Si_2N_2O对MgO-MA不烧砖性能的影响

Effect of Si_2N_2O on properties of MgO-MA unfired bricks

为了获得具有优良性能的RH炉用MgO-MA不烧砖,以5～3、3～1和<1 mm的电熔镁砂为骨料,<0. 088 mm的电熔镁砂粉、<0. 044 mm的镁铝尖晶石粉、金属铝粉、硅粉为基质,实验室合成的氧氮化硅(Si_2N_2O)为外加剂,热固性酚醛树脂为结合剂,制备了MgO-MA不烧砖。研究了外加剂Si_2N_2O加入量(w)分别为0、1%、2%、3%和4%时对MgO-MA不烧砖物理性能和显微结构的影响。结果表明:1)经200℃烘24 h后的试样,随着Si_2N_2O加入量增多,影响了颗粒与基质之间结合的紧密程度,导致结构变疏松,使得试样体积密度、抗折强度和耐压强度逐渐降低,热震后强度保持率先升高后降低。2)经1 550℃保温3 h热处理后的试样,因加入适量的Si_2N_2O分解生成的SiO2与MgO反应生成了适量的镁橄榄石(Mg2SiO4),提高了试样的抗折强度和耐压强度; Si_2N_2O加入量过多又会使试样内部产生微裂纹而导致性能下降。综合来看,Si_2N_2O的最佳加入量为1%～2%(w)。

In order to improve the performance,MgO-MA unfired bricks for RH furnace were prepared using fused magnesia(5-3,3-1and<1mm)as aggregates,fused magnesia fines(<0.088mm),magnesi-umaluminate spinel powder(<0.044mm),aluminum powder and silicon powder as the matrix,Si2N2O as the additive,and thermo-setting phenolic resin as the binder.The effects of the addition of Si2N20(0,1%,2%,3%and4%)on the physical properties and microstructure of MgO-MA bricks were studied.The results show that for the specimen dried at200℃for24h,the increasing addition of Si2N20affects the tightness of the binding between the particles and the matrix,resulting in the loose structure,thus the bulk den-sity,flexural strength and compressive strength gradually decrease and the residual strength ratio after thermal shock increases first and then decreases.After the heat treatment at1500℃for3h,the added ap-propriate amount of Si2N20decomposes and produces Si02,which reacts with MgO to generate the ap-propriate amount of forsterite(Mg2Si04),to improve the flexural strength and compressive strength.But the excessive Si2N20results in the formation of microcracks in the specimen,decreasing the performance.So,the optimum addition of Si2N20is1%-2%.