Showing papers in "Tetsu To Hagane-journal of The Iron and Steel Institute of Japan in 1989"
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TL;DR: In this paper, a new blast furnace process has been developed which blows normal temperature oxygen in place of the hot blast through the tuyeres and injects preheating gas into the upper shaft.
Abstract: Synopsis: A new blast furnace process has been developed which blows normal temperature oxygen in place of the hot blast through the tuyeres and injects preheating gas into the upper shaft. For the development of this process, mathematical model simulations and operation tests with an experimental blast furnace were done. The test operation was so stable that this process was technically verified to be consistent as an ironmaking process. The pulverized coal was injected up to the ratio of 0.94 kg-coal/Nm3-oxygen. The high productivity of 5.1 t/dm3 was realized. According to the analysis of measurements during the operation and dissection results, this process has been verified to have the follow ing characteristics; (1) The preheating gas injection lowers the heat flow ratio and raises the temperature in a whole section of the furnace. (2) The gaseous reduction takes place fast at relatively low temperature region and the content of the boudouard reaction is low. (3) The silicon content in metal is lower than that in the hot blast. The lower limit of the fuel rate was estimated 530 kg/t for a commercial blast furnace.
20 citations
TL;DR: In this article, a precipitation model of NbC in hot-rolled HSLA steels was developed to predict microstructure and mechanical properties in hot rolled steels, and the experimental results concerning the accelaration of precipitation due to strain and the interaction between recrystallization and precipitation were quantitatively explained.
Abstract: Synopsis : In order to predict microstructure and mechanical properties in hot rolled HSLA steels, a precipitation model of NbC in austenite was developed. The effects of Nb content, prior austenite grain size and condition of deformation on the precipitation kinetics were quantitatively determined by extraction replica. The modelling was basically constructed with the classical nucleation and growth theory, and the precipitation fraction was estimated from the supersaturation of Nb in solution. As effects of deformation on precipitation, a strain energy term was added to the driving force of nucleation. The increase in nucleation sites and the enhancement of diffusibity of Nb were expressed as functions of the dislocation density. The experimental results concerning the accelaration of precipitation due to strain and the interaction between recrystallization and precipitation were quantitatively explained by the present model. Rev words : modelling ; precipitation ; kinetics ; nucleation ; growth ; hot deformation ; Nb bearing steel ; high strength low alloy steel.
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TL;DR: In this paper, the microstructure and the interfacial strength have been studied for the diffusion bonding pairs between a commercially pure Ti and Fe-0.003 wt%C bonding pairs.
Abstract: Synopsis: The microstructure and the interfacial strength have been studied for the diffusion bonding pairs between a commercially pure Ti and Fe-0.003 wt%C or Fe-0.015 wt%C. The transformation of ƒ¿ -Ti into ƒÀ-phase and the formation of intermetallic compounds (TiFe and TiFe2) were induced by the interdiffusion in Ti/Fe-0.003 wt%C bonding pairs. During the cooling to room temperature, ƒÀ-phase layer with higher Fe content retained in ƒÀ-phase, whereas ƒÀ-phase layer with lower Fe content transformed into ƒ¿ '-Ti martensite. The specific crystallographic orientation relationship ; (0001)TiFe2//(101)ƒ¿ -Fe [1120]TiFe2//[111]ƒ¿ -Fe (Burger's relationship) was obtained between TiFe2 and ƒ¿ -Fe. The result indicates that TiFe2 was formed in a -Fe by the diffusion of Ti-atoms. In Ti/Fe-0.015 wt%C bonding pairs, /ƒÀ-transformed layer and intermetallic compound layer were not observed at the bonding temperatures below 1 073 K. In this case, TiC precipitates formed along the interface and they hindered the interdiffusion of Tiand Fe-atoms. However ƒÀ-transformed layer and intermetallic compound layer formed at the bonding temperature above 1 123 K. The interfacial strength of Ti/Fe-0 .003 wt%C bonding pairs depended on the width of intermetallic compound layer ( WIM). At the initial stage of bonding the strength was very low due to the inadequate diffusion, but it increased to the level of 300 MN m-2 in the Wm/ range between 0.4 and 1.2 Rm. The strength decreased rapidly again after the growth of intermetallic compound layer thicker than 1.2 Rm.
TL;DR: In this paper, the effect of insert metal, rolling conditions and oxidation of clad surface on the bonding strength and the microstructure of bonded zone were investigated, and the following results were obtained: the titanium clad steel inserted with ultra-low carbon steel, exhibits satisfactory bonding strengths, ductilities and weldabilities.
Abstract: Synopsis: In order to produce a titanium clad steel plate by hot rolling process, the effect of insert metal, rolling conditions and oxidation of clad surface on the bonding strength and the microstructure of bonded zone were investigated. The following results were obtained. (1) The titanium clad steel inserted with ultra-low carbon steel, exhibits satisfactory bonding strengths, ductilities and weldabilities. ( 2) The bonding strength is dominated by the thickness of Fe-Ti intermetallic compound produced at bonding interface and the degree of interdiffusion between Fe and Ti. High bonding strengths with very small scatter band can be obtained in the thickness range of Fe-Ti compound of 4.2 to 0.3 μm. (3) A lower bonding strength due to the oxidation on the surface to be bonded is not caused by the oxidized layer but mainly by the remarkable growth of intermetallic compound and, secondarily, by the formation of voids between Ti and steel.
TL;DR: In this paper, a superplastic elongation of fine-grained ceramics can be observed when some mechanical and microstructural requirements are satisfied at appropriate test conditions, temperature and strain rate.
Abstract: Superplastic elongation of fine-grained ceramics can be observed when some mechanical and microstructural requirements are satisfied at appropriate test conditions, temperature and strain rate. The phenomenon can be utilized in superplastic forming, solid-state bonding, sinter-forging, hot press, and hot-isostatic pressing. Recent advances in ceramic processing brought about superplastic ZrO2 composites, covalent polycrystals, bioceramics, and nanocrystalline materials. Numerous works on superplasticity of ZrO2 ceramics revealed some characteristics, microstructural features, and possible mechanisms. Attempts to achieve high-strain rate superplasticity were performed by modifying the nature of the grain boundary.
TL;DR: In this article, the formation process of burden distribution at blast furnace top was dynamically and quantitatively investigated by the use of a mathematical model, based on the equations of motion on distinct particles and the constitutive equation described by a Voigt-Kelvin rheological model with a slider.
Abstract: The formation process of burden distribution at blast furnace top was dynamically and quantitatively investigated by the use of a mathematical model, based on the equations of motion on distinct particles and the constitutive equation described by a Voigt-Kelvin rheological model with a slider. In order to increase the estimation accuracy of the mathematical model, the dashpot factor, which represents the kinetic energy dissipation of particles in the formation process of burden distribution, was experimentally determined.The following findings were obtained through the application of the mathematical model.The slope angle has significant influence on the burden deposit behavior throughout the charging. An increase of the amount of charge relates to an increase in charging rate, which results in a decrease of the deposit angle. The size segregation phenomenon on the slope can be quantitatively evaluated by the mathematical model. The change of the charging conditions of small particles onto the slope results in a change of the small particle distribution on the slope as well as a change of the deposit profile. A decrease of charging rate caused by an increase of charging time reduces the thickness of the flowing layer o f particles, resulting in the enhancement of percolation of small particles on the slope.
TL;DR: In this paper, the effect of residual stress on fatigue strength of a medium carbon steel was investigated, and a method to estimate fatigue limit from the total stress which is the sum of the residual stress and applied stress was proposed.
Abstract: Synopsis : The effect of residual stress on fatigue strength of a medium carbon steel was investigated. Specimens were induction hardened and subsequently reheated in three conditions to give them various distributions of residual stress. Fatige limit was improved by reheating in a condition compared with as induction hardened. Residual stress after the heat-treatments was compressive around the surface of the specimens, and varied to tensile stress in the inner unhardened region. A method to estimate fatigue limit from the total stress which is the sum of the residual stress and applied stress was proposed.
TL;DR: In this paper, the bulging behavior of the solidified shell in continuously cast slabs has been numerically analyzed using the elasto-plastic and creep Finite Element Method.
Abstract: The bulging behavior of the solidified shell in continuously cast slabs have been numerically analyzed using the elasto-plastic and creep Finite Element Method. Three-dimensional model has been applied in order to investigate the effect of the narrow face shell on restraining the bulging deflection. Three-dimensional shell profile and temperature distribution in it have been determined using the segregation considered solidification analysis method. In this way, strains occurring at the solidification front near the narrow face of the slab, as well as those occurring in the broad face have been computed. The computed bulging deflection have been in good agreement with measurements, and the relationship between the strain caused by the bulging and the internal cracks have been investigated. In addition, the effect of the slab width on the bulging are discussed.