| 摘要 |
PROBLEM TO BE SOLVED: To provide a melting method of a steel excellent in hydrogen induced cracking(HIC) resistance by restraining the generation of non-metallic inclusion becoming the starting point of the development of the HIC. SOLUTION: When a Ca-treatment is executed to molten steel already receiving deoxidation, Ca concn. is controlled so as to satisfy the following formulas I and II regarding S and O concns. in the molten steel. Formula I: [%Ca]×[%S]<=3.5×104, Formula II: 1<= [%Ca]-(0.80+130 [%Ca])×[%O]}/1.25/[%S], wherein % in the formulas I and II is wt.%. In this way, an aspect ratio of the inclusion becomes <=20, and since the generation of MnS can be restrained, the deformed ratio of the inclusion is little at the rolling time, and since the inclusion is not acted as the starting point of the HIC, the steel having extremely excellent HIC resistance can be obtd. |
