A spring steel containing SiO.sub.2, Al.sub.2 O.sub.3, CaO, and MgO as oxide type inclusions, which have an average composition (by weight) of 35%.ltoreq.SiO.sub.2.ltoreq.75%, 5%.ltoreq.Al.sub.2 O.sub.3.ltoreq.30%, 10%.ltoreq.CaO.ltoreq.50%, and MgO.ltoreq.5% (excluding 0%). This spring steel is superior in fatigue properties.

Un acero del resorte que contiene SiO.sub.2, Al.sub.2 O.sub.3, el CaO, y el MgO como tipo inclusiones, que del óxido tienen una composición media (por el peso) de el 35%.ltoreq.SiO.sub.2.ltoreq.75%, 5%.ltoreq.Al.sub.2 el O.sub.3.ltoreq.30%, el 10%.ltoreq.CaO.ltoreq.50%, y el MgO.ltoreq.5% (excepto el 0%). Este acero de la primavera es superior en características de fatiga.