Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels

Wang, Jujin; Li, Weifu; Ren, Ying; Zhang, Lifeng

doi:10.1002/srin.201800600

Cited by 22 publications

(14 citation statements)

References 14 publications

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“…Uncontrolled non-metallic inclusions in steel may have detrimental effects on mechanical properties such as strength, toughness, and ductility [1][2][3][4][5][6]. Generally, characteristics of the inclusions are modified and optimized by refining slag, calcium treatment or rare earth treatment in molten steel to minimize their harmfulness and eliminate nozzle clogging during casting [7][8][9][10][11][12][13]. However, the final inclusions in steel product are not exactly the same as those in the molten steel.…”

Section: Introductionmentioning

confidence: 99%

Evolution of non-metallic inclusions during heat treatment

Liu

Webler

2020

Metall. Res. Technol.

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Isothermal heat treatment can not only modify steel microstructure, but also non-metallic inclusions. In this work, heat treatment experiments were conducted between 1373 and 1573 K (1100 and 1300 °C) to study the evolution of inclusion composition, morphology, and size distribution. Results showed that during the heat treatment at 1473 and 1573 K (1200 and 1300 °C), two main kinds of inclusions initially in the steel, CaS and MgO–Al2O3–CaO–CaS, gradually transformed to (Ca, Mn)S and MgO–Al2O3–(Ca, Mn)S inclusions, and some MgO–Al2O3–CaO inclusions also transformed to MgO–Al2O3–(Ca, Mn)S. At the lowest temperature studied, 1373 K (1100 °C), little change was observed. No significant changes in number density and area fraction of the measured inclusions were observed, while the average size of inclusions increased after the heat treatment. The extent of transformation of CaS, MgO–Al2O3–CaO–CaS and MgO–Al2O3–CaO inclusions increased with decreasing inclusion size and higher temperature.

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Section: Introductionmentioning

confidence: 99%

Evolution of non-metallic inclusions during heat treatment

Liu

Webler

2020

Metall. Res. Technol.

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“…[ 8,9 ] Experiments and kinetic calculations showed that the transformation rate of inclusions relied strongly on both the temperature and the size of inclusions. [ 10,11 ] Inclusions of CaO–Al 2 O 3 –(MgO) transformed into Al 2 O 3 –CaS–(MgO) during the heat treatment of solid Al‐killed steels, such as linepipe steels [ 12 ] and bearing steels. [ 13 ] For Ti‐bearing steels, the precipitation of TiN was found and in situ observed.…”

Section: Introductionmentioning

confidence: 99%

“…[6] Therefore, it was of great significance to investigate the transformation of inclusions in the solid steel to improve the performance of heavy rail steel products.Previous studies on the transformation of inclusions in solid steels mainly focused on the following types of steels and inclusions. Inclusions in austenitic stainless steels varied from MnO-SiO 2 -(Cr 2 O 3 ) to MnO-Cr 2 O 3 -(SiO 2 ) during heat treatment [7][8][9][10][11] depending on the concentrations of Cr and Si in the steel. [8,9] Experiments and kinetic calculations showed that the transformation rate of inclusions relied strongly on both the temperature and the size of inclusions.…”

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confidence: 99%

Effect of Total Calcium in Heavy Rail Steels on the Transformation of Inclusions during Heat Treatment at 1473 K

Wang

Zhang

Liu

et al. 2021

steel research int.

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Heat treatment experiments of heavy rail steel samples are performed with varied total calcium (T.Ca) in the steel to investigate the transformation of inclusions. Before heat treatment, original inclusions in the heavy rail steel are homogeneous Al2O3–SiO2–CaO–MgO with little CaS. After soaking for 60 min at 1473 K, the precipitation of the CaS outer layer and MgO·Al2O3 core is clearly observed. The transformation ratio of CaO to CaS in inclusions increases with T.Ca in the steel under current steel compositions. When the T.Ca content in the steel increases from 3 to 9 ppm, the CaS content of inclusions increases by 5.31–16.14%, while the CaO content of inclusions varies in an opposite way by 5.40–14.01%. In addition, the content of Al2O3 in inclusions increases by 1.73–6.33%, the SiO2 content decreases by approximately 6%, while the content of MgO changes little. Thermodynamic calculation performed by FactSage 7.0 verifies the transformation of inclusions from CaO–SiO2 to CaS–Al2O3 in the solid heavy rail steel during heat treatment. A kinetic model is developed to predict the evolution of inclusions in the heavy rail steel during the heat treatment process.

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“…[6][7][8][9][10][11][12][13][14][15] However, little attention was paid to study the variation of inclusions in solid steels during heating and rolling so far. [16][17][18][19] Significant variation in the composition of inclusions from the molten steel of continuous casting tundish to continuous casting products was reported. [20] In the 1960s, Takahashi [21] reported the transformation of inclusions in 304 stainless steels from MnO-SiO 2 to MnO-Cr 2 O 3 during the heating of the steel, which was confirmed and deeply investigated by Shibata et al [22] and Ren et al [23] Li et al reported the transformation of inclusions in solid Al-Ti-deoxidized steels during heating.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Inclusions in a Complicated‐Deoxidized Heavy Rail Steels During Heating

Zhang

Chu³

et al. 2020

steel research int.

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The transformation of inclusions in a heavy rail steel during heating is investigated in laboratory experiments. When the steel is heated at 1000–1300 °C, inclusions of CaO–SiO2–Al2O3–MgO are transformed into CaS–MgO·Al2O3 ones and the contents of CaS and Al2O3 in inclusions increase, whereas those of CaO and SiO2 decrease. When the steel is heated at 1400 °C, the MgO·Al2O3 phase in inclusions precipitates, whereas CaS, CaO, and SiO2 still exist, which is caused by the lower thermodynamic driving force at high temperature. With the holding time increasing from 0 to 7 h, the composition of inclusions tends to the equilibrium value which is predicted using Factsage. The transformation phenomenon is validated using thermodynamic analysis and a kinetic model is established to predict the composition of inclusions during heating. The MgO·Al2O3 phase formed in inclusions in the steel during heating results in an exposure of MgO·Al2O3 spinel inclusions after rolling, which are rigid and harmful to the performance of steel rails.

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Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels

Cited by 22 publications

References 14 publications

Evolution of non-metallic inclusions during heat treatment

Evolution of non-metallic inclusions during heat treatment

Effect of Total Calcium in Heavy Rail Steels on the Transformation of Inclusions during Heat Treatment at 1473 K

Transformation of Inclusions in a Complicated‐Deoxidized Heavy Rail Steels During Heating

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