Modeling Research Technique of Nonmetallic Inclusions Distribution in Liquid Steel during Its Flow through the Tundish Water Model

Abstract

This study shows research results of behaviors of nonmetallic inclusions (NMIs) in a tundish represented by water model. The object under investigation is a two‐strand trough‐type continuous casting tundish operating in one of the Polish steel plants. Hollow glass microspheres with diameters ranging from 10 to 140 μm are used for testing, which represents the NMIs. The distribution process of microspheres is investigated; the qualitative analysis (visualization) and quantitative analysis (using a laser particle counter) of microsphere distribution (movement) are performed. Based on the obtained results, it is found that the analyzed tundish is not of optimal design, in terms of removing small NMIs, as they are conducted in a stream of liquid flowing at the bottom of the tundish, moving directly into nozzles of the tundish. Their movement is caused by the shaped liquid‐flow phenomena in the tundish working space. The test results help to validate a numerical model, which can be used in further studies to redesign the working space of the tundish. The positive result of verification facilitates to obtain a tool for implementing flow optimization in terms of receiving high metallurgical purity of slabs.

Evolution of the Numerical Model Describing the Distribution of Non-Metallic Inclusions in the Tundish

“…The tundish is one of the final elements of the technological line, in which appropriate conditions prevail for refining steel to clear it of inclusions. Therefore, aside from research on refining in the ladle, investigations are conducted to identify the hydrodynamic conditions prevailing in the tundish [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], and also to determine the behavior of NMIs in the tundish [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”

“…Meanwhile, for determining the similarity of particle motion, Stoke’s law and the Froud (Fr), Reynolds (Re), and Archimedes (Ar) criterial numbers are used. This enables the selection of the type of NMI-simulating microparticles [ 25 , 26 , 27 ] to be made appropriately for given testing conditions. The investigations reported in studies [ 13 , 14 , 15 , 17 , 19 , 21 , 22 , 23 , 24 ] chiefly concern the issues of removing NMIs and the analysis of this phenomenon.…”

“…NMIs in liquid steel, modeled in CFD computations, are idealized spherical forms defined by their dimensions and densities. The real range of nonmetallic inclusion density variation assumed in computation [ 12 , 13 , 18 , 25 , 29 , 30 , 31 ] results from the fact that the aluminum oxide inclusions form clusters of an expanded structure and a variable Al 2 O 3 fraction relative to the bonding metallic phase. In the majority of those studies, the boundary conditions reflect the entrance of NMIs (and their quantity and size) to the tundish with liquid steel through the surface corresponding to the inlet.…”

“…The boundary conditions for simulating the processes of NMI removal at the interfaces (liquid steel–liquid slag or liquid steel–refractory lining), available in commercial computation codes, are insufficient. In many numerical solutions, it is assumed that with the collision of NMIs with the liquid steel–tundish lining interface, the particle rebounds elastically from the lining wall [ 25 , 30 ]. This precludes a possible adhesion of NMIs to the lining and a permanent bond with the tundish lining material.…”

Physical Modeling Evaluation on Refining Effects of Ladle with Different Purging Plug Designs

“…The apparatus was established, referring to previous research, which was applied for measuring the inclusion removal rate (Figure ). According to Equation , and polystyrene (PS) particles of diameter 125–160 are used to simulate actual inclusions of diameter ≈50 . The properties of the water and PS particles are shown in Table .…”