| 摘要 |
A high-strength steel wire for heat-resistant springs has both excellent high-temperature tensile strength and excellent high-temperature sag resistance at a temperature as high as 350 to 500 DEG C, particularly at 400 DEG C or so (these properties are needed for spring materials). The steel wire contains (a) 0.01 to 0.08 wt% C, 0.18 to 0.25 wt% N, 0.5 to 4.0 wt% Mn, 16 to 20 wt% Cr, and 8.0 to 10.5 wt% Ni, (b) at least one constituent selected from the group consisting of 0.1 to 3.0 wt% Mo, 0.1 to 2.0 wt% Nb, 0.1 to 2.0 wt% Ti and 0.3 to 2.0 wt% Si, and (c) mainly Fe and unavoidable impurities both of which constitute the remainder. The steel wire has (a) a tensile strength of at least 1,300 N/mm<2> and less than 2,000 N/mm<2> before being treated with low-temperature annealing, and (b) a maximum crystal-grain diameter of less than 12 mu m in the gamma phase (austenite) in a transverse cross section of the wire.
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