Thermal Shock Resistance And Microscopic Stress Field Reconstruction Of Refractories

Refractories play an essential important role in a broad spectrum of hightemperature applications and are used in many strategic industries such as themetallurgy, building materials, non-ferrous metals, machineries, electricity. With thedevelopment of the industry technology, it has higher and higher demands on theperformance of refractory. Thermal shock resistance is one of the importantindicators for the evaluation of refractory performance. However, the evaluationtheories of thermal shock resistance of refractory are not unified, different theoriesof evaluation standards are different, and it can’t guide the actual production practiceeffectively at present. So it is very important and essential to research the thermalshock resistance of refractory. This experiment is devoted to the study of the types,distribution and transformation of the multiphase material interface stress and theessence of the thermal shock behavior of the thermal mismatched refractories whichis the supplementary to thermal shock stability theory in order to provide theoreticalsupport for the design and preparation of the refractory material. Corundum andmullite are used as raw materials. The thermal shock resistance of different thermalexpansion coefficient and different interface bonding composites is investigatedcombined with the application of Raman spectroscopy technology.Due to the different thermal expansion coefficients of corundum and mullite,two different complex refractory materials of different phase mismatch types areprepared, respectively. One of them is made of corundum as matrix phase andmullite as dispersion phase, the other one is made of mullite as matrix phase andcorundum as dispersion phase. The mullite is divided into the rich-aluminum mulliteand rich-silicon mullite whose activity and reaction behavior at high temperature aredifferent, so the interface bonding situations of the prepared composite made of thedifferent mullite are distinct too. Therefore, there are four different kinds of sampleby the same preparation process and conditions and experiment testing methods andconditions be prepared in this work to study their thermal shock behavior and thedistribution and change of the internal stress. The research results show that when the thermal expansion coefficient ofmatrix phase is greater than the dispersion phase’s, it will induce radial compressivestress at the phase interface which results in micro cracks in the matrix phase. Whenthe thermal expansion coefficient of matrix phase is less than the dispersion phase’s,it will induce interface tensile stress at the phase interface and cracks surroundedaround the dispersion phase. Solid phase reaction will occur under high temperaturein the heterogeneous material made of rich-silicon mullite and generate a smallamount of mullite at the interface and the interface combination is main flux mullitereaction layer. Solid phase reaction will not occur at high temperature inheterogeneous material made of rich-aluminum mullite and the interfacecombination is mainly generated by high temperature liquid phase, so the thermalshock performance is better than that of the latter. Thermal shock performance ofmaterials will decrease with the increasing the number of thermal shock cycles, butit is not a simple linear relationship. The internal stress of the sample is very smallbefore thermal shock which has no effect on the strength of the material. However, itwill produce a lot of stress after one thermal shock cycle along with the reducing ofthe material’ strength or rupturing. The non-uniformity of stress increases with theincrease of the numbers of thermal shock cycles and it result in cracking of materials,spalling and degradation until the final fracture.