Wide-thick Slab Research Articles

Investigation of Solidification Heat Transfer in Slab Continuous Casting Process Based on Different Roll Contact Calculation Methods.

The heat transfer of a slab is significantly influenced by roll contact during the continuous casting process. The influence of roll contact calculation methods on the predicted heat transfer results has not been previously investigated. In this work, the non-uniform solidification of the wide-thick slab was studied with a 2D heat transfer model using real roll contact method (R. method) and equivalent roll contact method (E. method). The predicted slab surface temperature and shell thickness were verified with the measured results of the infrared camera and nail shooting experiments, respectively. Then, the predicted heat transfer results (including the slab surface temperature, mushy region length, and solidification end position) for the wide-thick slab with different thicknesses and different casting speeds were calculated using the E. method and R. method, and the influence of these two roll contact methods on the predicted heat transfer results was discussed for the first time. The results show that both these two roll contact methods could be applied to accurately predict the slab surface temperature without considering the transient temperature dips in the roll-slab contact regions. However, the deviation of the predicted mushy region length and solidification end position using the E. method are obvious. Compared with the R. method, the predicted mushy region length obtained using the E. method is larger and the solidification end obviously subsequently moves along the casting direction.

Deep learning-based prediction framework of temperature control time for wide-thick slab hot rolling production

Deep learning-based prediction framework of temperature control time for wide-thick slab hot rolling production

Design of Process and Equipment for Wide-Thick Slab CSC-Roll Reduction and Study of the Resulting Surface Crack Risk

Design of Process and Equipment for Wide-Thick Slab CSC-Roll Reduction and Study of the Resulting Surface Crack Risk

A new method for determination of the theoretical reduction amount for wide-thick slab during the mechanical reduction process

Mechanical soft reduction (MSR) is an effective method for elimination of the centerline segregation and porosity of the continuous casting steel slab, and the reduction amount is a key parameter that determines whether the MSR could be applied successfully. In the present work, a 2D heat transfer model was developed for predicting the non-uniform solidification of the wide-thick slab. The measured shell thickness by nail shooting experiment and the measured slab surface temperature by infrared camera were applied to validate the 2D heat transfer model. A new calculation method of theoretical reduction amount that could consider the influence of non-uniform solidification of the wide-thick slab was then derived. Based on the predicted temperature field by the 2D heat transfer model and the newly-proposed calculation method, the required theoretical reduction amount and reduction gradient/rate for the wide-thick slab were calculated and discussed. The difference between the newly-proposed method and the previous method, the influence of the casting speed and slab thickness on the required theoretical reduction amount and reduction gradient/rate were also investigated.

A 3D model coupled inverse algorithm for the non-uniform thermal behavior of a continuous casting mold

A 3D finite element model of a copper plate in a continuous casting mold, including arc-shaped water slots and a nickel layer with increasing thickness, was built to reflect the flexible and non-uniform thermal behavior of the mold during wide-thick slab continuous casting. The inverse algorithm was applied to calculate the heat flux from temperatures measured by thermocouples, which were buried in various locations inside the mold. The model can reflect the real thermal behavior of the mold wall and further evaluate the effects of the nickel layer and water slots on heat transfer of mold. Along the casting direction, the temperature peaks appear approximately 100 mm below the meniscus. The temperature gradient in the nickel layer in the thickness direction is larger than that in the copper plate. The average temperature at the root of deepwater slots is higher than that of shallow ones by 10 °C. The model can further improve casting parameters and operations.

Deformation Behavior of Internal Porosity in Continuous Casting Wide-Thick Slab during Heavy Reduction

Heavy reduction (HR) is a novel technology that could effectively improve the internal porosities and other internal quality problems in continuously cast steel, during which a large reduction deformation is implemented at and after the strand solidification end. In the present paper, non-uniform solidification of the wide-thick slab was calculated with a two-dimensional (2D) heat transfer model. Based on the predicted temperature distribution at the solidification end of the casting strand, a three-dimensional (3D) thermal-mechanical coupled model was developed for investigating the deformation behavior of the internal porosities in wide-thick slab during HR. An Arrhenius-type constitutive model for the studied steel grade was derived based on the measured true stress-strain with single-pass thermosimulation compression experiments and applied to the 3D thermal-mechanical coupled model for improving the calculation accuracy. With the developed 3D thermal-mechanical coupled model, deformation behavior of the two artificial porosities located at the slab center of 1/2 width and 1/8 width during HR was investigated under different condition of HR deformation, HR start position, and HR reduction mode. Based on the calculated porosity closure degree (ηs) and the corresponding equivalent strain (εeq) under different HR conditions, a prediction model that describes the quantitative relationship between ηs and εeq was derived for directly and accurately evaluating the process effect of HR on improving the internal porosities in wide-thick slab.

Numerical Simulation of Bulging Deformation for Wide-Thick Slab Under Uneven Cooling Conditions

In the present work, the bulging deformation of a wide-thick slab under uneven cooling conditions was studied using finite element method. The non-uniform solidification was first calculated using a 2D heat transfer model. The thermal material properties were derived based on a microsegregation model, and the water flux distribution was measured and applied to calculate the cooling boundary conditions. Based on the solidification results, a 3D bulging model was established. The 2D heat transfer model was verified by the measured shell thickness and the slab surface temperature, and the 3D bulging model was verified by the calculated maximum bulging deflections using formulas. The bulging deformation behavior of the wide-thick slab under uneven cooling condition was then determined, and the effect of uneven solidification, casting speed, and roll misalignment were investigated.

Uneven Solidification during Wide-thick Slab Continuous Casting Process and its Influence on Soft Reduction Zone

A two-dimensional heat transfer model was developed to analyze the uneven solidification, particularly the shape of solidification end in wide-thick slab continuous casting process. In order to ensure the accuracy of simulation, material properties of peritectic steel were calculated by weighted averaging of phase fractions, and the boundary conditions were obtained by realistic water flux distribution on the slab transverse surface. The model was verified by nail shooting results at different locations of strand, and the absolute value of relative error was found to be no more than 2.12%. According to the simulation results, the liquid core around 1/8 location of slab width increased after the water flux was decreased around the slab corner to reduce transverse corner cracks. The soft reduction (SR) zone was optimized to reduce macro-segregation both at the slab center and 1/8th location. The plant results showed that the inner quality of wide-thick slab was significantly improved in the whole transverse section with the optimized SR zone parameters.

Effect of transverse distribution of secondary cooling water on corner cracks in wide thick slab continuous casting process

In the present work, a two-dimensional heat transfer model to describe the thermal behaviour of the wide thick slab during continuous casting process was developed, in which the boundary conditions for secondary cooling zone were calculated from the realistic water flux along the transverse surface of slab. The accuracy of the model calculation results were verified and calibrated by infrared thermography and nail shooting results. Furthermore, the slab temperature distribution under typical casting conditions were investigated numerically, and based on the hot ductility of microalloyed steel, the different arrangements of nozzles were optimized and designed to reduce the slab transverse corner cracks. The plant results showed that the defect rate of rolled plate corner and edge cracks were reduced from 12·6 to 3·5% with the optimised nozzles configurations.

Metallic slit waveguide for dispersion-free low-loss terahertz signal transmission

Transmission characteristics of a metallic waveguide are presented combining negligible dispersion, very low attenuation, and two-dimensional mode confinement. The waveguide is fabricated by sawing a 270μm wide slit through a 40mm wide and 300μm thick silicon slab and subsequent metalization of all faces. Single-mode terahertz pulses propagating through the slit are excited at one end of the waveguide using a photoconductive antenna array and detected with a freely positionable photoconductive probe tip. Low-loss propagation with negligible group velocity dispersion is observed in the 0.1–1.0THz frequency range. Compared to former approaches considerably stronger mode confinement is achieved.