Abstract: The present invention provides a spring steel with excellent performance, characterized in that the spring steel is produced by making a spring steel contain an appropriate amount of at least one or more of Ti, Nb, Zr, Ta, and Hf, thereby generating fine inclusions including carbide, nitride, sulfides and/or their complex compounds, to make the inclusions exert the effect of trapping diffusive hydrogen whereby the resistance to hydrogen embrittlement is enhanced, wherein the size and number of the coarse inclusions are regulated, thereby suppressing the decrease of the fatigue life. The spring steel can provide a valve spring or a suspension spring or the like, with enhanced strength and higher stress resistance, together with improved resistance to hydrogen embrittlement and fatigue.

Abstract: A high strength steel strand for PC of a wire material having a pearlite structure and containing 0.80 to 1.30% of C, 0.60 to 2.50% of Si and 0.30 to 1.50% of Mn, remainder being Fe and unavoidable impurities, wherein a cementite portion of the wire material comprises a mixed structure of fibrous cementite and granular cementite, the volumetric proportion of the granular cementite to the total cementite is 10 to 40%, the particle diameter of the granular cementite is 40 to 300.ANG., and the strand has a tensile strength of 235 kgf/mm.sup.2 or higher and an elongation of 3.5% or greater.

Abstract: Disclosed are a steel wire rod for manufacturing a fine steel wire excellent in drawability, strength and toughness in which the contents of components such as C, Si, Mn, P, S, Al, Cu are specified, the contents of one or more of elements selected from a group consisting of Cr, W, Ni and Mo are also specified, and in which the balance is essentially Fe and inevitable impurities and for which, the composition of non-metallic inclusions of oxides is also specified; a fine steel wire obtained by drawing of the steel wire rod; and a twisted wire cord made by twisting of the fine steel wires. Further, disclosed is a die schedule for manufacturing the above fine steel wire. Thus, there can be provided a steel wire rod with excellent drawability and which does not break during drawing; a fine steel wire excellent in strength and toughness obtained from the steel wire rod; and a twisted wire cord obtained by twisting together lengths of the fine steel wires.

Abstract: The fine steel wire according to the present invention has a high strength and high toughness, which is used as a rubber reinforcing material for a belt cord or tire cord, or as missile wires. Such a fine steel wire can be obtained by drawing a wire rod for a fine steel wire properly adjusted in its composition and structure, while applying working strain such that the total reduction of area in the final wire drawing step becomes 95% or more.