Combined Effects of Ternary Compound Binders on Magnesia Wet-gunning Mixes for Tundish

摘要

Silicate fume (SiO2,SF),sodium tripolyphosphate (Na5P3O10,SP) and sulfamic acid (H3NSO3,SA) have been widely used as the binders of mag-nesia-based refractories.In this work,the combined effects of temary compound binders SF,SP,and SA on the water addition (WA),apparent porosity (AP) cold crushing strength (CCS),and slag resistance of magnesia wet-gunning mixes for tundish have been investigated with a simplex centroid design (SCD).Experimental results show that sample containing 2.0％ of SA indicates high CCS (8.5 MPa) and low AP at ll0°C,mainly due to large amounts of brucite generated.However,low CCS at 1100°C and 1500°C is observed for the same sample,which perhaps results from the decomposition of brucite at elevated temperature.Compared with SP and SA,addition of binder SF is more effective in enhancing the middle temperature strength.Side effects will take place at all temperatures if basic SP is employed as the binder of magnesia-based refractories in combination with acidic SA,which is presumably attributed to the prior SA reactions with SP.Slag resistance test performed in a temperature gradient furnace shows that 2.0％ SP Sample T1 or Sample T4 located at the center point of SCD diagram exhibits better slag resistance than 4.0％ SF Sample T2 or 2.0％ SA Sample T3 in terms of residual thickness of initial layers of crucibles.