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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559

ISIJ International Vol. 58 (2018), No. 11

  • A Review of Fluorine-free Mold Flux Development

    pp. 1957-1964

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    DOI:10.2355/isijinternational.ISIJINT-2018-232

    More than 95% of crude steel has been produced through the process of continuous casting technology, in which mold flux plays important roles inside the mold. As conventional mold flux system contains certain amount of fluorides that tend to be evaporated and cause the corrosion of casting facilities and environmental pollutions etc. It is urgent to optimize the mold flux composition without fluorides for the continuous casting process. In this review paper, the substitutes for fluorides in mold flux are summarized via two main strategies: TiO2 and B2O3 based additives. Among them, CaO–SiO2–Al2O3–Na2O–B2O3 based fluoride-free (F-free) mold flux system shows great potential to replace conventional mold flux that can be widely used in the process of continuous casting, as the precipitated phase-Ca11Si4B2O22 has the most similar crystallization behavior to cuspidine in conventional mold flux, which can effectively control the horizontal heat transfer and reduce the occurrence of longitudinal cracks. This paper would provide technical guidance and research direction for the design and study of efficient environment-friendly F-free mold flux.
  • Phosphorus Partition and Phosphate Capacity of Basic Oxygen Steelmaking Slags

    pp. 1965-1971

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    DOI:10.2355/isijinternational.ISIJINT-2018-129

    The phosphorus partition (LP) and phosphate capacity ([ This part of text is omitted ]) were measured for slags in the CaO–SiO2–MgO–FetO–(MnO–Al2O3–TiO2–P2O5) system over temperatures representative of basic oxygen steelmaking. The measured LP values were found to be in good agreement with those predicted from the model of Assis et al. The oxygen potential of the slag-metal systems studied was also evaluated and used in combination with the measured LP to calculate the [ This part of text is omitted ] of the slags. Capacity values in the range of 7.77×1016 to 4.27×1019 for temperatures 1550°C to 1700°C were obtained.Correlations of [ This part of text is omitted ] with common measures of slag basicity (v-ratio and optical basicity) were sought and reported. Consistent with other researchers it was found that the LP and [ This part of text is omitted ] increased with increasing slag basicity and decreasing temperature.
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    Readers Who Read This Article Also Read

    1. Using Red Mud-based Flux in Steelmaking for High Phosphorus Hot Metal ISIJ International Vol.58(2018), No.11
    2. A Review of Fluorine-free Mold Flux Development ISIJ International Vol.58(2018), No.11
    3. Improving the Desulphurization in COREX-3000 Process by the Optimization of Chemical Compositions of Slag ISIJ International Vol.58(2018), No.11
  • Effect of Crystallization on the Abrupt Viscosity Increase during the Slag Cooling Process

    pp. 1972-1978

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    DOI:10.2355/isijinternational.ISIJINT-2018-176

    The abrupt viscosity increase during the slag cooling process may jeopardize the stability of industrial operation. However, the underlying mechanism has not been completely understood yet. In the present work, the viscosity of basic oxygen furnace (BOF) slags with different additions, i.e. Al2O3 and SiO2, was measured via a rotational rheometer. The slag crystallization behavior was observed in-situ via confocal laser scanning microscope (CLSM). Microstructural features, i.e. crystal fraction, shape and size in the slag, were identified through characterizing the water-quenched slag sample. The present results show that the abrupt viscosity increase occurs only when the crystal fraction exceeds a threshold (defined as critical volume fraction of solid, Φc), at which crystals start to interfere with each other and form solid aggregates/clusters. The critical solid fraction varies between 0.33 and 0.51 for the investigated samples and is found to decrease with increasing crystal aspect ratio, which varies between 1.43 and 2.17 in our samples.
  • A Kinetic Model on Oxygen Transfer at a Steel/Slag Interface under Effect of Interfacial Tension

    pp. 1979-1988

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    DOI:10.2355/isijinternational.ISIJINT-2018-303

    A kinetic model was developed to predict the dynamic change of the oxygen content in the sub-interface region as well as the dynamic change of the interfacial tension between molten steel and slag. The dynamic steel/slag interfacial phenomena are very complex, where the combined effect of thermodynamics and kinetics on the interfacial tension needs to be accounted for. As a first step, the current model only considers the SiO2 decomposition, oxygen adsorption and desorption at the steel/slag interface to realize the modeling of the dynamic change of the steel/slag interface phenomena. The oxygen desorption rate was derived based on the slope of the interfacial tension change over oxygen content. Specifically, the oxygen change with time in a sub-interface was predicted by the current model. The oxygen desorption rate was found to have an important influence on the dynamic change of the oxygen content in the sub-interface region. Furthermore, a low slag viscosity was found to increase the oxygen content at the interface due to the fast supply of SiO2 from the slag bulk to the interface. In addition, the equilibrium constant for the oxygen adsorption at an interface due to the interfacial tension effect increases the oxygen content in the sub-interface region.
  • Effect of Introducing Coke into Ore Layer on Softening-melting-dropping Characteristics of Vanadium-titanium Mixed Burden under Simulating BF Conditions

    pp. 1989-1998

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    DOI:10.2355/isijinternational.ISIJINT-2018-175

    Coke-ore mixed charging is a well-known and effective measure to strengthen BF operation and realize low reducing agent BF ironmaking. The objective of this paper is to investigate the effect of coke-ore mixing ratio on softening-melting dropping performance and permeability of vanadium-titanium mixed burden and to clarify the interaction mechanism between mixed nut coke and iron-bearing burden under BF simulating conditions. It was found that the softening-melting-dropping behaviors and permeability of mixed burden get improved obviously with a coke-ore mixing ratio of 20%. However, the generation of carbide of V and Ti would be accelerated with further increasing coke-ore mixing ratio to 50%, which would deteriorate the fluidity of slag and worsen the dropping behavior of mixed burden and lower the yield of V in liquid iron. The interaction between nut coke and vanadium-titanium mixed burden could be summarized as four parts, namely reduction strengthen, carburization promotion, permeability improvement, and the precipitation of the carbide of titanium.
  • Radar Detection-based Modeling in a Blast Furnace: a Prediction Model of Burden Surface Shape after Charging

    pp. 1999-2008

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    DOI:10.2355/isijinternational.ISIJINT-2018-267

    Radar detection is an advanced method for monitoring a blast furnace’s inner burden surface shape, which is an important factor that largely affects the production efficiency of the iron-making process. In this paper, a radar detection-based model for the prediction of burden surface shape was developed for assisting operators in developing a charging strategy. The data used are composed of both the detection and controlling records of a real, working-state blast furnace obtained by mechanical swing radar and a furnace database system, respectively. By defining and analyzing the stacking density function, the physical meanings of the modeling principles were revealed. Combined with the classical force charging trajectory sub-model and detection-driven burden descent calculation, the proposed model adopts Gaussian radius basis functions to approximate the stacking mechanism of the burden charging process. The parameter identification results show that the model can approximate the burden surface radius profile well. Compared with the results obtained for coke layers, the parameters’ ranges for the ore layers are narrower. Performance comparison shows that the proposed model has the advantages of higher prediction accuracy for both local details and global shape over the classical polygonal line model.
  • Influence of Agitating Conditions on Agglomeration and Collapse of Iron Ore Mixture

    pp. 2009-2017

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    DOI:10.2355/isijinternational.ISIJINT-2018-359

    The influence of agitating conditions on agglomeration and collapse of wet iron ore mixture was investigated in the view of kinetics and matrix model analysis. At the initial stage of mixing behavior, it was found that average particle size was dependent on the mixing rate constant defined as the deviation degree of particle size and water distribution from initial state. Mixing rate constants of powder and water were almost consistent with each other and expressed by power function of Froude number of impeller. It was presumed that the water and fine particle moved together as wet granules during mixing at a given water level. According to the analysis of entire mixing behavior based on matrix model, it was found that the collapse indexes defined by matrix parameters increased as particle size and impact force increased. Minimum particle size at initial mixing state decreased as collapse index increased and the size of long term mixing state was expected by intrinsic increasing rates defined by maximum eigenvalue of matrix parameters.
  • Numerical Investigation of Coke Collapse and Size Segregation in the Bell-less Top Blast Furnace

    pp. 2018-2024

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    DOI:10.2355/isijinternational.ISIJINT-2018-415

    The coke collapse phenomenon significantly affects the burden and gas distributions, and further gas utilization and CO2 emission. Therefore, it is necessary to investigate the coke collapse in blast furnace. A three dimensional model of bell-less top blast furnace is established based on discrete element method (DEM). The effects of chute angle, rotating speed and sinter amount on the coke collapse charateristics are then investigated based on this model. The results show that coke profile changes a lot after its collapse and the collapse region is more than 40% of the furnace radius. Sinter amount affects the coke collapse amount much, followed by chute angle and chute rotating speed. The coke collapse region is affected most by sinter amount, followed by chute rotating speed and chute angle. Large chute angle, higher rotating speed and small sinter amount are recommended for practical operation since they help to obtain a lighter coke size segregation along radius.
  • Improving the Desulphurization in COREX-3000 Process by the Optimization of Chemical Compositions of Slag

    pp. 2025-2031

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    DOI:10.2355/isijinternational.ISIJINT-2018-427

    To improve the desulfurization in the COREX-3000 process, several aspects are studied and practiced. The work documented in the present paper focuses on the effects of chemical compositions of slag, such as CaO/SiO2, MgO, MgO/Al2O3 and MnO, on desulfurization. Theoretical calculations of sulfide capacity and viscosity of slag and diffusion coefficient of S2− in the slag are given to study the effects of slag chemical compositions on the thermodynamics and dynamics of desulfurization. After that, experiments are carried out to verify the theoretical analyses and give the appropriate ranges of these four parameters. The suggested suitable ranges of CaO/SiO2, MgO content, MgO/Al2O3 and MnO content for COREX-3000 are 1.20–1.30, 10 wt%–12 wt%, 0.80–0.90 and 0.4 wt%–0.7 wt%, respectively.
  • Effect of Rb2O on Inclusion Removal in C96V Saw Wire Steels Using Low-Basicity LF Refining Slag

    pp. 2032-2041

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    DOI:10.2355/isijinternational.ISIJINT-2018-385

    A novel Rb2O-containing synthetic LF refining slag has been developed in order to produce ultraclean C96V saw wire steel. In addition, the thermodynamic and kinetics mechanism of Rb2O on inclusion removal have been discussed fully. The results indicated that (1) Rb2O additions (≤10.00 wt%) seems to significantly enhance inclusion removal in steel melts. ① The average diameter of nonmetallic inclusions decreased significantly with the Rb2O addition in synthetic LF refining slag increasing. In particular, the diameter of most of inclusions was less than 3.0 × 10−6 m (3.0 µm) when Rb2O addition was 10.00 wt% ② The number of nonmetallic inclusions decreased sharply with the content of Rb2O in synthetic LF refining slag raising. ③ Both of the MnO–SiO2–Al2O3, CaO–SiO2–Al2O3 inclusions system mainly concentrated in the low melting point zone. (2) For the 15.00 wt% Rb2O-containing synthetic LF refining slag, not only the average diameter of inclusion increases slightly with reaction times increasing, but also the number. This is due to the fact that, the effect of Rb2O on the ability of refining slag to absorb inclusions is a double-edged sword: On the one hand, Rb2O addition would promote the thermodynamic conditions of inclusion removal, then, inclusions would enter the slag spontaneously easier. On the other hand, Rb2O addition could also exacerbate the kinetic conditions of inclusion removal by increasing the viscosity of slag at the same time.
  • Numerical Simulation of Desulfurization Behavior in Ladle with Bottom Powder Injection

    pp. 2042-2051

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    DOI:10.2355/isijinternational.ISIJINT-2018-406

    A computation fluid dynamics–population balance model–simultaneous reaction model (CFD–PBM–SRM) coupled model was used to predict the reaction kinetic and desulfurization behavior in 80 ton ladle with bottom powder injection. The reaction rate and evolution of multi-components including Al, S, Si, Mn and Fe at the powder droplet–liquid steel interface, bubble–liquid steel interface, top slag–liquid steel interface and air–liquid steel interface were revealed. Then, the effects of different kinetic conditions on the desulfurization efficiency were investigated, and the importance of various mechanisms was discussed and clarified. The results show that at the lower powder injection rate, the desulfurization is mainly attributed to the joint effort of both powder–liquid steel reaction and top slag–liquid steel reaction which is the prevailing mechanism. At the higher powder injection rate, the powder particle–liquid steel and bubble–liquid steel interface reaction become more important and then predominate the desulfurization behavior. With the increase of gas flow rate, the total desulfurization ratio gradually decreases, and with the increasing of powder injection rate, the total desulfurization ratio increases.
  • In-situ Analysis and Numerical Study of Inclusion Distribution in a Vertical-bending Caster

    pp. 2052-2061

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    DOI:10.2355/isijinternational.ISIJINT-2018-283

    Based on a fast-detection platform (FDP) founded by us, an in-situ measurement of inclusion distribution in slab is successfully performed. The inclusion distribution is obviously asymmetry and non-uniform. Specially, due to the structure differences in the vertical and bending part of a slab caster, the inclusion distribution in these two parts are quite different: In the vertical part, the inclusions entrapped in the outer arc is much more than that in the inner arc, while in the bending part, the inclusions entrapped in the outer arc is a little less than that in the inner arc. Large inclusions are tend to be found near the surface, and sometimes in the center, but they’re very few. Then in order to interpret the inclusion distribution in practical measurements, a new LES model is established using Euler-Lagrange approach. A new entrapment criterion is also defined to calculate the entrapped inclusions. Big inclusions are tend to float up to the mold top, and aggregate near the outer arc, which can explain the differences of inclusion distribution in the vertical part; Smaller inclusions are easier to flow deep into the mold, and become clusters when they’re getting near, which can explain the big inclusions in the central part. What’s more, the drag effect of bending slab is proven to be responsible for the differences of inclusion distribution in the bending part. This mathematical model is helpful for understanding the inclusion movements in slab.
  • Numerical Study of Inclusion Removal in Steel Continuous Casting Mold Considering Interactions Between Bubbles and Inclusions

    pp. 2062-2070

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    DOI:10.2355/isijinternational.ISIJINT-2018-319

    Bubble coalescence-breakup and bubble-inclusion interaction models were implemented into Eulerian-Lagrangian models of steel liquid flow and discrete particles transport, which was applied to examine the interaction and removal of discrete bubbles and inclusions during continuous casting. Bubble distribution affected by coalescence-breakup and its connection with the inclusion removal rate were analyzed. The inclusion removal rates at different initial bubble diameters and inclusion diameters were predicted. Larger inclusions have a higher removal rate and the predicted removal rates ranging from 14% to 30% agree well with industrial experiment measurements. It is also found that smaller bubbles have a higher capacity to remove inclusions and very small bubbles may cause more production defects when it is attached to inclusions. These results show that the developed model can reasonably predict the behaviors of discrete bubbles and inclusions and their interactions in molten steel. Such a model should be useful for the operation of steel continuous casting.
  • Transient Thermo-fluid and Solidification Behaviors in Continuous Casting Mold: Oscillation Behaviors

    pp. 2071-2078

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    DOI:10.2355/isijinternational.ISIJINT-2018-169

    A computational model of the continuous casting process has been developed, which includes transient heat transfer, multiphase flow, solidification, and mold oscillation. Succeeding the previous report on the evolution phenomena in the mold, this article describes fluctuations in the pressure, heat flux, and slag films during the oscillation cycle and the coupling effect of these variables on slag flow and shell growth. The results show that the predicted flux pressure is decided by the combined effect of mold velocity and liquid film thickness. The presence of slag rim enhances the nonuniform pressure flow near the meniscus during mold oscillation. Increases in pressure and heat flux occur in the negative strip time while the mold and slag rim move downwards approaching the lowest position, which squeezes the slag flow to be divided into two tributaries, promoting the slag infiltration and the initial shell solidification. Negative consumption rate is identified partly in the cycle based on the velocity distributions of liquid slag. The model provides quantitative analysis regarding the influence of meniscus shape and slag films related to the casting speed on slag consumption and oscillation mark formation.
  • Characterization on Microstructure and Carbides in an Austenitic Hot-work Die Steel during ESR Solidification Process

    pp. 2079-2087

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    DOI:10.2355/isijinternational.ISIJINT-2018-370

    The current work was undertaken to systematically examine the as-cast microstructure and carbides in a developed austenitic hot work die steel produced by conventional electroslag remelting (ESR) and continuous directional solidification of electroslag remelting (ESR-CDS). In addition, the growth pattern of carbides was also discussed. A combination of optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize microstructure and carbides. The segregation was analyzed using an original position analyzer (OPA) and electron probe microanalysis (EPMA). The electrolytically extracted carbides were analyzed by SEM and x-ray diffraction (XRD) to identify their three-dimensional microstructure and compositions. The microstructure of electroslag remelted austenitic die steel was composed of austenite matrix and primary carbides V8C7-type and Mo2C-type. Compared with conventional ESR, ESR-CDS contributed to a finer as-cast microstructure, a smaller amount and smaller size of carbides in remelted steel. Meanwhile, the alloying elements segregation was reduced through ESR-CDS. The enrichment of carbide-forming elements was reduced through directional solidification of ESR, resulting in the change in the morphology of V-rich carbides from rod-like to lamellar-shaped. The hardness and V-notched impact energies of remelted ingot (produced by ESR-CDS) after heat treatment (solution temperature 1180°C for 2 hours, aging temperature 720°C for 2 hours) was increased by 3 to 5HRC and 4 to 6 J/cm2 respectively, in comparison with that produced by conventional ESR.
  • Image-based Method for Measuring Pellet Size Distribution in the Stable Area of Disc Pelletizer

    pp. 2088-2094

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    DOI:10.2355/isijinternational.ISIJINT-2018-384

    Disc pelletizer is widely used in the agglomeration process to form powdered iron ore into iron ore green pellets. The pellet size distribution (PSD) is one of the major measures of product quality. An imaging system is developed for measuring PSD in the stable area of the disc pelletizer. Image pre-processing is performed to extract the densely distributed pellets as foreground, followed by identifying surface pellets using pellet markers and K-means clustering method. Then a marker-controlled watershed algorithm is applied to segment overlapping pellets in the image. The pellet sizes and thus PSD are then obtained using circumscribed circle fitting. The proposed image-based measuring method was tested in a steel company. The measured PSD was compared with manual sieving results. It shows good accuracy for different size ranges under different pelletizing conditions. The proposed method also makes it possible to evaluate online the pellet quality.
  • High Temperature Oxidation Behavior of High Nitrogen 9%Cr Steels

    pp. 2095-2101

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    DOI:10.2355/isijinternational.ISIJINT-2018-246

    High temperature oxidation behavior of high nitrogen steel with about 0.3 mass% of nitrogen has been investigated comparing with nitrogen-free steels and ASME grade 91. High temperature oxidation tests were carried out in air over the temperature range 750 to 850°C for 300 h at maximum. Weight gain was measured and oxide scales were observed using an optical microscope and analyzed with an electron probe X-ray microanalyzer. It was found that the oxidation resistance of the high nitrogen steel is superior to that of nitrogen-free steels and ASME grade 91. Furthermore, Cr concentration in the oxide scale of the high nitrogen steel was higher than that in other steels. These results indicate high nitrogen promotes the formation of the oxide scale with high concentration of Cr inhibiting oxidation from proceeding in the high nitrogen steel.
  • Effect of Cr Content and Microstructure on High Temperature Oxidation Behavior of High Nitrogen Heat-resistant Ferritic Steels

    pp. 2102-2109

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    DOI:10.2355/isijinternational.ISIJINT-2018-247

    Effect of Cr content and microstructure on high temperature oxidation behavior of high nitrogen steels with 0.2–0.3 mass% of nitrogen has been investigated. For high temperature oxidation test 9–15%Cr high nitrogen steels are prepared. High temperature oxidation tests were carried out in air mainly at 800°C for 300 h at maximum. Weight gain was measured and oxide scales were observed using an optical microscope and analyzed with an electron probe X-ray microanalyzer. The addition of high nitrogen improved the oxidation resistance of 9–15%Cr high nitrogen steels. It was found that the oxidation resistance of the high nitrogen steels does not depend greatly on Cr content but on their microstructure. The oxidation resistance of high nitrogen ferritic heat-resistant steels increased as the fraction of martensite structure increased. These results indicate for high nitrogen steels Cr diffusion along grain boundaries is further promoted resulting in the formation of protective oxide scale having high Cr concentration.
  • Microstructural Changes in Low-carbon Steel Occurring by Heating in Mixtures of Iron, Graphite and Alumina Powders

    pp. 2110-2116

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    DOI:10.2355/isijinternational.ISIJINT-2018-290

    Carbon and nitrogen are easily diffused into stainless steel and titanium, when these are embedded in mixtures of iron, graphite and alumina powders and held at high temperatures in a nitrogen flow. To promote an understanding of this new diffusion technique, which we call “iron-powder pack treatment”, we focused attention on the microstructures of low-carbon steel subjected to such a treatment. The diffusion of carbon into the steel was understood by evaluating area fraction of pearlite emerging in ferrite. A pearlite area in the steel, which was heat-treated at 1273 K for 3.6 ks using a mixture of iron and alumina powders, was larger than before heating, because the steel was carburized by carbon in the iron powder. On the other hand, an increase in the pearlite area was hardly observed in the case of a mixture of graphite and alumina powders. By replacing a part of graphite in this mixture with the iron powder, however, pearlite was most remarkably produced in the steel. Instead of the iron powder, the use of nickel powder did not exert a significant impact on the diffusion of carbon into the steel. These indicate that the iron powder acts as an important agent for enhancing the migration of carbon from a powder mixture to low-carbon steel. The relationship between a diffusion phenomenon of carbon and the generation of carbon monoxide gas in heat treatment is also discussed.
  • Effect of Surface Textures of Steel Sheets on the Crystal Orientation of Electrodeposited Zinc

    pp. 2117-2124

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    DOI:10.2355/isijinternational.ISIJINT-2018-429

    Prior to electrodeposition, steel sheets underwent polishing using emery paper, buff, and then electrolytic polishing. Zn deposition was performed galvanostatically at 1500 A/m2 in an agitated sulfate solution at 40°C to investigate the effect of the surface textures of steel sheets on the crystal orientation of Zn. The strain of the steel surface and the decrease in Fe grain size due to this strain were largest with emery paper polishing, then with buff polishing, then when unpolished, and were smallest after electrolytic polishing. The preferred orientation of the {0001} Zn basal plane of the hcp structure was largest with electrolytic polishing, and decreased in the following order: unpolished, buff polishing, and then with emery paper polishing. Thus, the preference of the {0001} orientation of Zn increased with decreasing the strain of steel sheets and increasing the grain size of Fe. With electrolytic polishing, the strain applied to the steel sheets was decreased, the grain size of Fe increased, and therefore the epitaxial growth of deposited Zn occurred easily. The initial Zn deposits appeared to grow epitaxially as indicated by the orientation relationship of {111}Fe//{0001}Zn because the preferred orientation of the steel substrate used in this study is {111} Fe. The preferred orientation of {0001} Zn seems to be more common under conditions where the epitaxial growth of deposited Zn is easy to occur.
  • In situ Neutron Diffraction Study on Ferrite and Pearlite Transformations for a 1.5Mn-1.5Si-0.2C Steel

    pp. 2125-2132

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    DOI:10.2355/isijinternational.ISIJINT-2018-336

    The phase transformation behavior from austenite upon cooling in a 1.5Mn-1.5Si-0.2C steel was in situ monitored using dilatometry, X-ray and neutron diffractions. The starting temperature of ferrite transformation was in good agreement between dilatometry and neutron diffraction, whereas much higher in X-ray diffraction. Such a discrepancy in transformation temperature is attributed to the change in chemical composition near the surface of a specimen heated to elevated temperatures in a helium gas atmosphere for X-ray diffraction. In situ neutron diffraction enables us to investigate the changes in lattice constants of ferrite and austenite, which are affected by not only thermal contraction but also transformation strains, thermal misfit strains and carbon enrichment in austenite. Pearlite transformation started after carbon enrichment in austenite reached approximately 0.7 mass% and contributed to diffraction line broadening.
  • Local Buckling of Steel Plates in Composite Structures under Combined Bending and Compression

    pp. 2133-2141

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    DOI:10.2355/isijinternational.ISIJINT-2018-202

    In this paper, explicit local buckling analysis of steel plates in composite structures under combine bending and compression and with elastic restraint against rotation is presented. Unique displacement function, which combines sinusoidal and cosine functions along x- and y-directions and satisfies boundary and loading conditions, is proposed to account for the effect of restraint of concrete and the elastic rotational restraint stiffness along both the loaded and unloaded edges of the steel plates. The explicit local buckling solution for the elastically restrained steel plates in composite structures is simplified to several special cases (e.g., the CS, CC, SS and KS steel plates) subjected to combined bending and compression. To verify the accuracy of the explicit solutions, experimental data, available solutions in the literature, and finite element results are compared, and reasonable agreement has been observed, particularly for the simplified cases. Parametric study is further conducted, and the effects of different parameters such as the aspect ratio and the loading stress gradient parameter on the local buckling stress resultants of steel plates with different boundary conditions are discussed.
  • Remarkable Improvement of Creep Strength by Vanadium Addition in 2.25Cr Heat-Resistant Steel

    pp. 2142-2146

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    DOI:10.2355/isijinternational.ISIJINT-2018-265

    This paper reports the effect of vanadium (V) addition on elimination of easily coarsening M23C6 carbide and on remarkable creep strength improvement in T/P23 heat-resistant steel (2.25Cr-1.5W-VNbTi). Increase in V content eliminates coarse M23C6 and allows only precipitation of MX carbo-nitrides in T/P23 heat-resistant steel. Fine MX effectively stabilizes sub-boundaries of bainite microstructure, so coalescence of neighboring sub-boundaries and subsequent creep strength loss are suppressed. This steel even surpasses the creep life of conventional 9 wt.% Cr steels due to powerful sub-boundary hardening.
  • Effect of Manganese on the Thermodynamic Property of Tellurium in Molten Iron

    pp. 2147-2149

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    DOI:10.2355/isijinternational.ISIJINT-2018-315

    The effect of manganese on the thermodynamic property of tellurium in molten iron was experimentally evaluated as an interaction parameter using a vapor-liquid equilibration technique, where the vapor pressure of tellurium was controlled using the transpiration method. Manganese was found to stabilize tellurium in molten iron and its effect was relatively small compared to other alloying elements.
  • A Novel Measurement of Voidage in Coke and Ferrous Layers in Softening and Melting under Load Test Using Synchrotron X-ray and Neutron Computed Tomography

    pp. 2150-2152

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    DOI:10.2355/isijinternational.ISIJINT-2018-257

    For the first time, the bed voidage of samples from interrupted softening and melting (S&M) under load tests was measured directly using computed tomography (CT). The large size, fused structure and high metallic iron content of the samples required the very high energy synchrotron X-ray source for scanning; samples produced at higher temperatures, e.g., 1450°C, required neutron CT to allow adequate penetration of the samples. This method was able to uniquely and accurately identify the volumes, distributions, and structures of coke, ferrous, and void in the S&M samples, and quantify the tortuosity of the voids. This information is critical for analysis of the pressure drop–contraction relationship in the S&M under load test, and will allow the improvement of the treatment of the cohesive zone in numerical models of the blast furnace.
  • Using Red Mud-based Flux in Steelmaking for High Phosphorus Hot Metal

    pp. 2153-2155

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    DOI:10.2355/isijinternational.ISIJINT-2018-339

    To smelt high phosphorus hot metal effectively, a new flux named Red Mud (RM) was applied in steelmaking to form CaO–FeO–SiO2–Al2O3–Na2O slag. Good slag fluidity and dephosphorization effects can be achieved when using RM-based flux in simulated steelmaking for high phosphorus hot metal. The dephosphorization rates of the RM-based flux were all greater than 82%. Especially, when RM:CaO=1:1.2, high dephosphorization rate (~95%) and low final [P] (=0.02%) was achieved in the situation of high [C] =1.36%. This is of great importance for the production of clean steel. The P2O5 content in the P-rich phase in RM-based slag can reach 29.1 wt%, far higher than the 9.1 wt% in lime-based slag.

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  1. blast furnace
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