Abstract: CaO-containing refractories have the functions of desulfurization and dephosphorization.The introduction of CaO into MgO-based tundish dry mixes is conducive to improving the cleanliness of molten steel.As a common calcium source,high-silica dolomite is difficult to apply in refractories due to its high SiO₂ contents.First,high-silica dolomite raw materials were lightly calcined at different temperatures (700,800,900,1000 and 1 100 ℃) for 3 h,respectively,followed by heavy calcination at 1 600 ℃ for 3 h to prepare high-silica dolomite clinker.Subsequently,MgO-CaO based dry ramming mixes for tundishes were fabricated using the high-silica dolomite clinker heavy calcined after light calcining at the optinal light calcining temperature (0,15%,30%,45% and 60%,by mass) and fused magnesia as raw materials.The effects of the light calcination temperature on the properties of high-silica dolomite clinker,as well as its influences on the phase composition and performances of MgO-CaO tundish dry ramming mixes were investigated.The results show that during the heavy calcination at 1 600 ℃ for 3 h after the light calcination of high-silica dolomite at 1 000 ℃ for 3 h,dicalcium silicate in the light-calcined products transforms into tricalcium silicate.The obtained high-silica dolomite clinker exhibits the optimal comprehensive properties with a bulk density of 3.22 g·cm^-3 and an apparent porosity of 7.4%.The results indicate that with the increasing clinker addition,the apparent porosity of the dry mixes increases,the mechanical properties decrease slightly,and the slag resistance first declines and then improves.When the addition of high-silica dolomite clinker is 30%,the MgO-CaO dry mixes retain favorable mechanical strength and slag resistance,which enables the engineering application of low-grade high-silica dolomite in tundishes.

Key words: high-silica dolomite, tundish, dry mix, slag resistance

摘要： 含有CaO的耐火材料具有脱硫和脱磷的作用,在MgO质中间包干式料中引入CaO有利于提高钢水洁净度。高硅白云石是常见的钙源,但其SiO₂含量较高,难以在耐火材料中应用。首先以高硅白云石原料,分别在700、800、900、1 000和1 100 ℃下轻烧3 h,再于1 600 ℃保温3 h重烧制得高硅白云石熟料。接着以最佳轻烧温度下再重烧的高硅白云石熟料(加入质量分数分别为0、15%、30%、45%和60%)和电熔镁砂为原料,制备MgO-CaO质中间包干式料,研究了轻烧温度对高硅白云石熟料性能的影响,以及高硅白云石熟料对该干式料的物相组成和性能的影响。结果表明:高硅白云石在1 000 ℃下保温3 h轻烧,然后经1 600 ℃重烧3 h的过程中,轻烧产物中的硅酸二钙在重烧过程中转变为硅酸三钙,制备的高硅白云石熟料体积密度和显气孔率分别为3.22 g·cm^-3和7.4%,性能最优;随着高硅白云石熟料加入量的增加,干式料的显气孔率升高,力学性能有所降低,抗渣侵蚀能力先降低后升高;当高硅白云石熟料加入量为30%(w)时,MgO-CaO质干式料具有较高的强度和抗渣性,可实现低品位高硅白云石在中间包中的应用。

关键词: 高硅白云石, 中间包, 干式料, 抗渣性