| 1. |
- Abdul Abas, Riad, et al.
(författare)
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Studies on Graphitisation of Blast Furnace Coke by X-ray Diffraction Analysis and Thermal Diffusivity Measurements
- 2005
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 77:11, s. 763-769
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Tidskriftsartikel (refereegranskat)abstract
- High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X-ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser-flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X-ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.
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| 2. |
- Andersson, Annika, et al.
(författare)
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A study of some elemental distributions between slag and hot metal during tapping of the blast furnace
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:5, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10-minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag-metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L-Mn and L-V, but an increased L-S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO2 was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.
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| 3. |
- Bohnenkamp, U., et al.
(författare)
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Evaluation of the density of steels
- 2000
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:3, s. 88-93
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Tidskriftsartikel (refereegranskat)abstract
- Data on physical properties of steels have been collected from the open literature and put into a database. The influence of composition on the density of steels has been analyzed. An overview over former studies is given. The steels have been investigated by regression analysis in two groups, i) ferritic and low alloy steels, and ii) austenitic steels. For ferritic steels two models are provided. The first model is based on the assumption that all C is bound in cementite and other solutes are insoluble in cementite, The second model employs the result of a thermodynamic analysis where the amount of cementite and the solubilities in ferrite and cementite were determined with computational thermodynamics. The non-linear effect of Cr and Mn in cementite was computed and regression analysis of the effect of solutes on the density of ferrite was performed. For Ti-stabilized austenitic steels, the amount of TiC and the solubilities were assessed in a thermodynamic analysis. The effect of solutes on the density of austenite was studied by regression analysis. For estimations of the density of steels containing components that are not covered by the regression analysis, the regression coefficients can be supplemented with literature data or theoretically determined values. The results obtained by the present regression analysis are: Cu and Mo increase the density of ferritic steels, and C, Cr, Mn, S, Si, and V decrease it. TiC. C, Cr, Mn, N, Si, and Ti reduce the density of austenitic steels and Cu, Co. Mo, and Ni increase it.
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| 4. |
- Bohnenkamp, U., et al.
(författare)
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Evaluation of the elastic modulus of steels
- 2000
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:3, s. 94-99
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Tidskriftsartikel (refereegranskat)abstract
- Literature data on the physical properties of steels have been collected and put into a database. The elastic modulus of steels has been analyzed as a function of composition. An overview over former studies is given. The steels have been investigated in three groups, martensitic and ferritic steels, ferritic steels separately, and austenitic steels. For the last two groups, a thermodynamic analysis with Thermo-Gale has been performed. Regression analysis on the influence of composition on the elastic modulus was then carried out. The results for ferritic steels reveal that cementite has no effect on the elastic modulus, whereas Cr, Mo, Si, Mn, and Cu increase it. The elastic modulus of austenitic steels is reduced by Ni and Mo and increased by N, NbC, TiC, and Cr. Cr23C6, while statistically significant in the analysis, has no effect on the elastic modulus of austenitic steels, The regression coefficients found can be used to predict the elastic modulus of steels with known composition.
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| 5. |
- Bohnenkamp, U., et al.
(författare)
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Evaluation of the electrical resistivity of steels
- 2000
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:10, s. 410-416
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Tidskriftsartikel (refereegranskat)abstract
- Literature data on the physical properties of sleets have been collected and put into a database. The resistivity of steers has been analyzed as a function of composition and microstructure. An overview over former studies is given. The steels have been investigated in two groups, ferritic steels and austenitic steels. A thermodynamic analysis with ThermoCalc has been performed. Regression analysis on the influence of composition on the resistivity was then carried out. The results for ferritic steels are: Si and Al have the highest elemental resistivity, followed by Mn. Cu, Ni, Mo, and Cr. C precipitated in cementite shows a high coefficient in the analysis when the amount of Fe bound in cementite is not considered separately. C in solution with ferrite shows no significant effect. Cr bound in cementite shows a significant effect but Mn, though present in cementite in comparable amounts, has no significant effect on the resistivity. N and C have the highest elemental resistivity in austenite, followed by the substitutional solutes Nb, Si, Ti, Cu, Ni, Mo, and Cr. The carbides NbC and Tic appear with a higher coefficient in the regression model than can be explained by phase-mixture models providing upper and lower bounds for the resistivity of two-phase alloys. Cr23C6 shows no significant effect. The regression results can be used to predict the resistivity of steels with known composition. The model predicts the resistivity of ferritic steels with a maximum deviation between experimental and computed value of 12 n Omegam and a standard deviation of 5.6 n Omegam. For austenitic steels, the model prediction shows a maximum deviation of 52 mu Omegam and a standard deviation of 20 n Omegam.
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| 6. |
- Brandberg, Jenny, et al.
(författare)
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Water capacity model of Al2O3-CaO-MgO-SiO2 quaternary slag system
- 2007
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 78:6, s. 460-464
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the present work was to develop a water capacity model for the quaternary slag system Al2O3-CaO-MgO-SiO2. In the model, a silicate melt was considered to consist of two ion groupings, viz. cation grouping and oxygen ion. The water capacity of a melt is supposed to depend on the interactions between the cations in the presence of oxygen ions. These interactions were determined on the basis of the experimentally measured water solubility data. Only binary interactions were employed in the model. For the system CaO-SiO2, disagreement in the literature data was found. Since the interaction between Ca2+ and Si4+ would play an important role, experiments were carried out to determine the water capacities of some CaO-SiO2 slags. For this purpose a thermogravimetric method was employed. Iso-lines of water capacities at constant MgO contents were predicted by the model and compared with the experimental data from literature. The model calculations agreed well with the experimental results.
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| 7. |
- Eliasson, J., et al.
(författare)
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Proof strength values for austenitic stainless steels at elevated temperatures
- 2000
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:07-jun, s. 249-254
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the alloying elements C, N, Si, Mn, Cr, Ni, Mo, Cu, Ti on proof strength is studied in the temperature range 20-550 degrees C. High temperature data for the proof strength of austenitic stainless steels have been analysed. Using computational thermodynamics the amount of alloying elements in solid solution and the volume fractions of precipitates were assessed. These quantities were then applied in a regression analysis for the high temperature strength. Quantitative relationships for the proof strength as a result of the regression analysis are proposed as a function of temperature. They are to be used in materials design. The interstitial elements showed the largest effect. Si, Ni and Mo increased the strength at all temperatures. Cu and Mn reduced the strength and Cr gave an influence, which varied with temperature.
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| 8. |
- Eriksson, Robert, et al.
(författare)
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An experimental study of the velocity field during filling of an ingot mould
- 2003
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 74:7, s. 423-430
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Tidskriftsartikel (refereegranskat)abstract
- In the present study the velocity field in a 1:3 scale water model of a 4.2-tonne ingot mould was determined using Laser Doppler Anemometry (LDA). The velocity was measured in the horizontal and vertical directions at several different locations along the centre plane of the model. The effect of different volumetric flow rates and water temperatures was also investigated. The reproducibility of the measurements was found to be satisfactory, since the mean velocity at any measurement location had an average difference of around 10% between two fillings. The effect of different volumetric flow rates showed that while decreasing the flow rate, the mean velocity at the bottom turned from an upward direction to a downward direction. At the top of the model the difference between the mean velocities for the different flow rates was less pronounced. An influence of the temperature on the mean velocity could be observed. However, further studies are required to verify this result.
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| 9. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some binary FeO-Containing slags
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:4, s. 240-246
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation, experimental measurements of the thermodynamic activities of iron oxide in the Al2O3-FeO, CaO-FeO and FeO-SiO2 systems were performed in the temperature range 1823-1873 K by using gas equilibration technique. The molten slag, kept in a Pt-crucible was brought to equilibrium with a gas mixture of known oxygen partial pressure. A part of the Fe from the FeO was reduced during the equilibration and got dissolved in the Pt phase. The samples were quenched after the required equilibration time and the slag phase as well as the platinum crucible was subjected to chemical analysis. The activities of FeO in the slag were calculated from the experimental data using thermodynamic information on the Fe-Pt binary metallic system generated and assessed earlier. The experimental results are compared with earlier thermodynamic studies of the slag systems. Reassessment with the KTH slag model is performed and the results are compared with other thermodynamic models, viz. F*A*C*T(TM) and Thermo-Calc(TM) respectively. The experimental activities predicted by the KTH slag model are in good agreement with the experimental data available in the literature. A general agreement between the various models is also observed.
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| 10. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some ternary FeO-containing slags
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:6, s. 357-365
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic data concerning FeO-containing slags is of importance in ladle refining of steel. With a view to generate a set of reliable and self-consistent thermodynamic data for these slags, experimental determination of the activities of iron oxide in the Al2O3-FeO-SiO2, CaO-FeO-SiO2 and FeO-MgO-SiO2 systems was carried out using the gas equilibration method involving CO-CO2-Ar gas mixtures in the temperature range 1823-1923 K. The slag samples kept in Pt crucibles were quenched after the equilibration and subjected to chemical analysis. The thermodynamic activities of FeO in the slags were calculated from the experimental data. The results are incorporated into a thermodynamic description of silicate melts developed in the present laboratory. The model is based on a Temkin-Lumsden approach and is able to compute the thermodynamics of higher order systems from the lower order ones. The model was updated with the present results and iso-activity contours of FeO in the three component systems are presented at 1873. The capacity of the model to predict the thermodynamic activites in four-, five-, and six-component slags is demonstrated in the case of steelmaking slags.
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