Showing papers in "Steel Research International in 2011"
TL;DR: In this article, a numerical analysis of the quasi-steady fluid flow and interfacial behavior in a three-phase argon gas-stirred ladle with off-centered bottom Ar injection through a plug and two plugs placed in 1808 and 908 configurations, respectively, is presented.
Abstract: A numerical investigation is performed to describe the quasi-steady fluid flow and interfacial behavior in a three-phase argon gas-stirred ladle with off-centered bottom Ar injection through a plug and two plugs placed in 1808 and 908configurations, respectively. The flow of the fluid phase is solved in an Eulerian frame of reference together with the motion of every individually injected Ar bubble, tracked in its own Lagrangian frame. Volumeof fluid (VOF)modelis usedtotrackanyinterfacebetween twoor moreimmisciblephases,whichincludeslag/metal, slag/gasandmetal/ gas. The characteristics of fluid flow in a gas-stirred ladle with one plug or two plugs configuration are described when the slag layer and the top gas are presented. The slag layer deformation and slag open-eye formation at different Ar gas flow rates for three types of plug arrangements are given. The comparison of the mixing time, the deformation of slag layer and the behavior of slag/steel interface between one-plug and twoplug system is made. Several implications for ladle operational issues during a gas-stirred ladle refining cycle are discussed. It is found that the proper selection of Ar gas flow rate and plug arrangements during a ladle refining cycle is required for different refining purposes considering the mixing and metallurgical reaction in a three-phase ladle system.
100 citations
TL;DR: In this article, the authors studied the hydrogen solubility and diffusion in austenitic stainless steels with thermal desorption spectroscopy (TDS) after electrochemical potentiostatic hydrogen pre-charging.
Abstract: Hydrogen solubility and diffusion in austenitic stainless steels, namely AISI 310, AISI 301LN and AISI 201, are studied with thermal desorption spectroscopy (TDS) after electrochemical potentiostatic hydrogen pre-charging. Temperature dependencies of hydrogen desorption for all studied steels manifest a complex main peak caused by hydrogen releasing from the steel lattice by diffusion. Depending on the steel and heating rate the peak is situated from 350 to 500 K and its shape reflects a specific of hydrogen diffusion in stainless steels, which are multicomponent alloys. Analysis of the TDS curves is based on the hydrogen diffusion model taking into account trapping of hydrogen atoms in the energetically deep interstitial positions in the steel crystal lattice. Diffusion coefficient of hydrogen and its total content after the same charging procedure are obtained from the TDS curves and compared for the studied steels.
82 citations
TL;DR: In this article, the spark plasma sintering technique was used to construct a composite of 5 vol.% Mg-PSZ-TRIP-TRIMM composites and a model of the reinforcing mechanism was proposed.
Abstract: Dense TRIP-matrix composites containing 5 vol.% Mg-PSZ as reinforcing phase were produced by employing the spark plasma sintering technique. A continuous and seamless interface between the ceramic particles and the steel matrix was achieved. Compression tests revealed better mechanical properties of the 5 vol.% Mg-PSZ-TRIP steel composites in comparison with both, pure and Al2O3 reinforced TRIP steel. The underlying deformation mechanism within the austenitic matrix entailed a pronounced martensite formation. An additional phase transformation was observed within the ZrO2 particles. The enhanced mechanical properties of the 5 vol.% Mg-PSZ composite are dedicated to the transformation strengthening of the ceramic particles. Finally a model of the reinforcing mechanism is proposed.
74 citations
TL;DR: In this paper, the temperature dependence of the martensite formation and the mechanical properties of three high alloyed Cr-Mn-Ni as-cast steels with varying Ni contents were studied.
Abstract: The temperature dependence of the martensite formation and the mechanical properties of three high alloyed Cr-Mn-Ni as-cast steels with varying Ni contents were studied. The results showed that the Ms and Md temperatures of the steels decrease with increasing nickel contents. Therefore the strain-induced martensite formation, the TRIP effect and the temperature anomaly of the elongations occurs at lower temperatures. The steel alloyed with 3% nickel shows a stress induced formation of martensite and a dynamic strain aging. Depending on the nickel content and the temperature a TWIP effect occurs additionally to the TRIP effect in the investigated steels. The study was performed by using static tensile tests, dilatometer tests, optical microscopy and the magnetic scale for the detection of ferromagnetic phase fractions.
67 citations
TL;DR: In this article, the corrosion resistance of laboratory press-hardened components in aluminized, galvanized or galvannealed boron steels was evaluated through VDA 621-415 cyclic test for the automotive industry.
Abstract: The corrosion resistance of laboratory press-hardened components in aluminized, galvanized or galvannealed boron steels was evaluated through VDA 621-415 cyclic test for the automotive industry. 22MnB5 uncoated steel for hot stamping and standard galvanized steel for cold forming were also included as references. Corrosion resistance after painting (cosmetic corrosion) was quantified by measuring the delamination of electro-deposited paint from scribed panels. The rusting on their edges was used for determining the cut-edge corrosion resistance. The corrosion resistance on unpainted deformed panels (perforating corrosion) was quantified by mass losses and pit depth measurements. Zinc-coated boron steels were found to be more resistant to cosmetic corrosion than the other materials, and slightly more resistant to cut-edge corrosion than the aluminized one. Red rust apparition could not be avoided due to the high iron content in all these hot-stamped coatings. The three coated boron steels showed similar performances in terms of resistance to perforation. Aluminized boron steel presents the advantage of being less sensitive to hot-stamping process deviation. Its robustness has been proved for many years on cars.
64 citations
TL;DR: In this paper, a new twin bridge torsion shear test is proposed to determine anisotropic yield behavior and to characterize prestrained specimen, for instance due to cold rolling, when the yield locus is shifted by a backstress tensor.
Abstract: In order to predict plastic material behavior for sheet forming processes by finite element simulation, shear tests are useful to identify material parameters. Since the existing shear test setups have certain disadvantages, a new twin bridge torsion shear test is proposed. Stress and strain calculation is derived from the presented geometrical features. The clamping situation and the shear gauge dimensions are investigated to evaluate the quality of the obtained flow curves. It is shown that this test specimen is suitable to determine anisotropic yield behavior and to characterize prestrained specimen, for instance due to cold rolling, when the yield locus is shifted by a backstress tensor.
62 citations
TL;DR: In this paper, the cyclic deformation behavior of three high-alloyed cast steels is characterized by different chemical compositions leading to different austenite stabilities and stacking fault energies.
Abstract: This study presents the cyclic deformation behaviour of three high-alloyed austenitic cast steels which are characterized by different chemical compositions leading to different austenite stabilities and stacking fault energies. Thus, depending on the chemical composition different deformation mechanisms arise which have a significant influence on the cyclic deformation behaviour and life time relations.
The materials were characterized under total-strain control. The fatigue life relations of Basquin and Manson-Coffin are applied successfully for all steel variants. The cyclic stress-strain response is described using the Ramberg-Osgood relationship. It is shown that the parameters n' and K' depend strongly on the accumulated plastic strain λp. The mechanical properties are discussed together with microstructural investigations of deformation structures and martensitic transformations as well as twinning, respectively.
55 citations
TL;DR: In this article, a novel gas-solid suspension ironmaking process is proposed at the University of Utah, which is based on the flash reduction of iron ore concentrate using a gaseous reagent, such as hydrogen, syngas, natural gas or a combination of thereof.
Abstract: A novel gas-solid suspension ironmaking process is under development at the University of Utah, which would greatly reduce energy consumption and carbon dioxide emission compared with current blast furnace technology. The proposed process is based on the flash reduction of iron ore concentrate using a gaseous reagent, such as hydrogen, syngas, natural gas or a combination of thereof.
A process flow sheet of the proposed ironmaking process using purchased hydrogen was constructed and then simulations were performed at several potential operating conditions. Ironmaking was simulated using two different process configurations. The simulation results show that the required fresh hydrogen would increase with higher excess driving force and operating temperature, but not greatly when hydrogen is preheated. Compared with the average blast furnace process, the proposed process would reduce energy consumption by 57 - 60%, using the higher heating value of hydrogen (71 – 73%, if the lower heating value is used), when hydrogen and coal are considered as the starting materials in the respective processes. The economic feasibility analysis using net present value (NPV) indicates that the proposed process could be economically feasible at elevated hot metal prices and/or if reduction in carbon dioxide emissions has a significant value in a cap and trade scenario.
53 citations
TL;DR: In this article, the effect of SiO2 on the formation of anosovite in the titanium-bearing blast furnace slags was studied under C/CO equilibrated atmospheres using a combination of X-ray Diffraction (XRD) and Energy Dispersive Xray Spectroscopy (EDX).
Abstract: The present paper investigated the crystallization behavior of Ti-concentrating phases in titanium-bearing blast furnace slags influenced by the silica content. The objective was to recycle the titanium from titanium-bearing blast furnace slags by enriching Ti element in anosovite. The effect of SiO2 on the formation of anosovite in the titanium-bearing blast furnace slags was studied under C/CO equilibrated atmospheres using a combination of X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDX). It was found that, under the C/CO equilibrated atmospheres, the formed primary phases transformed from perovskite to anosovite by adding SiO2 up to 35 wt% in the slags. The related mechanism was investigated according to the theory of molten slags structure and the principle of thermodynamics.
52 citations
TL;DR: In this paper, a compensation control model of secondary cooling process of billet continuous casting for quality steel has been presented and the effects on the spray control of the various parameters such as steel superheat, casting speed, cooling water temperature and chemical component of steel were considered.
Abstract: In this paper, a compensation control model of secondary cooling process of billet continuous casting for quality steel has been presented. The effects on the spray control of the various parameters such as steel superheat, casting speed, cooling water temperature and chemical component of steel were considered. The parameters of control model were determined to associate with the two-dimensional heat transfer equation and solved by finite-difference method. Effects of steel superheat and cooling water temperature on surface temperature, solidification structure and solidifying end point were discussed. Results indicate that steel superheat significantly affects solidification structure and solidifying end point but has a little effect on slab surface temperature. Moreover, secondary cooling water temperature affects surface temperature and solidifying end point but has a little effect on solidification structure. The surface temperature and solidifying end point can be maintain stabilized through applying the compensation control model when steel superheat and cooling water temperature vary. The models have been validated by industrial measurements. The results show that the simulations are in very good agreement with the real casting situation.
51 citations
TL;DR: In this article, the effect of CaF2 on slag viscosity depended strongly on the composition of master slag and the amount of SiO2 contained in the master slags.
Abstract: The present work is to study slag phenomena in steelmaking process. In order to attain thegoal, a number of high temperature experiments and simulation experiments were carried out. Four master slags were used to study the effect of CaF2 on slag viscosity. Experimentalresults indicated the effect of CaF2 on slag viscosity depended strongly on the composition ofmaster slag. For high basicity slags, CaF2 mainly suppressed the precipitation of solid phasesat lower temperatures, leading to a lower viscosity compared to CaF2-free slags. For slagswith higher SiO2 contents, CaF2 both lowered the viscosity of the liquid phase and suppressedthe precipitation of solid phases. The viscosities of solid-liquid mixtures were experimentally determined for silicon oilparaffinsystem at room temperature and solid-liquid oxide mixture at steelmakingtemperature. The results of both measurements indicated that the increasing trend of mixturesviscosity with particle fraction can be described by Einstein-Roscoe equation.Silicone oils of different viscosities were used to simulate slag foaming. The experimentalresults showed, at a constant viscosity, the foaming height increased first with superficialvelocity before reaching a maximum value. Thereafter, the foaming height decreased with thefurther increase of the superficial velocity. Similar, a maximum foaming height was observedat an optimum viscosity when a constant superficial gas velocity was applied. Based on theexperimental data, a semi-empirical equation of foaming height was developed. Thepredictions of the model agreed well with experiment data. The model could also reasonablywell explain the industrial pilot trial experiments. Water-silicon oils model and liquid alloy (Ga-In-Sn)- 12% HCl acid model were employed tosimulate the formation of open-eyes in a gas stirred ladle. The experimental results indicatedthat the viscosity of the top liquid and the interfacial tension between the two liquids had onlylittle effect on the open-eye size. A semi-empirical model was developed to describe the sizeof open-eye as functions of the gas flow rate, bath height and slag height. The two sets ofparameters obtained for the water and Ga-In-Sn models were very different. Industrial trialswere also conducted to examine the applicability of the models. Liquid alloy model couldwell predict the formation of an open-eye during ladle treatment. Two cold models, sodium tungstate-oil model and water-oil model, were carried out tosimulate the formation of droplets in a gas stirred ladle. The experimental results showed thatthe gas flow rate and interfacial tension had strong impact on the size of droplets. A semiempiricalmodel was developed to describe the size of droplets for water model. Meanwhile,the parameter obtained for water model can be used for sodium tungstate-silicone oil system.The results indicate the model has strong compatibility.
TL;DR: In this article, a comprehensive technology integrating beneficiation and smelting processes was proposed, which would provide technology support for the efficient utilization of high phosphorus Oolitic Hematite, and also provide technology for industrial demonstrating projects.
Abstract: With increasing consumption of iron ore over the world, new technology of beneficiation and smelting is more urgently needed than ever before to explore ores which, are difficult to utilise by beneficiation and smelting processes. Oolitic Hematite mines, iron ore with poor beneficiation efficiency are widely distributed in China with the most abundant deposits. In this paper, comprehensive technology integrating beneficiation and smelting processes was proposed. This paper reports the experimental results on ore beneficiation, pretreatment of hot metal with high phosphorus and dephosphorization during direct reduction. It would provide technology support for the efficient utilization of high phosphorus Oolitic Hematite, and also provide technology for industrial demonstrating projects.
TL;DR: In this article, the authors investigated the relationship between the martensite start temperature, re-transformation start temperature (As), and retransformation finish temperature (Af) of six high alloyed Cr-Mn-Ni steels with varying Ni and Mn contents in the wrought and as-cast state.
Abstract: The martensite start temperature (Ms), the martensite austenite re-transformation start temperature (As) and the re-transformation finish temperature (Af) of six high alloyed Cr-Mn-Ni steels with varying Ni and Mn contents in the wrought and as-cast state were studied. The aim of this investigation is the development of the relationships between the Ms, As, Af, T0 temperatures and the chemical composition of a new type of Cr-Mn-Ni steels. The investigations show that the Ms, As and Af temperatures decrease with increasing nickel and manganese contents. The Af temperature depends on the amount of martensite. Regression equations for the transformation temperatures are given. The experimental results are based on dilatometer tests and microstructure investigations.
TL;DR: In this article, three high-alloyed cast CrMnNi-steels with different austenite stabilities were examined and three deformation induced martensitic transformation (TRIP-effect) and mechanical twinning (TWIP effect) mechanisms were compared.
Abstract: Modern steel developments often use additional deformation mechanisms like the deformation induced martensitic transformation (TRIP-effect) and mechanical twinning (TWIP-effect) to enhance elongation and strength. Three high-alloyed cast CrMnNi-steels with different austenite stabilities were examined. Dependent on the austenite stability, TRIP-effect and TWIP-effect were found. A low austenite stability causes a distinctive formation of deformation induced α'-martensite and therefore a strong strain hardening. The increase of strain rate leads to an increase in yield strength and flow stress, but also to a counteractive adiabatic heating of the specimen. Dependent on the degree of deformation, low austenite stabilities and high strain rates lead to excellent values in specific energy absorption.
TL;DR: In this article, a density-functional theory-based total energy calculation was performed in order to discover possible local atomic ordering effects in manganese-rich austenite phases.
Abstract: Density-functional theory-based total-energy calculations have been performed in order to discover possible local atomic ordering effects in manganese-rich austenite phases. For manganese contents of 25 and 50% we found a thermochemical driving force that should lead to a manganese enrichment of the immediate proximity of the carbon atom. The energy lowers almost linearly from a pure iron- to a pure manganese-coordinated carbon atom with an energy difference between the two M6 octahedra (M = Fe, Mn) of ca. 0.34 eV (33 kJ/mol) for both antiferromagnetic and nonmagnetic structures. This very effect and the energy differences are almost independent of (a) the manganese concentration, (b) the carbon concentration, and (c) the magnetic state. A comprehensive bonding analysis yields that the effect is caused by the destabilization of the carbon atom's surrounding metal–metal bonds which come out larger for iron than for manganese. The size of the energy differences indicate a strong tendency for carbon-induced short-range ordering.
TL;DR: In this paper, the phase compositions of MgO partially stabilized zirconia (Mg-PSZ) were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), as well as electron backscatter diffraction (EBSD) due to the high spatial resolution.
Abstract: Metal matrix composites (MMC) containing TRIP-steel/Mg-PSZ were processed by cold pressing and conventional sintering in different atmospheres. The MMC was based on austenitic steel in the system Fe-Cr-Mn-Ni showing transformation induced plasticity (TRIP). Depending on the sintering temperature, the sintering atmosphere and the steel composition the phase compositions of MgO partially stabilized zirconia (Mg-PSZ) were analysed by scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX) as well as electron backscatter diffraction (EBSD). The interactions between the alloying elements of austenitic stainless steel and the ceramic stabilizer (MgO) as well as the technological parameters lead to a significant change in the phase composition of the Mg-PSZ. The changes can be analysed by EBSD due to the high spatial resolution.
TL;DR: In order to understand the complicated phenomena of pulverized coal injection (PCI) process in blast furnace (BF), several mathematical models have been developed by the UNSW and BSR cooperation as mentioned in this paper.
Abstract: In order to understand the complicated phenomena of pulverized coal injection (PCI) process in blast furnace (BF), several mathematical models have been developed by the UNSW and BSR cooperation. These models are featuring from coal combustion in a pilot-scale test rig, to coal combustion in a real BF, and then to coal/coke combustion in a real BF, respectively. This paper reviews these PCI models in aspects of model developments and model applicability. The model development is firstly discussed in terms of model formulation, their new features and geometry/regions considered. The model applicability is then discussed in terms of main findings followed by the model evaluation on their advantages and limitations. It is indicated that the three PCI models are all able to describe PCI operation qualitatively. The model of coal/coke combustion in a real BF is more reliable for simulating in-furnace phenomena of PCI operation qualitatively and quantitatively. Such model gives a more reliable burnout prediction over the raceway surface, which could better represent the amount of unburnt char entering the coke bed. These models are useful for understanding the flow-thermo-chemical behaviours and then optimising the PCI operation in practice.
TL;DR: In this article, cold model experiments and CFD simulations were carried out with single and multi-hole nozzles and the velocity profiles of jets were successfully simulated, and water model experiments were also performed to study the cavity formation and the spitting phenomena by the impinging jets.
Abstract: It is important to understand the physical interaction between top-blown oxygen jets and liquid steel in basic oxygen steelmaking furnaces (BOF). In the present study, cold model experiments and CFD simulations were carried out with single- and multi-hole nozzles and the velocity profiles of jets were successfully simulated. Water model experiments were also performed to study the cavity formation and the spitting phenomena by the impinging jets. The cavity shapes and the spitting behavior were correlated to the top-blowing conditions by considering the characteristics of multi-hole nozzle jets.
TL;DR: In this paper, the viscosities of some quaternary slags in the Al2O3-CaO-MgO-SiO2 system were measured using the rotating cylinder method.
Abstract: Viscosities of some quaternary slags in the Al2O3-CaO-MgO-SiO2 system were measured using the rotating cylinder method. Eight different slag compositions were selected. These slag compositions rang ...
TL;DR: In this paper, the authors showed that after long term development and continuous improvement, special intensified smelting technologies for vanadium-bearing titanomagnetite by blast furnace were obtained and improved gradually.
Abstract: The smelting of vanadium-bearing titanomagnetite by blast furnace was very difficult because the content of TiO2 of blast furnace slag could amount to 20-25%. After long term development and continuous improvement, special intensified smelting technologies for vanadium-bearing titanomagnetite by blast furnace were obtained and improved gradually. With the improvement of beneficiated material and equipment, smelting intensity has been increasing gradually and the highest comprehensive smelting intensity that is fuel comsumption per unit useful volume per day reached 1.45t/(m3·d). Technical-and-economic indexes of blast furnace have also been increasing remarkably. The highest monthly utilization coefficient exceeded 2.7t/(m3·d) on the condition that the burden total ferrum grade was only about 50%.
TL;DR: In this article, the authors developed stress-temperature-transformation (STT) and Deformation-Temperature-Transformation (DTT) diagrams for a novel austenitic Cr-Mn-Ni (16%Cr, 6% Mn,6% Ni) as-cast steel and AISI 304 are presented.
Abstract: Stress-Temperature-Transformation (STT) and Deformation-Temperature-Transformation (DTT) diagrams are suitable to characterize the TRIP (transformation-induced plasticity) and TWIP (twinning-induced plasticity) effect in steels. The triggering stresses for the deformation-induced microstructure transformation processes, the characteristic temperatures, the yield stress and the strength of the steel are plotted in the STT diagram as functions of temperature. The elongation values of the austenite, the strain-induced twins and martensite formations are shown on the DTT diagram.
The systematics of STT and DTT diagrams and the method for their development are described. Especially, the correlations between the STT and DTT diagrams and the thermodynamics are explained in the present paper. The developed STT and DTT diagrams for a novel austenitic Cr-Mn-Ni (16%Cr, 6% Mn, 6% Ni) as-cast steel and austenitic steel AISI 304 are presented. The Cr-Mn-Ni steel shows a deformation-induced α′-martensite and twin formation. In contrast, the AISI 304 shows a deformation-induced e- and α′-martensite formation. The differences between both steel grades are based on thermodynamic pre-conditions.
Therefore the thermodynamic stability conditions of the phases and the kinetics of stress and deformation-induced martensite and the twins formation are reflected in the developed STT and DTT diagrams.
TL;DR: In this paper, a dissymmetrical cooling on different surfaces, by which the area for the precipitation of segregation solutes was enlarged, was introduced to mitigate the center macro-segregation in billets during continuous casting process.
Abstract: In the current paper, Methods of enlarging the area for the distribution of segregation solutes were introduced to mitigate center macro-segregation in steel billets and steel slabs during continuous casting process, which cost less and have significant effect. The location of center macro-segregation is relative to the shape of liquid-core at the solidification end during steel continuous casting. A method of dissymmetrical cooling on different surfaces, by which the area for the precipitation of segregation solutes was enlarged, was introduced to mitigate the center macro-segregation in billets during continuous casting process. Method of optimizing the uniformity of solidified shell in the transverse direction was introduced to mitigate the center macro-segregation in steel slabs. The uniform cooling intensity along the transverse direction guaranteed a regular solidification end in the continuous casting slab, which aided in the effective application of dynamic soft reduction technology. A relevant 2-D heat transfer model was developed for the optimization of uniform solidification. The current method was applied to the industrial slab continuous casting using the heat transfer model. The results indicated a better industrial slab quality with much less center macro-segregation after the use of the method.
TL;DR: In this paper, a sliding-window smooth support vector regression model is presented to address the issue of predicting the blast furnace inner thermal state, represented by the silicon content in blast furnace hot metal in the context.
Abstract: Blast furnace is one of the most complex industrial reactors and remains some unsolved puzzles, such as blast furnace automation, prediction of the inner thermal state, etc. In this work, a sliding-window smooth support vector regression model is presented to address the issue of predicting the blast furnace inner thermal state, represented by the silicon content in blast furnace hot metal in the context. Different from the traditional numerical prediction models of silicon, the constructed SW-SSVR model is devoted to predicting the changing trend of silicon and exhibits good performance with high percentage of successful trend prediction, competitive computational speed and timely online service. Additionally, some sharp fluctuation trend in the silicon test data can also be followed well by the SW-SSVR model, which is always difficult for traditional data–driven based silicon prediction models. All of these indicate that the SW-SSVR model is a good candidate to predict the change of blast furnace inner thermal state, and may provide a guide for operators to take proper action on operating blast furnace in advance.
TL;DR: In this article, the fraction and microstructure of spontaneous and deformation-induced martensite in three austenitic stainless steels with different austenite stability have been investigated.
Abstract: The fraction and microstructure of spontaneous and deformation-induced martensite in three austenitic stainless steels with different austenite stability have been investigated. Samples were quench ...
TL;DR: In this article, an ab initio approach to determine single-crystalline elastic constants of ordered compounds and disordered alloys is presented. But the authors focus on the effect of magnetism on the elasticity and phase stability of α-Fe.
Abstract: Quantum-mechanical (so-called ab initio) calculations have achieved considerable reliability in predicting physical and chemical properties and phenomena. Due to their reliability they are becoming increasingly useful when designing new alloys or revealing the origin of phenomena in existing materials, also because these calculations are able to accurately predict basic material properties without experimental input. Due to the universal validity of fundamental quantum mechanics, not only ground-state properties, but also materials responses to external parameters can reliably be determined. The focus of the present paper is on ab initio approaches to the elasticity of materials. First, the methodology to determine single-crystalline elastic constants and polycrystalline moduli of ordered compounds as well as disordered alloys is introduced. In a second part, the methodology is applied on α-Fe, with a main focus on (i) investigating the influence of magnetism on its elasticity and phase stability and (ii) simulating extreme loading conditions that go up to the theoretical tensile strength limits and beyond.
TL;DR: In this article, the authors investigated a new route to utilize waste bakelite as a source of carbon in EAF steelmaking process and reported the carbon dissolution behavior of bakelite/coke blends into liquid steel at 1550°C.
Abstract: Bakelite is a thermoset plastic commonly found in electronic and automobile components. CaCO3 is generally found in the polymer as a filler material. Since it cannot be remelted, the disposal of this material has become an environmental issue. The present study investigates a new route to utilize waste bakelite as a source of carbon in EAF steelmaking process. This paper reports the carbon dissolution behaviour of bakelite/coke blends into liquid steel at 1550 °C. The carbon pick up in the liquid steel after reaction with varying blends of bakelite/coke for 30 minutes ranged between 0.13 wt% to 0.17 wt%; these were generally higher than that observed from coke alone (0.1 wt%). The dissolution rate (K) was also found to improve and the observed trend was BK2 (0.045 × 10−3 s−1) > BK3 (0.023 × 10−3 s−1) > BK1 (0.005 × 10−3 s−1) > coke (0.003 × 10−3 s−1). The reaction products formed at the interface after 30 minutes of contact between liquid steel and bakelite/coke blends were observed to be a CaS-Al2O3 complex. The presence of CaS in the interfacial layer due to the CaO in the ash, lowered melting temperature of the layer, thereby allowing for increased removal of the ash layer and greater carbon pick-up. The CaO is formed from the decomposition of CaCO3, and its presence was found to have a positive effect on modifying the properties of the coke, and thereby enhancing the carbon dissolution behaviour.
TL;DR: In this paper, the effects of charging carbon composite iron ore hot briquette (CCB) on the dripping properties of comprehensive burdens are elucidated based on the experiments under simulated blast furnace conditions, which revealed that the CCB possesses the required metallurgical properties and is suitable to use as the blast furnace burden.
Abstract: Carbon composite iron ore hot briquette (CCB) is the product of fine iron ore and fine coal by hot briquetting process, which attracts more and more attention as a new type of ironmaking raw materials aiming to improve the operation efficiency and reduce the coke consumption of blast furnace. This paper is devoted to experimental study on metallurgical properties of CCB and numerical simulation of the BF operation with CCB charging. At first, the metallurgical properties of CCB, including cold crushing strength, RDI, RSI, reducibility, high temperature strength, and softening and dripping are experimentally tested and compared with the common burdens, which revealed that the CCB possesses the required metallurgical properties and is suitable to use as the blast furnace burden. Then, the effects of charging CCB on the dripping properties of comprehensive burdens are elucidated based on the experiments under simulated blast furnace conditions. The results showed that the maximum charging ratio of CCB in the iron burdens is 40%–50% for achieving appropriate dripping properties of the mixed burdens. Finally, a multi-fluid blast furnace model is used to simulate BF operation with CCB charging. According to model simulations, charging CCB will cause the temperature level to decreases in the furnace and the location of the cohesive zone shifts downward. On the other hand, the productivity tends to increase while coke rate and total reducing agent rate decrease, the heat efficiency improves remarkably and the operation performance of BF is effectively enhanced.
TL;DR: In this article, a 3D cellular automaton was used for the simulation of recrystallization in order to study the impact of different nucleation mechanisms on annealing texture.
Abstract: The annealing textures of a Fe-0.3%C-22%Mn TRIP steel and a Fe-0.6%C-22%Mn TWIP steel were experimentally determined. The results showed that these alloys have an almost identical texture after recrystallization. In general, the recrystallization textures showed low intensities and a dependency on annealing temperature. The samples annealed at high temperatures exhibited a random texture whereas samples annealed at lower temperature showed at least a weak texture. Due to the low SFE of the metals, we surmise that the nucleation at shear bands contributed to the randomization of the recrystallization texture. It was found that grains with Q orientation grow in volume by a factor of 30 compared to deformed state. A 3D cellular automaton was utilized for the simulation of recrystallization in order to study the impact of different nucleation mechanisms on annealing texture. The simulations showed that at least 70% of nucleation has to occur at shear bands to account for the observed randomization of the texture. In order to reproduce the weak texture of samples annealed at lower temperatures, 30% of the nuclei at shear bands needed to be either Q or Goss oriented. A more detailed analysis is necessary to also reproduce the minor texture components.
TL;DR: In this paper, the capabilities of the thin strip casting method to produce high manganese steel strip are examined, and a FeMn22C0.6 strip has been cast both using a lab-scale twin roll casting line and a more conventional process chain.
Abstract: In this paper, the capabilities of the thin strip (twin roller) casting method to produce high manganese steel strip are examined. For this purpose a FeMn22C0.6 strip has been cast both using a lab-scale twin roll casting line and a more conventional process chain. The experiments show that the production of high manganese steel strip is feasible with both methods. Differences become apparent in the microstructure and chemical composition. While the strip which was produced by ingot casting and hot forming shows a homogenous grain distribution, the thin-strip-cast one shows a typical casting microstructure, consisting of dendritic and globulitic structures. In addition, the thin-strip-cast steel contains the accurate carbon content, while the hot forming route led to a loss of carbon, which influences the mechanical properties. The good potential of thin-strip casting of high manganese steels, although it still has to be improved, is confirmed.
TL;DR: In this paper, a new model has been developed that combines Discrete Element Method with Computational Fluid Dynamics (DEM-CFD) to simulate precisely the gas flow and solid motion in a blast furnace.
Abstract: Blast furnace technology is currently aiming at low reducing agent operation so as to decrease CO2 emissions. At the same time, the inner volume of blast furnaces has frequently been enlarged so as to increase production rate in some countries, including Japan. Operating conditions designed for low reducing agent in a large blast furnace tend to cause unfavorable phenomena such as slipping of the burden and gas channeling due to the decrease in coke rate. Mathematical models help to clarify the in-furnace phenomena under these situations.
From the above backgrounds, a new model has been developed that combines Discrete Element Method with Computational Fluid Dynamics (DEM-CFD) to simulate precisely the gas flow and solid motion in a blast furnace. The present study aimed to develop a three-dimensional mathematical model based on DEM-CFD for simultaneous analysis of gas and solid flow in the whole blast furnace. The unbalanced gas flow in the case of clogging of the particular tuyere was analyzed to clarify the circumferential unevenness in the lower part of the blast furnace. Based on the combined DEM with CFD model, the non-uniform gas flow in the lower part of the blast furnace was precisely evaluated.