METHOD FOR MELTING HIGHLY CLEAN NITROGEN-CONTAINING STEEL AND NITROGEN-CONTAINING STEEL PRODUCED BY THE MELTING METHOD

Japanese Patent JP2023160452

A

To provide a method for melting a highly clean nitrogen-containing steel capable of accurately adjusting the nitrogen concentration in a nitrogen-containing steel within a predetermined target range by changing RH treatment conditions in accordance with the nitrogen concentration in the steel during a RH treatment, and improving the cleanliness of the steel.SOLUTION: In melting a nitrogen-containing steel containing 0.03 mass% or more of [C] and having a target nitrogen concentration of 70 ppm to 150 ppm, the relationship 1 between the change of the nitrogen concentration in molten steel during a RH treatment and the treatment condition is obtained. The relation 2 between the difference between the nitrogen concentration in molten steel estimated from the relationship 1 and the nitrogen concentration in molten steel in operation results and the treatment time is obtained. The target nitrogen concentration and its range are set, the nitrogen concentration in molten steel is confirmed, the treatment condition is set using the relationship 1, the relationship between the remaining treatment time tr at the time of treatment and the time tm outside the range of the target nitrogen concentration is confirmed using the relationship 2, the treatment is carried out under the treatment condition. The nitrogen concentration in the molten steel is confirmed in the time Tm outside the range of the target nitrogen concentration when tr≥tm, the treatment is continued when tr