| 摘要 |
A steel for high-cleanliness springs which is significantly reduced in the content of SiO2 inclusions and is useful for producing a spring having excellent fatigue characteristics. The steel for high-cleanliness springs is a steel which contains, in terms of mass%, 0-1.2%, excluding 0%, C, 1.2-4% Si, 0.1-2.0% Mn, and 0-0.01%, excluding 0%, Al, the remainder being iron and unavoidable impurities. It is characterized in that, among the inclusions in the steel, the total number of oxide inclusions which have an oxygen concentration of 25 mass% or higher and an SiO2 content of 70 mass% or higher when Al2O3+MgO+CaO+SiO2+MnO is 100 mass% and in which the L (major-axis inclusion length)/D (minor-axis inclusion length) is 4 or more and D is 25 mum or larger and oxide inclusions which have the oxygen concentration and SiO2 content and in which the L/D is less than 4 and L is 25 mum or larger is 20 or smaller per 500 g. |
