| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high cleanliness steel with a long rolling fatigue life by controlling the oxide composition in the steel to CaO-Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>-MgO system, and a method for producing the same. <P>SOLUTION: The high cleanliness steel is characterized by including a nonmetallic inclusion which has, by mass%, C concentration of 0.85% or more and 1.2% or less; Sol. Al concentration of 0.020% or more and 0.035% or less; Cr concentration of 0.50% or more and 2.0% or less; S concentration of 0.0020% or less; and total O concentration of 0.0020% or less; and also has a circle equivalent diameter of 1.0 μm or more and 10 mμ or less on a mirror polishing surface, when microscope observation is carried out on a sample cut from an iron slab after continuous casting and finished by mirror polishing. In the nonmetallic inclusion, Ca, Al, Mg, and O occupy 90 atom% or more among all the elements constituting the nonmetallic inclusion, and the number ratio of the nonmetallic inclusions having a CaO concentration of 20 to 50 mass% is 50% or more among all the number of the nonmetallic inclusions having a Ca concentration of 5 atom% or more. <P>COPYRIGHT: (C)2013,JPO&INPIT |
