Correlation of microstructure and thermal-fatigue properties of centrifugally cast high-speed steel rolls |
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Authors: | Chang Kyu Kim Jong Il Park Jae Hwa Ryu Sunghak Lee |
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Affiliation: | (1) the Center for Advanced Aerospace Materials, Pohang University of Science and Technology, 790-784 Pohang, Korea;(2) Hot Rolling Department, Pohang Iron and Steel Co., Ltd., 790-785 Pohang, Korea;(3) Graduate School of Iron and Steel Technology, Pohang University of Science and Technology, Korea;(4) Center for Advanced Aerospace Materials and Department of Materials Science and Engineering, Pohang University Science and Technology, Korea |
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Abstract: | This is a study of thermal-fatigue properties in centrifugally cast high-speed steel (HSS) rolls. The thermal-fatigue mechanism
was investigated, with special focus on the roll microstructure and the increase in tensile stress which led the specimens
to fracture when it reached the tensile strength. The thermal-fatigue test results indicated that the thermal-fatigue life
decreased with increasing maximum temperature of the thermal-fatigue cycle. The results were then interpreted based on the
amount of carbides and the cyclic-softening phenomenon associated with the exposed time to elevated temperatures. The coarse
intercellular carbides on the specimen surface acted as fatigue-crack initiation sites as they cleaved at a low stress level
to form cracks. The roll having the lowest matrix hardness and the smallest amount of intercellular carbides, thus, showed
better thermal fatigue properties than the other rolls. For the improvement of the thermal-fatigue properties of the rolls,
this study suggests a homogeneous distribution of carbides by reducing the carbide segregation formed along the solidification
cell boundary and by optimizing the roll compositions. |
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