Spring steel and spring superior in fatigue properties

摘要

Disclosed is a spring steel which contains, by mass, 1.2% or less C; 0.1% to 2% Mn; 0.2% to 3% Si; 0.0003% to 0.005% A1; 0.03 to 8 ppm Li; 30 ppm or less (excluding 0 ppm) Ca; and 10 ppm or less (excluding 0 ppm) Mg. The steel contains oxide inclusions satisfying the following conditions (1) to (3) in a number of 1 x 10 -4 or more per square millimeter: (1) containing a total of 80 percent by mass or more of Al 2 O 3 and SiO 2 based on the inclusion composition excluding Li 2 O, (2) having a ratio by mass of Al 2 O 3 to SiO 2 of from 1:4 to 2:3; and (3) containing lithium (Li). The spring steel gives a spring that exhibits superior fatigue properties without strict control of the average composition of inclusions.