二氧化锰加入量对含铝MgO-C砖高温抗折强度和显微结构的影响

Effect of MnO_2 Additions on the Hot Modulus of Rupture and Microstructure of MgO-Al-C Bricks

以97电熔镁砂和95鳞片状石墨为主要原料,添加金属铝粉和硅粉,以酚醛树脂为结合剂,制备了含铝镁碳砖,研究了二氧化锰加入量对试样高温抗折强度的影响,并借助X-射线衍射仪,扫描电镜等对试样物相和显微结构进行检测。结果表明:试样高温抗折强度在MnO2加入量0.5%时和未加入时相等,随着二氧化锰加入量的增大,试样高温抗折强度减小;在试样中加入二氧化锰,由于二氧化锰分解释放出氧气,抑制了铝粉的碳化和氮化,而直接氧化为氧化铝,部分转化为镁铝(锰铝)复合尖晶石,体积膨胀,结构致密;部分和基质中氧化钙、二氧化硅等杂质生成了低熔物,也促进了结构的致密化;但是随着二氧化锰量的增大,释放氧气过多,部分石墨被氧化,气孔率增大,并且生成的液相量增加,又使得试样高温抗折强度减小。

MgO-C refractories containing MnO2 and A1, Si additives were prepared using 97% fused magnesia, 95 % graphite flake as main starting materials and phenolic resin as a binder. The hot modulus of rupture （HMOR） of MgO-C refractories was determined at 1400 ℃for 0.5 h at carbon embedded conditions. The phase composition and microstructure were investigated by means of X-ray diffraction （XRD） （EDS）. , scanning electron microscopy （SEM） coupled with energy dispersive X-ray spectroscopy The results show addition of 0. 5% MnO2 had little influence on the HMOR of MgO-C refractories. Further increasing MnO2 amount, the HMOR decreased. This is because the added MnO2 would decompose to release oxygen, which inhibited the carbonization and nitridation of aluminum powder. Thus some aluminium powder was directly oxidized to form alumina or transform to complex spinel companying volume expansion and structure compactness. Some would react with impurities such as calcium oxide or silica to generate low melting substances, which also contributed to the compactness of the structure. However, with further increasing MnO2 amount, much oxygen would be released to lead to the oxidation of partial graphite. The porosity and liquid amount increased. So the HMOR inclined.