Si_3N_4对镁质浇注料抗渣性能的影响

Effect of Si_3N_4 on slag resistance of magnesia based castable

以95烧结镁砂为主要原料,以SiO2微粉为结合剂,在配料的细粉部分分别以0、3%、4%、5%的β-Si3N4细粉替代等量的镁砂细粉,搅拌均匀后浇注成氮化硅含量不同的镁质坩埚试样。选用宝钢中间包渣,采用静态坩埚法,在1550℃3h条件下对这些坩埚试样进行了抗渣试验。试验结果表明:加入Si3N4可以明显改善镁质浇注料的抗渣性能,并且随着Si3N4加入量的增加,试样的抗渣性能提高;在含氮化硅的镁质浇注料表面,由于Si3N4被氧化为SiO2而形成了致密烧结层,能阻止渣的进一步渗透;在加入Si3N4的镁质浇注料试样内部深处,由于氧分压非常低,Si3N4稳定存在;由于Si3N4在还原气氛下难以烧结,造成镁质浇注料内部结构疏松。

The magnesia based curcible specimens with different Si3N4 contents were casted using sintered magnesite （w（MgO） =95% ） as starting materiaI,SiO2 micro-powder as binder,0,3% ,4% and 5%β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550 ℃ for 3 h using Baosteel tundish slag and static crucible method. The result indicates that： introducing Si3N4 could obviously improve the slag resistance of MgO based castable,which increased with the increase of Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable,the partial -pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere,Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.