Time-Series Analysis Technologies Applied to the Study of Carbon Element Distribution Along Casting Direction in Continu
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UCTION
CARBON element distribution along the casting direction in continuous-casting billet means the change of carbon mass fraction along a certain direction of billet in the study. Segregation in continuous-casting billet means nonuniform distribution of element, and there are two kinds of segregation, i.e., macrosegregation and microsegregation. Macrosegregation is very important defect for the quality of continuous-casting billet. Over years, many works have been done for the macrosegregation in a transverse cross section of continuous-casting billet (perpendicular to casting direction).[1,2] Except for the macrosegregation perpendicular to the casting direction, element distribution along the casting direction is always obviously nonuniform, and this phenomenon also has great influence on the quality ZIBING HOU, CHENGCHUAN WU, and CHAO CHEN, Doctor Students, and GUOGUANG CHENG, Professor, are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] Manuscript submitted June 15, 2012. Article published online October 3, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
of continuous-casting billet and final product.[3–7] However, there are only a few special investigations[7,8] for this element distribution in continuous-casting billet. The solidification process in continuous-casting billet involves many complicated phenomena, such as heat transfer, mass transfer, momentum transfer, and phase transformation. Moreover, it also presents obvious indeterminacy and nonlinear characteristics, and it is very difficult to describe the state change completely during solidification process using deterministic mathematic models.[9–11] In the actual research, only the time series of one or some variables that are changed with time have been always obtained, such as the surface temperature of the billet during solidification and element distributions at different positions. Time series, which is a special concept in mathematics, means a series of data points that were formed with the lapse of the time as to a certain variable.[12] How to understand the essential characteristics and dynamic information of the nonlinear system by these time series is a very important issue. And this nonlinear system, the solidification process of continuous-casting billet, has direct relationship with the quality of billet and final steel products.[10,11] Therefore, it is very valuable to investigate the characteristics of the system about the solidification VOLUME 43B, DECEMBER 2012—1517
EXPERIMENTAL AND PROCEDURE
A. Application of the OPA Technology In order to obtain the carbon element distributions of billet along casting direction at different positions, then the OPA was used for scanning the selected zone. The OPA is a new analytical method to determine the 1518—VOLUME 43B, DECEMBER 2012
Sampling Position
Inner Radius Side Casting Direction Left Side
Right Side Outer Radius Side
(a) Sampling position of continuous-casting billet
Centerli
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