Original paper(Vol.46 No.1 pp.47)
Prediction of crack initiation life of converter shell based on stress analysis
Miyahara Mitsuo; Toyama Kazuo; Tokimasa Katsuyuki; Kurihara Shigeyuki
Abstract:In order to clarify effective measures to extend a life of converter shell in a steel production plant, the thermal fatigue crack initiation life was predicted by the strain range partitioning method.
A three-dimensional FEM model of the converter which is composed of a shell and bricks was established. An inelastic strain of the shell caused by a thermal cycle during operation was evaluated by an elastic-plastic-creep analysis. Since the thermal expansion of bricks is partly absorbed by a gap between bricks, the inelastic strain of the shell is affected by the gap size. Therefore, in the FEM model the hyperelastic element was used in order to describe the deformation behavior of bricks and gaps, and the stress analysis was conducted taking the gap size into consideration.
Based on the analytical results and creep-fatigue properties of a shell material, the crack initiation life of the shell was predicted. The relationship between the shell life and cooling conditions at the outer surface of the shell and the relationship between the shell life and the gap size were examined. The following results were obtained.
(1) The predicted shell life corresponded well with that in the actual converter.
(2) It is possible to extend the shell life by decreasing the maximum shell temperature which can be attained by increasing the film coefficient of cooling at the outer surface of the shell.
(3) It is also possible to extend the shell life by increasing the gap size. Furthermore, the larger the gap size is, the decrease of shell temperature becomes more effective for the shell life extension.
Key Words:creep-fatigue, life prediction, converter, stress analysis, strain range partitioning method