Investigation of thermomechanical behavior of a work roll and of roll life in hot strip rolling
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I.
INTRODUCTION
IN hot strip rolling, a hot slab is passed through the roll gap several times, with its thickness being progressively reduced to achieve the final strip dimensions. The primary goals to be met by process design and control may vary depending upon the need of manufacturers and customers, but unprecedented considerations are being given to precise control of product quality, as well as to enhancing production economy, in most modern rolling practices. Product quality and production economy depend on the mechanical/thermal/metallurgical behaviors of the strip and also on those of the roll during rolling, and, therefore, in order to achieve successful process design and control, it is highly desirable to be capable of predicting the detailed aspects of these behaviors through sound process modeling. In the following article, state-of-the-art process modeling techniques related to hot strip rolling were summarized, with emphasis on those based on the finite-element or finite-difference method. A. Mechanical Behavior of the Strip In the past, various analytical and numerical techniques have been applied to predict the metal flow occurring in the strip in cold and hot rolling, to a degree far beyond the scope that the elementary rolling theories can cover. Among them, finite-element models were especially successful with regard to revealing the most detailed aspects of the metal flow characteristics in two- and three-dimensional rolling, either steady or nonsteady state. Examples are found in References 1 through 13 and in many more articles. Rigid-plastic (including rigid-viscoplastic) or elastic-plastic (including elastic-viscoplastic) materials were assumed.
C.G. SUN, Research Assistant, and S.M. HWANG, Professor, are with the Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea. C.S. YUN, formerly Research Assistant, Department of Mechanical Engineering, POSTECH, is Staff with Pohang Iron and Steel Co. Ltd., Pohang 790784, Korea. J.S. CHUNG, formerly Research Assistant, Department of Mechanical Engineering, POSTECH, is Researcher with Research Institute of Industrial Science and Technology, Pohang 790-784, Korea. Manuscript submitted December 27, 1996. METALLURGICAL AND MATERIALS TRANSACTIONS A
B. Thermal Behavior of the Strip and Thermal Behavior of the Roll During rolling, the work roll receives heat from the strip while the strip surface is chilled as it contacts the roll. The roll is also subject to surface cooling by water spray and by air. Prediction of the detailed thermal behavior of the roll-strip system is of great interest, for various reasons. The thermal behavior of the roll and of the strip are coupled through the roll-strip contact, necessitating the coupled analysis of heat transfer for the roll and strip. Sekimoto et al.,[14] Parke and Baker,[15] and Ohnuki and Nakajima[16] developed finite-difference models focusing on the prediction of the temperature distributions in the roll. Lahoti et al.[17] developed a finite-differ
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