STEELMAKING METHOD USING IRON-SCRAP AS MAIN RAW MATERIAL

摘要

PPROBLEM TO BE SOLVED: To make reduction-recovering of a part of Mn into molten steel as a product, since most parts of Mn in raw material are disposed with oxidized slag, in a steelmaking method in an electric furnace using iron scrap as the main raw material. PSOLUTION: The raw material is melted and successively, the usual oxidizing-refining is performed and the greater part of the oxidized slag is remained in the furnace, and when tapping off the molten steel, this slag is moved into a ladle together with the molten steel. At the same time, a reducing agent corresponding to a low-grade oxidized amount in the slag, is charged. An upper and lower airtight cover is attached on the ladle and the pressure in the ladle is reduced and a reduction-refining is performed by performing gas-bubbling to reduction-recover Mn in the slag. The greater part of dephosphorization with the oxidizing-refining is returned back as the phosphorus, and P content is increased, but a steel ingot is formed with a continuous casting method, wherein this ingot is composed of a chilled and columnar crystal in the solidified structure without generating the center segregation. In this way, action of impurity P as a toxic element, is weakened. PCOPYRIGHT: (C)2009,JPO&INPIT