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 and 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 13 forming a molten steel flow passage 17 communicating a receiving part 14 and a discharging part 15 formed inside with a height position from a bottom face 22 of the receiving part 14 of an aperture 19 in a side of the receiving part 14 of the molten steel flow passage 17 of 0.2 times or lower of molten steel depth of the receiving part 14 and induction heated in the molten steel flow passage 17.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、出鋼工程での出鋼から取鍋精錬工程での撹拌処理を行う前までの間に、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、受湯部１４と排湯部１５を連通する溶鋼流路１７を形成した堰１３が内部に設けられ、溶鋼流路１７の受湯部１４側の開口部１９の受湯部１４の底面２２からの高さ位置を、受湯部１４の溶鋼深さの０．２倍以下としたタンディッシュ１０に注湯し、溶鋼流路１７で誘導加熱する。【選択図】図１