Steel Thermo‐Fluid‐Dynamics at Tundish Drainage and Quality Features

Abstract

In steelmaking and casting, transient operations are very critical for product quality and process regularity. This holds especially for the tundish. Typical drawbacks can occur at ladle change, where, for example, refilling high flow rates induce flow short‐circuits risky for dispersed oxides (“inclusions”) dragging towards the strands. At drainage, vortices formation can affect steel cleanliness via slag entrapment. Such topics were investigated for an industrial tundish with computational fluid dynamics validated tools. The focus was given on a multi‐strand layout more prone to unevenness features. As a matter of fact, the different steel path to reach different strands causes often too high temperature differences and different strand cleanliness levels. Strands closer to the tundish center, are generally hotter and less clean; the others, slightly colder but cleaner. Multiphase models, together with advanced meshing techniques and validated boundary conditions, were used to describe tundish refilling and drainage. Within the operating conditions of concern, a bath height of 300 mm was found as a best compromise between the need of avoiding slag entrapment through vortices and to have maximum yield. Once applied into operating practice, no rejection for cleanliness or customer claims were achieved. As refers to temperature loss from ladle to tundish, a drop at strands of about 2 and of 4°C from tundish inlet to strand, in agreement with plant data over about 700 heats and literature experiments under the same operating conditions, were found.

Improvement in steel cleanliness of central strand in billet caster

“…Battaglia et al [14] studied the steel cleanliness and slag entrapment during the drainage of multi-strand tundish by using CFD tools. Generally, strands that are closest to turbostopper are generally hotter and lesser clean than other stands.…”

Numerical simulation of slag entrapment process during the end of casting in tundish

“…In order to avoid slag entrapment, a certain amount of molten steel must be left in the tundish [5][6][7], which will reduce the metal yield rate and increase the production cost. The final pouring level height is dependent on the critical slag entrapment height (h cs ).…”

Two-Phase Numerical Modeling of Grade Intermixing in a Steelmaking Tundish

“…The operating parameters of tundish and transient melt level in tundish has a major influence on intermixed grade melt. The shapes and sizes of tundish are varied according to the need of final product [6,7], however, the operating parameters such as inflow rate, residual volume, and outflow (throughput) rate, etc., have more influence on mixing of different grades during sequential casting [8][9][10]. The above parameters modify the melt flow structure inside the tundish.…”