PROTECTIVE MATERIAL FOR PREVENTING POROUS PLUG FROM BEING MADE IMPERMEABLE TO GAS

摘要

PURPOSE:To enhance the yield of high quality steel by specifying the amts. of ZrO2, SiO2 and Al2O3 as the constituents of a protective material and the grain size of the material so as to prevent the material from being washed away or sintered by a flow of molten steel in the early stage of tapping. CONSTITUTION:A protective material 4 for preventing a porous plug from being made impermeable to gas is composed of 40-50wt% ZrO2, 40-50wt% SiO2 and 5-10wt% Al2O3 and the grain size of the material is regulated so that granules of 2-10mm grain size account for =80% of all the granules. The protective material 4 is put on the gas blowing surface of a porous plug 1 fixed in the bottom of a vessel contg. molten metal 5.