Formation and Evolution of Silicate Inclusions in Molten Steel by Magnesium Treatment

Zhang, Qingsong; Min, Yi; Xu, Haisheng; Xu, Jiujian; Liu, Chengjun

doi:10.2355/isijinternational.isijint-2018-543

Cited by 11 publications

(8 citation statements)

References 29 publications

(19 reference statements)

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“…The change of oxygen activity in melts during experiments was measured by an electrolyte oxygen probe, the method of which was introduced in the earlier work. 23,42) Specifically, the first measurement of oxygen activity (a[O] 1 ) was in the initial melt without deoxidation, the second a[O] 2 was measured after Al deoxidation, then the final a[O] 3 was measured after taking the last sample from the melts with Ce and Mg addition. The different addition amounts of Al, Ce and Mg in experiments and the measured oxygen activity are listed in Table 1.…”

Section: High-temperature Simulation Experimentsmentioning

confidence: 99%

Effect of Cerium and Magnesium Addition on Evolution and Particle Size of Inclusions in Al-killed Molten Steel

Wang

Liu

2022

ISIJ Int.

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To investigate the effect of Ce and Mg addition on the evolution of inclusions in Al-killed molten steel, both thermodynamic calculations and laboratory-scale experiments were carried out in the present work. The samples taken at different time after various addition amounts and order of Ce and Mg were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The results show that Al 2 O 3 was firstly modified to MgAl 2 O 4 and then the transformation from MgAl 2 O 4 to CeAlO 3 with the addition order of Al → Mg → Ce. Under the addition order of first Ce followed by Mg, CeAlO 3 was eventually modified to MgAl 2 O 4 in the case of low Mg contents, and was modified to MgO with high Mg contents. The thermodynamic conditions were performed to discuss the mechanism of inclusions formation and transformation. More importantly, under the condition of Ce addition followed by Mg addition, due to the transformation from large-sized RE-inclusions to disperse MgO-containing ones, the average sizes of inclusions reduced from 3.12 μm and 3.28 μm to 1.99 μm and 1.83 μm, respectively. This evolution behavior of inclusions was firstly observed in-situ by a novel experiment, in which the large-sized CeAlO 3 clusters were disaggregated to MgO-Al 2 O 3 particles with smaller sizes. The control strategy of inclusions proposed in this study is expected to improve the casting process and the product quality of Al-killed steel containing rare earth element.

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Section: High-temperature Simulation Experimentsmentioning

confidence: 99%

Effect of Cerium and Magnesium Addition on Evolution and Particle Size of Inclusions in Al-killed Molten Steel

Wang

Liu

2022

ISIJ Int.

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“…The principles and operation methods of oxygen activity are detailed introduced in the literature. 34) A certain amount of Si or Si/Al was then added to the molten steel and kept for 30 minutes to deoxidize followed by the second oxygen activity (a[O] 2 ) measurement. Sample A was then taken by a quartz pipe after Si deoxidation and quenched in an ice bath, while samples B, C were treated with Ce after Si and Si/Al deoxidation respectively.…”

Section: Samples Preparationmentioning

confidence: 99%

Agglomeration Characteristics of Various Oxide Inclusions in Molten Steel Containing Rare Earth Element under Different Deoxidation Conditions

Wang

Liu

2021

ISIJ Int.

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Comprehensive investigation of agglomeration behavior of oxide inclusions in steel-containing rare earth (RE) under different deoxidation conditions is essential for improving the nozzle-clogging problem during continuous casting. The present study first optimized the thermodynamic model by supplementing thermodynamic data of the RE-compound to study the formation of various inclusions in the Ce-Si-Al-O system. On this basis, laboratory-scale experiments with different deoxidation conditions were designed to obtain samples containing one single type of inclusions, viz., SiO 2 , SiO 2 -Ce 2 O 3 or SiO 2 -Al 2 O 3 -Ce 2 O 3 , respectively. Subsequently, the agglomeration behavior of inclusions was observed in situ by confocal laser scanning microscopy (CLSM), and the corresponding attractive forces were calculated to compare the agglomeration tendency of various inclusions. The results indicate that, in the Si deoxidized samples, SiO 2 -Ce 2 O 3 inclusions agglomerate to form clusters with the attractive force of 4.3 × 10 − 17 N to 4.2 × 10 − 15 N, which is weaker than that of Al 2 O 3 and Al 2 O 3 -Ce 2 O 3 inclusions after Al deoxidation. Although SiO 2 inclusions can agglomerate, their attractive force is only 6.3 × 10 − 19 N to 1.2 × 10 − 16 N, which is the weakest of the above inclusions. In the case of Si/Al complex deoxidization, spherical SiO 2 -Al 2 O 3 -Ce 2 O 3 liquid inclusions are formed after Ce treatment, and no agglomeration of such inclusions was observed in situ. The study could provide theoretical guidance for improving the nozzle-clogging problem of RE-containing steel from inclusion-controlling perspective under different deoxidation conditions.

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“…The solubility of magnesium in molten steel is relatively high. Magnesium has a strong affinity with oxygen and sulfur, which can effectively reduce the content of O and S in steel, and improve the quantity and morphology of inclusions in steel; moreover, it has an obvious modification effect on oxide inclusions and plays a role in purifying molten steel [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Kinetics Study on the Modification Process of Al2O3 Inclusions in High-Carbon Hard Wire Steel by Magnesium Treatment

Xiong

et al. 2021

Metals

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The aim of the experiment in this work is to modify the Al2O3 inclusions in high-carbon hard wire steel by magnesium treatment. The general evolution process of inclusions in steel is: Al2O3 → MgO·Al2O3(MA) → MgO. The unreacted core model was used to study the modification process of inclusions. The results show that the complete modification time (tf) of inclusions is significantly shortened by the increase of magnesium content in molten steel. For Al2O3 inclusions with radius of 1 μm and Mg content in the range of 0.0005–0.0055%, the modification time of Al2O3 inclusions to MA decreased from 755 s to 25 s, which was reduced by 730 s. For Al2O3 inclusions with a radius of 1.5 μm and Mg content in the range of 0.001–0.0035%, the Al2O3 inclusions were completely modified to MgO inclusions from 592 s to 55 s. The Mg content in the molten steel increased 3.4-fold, and the time for complete modification of inclusions was shortened by about 10-fold. With the increase of Al and O content in molten steel, the complete modification time increased slightly, but the change was small. At the same time, the larger the radius of the unmodified inclusion is, the longer the complete modification time is. The tf of Al2O3 inclusions with a radius of 1 μm when modified to MA is 191 s, and the tf of Al2O3 inclusions with a radius of 2 μm when modified to MA is 765 s. According to the boundary conditions and the parameters of the unreacted core model, the MgO content in inclusions with different radius is calculated. The experimental results are essentially consistent with the kinetic calculation results.

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Formation and Evolution of Silicate Inclusions in Molten Steel by Magnesium Treatment

Cited by 11 publications

References 29 publications

Effect of Cerium and Magnesium Addition on Evolution and Particle Size of Inclusions in Al-killed Molten Steel

Effect of Cerium and Magnesium Addition on Evolution and Particle Size of Inclusions in Al-killed Molten Steel

Agglomeration Characteristics of Various Oxide Inclusions in Molten Steel Containing Rare Earth Element under Different Deoxidation Conditions

Kinetics Study on the Modification Process of Al2O3 Inclusions in High-Carbon Hard Wire Steel by Magnesium Treatment

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