Study On Evaluation Method Of Thermal Shock Resistance Of Mullite Castable

Thermal shock resistance is one of the important performance properties of refractory castables.The quantitative evaluation of thermal shock resistance is of great significance in practical production applications.In the process of thermal shock,the irregularly distributed thermal stress inside the refractory castable changes dynamically,causing the structure and performance of the material to change to varying degrees.The current standard of thermal shock resistance evaluation uses a single performance change to evaluate the thermal shock resistance of the material.There is a large deviation,which can only be used to explain its thermal shock resistance.Therefore,in order to compare and analyze different quantitative evaluation methods of thermal shock resistance,and explain the thermal shock damage of refractory castables from the perspective of crack development,this article takes mullite castable as the research object,combined with the wedge splitting experiment and the thermal stress damage factor to theoretically analyze the thermal shock damage of the refractory castable,and comparatively analyzes three quantitative evaluation methods of thermal shock resistance—residual modulus of elasticity ratio,residual module of rupture ratio and residual ultrasonic wave velocity ratio,comprehensively explain the thermal shock damage form of mullite castables,with a view to providing theoretical basis and guidance for the quantification of the thermal shock resistance of refractory castablesIn the research of the subject,the evaluation method of the thermal shock resistance of the casting material was studied by changing the combination system,the addition amount of steel fiber and ZrO2 fine powder.The main research contents are as follows(1)The addition of steel fiber and ZrO2 fine powder both reduce the bonding strength of the castable after heat treatment;as the addition of both continues to increase,its toughening effect on the material can improve the thermal shock resistance of the material to a certain extent;In the thermal shock damage analysis of castables bonded with p-Al2O3,the addition of an appropriate amount of steel fiber(?1.5wt%)and ZrO2 fine powder(<3wt%)can improve its residual module of rupture ratio,but its residual modulus of elasticity ratio and residual ultrasonic wave velocity ratio decreased obviously after adding steel fiber and ZrO2 fine powder.In the thermal shock damage analysis of pure aluminate cement combined with castable,the three residual performance ratio changed roughly consistently as the addition of steel fiber and ZrO2 fine powder(2)The density of mullite castables decreases after thermal shock,and different performances fluctuate to different degrees.Its structural damage manifests as the increasing shape,number,and size of defects(cracks,pores,etc.).Through the analysis of the different changes of R'" and R"",it can be obtained that the material is resistant to new crack initiation and primary microstructure under thermal stress The ability to generate elastic strain(R'")and the ability to resist crack growth(R"")during crack propagation.A single thermal shock resistance evaluation method can only describe the thermal shock damage of the castables unilaterally.During the thermal shock procedure,the quantitative evaluation results of different thermal shock resistance can be obtained by the number of defects(residual modulus of elasticity ratio),the maximum defect size(residual module of rupture ratio)and the structural coherence change(residual ultrasonic wave velocity ratio).The comprehensive use of the thermal shock resistance evaluation method can more fully reflect the thermal shock damage of the material(3)The correlation between the post-peak area and the fracture toughness obtained by the wedge splitting test has been proved;Among the three methods of quantitative evaluation of thermal shock resistance,residual modulus of elasticity ratio and residual ultrasonic wave velocity ratio have a greater correlation;The correlation between the ability to generate elastic strain(R'")and residual modulus of elasticity ratio and residual ultrasonic wave velocity ratio is greater,and the ability to resist crack growth(R"")and residual module of rupture ratio are greater.