Crystals

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13 pages, 2425 KiB

Open AccessArticle

Simulation of the Refining Process of Ultra-Low Carbon (ULC) Steel

by Dali You, Christian Bernhard, Andreas Viertauer and Bernd Linzer

Crystals 2021, 11(8), 893; https://doi.org/10.3390/cryst11080893 - 30 Jul 2021

Cited by 2 | Viewed by 2717

The standard production route for mild steels for automotive purposes is still based on conventional continuous casting (CC) and hot strip rolling (HSR). The current trend towards the “zero-carbon car” will demand the abating of material emissions in the future. Thin slab casting [...] Read more.

The standard production route for mild steels for automotive purposes is still based on conventional continuous casting (CC) and hot strip rolling (HSR). The current trend towards the “zero-carbon car” will demand the abating of material emissions in the future. Thin slab casting and direct rolling (e.g., Arvedi endless strip production (ESP)) is an approach to reduce CO₂ emissions by 50% compared to CC and HSR. One of the main limitations in applying ESP for the production of ultra-low carbon/interstitial free (ULC/IF) steels is clogging. Clogging is the blockage of the submerged entry nozzle due to the build-up of oxide layers or an oxide network. The high clogging sensitivity of IF steels results most probably from the FeTi addition, and hence, a general change of the deoxidation practice might be an option to overcome these problems. In the present work, the thorough refining process of ULC steel was simulated by addressing the different deoxidation routes and the influence of titanium (Ti) alloying on steel cleanness. The developed ladle furnace (LF) and the Ruhrstahl Heraeus (RH) refining models were applied to perform the simulation. Before the simulations, the models are briefly described and validated by the published industrial data. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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17 pages, 5672 KiB

Open AccessArticle

Influence of Gas Density and Plug Diameter on Plume Characteristics by Ladle Stirring

by Dmitrii Riabov, Muhammad Murtaza Gain, Tomasz Kargul and Olena Volkova

Crystals 2021, 11(5), 475; https://doi.org/10.3390/cryst11050475 - 23 Apr 2021

Cited by 3 | Viewed by 2225

Abstract

The paper presents new results concerning the influence of the gas density and porous plug diameter on the nature of liquid steel stirring with an inert gas in the ladle. The tests were carried out on a cold model of a 30t ladle [...] Read more.

The paper presents new results concerning the influence of the gas density and porous plug diameter on the nature of liquid steel stirring with an inert gas in the ladle. The tests were carried out on a cold model of a 30t ladle using particle image velocimetry (PIV) with a high-speed camera to analyse the plume zone formed during the supply of argon and helium as a stirring gas. The similarity criteria for the investigation of stirring processes in cold model in the past were discussed and compared. The modified Morton number was used in this paper to relate the gas flow rate in the model with real objects. The presented results constitute complete documentation of the influence of the plug diameter and gas density on the size of formed gas bubbles and the velocity of gas bubbles rising in different zones of the plume, plume, and spout geometry, including the expansion angle, spout height, open eye area, and gas hold-up. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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10 pages, 3591 KiB

Open AccessArticle

New Insight on Liquid Steel Microalloying by Pulse-Step Method in Two-Strand Slab Tundish by Numerical Simulations

by Adam Cwudziński

Crystals 2021, 11(4), 448; https://doi.org/10.3390/cryst11040448 - 20 Apr 2021

Cited by 2 | Viewed by 1835

Abstract

Developing a technology for introducing alloy addition to liquid steel during the course of continuous casting process seems to be an interesting approach to enhancing the steelmaking process, especially as the effective introduction of micro-additives or non-metallic inclusion modifiers to the liquid steel [...] Read more.

Developing a technology for introducing alloy addition to liquid steel during the course of continuous casting process seems to be an interesting approach to enhancing the steelmaking process, especially as the effective introduction of micro-additives or non-metallic inclusion modifiers to the liquid steel is the key to the production of the highest-quality steel. This paper presents the results of investigation describing the process of liquid steel chemical homogenisation in the two-strand slab tundish. The alloy was fed to liquid steel by pulse-step method. Five tundish equipment variants with different flow control devices and alloy addition feeding positions were considered. The paper includes fields of liquid steel flow, alloy concentration vs. time curves, dimensionless mixing time, minimum time values and alloy concentration deviations at tundish outlets. The results pointed much more effectively with liquid steel mixing nickel than aluminium. For aluminium obtaining a 95% chemical homogenisation level requires three-fold more time. Moreover, it is definitely beneficial for chemical homogenisation to initiate the alloying process simultaneously in two sites. This procedure generates, among others, the least alloy deviation of concentration at tundish outlets. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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14 pages, 1789 KiB

Open AccessArticle

Influence of Al and N Content and Cooling Rate on the Characteristics of Complex MnS Inclusions in AHSS

by Muhammad Nabeel, Michelia Alba and Neslihan Dogan

Crystals 2020, 10(11), 1054; https://doi.org/10.3390/cryst10111054 - 19 Nov 2020

Cited by 13 | Viewed by 2390

Abstract

This study focused on the characteristics of complex MnS inclusions in advanced high strength steels. The effect of metal chemistry (Al and N) and the cooling rate of steel were evaluated by analyzing the inclusions present in five laboratory produced steels. The observed [...] Read more.

This study focused on the characteristics of complex MnS inclusions in advanced high strength steels. The effect of metal chemistry (Al and N) and the cooling rate of steel were evaluated by analyzing the inclusions present in five laboratory produced steels. The observed complex MnS inclusions contained Al₂O₃-MnS, AlN-MnS, and AlON-MnS. An increase in Al content from 0.5% to 6% increased the number of complex MnS inclusions by ~4 times. In comparison, a decrease of ~80% was observed due to the increased N content of steel from <10 ppm to ~50 ppm. MnS precipitation ratio was used to determine the potency of different inclusions forming complex MnS inclusions due to heterogeneous nucleation. It was found that the MnS precipitation ratio of the observed inclusions was related to their misfit with MnS, and it decreased in the order of AlN > AlON > Al₂O₃. Moreover, it was determined that AlN particles could be easily engulfed at the solidification front relative to Al₂O₃, which resulted in a higher MnS precipitation ratio for Al₂O₃ under slow cooling conditions. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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18 pages, 11450 KiB

Open AccessArticle

Process Diagnosis of Liquid Steel Flow in a Slab Mold Operated with a Slide Valve

by Jafeth Rodríguez-Ávila, Carlos Rodrigo Muñiz-Valdés, Rodolfo Morales-Dávila and Alfonso Nàjera-Bastida

Crystals 2020, 10(11), 1035; https://doi.org/10.3390/cryst10111035 - 13 Nov 2020

Viewed by 1997

Abstract

Slab molds receive liquid steel from the tundish through bifurcated submerged entry nozzles (SEN) using a slide valve as throughput control. Due to the off-centering position of the three plates’ orifices that conform to the valve to control the steel passage, the flow [...] Read more.

Slab molds receive liquid steel from the tundish through bifurcated submerged entry nozzles (SEN) using a slide valve as throughput control. Due to the off-centering position of the three plates’ orifices that conform to the valve to control the steel passage, the flow inside the nozzle and mold is inherently biased toward the valve opening side. In the practical casting, a biased flow induces inhomogeneous heat fluxes through the mold copper plates. The nozzle design itself is also a challenge, and has direct consequences on the quality of the product. A diagnosis of the casting process regarding the internal and external flows, performed through experimental and mathematical simulation tools, made it possible to reach concrete results. The mathematical simulations predicted the flow dynamics, and the topography and levels variations of the meniscus characterized through a full-scale water model. The flows are biased, and the meniscus level fluctuations indicated that the current nozzle is not reliable to cast at the two extremes of the casting speeds of 0.9 m/min and 1.65 m/min, due to the danger of mold flux entrainment. A redesign of the nozzle is recommended, based on the experimental and mathematical results presented here. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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19 pages, 9815 KiB

Open AccessArticle

Modeling Study of EMBr Effects on the Detrimental Dynamic Distortion Phenomenon in a Funnel Thin Slab Mold

by Saul Garcia-Hernandez, Carlos Humberto Gonzalez-Guzman, Rodolfo Morales Davila, Jose de Jesus Barreto, Enif Gutierrez and Ismael Calderon-Ramos

Crystals 2020, 10(11), 958; https://doi.org/10.3390/cryst10110958 - 22 Oct 2020

Cited by 11 | Viewed by 2348

Abstract

The turbulent phenomena occurring in the thin slab mold affect the final product quality. Therefore, it is essential to carry out studies to understand and control their occurrence. Current research aims to study the electromagnetic brake (EMBr) effects on the flow patterns in [...] Read more.

The turbulent phenomena occurring in the thin slab mold affect the final product quality. Therefore, it is essential to carry out studies to understand and control their occurrence. Current research aims to study the electromagnetic brake (EMBr) effects on the flow patterns in a funnel thin slab mold. The objective is to prevent the detrimental phenomenon known as dynamic distortions (DD) of the flow, applying the EMBr in the typical horizontal position (H-EMBr) and a new vertical position close to the narrow faces (V-EMBr). The fluid dynamics are simulated using the Reynolds stress model (RSM), the Volume of Fluid (VOF) model and the Maxwell equations in their magnetohydrodynamics (MHD) simplification. The results show that the H-EMBr effectively counteracts the DD phenomenon by reducing the submerged entry nozzle (SEN) ports' mass flow rate differences. The EMBr reduces the highest meniscus fluctuations from −10 to ±3 mm with a field intensity of 0.1T and almost 0 mm for higher field intensities. In contrast, the V-EMBr configuration does not reduce or control at all the DD phenomenon, even though eliminating the upper roll flows does not diminish the meniscus fluctuation amplitudes and induces new small roll flows close to the SEN's wall. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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18 pages, 5502 KiB

Open AccessArticle

Numerical Simulation of Melting Kinetics of Metal Particles during Tapping with Argon-Bottom Stirring

by Kinnor Chattopadhyay, Rodolfo Morales-Davila, Alfonso Nájera-Bastida, Jafeth Rodríguez-Ávila and Carlos Rodrigo Muñiz-Valdés

Crystals 2020, 10(10), 901; https://doi.org/10.3390/cryst10100901 - 6 Oct 2020

Cited by 7 | Viewed by 2159

Abstract

Molten steel is alloyed during tapping from the melting furnace to the argon-bottom stirred ladle. The metallic additions thrown to the ladle during the ladle filling time are at room temperature. The melting rates or kinetics of sinking-metals, like nickel, are simulated through [...] Read more.

Molten steel is alloyed during tapping from the melting furnace to the argon-bottom stirred ladle. The metallic additions thrown to the ladle during the ladle filling time are at room temperature. The melting rates or kinetics of sinking-metals, like nickel, are simulated through a multiphase Euler–Lagrangian mathematical model during this operation. The melting rate of a metallic particle depends on its trajectory within regions of the melt with high or low turbulence levels, delaying or speeding up their melting process. At low steel levels in the ladle, the melting rates are higher on the opposite side of the plume zone induced by the bottom gas stirring. This effect is due to its deviation after the impact of the impinging jet on the ladle bottom. The higher melting kinetics are located on both sides at high steel levels due to the more extensive recirculation flows formed in taller baths. Making the additions above the eye of the argon plume spout increases the melting rate of nickel particles. The increase of the superheat makes the heat flux more significant from the melt to the particle, increasing its melting rate. At higher superheats, the melting kinetics become less dependent on the fluid dynamics of the melt. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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17 pages, 4038 KiB

Open AccessArticle

Effect of Nitrogen Content on the Formation of Inclusions in Fe-5Mn-3Al Steels

by Michelia Alba, Muhammad Nabeel and Neslihan Dogan

Crystals 2020, 10(9), 836; https://doi.org/10.3390/cryst10090836 - 18 Sep 2020

Cited by 8 | Viewed by 2650

Abstract

The effect of N content on the characteristics and formation of inclusions in the Fe-5Mn-3Al steels was investigated in this study. Two synthetic steel melts were produced by two different methods—N₂ gas purging and injecting—to introduce nitrogen into the melt. The N [...] Read more.

The effect of N content on the characteristics and formation of inclusions in the Fe-5Mn-3Al steels was investigated in this study. Two synthetic steel melts were produced by two different methods—N₂ gas purging and injecting—to introduce nitrogen into the melt. The N content of steel melt varied from 2 to 54 ppm. An increase in the N content to 47 ppm (for 533N-P) and 58 ppm (for 533N-I) increased the total amount of inclusions from 13 to 64 mm⁻² and from 21 to 101 mm⁻², respectively. The observed inclusions were Al₂O_3(pure), Al₂O₃-MnS, AlN_(pure), AlN-MnS, AlON, AlON-MnS, and MnS. When the N content was less than 10 ppm, AlN-MnS inclusions were the primary type of inclusions and they formed as solidification products. With an increase in the N content, AlN_(pure) inclusions became the dominant type of inclusions as AlN was stable in the liquid steel. These findings were confirmed by thermodynamic calculations. The influence of cooling rate on the types of inclusions was studied and a higher number of AlN-MnS inclusions were observed in samples with slow cooling rate. Full article

(This article belongs to the Special Issue Liquid Steel Alloying Process)

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