| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high cleanliness spring steel having excellent fatigue properties by allowing the whole of inclusions to be made easy to deform at a low melting point, and allowing SiO<SB>2</SB>to be made hard to be generated even if phase separation is caused upon heating before hot rolling and during hot rolling. <P>SOLUTION: In the high cleanliness spring steel, oxide based inclusions with a width of≥3μm present on the surface layer side from the surface of the wire rod to a depth of 1/4 of the diameter satisfy inequality (1), further, the concentration of MgO is≤5 mass% (including 0 mass%) and the concentration of MnO is≤10 mass% (including 0 mass%), also, each concentration of SiO<SB>2</SB>, Al<SB>2</SB>O<SB>3</SB>and CaO in the oxide based inclusions satisfies prescribed relation, and further, when the Al<SB>2</SB>O<SB>3</SB>concentration [An], the SiO<SB>2</SB>concentration[Sn] and the CaO concentration [Cn] are expressed by an Al<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>-CaO three component system phase diagram, the melting point thereof is≤1,500°C: CaO+Al<SB>2</SB>O<SB>3</SB>+SiO<SB>2</SB>>80 (mass%) (1). <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
