| 1. |
- Jakobsson, A., et al.
(författare)
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Interfacial phenomena in some slag-metal reactions
- 2000
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 31:5, s. 973-980
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the change of the interfacial tension at the slag-metal interface for sulfur transfer between molten iron, slag, and gas phases was monitored by X-ray sessile drop method in dynamic mode in the temperature range of 1830 to 1891 K. The experiments were carried out with pure iron samples immersed partly or fully in the slag phase. The slag consisted of 30 wt pet CaO, 50 wt pet Al2O3, and 20 wt pet SiO2 (alumina saturated at the experimental temperatures) with additions of FeO. Metal and slag samples contained in alumina crucibles were exposed to a CO-CO2-SO2-Ar gas mixture with defined oxygen and sulfur partial pressures, and the change of the shape of the metal drop was determined as a function of time. The equipment and the technique were calibrated by measurements of the surface tensions of the pure Cu, Ni, and Fe containing two different amounts of dissolved oxygen. A theoretical model was developed to determine the sulfur content of the metal as a function of time on the basis of sulfur diffusion in the slag and metal phases as well as surface tension-induced flow on the metal drop surface. Attempts were made to compute the interfacial tensions on the basis of force balance.
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| 2. |
- Allertz, Carl, et al.
(författare)
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A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment
- 2014
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 689-696
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Tidskriftsartikel (refereegranskat)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 and oxygen potentials at 1873K. The nitride capacities in the composition range studied were found to be very low. In accordance with the literature, the nitride capacity was found to increase with increasing SiO2 content. Industrial trials were performed. The nitrogen content of the steel was determined before and after vacuum degassing as well as after the waiting period. Three different trends of the variation of nitrogen content in the steel were observed. Both the laboratory study and the industrial trials revealed that the transfer of nitrogen from slag to steel was not the reason for nitrogen pickup in the steel subsequent to vacuum degassing.
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| 3. |
- Allertz, Carl, et al.
(författare)
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Effect of carbon on the solubility of nitrogen in slag
- 2015
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Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 106:8, s. 822-830
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Tidskriftsartikel (refereegranskat)abstract
- The effect of carbon on nitrogen solubility in slag was investigated for the ternary CaO-MgO-SiO2 and the quaternary Al2O3-CaO-MgO-SiO2 slag systems at 1 873 K under controlled oxygen and nitrogen potentials. Gas-slag equilibration experiments were conducted using molybdenum and graphite crucibles. In the absence of carbon, the nitrogen solubility was very low. The presence of carbon greatly increased the nitrogen solubility in slag. The total nitrogen content was found to increase with SiO2 and MgO concentration for the carbon saturated slags. Low levels of cyanide were found by wet chemistry with considerable uncertainty. The results analyzed by different methods ruled out cyanide formation being the main reason for the large increase in nitrogen solubility in the presence of pure carbon.
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| 4. |
- Allertz, Carl, et al.
(författare)
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Nitrogen solubility and the effect of carbon in ladle slag at 1873 K
- 2015
-
Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 316-319
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Konferensbidrag (refereegranskat)abstract
- The solubility of nitrogen in ladle slag was determined at 1873K under controlled nitrogen and oxygen potentials. Gas- slag equilibrium experiments were conducted using molybdenum and graphite crucibles. In the absence of carbon, the nitrogen solubility was very low. The presence of carbon greatly increased the nitrogen solubility in the slag. Low levels of cyanide was detected by wet chemistry, with considerable uncertainty. Cyanide was ruled out as the main reason for the large increase of nitrogen in the presence of pure carbon. The nitrogen solubility was found to increase with increasing SiO2 content both in the absence and presence of carbon.
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| 5. |
- Allertz, Carl, et al.
(författare)
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Possibility of Sulfur Removal from Ladle Slag by Oxidation in the Temperature Range 1373-1673 K
- 2015
-
Ingår i: Journal of Sustainable Metallurgy. - : Springer Science and Business Media LLC. - 2199-3823 .- 2199-3831. ; 1:3, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were conducted to investigate the possibility of removing sulfur from used ladle slag by oxidation. Slag samples (solid, two-phase mixture, and liquid with a small fraction of solid MgO particles) were subjected to an oxygen-rich atmosphere in the temperature range 1373–1673 K. The sulfur removal from the samples of solid and two-phase mixture was found to be a slow process due to the slow diffusion. The sulfur removal was found to have little dependence on temperature in the range 1373–1573 K. When the slag was mostly liquid (at 1673 K), the sulfur removal was significantly increased. More than 85 % of the sulfur could be removed after 60 min of oxidation in pure oxygen. An increase in oxygen partial pressure was found to increase the desulfurization slightly. Increasing the Al2O3 content in the slag decreased the degree of sulfur removal.
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| 6. |
- Allertz, Carl, et al.
(författare)
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Sulfide Capacity in Ladle Slag at Steelmaking Temperatures
- 2015
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 46:6, s. 2609-2615
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Tidskriftsartikel (refereegranskat)abstract
- Sulfide capacity measurements were conducted at 1823 K and 1873 K (1550 degrees C and 1600 degrees C) for the quaternary Al2O3-CaO-MgO-SiO2 system, for typical compositions used in the ladle in steelmaking. A copper-slag equilibrium was used under controlled oxygen and sulfur potentials. The sulfide capacity is strongly dependent on the composition and it was found to increase with the basic oxides, while it decreases with increase of the acidic components. It was found that CaO is more effective in holding sulfur in the slag compared to MgO when replacing SiO2. For the present slag compositions, Al2O3 and SiO2 behaved similar with respect to sulfur, and no considerable effect could be recorded when replacing one for the other. The sulfide capacity was also found to be strongly dependent on the temperature, increasing with temperature. The present results were compared with industrial data from the ladle, after vacuum treatment, and they were in good agreement.
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| 7. |
- Allertz, Carl
(författare)
-
Sulfur and nitrogen in ladle slag
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present work deals with some aspects of slags related to secondary metallurgy in the steelmaking process. More specifically the focus is given to sulfur and nitrogen in ladle slags. Even though slags have been fairly well-researched in the past, the available data for these elements in typical ladle slag compositions is rather scarce. In some cases the available data is in discordance. There are also inconsistencies between the literature data and what is commonly observed in the industrial processes.Sulfide capacities were measured at steelmaking temperatures, 1823–1873 K, in ladle slags. The data was found to be in reasonable agreement with the industrial process norms. The sulfide capacity was found to increase with the basic oxides CaO and MgO; and decrease with the acidic components Al2O3 and SiO2. The sulfide capacity was also found to increase with temperature.The dependence of sulfide capacity on the oxygen partial pressure, for slags containing multivalent elements, was investigated experimentally at 1873 K with a slag containing vanadium oxide. A strong dependence of oxygen partial pressure was observed. The sulfide capacity increase by more than two orders of magnitude when the oxygen partial pressure was increased from 4.6×10-16 atm to 9.7×10-10 atm.The nitrogen solubility and the effect of carbon was investigated in typical ladle slags and the CaO–MgO–SiO2 system at 1873 K. Carbon increases the nitrogen solubility substantially. In the absence of carbon, the nitrogen solubility is extremely low. Low concentrations of cyanide was detected in the carbon saturated slag. This was much lower than the total nitrogen content and formation of cyanide cannot explain the large increase.The possibility of removing sulfur with oxidation from used ladle slag was investigated experimentally at 1373–1673 K. The sulfur removal of mostly solid slag was found to be a slow process, and would not suitable for industrial practice. At 1673 K the slag was mostly liquid and more than 85% of the sulfur was removed after 60 min of oxidation in pure oxygen atmosphere.
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| 8. |
- Allertz, Carl, et al.
(författare)
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The Effect of Oxygen Potential on the Sulfide Capacity for Slags Containing Multivalent Species
- 2016
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 47:5, s. 3039-3045
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Tidskriftsartikel (refereegranskat)abstract
- The dependence of sulfide capacity on the oxygen partial pressure for slags containing multivalent species was investigated experimentally using a slag containing vanadium oxide. Copper-slag equilibration experiments were carried out at 1873 K (1600 A degrees C) in the approximate oxygen partial pressure range 10(-15.4) to 10(-9) atm. The sulfide capacity was found to be strongly dependent on the oxygen potential in this slag system, increasing with the oxygen partial pressure. The sulfide capacity changed by more than two orders of magnitude over the oxygen partial pressure range. The effect of changing oxygen partial pressure was found to be much greater than the effect of changing slag composition at a fixed oxygen partial pressure.
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| 9. |
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| 10. |
- Andersson, Emma, et al.
(författare)
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The Effect of CaF2 in the Slag in Ladle Refining
- 2009
-
Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 80:8, s. 544-551
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Tidskriftsartikel (refereegranskat)abstract
- Industrial experiments were conducted in ladle treatment at SSAB Oxelosund aiming at a reduction and even elimination of CaF2 as a component in synthetic slag formers. The effects of the presence of CaF2 on sulphur refining, lining wear as well as types and amount of inclusions were examined. The results of the plant trials indicated that the new slag without CaF2 had enough capacity for sulphur removal. On the other hand, the presence of CaF2 as a flux in the slag resulted in profound lining wear. It was also found that both the number and the types of non-metallic inclusions were not affected by the elimination of CaF2 from synthetic slag. The origins of different types of inclusions were also analysed on the basis of the experimental results. The analysis supported the finding that the presence of CaF2 had little effect on inclusions.
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| 11. |
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| 12. |
- Aune, Ragnhild, E, 1965-, et al.
(författare)
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A Galvanic Cell Study Of the Ni-W-O System in the Temperature Range 1034-1317 K
- 1994
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Ingår i: Journal of Chemical Thermodynamics. - : Elsevier BV. - 0021-9614 .- 1096-3626. ; 26:5, s. 493-505
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies of the standard molar Gibbs free energy of formation of NiWO4 have been carried out using a solid-state galvanic cell involving (zirconium oxide + calcium oxide) electrolyte in the temperature range T = 1034 K to 1317 K. The galvanic cell used can be represented as -Pt|{(1 - δ)Ni + δW}(f.c.c.), NiWO4(s), WO2.72(s)|(1 - x)ZrO2 + x CaO|NiO(s), Ni(s)|Pt+, where δ « 1. The e.m.f. against temperature plot shows a break at T ≈ 1167 K, indicating a possible phase transformation occurring in the ternary mixture. These studies were complemented by X-ray-diffraction studies of some ternary mixtures equilibrated at T = 1073 K and 1273 K. A thermodynamic assessment of (nickel + tungsten + oxygen) was carried out as part of the present work, incorporating the present results along with those available in the literature for the ternary as well as the three binaries involved. The isothermal sections at T = 1073 K and 1273 K are presented.
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| 13. |
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| 14. |
- Aune, Ragnhild, E, 1965-, et al.
(författare)
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Phase Relationships in the System Mn-Co-C
- 1997
-
Ingår i: The Japan Society of Calorimetry and Thermal Analysis - Netsu Sokutei. ; 24:4, s. 171-178
-
Tidskriftsartikel (refereegranskat)
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| 15. |
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| 16. |
- Berg, Martin, et al.
(författare)
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Effect of Aluminum on the Solubility of Calcium in Liquid Iron at Low Calcium and Aluminum Contents
- 2020
-
Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 60:1, s. 190-192
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Tidskriftsartikel (refereegranskat)abstract
- The solubility of calcium in liquid iron as a function of aluminum content and calcium potential, at compositions relevant to production of aluminum killed steels, was studied experimentally at 1 873 K. The measurements were made using a closed molybdenum chamber in which iron-aluminum alloys were held. The calcium potential was fixed using pure liquid calcium held at different temperatures. The calcium contents in the iron varied between 6 and 22 ppm by weight and the aluminum contents varied between 70 and 1 900 ppm by weight. The results indicate that the effect of aluminum on the solubility of calcium in iron is very low in the composition ranges studied.
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| 17. |
- Berg, Martin, et al.
(författare)
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Partitioning of Calcium Between Liquid Silver and Liquid Iron
- 2018
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : SPRINGER. - 1073-5615 .- 1543-1916. ; 49:3, s. 949-952
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Tidskriftsartikel (refereegranskat)abstract
- The partitioning of calcium between liquid silver and liquid iron at 1823 K and 1873 K (1550 degrees C and 1600 degrees C) was studied experimentally using a closed molybdenum container. The calcium potential in the container was controlled by the composition of the alloys in equilibrium. The results agreed well with previous experimental measurements and indicated that the effect of temperature was not very pronounced in the temperature range studied.
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| 18. |
- Berg, Martin, et al.
(författare)
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Study on the Equilibrium Between Liquid Iron and Calcium Vapor
- 2017
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : SPRINGER. - 1073-5615 .- 1543-1916. ; 48:3, s. 1715-1720
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Tidskriftsartikel (refereegranskat)abstract
- The solubility of calcium in liquid iron at 1823 K and 1873 K (1550 A degrees C and 1600 A degrees C) as a function of calcium potential was studied experimentally. The measurements were performed using a closed molybdenum holder in which liquid calcium and liquid iron were held at different temperatures. The results indicate a linear relationship between the activity of calcium, relative to pure liquid calcium, and the mole fraction of dissolved calcium in liquid iron, with a negligible temperature dependency in the ranges studied. The activity coefficient of calcium in liquid iron at infinite dilution, was calculated as 1551.
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| 19. |
- Beskow, Kristina, et al.
(författare)
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A new approach for the study of slag-metal interface in steelmaking
- 2006
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 33:1, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The main focus of the present work was to develop a sampler to obtain the physical description of the slag-metal interface in the presence of bulk flow. Industrial trial experiments were carried out in the ladles at Uddeholm Tooling, Hagfors, Sweden using the designed sampler. Samples of the slag-metal interface were successfully taken in both gas stirring and induction stirring modes. The similarities of the appearance as well as the micrographs of the samples suggested that the slag-metal interfaces in the two stirring modes were very similar except in the open eye area. In the case of both stirring modes, metal droplets were found in the slag bulk. On the other hand, no appreciable amount of slag was detected in the metal bulk. Further systematic investigation using a large number of samples is required to obtain a quantitative description of the interface.
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| 20. |
- Beskow, Kristina, et al.
(författare)
-
A new approach for the study of slag-metal interface in steelmaking
- 2006
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 33:1, s. 74-80
-
Tidskriftsartikel (refereegranskat)abstract
- The main focus of the present work was to develop a sampler to obtain the physical description of the slag-metal interface in the presence of bulk flow. Industrial trial experiments were carried out in the ladles at Uddeholm Tooling, Hagfors, Sweden using the designed sampler. Samples of the slag-metal interface were successfully taken in both gas stirring and induction stirring modes. The similarities of the appearance as well as the micrographs of the samples suggested that the slag-metal interfaces in the two stirring modes were very similar except in the open eye area. In the case of both stirring modes, metal droplets were found in the slag bulk. On the other hand, no appreciable amount of slag was detected in the metal bulk. Further systematic investigation using a large number of samples is required to obtain a quantitative description of the interface. © 2006 Institute of Materials, Minerals and Mining.
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| 21. |
- Beskow, Kristina, et al.
(författare)
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Impact of slag-refractory lining reactions on the formation of inclusions in steel
- 2004
-
Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:6, s. 514-518
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Tidskriftsartikel (refereegranskat)abstract
- The present study was carried out to investigate the impact of slag-refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.
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| 22. |
- Beskow, Kristina, et al.
(författare)
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Ladle glaze : major source of oxide inclusions during ladle treatment of steel
- 2004
-
Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:5, s. 393-400
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Tidskriftsartikel (refereegranskat)abstract
- Samples of ladle lining covered by glaze were taken from industrial ladles of different ages at Uddeholm Tooling AB, Hagfors, Sweden. It was found in the samples taken at and below the slag line that a slag infiltrated layer was covered by an outer layer containing many MgO 'islands' of various sizes. The microstructure of the infiltrating slag was the same as the matrix of the outer layer. The slag was found to decompose into the compound 3CaO. Al2O3 and a liquid phase during the cooling process. The former phase along with tiny MgO particles from the ladle glaze was found to be one of the major sources of inclusions during the degassing and flotation periods of ladle treatment. Thermodynamic analysis indicated that the reaction between the ladle glaze and the slag from the electric arc furnace resulted in the formation of MgO-Al2O3 spinel and an oxide solution, which were also the main inclusions found at the initial stages of ladle treatment. Evidence of this reaction was found in the lining samples taken above the slag line.
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| 23. |
- Beskow, Kristina, et al.
(författare)
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Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle
- 2001
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 32:2, s. 319-328
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the deoxidation of liquid steel with aluminum wire injection in a gas-stirred ladle was studied by mathematical modeling using a computational fluid dynamics (CFD) approach. This was complemented by an industrial trial study conducted at Uddeholm Tooling AB (Hagfors, Sweden). The results of the industrial trials were found to be in accordance with the results of the model calculation. In order to study the aspect of nucleation of alumina, emphasis was given to the initial period of deoxidation, when aluminum wire was injected into the bath. The concentration distributions of aluminum and oxygen were calculated both by considering and not considering the chemical reaction. Both calculations revealed that the driving force for the nucleation of Al2O3 was very high in the region near the upper surface of the bath and close to the wire injection. The estimated nucleation rate in the vicinity of the aluminum wire injection point was much higher than the recommended value for spontaneously homogeneous nucleation, 10(3) nuclei/(cm(3)/s). The results of the model calculation also showed that the alumina nuclei generated at the vicinity of the wire injection point are transported to other regions by the flow.
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| 24. |
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| 25. |
- Brandberg Hurtig, Jenny, et al.
(författare)
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Hydrogen pick-up after vacuum degassing
- 2015
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:1, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- The present work aimed at determining the major source for hydrogen pick-up of the steel after vacuum degassing but before casting. Samples of slag and metal were taken at different stages during ladle treatment at SSAB. Hydrogen increase after vacuum treatment was observed. Moisture contents of the industrial slags were analysed and their water capacities were calculated. It could be seen that the hydrogen increase was correlated to the amount of moisture in the slag and the water capacity. The study showed that the slag containing most water was also the heat having the largest hydrogen increase. The slag with most water had the highest water capacity. It could be concluded that the major source for hydrogen increase after degassing was due to the slag-metal reaction.
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| 26. |
- Brandberg, Jenny, 1975-
(författare)
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Solubility of hydrogen in slags and its impact on ladle refining
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the present work was to clarify the mechanisms of hydrogen removal during vacuum degassing. The main reason for this was because the primary source of hydrogen pick-up in steel-making is the moisture in the furnace atmosphere and the raw material charged into the ladle furnace. Previous studies showed that the presence of hydroxyl ions in the ladle slag results in hydrogen transfer from the slag back into the steel bath. The main focus of this thesis was therefore to gain deeper knowledge of the ladle slag and its properties. For this purpose a number of slag compositions were examined in order to clarify whether these slags were single liquids at 1858 K. 14 out of 27 compositions in the Al2O3 CaO MgO SiO2 system was completely melted. These results were in disagreement with the existing phase diagrams.Water solubility measurements were carried out by employing a thermo gravimetric technique. The temperature was found to have negligible effect on the water solubilities. The experimental results showed that the water capacity values varied between 1x103 and 2x103 in the majority of the composition range. However, for compositions close to CaO saturation the water capacity value could reach higher than 3x103. The experimental determined water capacity was further used to develop a water capacity model for the quaternary slag system Al2O3 CaO MgO SiO2. The model was constructed by considering the affects of the binary interactions between the cations in the slag on the capacity of capturing hydroxyl ions. The model calculations agreed well with the experimental results as well as with the literature data.An attempt was made to develop a preliminary process model for dehydrogenation by using the results from CFD calculation. For this purpose industrial sampling was made during vacuum treatment. The hydrogen concentrations decreases fast in the initial stages of the degassing, but is slowed down in the final stage. The model calculations fit the initial stage of the dehydrogenation process well. In the final stage of the process the predicted values are somewhat lower than the plant data. The results from the model prediction showed that a dynamic process model could be satisfactorily constructed using the results from CFD calculation.The present work aimed at determining how big impact hydroxyl ions in the slag have on the final hydrogen concentration in the liquid steel. It was found that the effect is of less importance regarding the final concentration of the metal after the degassing treatment.
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| 27. |
- 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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| 28. |
- Brandberg, Jenny, et al.
(författare)
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Water vapor solubility in ladle-refining slags
- 2006
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 37:3, s. 389-393
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Tidskriftsartikel (refereegranskat)abstract
- A thermo-gravimetric technique was used to determine the hydrogen solubilities of some Al2O3-CaO-MgO-SiO2 quaternary slags. The focus of the work was to determine the water capacities in slags having lower SiO2 concentrations, which were relevant to industrial practices. The majority of the experiments were carried out in the temperature interval 1747 to 1827 K with water pressure of 157 mbar. The reliability of the experiments was confirmed using a quenching technique. The temperature was found to have a negligible effect on the water solubilities. The composition of the slag did not seem to significantly affect the water capacity. However, as the slag composition approached CaO saturation, a considerable increase of the solubility was noticed.
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| 29. |
- Bustnes, J. A., et al.
(författare)
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Investigation of the kinetics of reduction of manganese tungstate by hydrogen
- 2000
-
Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 29:4, s. 151-155
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Tidskriftsartikel (refereegranskat)abstract
- The present work was carried out as a part of a research program studying the reduction kinetics of some transition metal tungstates. Manganese tungstate was reduced by hydrogen under isothermal conditions in the temperature range 883-1183 K. The reaction was round to take place in a single step with MnO and W as the solid products. The activation energy for the reduction of manganese tungstate was evaluated to be 92 kJ mol(-1) using the initial reaction rates. This activation energy was compared with the activation energies of the other transition metal tungstates in the light of bond strength of the metal-oxygen bonds.
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| 30. |
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| 31. |
- Condo, Adolfo Firmino Timoteo, 1976-, et al.
(författare)
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Experimental Determination of Sulphide Capacities of Blast Furnace Slags with Higher MgO Contents.
- 2017
-
Ingår i: IRONMAKING & STEELMAKING. - : Taylor & Francis. - 0301-9233 .- 1743-2812.
-
Tidskriftsartikel (refereegranskat)abstract
- Sulfide capacity measurements of slag with MgO content up to 18 mass% were carried out at 1713, 1743 and 1773 K to obtain reliable data for the blast furnace process. In the measurement, slag is equilibrated with copper at controlled oxygen partial pressure for 24h. The sulfide capacities are calculated based on the sulfur analyses for both slag and copper.
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| 32. |
- Condo, Adolfo Firmino Timoteo
(författare)
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Study of Sulfide Capacity of Slag and Sulfur Removal from Hot Metal
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present study aims at investigating the desulfurization process in hot metal and sulfide capacity of slags. The missing experimental data of sulfide capacities in Al2O3-CaOMgO-SiO2 system at 1713 K, 1743 K, 1773 K, 1823 K, 1873 K and in the Al2O3-CaO-SiO2 system at 1873 K were investigated under wellcontrolled oxygen potentials. These data along with the reliable and accurate data carefully selected from the literature were employed for KTH model optimization. The model was successfully optimized and produced good predictions of sulfide capacity between 1700 K and 1873 K for all liquid slags in the Al2O3-CaO-MgO-SiO2 system, especially for ladle slags and blast furnace slags, with an average relative deviation of approximately 15%. The partition of sulfur in the blast furnace at tapping was investigated. The results of re-melted slag and hot metal at temperatures of 1743 K and 1773 K showed that the two phases were not in equilibrium with respect to sulfur at tapping. Furthermore, about 30 min was required to reach equilibrium. The optimum equilibrium sulfur partition in the range of blast furnace slag was determined using sulfide capacity data calculated with the newly-optimized model. The results showed clearly that the best area which provides a good equilibrium sulfur partition is between 10 to 14 mass% MgO. The effect of aged CaC2 on the desulfurization of hot metal was investigated at 1673 K and 1773 K. The results show that the use of aged CaC2 does not have significant effect on the desulfurization process since all the samples used exhibited almost the same performance, despite being subject to different aging treatments. The possibility of re-sulfurization during the long waiting time in the transfer ladle before the BOF was investigated. From the results, II different solid phases were found present in the slag along with small portion of liquid slag. In addition, majority of sulfur in the slag is in the solid phase in the form of CaS, which is only a small fraction of the slag. The liquid slag and solid CaS was found to have a limited contact with the hot metal leading to very poor kinetics for re-sulfurization. Therefore, the amount re-sulfurization that is observed in the transfer ladle was found to be very low.
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| 33. |
- Condo, Adolfo Firmino Timoteo, et al.
(författare)
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Study on the Effect of Aging on the Ability of Calcium Carbide for Hot Metal Desulfurization
- 2016
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 87:9, s. 1137-1143
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Tidskriftsartikel (refereegranskat)abstract
- Industrial trials and laboratory study are carried out to investigate the effect of aging on the ability of CaC2 in hot metal desulfurization. The industrial trials indicate that the time of storage of calcium carbide within the limit of industrial practice has no appreciable effect on its ability of desulfurization. In the laboratory, samples of CaC2 are prepared by exposing them in air for different times to promote formation of a Ca(OH)(2) outer layer. The thickness of Ca(OH)(2) increases with exposing time. Thereafter, the aged CaC2 samples are employed for desulfurization at 1673 and 1773 K for 8 min. For all the samples after desulfurization, layers of graphite and CaO are found between the remaining CaC2 particles and the outer CaS layer. The desulfurization using CaC2 is found to proceed by the diffusion of calcium vapor through the product layers and then its reaction with dissolved sulfur in the hot metal at the surface. No appreciable difference in the thickness of the CaS layer is found with the samples exposed to air for different times. This finding explains well the industrial results.
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| 34. |
- Condo, Adolfo Firmino Timoteo, et al.
(författare)
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Study on the Equilibrium of Slag and Hot Metal at Tapping with Respect to Sulfur
- 2017
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Ingår i: Steel Research International. - : Wiley. - 1869-344X .- 1611-3683. ; 88:6, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The blast furnace slag and hot metal were collected from the industrial trials. The collected slag and hot metal samples are re-melted in a graphite crucible and stirred to investigate the sulfur partition at different stirring times. The experimental oxygen potential is well controlled to simulate the blast furnace conditions. The results show evidently that sulfur is transferred from hot metal to slag, which led to an increase in the sulfur partition from its initial value (t=0 min) of 26 -33 at 1743 K, and from 23 to 37 at 1773 K after 30 min of slag-metal reaction. The results strongly indicate non-equilibrium between slag and hot metal at tapping. The sulfide capacities of the slag with typical composition of the slag at tapping are determined. On the basis of the sulfide capacity data, the theoretical sulfur partition is evaluated. The theoretically calculated partition further supports the finding obtained in the stirring experiments. This finding would suggest the possibility of improvement to increase the usage of blast furnace slag in desulfurization.
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| 35. |
- Condo, Adolfo Firmino Timoteo, 1976-, et al.
(författare)
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Sulfide Capacities in the Al2O3-CaO-MgO-SiO2 System
- 2018
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 89:8
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the sulfide capacities of the slags in the ternary Al2O3-CaO-SiO2 system at 1873K, and in the quaternary system Al2O3-CaO-MgO-SiO2 at 1823 and 1873K are experimentally measured using copper-slag equilibrium at controlled oxygen partial pressure. The experimental data, which has been unavailable, are needed for the improvement of a sulfide capacity model. An assessment of the available data for sulfide capacities in the Al2O3-CaO-MgO-SiO2 system and its sub lower-order systems are made. Based on this assessment and the present experimental results, the model parameters of the existing sulfide capacity model are re-optimized. The sulfide capacity model can be successfully used in the prediction of the sulfide capacities of multicomponent slags with satisfactory accuracy.
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| 36. |
- Dahl, Fredrik, et al.
(författare)
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Characterization of melting of some slags in the Al2O3-CaO-MgO-SiO2 quaternary system
- 2006
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:4, s. 614-616
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Tidskriftsartikel (refereegranskat)abstract
- A number of slag compositions in the Al2O 3-CaO-MgO-SiO2 quaternary system was investigated. The Al2O3, CaO, and SiO2 oxide powders were calcinated at 1073 K for 24 hours before being mixed in an agate mortar. The oxide mixtures were further pressed into small pellets and sealed in a glass bottle. A horizontal platinum furnace and platinum crucibles were used and each slag composition was investigated four times to confirm the reproductibility of the process. Efforts were made to carry out the experiments with identical quenching speed. The slags were quenched from 1793 K to examine the liquidity of the slag samples at lower temperatures. It was revealed that the quenched samples were multi-phase mixtures instead of melting at the experimental temperature under the influence of the phase diagrams.
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| 37. |
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| 38. |
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| 39. |
- Dayal, P., et al.
(författare)
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Study of stag/metal interface in ladle treatment
- 2006
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 33:6, s. 454-464
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Tidskriftsartikel (refereegranskat)abstract
- In order to gain an insight into the mixing behaviour of slag and metal under different stirring conditions, samples of slag/metal interface were collected from an industrial 65 ton ladle furnace using a new sampling technique. Different stirring conditions and sampling positions in the ladle were chosen. Complementary cold model experiments were also performed. The experimental results strongly suggested that the shear force between the two liquids played an important role in slag-metal mixing. Evidence for the existence of slag droplets each surrounded by a very thin metal film was found in the samples taken under both gas stirred and induction stirred conditions. This observation strongly suggested that slag-metal system behaved similarly as oil-water system, wherein, the shear force owing to the bulk flow led to a packed 'sphere bed' of oil droplets each coated by a thin water film above the water bath. On the basis of the experimental results, preliminary mathematical models were developed to describe the rate of mass exchange at the slag/metal interface.
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| 40. |
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| 41. |
- Deng, Tengfei, et al.
(författare)
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Dissolution mechanism of dolomite in converter slag at 1873K
- 2014
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of dolomite dissolution in converter slag was studied and found to proceed by two steps: decomposition of dolomite into CaO and MgO and dissolution of the product into the slag. The first step was found to be controlled by heat transfer, which was confirmed by theoretical calculation. The decomposed dolomite had many pores, which allowed easy slag penetration. A discontinuous 2CaO.SiO2 layer along with MgO.Fe2O3 particles was found on the surface of the samples. Some 2CaO.SiO2 islands were found in the vicinity of the samples in the slag, revealing that the dissolution was dominated by peeling-off of the layer of 2CaO.SiO2- MgO.Fe2O3 mixture. 2CaO.SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite samples close to the surface. 2CaO.SiO2 phase was replaced gradually by 3CaO.SiO2 towards the centre of the decomposed sample. While addition of small amounts of dolomite directly into the slag could be considered in steelmaking converter, too much would result in slow dissolution and waste of the raw materials.
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| 42. |
- Deng, Tengfei, et al.
(författare)
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Dissolution of Lime in Synthetic 'FeO'-SiO2 and CaO-'FeO'-SiO2 Slags
- 2010
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:5, s. 347-355
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Tidskriftsartikel (refereegranskat)abstract
- Dissolution of different CaO samples into molten synthetic 'FeO'-SiO2 and 'FeO'-SiO2-CaO slags was carried out in a closed tube furnace at 1873K. The slag was kept stagnant. It was found that the dissolution rate was very fast when CaO rod was dipped into 'FeO'-SiO2 slag. In the case of 'FeO'-SiO2-CaO slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). Only less than 16 percent CaO reacted with the slag, irrespective of the type of lime. Three phase-regions were identified in the reacted part of the lime rod by SEM-EDS analysis. The formation of these regions was explained thermodynamically. A dense layer of 2CaO center dot SiO2 was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO center dot SiO2 layer would be of essence to obtain a high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag to reach a reliable conclusion regarding the relevance of the reactivity obtained by water ATSM test to the real reactivity of lime in high temperature slag.
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| 43. |
- Deng, Tengfei, et al.
(författare)
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Experimental Design for the Mechanism Study of Lime Dissolution in Liquid Slag
- 2012
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:3, s. 259-268
-
Tidskriftsartikel (refereegranskat)abstract
- The applicability of rotating rod technique in the study of lime dissolution in slag was investigated. Both computational fluid dynamic (CFD) and cold model experiments showed that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was long. The mass transfer by forced convection was also less important in comparison with natural convection and diffusion when the rod was half length of the height of the bath. This finding was in accordance with the criteria put forward by the original work that the method could only be applicable when a thin disk (instead of rod) with big diameter and big liquid bath were used. To study the lime dissolution by forced convection a new experimental technique was developed. A cube was placed in the slag that was eccentrically stirred. The whole system, viz. the sample along with the slag could be quenched. The new technique could study the effect of forced convection on the dissolution. The microscopic study on the quenched slag-lime samples could reveal the dissolution mechanism successfully.
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| 44. |
- Deng, Tengfei, et al.
(författare)
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Limestone Dissolution in Converter Slag at 1873 K (1600 degrees C)
- 2013
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 44:1, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- Decomposition and dissolution of limestone in slag at 1873 K (1600 A degrees C) were studied. The limestone samples were in the shape of cubes (11 mm x 11 mm x 11 mm approximately). The decomposition was carried out both in argon and in slag under argon atmosphere. In order to gain an insight into the phenomenon of slow decomposition, the decomposition process of CaCO3 was simulated using Comsol. The results showed evidently that the decomposition of calcium carbonate was controlled mostly by heat transfer. It was also found that the decomposition product CaO had very dense structure, whether the sample was decomposed in slag or in argon. The slow decomposition and the dense CaO layer would greatly hinder the dissolution of lime in the slag. The present results clearly indicate that the addition of limestone instead of lime would not be beneficial in the converter process.
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| 45. |
- Deng, Tengfei, et al.
(författare)
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Study of Lime Dissolution Under Forced Convection
- 2012
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 43:3, s. 578-586
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Tidskriftsartikel (refereegranskat)abstract
- Dissolution of different CaO cubes under force convection in liquid CaO-"FeO"-SiO2 slag was studied at 1873 K (1600 A degrees C). A linear relationship between normalized lengths and time was obtained after the experiment. It was evidently observed that the removal of the interface layer(s) including 2CaO center dot SiO2 by shear stress was the main mechanism for the dissolution. A stirring rate of approximately 100 rpm was found to be efficient to remove the interface layer(s). The limes with different structures had different dissolution rates.
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| 46. |
- Deng, Tengfei
(författare)
-
Study on the dissolution of lime and dolomite in converter slag
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the present study, the dissolution mechanism and rate of lime, limestone and dolomite in converter slag was studied. Lime dissolution in stagnant slag was studied first and dissolution of lime, limestone and dolomite under forced convection were carried out by new experimental setup.Dissolution of different CaO samples into stagnant converter slags was carried out in a closed tube furnace at 1873K. In the case of CaO-‘FeO’-SiO2 slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). A dense layer of 2CaO∙SiO2 was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO∙SiO2 layer would be of essence to obtain high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag.In order to obtain reliable information of lime dissolution under forced convection, the commonly used rotating rod method was examined. Both CFD calculation and cold model experiments showed evidently that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was centrally placed in a cylindrical container. A new experimental design was therefore developed. A cube was placed in the crucible and stirred by Mo rod along with slag. The whole system could be quenched in order to maintain the state of the system at high temperature. A linear relationship between normalized length and time was obtained for lime dissolution. Different lime samples showed big difference in dissolution rate. It was found that the main mechanism of CaO dissolution in slag was due to the removal of 2CaO∙SiO2 layer.Decomposition and dissolution of limestone and dolomite in slag at 1873 K were studied. The decomposition was carried out both in argon and in slag under argon atmosphere. The decomposition process was simulated using Comsol. The results showed evidently that the decomposition of limestone and dolomite was controlled mostly by heat transfer.It was also found that the decomposition of limestone product: CaO had very dense structure, no matter the sample was decomposed in slag or in argon. The slow decomposition and the dense CaO layer would greatly hinder the dissolution of lime in the slag. The present results clearly indicate that addition of limestone instead of lime would not be beneficial in converter process.Discontinuous 2CaO∙SiO2 layer along with MgO∙Fe2O3 particles was found on the surface of the dolomite sample. Some 2CaO∙SiO2 islands were found in the vicinity of the sample in the slag, which revealed therefore that the dissolution was dominated by the peeling-off of the layer of 2CaO∙SiO2-MgO∙Fe2O3 mixture. 2CaO∙SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite sample close to the surface. 2CaO∙SiO2 phase was replaced gradually by 3CaO∙SiO2 towards the centre of the decomposed sample.
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| 47. |
- Deng, Zhiyin, et al.
(författare)
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Attachment of Alumina on the Wall of Submerged Entry Nozzle During Continuous Casting of Al-Killed Steel
- 2016
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 47:3, s. 2015-2025
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of the formation of different attachments on the walls of submerged entry nozzle (SEN) were studied for the processes of Al-killed steel (Ca-treated, HSLA) and ultra-low carbon Al-killed steel (ULC). To understand the mechanism, the types of inclusions in the steel taken in tundish and in bloom (or slab) were identified. In the case of ULC, the reoxidation product, micro-alumina particles were found to be the source of attachment on the inner wall of the SEN. To avoid reoxidation of the steel by the top slag, removal of the slag could be considered in order to improve the situation. No attached layer was found on the outer surface of the SEN after casting of the ULC steel. In the case of HSLA steel, an attached layer composed of plate-like alumina crystals was found in some trials. The entrainment of oxygen through the mold powder due to improper operation would be the reason for the formation of this type of attachment. The formation of the plate-like crystals was discussed with the help of CFD calculation.
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| 48. |
- Deng, Zhiyin, et al.
(författare)
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Attachment of Liquid Calcium Aluminate Inclusions on Inner Wall of Submerged Entry Nozzle during Continuous Casting of Calcium-Treated Steel
- 2014
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 54:12, s. 2813-2820
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, inclusions in calcium-treated steel after RH treatment, in the tundish and in bloom were studied. Only two types of inclusions were detected in all steel samples, namely liquid calcium aluminate inclusions and inclusions of two phases with spinel in the center surrounded by the liquid calcium aluminate. The attachment of the inclusions on the inner surface of SEN was investigated for two types of refractory materials. The results indicated that liquid calcium aluminate inclusions could attach on the wall of SEN, when the refractory had big grain size and big cavities on the surface. On the other hand, tiny grain size and smooth surface of the SEN showed no attachment of the inclusions. The different behaviors of the two types of SEN were well explained using the results of flow calculation in the nozzle. The mechanism of the attachment was also discussed based on the experimental results and the CFD calculation. The tiny nodules formed on the surface of the inner nozzle due to inclusion attachment could be a source of macro inclusions.
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| 49. |
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| 50. |
- Deng, Zhiyin, et al.
(författare)
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Effects of Temperature and Holding Time on the Sintering of Ladle Filler Sand with Liquid Steel
- 2016
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 87:7, s. 921-929
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Tidskriftsartikel (refereegranskat)abstract
- In the present work the effects of temperature and holding time on the sintering of ladle filler sand are studied. Laboratory experiments are carried out using pellets made of chromite based filler sand and two steel grades containing different contents of Mn and Al. It is found that the liquid steel plays a major role in the sintering behavior. The results also show that the amount of liquid phase in the sintered sand pellets increases with the increase of temperature and holding time. The Al2O3 content increases substantially in the chromite phase (spinel), especially in the region close to the liquid phase, when the temperature is high enough or when the holding time is long enough. Higher content of dissolved Al would accelerate the formation of the alumina-rich chromite.
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