| 摘要 |
PURPOSE: To reduce the developing quantity of dust and to prevent the erosion of the refractory of a converter by arranging shielding plates each having a specific size on an opening part of a slit-type oxygen supplying tube having a concentric polygonal or a concentric circular cross section in a top-blowing lance. CONSTITUTION: Oxygen is blown on the molten steel surface from the top-blowing lance in a top-bottom combined blowing converter type refining furnace to stir and refine molten steel. In this top-blowing lance, one line of slit-type oxygen supplying tube having a cross section of concentrical 3-16 side polygonal or a concentrical circle is provided in the lance body 1. The tip part of the lance including the lance body 1 and a lance center point (a) is fixed through 2-10 pieces of the shielding plates 3 arranged to a part of the tip opening surface part 2 of the oxygen supplying tube. At this time, the ratio of the length B of a long side to the length (h) of a short side in the opening surface separated with the shielding plates 3 is made to satisfy B/h=10-225 and B×g/R=0.4-4, wherein R is the lance diameter and the angleωformed between points nearest each other on the circumference of the opening surface and the lance center point (a) is made to be 10-60 deg..
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