| 1. |
- Alexis, Jonas, et al.
(författare)
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Heating and electromagnetic stirring in a ladle furnace – a simulationmodel
- 2000
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 40:11, s. 1098-1104
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional simulation model coupling heating and induction stirring in an ASEA-SKF ladle furnace was developed. Data of the heat transfer from the area to the steel bath were predicted in a separate model and included as boundary conditions in a ladle model. The are model considers the contributions of heat transferred by of each of the following mechanisms: radiation, convection, condensation and energy transported by electrons. Predictions were made to simulate the change of temperature distribution in the ladle during simultaneous heating with electrodes and stirring by induction. A first attempt was made to compare the predictions with measured temperatures from a 100 t ASEA-SKF ladle. The agreement was found to be fairly good when heat-flux data for a 25 cm are length were used as input to the ladle model. This indicates that the model can be used for more in-depth studies of the effects of heating for ladles that are inductively stirred.
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| 2. |
- Andersson, Margareta A.T., et al.
(författare)
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Slag-metal reactions during ladle treatment with focus on desulphurisation
- 2002
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 29:3, s. 224-232
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Tidskriftsartikel (refereegranskat)abstract
- Within several cooperative projects, KTH (Royal Institute of Technology), Ovako Steel AB, and MEFOS have investigated the desulphurisation of bearing steel during vacuum degassing. The work includes thermodynamic calculations of the slag-metal equilibrium, CFD modelling of slag-metal reactions, and plant trials. Results from the various studies are presented and discussed in this paper. Models for predicting slag properties (sulphide capacity, viscosity, and oxide activities) in liquid slags as functions of slag composition and temperature have been used for the calculation of data which have been employed in static and dynamic modelling of sulphur refining. The results from static modelling show that the method allows fast and easy evaluation of the theoretical desulphurisation conditions during degassing at Ovako Steel AB, as well as theoretical determination of the parameters that have the greatest influence on the equilibrium sulphur distribution. The conclusion from dynamic modelling is that the vacuum degassing operation can be described dynamically with the present knowledge of sulphide capacity, sulphur distribution, viscosity, and oxide activities of ladle slags if this knowledge is combined with fluid flow modelling to derive the overall kinetics. The presented model approaches have been found useful in understanding the sulphur refining process at Ovako Steel AB. The dynamic modelling concept is also believed to have potential for dynamic descriptions of other slag-metal reactions in steelmaking.
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| 3. |
- Bi, Yanyan, et al.
(författare)
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Investigations of inclusions in ferrochromium alloys
- 2014
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:10, s. 756-762
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Tidskriftsartikel (refereegranskat)abstract
- Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si-Cr-O and Cr-O oxides as well as intermetallic Cr-Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr-Mn-S, Cr-C-N, Si-Al-Ca-Mg-O and Ca-O-P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.
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| 4. |
- Bi, Yanyan, et al.
(författare)
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Three Dimensional Evaluations of REM Clusters in Stainless Steel
- 2014
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 54:6, s. 1266-1273
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Tidskriftsartikel (refereegranskat)abstract
- It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. In this study, 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 different holding times after the addition of mischmetal. Thereafter, REM clusters collected on film filters after electrolytic extraction and filtration were investigated in three dimensions (3D) by SEM in combination with EDS. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of 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 mu m. In addition, the size and number of most clusters in PT are larger than those in IH samples. Furthermore, the formation mechanisms and evolution of different type of REM clusters were discussed in both PT and IH heats.
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| 5. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process performance
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 378-385
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Tidskriftsartikel (refereegranskat)abstract
- A plant trial has been performed, with recycling of ladle slag to the LD converter at SSAB EMEA, Lulea, Sweden. The effect of ladle slag addition on the slag and steel composition, together with the slag weight, was investigated with sampling both during the blow and at blow end. The addition of ladle slag resulted in an increase in slag weight between 1 and 2 t throughout the blow and an increase of 3 wt-% in the slag Al2O3 content. This indicated that the ladle slag melted during the initial stages of the blow and enhanced the early slag formation. Lime additions were reduced with 3.5 kg t(-1) liquid steel without drawbacks on the phosphorus or sulphur refining. Heats with added ladle slag had an increase in blowing time with similar to 4% and an increased tendency for slopping. However, this can be handled by different lance and addition programmes.
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| 6. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process under production conditions
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 318-326
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Tidskriftsartikel (refereegranskat)abstract
- The influence of recycled ladle slag on the basic oxygen furnace (BOF) process under production conditions was investigated in plant trials. More specifically, 25 heats with ladle slag additions and 23 heats without ladle slag additions were studied. Both steel and slag samples were collected, from which the chemical compositions were determined. In addition, several process parameters were monitored. Overall, it was found that recirculation of ladle slag during normal production conditions works fine. On the positive side, it was seen that the steel quality concerning the phosphorus and sulphur contents of liquid steel has, in accordance with previous studies, not been affected by the ladle slag additions. Furthermore, no major differences in the slag composition occur when the recycling of ladle slag to BOF is performed. Finally, in comparison to previous studies, the increased tendency for slopping when adding ladle slag could be eliminated with a change in the lance schedule. However, on the negative side, it was seen that the addition of ladle slag leads to an increased blowing time due to lower iron ore additions. Moreover, the slag weight at tapping increased due to an increased weight of added slag formers.
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| 7. |
- Doostmohammadi, Hamid, et al.
(författare)
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Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting
- 2010
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Ingår i: STEEL RES INT. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:2, s. 142-149
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Tidskriftsartikel (refereegranskat)abstract
- In the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary In this work non-metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study A scanning electron microscope (SEM) was used to assess inclusion size and morphology The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called 'INCAFeature' was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples.
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| 8. |
- Grip, Carl-Erik, et al.
(författare)
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Theoretical and practical study of thermal stratification and drainage in ladles of different geometry
- 2000
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 29:1, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- SSAB Lulea, SSAB Oxelosund, MEFOS and Lulea University of Technology have cooperated in developing theoretical models for prediction of thermal stratification and drainage in steel ladles. Predicted results have been verified by measurements done in production ladles with heat weighs of 105 and 200 tonne as well as in a 7-tonne pilot plant ladle. The thermal stratification was measured by thermocouples at different depths. The drainage flow was studied by means of tracer experiments. Numerical simulation models of the steel flow were developed for 7, 105 and 200 tonne steel ladles. The agreement between predictions and measurements was found to be good. The conclusion is that CFD simulation gives a good prediction of stratification and drainage flows in production ladles.
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| 9. |
- Jansson, Sune, et al.
(författare)
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Corrosion mechanism and kinetic behaviour of MgO-C refractory material in contact with CaO-Al2O3-SiO2-MgO slag
- 2005
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 34:5, s. 283-292
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Tidskriftsartikel (refereegranskat)abstract
- The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical refractory specimens. The specimens were rotated for 15-120 min at a speed of 100-400 rpm in the molten slag. The rate of corrosion was found to increase with an increase in temperature and rod rotation speed, and to decrease when the slag was nearly saturated with MgO. The experimental results support the assumption that the diffusion of magnesium oxide through the slag-phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of refractory material into the slag followed by penetration of pores and grain boundaries and dispersion of the grains into the slag.
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| 10. |
- Jansson, Sune, et al.
(författare)
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Corrosion mechanism of commercial doloma refractories in contact with CaO-Al2O3-SiO2-MgO slag
- 2008
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 35:2, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution of three doloma based refractories in liquid CaO-Al2O3-SiO2-MgO slag was studied. Cylindrical refractory specimens of doloma, carbon bonded doloma, and magnesia doloma were rotated in a stationary crucible of molten slag under forced convection conditions. Slag composition, temperature, rod rotation speed and rod immersion time were varied. The refractory dissolution rate was determined from the change in diameter of the cylindrical specimens. The corrosion rate was found to increase with temperature and rod rotation speed and decrease when the slag was nearly saturated with MgO. The findings of the study substantiate the assumption that the diffusion of magnesium oxide through the slag boundary layer controls the corrosion process. The results indicated the overall corrosion process to be the dissolution of refractory material into the slag, followed by slag penetration of the pores and grain boundaries and finally, dispersion of the grains into the slag.
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