SPRING STEEL AND METHOD FOR PRODUCING SAME

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Fatigue strength, toughness, and cold ductility are sought after in spring steel. A spring steel according to the present embodiment has a chemical composition containing, in mass%, 0.4-0.7% of C, 1.1-3.0% of Si, 0.3-1.5% of Mn, at most 0.03% of P, at most 0.05% of S, 0.01-0.05% of Al, 0.0001-0.002% of rare earth elements, at most 0.015% of N, , at most 0.0030% of O, and 0.02-0.1% of Ti, containing Ca, Cr, Mo, W, V, Nb, Ni, Cu, and B as optional elements, and having a balance comprising Fe and impurities. In the spring steel, the number of oxide inclusions having an equivalent circle diameter of at least 5 µm and being either composite oxides containing an Al oxide, REM, O, and Al, or composite oxides containing REM, O, S, and Al is at most 0.2/mm2. Furthermore, the maximum value for the equivalent circle diameter of the oxide inclusions is at most 40 µm.