A New Inert Gas Delivery Design for Improved Shielding of Ladle Shroud–Collector Nozzle (LS–CN) Assembly: Modeling, Design, and Industrial‐Scale Validations

Abstract

Argon injection in ladle shrouds is customarily practiced during the teeming of liquid steel from ladle to tundish to minimize air ingression and thereby restrict atmospheric oxidation of steel melt. Despite such practices, nitrogen pickup results in the tundish, implying inadequate shielding of ladle shroud-collector nozzle (LS-CN) joint. Accordingly, the efficacy of different argon injection designs in shrouds is evaluated in the present study, and thereby, a novel argon injection arrangement, embodying a twin, tangential gas discharge system, developed as a curative step to ensure maximum inertization of the LS-CN assembly. Numerical prediction of argon flow and distribution around the LS-CN assembly is accompanied by a homogeneous, non-isothermal, two-component turbulent flow model embodied in ANSYS Fluent. These, supported adequately by water modeling results, indicated that inertization of LS-CN assembly is considerably improved with the proposed design at argon flowrates typically practiced in industries (10 Nlit min À1 ). To substantiate laboratory findings, a plant-scale investigation is carried out, wherein shrouds with a new gas delivery design are fabricated and deployed in continuous bloom casting operation in a special steel plant. Industrial trials confirm the superiority of the new design over existing ones and demonstrate a 50% reduction in nitrogen pickup, during teeming, under identical operating conditions.

Role of Gas Aspiration through Ladle Shroud and Influence on Tundish Hydrodynamic Performances: A Physical and Mathematical Modeling Study

“…Figure 1 depicts a schematic of the molten steel transfer operation from a ladle to a continuous casting tundish via a ladle shroud. It is now rather well known [5][6][7][8][9] that due to aspiration of gases from the ambient (via slide-gate or shroud-collector nozzle joint), a two-phase, gas-liquid flow results in ladle shrouds. The phenomenon, particularly in the shroud, is shown to be driven by the low-pressure region prevalent inside a shroud during operation, assisted by various imperfections present at refractory artifacts joint/assembly.…”

“…Special steel plants in India [3][4][5] 7-25 show relatively smaller nitrogen pick up (≈5 ppm) because beyond 200 s or so, shroud tip is completely submerged, and steel-air interaction in tundish tends to cease completely. [4] The latter value of nitrogen pickup can, therefore, be solely attributed to air-steel interaction in ladle shroud and hence applied toward a first-hand estimate of volumetric gas aspiration rate in shroud, relative to liquid flow rate (i.e., Q g /Q L ).…”

“…Aspiration, rather than no aspiration of gases, is common during ladle to tundish transfer of melt in continuous casting, and the phenomenon is known to manifest in terms of "increased total nitrogen (as well as oxygen) content" of liquid steel between ladle and tundish. [2][3][4][5] The phenomena of aspiration and the resulting two-phase flows in the ladle shroud have been investigated at length by many investigators. [5][6][7][8][9] Thus, while Chatterjee et al [10] and Mukherjee et al [11] have investigated the role of gas aspiration on the characteristics of the tundish slag "eye," Tao et al [12] Zhang et al [13] and Solorio-Diaz et al [14] on the other hand, studied inclusion removal in the tundish via controlled gas injection (injection rate <0.50% of the liquid flow rate) via ladle shroud.…”

“…[2][3][4][5] The phenomena of aspiration and the resulting two-phase flows in the ladle shroud have been investigated at length by many investigators. [5][6][7][8][9] Thus, while Chatterjee et al [10] and Mukherjee et al [11] have investigated the role of gas aspiration on the characteristics of the tundish slag "eye," Tao et al [12] Zhang et al [13] and Solorio-Diaz et al [14] on the other hand, studied inclusion removal in the tundish via controlled gas injection (injection rate <0.50% of the liquid flow rate) via ladle shroud. However, only a few researchers [15] explored the possible influence of gas aspiration in the ladle shroud on the flow behavior and macromixing characteristics of the tundish.…”

Mathematical and Physical Modelling of Transient Multi-Phase Flows in a Ladle Shroud during Start-Up

“…Some more recent work on physical and mathematical modelling by Mukherjee and Mazumdar [10][11][12] validated the use of full-scale water models to study Ladle Shroud systems, given that the Reynolds number similarity is maintained and the isothermal approach was validated [10]. The authors also found that homogenous argon shrouding distribution was not achieved by the studied argon delivery systems [11]. Additionally, a new delivery system, which delivered the argon tangentially, was proposed, resulting in enhanced shielding of the lower nozzle-Ladle Shroud joint [11].…”