| 摘要 |
PROBLEM TO BE SOLVED: To evaluate an HIC (Hydrogen Induced Cracking) property on the stage of a cast slab without performing an HIC test.SOLUTION: A Ca concentration Caof molten steel within a tundish is investigated (S1). A Ca concentration Caof a slab of a charge same as that in the step S1 is investigated at two or more positions of which the thickness directions are different (S2), and a minimum Ca concentration Cais settled (S3). A threshold value of a Ca reduction amount not generating HIC is then settled using a Ca reduction amount Ca=Ca-Caand an HIC test result (S4 to S6). A Ca concentration Caof molten steel within the tundish is then investigated (S7) for a determination object charge, the Ca concentration of the slab is investigated (S8), and a minimum Ca concentration Cais settled (S9). When the Ca reduction amount Ca(=Ca-Ca) is greater than the threshold value (S10 and S11: YES), it is determined that HIC may occur, and the slab is used for any other purpose than sour-resistant steel (S12). |
