| 摘要 |
<p>A steel wire for a cold-formed spring according to the present invention contains a prescribed chemical component composition, wherein: a martensitic transformation start temperature M S1 shown by the following expression (1) is in the range from 280°C to 380°C; the austenite grain size number N of austenite grains is No. 12 or more; the grain boundary share of carbide precipitated along the austenite grain boundaries is 50% or less; the amount of retained austenite after austenitized and tempered is 20 vol.% or less; and the tensile strength is 2,000 MPa or more; M S 1 = 550 ˆ’ 361 €‰ [ C ] ˆ’ 39 €‰ [ Mn ] ˆ’ 20 €‰ [ Cr ] where [C], [Mn] and [Cr] represent the contents (mass %) of C, Mn and Cr, respectively. Such a steel wire can: secure hot-rolling formability and subsequent drawability while aiming at higher strength and higher stress; moreover exhibit excellent corrosion resistance; and obtain a spring (mainly a suspension spring for an automobile) excellent also in fatigue strength which is a basic required characteristic.</p> |
