REFINING METHOD

• Main Authors: SAKAMOTO MOTOHIRO, KADOWAKI RYO, NAKAE TAICHI
• Format: Patent
• Language: English; Japanese
• Published: 15.07.2022
• Subjects: CHEMISTRY; METALLURGY; METALLURGY OF IRON; PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OFWROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS

To stably discharge a large amount of slag in intermediate deslagging after molten iron pretreatment in a converter type vessel.SOLUTION: The inventive refining method includes a first step for charging molten iron into a converter type vessel, a second step for adding lime flux and spraying acid to apply Si and P removal treatments to the molten iron, foaming the slag, a third step for performing intermediate deslagging to discharge slag out of a throat of the converter type vessel, and a fourth step for adding flux into the converter type vessel after intermediate deslagging, to perform top-blow refining. At the start of the second step, a Si content of the molten iron is 0.6 mass% or less. At the time when acid spraying is stopped in the second step, the slag has an Al2O3 content of 0.5 mass% or more and 5.0 mass% or less and a basicity of 0.8 or more and 1.5 or less. In the second step, a height of foaming is measured. At the time when acid spraying is stopped before intermediate deslagging, the height of foaming satisfies a formula (1).SELECTED DRAWING: Figure 3 【課題】転炉型容器における溶銑予備処理後に生成したスラグを中間排滓する際に、安定して多量のスラグを排出すること。【解決手段】本発明に係る精錬方法は、溶銑を転炉型容器に装入する第１工程と、石灰系フラックスを添加して吹酸することで溶銑に対して脱Ｓｉ処理及び脱Ｐ処理を施し、スラグをフォーミングさせる第２工程と、スラグを転炉型容器の炉口から排滓する中間排滓を実施する第３工程と、中間排滓後の転炉型容器内にフラックスを添加して、上吹精錬処理を実施する第４工程と、を含む。第２工程の開始時における溶銑のＳｉ濃度は、０．６質量％以下であり、第２工程の吹酸停止時におけるスラグについて、Ａｌ２Ｏ３濃度を、０．５質量％以上５．０質量％以下、塩基度を、０．８以上１．５以下とし、第２工程では、フォーミングの高さを測定しておき、中間排滓前の吹酸の停止時におけるフォーミングの高さが、式（１）を満足する。【選択図】図３