POSCO Holdings Inc.
WIRE ROD FOR GRAPHITIZATION HEAT TREATMENT, GRAPHITE STEEL, AND MANUFACTURING METHOD THEREFOR

Abstract:

A graphite steel available as a material for mechanical parts of industrial machines or automobiles, and more particularly, a steel wire for graphitization heat treatment and a graphite steel and methods of manufacturing the same. The graphite steel includes, in percent by weight (wt %), 0.6 to 0.9% of carbon (C), 2.0 to 2.5% of silicon (Si), 0.1 to 0.6% of manganese (Mn), 0.015% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.01 to 0.05% of aluminum (Al), 0.01 to 0.02% of titanium (Ti), 0.0005 to 0.002% of boron (B), 0.003 to 0.015% of nitrogen (N), 0.005% or less of oxygen (O), and the remainder of iron (Fe) and inevitable impurities, and satisfying Equation (1) below: wherein graphite grains are distributed in a ferrite base as a microstructure and a graphitization rate is 100%, (1) -0.003<[N]-[Ti]/3.43-[B]/0.77<0.003, wherein in Equation (1), [Ti], [N], and [B] are wt % of titanium, nitrogen, and boron, respectively.