MANUFACTURING METHOD OF HIGH CLEANLINESS STEEL

• Main Authors: MIYAMOTO KENICHIRO, GOSHO TAKUMI, KANEYASU TAKAYUKI, SUZUKI HIDEJI, NAKAMURA RYOTA
• Format: Patent
• Language: English; Japanese
• Published: 26.04.2018
• Subjects: CASTING; CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES; CHEMISTRY; METALLURGY; METALLURGY OF IRON; PERFORMING OPERATIONS; POWDER METALLURGY; PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OFWROUGHT-IRON OR STEEL; TRANSPORTING; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS

PROBLEM TO BE SOLVED: To provide a manufacturing method of a high cleanliness steel capable of more reducing the number of alumina inclusions than conventional ones, especially reducing the number of alumina inclusions with particle diameter of 20 μm or less class.SOLUTION: After time when molten steel after primary refining is tapped in a tapping process and before a stirring treatment in a ladle refining process, caustic lime is input to the molten steel and/or slag, metal Al and/or a flux containing the same is added to conduct a modification treatment of the slag and make total of T.Fe concentration and MnO concentration of the slag at 5 mass% or less and dissolved oxygen concentration of the molten steel at 10 to 50 ppm, then the molten steel which is stirring treated in the ladle refining process is degasification treated by circulating the same in the vacuum degasification process, and the molten steel after standing for 10 min. or more is poured to a tundish 10 having a weir 16 partitioning a receiving part 13 for receiving the molten steel and a discharging part 15 for inputting the molten steel to a casting mold 14 for continuous casting formed inside with height of 0.3 to 0.8 times of molten steel depth H.SELECTED DRAWING: Figure 1 【課題】従来よりもアルミナ介在物の個数を低減でき、特に粒径が２０μｍ以下クラスのアルミナ介在物の個数を低減可能な高清浄鋼の製造方法を提供する。【解決手段】一次精錬を行った溶鋼を、出鋼工程で出鋼する時から取鍋精錬工程で撹拌処理する前までの間に、溶鋼及び／又はスラグに、生石灰を投入すると共に、金属Ａｌ及び／又はこれを含むフラックスを添加して、スラグを改質処理し、スラグのＴ．Ｆｅ濃度とＭｎＯ濃度の合計を５質量％以下、溶鋼の溶存酸素濃度を１０〜５０ｐｐｍとした後、取鍋精錬工程で撹拌処理した溶鋼を真空脱ガス工程で環流させて脱ガス処理し、１０分以上静置した溶鋼を、溶鋼を受け入れる受湯部１３と、溶鋼を連続鋳造する鋳型１４に注入する排湯部１５とに仕切る堰１６が内部に設けられ、その高さを溶鋼深さＨの０．３〜０．８倍としたタンディッシュ１０に注湯する。【選択図】図１