Abstract
Free-cutting steel (grade A12) is produced in a two-vaned steel-making unit (capacity of 180×180 tons) and processed on a ladle-furnace unit (LFU) in the electric steel-making shop of PJSC "Magnitogorsk Iron and Steel Works". The sulfur required for free-cutting steel is added into the metal with a flux-cored wire. The assimilation of sulfur in the process of ladle treatment of A12 free-cutting steel is considered in the paper. The production data array from 38 heats was analyzed. The dependences of the sulfur distribution coefficient on the basicity of the slag, the content of manganese oxide in the slag and the total content of iron and manganese oxides are established in the work. Dependences of sulfur assimilation on the silicon content in the metal, the ratio of the manganese content to the silicon content and the ratio of the calcium content to the aluminum content were revealed. For increase the efficiency of sulfur assimilation a flux-cored wire with a diameter of 14-16 mm is added to the metal during ladle treatment. It is recommended to provide a slag basicity of no more than 1.5, oxide content manganese in the slag is more than 2.5%, and the amount of iron and manganese oxides are more than 4.5%; the silicon content in the metal is 0.20-0.35%; the ratio [Mn] / [Si] is not more than 4.0; the ratio [Ca] / [Al] is equaled to 0.2-0.3 during casting with an open jet and 0.4-0.5 during casting with a closed jet.
Keywords
Free-cutting steel, ladle-furnace processing, flux-cored wire, sulfur, assimilation.