Ladle Treatment

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Pär Jönsson - One of the best experts on this subject based on the ideXlab platform.

  • effect of the stirring mode on the behavior of al2o3 mgo particles and clusters during Ladle Treatment of ni based alloy 825
    Steel Research International, 2017
    Co-Authors: Andrey Karasev, Hans E O Kellner, Olle Sundqvist, Pär Jönsson
    Abstract:

    Effect of the Stirring Mode on the Behavior of Al2O3–MgO Particles and Clusters during Ladle Treatment of Ni-based Alloy 825

  • effect of stirring mode on non metallic inclusions in alloy 825 during Ladle Treatment
    2017
    Co-Authors: Hans E O Kellner, Andrey Karasev, Olle Sundqvist, Pär Jönsson
    Abstract:

    It is well known thatinclusions affect the properties of steels and alloys. Therefore, it is essentialto understand what types of inclusions that exist and how they behave duringthe production. Thi ...

  • slag metal equilibrium calculations for estimation of oxygen activity in molten steel during Ladle Treatment
    2016
    Co-Authors: Johan Ekengard, Pär Jönsson, Margareta Andersson
    Abstract:

    In the present paper three different methods to calculate the equilibrium oxygen activity have been compared with measured oxygen activities and oxygen activities based on sulphur equilibrium betwe ...

  • effect of stirring practice on sulphur and nitrogen refining as well as inclusion removal in Ladle Treatment
    Steel Research International, 2015
    Co-Authors: Charlotte Medioni, Pär Jönsson, Du Sichen
    Abstract:

    Steel cleanliness as a function of stirring practice during vacuum degassing Treatment have been investigated in industrial studies at the steel plants of SSAB Special Steels in Oxelosund and Uddeholm AB in Hagfors. The cleanliness was examined with regards to the contents of sulphur, nitrogen and large inclusions (>10µm).The stirring practice during the vacuum degassing Treatment has been studied with respect to time, namely by shortening the vacuum degassing Treatment time from 24 to 15 minutes. Furthermore, the effect of the stirring intensity was studied by measuring the open eye zone using camera recordings. The focus has been to study the effect of a shortened vacuum degassing time as well as a controlled stirring intensity on the steel cleanliness. Moreover, study the effect of subsequent induction stirring, after vacuum degassing, on the amount of inclusions. By taking steel and slag samples taken before and after the vacuum degassing Treatment, the different stirring practices could be investigated. It should be noted that all heats reached the desired composition regardless of the Treatment time and stirring practice.The results from the trials at SSAB Special Steels showed that the stirring practice during vacuum degassing have an effect on the total number of inclusions. The strong argon stirring during vacuum degassing with visible open eyes resulted in an average increase of 400% of the total amount of inclusions >10µm. However, no difference between a vacuum degassing time of 24 or 15 minutes was seen with respect to the increased amount of inclusions, denitrogenization or desulphurization. During the subsequent induction stirring, which was softer with no open eyes, the effect of the stirring practice was unclear due to overlapping confidence intervals. An average decrease of 65% of the total amount of inclusions >10 µm was seen for the heats with non-overlapping confidence intervals. Based on these results it can be suggested that the use of a soft induction stirring after the vacuum degassing Treatment as a possible process change to reach lower amounts of large inclusions.The stirring intensity during the vacuum degassing Treatment was measured as the average Ladle eye size during the trials at Uddeholm AB. This, due to that stronger stirring results in larger Ladle eye zone. The results show that the amount of smaller inclusions ( 22.4 μm). Moreover, the denitrogenization and desulphurization was not affected by the changed stirring intensity during vacuum degassing. It was also found that the average Ladle eye size did not correlate to the logged average argon flow.

  • evolution of different inclusions during Ladle Treatment and continuous casting of stainless steel
    Isij International, 2013
    Co-Authors: Andrey Karasev, Pär Jönsson
    Abstract:

    As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloyson the steel cleanness. Thus, the number, morphology, size and composition of inclusions in sixdifferent ferroalloys (FeTi, FeNb, FeSi,SiMn, LC and HC FeCr) were investigatedin this study. This was done in three dimensions (3D) by using a SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Theresults show that thenon-metallic and metallic inclusions can besuccessfully analyzed on the surface of a film filterafter a separation of the inclusions from the matrix. Overall, the inclusions canbe divided into two categories depending on the melting point. Furthermore, the possible transformation of different kinds of inclusions after their addition to the liquid steel canalso be determined.The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were also investigated and compared during Ladle Treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the Ladle Treatment and casting during two plant trials: a low Al steel (LAl) and a high Al steel (HAl). Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It wasfound that the morphology and composition of inclusions and clusters in both heats were significantly changed during the Ladle Treatment and casting. Most of inclusions (44-98%) in a low Al steel are MgO-CaO-SiO2-Al2O3spherical inclusions. The compositions of irregular and regularinclusions and clusters in steel samples of a high Al steel were mostly MgO·Al2O3spinel, but also complex sphericalinclusions containing Al2O3-MgO-CaO-SiO2. In addition, the phase stabilitydiagram based on Darken’s quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. Therefore, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at differentholding times after the addition of a mischmetal. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of the holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples.Largesize inclusions are recognized to be crucially harmful for the mechanical properties of steel products. Therefore, predictionsof the maximum size of Al2O3-CaO spherical inclusions in an Fe-10 mass% Ni alloy have been examined based on two dimensional (2D) and three dimensional (3D) investigations. The effects of the number of measurements and unit volume on the estimated 3D results were also investigated.

Du Sichen - One of the best experts on this subject based on the ideXlab platform.

  • effect of stirring practice on sulphur and nitrogen refining as well as inclusion removal in Ladle Treatment
    Steel Research International, 2015
    Co-Authors: Charlotte Medioni, Pär Jönsson, Du Sichen
    Abstract:

    Steel cleanliness as a function of stirring practice during vacuum degassing Treatment have been investigated in industrial studies at the steel plants of SSAB Special Steels in Oxelosund and Uddeholm AB in Hagfors. The cleanliness was examined with regards to the contents of sulphur, nitrogen and large inclusions (>10µm).The stirring practice during the vacuum degassing Treatment has been studied with respect to time, namely by shortening the vacuum degassing Treatment time from 24 to 15 minutes. Furthermore, the effect of the stirring intensity was studied by measuring the open eye zone using camera recordings. The focus has been to study the effect of a shortened vacuum degassing time as well as a controlled stirring intensity on the steel cleanliness. Moreover, study the effect of subsequent induction stirring, after vacuum degassing, on the amount of inclusions. By taking steel and slag samples taken before and after the vacuum degassing Treatment, the different stirring practices could be investigated. It should be noted that all heats reached the desired composition regardless of the Treatment time and stirring practice.The results from the trials at SSAB Special Steels showed that the stirring practice during vacuum degassing have an effect on the total number of inclusions. The strong argon stirring during vacuum degassing with visible open eyes resulted in an average increase of 400% of the total amount of inclusions >10µm. However, no difference between a vacuum degassing time of 24 or 15 minutes was seen with respect to the increased amount of inclusions, denitrogenization or desulphurization. During the subsequent induction stirring, which was softer with no open eyes, the effect of the stirring practice was unclear due to overlapping confidence intervals. An average decrease of 65% of the total amount of inclusions >10 µm was seen for the heats with non-overlapping confidence intervals. Based on these results it can be suggested that the use of a soft induction stirring after the vacuum degassing Treatment as a possible process change to reach lower amounts of large inclusions.The stirring intensity during the vacuum degassing Treatment was measured as the average Ladle eye size during the trials at Uddeholm AB. This, due to that stronger stirring results in larger Ladle eye zone. The results show that the amount of smaller inclusions ( 22.4 μm). Moreover, the denitrogenization and desulphurization was not affected by the changed stirring intensity during vacuum degassing. It was also found that the average Ladle eye size did not correlate to the logged average argon flow.

  • a study of nitrogen pickup from the slag during waiting time of Ladle Treatment
    Steel Research International, 2014
    Co-Authors: Carl Allertz, Niklas Kojola, Wang Hui, Du Sichen
    Abstract:

    An investigation of the nitrogen pickup of liquid steel from Ladle slag after vacuum degassing was made. Nitride capacities, C-N, of a number of Ladle slags were determined at controlled nitrogen a ...

  • mechanism study on formation and chemical changes of calcium aluminate inclusions containing sio2 in Ladle Treatment of tool steel
    Ironmaking & Steelmaking, 2011
    Co-Authors: Minho Song, Mselly Nzotta, Lars Ragnarsson, Du Sichen
    Abstract:

    The formation and chemical changes of non-metallic inclusions in the Ladle Treatment were studied with laboratory experiments and theoretical analysis. Refractory samples covered by the Ladle glaze ...

  • the effect of solid particles on liquid viscosity
    Steel Research International, 2011
    Co-Authors: Minho Song, Du Sichen
    Abstract:

    The present work is to study slag phenomena in steelmaking process. In order to attain thegoal, a number of high temperature experiments and simulation experiments were carried out. Four master slags were used to study the effect of CaF2 on slag viscosity. Experimentalresults indicated the effect of CaF2 on slag viscosity depended strongly on the composition ofmaster slag. For high basicity slags, CaF2 mainly suppressed the precipitation of solid phasesat lower temperatures, leading to a lower viscosity compared to CaF2-free slags. For slagswith higher SiO2 contents, CaF2 both lowered the viscosity of the liquid phase and suppressedthe precipitation of solid phases. The viscosities of solid-liquid mixtures were experimentally determined for silicon oilparaffinsystem at room temperature and solid-liquid oxide mixture at steelmakingtemperature. The results of both measurements indicated that the increasing trend of mixturesviscosity with particle fraction can be described by Einstein-Roscoe equation.Silicone oils of different viscosities were used to simulate slag foaming. The experimentalresults showed, at a constant viscosity, the foaming height increased first with superficialvelocity before reaching a maximum value. Thereafter, the foaming height decreased with thefurther increase of the superficial velocity. Similar, a maximum foaming height was observedat an optimum viscosity when a constant superficial gas velocity was applied. Based on theexperimental data, a semi-empirical equation of foaming height was developed. Thepredictions of the model agreed well with experiment data. The model could also reasonablywell explain the industrial pilot trial experiments. Water-silicon oils model and liquid alloy (Ga-In-Sn)- 12% HCl acid model were employed tosimulate the formation of open-eyes in a gas stirred Ladle. The experimental results indicatedthat the viscosity of the top liquid and the interfacial tension between the two liquids had onlylittle effect on the open-eye size. A semi-empirical model was developed to describe the sizeof open-eye as functions of the gas flow rate, bath height and slag height. The two sets ofparameters obtained for the water and Ga-In-Sn models were very different. Industrial trialswere also conducted to examine the applicability of the models. Liquid alloy model couldwell predict the formation of an open-eye during Ladle Treatment. Two cold models, sodium tungstate-oil model and water-oil model, were carried out tosimulate the formation of droplets in a gas stirred Ladle. The experimental results showed thatthe gas flow rate and interfacial tension had strong impact on the size of droplets. A semiempiricalmodel was developed to describe the size of droplets for water model. Meanwhile,the parameter obtained for water model can be used for sodium tungstate-silicone oil system.The results indicate the model has strong compatibility.

  • observation on physical growth of nonmetallic inclusion in liquid steel during Ladle Treatment
    Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2011
    Co-Authors: Young Jo Kang, Bahman Sahebkar, Piotr R Scheller, Kazuki Morita, Du Sichen
    Abstract:

    The behaviors of several types of inclusions at a high temperature were examined using a confocal scanning laser microscope (CSLM, 1LM21H/SVF17SP). Although alumina inclusions tended to impact on each other, agglomerate, and grow quickly, no other inclusion type, such as spinel as well as solid and liquid calcium aluminate, was observed to attract each other. The results of confocal microscope study were compared with the industrial investigation. For this purpose, many steel samples were taken at different stages of Ladle Treatment. The samples were analyzed by scanning and light optical microscopes. Approximately 50,000 inclusions of several types were examined. Only alumina inclusions were attracted to each other and agglomerate. No agglomeration by attractive behavior was observed in the other types of inclusions, including liquid inclusions. Both the industrial data and the in situ observation by CSLM indicate that, although the attraction force and the agglomeration play a significant role in the growth of alumina inclusions, the agglomeration of spinel and calcium aluminate inclusions does not need special consideration in Ladle Treatment. The agglomeration of liquid calcium aluminate inclusions took place only when they occasionally met as a result of external force, which led to low collision probability. However, the agglomeration of the liquid calcium aluminate inclusions along with alumina particles could be detrimental in the casting process.

Margareta Andersson - One of the best experts on this subject based on the ideXlab platform.

  • slag metal equilibrium calculations for estimation of oxygen activity in molten steel during Ladle Treatment
    2016
    Co-Authors: Johan Ekengard, Pär Jönsson, Margareta Andersson
    Abstract:

    In the present paper three different methods to calculate the equilibrium oxygen activity have been compared with measured oxygen activities and oxygen activities based on sulphur equilibrium betwe ...

  • Effect of Temperature on Oxygen Activity during Ladle Treatment
    Isij International, 2008
    Co-Authors: Johan Björklund, Margareta Andersson, Takahiro Miki, Pär Jönsson
    Abstract:

    The effect of temperature on oxygen activity in steel was studied in plant trials where temperature and oxygen activity were measured at two depths and at the same time during different parts of la ...

  • the effect of Ladle Treatment on inclusion composition in tool steel production
    Steel Research International, 2008
    Co-Authors: Johan Björklund, Margareta Andersson, Mselly Nzotta, Pär Jönsson
    Abstract:

    The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the Ladle refining process. The inclusion composition is related to top slag composition and other parameters during Ladle Treatment. The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during Ladle Treatment. Evaluation of inclusion composition during the Ladle refining have revealed that the majority of the inclusions belonged to the system Al2O3-CaO-MgO-SiO2 and showed a continuous composition change throughout the Ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3. The final composition after vacuum Treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during Ladle refining were proven to give large differences of the inclusion composition. Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.

  • equilibrium between slag steel and inclusions during Ladle Treatment comparison with production data
    Ironmaking & Steelmaking, 2007
    Co-Authors: Johan Björklund, Margareta Andersson, Pär Jönsson
    Abstract:

    The primary purpose of the investigation was to determine whether equilibrium conditions exist between slag and steel and inclusions and steel after silicon deoxidation and aluminium deoxidation. I ...

  • determination of inclusion characteristics in the asea skf process using the modified spark induced oes technique as a complement in studying the influence of top slag composition
    Steel Research International, 2005
    Co-Authors: M Almcrantz, Margareta Andersson, Pär Jönsson
    Abstract:

    The spark-induced modified optical emission spectroscopy (OES) technique developed by Ovako Steel makes it possible to rapidly determine inclusion characteristics in steel samples. In earlier investigations using the modified spark-induced OES technique for steel samples taken from billets, predicted oxygen contents agreed well with results from conventional melt extraction analyses. In this investigation, samples taken during Ladle Treatment in an ASEA-SKF Ladle furnace were analysed using the modified OES technique. When comparing the results with inclusion characteristics determined by conventional analysis, similar trends were found. Plant trials were also carried out where three different top slag compositions were used. The purpose was to evaluate if the modified OES technique can be used to study the effect of changes in the refining operation on inclusion characteristics. Results indicated that the modified OES technique could be used to determine the effect of a changed slag composition on the inclusion characteristics in the steel. Since the modified OES method provides rapid feedback of inclusion characteristics, it has the potential of being used for faster optimisation of Ladle refining operations.

Johan Björklund - One of the best experts on this subject based on the ideXlab platform.

Minho Song - One of the best experts on this subject based on the ideXlab platform.

  • mechanism study on formation and chemical changes of calcium aluminate inclusions containing sio2 in Ladle Treatment of tool steel
    Ironmaking & Steelmaking, 2011
    Co-Authors: Minho Song, Mselly Nzotta, Lars Ragnarsson, Du Sichen
    Abstract:

    The formation and chemical changes of non-metallic inclusions in the Ladle Treatment were studied with laboratory experiments and theoretical analysis. Refractory samples covered by the Ladle glaze ...

  • the effect of solid particles on liquid viscosity
    Steel Research International, 2011
    Co-Authors: Minho Song, Du Sichen
    Abstract:

    The present work is to study slag phenomena in steelmaking process. In order to attain thegoal, a number of high temperature experiments and simulation experiments were carried out. Four master slags were used to study the effect of CaF2 on slag viscosity. Experimentalresults indicated the effect of CaF2 on slag viscosity depended strongly on the composition ofmaster slag. For high basicity slags, CaF2 mainly suppressed the precipitation of solid phasesat lower temperatures, leading to a lower viscosity compared to CaF2-free slags. For slagswith higher SiO2 contents, CaF2 both lowered the viscosity of the liquid phase and suppressedthe precipitation of solid phases. The viscosities of solid-liquid mixtures were experimentally determined for silicon oilparaffinsystem at room temperature and solid-liquid oxide mixture at steelmakingtemperature. The results of both measurements indicated that the increasing trend of mixturesviscosity with particle fraction can be described by Einstein-Roscoe equation.Silicone oils of different viscosities were used to simulate slag foaming. The experimentalresults showed, at a constant viscosity, the foaming height increased first with superficialvelocity before reaching a maximum value. Thereafter, the foaming height decreased with thefurther increase of the superficial velocity. Similar, a maximum foaming height was observedat an optimum viscosity when a constant superficial gas velocity was applied. Based on theexperimental data, a semi-empirical equation of foaming height was developed. Thepredictions of the model agreed well with experiment data. The model could also reasonablywell explain the industrial pilot trial experiments. Water-silicon oils model and liquid alloy (Ga-In-Sn)- 12% HCl acid model were employed tosimulate the formation of open-eyes in a gas stirred Ladle. The experimental results indicatedthat the viscosity of the top liquid and the interfacial tension between the two liquids had onlylittle effect on the open-eye size. A semi-empirical model was developed to describe the sizeof open-eye as functions of the gas flow rate, bath height and slag height. The two sets ofparameters obtained for the water and Ga-In-Sn models were very different. Industrial trialswere also conducted to examine the applicability of the models. Liquid alloy model couldwell predict the formation of an open-eye during Ladle Treatment. Two cold models, sodium tungstate-oil model and water-oil model, were carried out tosimulate the formation of droplets in a gas stirred Ladle. The experimental results showed thatthe gas flow rate and interfacial tension had strong impact on the size of droplets. A semiempiricalmodel was developed to describe the size of droplets for water model. Meanwhile,the parameter obtained for water model can be used for sodium tungstate-silicone oil system.The results indicate the model has strong compatibility.

  • Effect of Ladle slag of previous heat on number of non-metallic inclusions in Ladle Treatment of tool steel
    Ironmaking & Steelmaking, 2011
    Co-Authors: Minho Song, Mselly Nzotta, Du Sichen
    Abstract:

    Nine series of industrial trials were carried out using the same Ladle in each series to examine the effect of Ladle slag on the number of non-metallic inclusions in the next heat. Steel and slag samples were taken after Ladle vacuum Treatment for chemical composition analysis. Samples of the final steel product were examined to determine the number of non-metallic inclusions. It was found that the number of inclusions increased with SiO2 content of the Ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions.Theoretical analysis based on the experimental results suggested that the formation of 2CaO.SiO2 followed, but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.

  • A Study on the Correlation between Ladle Glaze and Non-Metallic Inclusions in the Ladle Treatment
    2010
    Co-Authors: Minho Song
    Abstract:

    In the present thesis, the correlation between Ladle glaze and non-metallic inclusions in the Ladle Treatment was studied. A number of industrial trials with full scale Ladle and laboratory works w ...

  • study of the formation of non metallic inclusions by Ladle glaze and the effect of slag on inclusion composition using tracer experiments
    Steel Research International, 2009
    Co-Authors: Minho Song, Mselly Nzotta, Du Sichen
    Abstract:

    In the present thesis, the correlation between Ladle glaze and non-metallic inclusions in the Ladle Treatment was studied. A number of industrial trials with full scale Ladle and laboratory works were performed to investigate the inclusions in the Ladle Treatment. BaO was used as tracer in the Ladle slag to investigate the effect of slag on inclusion composition and the formation of non-metallic inclusions by Ladle glaze. BaO was detected in the inclusions of all followed heats. This observation showed strong evidence for the generation of non-metallic inclusions by the Ladle glaze. The increase of the fractions of BaO containing inclusions and their average content of BaO in the first heat with tracer suggested that the effect of slag on the composition of inclusions was a very slow process. The detachment of Ladle glaze and the chemical transformations of oxide solution in the MgO matrix were investigated. The experimental results evidently showed that the Ladle glaze could be the source of inclusions continually during the Ladle Treatment. Samples of liquid oxide solution to simulate the liquid oxide inclusions carried over from EAF were equilibrated with molten steel under controlled atmosphere. The results along with thermodynamic calculation suggested that the SiO2 content of inclusions from EAF could be considerably reduced by dissolved aluminium in the steel. This would explain the vanishing of inclusions containing high SiO2 content after deoxidation. Due to the lack of experimental data, the viscosities of slags in the Al2O3-CaO-MgO-SiO2 system were measured using the rotating cylinder method in the temperature range of 1720 to 1910 K. Eight different slag compositions related to the secondary steel making operations were selected. Viscosities in this system and its sub-systems were expressed as a function of temperature and composition based on the viscosity model developed earlier at KTH. The activities of oxide components in the Al2O3-CaO-MgO-SiO2 systems at 1873 K were measured by equilibrating liquid slag and metal. Either silicon or copper was used as the metal phase and the oxygen partial pressure was controlled with different mixing rates of Ar and CO gas flow in equilibrium with graphite. Iso-activity lines were drawn from the measured activity values in the isothermal section of the slag systems. Nine series of industrial trials were carried out using the same Ladle in each series to examine the effect of Ladle slag on the number of non-metallic inclusions in the next heat. It was found that the number of inclusions increased with SiO2 content of the Ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions. Theoretical analysis based on the experimental results suggested that the formation of 2CaO∙SiO2 followed but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.

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