Hydrogen Traps and Hydrogen Induced Cracking in 20CrMo Steel

The gas injection in a ladle using a porous plug is simulated using both the Euler‐Euler and Euler‐Lagrange approaches. The effects of various forces, bubble sizes, and bubble injection frequencies on the flow pattern are modeled. For predicting axial velocity and turbulent kinetic energy, the Euler‐Lagrange approach fits better than Euler‐Euler approach with the measured data. In the Euler‐Euler approach, differences in axial velocities and turbulent kinetic energies for various bubble sizes mainly appears in the plume zone. In the Euler‐Lagrange approach, different bubble sizes with the same injection frequency have a small impact on the turbulence dissipation. Furthermore, the turbulent dispersion from the gas phase to the liquid phase has an important effect on the plume structure and spout eye formation. For both modeling, the smaller the bubble diameter is, the larger the axial velocity and turbulent kinetic dissipation are in the central zone. For the bubble coalescence and breakup, according to the comparison of two modeling approaches, the Euler‐Lagrange approach is more accurate in predicting the flow pattern for gas injection with a porous plug in the ladle.

Section: Introductionmentioning

confidence: 99%

Comparison of Euler‐Euler Approach and Euler–Lagrange Approach to Model Gas Injection in a Ladle

Liu

Ersson

et al. 2019

Section: Introductionmentioning

confidence: 99%

“…The formation of exposed slag eyes in the gas-stirred metallurgical vessels such as ladle [11][12][13][14][15][16][17][18][19][20][21][22][23] or tundish [24][25][26] is a common phenomenon. Extensive studies of the formation of exposed slag eyes in the ladle have been performed by physical [11][12][13][14][15][16][17][18] and numerical modeling. [19][20][21][22][23] For physical modeling, the water model experiments have been widely used to study the sizes of slag eyes, various dimensionless expressions for exposed slag eye areas have been proposed by Yonezawa and Schwerdtfeger, [11,12] Subagyo et al, [13] Iguchi et al, [14] Mazumdar and Evans, [15] Krishnapisharody and Irons, [16,17] Liu et al, [18] and so on.…”

Section: Introductionmentioning

confidence: 99%

“…Extensive studies of the formation of exposed slag eyes in the ladle have been performed by physical [11][12][13][14][15][16][17][18] and numerical modeling. [19][20][21][22][23] For physical modeling, the water model experiments have been widely used to study the sizes of slag eyes, various dimensionless expressions for exposed slag eye areas have been proposed by Yonezawa and Schwerdtfeger, [11,12] Subagyo et al, [13] Iguchi et al, [14] Mazumdar and Evans, [15] Krishnapisharody and Irons, [16,17] Liu et al, [18] and so on. For numerical modeling, Li et al, [19] Llanos et al [20] developed a mathematical model based on volume of fluid (VOF) approach to analyse the argon/ steel/slag three-phase flow and the exposed slag eye phenomenon in the ladle.…”

Section: Introductionmentioning

confidence: 99%

“…Cloete et al [21] and Liu et al [22] developed a mathematical model by employing the discrete phase model (DPM) to describe the bubble transport and the VOF model to track the fluctuation of steel/slag interface without considering the bubble coalescence and breakup. Further Li et al [23] developed a similar mathematical model by employing the DPM-VOF coupled method to investigate the slag layer and eye formation considering the bubble coalescence and breakup. Recently, the exposed slag eye formation in an inert gasshrouded tundish has been studied by Chattopadhyay et al, [24][25][26] a large number of experiments were done in a full scale and in a down-scaled water model under various operating conditions, and a mathematical model based on the DPM-VOF coupled method was developed to predict the investigated multiphase phenomenon.…”

Section: Introductionmentioning

confidence: 99%

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Physical and Numerical Modeling of Exposed Slag Eye in Continuous Casting Mold using Euler–Euler Approach

Liu

Vakhrushev

et al. 2018

Gas injection through the submerged entry nozzle (SEN) into the continuous casting mold can be an effective approach for preventing SEN clogging and promoting the floatation of the non‐metallic inclusions. However, sometimes the exposed slag eyes due to gas injection appear on the top surface of the liquid slag layer, resulting in heat losses, re‐oxidation, and nitrogen pickup in the molten steel. An Eulerian multiphase‐flow model is developed to predict the argon‐steel‐slag three‐phase flow in a slab continuous casting mold. All the phases are treated based on Eulerian approach. The mathematical model is compared with the industrial observations and the water model experiments. Both of physical and numerical results reproduce the phenomenon of the high gas concentration at the SEN exit port. Most of the argon bubbles stay below the slag layer for quite long time because the slag blocks their floatation. Furthermore, the argon bubbles would gradually gather in a dense plume while escaping through the slag layer. Scattered argon exit spots are found at the top surface of slag layer. Two main locations of the exposed slag eye are found: 1) adjacent to the SEN; 2) at the mold's mid‐section at the position where a concentrated argon plume breaches through the slag layer. The near‐SEN exposed eye occurs under any of considered conditions. The one at the mid‐section is formed when the meniscus convex reaches a critical level, been dependent on the casting conditions.

Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open‐Eye in Gas‐Stirred Ladles With Single and Dual‐Plugs

Ramasetti

Visuri

Sulasalmi

et al. 2019

In secondary steelmaking, the optimal size and position of open-eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open-eye in a gas stirred ladle was investigated. A one-fifth scale water model of 150-ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open-eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5 cm using a gas flow rate of 7.5 NL min À1 . The effect of the number of plugs on the open-eye area for the same range of top layer thickness mentioned above was also studied. The relative open-eye area generated due to the gas injection through the dual plugs decreased from 49.9 to 5.8%. To study the effect of top layer properties, rapeseed oil, castor oil and paraffin oil were employed for studying the effect of density and dynamic viscosity on the open-eye formation. The results revealed that a larger open-eye is formed when the density is increased. Furthermore, it was found out that the density of the upper phase dominates the open-eye formation while dynamic viscosity has only minor effect. The results obtained from numerical simulations and physical modeling were found to be in good agreement.