Thermal stress fracture of refractory lining components: Part III. Analysis of Fracture
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I.
INTRODUCTION
THEprincipal objective when heating or cooling industrial linings through a prescribed temperature range is to do so as rapidly as possible without producing nonlinear temperature fields within the refractory components that will cause fracture. In previous work,l'2 a thermoelastic model was used to develop a theoretical resistance-to-fracture-initiation parameter useful for the design and selection of refractory components that reflected the industrial goal. However, the thermal stress fracture of refractory components is not always avoided in practice, and the nature of fracture can significantly affect the rate of refractory wear. This work presents a theoretical analysis of fracture behavior of refractory components based on a two-dimensional constant heating rate thermoelastic model. Aspects of fracture that are directly related to refractory wear are location of fracture initiation, orientation of cracking, and extent of crack propagation. Components with cracks running perpendicular to the heated face are expected to be more stable than those with cracks parallel to the heated face, in that sudden catastrophic loss of significant portions of the lining is less likely in the former case. When cracking occurs parallel to the hot face, the distance of the crack plane from the heated face is a direct measure of potential loss on spalling, or component separation. Most refractory components possess good crack arrest capability, which means that crack propagation often stops prior to the crack plane completely traversing a section of the component causing separation. From the refractory wear standpoint, resistance to crack propagation is another important consideration in the selection of refractory components. The industrial lining problem is particularly suitable for a theoretical approach since it is extremely difficult to monitor the thermal fields and fracture behavior of lining compo-
F. BRADLEY is Assistant Professor, Department of Metallurgical and Mineral Engineering, University of Wisconsin-Madison, Madison, WI 53706. A. C. D. CHAKLADER and A. MITCHELL are Professors, Department of Metallurgy, University of British Columbia, Vancouver, BC, Canada, V6T lW5. Manuscript submitted April 28, 1986. METALLURGICALTRANSACTIONS B
nents during service. In many applications both severe thermal and chemical environments are encountered during the various stages of processing. The hot face of the lining components is often covered by slag or other coatings which form during processing, obscuring cracks which may have initiated at or propagated to the surface. Regardless of the condition of the hot face, cracks which run parallel to the hot face in the interior of the brick are not detectable during or after service. A lining can be dismantled and examined after service to document the effects of operating practice on fracture behavior, but such an approach does not yield information regarding the temperature field responsible for fracture. In this work, a two-dimensional constant heating rate therm
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