氮化硅加入量对镁质浇注料力学性能的影响

以镁砂为主要原料,以硅灰为结合剂,研究了不同氮化硅加入量对镁质浇注料的常温物理性能和高温力学性能的影响,用X射线衍射仪、扫描电镜等对浇注料的物相和显微结构等进行了分析.结果表明:经110℃,24h烘干的浇注料的常温抗压和抗折强度随着氮化硅加入量的增加而降低;经1 200℃,3 h烧结后的浇注料的常温抗压和抗折强度随着氮化硅加入量的增加先升高后降低,并在氮化硅加入量为3%(质量分数,下同)时达到极值点;经高温(1 500℃,3 h)烧结后的浇注料的常温抗压和抗折强度随着氮化硅加入量的增加而降低;烘干后的浇注料的高温(1 400℃)抗折强度在氮化硅加入量为3%时达到最大.在加热过程中氮化硅的作用包括两方面:一方面能部分氧化成二氧化硅,进而形成纤维状的镁橄榄石,增大浇注料的强度;另一方面氮化硅保留下来妨碍烧结,导致浇注料的强度降低.

EFFECTS OF Si_3N_4 ADDITION ON MECHANICAL PROPERTIES OF MgO-BASED CASTABLES

The effect of Si_3N_4 addition on the physical_properties at room temperature and hot mechanical properties of MgO-based castable refractory was investigated using magnisia as a main raw material and silica ash as a binder. The phases and the microstruc-ture were analyzed by using X-ray diffractometer and scanning electron microscopy. The results show that the cold compressive strength and rupture strength of the castables dried at 110 ℃ for 24 h decreases with the increase of Si_3N_4 addition. The cold com-pressive strength and rupture strength of the castables sintered at 1 200 ℃ for 3 h increases first then decreases with the increase of Si_3N_4 addition. The cold compressive strength and rupture strength of the castables sintered at 1 500 ℃ for 3 h decreases with the increase of Si_3N_4 addition , and the high temperature strength (at 1 400 ℃) reaches the maximum when the addition of Si_3N_4 is 3%. The addition of Si_3N_4 has two effects, namely, the partially oxidization of SiO_2 and the transformation of fibrous forsterite increased the strength and the residual Si_3N_4 hampered the sintering process, which can reduce the strength.