Development and Application of Dynamic Soft-reduction Control Model to Slab Continuous Casting Process

Abstract

the effect of casting history during slab cooling process. Considering the current actual casting speed, the effective casting speed is defined based on the quantity of slicing units and the average casting speed at the secondary cooling zone. The definition can fully reflect the casting history (calculated from the beginning of the slicing unit) of each slicing unit and its effect on the total heat transfer of the caster at the secondary cooling zone. The schematic of method for calculating the effective casting speed is shown in Fig. 2. In the current calculation cycle, the secondary cooling zone totally contains N slicing units (corresponding serial numbers are j, jϩ1 · · · jϩNϪ2 and jϩNϪ1). The slicing unit generates at the meniscus and moves toward the out gate of the caster with certain casting speed.The average casting speed of slice unit j in m/s can be represented by: where L is the casting distance from meniscus in m; t and (tϩDt) are the last and the current calculation period respectively in second; dZm is the moving distance of slice unit j during the current calculation period Dt in m, which is calculated by:. .(7)Where V c is the actual casting speed in m/s. The average casting speed of all the slice units at the secondary cooling zone i can be obtained by Eq. (6). And then the average casting speed of the secondary cooling zone i can be calculated by:..... (8) where V z,i is the total average casting speed of the secondary cooling zone in m/s; N is the number of the slice units.A reasonable fractional factor is necessarily introduced to describe the relationship between the collectivity average casting speed, which can be calculated from the average casting speed contained in each unit in all sections, and the current actual speed:........... (9) where V eff,i is the effective casting speed of secondary cooling zone i in m/s; C frac (i) is the fractional factor of secondary cooling zone i; and V c is the actual casting speed in m/s. Taking into account of the remarkable differences of the distance from the meniscus to the individual secondary cooling partition, and the time that the slicing units with new operating conditions need to move to the individual secondary cooling partition, the value of cooling fractional factor must acclimatize to this technical character. For example, the front parts of secondary cooling zone are closer to the meniscus than other parts, the actual casting speed has more effects on the effective casting speed, and thus the value of fractional factor should be smaller. Contrarily, for the secondary cooling partition which have relatively longer distances to the meniscus, the actual casting speed contribute less to the effective casting speed, the value of corresponding fractional factor should be an appropriate larger number.Besides considering the history of casting speed, the concept of comparing the target surface temperature to modify the flow rate of cooling water is introduced in the control algorithms. In other words, it is to compare and analyze the theoretica...

Analysis and Application of Soft Reduction Amount for Bloom Continuous Casting Process

“…[1][2][3][4][5][6][7][8][9][10] The principle of SR is to impose a reasonable reduction rate/ amount on the solidification end of the strand for compensating liquid core shrinkage and preventing the soluteenriched liquid flowing toward the center of the strand without creating internal cracks. 1,2,4) In bloom SR process, the reduction is usually executed by 6-10 withdrawal units which are arranged in the air cooling zone with intervals of 1.0-3.5 m. Therefore the reduction interface is discontinuous, and the SR amount is generally selected as the primary control parameter during the bloom SR process.…”

Research on the On‐Line Simulation of a Three‐Dimensional Temperature Field Model of Slab Continuous Casting

“…It can be seen that basing on the simulation of the three‐dimensional temperature field the temperature in the width direction of the slab may be uniformed by the dynamic secondary cooling water model and a regular shape of the solidification end may be obtained which is the key factor for achieving good results of soft‐reduction technology . So, the dynamic secondary cooling water model and dynamic soft‐reduction model are successfully used to modify the original model in a domestic steel mill, which is the two‐dimensional temperature field version.…”

Real‐Time Heat Transfer Model Based on Distributed Thermophysical Property Calculation for the Continuous Casting Process

“…Although the offline heat transfer model could predict solidification ends with different casting conditions, it is difficult to real‐time predict the solidification end of strand in industry production process due to the huge calculation cost, especially under conditions of the unsteady continuous casting. Therefore, many real‐time heat transfer models were developed to calculate the solidification end efficiently . Voest‐Alpine Industieanlaenbau(VAI) developed a real‐time cooling control and heat transfer calculation model, named Dynacs @ (Dynamic Strand Cooling Management System), which could determine the solidification end with the specific condition of steel grade, casting speed, and casting temperature.…”

“…Therefore, many real-time heat transfer models were developed to calculate the solidification end efficiently. [24][25][26][27][28] Voest-Alpine Industieanlaenbau(VAI) [29] developed a real-time cooling control and heat transfer calculation model, named [25] proposed real-time model-based system to control secondary cooling water sprays and provide the predicted solidification end in continuous casting of thin steel slabs. Chen et al [24] developed a one-dimensional heat transfer model to control the fluctuation of operating parameters promptly and applied the model to dynamic soft reduction.…”

“…[24][25][26][27][28] Voest-Alpine Industieanlaenbau(VAI) [29] developed a real-time cooling control and heat transfer calculation model, named [25] proposed real-time model-based system to control secondary cooling water sprays and provide the predicted solidification end in continuous casting of thin steel slabs. Chen et al [24] developed a one-dimensional heat transfer model to control the fluctuation of operating parameters promptly and applied the model to dynamic soft reduction. Xie et al [28] presented a real-time heat transfer model for controlling the continuous casting of billets and adapted the finite volume method (FVM) and the alternating direction implicit (ADI) method to create an efficient numerical solution algorithm for accelerating the calculation of the heat transfer model.…”