articles+ search results

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Traitement surface, Surface treatment, Tratamiento superficie, Oberflaechenbehandlung, Acier bas carbone, Low carbon steel, Acero bajo carbono, Kohlenstoffarmer Stahl, Acier non allié, Carbon steel, Acero no aliado, Unlegierter Stahl, Ductilité, Ductility, Ductilidad, Verformungsfaehigkeit, Durcissement déformation, Strain hardening, Endurecimiento deformación, Verfestigung, Durcissement précipitation, Precipitation hardening, Endurecimiento precipitación, Ausscheidungshaerten, Ecrouissage, Work hardening, Endurecimiento en frío, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété traction, Tensile property, Propiedad tracción, Zugeigenschaft, Précipitation, Precipitation, Precipitación, Ausscheidung, ductility, interphase precipitation, low carbon steel, precipitation strengthening, and work hardening

Tensile behavior and structure-property relationship of ferritic steels with nano-sized carbide dispersion were invesigated using Ti-added steel and Ti,Mo-added low carbon steels. By austenitizing followed by isothermal heat treatment at 700°C, polygonal ferrites containing very fine carbides of TiC and (Ti,Mo)C were obtained in the Ti-added and the Ti,Mo-added steels, respectively. The size of such carbides was finer in the Ti,Mo-added steel than in the Ti-added steel at the same isothermal holding. The results of tensile tests for these samples showed that the strength is higher as the carbide size is smaller. The structure-based strength calculation led to a good agreement with the experiments, when it was assumed that the Ashby-Orowan mechanism is dominant for precipitation strengthening of nano-sized alloy carbides. It was also suggested that a relatively large tensile ductility is related to enhanced recovery during the tensile deformation, accompanied with promotion of secondary slips or cross slips in a finer scale due to the nano-sized particles.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Haut fourneau, Blast furnace, Alto horno, Hochofen, Laitier haut fourneau, Blast furnace slag, Escoría alto horno, Hochofenschlacke, Scorie, Slag, Escoria, Schlacke, blast furnace slag, hydrate layer, hydrothermal reaction, and surface reaction

Hydrothermal treatment has various possibilities for adding value to blast furnace (BF) slag by forming hydroxide or hydrate crystals and introducing pores into the reaction product. To optimize the hydrothermal reaction process, understanding of the reaction behavior of BF slag during hydrothermal treatment is indispensable. In the present work, the mechanism of the hydrothermal reaction of BF slag was investigated by focusing on the reaction at the slag surface. The surface reaction behavior was reproduced using slag plate samples, which adjusted the effective amount of hot water participating in the reaction. The changes in the surface morphology of BF slag and synthesized CaO―SiO2―Al2O3(―MgO) slags during hydrothermal treatment at 250°C were examined. The reaction mechanism of BF slag as well as the effect of MgO on the reaction were discussed from the observed phenomena.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alumine, Alumina, Alúmina, Tonerde, Oxyde de bore, Boron oxide, Boro óxido, Boroxid, Oxyde de calcium, Calcium oxide, Calcio óxido, Calciumoxid, Scorie, Slag, Escoria, Schlacke, BaO-B2O3 addition, mineralogy, slag valorisation, and sulphide capacity

BaO and B2O3 were used to improve the metallurgical properties and valorisation potential of CaO-Al2O3 based top slag. The sulphide capacity of BaO-B2O3 modified CaO-Al2O3 based top slag was measured and compared with calculated values using the FactSage software. The effect of slag basicity (CaO + MgO)/(Al2O3 + B2O3) = 0.6-1.4 and BaO content on sulphide capacity was discussed. The mineralogy of the slag after experiments was observed. The crystallisation path of the slag during cooling was predicted based on a Scheil-Gulliver model. Consequently, the effect of the slag basicity and B2O3 on slag mineralogy and glass formation ability was discussed. It is found that the sulphide capacity is mainly influenced by slag basicity. BaO addition improves the slag sulphide capacity only for slag with low basicity (< 1.2). B2O3 addition enlarges the liquid region at 1 600°C but decreases the slag sulphide capacity. High basicity and B2O3 addition benefit the glass formation and would improve the slag valorisation potential in applications where the glass content is important.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alumine, Alumina, Alúmina, Tonerde, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Molekulardynamik, Oxyde de calcium, Calcium oxide, Calcio óxido, Calciumoxid, Oxyde de titane, Titanium oxide, Titanio óxido, Titanoxid, Scorie, Slag, Escoria, Schlacke, Silice, Silica, Sílice, Simulation, Simulación, Spectrométrie IR, Infrared spectrometry, Espectrometría IR, CaO―SiO2―Al2O3―TiO2, FT-IR, molecular dynamics, and structure

The structure information in the CaO-SiO2-14 mass% Al2O3―TiO2 slag was investigated by the molecular dynamics simulation and the FT-IR spectroscopy at 1 773 K. The influence of different additions of TiO2 and varying CaO/TiO2 ratios on the structure was studied to clarify the role of TiO2 in the slag. The results show that there exist three stable units, [SiO4] tetrahedron and [AlO4] tetrahedron as well as [TiO6] octahedron in the CaO-SiO2-14 mass% Al2O3―TiO2 slag. The average coordination numbers, CNSi―Al and CNAl―Al, are all approximately equal to 1 and are barely influenced by additions of TiO2 and varying CaO/TiO2 ratios, which indicates that both the [SiO4] and [AlO4] tetrahedrons are surrounded by only one [AlO4] tetrahedron and some other units. Nevertheless, [AlO4] can be linked by more than one [SiO4] tetrahedron but [SiO4] can only be surrounded by one [AlO4] tetrahedron. The bridging oxygen, classified into Si―O―Si, Al―O―Al and Si―O―Al, is preferentially localized in Si―O―Al. However, it is found a little violation of the so-called Al avoidance principle which states that the Al-O-Al linkage is absent have been obtained with about (less than) 5% Al―O―Al, and the bond of Al―O―Al is hardly affected by TiO2 additions. Replacement of CaO by TiO2 can only result in a slight change of the degree of polymerization, indicating TiO2 has the similar role as CaO to be a basic oxide.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Acier inoxydable, Stainless steel, Acero inoxidable, Nichtrostender Stahl, Fluorure de calcium, Calcium fluoride, Calcio fluoruro, Calciumfluorid, Scorie, Slag, Escoria, Schlacke, Spectrométrie Raman, Raman spectrometry, Espectrometría Raman, MAS-NMR, Raman spectroscopy, mould fluxes, stainless steel casting, and structure

During the production of titanium stabilized stainless steel, as titanium in steel has a tendency to reacting with SiO2 in mould fluxes to generate TiO2 into mould fluxes and mould powder can inevitably pick up Ti-bearing inclusions floating up from steel, TiO2 content in the molten mould fluxes gradually increases so that physiochemical properties of the fluxes change. To evaluate the effect of TiO2 increase in mould fluxes on the structure of the mould flux, the glassy slag system CaO-SiO2-CaF2-TiO2 for stainless steel casting fluxes was studied by combining Raman spectroscopy with 29Si and 19F Magic Angular spinning Nuclear Magnetic resonance (MAS-NMR) to obtain the structure information. Both Raman and 29Si MAS-NMR investigation results have shown that Q2 is predominant silicate species in structures of all samples. Ti4+ mainly exists in the form of [TiO4] in slag, and forms TiO2-like clusters with Ti4+ in tetrahedral coordination, which cannot change the degree of polymerization of the silicate network. A small amount of Ti enters into the silicate network as the role of network formation, which slightly enhances the degree of polymerization of the silicate network. According to 19F MAS-NMR spectra, most of the fluorine is exclusively coordinated by Ca2― corresponding to F―Ca(n) site and only a few Si-F bonds were observed in samples. Increase of TiO2 content has no significant effects on the F- bonds.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Défaut surface, Surface defect, Defecto superficie, Oberflaechenfehler, Extraction, Extracción, Machine, Máquina, Maschine, GLGOCM, GMGOCM, LSTWSVM, classification, feature extraction, strip steel, and surface defect

Feature extraction and classification are two important steps in the process of strip steel surface defect recognition. Traditional methods of defect feature extraction are not of scale and rotation invariance. Moreover, traditional methods of defect classification have a conflict between efficiency and accuracy in. In order to solve the above two problems, a novel recognition method is proposed in this paper. On one hand, the novel defect feature extraction scheme is realized by building sampling benchmark scale (SBS) information for training dataset and using gradient magnitude and gradient orientation co-occurrence matrix (GMGOCM), gray level and gradient orientation co-occurrence matrix (GLGOCM), and moment invariant features. On the other hand, K-nearest neighbor and R-nearest neighbor algorithms are used to prune training dataset, and amplification factors of pruned samples are used to improve least squares twin support vector machine (LSTWSVM) classifier in efficiency and accuracy. The experimental results show that the novel recognition method can not only realize defect feature extraction with scale and rotation invariance but also realize defect classification with high efficiency and accuracy.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Densité, Density, Densidad, Défaut surface, Surface defect, Defecto superficie, Oberflaechenfehler, Machine, Máquina, Maschine, SOR, TWSVM, multi-class classification, multi-density, strip steel, and surface defect

The strip steel surface defect classification belongs to multi-class classification. It demands high classification accuracy and efficiency. However, traditional methods are not fit for abnormal datasets, such as the large-scale, sparse, unbalanced and corrupted dataset. So a novel classification method is proposed in this paper based on enhanced twin support vector machine (TWSVM) and binary tree. According to the density information, the large-scale dataset is pruned, the sparse dataset is added with unlabeled samples, and TWSVM is improved to multi-density TWSVM (MDTWSVM) which has efficient successive over-relaxation (SOR) algorithm. Finally, MDTWSVM and binary tree are combined together to realize multi-class classification. Some experiments are done on the strip steel surface defect datasets with the proposed algorithm. Experimental results show that MDTWSVM has higher accuracy and efficiency than the other methods of multi-class classification for the strip steel surface defect.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Carbone, Carbon, Carbono, Kohlenstoff, Coke, Coque, Koks, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Scorie, Slag, Escoria, Schlacke, capillary force, carbonaceous bed, char, coke, ironmaking, and slag holdup

The static holdup of liquid slag in carbonaceous beds at high temperatures was studied using lab-scale experiments. The effects of particle size, type of carbonaceous materials, and slag composition on the static holdup of liquid slag were investigated. The particle diameter was found to be the most important factor determining the static holdup. From the experimental results, the empirical dimensionless correlation for the static holdup of liquid slag (Hs) in the carbonaceous beds was derived in terms of the modified capillary number (Cpm). Hs = 32.9 × C-0.562pm.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Elaboration acier, Steelmaking, Fabricación acero, Stahlherstellung, Oscillation, Oscilación, cavity mode, cavity oscillation, penetrating mode, splashing, steelmaking, and waves

In oxygen steelmaking, splashing from the injection of oxygen plays an important role in the kinetics of the process. Though waves inside the cavity and formation of various modes (i.e. dimpling, splashing, and penetrating) have been investigated in the past, it is not clearly understood how these wave behaviour affects splashing. Therefore, in the present work, a cold model experimental study has been carried to establish if it was possible to quantitatively identify various modes of cavity. Fast Fourier Transform (FFT) on cavity depth oscillation showed that amplitude and frequency of cavity oscillation is highest in penetrating mode. Important aspects of the droplet generation process were identified from high speed imaging. Formation of sheet structure was identified and the height of these structures above the bath surface were found to decline as the cavity mode changed from splashing to penetrating. Existence of the splash sheets emphasizes that the sampling position can be a crucial issue in interpreting plant studies.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Abrasion, Abrasión, Air, Aire, Luft, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Haut fourneau, Blast furnace, Alto horno, Hochofen, Laitier haut fourneau, Blast furnace slag, Escoría alto horno, Hochofenschlacke, Microstructure, Microestructura, Mikrogefuege, Porosité, Porosity, Porosidad, Porositaet, Propriété mécanique, Mechanical properties, Propiedad mecánica, Résistance usure, Wear resistance, Resistencia al desgaste, Verschleissfestigkeit, Scorie, Slag, Escoria, Schlacke, Solidification, Solidificación, Erstarren, Tribologie, Tribology, Tribología, Usure abrasive, Abrasive wear, Desgaste abrasivo, Abrasivverschleiss, Vitesse refroidissement, Cooling rate, Velocidad enfriamiento, Abkuehlungsgeschwindigkeit, abrasion resistance, air-cooled blast furnace slag, coarse aggregate, cooling rate, pavement, porosity, and solidification

The solidification conditions to reduce the porosity of air-cooled blast furnace slag were investigated. From cross-sectinal observation of solidified slag, growth of gas bubble generated in molten slag was estimated to be cause of high porosity. With low thermal conductivity slag, increasing the cooling rate by thin slag casting was effective for reducing the porosity of air-cooled blast furnace slag. As a method of reducing the porosity of air-cooled blast furnace slag, a process was developed in which the slag is solidified to a plate thickness of 20-30 mm in about 2 minutes by pouring the molten slag in a cast steel mold. When porosity reduced, the abrasion resistance of the slag improved. The possibility of using low porosity slag as aggregate for drainage pavement was confirmed in an experiment with test pavement.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Brame, Slab, Zamarra, Bramme, Elaboration acier, Steelmaking, Fabricación acero, Stahlherstellung, Modélisation, Modeling, Modelización, mixed integer linear programming, scatter search, scenario-based modeling approach, slab allocation, and stochastic optimization

A common problem encountered in steel companies is that of allocating the surplus slabs to customer orders so as to minimize the total cost of production and inventory. Due to many unpredictable events arising in practical manufacture environment, slab yields and customer demands are full of uncertainties. This paper focuses on such uncertainties and studies the stochastic version of the slab allocation problem that has received little attention in the literature. Using a scenario-based approach, we formulate the problem as a mixed integer linear programming (MILP) model. To make the MILP model more concision, we reformulate it with less variables and constraints by using a scenarios aggregation approach. The commercial optimization software such as IBM ILOG CPLEX can solve the model to optimality for small and medium scale instances, but fail to solve large scale instances to optimality. Thus, a scatter search algorithm with directed local search based on follow-up technique is proposed to solve the problem approximately. Moreover, we introduce a random perturbation strategy to avoid search process being tapped in local optimum. Computational results on randomly generated instances show that the proposed algorithm is effective.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Transformation de matériaux métalliques, Production techniques, Métallurgie des poudres. Matériaux composites, Powder metallurgy. Composite materials, Métaux et alliages frittés. Cermets, Sintered metals and alloys. Pseudo alloys. Cermets, Boulette, Pellet, Bolita, Efficacité, Efficiency, Eficacia, Wirkungsgrad, Elaboration acier, Steelmaking, Fabricación acero, Stahlherstellung, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Frittage, Sintering, Sinterización, Sintern, Haut fourneau, Blast furnace, Alto horno, Hochofen, Minerai fer, Iron ore, Mineral hierro, Eisenerz, Métallurgie poudre, Powder metallurgy, Metalurgia polvo, Pulvermetallurgie, Rendement énergétique, Energetic efficiency, Rendimiento energético, blast furnace, energy, integrated steelmaking, iron ore, pellets, and sinter

The role of ferrous raw materials and iron ore agglomeration in energy consumption of integrated steelmaking has been evaluated using a system-wide model. Four steelplant cases were defined: typical European steelplant with sinterplant; Nordic steelplant with sinterplant; European steelplant with sinter:pellet ratio of 50%, and Nordic steelplant charging pellets and a small amount of briquettes. Energy consumption in the mining system were estimated from published statistics at 150 MJ/t for lump ore and sinter fines, 650 MJ/t for pellets made from magnetite and 1 050 MJ/t for pellets made from hematite. An integrated steelplant model including all major unit operations was used to calculate overall system energy consumption from iron ore mining to hot rolled coil. Adjustments were made accounting for energy benefit of ground granulated blast furnace slag in cement production, energy required for cement production required for briquetting, and excess BF and BOF gas producing electricity in a 32% efficient power plant. The system-wide net adjusted energy in the first three steeplant cases showed marginal improvement with use of high grade sinter fines and decrease of pellet/sinter ratio to 50% compared to typical European case. Nordic steelplant charging pellets and briquettes had a reduction in system-wide energy of 5% to 8% for charging pellets from hematite or magnetite respectively compared to the typical European steelplant charging sinter and pellets made from hematite ore. Replacement of sinter with pellets was mainly responsible for the improvement with smaller contributions from magnetite ore in pelletizing.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Modèle thermodynamique, Thermodynamic model, Modelo termodinámico, Modélisation, Modeling, Modelización, Thermodynamique, Thermodynamics, Termodinámica, Thermodynamik, Fe-Al binary melts, activity of aluminum, activity of iron, atom and molecule coexistence theory (AMCT), mass action concentration, reaction ability, structural units, and thermodynamic model

A thermodynamic model for calculating the mass action concentrations of structural units in Fe-Al binary melts based on the atom-molecule coexistence theory, i.e., AMCT-Ni model, has been developed and verified through comparing with the reported activities of both Al and Fe in Fe-Al binary melts in a temperature from 1 573 K to 1 873 K by different researchers. The calculated mass action concentration NAl of Al or NFe of Fe can be applied to ideally substitute the measured activity aR, Al of Al or aR,Fe of Fe relative to pure liquid Al(l) or Fe(l) as standard state in Fe-Al binary melts. The following equations were derived for the activity coefficient of Al in natural logarithmic form In γAl and the calculated activity coefficient of Fe in natural logarithmic form In γfe in the temperature range from 1 573 K to 1 873 K. InγAl = -3.810 + 4.476xAl 0 < xAl ≤ 0.005, T = 1573 K InγAl = -3.397 + 4.248xAl, 0 < xAl ≤ 0.005, T = 1673 K lnγAl= -3.056 + 4.011xAl 0 < xAl ≤ 0.005, T = 1 773 K InγAl = -2.537 + 3.599xAl 0 < xAl ≤ 0.005, T = 1873 K InγFe = -3.837 + 6.701xFe 0 < xFe ≤ 0.005, T = 1573 K InγFe = -3.753 + 7.627xFe 0 < xFe ≤ 0.005, T = 1673 K InγFe = -3.701 + 8.066xFe 0 < xFe ≤ 0.005, T = 1773 K InγFe = -3.686 + 8.176xFe 0 < xFe ≤ 0.005, T = 1873 K Temperature dependences of the activity coefficient of Al in natural logarithmic form In γ0Aland the calculated activity coefficient of Fe in natural logarithmic form Inγ0Fe were given Inγ0Fe = 2.6917 - 10 222.7/T 1573 K ≤ T ≤ 1873 K Inγ0Fe= -2.8573 - 1 21.6816/T 1573 K ≤ T ≤ 1873 K The obtained values were compared with the results of the previous investigations.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Déphosphoration, Dephosphorization, Desfosforación, Entphosphorung, Oxyde de calcium, Calcium oxide, Calcio óxido, Calciumoxid, Scorie, Slag, Escoria, Schlacke, CaO―containing slags, ion and molecule coexistence theory, mass action concentration, phosphorous distribution, and structural units

A thermodynamic model for calculating phosphorous distribution between several slag systems and hot metal has been developed by coupling with a developed thermodynamic model for calculating mass action concentrations of iron oxides based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of iron oxides in the several CaO―containing slags can be applied to represent reaction ability of iron oxides, like classic concept of activity. The developed thermodynamic model for calculating phosphorus distribution can quantitatively calculate the respective contribution of free components, and the sum of the respective contribution of free components. The comparison of the calculated total phosphorous distribution with all available measured phosphorous distribution reported in literatures shows that the agreement between the calculated total phosphorous distribution and measured phosphorous distribution is good. This reliable agreement indicates that the IMCT―LP model can be successfully applied to predict the phosphorous distribution for CaO―FeO―Fe2O3-P2O5 slags, CaO―SiO2―FeO― Fe2O3―P2O5 slags, CaO―SiO2―FeO―Fe2O3―Al2O3―P2O5 slags, CaO―SiO2―FeO―MgO―P2O5 slags, CaO―SiO2― FeO―Fe2O3―MgO―P2O5 slags and CaO―SiO2―MgO―FeO―Fe2O3―MnO―P2O5 slags in a temperature range from 1 823 K to 1973 K.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Microstructure, Microestructura, Mikrogefuege, Acier liquide, Molten steel, Acero líquido, Fluessiger Stahl, Enlèvement, Removal, Toma, Inclusion non métallique, Non metallic inclusion, Inclusión no metálica, Nichtmetallischer Einschluss, Modélisation, Modeling, Modelización, Mécanisme, Mechanism, Mecanismo, bubble wake, inclusion removal, mechanism, molten steel, and water model

In order to make clear the mechanism how the non-metallic inclusions were removed by bubble wake flow in the molten steel, water model experiments were conducted by high speed video and image processing software. The bubble wake flow zone was partitioned and the characteristics of removing inclusions through bubble wake flow were analyzed, and the effects of various factors including bubble size, inclusion size and concentration on the removal behavior of inclusions were also investigated. The results show that the bubble wake flow is useful for the floatation of inclusions. The bubble wake flow involves the boundary zone and the rising zone, and the process of inclusion removal by the bubble wake flow can be decomposed into three sub-processes: firstly approaching and passing into the boundary zone, secondly passing into the rising zone and finally going on floating up or escaping from the rising zone. The increasing of the bubble diameter Db and the particle concentration Cp is in favor of inclusion removal by bubble wake flow. If the particle diameter Dp is smaller, the inclusions are easier to be removed by wake flow.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Acier bainitique, Bainitic steel, Acero bainítico, Bainitischer Stahl, Austénite résiduelle, Retained austenite, Austenita residual, Restaustenit, Martensite, Martensita, Martensit, Température cryogénique, Cryogenic temperature, Temperatura criogénica, Traitement thermique, Heat treatment, Tratamiento térmico, Waermebehandlung, cryogenic treatment, martensite, retained austenite, and super-bainitic steel

The effect of a deep cryogenic treatment on the microstructure of a super-bainitic steel was investigated. It was shown that quenching the super-bainitc steel in ―196°C liquid nitrogen resulted in the transformation of retained austenite to two phases: ∼20 nm thick martensite films and some nano carbides with a ∼25 nm diameter. Some refinement of the retained austenite occurred, due to formation of fine martensite laths within the retained austenite. The evolution of these new phases resulted in an increase in the average hardness of the super-bainitic steel from 641 to ∼670 HV1.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alumine, Alumina, Alúmina, Tonerde, Boulette, Pellet, Bolita, Matériau composite, Composite material, Material compuesto, Verbundwerkstoff, Silice, Silica, Sílice, Boudouard reaction, alumina and silica, carbon composite pellet, iron making, and reduction behavior

The effect of alumina and silica on the reaction behavior of carbon composite pellet was investigated by thermogravimetric analysis at 1 273 K (1 000°C) and 1 373 K (1 100°C). X-ray diffraction was used for the phase analysis of iron oxide changing from hematite to reduced iron. The overall reaction was divided into three stages according to phase transformation of iron oxide. CO and CO2 from off-gas data was used for kinetic analysis and for understanding reaction mechanism. The Boudouard reaction was largely influenced by alumina and silica that changed CO gas concentration resulting in different reduction behavior of the pellets. Alumina increased the reaction rate of carbon composite pellet while silica decreased the overall reaction rate.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base aluminium, Aluminium base alloys, Alumine, Alumina, Alúmina, Tonerde, Oxyde de fer, Iron oxide, Hierro óxido, Eisenoxid, Fe-Al alloys, alumina, carbon, iron oxide, molten iron, and reduction

With a view to produce Fe-Al alloys for deoxidation during steel refining, chemical reactions were investigated in Al2O3-C-Fe and Al2O3-Fe2O3-C systems at 1 823 K. Using a horizontal tube furnace and argon atmosphere, interactions were investigated for time periods up to 2 hours. Two sets of blends were prepared from initial constituents, which were later used to prepare two types of substrates. Alumina and synthetic graphite powders were blended in a 70: 30 proportion (blend I), and in the second set, Fe2O3 was blended with C in a proportion of 75:25 (blend II). In one case, blend I was mixed thoroughly with iron powder (Fe (2.7 pct C)) in a ratio of 80:20; in the second case, blend I was mixed with blend II in the ratio of 70:30. We report significant reduction reactions in both cases. SEM/EDS studies on the Al2O3-C-Fe system showed unambiguous evidence for the pick-up of aluminium by molten iron after 1 hour. Levels of aluminium in molten iron were found to increase significantly with time. Due to in-situ reduction of Fe2O3, the generation of CO gas and associated turbulence, the reactions were quite fast in the Al2O3-Fe2O3-C system. X-ray diffraction studies showed the presence of additional diffraction peaks belonging to Fe3AlC and Fe3Al systems. Molten iron was found to act as a reducing agent and a metallic solvent in both cases. This study provides evidence for the carbothermic reduction of alumina at 1 823 K and for the formation of ferroalloys directly from mixed oxides of aluminium and iron.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Azote, Nitrogen, Nitrógeno, Stickstoff, Dioxyde de carbone, Carbon dioxide, Carbono dióxido, Kohlendioxid, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Gonflement, Swelling, Inflamiento, Haut fourneau, Blast furnace, Alto horno, Hochofen, Monoxyde de carbone, Carbon monoxide, Carbono monóxido, Kohlenmonoxid, blast furnace, carbon dioxide, carbon monoxide, cold-bonded briquettes, nitrogen, non-isothermal, reduction, and swelling

Recycling of fine sized iron-rich by-products back to blast furnace (BF) process in the form of cement-bonded briquettes has become a common procedure in steel plants. Replacing part of the cement by Ground Granulated Blast Furnace Slag (GGBFS) is also a common method to reduce cement consumption. When the briquettes are subjected to high temperature and reducing atmosphere in the BF, the cement phases decompose and the iron oxides undergo a series of phase transformations. To avoid early disintegration and to improve the performance of the briquettes, it is necessary to study these reactions during the reduction. In the present study the reduction behavior of the BF briquette samples was studied by experimental methods in a laboratory scale furnace, which simulates the conditions of the BF shaft in a CO-CO2-N2 atmosphere. With interrupted experiments the composition of the briquette was studied in different reduction stages of the BF shaft. The effect of GGBFS as a binder material on the reduction was studied with GGBFS containing briquette samples. The reduction of briquettes was compared to an olivine pellet which was used as a reference sample. Considerably higher reduction rate was detected with the briquettes compared to the pellet at 1 100°C when reduced to metallic iron. 25-50 vol-% swelling in the briquette samples was detected during the wüstite-iron reduction step at 900-1 000°C. X-ray diffraction (XRD) was used to observe the phase transformations in the Fe-Fe2O3-CaO system of the briquette and the results are in agreement with the theory.

Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Charbon pulvérisé, Pulverized coal, Carbón pulverizado, Kohlenstaub, Coke, Coque, Koks, Elaboration fonte, Pig iron manufacture, Elaboración fundición, Roheisenherstellung, Haut fourneau, Blast furnace, Alto horno, Hochofen, Potentiel, Potential, Potencial, Réducteur, Reducing agent, Reductor, Reduktionsmittel, blast furnace, coke, gas utilization ratio, pulverized coal, reducing agent, and reduction index

In blast furnace operation, reducing agent ratio (RAR) is an important index. The RAR is defined only as a sum of weights, without considering the kind of reducing material. Here the author proposes a new reducing potential index, ReP, which considers the difference of reducing material composition under the real blast furnace condition that gas utilization ratios (ηco and ηH2) are 50%. Namely, ReP is set as C = 3, H = 0.5, O = -2, (N = 0) (ReP/kmol). This index evaluates reduction potentials of various reducing materials in a uniform manner. Latter part of this report includes an example of blast furnace operation analysis using ReP. Extended case studies that concern utilization of partially reduced ore, utilization of mixture of ferrous and carbonous materials, and gas utilization ratio changes far from 50%, are performed. When gas utilization ratios change from 50%, ReP is available if extended ReP is set as C = 2 + 2ηCO, H = ηH2, O = -2, (N = 0) (ReP/kmol).