than 4mum in average particle size can be provided as rolled in a hot state thereby. This steel member is excellent in characteristics such as tensile strength, yield stress, etc. and has sufficient ductility and workability as practical steel.
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