颗粒级配对低碳镁碳砖性能的影响

Effect of grain size distribution on performance of low carbon MgO-C brick

为提高低碳镁碳砖的抗热震性,选用电熔镁砂、石墨和铝硅合金为原料,PF-5405热塑性酚醛树脂为结合剂制备低碳镁碳砖,并根据Andreassen连续颗粒级配理论调整电熔镁砂颗粒配比,研究了q值(为0.3、0.4、0.5、0.6和0.7)对试样性能的影响。结果表明:1)当q为0.4~0.6时,生坯的密实度变化明显,且随q值增大而提高;当q<0.4或q>0.6时,生坯密实度变化较小;试样强度随显气孔率减小而线性增大。2)低碳镁碳砖试样热震后强度保持率随q值增大而线性提高,即随粗颗粒的增多,抗热震性提高。3)依据试样热震后产生裂纹的SEM照片建立了微观组织结构简易模型并通过对裂纹沿颗粒边界扩展贯穿的长度和颗粒剥出所需的能量分析得出,当粗颗粒较多时,虽然颗粒总比表面积减小,但单个粗颗粒与基质结合界面大,所需的断裂能大,因此裂纹较难扩展。

In order to improve the thermal shock resistance,the low carbon MgO-C bricks were prepared using fused magnesia,graphite and aluminum-silicon alloy as raw materials, PF-5405 thermoplastic phe- nolic resin as the binder,adjusting the grain size distribution of fused magnesia particles according to Andreassen continuous particle gradation theory. Effect of the q value （0.3,0.4,0.5,0.6 and 0.7） on proper- ties of the specimens was studied. The results show that： （1） when q is 0.4 -0.6, the compactness of green body changes obviously and increases with the q value increasing; when q 〈 0.4 or q 〉 0.6, the compactness of green body changes slightly;the strength of the specimens increases linearly with the ap- parent porosity decreasing;（2） after thermal shock,the strength retention ratio of the specimens increases linearly with the q value increasing, meaning that the thermal shock resistance increases with the coarse particles increasing; （3）according to the SEM photos of cracks after thermal shock,a simple model of mi- crostructure is established;by analyzing the length of crack propagating along the boundary of particles and the energy of particles to strip out, it can be concluded that when the coarse particles are more, al- though the total specific surface area of the particles decreases, the interface between the single coarse particle and the matrix is large, and the fracture energy required is large, so it is difficult for the crack to propagate.