Mathematical Analysis of the Dynamic Effects on the Deposition of Alumina Inclusions inside the Upper Tundish Nozzle

Abstract

Nozzle clogging is still a standing problem in the continuous casting of steel since the deposition of alumina inclusions inside the Upper Tundish Nozzle (UTN) affects the productivity and the product quality. The present fundamental work studies the effects of inertial, gravitational, buoyant, pressure gradient, and Saffman forces on the deposited inclusion trajectories at the typical adhesion zone inside the UTN, using analytical and numerical techniques. For this, a mathematical model was developed considering the Navier-Stokes equations, the standard k-ε model, and the Lagrangian discrete phase model for a coupled system including the tundish, the UTN, the slide gate, the SEN, and the mould. The results show that the highest inclusion deposition rate is just below a low static pressure zone. At the low static pressure zone the pressure gradient force becomes important, attracting the inclusions to the nozzle wall, and once the inclusions leave this zone, this force does not promote a significant inclusion radial movement. In addition, at the highest deposition zone, the effects of the gravitational and buoyant forces do not promote a significant inclusion radial movement since these are aligned with the direction of the flow stream lines. In contrast, the Saffman force shows an important effect on the deposited inclusions, slowing down the inclusions in the vertical axis and increasing their radial movement.

A Study on the Nonmetallic Inclusion Motions in a Swirling Flow Submerged Entry Nozzle in a New Cylindrical Tundish Design

“…In order to understand the deposition location and mechanism, computational fluid dynamics (CFD) studies have been carried out to investigate the inclusion transport in turbulent steel flows and its deposition on the SEN walls. [9][10][11][12][13][14][15][16][17] Deposition rates of inclusions on the SEN wall were predicted by using an Eulerian deposition model, which considered the transport of inclusions in the turbulent flow boundary layer as well as the turbophoresis effect. [16,17] Finally, inclusions move into the mold accompanying steel flows, where the solidification of molten steel happens.…”

Decrease of Nozzle Clogging through Fluid Flow Control

“…This phenomenon produces an inconsistent flow and temperature variations, steel level fluctuations in the mold, impairment of steel quality, and the steel casting's abrupt interruption. Clogging starts when solid compounds, mainly steel skull, and non-metallic inclusions, are non-uniformly deposited at the entry nozzle inner wall at some typical preferential zones characterized for neighboring dead flow conditions [1][2][3][4][5]. These inclusions have as primary sources: (1) The reaction between the dissolved oxygen with the deoxidizers [6][7][8][9]; (2) re-oxidation in the tundish or the nozzle [10,11]; and (3) the entrainment of slag or refractory particles [11][12][13][14].…”

Removal Mechanism of Microscale Non-Metallic Inclusions in a Tundish with Multi-Hole-Double-Baffles

“…Because steel grades require an increasingly high degree of purity, particularly for micro-inclusions with sizes of 1 µm to 50 µm, the tundish must be able to remove the micro-inclusions in the steel [19][20][21][22][23]. Unfortunately, the currently used tundishes and in particular the tundish used for high casting speed caster, cannot remove the micro-inclusions effectively [24][25][26][27].…”