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Joo Hyun Park - One of the best experts on this subject based on the ideXlab platform.
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Synergistic Effect of Nitrogen and Refractory Material on TiN Formation and Equiaxed Grain Structure of Ferritic Stainless Steel
Metallurgical and Materials Transactions B, 2018Co-Authors: Joo Hyun ParkAbstract:The effect of nitrogen content on the formation of an equiaxed solidification structure of Fe-16Cr steel was investigated. Moreover, two different kinds of refractory materials, i.e ., alumina and magnesia, were employed to control the type of Oxide Inclusion. The characteristics of TiN(-Oxide) Inclusions were quantitatively analyzed in both molten steel and solidified samples. When the melting was carried out in the alumina refractory, the grain size continuously decreased with increasing nitrogen content. However, a minimum grain size was observed at a specific nitrogen content (approx. 150 ppm) when the steel was melted in the magnesia refractory. Most of the single TiN particles had a cuboidal shape and fine irregularly shaped particles were located along the grain boundary due to the microsegregation of Ti at the grain boundary during solidification. The type of TiN-Oxide hybrid Inclusion was strongly affected by the refractory material where Al_2O_3-TiN and MgAl_2O_4-TiN hybrid-type Inclusions were obtained in the alumina and magnesia refractory experiments, respectively. The formation of Oxide Inclusions was well predicted by thermochemical computations and it was commonly found that Oxide particles were initially formed, followed by the nucleation and growth of TiN. When the nitrogen content increased, the number density of TiN linearly increased in the alumina refractory experiments. However, the number of TiN exhibits a maximum at about [N] = 150 ppm, at which a minimum grain size was obtained in the magnesia refractory experiments. Therefore, the larger the number density of TiN, the smaller the primary grain size after solidification. The number density of TiN in the steel melted in the magnesia refractory was greater than that in the steel melted in the alumina refractory at given Ti and N contents, which was due to the lower planar lattice disregistry of MgAl_2O_4-TiN interface rather than that of Al_2O_3-TiN interface. When ∆ T _TiN (= difference between the TiN precipitation temperature and the liquidus of the steel) was 20 K to 40 K, the number density of effective TiN was maximized and thus, the grain size was minimized after solidification. Finally, although most of the TiN particles were smaller than 1 μ m in the molten steel samples irrespective of the nitrogen content, TiN particles larger than 10 μ m were observed in the solidified samples when the nitrogen content was greater than 150 ppm. The growth of TiN particles during melting and solidification was well predicted by the combinatorial simulation of the ‘Ostwald ripening model’ based on the Lifshitz–Slyozov–Wagner theory in conjunction with the ‘Diffusion controlled model’ using Ohnaka’s microsegregation equation.
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understanding viscosity structure relationship of slags and its influence on metallurgical processes
2018Co-Authors: Jin Gyu Kang, Joo Hyun ParkAbstract:The viscosity is one of the most critical properties of slags and thus its influence on the physicochemical phenomena in metallurgical processes has been issued for last decades. The viscosity of ferrous- and non-ferrous metallurgical slags can be understood via structural investigation with spectroscopic methodologies including x-ray photoelectron spectroscopy, infrared- and Raman spectroscopy, and solid state nuclear magnetic resonance spectroscopy, etc. Therefore, the reaction kinetics such as desulfurization in ladle metallurgical furnace, reduction of FeO and MnO in electric arc furnace is strongly dependent on the viscosity of the slags. The rates of Oxide (Inclusion and refractory) dissolution into the slags and fluxes are governed by the viscosity. Alternatively, the structure of aluminosilicate melts also affects the thermochemical properties such as sulfide capacity, etc. These diverse applications of the viscosity-structure relationship to ferrous- and non-ferrous metallurgical processes were reviewed.
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Modification of Inclusions in Molten Steel by Mg-Ca Transfer from Top Slag: Experimental Confirmation of the ‘Refractory-Slag-Metal-Inclusion (ReSMI)’ Multiphase Reaction Model
Metallurgical and Materials Transactions B, 2017Co-Authors: Jae Hong Shin, Joo Hyun ParkAbstract:High-temperature experiments and Refractory-Slag-Metal-Inclusion (ReSMI) multiphase reaction simulations were carried out to determine the effect of the ladle slag composition on the formation behavior of non-metallic Inclusions in molten steel. Immediately after the slag-metal reaction, magnesium migrated to the molten steel and a MgAl_2O_4 spinel Inclusion was formed due to a reaction between magnesium and alumina Inclusions. However, the spinel Inclusion changed entirely into a liquid Oxide Inclusion via the transfer of calcium from slag to metal in the final stage of the reaction. Calcium transfer from slag to metal was more enhanced for lower SiO_2 content in the slag. Consequently, the spinel Inclusion was modified to form a liquid CaO-Al_2O_3-MgO-SiO_2 Inclusion, which is harmless under steelmaking conditions. The modification reaction was more efficient as the SiO_2 content in the slag decreases.
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refractory slag metal Inclusion multiphase reactions modeling using computational thermodynamics kinetic model for prediction of Inclusion evolution in molten steel
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2017Co-Authors: Jae Hong Shin, Yongsug Chung, Joo Hyun ParkAbstract:The refractory–slag–metal–Inclusion multiphase reaction model was developed by integrating the refractory–slag, slag–metal, and metal–Inclusion elementary reactions in order to predict the evolution of Inclusions during the secondary refining processes. The mass transfer coefficient in the metal and slag phase, and the mass transfer coefficient of MgO in the slag were employed in the present multiphase reactions modeling. The “Effective Equilibrium Reaction Zone (EERZ) Model” was basically employed. In this model, the reaction zone volume per unit step for metal and slag phase, which is dependent on the ‘effective reaction zone depth’ in each phase, should be defined. Thus, we evaluated the effective reaction zone depth from the mass transfer coefficient in metal and slag phase at 1873 K (1600 °C) for the desulfurization reaction which was measured in the present study. Because the dissolution rate of MgO from the refractory to slag phase is one of the key factors affecting the slag composition, the mass transfer coefficient of MgO in the ladle slag was also experimentally determined. The calculated results for the variation of the composition of slag and molten steel as a function of reaction time were in good agreement with the experimental results. The MgAl2O4 spinel Inclusion was observed at the early to middle stage of the reaction, whereas the liquid Oxide Inclusion was mainly observed at the final stage of the refining reaction. The content of CaO sharply increased, and the SiO2 content increased mildly with the increasing reaction time, while the content of Al2O3 in the Inclusion drastically decreased. Even though there is slight difference between the calculated and measured results, the refractory–slag–metal multiphase reaction model constructed in the present study exhibited a good predictability of the Inclusion evolution during ladle refining process.
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Refractory–Slag–Metal–Inclusion Multiphase Reactions Modeling Using Computational Thermodynamics: Kinetic Model for Prediction of Inclusion Evolution in Molten Steel
Metallurgical and Materials Transactions B, 2017Co-Authors: Jae Hong Shin, Yongsug Chung, Joo Hyun ParkAbstract:The refractory–slag–metal–Inclusion multiphase reaction model was developed by integrating the refractory–slag, slag–metal, and metal–Inclusion elementary reactions in order to predict the evolution of Inclusions during the secondary refining processes. The mass transfer coefficient in the metal and slag phase, and the mass transfer coefficient of MgO in the slag were employed in the present multiphase reactions modeling. The “Effective Equilibrium Reaction Zone (EERZ) Model” was basically employed. In this model, the reaction zone volume per unit step for metal and slag phase, which is dependent on the ‘effective reaction zone depth’ in each phase, should be defined. Thus, we evaluated the effective reaction zone depth from the mass transfer coefficient in metal and slag phase at 1873 K (1600 °C) for the desulfurization reaction which was measured in the present study. Because the dissolution rate of MgO from the refractory to slag phase is one of the key factors affecting the slag composition, the mass transfer coefficient of MgO in the ladle slag was also experimentally determined. The calculated results for the variation of the composition of slag and molten steel as a function of reaction time were in good agreement with the experimental results. The MgAl_2O_4 spinel Inclusion was observed at the early to middle stage of the reaction, whereas the liquid Oxide Inclusion was mainly observed at the final stage of the refining reaction. The content of CaO sharply increased, and the SiO_2 content increased mildly with the increasing reaction time, while the content of Al_2O_3 in the Inclusion drastically decreased. Even though there is slight difference between the calculated and measured results, the refractory–slag–metal multiphase reaction model constructed in the present study exhibited a good predictability of the Inclusion evolution during ladle refining process.
James E. Castle - One of the best experts on this subject based on the ideXlab platform.
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The initiation of pitting corrosion of stainless steels at Oxide Inclusions
Corrosion Science, 1992Co-Authors: Mark Baker, James E. CastleAbstract:Abstract The initial stages of pit growth for stainless steel exposed in 0.5 M H 2 SO 4 + 0.5 M NaCl + 0.08% H 2 O 2 at the free corrosion potential for 10 s have been examined by Auger and simultaneous EDX mapping and electron microscopy. This investigation was focussed on pits which initiated at mixed Al/Ti/Mn/Cr Oxide Inclusions. Auger/EDX maps showed the strong presence of Al in corrosion deposits partially covering the pit, and traces of Mn and Ti in deposits adjacent to the Inclusions, indicating that these elements have been leached from the Inclusion. The reduction of pH within the pit has resulted in partial dissolution of the generally inert Oxide Inclusion. Activity-pH diagrams have been used to interpret the dissolution and redeposition of the Oxide Inclusion components.
Shi-yen Shiau - One of the best experts on this subject based on the ideXlab platform.
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dietary chromic Oxide Inclusion level required to maximize glucose utilization in hybrid tilapia oreochromis niloticus o aureus
Aquaculture, 1998Co-Authors: Shi-yen Shiau, Shwumei ShyAbstract:Abstract The purpose of this study was to elucidate the influence of dietary chromic Oxide (Cr 2 O 3 ) on glucose utilization and digestibility by hybrid juvenile tilapia. Eight levels of Cr 2 O 3 (0, 2, 10, 50, 100, 300, 1000 and 5000 mg/kg) were incorporated into the basal diet containing glucose as the carbohydrate source. Each of the eight diets was fed to triplicate groups of tilapia in a static rearing system for 8 weeks. Weight gain percentage was significantly ( P 2 O 3 /kg diet than in fish fed the other diets except for those fed the diet supplemented with 100 mg Cr 2 O 3 /kg. Feed efficiency ratio and protein efficiency ratio was better in fish fed the diet supplemented with 300 mg Cr 2 O 3 /kg compared to those fed diets supplemented with 10, 50 and 5000 mg Cr 2 O 3 /kg. Dry matter, lipid and protein digestibilities did not differ among dietary groups. Body ash contents were higher in fish fed diets with >100 mg Cr 2 O 3 /kg than in fish fed diets with 2 O 3 /kg. The dietary Cr 2 O 3 level that yielded maximum growth was 204 mg/kg based on a broken-line model estimation of weight gain.
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Carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus, are affected by chromic Oxide Inclusion in the diet.
The Journal of nutrition, 1995Co-Authors: Shi-yen Shiau, Hong-shiang LiangAbstract:A 12-wk feeding trial was conducted to study the influence of chromic Oxide (Cr2O3) on carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus. Two levels of chromic Oxide (0.5 and 2%) were each incorporated into diets containing glucose or starch. Chromic Oxide was added at 0 or 8 wk. The diets were fed to triplicate groups of fish weighing 1.11 +/- 0.05 g. Fish fed the starch diet had greater (P < 0.05) weight gain, feed efficiency ratio, protein efficiency ratio, protein deposition and digestibility of protein, lipid, carbohydrate and dry matter than fish fed the glucose diet irrespective of the time and level of chromic Oxide supplementation. Fish fed the glucose diet with 0.5% chromic Oxide had higher weight gain, feed efficiency ratio, protein efficiency ratio and protein deposition than fish fed the glucose diet with 2% chromic Oxide. The ingredient digestibility estimated using 0.5% chromic Oxide as the marker was greater than that estimated with 2% chromic Oxide. Higher phosphofructokinase and lower glucose-6-phosphatase activity was found in fish fed the starch diet than in fish fed the glucose diet regardless of the time and level of chromic Oxide Inclusion. Fish fed the glucose diet with 0.5% chromic Oxide had higher phosphofructokinase activity and lower tissue chromium concentration than fish fed the glucose diet with 2% chromic Oxide irrespective of chromic Oxide Inclusion time. These data suggest that the level of chromic Oxide in the diet alters glucose utilization by tilapia and affects nutrient digestibility by tilapia. The time of chromic Oxide Inclusion had no effect on carbohydrate utilization and digestibility.
Shwumei Shy - One of the best experts on this subject based on the ideXlab platform.
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dietary chromic Oxide Inclusion level required to maximize glucose utilization in hybrid tilapia oreochromis niloticus o aureus
Aquaculture, 1998Co-Authors: Shi-yen Shiau, Shwumei ShyAbstract:Abstract The purpose of this study was to elucidate the influence of dietary chromic Oxide (Cr 2 O 3 ) on glucose utilization and digestibility by hybrid juvenile tilapia. Eight levels of Cr 2 O 3 (0, 2, 10, 50, 100, 300, 1000 and 5000 mg/kg) were incorporated into the basal diet containing glucose as the carbohydrate source. Each of the eight diets was fed to triplicate groups of tilapia in a static rearing system for 8 weeks. Weight gain percentage was significantly ( P 2 O 3 /kg diet than in fish fed the other diets except for those fed the diet supplemented with 100 mg Cr 2 O 3 /kg. Feed efficiency ratio and protein efficiency ratio was better in fish fed the diet supplemented with 300 mg Cr 2 O 3 /kg compared to those fed diets supplemented with 10, 50 and 5000 mg Cr 2 O 3 /kg. Dry matter, lipid and protein digestibilities did not differ among dietary groups. Body ash contents were higher in fish fed diets with >100 mg Cr 2 O 3 /kg than in fish fed diets with 2 O 3 /kg. The dietary Cr 2 O 3 level that yielded maximum growth was 204 mg/kg based on a broken-line model estimation of weight gain.
John N. Dupont - One of the best experts on this subject based on the ideXlab platform.
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The influence of martensitic microstructure and Oxide Inclusions on the toughness of simulated reheated 10 wt% Ni steel weld metal multi-pass fusion zones
Materials Science and Engineering: A, 2021Co-Authors: Erin J. Barrick, John N. DupontAbstract:Abstract The influence of the effective grain size of the martensitic microstructure and the presence of Oxide Inclusions on the toughness of a novel high strength, high toughness 10 wt% Ni steel weld metal was investigated. Previously, it was determined that welds produced with the gas tungsten arc welding (GTAW) process exhibited superior toughness to those produced using gas metal arc welding (GMAW), and differences in the martensitic microstructure and Oxide Inclusion content were identified between the two welds. To elucidate the effect of these two microstructural constituents on toughness, multi-pass weld reheat simulations were performed using a Gleeble 3500 thermal-mechanical simulator designed to produce identical martensitic microstructures in GTAW and GMAW specimens. The GMAW reheat specimens contained a large presence of Oxide Inclusions from the use of a 98% Ar/2% O2 shielding gas used during welding, whereas the GTAW specimens exhibited a smaller quantity since 100% Ar was used as the shielding gas. These reheat experiments demonstrate that even when both welds have a fine martensitic microstructure, a known toughening mechanism, the toughness of the GMAW is still significantly lower than the GTAW. Thus, the Oxide Inclusions are the main influence in the lower toughness of the as-welded GMAW, and microstructural refinement is the secondary influence. However, the superior toughness of the GTAW is not only from the lower quantity of Oxide Inclusions, because when the effective grain size of the GTAW is coarse, the toughness is very low. Thus, both influences are necessary for high toughness of the as-welded GTAW. These results are significant in that they demonstrate the necessity of developing an oxygen-free shielding gas to improve the toughness of welds produced with the GMAW process. The results also now allow for welding procedures to be developed in such a way to avoid low toughness regions in welds produced with both processes, based on the scientific foundation that has been laid here.
