Oxidation of Molten Steel by the Air Permeated through a Refractory Tube.

Suzuki, Mikio; Yamaoka, Yuichi; Kubo, Noriko; Suzuki, Makoto

doi:10.2355/isijinternational.42.248

Cited by 15 publications

(14 citation statements)

References 3 publications

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“…This rate will build up 1.1 mm thickness of clogging per hour on the entire SEN wall, assuming that 50% of the inclusions attach to the walls [40] and that the clog consists of 50% alumina and 50% steel [41]. This represents up to 30% of the typical clogging rate observed in commercial operations [26]. Note that the aspirated gas flow rate (Equation (42)) increases with the cube of the gap size, so large gaps will cause severe clogging and quality problems very quickly.…”

Section: Estimation Of Air Aspiration Reoxidation and Transient Clomentioning

confidence: 99%

“…Another model used a Smoothed Particle Hydrodynamics (SPH) method to predict the amount of oxides in cast ingots during filling, based on the surface area of metal exposed to the air [25]. A study of reoxidation due to air permeation through the SEN refractory wall [26] concluded that this source of oxides is not enough to be fully responsible for nozzle clogging. However, the contribution of aspirated air through possible cracks or gaps in the refractory was not considered.…”

Section: Previous Modelsmentioning

confidence: 99%

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Modeling Air Aspiration in Steel Continuous Casting Slide-Gate Nozzles

Yang

Olia

Thomas

2021

Metals

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Air aspiration is an important cause of nozzle clogging and inclusions in final products of continuous casting of steel due to the presence of metal oxides (such as alumina) which occur through the reoxidation of molten steel. This problem is most likely to occur when the flow control system (slide-gate or stopper rod) causes the pressure inside the nozzle to drop below atmospheric pressure, drawing gas into the system through possible cracks or gaps in the refractory walls. In this work, a 1-D pressure-energy model of the complete metal delivery system from the tundish to the mold is developed to predict the pressure distribution and throughput under dynamic operating conditions and varying clogging conditions. The energy balance approach includes pressure losses in the slide-gate, wall friction, and nozzle geometry variations, including the effects of multiphase flow due to argon gas injection. The model also predicts air aspiration, oxide inclusion formation, and the time for clogging shutdown. The predicted pressure distribution is verified with a three-dimensional numerical simulation of multiphase turbulent flow, and is validated with plant measurements. Parametric studies with different submerged entry nozzle (SEN) designs revealed that a smaller SEN diameter may lessen negative pressure by redistributing the pressure loss from the slide-gate to the entire nozzle through increased friction losses. Under negative pressure, a submillimeter-thin gap was shown to cause considerable air aspiration. Clogging shutdown times were evaluated for several scenarios under static and dynamic operating conditions.

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Section: Estimation Of Air Aspiration Reoxidation and Transient Clomentioning

confidence: 99%

Section: Previous Modelsmentioning

confidence: 99%

Modeling Air Aspiration in Steel Continuous Casting Slide-Gate Nozzles

Yang

Olia

Thomas

2021

Metals

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“…It was assumed that the permeability of the SEN refractory to CO gas was sufficiently high that CO gas flowing through refractory pores did not cause any pressure drop. Laboratory [28] and plant [4] scale investigations on the permeability of SEN refractories have shown that SEN permeability does not play a significant role in clogging. Therefore, the above assumption of a large permeability of the SEN refractory appears reasonable.…”

Section: A Validation Of the Modelmentioning

confidence: 99%

Mathematical Modeling of the Early Stage of Clogging of the SEN During Continuous Casting of Ti-ULC Steel

Barati¹,

Wu²,

Michelic

et al. 2021

Metall Mater Trans B

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The clogging of the submerged entry nozzle (SEN) during the continuous casting of steel can be divided into two stages: the “early stage,” when the initial layer of the clog covers the SEN refractory surface owing to chemical reactions, and the “late stage,” when the clog layer continues to grow because of the deposition of non-metallic inclusions (NMIs). In this paper, a mathematical formulation is proposed for the build-up of the initial oxide. The chemical reaction mechanism is based on the work of Lee and Kang (Lee et al. in ISIJ Int 58:1257–1266, 2018): a reaction among SEN refractory constituents produces CO gas, which can re-oxidize the steel melt and consequently form an oxide layer on the SEN surface. The proposed formulation was further incorporated as a sub-model in a transient clogging model, which was previously developed by the current authors to track the late stage of clogging. The thermodynamics and kinetics of CO production, depending on the local pressure and temperature, must be considered for the sub-model of early-stage clogging. Test simulations based on a section of an actual industrial SEN were conducted, and it was verified that the clogging phenomenon is related to the SEN refractory, the chemical reaction with the steel melt, the local temperature and pressure, and the transport of NMIs by the turbulent melt flow in the SEN. The model was qualitatively validated through laboratory experiments. The uncertainty of some parameters that govern the reaction kinetics and permeability of the oxide layer is discussed.

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“…The decrease in pressure can cause air to be sucked through cracks, joints and porous refractory of the submerged entry nozzle (SEN), making re‐oxidation of steel possible 1–4. On the other hand, according to the measurements made by Suzuki et al 5 remarkable re‐oxidation of steel cannot be attributed to air sucked through refractory.…”

Section: Introductionmentioning

confidence: 99%

Modelling of Pressure Distribution inside the SEN in a Stopper‐rod controlled System

Savolainen

Rousu

Fabritius

et al. 2010

steel research int.

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Shrouding tubes and submerged entry nozzles (SEN) are mainly used on steel transfer between process units of continuous casters. Molten steel flow in the SEN or shrouding tube causes a pressure drop which creates possibilities for air aspiration through refractory material. The objective of this research was to model the pressure distribution in the SEN of a continuous caster using a full scale water model. Effects of casting speed, SEN immersion depth and liquid level of tundish on the pressures at the SEN wall and centre were defined. The experiments proved that SEN immersion depth had the most remarkable effect on the pressure inside the SEN. However experiments did not show a significant effect of casting speed and tundish liquid level on the pressure inside the SEN. This research presents a simplified model for pressure distribution in SEN. The presented model agrees well with measurements at the SEN wall.

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Oxidation of Molten Steel by the Air Permeated through a Refractory Tube.

Cited by 15 publications

References 3 publications

Modeling Air Aspiration in Steel Continuous Casting Slide-Gate Nozzles

Modeling Air Aspiration in Steel Continuous Casting Slide-Gate Nozzles

Mathematical Modeling of the Early Stage of Clogging of the SEN During Continuous Casting of Ti-ULC Steel

Modelling of Pressure Distribution inside the SEN in a Stopper‐rod controlled System

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