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

ISIJ International Vol. 58 (2018), No. 12

  • A Review of the Chemistry, Structure and Formation Conditions of Silico-Ferrite of Calcium and Aluminum (‘SFCA’) Phases

    pp. 2157-2172

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    DOI:10.2355/isijinternational.ISIJINT-2018-203

    This paper critically reviews published research on silico-ferrite of calcium and aluminum (‘SFCA’) phases, the major bonding phases found in modern iron ore sinters. In particular, we focus on describing the different ‘SFCA’1 phases formed in iron ore sinter and examining their phase chemistry, crystal structures, characteristic textures and microstructures, and formation conditions. Information for the two main bonding phases SFCA and SFCA-I are reviewed and, based on a critical analysis of the data, we suggest future research directions required to generate the information necessary to fully describe the properties of both phases.1Throughout this text the acronym ‘SFCA’ in single quotation marks refers to undifferentiated ‘SFCA’-like phases. These may consist of substituted calcium ferrites, SFCA sensu stricto and SFCA-I.
  • Effect of TiO2 and MnO on Viscosity of Blast Furnace Slag and Thermodynamic Analysis

    pp. 2173-2179

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    DOI:10.2355/isijinternational.ISIJINT-2018-379

    The effect of TiO2 and MnO on the viscous behavior and structure of CaO–SiO2–MgO–Al2O3–TiO2–MnO slags were studied using rotating cylinder method and FTIR spectroscopic analysis. Furthermore, the heat capacity and enthalpy change of the slag were calculated to clarify the influence of TiO2 and MnO on the heat quantity of the slag at elevated temperatures, and then the equilibrium temperatures and corresponding viscosities of the slag under various fixed heat quantities were also analyzed. The higher TiO2 and MnO contents resulted in lower viscosity. The FTIR results revealed that TiO2 and MnO depolymerized the slag by modifying the silicate network structure and breaking the linkage between the silicate and aluminate structure, while have little effect on aluminate structure of the slag. In the temperature range of interest, the enthalpy change of the slag increased with increasing TiO2 content, but remained basically unchanged with MnO additions. The fluctuations of the slag heat quantity had a significant influence on the slag temperature and viscosity. With the increase of TiO2 content, the equilibrium temperature of the slag at fixed heat quantity decreased and the corresponding viscosity increased. However, as the MnO content increased, the equilibrium temperature of the slag at fixed heat quantity was almost constant and the corresponding viscosity decreased.
  • Viscosity of SiO2–CaO–Al2O3 Slag with Low Silica – Influence of CaO/Al2O3, SiO2/Al2O3 Ratio

    pp. 2180-2185

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    DOI:10.2355/isijinternational.ISIJINT-2018-381

    The viscosity of low SiO2 (10–20 mass%)-CaO-Al2O3 slag system was measured in a wide temperature range (1623–2800 K) using the rotational bob method and the aerodynamic levitation method. The influence of SiO2/Al2O3 ratio and CaO/Al2O3 ratio on the viscosity was examined. It was concluded that the SiO2/Al2O3 ratio did not affect the degree of polymerization of the aluminosilicate network in the composition range of the present study. An abnormal behaviour of the viscosity was observed at a CaO/Al2O3 ratio of 1.57 which was attributed to the formation of 12CaO·7Al2O3-like clusters. It was concluded that the overall influence on the viscosity could be expressed as the summation of the influence from the aluminosilicate network and the influence from the cluster formation of the primary precipitating solid phase. The temperature dependence of the cluster formation was coupled to the driving force of precipitation of the 12CaO·7Al2O3 phase.
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    1. Development and Validation of Kinematical Blast Furnace Model with Long-term Operation Data ISIJ International Vol.58(2018), No.12
    2. Kinetics of Dissolution of SiO Gas in Liquid Fe–C Alloys ISIJ International Vol.58(2018), No.12
    3. Improvement of Sinter Productivity by Control of Magnetite Ore Segregation in Sintering Bed ISIJ International Vol.58(2018), No.12
  • High Temperature Thermal Diffusivity Measurement for FeO Scale by Electrical-Optical Hybrid Pulse-Heating Method

    pp. 2186-2190

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    DOI:10.2355/isijinternational.ISIJINT-2018-380

    Thermal diffusivity of FeO scale formed on iron has been determined at high temperature using an electrical-optical hybrid pulse-heating method, which can avoid the compositional change of the sample even at elevated temperatures by executing the experiment rapidly. The sample was a 90 µm-thick FeO scale layer, which had been thermally grown on a 0.5 mm-thick iron coupon at 1123 K in an Ar–H2–H2O gas mixture. In the experiment, a large current pulse was supplied to the iron coupon, and the FeO scale was indirectly heated up to about 932 K from room temperature within 0.5 s. The temperature was maintained at the experimental temperature and the laser flash method was conducted to measure the effective thermal diffusivity of the coupon. Thermal diffusivity of FeO scale at 932 K was calculated to be 5.27 × 10−7 m2s−1 based on a multi-layered analysis for the effective thermal diffusivity on the three-layered structure (FeO/Fe/FeO). X-ray diffraction analysis for the post-experiment coupon confirmed that no compositional change had occurred during the experiment. The uncertainty of the measured value was discussed. The effect of boundary resistance on the measured value was also estimated in this study.
  • Recovery of Fe, Ni, Co, and Cu from Nickel Converter Slag through Oxidation and Reduction

    pp. 2191-2199

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    DOI:10.2355/isijinternational.ISIJINT-2018-533

    The conventional method of nickel converter slag dilution is reduction–sulfurization by adding coal and pyrite into the slag. In this study, the effect of sulfur content in the initial slag ((pct S)0) on the slag dilution process was determined by producing metal, which is significantly different from the conventional method producing matte. Analysis of the nickel converter slag showed that nickel, cobalt, and copper were mainly present in the form of sulfides, which are difficult to separate from the slag. The NiO, CoO, and Cu2O in the slag are easily reduced into metal using carbon, while the presence of sulfur inhibits the reduction reaction. In a vertical resistance furnace, the desulfurized slags with different sulfur contents were reduced using carbon. The sulfur distribution rate increased with the decrease in (pct S)0; the distribution of nickel, cobalt, and copper decreased with the decrease in (pct S)0. The nickel recovery rate increased with the decrease in (pct S)0, while (pct S)0 almost had no effect on the recovery of iron, cobalt, and copper. The distribution rates of sulfur, nickel, and copper increased with the increase in mole ratio of carbon to reducible oxygen (nC/nO), while the distribution rate of iron and cobalt decreased with the increase in nC/nO. In addition, the recovery rates of iron, nickel, cobalt, and copper increased with the increase in nC/nO.
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    Readers Who Read This Article Also Read

    1. Development and Validation of Kinematical Blast Furnace Model with Long-term Operation Data ISIJ International Vol.58(2018), No.12
    2. Kinetics of Dissolution of SiO Gas in Liquid Fe–C Alloys ISIJ International Vol.58(2018), No.12
    3. Effect of Coke Size on Reducing Agent Ratio (RAR) in Blast Furnace ISIJ International Vol.58(2018), No.12
  • Improvement of Sinter Productivity by Control of Magnetite Ore Segregation in Sintering Bed

    pp. 2200-2209

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    DOI:10.2355/isijinternational.ISIJINT-2017-691

    Recently, the quality of sinter feed ore used in sintering process has deteriorated. In particular, T.Fe has decreased and gangue component has increased in the sinter feed ore. Increase of gangue is not only the factor to influence sinter qualities, but also the factor to increase coke ratio in the blast furnace operation as the increase of slag ratio. Therefore, to cope with the deterioration of iron ore qualities, studies on alternative iron ore resources and development of its utilization technology have been required.In that kind of new iron ore resources, authors focus on high grade magnetite fine. In the past, there are some studies about the effect of mixing ratio and size of magnetite fine on productivity and quality, but there are few studies about magnetite fine segregation in charging. In addition, magnetite fine decreases sinter productivity by the decrease of permeability of sintering bed. A new study for using large amount of magnetite fine is required.In this research, the control method of magnetite fine segregation by magnetic force at charging and the improvement of sinter productivity by this method was studied. The effect of upper segregation of magnetite fine was studied through the analysis of melting behavior and interfacial reaction of calcium ferrite melts into hematite substrate and magnetite substrate.
  • Development and Validation of Kinematical Blast Furnace Model with Long-term Operation Data

    pp. 2210-2218

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    DOI:10.2355/isijinternational.ISIJINT-2018-177

    In order to operate a blast furnace properly, the future prediction of process variables by a transient model based on kinetics is useful. In general, such a kinematic blast furnace model includes uncertain factors regarding reaction rates and heat transfer. However, any guideline of adjusting such factors to reproduce actual transition of process variables has not been fully discussed in the literature. In this research, we developed a transient two-dimensional (2D) model for online use, and then discussed an adjustment method to reproduce the behavior of process variables when the reducing agent ratio (RAR) is changed from the viewpoint of mass and heat balance with the Rist diagram. It was found that appropriate consideration of the chemical reserve zone and the heat balance of the furnace was effective to fit the developed model to the actual data.
  • Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction

    pp. 2219-2227

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    DOI:10.2355/isijinternational.ISIJINT-2018-372

    The effect of different gangue oxides(Al2O3, SiO2 and Fe2O3) on the gasification and migration of phosphorus during the carbothermal reduction of fluorapatite has been investigated. The vaporization of phosphorus during the carbothermal reduction of synthesized model sample demonstrating a high-phosphorus iron ore was analyzed by gas mass spectrometry. Results revealed that the dephosphorization of fluorapatite was promoted by Al2O3 and SiO2 to form CaAl2O4 and CaSiO3, respectively. The promotion effect of SiO2 was larger than that of Al2O3. With the increase in the addition of gangues, the thermodynamic conditions for the reduction of fluorapatite were continuously optimized, thereby accelerating the dephosphorization of fluorapatite. At a C/O (O originated from fluorapatite and Fe2O3) of larger than 1 in molar ratio, P2 was the the dephosphorization product. Whereas, at a C/O of less than 1, the dephosphorization product turn to PO. With the addition of Fe2O3 to fluorapatite, a large amount of phosphorus was absorbed by liquid iron, resulting in a decrease of the amount of volatilized P2, leading to the slow increase or decrease in the dephosphorization ratio of the pellets. Phosphorus was absorbed by liquid iron as P2, whereas PO gas was completely volatilized. Gasification dephosphorization mainly occured from 10 min to 25 min at 1200°C. These findings leads to a new idea on the dephosphorization of a high -phosphorous iron ore, that is, decreasing the reduction temperature to retard melting of iron and simultaneously adding the additives to promote the dephosphorization of fluorapatite.
  • Effect of Coke Size on Reducing Agent Ratio (RAR) in Blast Furnace

    pp. 2228-2235

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    DOI:10.2355/isijinternational.ISIJINT-2018-360

    The coke size’s effect on RAR (Reducing Agent Ratio, Fuel Ratio) should be estimated for the efficient blast furnace operation. The reaction and the heat exchange efficiency decrease by 0.2% and 3% per 1 mm increase of the coke size. This makes RAR increase by about 1 kg/t-p according to the 2-D numerical analysis under the stable blast condition. The coke sampling through the tuyere shows that the coke size is not linearly proportional to the charged coke size. The 2-D numerical analysis model shows that the gas utilization ratio is decreased by 2.5% for the case of deteriorated deadman state according to the increase of charging coke size by 5 mm. Moreover, the number of tapping is increased due to the increased coke size which makes the molten material drainage deteriorate at the coke bed of the tuyere level. From these results, the relationship between the coke size and RAR can be quantified and the optimal coke size can be determined according to the productivity for the stable blast furnace operation.
  • Off-line Model of Blast Furnace Liquid Levels

    pp. 2236-2245

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    DOI:10.2355/isijinternational.ISIJINT-2018-417

    An off-line simulation model of the blast furnace hearth is developed based on mass balances for iron and slag, expression of the liquids outflow rates and logical conditions for the start and the end of the outflow of liquids. The dynamic model divides the furnace hearth into two regions of sizes that may change during the tapping process. It provides a description of the time evolution of the liquid levels and predicts the duration and the periods of iron- or slag-only flow in the beginning of the taps. The values of some model parameters are estimated on the basis of measurements in a reference blast furnace, while others are fixed. A sensitivity analysis of the model is provided, revealing the role of some key parameters. The model is demonstrated to describe the overall drainage behavior of the reference furnace reasonably well, and the presence of pools with different liquid levels can also be deduced from the real data. Finally, some recommendations for future work are suggested.
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    1. Degradation and Microstructure Changes of Tuyere Coke Behavior of a COREX-3000 Furnace ISIJ International Vol.58(2018), No.12
    2. Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction ISIJ International Vol.58(2018), No.12
    3. Kinetics of Dissolution of SiO Gas in Liquid Fe–C Alloys ISIJ International Vol.58(2018), No.12
  • Kinetics of Dissolution of SiO Gas in Liquid Fe–C Alloys

    pp. 2246-2252

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    DOI:10.2355/isijinternational.ISIJINT-2018-463

    The dissolution rate of SiO gas in liquid iron (Fe-2 wt% C and Fe-4 wt% C alloys) was investigated at 1843, 1868, and 1893 K. SiO gas was generated from a silica-graphite particle mixture, and then, it was introduced onto the surface of liquid iron through an alumina lance with CO carrier gas. The effect of gas-phase mass transfer on the dissolution rate of SiO gas was minimized by adjusting the CO gas flow rate. The rate of silicon transfer remained almost constant regardless of the initial carbon content in liquid iron, whereas it increased with increasing temperature. From the experimental results, it was concluded that the adsorption of SiO gas onto the surface of liquid iron was the rate-determining step.
  • Degradation and Microstructure Changes of Tuyere Coke Behavior of a COREX-3000 Furnace

    pp. 2253-2257

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    DOI:10.2355/isijinternational.ISIJINT-2018-409

    The behavior of tuyere coke obtained from a COREX-3000 process was investigated in the present study for an in-depth understanding for the condition of raceway. The coke samples was obtained in a dissection process of the furnace, and coke samples at P1 (200 mm from tuyere sleeve towards the furnace center), P2 (400 mm from tuyere sleeve towards the furnace center), P3 (600 mm from tuyere sleeve towards the furnace center), P4 (800 mm from tuyere sleeve to the furnace center), P5 (1000 mm from tuyere sleeve to the furnace center) and P6 (1200 mm from tuyere sleeve to the furnace center) were sieved, and the particles size distribution and average size of different position has been calculated. Microstructure of coke samples at P2, P4 and P6 was examined using scanning electron microscopy, and carbon structure and mineral phases of coke samples at P6 were identified using X-ray diffraction (XRD) analysis. The results showed that the percentage of small coke particles (<10 mm) was higher at P5 and P6, and the average particle size of coke samples at P5 and P6 were 12.04 mm and 7.71 mm, which is much smaller than that of other samples indicating a severe degradation of coke. The amount of pores of tuyere coke increased compared with charged coke, and more pores were found in coke sample at P6 than P2 and P4, indicating a violent reaction at this position. The graphitization degree of tuyere cokes at P6 were much higher than that of charged coke, and coke particle (10–16 mm) possess the highest graphitization degree, indicating the much higher temperature in the raceway zone. The main minerals in the tuyere coke were gehlenite and akermanite, and the slag was melt to be spherical particles confirming the higher temperature in raceway zone in COREX-3000 process.
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    Readers Who Read This Article Also Read

    1. Kinetics of Dissolution of SiO Gas in Liquid Fe–C Alloys ISIJ International Vol.58(2018), No.12
    2. Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction ISIJ International Vol.58(2018), No.12
    3. Off-line Model of Blast Furnace Liquid Levels ISIJ International Vol.58(2018), No.12
  • Measurement on Interaction Parameter between Co and Al in Molten High Al Steel

    pp. 2258-2261

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    DOI:10.2355/isijinternational.ISIJINT-2018-281

    Nowadays Al is commonly used as deoxidizer and sometimes alloying element. On the other hand, due to the increase in scrap addition, suppress in the concentration of tramp element in molten steel during refining process becomes more important than ever. Co is one of the tramp elements in steel scrap and its content is increasing due to the increase in the production of Co materials world widely. As fundamentals to understand the thermodynamic behaviors of Co in the molten steel containing high Al, the interaction parameter between Co and Al has been measured in this study through a chemical equilibrium method. From the equilibrium composition of the Fe–Co–Al alloy and Ag, the interaction parameter between Co and Al in molten Fe–Co–Al alloy was determined as follows,[ This part of text is omitted ]By converting the temperature and the reference state, the following values were also obtained,[ This part of text is omitted ][ This part of text is omitted ][ This part of text is omitted ]
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    1. Water Drainage Time of Pipe Laminar Type Cooling Equipment ISIJ International Vol.58(2018), No.12
    2. Effect of Particle Velocity on Penetration and Flotation Behavior ISIJ International Vol.58(2018), No.12
    3. Effect of Crystal Structural Changes of PET in Can-making Process on Properties of Film Laminated Steel for Containers ISIJ International Vol.58(2018), No.12
  • Effect of Size of Ferrotitanium on the Melting Behavior and the Yield in the Refining of Interstitial Free Steel by RH De-gasser

    pp. 2262-2270

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    DOI:10.2355/isijinternational.ISIJINT-2018-292

    The reduction of ferroalloy consumption used in the steel making is an important approach to high-performance and low-cost steel manufacture. In this paper, the effect of size of ferrotitanium on the yield in the refining of interstitial free steel by RH de-gasser was investigated. Motion trajectory of ferrotitanium after the addition into molten steel in RH de-gasser was investigated through water model experiment. The effect of size of ferrotitanium on the melting time was investigated by numerical simulation. Combining water model experiment with numerical simulation, the loss mechanism and effect of size on the yield of ferrotitanium were discussed. It was found that the size of ferrotitanium larger than a certain value has a great opportunity of floating up to the interface of molten steel and slag in ladle and being oxidized there. Results of industrial experiment verified the mechanism. As for a 300 tons RH de-gasser, Fe-70%Ti alloy whose size was larger than 43 mm had a low yield because of oxidation by the ladle slag.
  • Limestone Dissolution in Converter Slag: Kinetics and Influence of Decomposition Reaction

    pp. 2271-2279

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    DOI:10.2355/isijinternational.ISIJINT-2018-314

    Dissolution rate of limestone in converter slag is a key to evaluate the feasibility of limestone slagging mode during steelmaking process. In this work, kinetics of limestone dissolution in converter slag at 1300–1400°C were studied and the influence of decomposition reaction were investigated. The results showed that the dissolution process of limestone in converter slag can be divided into three stages: stagnation stage, coupling stage and sole dissolution stage. Higher slag temperature and lower slag basicity were conducive to reduce the duration time of stagnation stage and obtain higher dissolution degree. The coupling stage of limestone dissolution was confirmed to be controlled by the chemical reaction, whereas diffusion through the boundary layer as well as combination of controlling steps was the rate limitation at the sole dissolution stage under different slag basicities. The kinetics parameters were determined. In addition, CO2 bubbles generated from decomposition reaction could provide a certain enhancement of limestone dissolution and inhabit the formation of 2CaO·SiO2 phase at the coupling stage of limestone dissolution in converter slag.
  • Formation and Evolution of Oxide Inclusions in Titanium-Stabilized 18Cr Stainless Steel

    pp. 2280-2287

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    DOI:10.2355/isijinternational.ISIJINT-2018-332

    During Ti-stabilized stainless steelmaking process, oxide inclusions in steel generally cause the clogging of submerged entry nozzle and surface defects of cold-rolled products. Therefore, the evolution mechanism of oxide inclusions in Ti-stabilized 18Cr stainless steel was investigated by industrial experiments. The characteristics of inclusions in specimens were analyzed by scanning electron microscopy and energy dispersive spectroscopy. After Al deoxidation, the main inclusions were irregular MgO–Al2O3 spinel. After calcium treatment, MgO–Al2O3 inclusions were modified to be spherical multilayer CaO–MgO–Al2O3 inclusions consisting of spinel crystal embedded in CaO–Al2O3 liquid matrix. Thermodynamic calculation indicated that several ppm Ca could significantly expand the liquid oxides phase in Mg–Al–O phase diagram. After Ti addition, multilayer CaO–MgO–Al2O3–TiOx inclusions were formed. The compositions of steel were located close to Al2O3–TiOx liquid oxide phase, which would help to reduce oxide inclusions and increase titanium yield. Titanium addition has modified spinel inclusions to multilayer MgO–Al2O3–Ti3O5 inclusions containing solid spinel inner layer and MgO–Al2O3–Ti3O5 liquid oxide outer layer. As for improving the cleanliness of molten steel, the contents of magnesium, aluminum, and titanium could be considered simultaneously to liquefy oxide inclusions during Ti-stabilized stainless steelmaking process.
  • Effect of Particle Velocity on Penetration and Flotation Behavior

    pp. 2288-2297

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    DOI:10.2355/isijinternational.ISIJINT-2018-400

    To improve the properties of steel, lower sulfur content is required. Therefore, powder blast is often used for desulfurization in secondary refining process, and increasing efficiency is important for desulfurization treatment. As a fundamental research, water model experiment under reduced pressure was carried out and behavior of a particle from penetration to flotation was analyzed. A polypropylene particle (3.2 mm in diameter) was blasted onto the water surface with Ar gas through a single-hole nozzle, and behavior of the particle was recorded by a high-speed camera. According to penetration of the particle, an air column was generated and a bubble remained on the particle after rupture of the air column. The Particle with high velocity before penetration floated to the water surface rapidly even though they penetrated into water deeply as the residual bubble was easily generated. Therefore, increasing particle velocity before penetration does not result in increasing detention time of the particle, and it is suggested that the particle should be blasted by its own velocity without generating the air column to avoid remaining the bubble. In addition, flotation behavior of the particle was analyzed by a kinetic equation. As a result, when the residual bubble was greater than 2 mm in diameter, the apparent resistance coefficient increased with diameter of the residual bubble. This is because that increasing diameter of the residual bubble led to increasing projection cross section area of the particle including the bubble, and because the friction force between liquid and the particle was increased.
  • Effect of Nb on the As-cast Structure and Compactness Degree of Ferritic Stainless Steel Dual Stabilized by Ti and Nb

    pp. 2298-2307

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    DOI:10.2355/isijinternational.ISIJINT-2017-595

    The effect of Nb on the as-cast structure and compactness degree of ferritic stainless steel (FSS) dual stabilized by Ti and Nb are investigated. In this study, the as-cast structure of experimental ingots were almost composed of equiaxed grains and Ti-Mg-Al-oxide enveloped by Ti(C,N) or (Ti,Nb)x(N,C)y, namely complex nucleus, was found in the interior of FSS grain. When Nb was added to FSS, the as-cast grain size became smaller and the grain boundary precipitates (BP) became smaller and more dispersed. In addition, the composition of the outer layer of the complex nucleus and the BP both converted from Ti(C,N) to (Ti,Nb)x(N,C)y. Thermodynamics analysis showed that, the solidification region will be extended by Nb, which will be beneficial to the nucleation of complex nucleus. Complex nucleus is theoretically possible to form and exhibits good nucleation effect on δ-Fe as well as TiN according to the disregistry calculation. What’s more, (Ti,Nb)x(N,C)y particles in BP will be formed at the end of solidification and will prevent the grain merging by pinning effect.
  • Mathematical Model and Plant Investigation to Characterize Effect of Casting Speed on Thermal and Solidification Behavior of an Industrial Slab Caster

    pp. 2308-2317

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    DOI:10.2355/isijinternational.ISIJINT-2018-423

    Development of a validated 3D transient mathematical model for modeling the fluid flow and solidification process in an industrial continuous slab caster has been demonstrated. The model couples thermo-fluid aspect of mold and sub-mold region by utilizing a standard Enthalpy-porosity method. Extensive plant level measurements of mold heat fluxes and thermocouples data, breakout shell thickness profile, and macrostructures were carried out to evaluate proper input of heat transfer and other conditions for the model. A suitable validation of the model is established with slab surface temperature and solidified shell thickness profile as measured from a breakout shell in the caster plant. An insight is drawn for an industrial slab caster from the model results analysis for a range of operating parameters of casting speed and SEN submergence depth as employed in the caster. Evolution of a solidified shell thickness profile is simulated. Slab surface temperature mapping is drawn from the model and discussed its variation originating due to fluid flow inside the solidified shell. Casting speed is shown to have a dominant effect as temperature rise of order of 50°C are observed as it is increased from an average plant value of 1.4 m/min to peak of 1.8 m/min. Similar effect is also reflected in the solidified shell thickness profile as shell thickness gets thinner by an order of 6 mm in the sub-mold region due to increase in casting speed from an average to peak value. The effect of SEN submergence depth is also outlined.
  • Vanadium Alloy Steel DIN 30MnVS6 Applied in Cold Forging Process

    pp. 2318-2322

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    DOI:10.2355/isijinternational.ISIJINT-2018-342

    Vanadium alloy steels are still little known and debated when applied to the cold forming process, it is not clear what the performance of their mechanical performance is compared to traditional steels that the market already uses.The possibility of reducing costs and generating competitiveness, are the basis for studies that generate new opportunities for industries. In this article, the possibility of withdrawing the heat treatment process, directed the performance of the tests presented here.This paper deals with the performance comparison of DIN 30MnVS6 steel compared to ISO 898-1, which deals with mechanical performance for bolts. The tests were correlated with the bolts of resistance class 8.8, which currently have heat treatment. It is possible to evaluate the positive performance of the vanadium-alloyed steel DIN 30MnVS6, despite the occasional performance limitations in some attributes addressed in ISO 898-1.
  • Water Drainage Time of Pipe Laminar Type Cooling Equipment

    pp. 2323-2329

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    DOI:10.2355/isijinternational.ISIJINT-2018-487

    Cooling equipment of the pipe laminar type is utilized on run–out tables in hot strip mills. It is known that the responsiveness of starting and stopping cooling water injection affects cooling accuracy. In this study, experiments and calculations were performed in order to research the water drainage behavior of pipe laminar type cooling equipment. The experimental apparatus consisted of a single nozzle, orifice, header and air inlet tube. The calculation model considered Bernoulli’s theorem and pressure loss. The experimental results showed that the pressure loss of the air inlet tube and the nozzle affects water drainage time. The calculated results showed good agreement with the experimental results. Therefore, it is possible to estimate the water drainage time of pipe laminar equipment by the developed calculation model. Based on the calculation model, we suggested that the optimum diameter of the air inlet tube is 12 mm.
  • Effect of Crystal Structural Changes of PET in Can-making Process on Properties of Film Laminated Steel for Containers

    pp. 2330-2337

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    DOI:10.2355/isijinternational.ISIJINT-2018-519

    Polyethylene terephthalate (PET) film laminated steel sheets with excellent properties are now widely used in beverage cans. In recent years, can weight reduction has been promoted from the viewpoint of resource saving, and deep-drawing and ironing processing has been applied to the laminated steel sheets. Therefore, non-oriented PET films (NO-PET) with excellent formability are required instead of biaxially oriented PET films (BO-PET), but NO-PET films may affect impact resistance and corrosion resistance due to their lack of a crystal structure.This study investigated the effect of the crystallinity of the PET film on various properties required for food cans. PET films with different crystallinities laminated on steel sheets were formed into a can shape by a stretch-drawing process in order to evaluate formability, adhesion, impact resistance and corrosion resistance.The results showed that the BO-PET film laminated steel with high crystallinity was inferior in impact resistance and corrosion resistance compared with the BO-PET/IA (copolymerized with isophthalic acid) and the NO-PET/IA film laminated steel. Film cracks parallel to the can height direction were observed only on the surface of the BO-PET film after heat treatment. Heat treatment increased the crystallinity of the PET and oriented (100) crystal face of the PET parallel to the can height direction, which resulted in the film cracks observed on the surface of the BO-PET film.As a result of this study, it was concluded that the crystal structure change of the PET film in a can making process had significant effects on impact resistance and corrosion resistance, and control of the crystallinity of the PET was the key factor for obtaining excellent properties.
  • Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling

    pp. 2338-2347

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    DOI:10.2355/isijinternational.ISIJINT-2018-365

    Pre-oxidation in air at 750°C for 10 min, the plain carbon steels without Cr and containing 0.4 wt.% Cr tended to rapidly form oxide scale composed of outer Fe3O4 layer and inner FeO layer. Moreover, a FeCr2O4 layer was observed at the FeO/substrate interface on the steel containing Cr. A comparative study was carried out between the scales on the two steels in inert gas cooled from 350–600°C to room temperature at the cooling rate range of 1–40°C/min, to determine the effect of low concentration Cr addition on the phase transformation of FeO. Based on the cross-sectional morphologies of oxide scale during various cooling conditions, the relationship between cooling rate and start cooling temperature were constructed, and the area fraction of eutectoid structure was analyzed. The result shows that the transformation rate and area fraction of eutectoid structure in oxide scale on steel containing Cr were greater than that on steel without Cr, and then the nucleation, growth and 100% transformation region of eutectoid structure in oxide scale on steel without Cr were delayed. This study proposed two mechanisms to discuss the experimental results. Firstly, the formation of FeCr2O4 layer reduced the consumption of O, and then prevented short-range uphill diffusion of Fe from FeO to substrate. Secondly, combined with the lamellar spacing in eutectoid structure and the Fe–Cr–O equilibrium phase diagram, the Cr addition increased the formation temperature of FeO in oxide scale, which provided sufficient driving force for eutectoid transformation during continuous cooling.
  • Effect of Rare Earth Element La on Texture and Inclusion of Non-oriented Electrical Steel Produced by Thin Slab Casting and Rolling Process

    pp. 2348-2353

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    DOI:10.2355/isijinternational.ISIJINT-2018-392

    Effect of rare earth element La on non-oriented electrical steel produced by thin slab casting and rolling process is investigated by using transmission electron microscope, scanning electron microscope and X-ray diffraction. The results show that, (1) The columnar crystals are refined obviously with the addition of rare earth element La, the primary dendrite arm spacing is reduced from 2.42 mm to 1.76 mm, and the secondary dendrite arm spacing is reduced from 0.35 mm to 0.28 mm. (2) The banded structure of the hot rolled plate in center is significantly improved after adding rare earth, the thickness of the banded structure is reduced from 0.75 mm to 0.24 mm. (3) With the addition of rare earth element La, the precipitation morphology of AlN transforms from lump to spherical, the density and amount of inclusions are greatly reduced. (4) The average grain size of finished product is increased with the addition of rare earth element La, meanwhile, the unfavorable texture of (111) decreases and the favorable texture of (100) and (110) increases. With the addition of rare earth, the average core loss is decreased by 0.4 W/kg, and the average magnetic induction intensity is increased by 0.011T.
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  • Proposal of Simplified Modified Williamson-Hall Equation

    pp. 2354-2356

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    DOI:10.2355/isijinternational.ISIJINT-2018-517

    Williamson-Hall (WH) plots are characterized by irregular arrangement of data due to the elastic anisotropy in each {hkl} plane. In order to correct the effect of elastic anisotropy, Ungár developed a unique methodology using the contrast factor C, so called the modified Williamson-Hall (mWH) method. When X-ray with the wave length λ was used for diffraction analysis and diffraction angle θ and integral breadth β was obtained in each diffraction peak, the following mWH equation is constructed as functions of the parameter K (=2sinθ/λ) and ΔK (=βcosθ/λ).
    [ This part of text is omitted ]
    Here, the parameter α is dependent on the crystallite size. The parameter φ and O are constants but the O-value is much smaller than the φ-value. In the mWH plots in 60% cold rolled ferrite (Fe-0.0056%C), ultra low carbon martensite (Fe-18%Ni) and 20% cold rolled austenite (SUS316L), it was confirmed that the value of OK2C is negligibly small. As a result, the following simplified equation is applicable for the analysis by mWH method.
    [ This part of text is omitted ]

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