Method of manufacturing a low-phosphorus steel and steel refining process using a converter

摘要

PROBLEM TO BE SOLVED: To provide a method for stably producing a large quantity of low phosphorus steel and for achieving a high-efficient steel-making refining process without using halide material such as fluorite and Al₂O₃ source in the whole steel-making refining process using a converter.;SOLUTION: When the low phosphorus molten steel is produced by blowing to pre-dephosphorized molten iron with a top and bottom blowing-type converter, the mass-concentration in slag after blowing is controlled to be ≤3.5% Al₂O₃, ≥15% T.Fe and further, the mass-concentration ratio of CaO to SiO₂ (CaO%/SiO₂%) is controlled to be 4.0 to 6.0, and thus, the converter slag of which free CaO mass concentration is adjusted to adjusted to ≥7% free is simultaneously produced, and when performing dephospherizing treatment to the molten iron which has not received pre-dephosphorizing treatment and of which Si mass-concentration is ≥0.20% by using the top-bottom blowing type converter, the dephosphorizing treatment is performed by using the converter slag produced in the process, as a part of the dephosphorizing agent.;COPYRIGHT: (C)2011,JPO&INPIT