| Summary: | 碩士 === 國立中正大學 === 機械系 === 91 === Abstract
In general, the defects appear on the surface and two sides of strip after rolling process. These defects not only affect surface property, but also the mechanical property of strip. In order to maintain the quality of products, both two sides of steel strip should be cut to get rid of defect. It will raise rolling cost drastically.
The hot rolling process includes rough stand and finish stand. Each step contains multi-pass rolling, such as edging rolling and horizontal rolling. After first edging rolling, the double bulge shape formed on both ends of the cross section. In addition to horizontal rolling, the edging defects then form in the area of double bulge or around the distance of 60mm from the slab edge. According to experimental results from China Steel Corporation, it is impossible to obtain a defect free strip after rolling process. Thus, understanding the causes of defects formation is essential to reduce the cost of rolling process.
This study investigates deformation of SUS304 stainless steel during rolling process using finite element soft name ABAQUS. The initial conditions, boundary conditions are obtained form China Steel Corporation, and the constitutive equation was obtained from flow curves, which were obtained from Gleeble forging test. A 3-D rolling model was used to simulate the deformation and the existence of the edging defects during rolling process. The position of the edging defects was determined based on maximum shear stress yielding criterion.
The results depict that the cause of defect formation mainly was attributed to edging rolling. Furthermore, the defects increase with increasing rolling passes at same conditions. It implies that decreasing or eliminating the rolling passes are effective on reducing the defects, which is consistence with the experimental results from China Steel Corporation. The finite element method used in this study is proved to be an effective tool to predict the defects site during rolling process.
Key words：slab edging defect, slab rolling, double bulge, SUS304 stainless steel, finite element, ABAQUS, Gleeble forging test, flow curves
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