Inclusion morphology control steel and its manufacturing method

摘要

To present a condition for preventing nozzle clogging and suppressing MnS inclusion formation in REM-added steel and a production method thereof.SOLUTION: The steel comprises, on the percent by mass basis, Al: 0.005 to 0.5%, O: 0.0013 to 0.005%, Ca: 0.0005 to 0.0045%, and one or more of La, Ce and Nd with a total concentration of 0.0005 to 0.0035%. The number Nof an inclusion group A and the number Nof an inclusion B group are within a predetermined range in terms of the ternary mass concentration of the oxide R-O consisting of one or more of AlO, CaO and La, Ce, and Nd in the nonmetallic inclusion, and satisfy the relationship of the expression (3), whereby generation of MnS can be suppressed while keeping the cleanliness high. 0.6≤N/(N+N)≤0.75...(3)SELECTED DRAWING: Figure 2