Research On A New Basic Packing Sand For Sliding-gate Of Steel Ladles

With development of clean steel manufacturing and attention paid on environment problems, highly qualified environment friendship packing sand are required, which not only ensure the free-opening of sliding-gate system for steel ladle, but also reduce its influence on the metallurgical process in tundish. Thus, high quality packing sand, with the properties of better flowability, smaller linear change as well as the sinterability are required, so that the sintered layer could be broken by the static pressure of molten steel.In this paper, an basic packing sand for sliding-gate systems for steel ladles was developed in the laboratory, which is composed of magnesia, corundum, calcite and potassium feldspar. The calcite added to the samples was used to make the packing sand fast sinter and form a compact sintering layer in high-temperature zone, moreover, not sinter in low-temperaure zone to avail the free-opening of sliding-gate system for steel ladle. The effect of composition, sintering temperature and holding time on sintering properties of packing sand was investigated, and the ingredient of high quality packing sand was determined. The following conclusions were obtained:(1) At high temperature, the liquid phase formed by the reaction between SiO2-Al2O3-MgO system and CaO derived from the composition of calcite added to samples accelerated the samples sintering. The apparent porosity of the packing sand samples added with 6mass% and 15mass% calcite and heated at 1500℃for 2h decreased to 4% below.(2) Compared with the sample with 15mass% calcite addition, the sample with 6mass% calcite addition and heated at 1500℃for 2h had better sinterability and can form a compact sintering layer in shorter time.(3) At 1500℃holding for 2h, the volume shrinkage of sintered samples caused by decomposition of calcite and sintering of samples was compensated by expension of spinel derived from reaction between magnesia and corundum. The sintered samples had high densification and small linear change. The radius shrinkage rates of samples with 6mass% and 15mass% calcite addition were lower than 5%. Comparing with in-situ packing sand, they had better volume stability. The radius shrinkage rate of sample with 15mass% addition was better than that of one with 6mass% calcite addition.(4) The sample with 6mass% calcite addition had faster sintering velocity, and the one with 15mass% calcite addition had better volume stability and higher basicity. Consequently, the two samples can be used to develop a new kind of highly basic packing sand.