HIGHLY CLEANED STEEL

摘要

A highly cleaned steel being excellent in cold forming property and fatigue characteristics, characterized in that, in the L cross section of a rolled steel, with respect to non-metal inclusions having a ratio of length (l) to width (d), l/d, of 5 or less, those having the composition A1 described below account for 20 number % or more, the sum of those having the composition A1 or B1 account for 80 number % or more, and non-metal inclusions having a l/d of 5 or less and the composition A1 have a d of 40 mu m or less, composition A1: SiO2: 60 % or more, composition B1: SiO2: 20 to 60 %, MnO: 10 to 80 %, and further 50 % or less of CaO and/or 15 % or less of MgO are contained. The highly cleaned steel being excellent in cold forming property and fatigue characteristics can be produced by use of a reduced amount of an alloy containing Ca and/or Mg.