Distribution Characteristics Of Fracture Strength Of Refractoires

Refractories are key materials in high temperature industry including steel making, cementand glass manufacturing. Because of its poor plasticity, refractories are sensitive to severalparameters including phase compositions and pores, and the random of the parameters leads togreat scatter of strength data. Therefore the values of strength as well as their distribution orprobability of failure have to be considered for design of metallurgical equipments. It issignificant to analyses the strength and its distribution of refractories for understanding themechanical properties of refractories and setting up the design rules of metallurgical equipments.In this paper, the methods of Weibull statistics and fractal are introduced into the distributionresearch of strength for refractories.The bending strengths of refractories including MgO-C, MgO-Cr₂O₃and high aluminabricks were measured. Weibull modulus of bending strength was estimated and discussedcombined with their apparent porosity, bulk density, chemical composition, phases. The fractureimages are threshold processed by image analysis technique, and then the fractal dimensions arecalculated by using Slit Island Method. The fracture mechanism is researched by comparing thevalue of fractal dimensions. The conclusions based on the results are listed as follows:The bending strength of refractories obeys Weibull distribution, their Weibull modulus mranges from3.8to10.7. It is helpful for refractories to reduce the discreteness of bendingstrength and improve the reliability of bending strength by increasing the density. The stress isdispersed by graphite for its flake structure in MgO-C refractories. The failure strength can beconcentrated by increasing the content of graphite. The pore can be removed by dissolving themagnesia-chrome spinel which is produced by fused magnesia and chromium oxide intopericlase for MgO-Cr₂O₃refractories. The solid solution is helpful for crystal growth. Thestrength and reliability of fused-rebonded MgO-Cr₂O₃refractories are higher than semi-rebondedMgO-Cr₂O₃refractories. The strength and its distribution are influenced by the glass phase forhigh alumina refractories. Combining degree of mullite can be improved by the uniformdistribution of glass phase. Weibull modulus m and characteristic strength σ0can be increased byenhance the degree of mullitization, and it is because of the reduction of defect and denserstructure of material.