Physico‐chemical aspects of the behaviour of inclusions in steels

Gatellier, C.; Gaye, Henri; Lehmann, J.; Pontoire, Jean Noël; Riboud, Paul Victor

doi:10.1002/srin.199300987

Cited by 21 publications

(22 citation statements)

References 5 publications

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“…Unlike MnS, most of the sulfides (CaS, TeS, CeS) are nearly non-deformable during rolling. [10][11][12] Mostly, these inclusions are quite tiny, less than 5 mm in size. However, depending on the steelmaking practice, even bigger inclusions may be found.…”

Section: ϫ9mentioning

confidence: 99%

Thermodynamic Evaluation of Formation of Oxide–Sulfide Duplex Inclusions in Steel

Choudhary

Ghosh

2008

ISIJ Int.

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Calcium is widely used for improving the castability of liquid steel, as well as for improvement of steel cleanliness and inclusion modification for better quality steel. Calcium modifies solid alumina inclusions, arising out of deoxidation of liquid steel, into liquid calcium aluminate. Depending upon the steel composition, calcium sulfide (CaS) and/or various forms of calcium aluminates may form. Sulfides are often associated with the oxide phase, which is typically known as oxide-sulfide duplex inclusion. Formation of solid calcium sulfide must be avoided during the ladle treatment of liquid steel, since it is detrimental to the castability of steel. In the present work a thermodynamic model has been developed for predicting the formation of oxide-sulfide duplex inclusions arising out of competitive reactions between [O], [S] and [Ca] in Al-killed steel. The model predictions of the present work were compared with those reported in literature, as well as with the types of inclusions observed in steel samples collected from the plant. Reasonably good agreements amongst them were observed. The results indicated that in order to achieve completely liquid calcium aluminate without forming any sulfides the sulfur content of liquid steel must be sufficiently low. With increasing S content of liquid steel, complete modification of alumina inclusions into liquid calcium aluminate becomes difficult. The maximum sulfur content to avoid formation of CaS depends upon the steel composition, principally aluminum. The sulfide inclusions are often a solid solution of CaS and MnS. Thermodynamic analysis for this system was also carried out. Based on the analysis in the present work, it is possible to predict the influence of sulfide composition on formation of duplex inclusions.

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Section: ϫ9mentioning

confidence: 99%

Thermodynamic Evaluation of Formation of Oxide–Sulfide Duplex Inclusions in Steel

Choudhary

Ghosh

2008

ISIJ Int.

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“…A technique that has been extensively used by IRSID 3,4) for obtaining crystallization data of the SiO 2 -CaO-Al 2 O 3 -MgO system consists of melting and holding the slag Sample at an elevated temperature above its melting point, before cooling the Sample to an isothermal temperature where the Sample is held for different holding times. After the specific holding time the Sample is quenched and inspected by optical microscope and/or by Scanning Electron Microscope (SEM).…”

Section: Introductionmentioning

confidence: 99%

In Situ Observation of the Role of Alumina Particles on the Crvstallization Behavior of Slags.

2000

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The confocal laser scanning microscope (CLSM) allows crystallization behavior in liquid slags to be observed in situ at high temperatures. Slags in the lime-silica-alumina-magnesia system are easily under cooled and it is possible to construct time temperature transformation (TTT) diagrams for this system. The presence of solid alumina particles in these liquid slags was studied to determine if these particles act as heterogeneous nucleation sites that cause the precipitation of solid material within slags. The introduction of alumina particles reduced the incubation time for the onset of crystallization and increased the temperature at which crystallization was observed in the slags to close to the liquidus temperature for the slag. Crystal growth rates are in a good agreement with Ivantsov's solution of the problem of diffusion controlled dendritic growth. Alumina appears to be a potent nucleating agent in the slag systems that were studied.

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“…3. It clearly shows a positive deviation from the ideality, and the deviation shows more positive than that of Gaterlier et al 24) It is reminded that the results of Gaterlier et al were obtained by estimation as mentioned in Sec. 2.1.…”

Section: (4)mentioning

confidence: 55%

“…1. Gatellier et al 24) reported a Henrian activity coefficient of CaS in the solid (Ca,Mn)S solution at 1 470°C (γ°CaS = 2.3). However, the value was obtained by extrapolating to pure MnS from the CaS-MnS-FeS (XFeS = 0.07-0.28) ternary sulfide solution, thus it can only be regarded as an estimation.…”

Section: Literature Datamentioning

confidence: 99%

Activity Measurement of the CaS–MnS Sulfide Solid Solution and Thermodynamic Modeling of the CaO–MnO–Al2O3–CaS–MnS–Al2S3 System

2013

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In order to provide a prediction tool for sulfide/oxide/oxysulfide inclusion evolution in Mn-Al steel with a Ca addition/CaO-based flux, a comprehensive thermodynamic database for the inclusion system composed of CaO-MnO-Al2O3-CaS-MnS-Al2S3 was developed in the present study. Activity of MnS in a CaSMnS sulfide solid solution was experimentally determined by employing a chemical equilibrium technique at 1 400°C and 1 500°C. The measured activity exhibits a positive deviation from an ideal behavior, which is in consistent with the known two-phase separation of the sulfide solid solution at lower temperature (Tcr = 1 200°C). Based on the activity and the phase diagram data available in literature, a thermodynamic modeling of the CaS-MnS system was carried out. The following excess Gibbs free energy of the CaSMnS sulfide solid solution was obtained:Furthermore, using available thermodynamic modeling results for other constituent sub-systems, a larger thermodynamic database of the CaO-MnO-Al2O3-CaS-MnS-Al2S3 system was developed. A Modified Quasichemical Model in the quadruplet approximation was used to model the Gibbs free energy of the oxysulfide liquid solution. Comparisons between the model calculation and available experimental data show good agreement. The developed thermodynamic model and the database were used to predict unexplored phase diagrams with various nMn/(nCa + nMn) ratio, and sulfide capacity of the CaO-MnO-Al2O3 oxide liquid phase. The database can be used along with software for Gibbs free energy minimization in order to calculate any phase diagram section or thermodynamic property.

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Physico‐chemical aspects of the behaviour of inclusions in steels

Cited by 21 publications

References 5 publications

Thermodynamic Evaluation of Formation of Oxide–Sulfide Duplex Inclusions in Steel

Thermodynamic Evaluation of Formation of Oxide–Sulfide Duplex Inclusions in Steel

In Situ Observation of the Role of Alumina Particles on the Crvstallization Behavior of Slags.

Activity Measurement of the CaS–MnS Sulfide Solid Solution and Thermodynamic Modeling of the CaO–MnO–Al2O3–CaS–MnS–Al2S3 System

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