Abstract: A steel wire has tempered martensite, comprises, as essential components, by mass, C: 0.53 to 0.68%; Si: 1.2 to 2.5%; Mn: 0.2 to 1.5%; Cr: 1.4 to 2.5%; Al: 0.05% or less; further comprises, as a selective component, Ni: 0.4% or less; V: 0.4% or less; Mo: 0.05 to 0.5%; or Nb: 0.05 to 0.5%; and further comprises remainder essentially consisting of Fe and inevitable impurities, wherein the grain size number of prior austenite is 11.0 or larger, and the proof stress ratio (?0.2/?B), namely, a ratio of 0.2% proof stress (?0.2) to tensile strength (?B) is 0.85 or lower. Satisfying the above requirements makes it possible to produce a steel wire for high-strength spring excellent both in workability (cold workability), and in sag resistance and fatigue properties.

Abstract: A coil spring reduces Hertzian stress on a first turn and bending stress on a coil end. A coil end 11 is shifted in a diametral outer or inner direction of a coil spring relative to the first turn 13, to form a vertical gap between the coil end 11 and the first turn 13 in a free state without load on the coil spring. Due to the gap, the coil spring including the coil end 11 and first turn 13 can be entirely processed by shot peening as well as the remaining portion. The first turn 13 receives a combination of torsional stress and Hertzian stress (contact stress). Since the coil end 11 that receives high Hertzian stress is shifted in a diametral outer or inner direction of the coil spring relative to the first turn 13, a contact point on the first turn 13 is shifted in the diametral outer or inner direction to reduce the torsional stress on the first turn 13.

Abstract: A coil spring reduces Hertzian stress on a first turn and bending stress on a coil end. A coil end 11 is shifted in a diametral outer or inner direction of a coil spring relative to the first turn 13, to form a vertical gap between the coil end 11 and the first turn 13 in a free state without load on the coil spring. Due to the gap, the coil spring including the coil end 11 and first turn 13 can be entirely processed by shot peening as well as the remaining portion. The first turn 13 receives a combination of torsional stress and Hertzian stress (contact stress). Since the coil end 11 that receives high Hertzian stress is shifted in a diametral outer or inner direction of the coil spring relative to the first turn 13, a contact point on the first turn 13 is shifted in the diametral outer or inner direction to reduce the torsional stress on the first turn 13.

Abstract: A steel wire has tempered martensite, comprises, as essential components, by mass, C: 0.53 to 0.68%; Si: 1.2 to 2.5%; Mn: 0.2 to 1.5%; Cr: 1.4 to 2.5%; Al: 0.05% or less; further comprises, as a selective component, Ni: 0.4% or less; V: 0.4% or less; Mo: 0.05 to 0.5%; or Nb: 0.05 to 0.5%; and further comprises remainder essentially consisting of Fe and inevitable impurities, wherein the grain size number of prior austenite is 11.0 or larger, and the proof stress ratio (?0.2/?B), namely, a ratio of 0.2% proof stress (?0.2) to tensile strength (?B) is 0.85 or lower. Satisfying the above requirements makes it possible to produce a steel wire for high-strength spring excellent both in workability (cold workability), and in sag resistance and fatigue properties.