Role of Solidification in Submerged Entry Nozzle Clogging During Continuous Casting of Steel

Abstract

Metallurgists are embroiled in a debate on the role of solidification in submerged entry nozzle (SEN) clogging during continuous casting of steel: does clogging originate from solidification, or does clogging cause the solidification? This study tries to clarify this debate. An enthalpy‐based mixture continuum model is used to simulate solidification in a clog structure. The 3D structure of the clog is reconstructed using X‐ray tomography images of an as‐clogged piece in an SEN, and is directly used in the numerical model. The flow and solidification in the open pores/channels of the clog structure are then calculated. The modeling results demonstrate that although solidification does occur deep in the clog structure as the melt flow is stopped, a gap remains between the solidification and clog fronts. This gap signifies an open‐channel clog region, and the clog structure in this region needs to be mechanically strong to withstand the impact of the melt flow; otherwise, fragmentation occurs. The study verifies that the solidification cannot occur before clogging if the molten steel has sufficient superheat and the SEN is properly preheated. A SEN made of an isolating refractory material can postpone the clogging, thereby extending its service life.

On Modelling Parasitic Solidification Due to Heat Loss at Submerged Entry Nozzle Region of Continuous Casting Mold

“…For the solidification modelling, a low-alloy steel (C 0.05 wt%) was selected. The physical properties were calculated using the IDS software [81] at a typical CC cooling rate of 10 K/s to compare the obtained results with previous studies [50,64]. The casting parameters were adjusted to combine the settings from both publications.…”

“…In the current study, the clog layer was assumed to be uniform with a moderate thickness of 12 mm [64]. The clogging was assumed to be non-permeable for the flow.…”

“…The clogging was assumed to be non-permeable for the flow. It contained of the 45% volume fraction of the melt that could solidify [64]. This simplified model provided a general impression regarding clog influence on the parasitic solidification inside the SEN.…”

“…Recently, an advanced model was developed based on turbulent quantities near the refractory wall [61,62] to study whether clogging or parasitic solidification dominates. This model was employed together with a solidification model to analyze which phenomenon is dominant [63,64]; using an experimental setup with melt velocities of~4-5 m/s, solidification inside the SEN was found to follow the clogging front.…”

“…Additionally, the authors of the present study considered the formation of clogging inside an SEN. A uniform 12 mm clog layer with 45% entrapped liquid steel was assumed to be non-permeable for the melt flow. The process parameters and the clogging material properties were taken from the literature [50,64].…”