POSCO Holdings Inc.
WIRE ROD AND STEEL WIRE FOR HIGH STRENGTH SPRING, AND MANUFACTURING METHOD THEREFOR

Abstract:

A wire rod and a steel wire for a high stress suspension spring for motorcycles, wherein decarbonization and low-temperature structure occurrence are easily suppressed when the wire rod and the steel wire are cooled down; and a manufacturing method therefor. A steel wire for a high strength spring includes, in percent by weight (wt %), 0.55 to 0.65% of carbon (C), 0.5 to 0.9% of silicon (Si), 0.3 to 0.8% of manganese (Mn), 0.3 to 0.6% of chromium (Cr), 0.015% or less of phosphorus (P), 0.01% or less of sulfur (S), 0.01% or less of aluminum (Al), 0.005% or less of nitrogen (N), and the remainder of iron (Fe) and inevitable impurities, satisfies Formula (1) below, and comprises 90% or more of a tempered martensite structure. In Formula (1), C, Mn, Cr, and Si denote contents (wt %) of the corresponding elements, respectively. (1) 0.77.ltoreq.C+(1/6)*Mn+(1/5)*Cr+( 1/24)*Si.ltoreq.0.83.