REFINING OF CHROMIUM-CONTAINING STEEL AND CHROMIUM SENSOR USED FOR THIS METHOD

PURPOSE:To economically and accurately control chromium concn. at the time of tapping molten steel by obtaining the actual carbon concn. and chromium concn. based on the measured chromium concn. and solidified temp. at the oxygen-blowing decarburizing stage and executing the refining control according to the differences from the aimed values. CONSTITUTION:In a top and bottom combined blowing converter 10, the chromium concn. and the solidified temp. of the chromium-containing molten steel are measured by using a sub-lance 11 at the oxygen-blowing decarburizing stage. The chromium concn. is measured by using a probe-type chromium sensor. The top-blowing oxygen feeding rate, distance between the lance and the molten steel surface and a dilution ratio of the oxidizing gas with an inert gas are adjusted based on the actual carbon concn. calculated from the measured value and the actual chromium concn. and the differences from these aimed values, and as necessary, coolant 21 or temp. raising material 22 is charged. The produced quantity of the chromium oxide is restrained by executing the blowing through this on-line control, and the suitable reducing material 23 is charged in a reducing stage.