Showing papers in "Isij International in 1992"
TL;DR: In this paper, a mathematical model was developed that predicts the final mechanical properties of hot-rolled steels, consisting of submodels for static and metadynamic recrystallisation, grain growth and the transformed ferrite grain size.
Abstract: A mathematical model has been developed that predict the final mechanical properties of hot rolled steels. It consists of submodels for static and metadynamic recrystallisation, grain growth and the transformed ferrite grain size. Each submodel was characterised for a wide range of C-Mn and HSLA steels. The total microstructure model has been integrated into process models and evaluated using production data for plate, structural, bar and strip rolling. Results to date indicate that the accuracy of the model is excellent and is suitable for the evaluation of new steel grades and the development of optimised thermomechanical processing routes.
358 citations
TL;DR: In this article, the effects of silicon and manganese contents on volume fraction and stability of retained Austenite particles in TRIP-aided dual-phase steels were investigated.
Abstract: The effects of silicon and manganese contents on volume fraction and stability of retained austenite particles in 0.2C-(1.0-2.5)Si-(1.0-2.5)Mn (mass%) TRIP-aided dual-phase steels were investigated. In addition, the relationships between above retained austenite parameters and ductility at room and moderate temperatures were discussed through studies on strain-induced transformation behavior of retained austenite.As increasing the silicon and manganese contents except for 2.5 mass% manganese steel, the initial volume fraction of retained austenite increased with accompanied by reducing carbon concentration in retained austenite. It was found that the ductilities of these steels became maximum at a given temperature between 23 and 175°C, i.e., a peak temperature. The peak temperature was concluded to agree well with the temperature at which the strain-induced transformation of retained austenite was suppressed moderately for each steel. Moreover, the peak temperature Tp (°C) was related to estimated martensite-start temperature Ms (°C) of the retained austenite as Tp=3.04Ms+187. Strength-ductility balance, i.e., the product of tensile strength and total elongation, at the peak temperature linearly increased with an increase in the initial volume fraction of retained austenite.
332 citations
TL;DR: The Sheffield Leicester Integrated Model for Microstructural Evolution in Rolling (SLIMMER) as discussed by the authors was developed for hot rolling of flat products and used to calculate rolling loads and torques with an accurate prediction of mean flow stress.
Abstract: By collaborative work the Sheffield Leicester Integrated Model for Microstructural Evolution in Rolling (SLIMMER) has been developed for hot rolling of flat products. The background physical metallurgy is presented together with the expressions used to describe microstructure evolution for a range of ferrous and non-ferrous metals. The finite difference thermal model at the heart of SLIMMER computes heat loss to air, descalers, rolls and water cooling while allowing for oxidation and deformation heating. The use of temperature compensated time enables isothermally determined equations for microstructure evolution to be applied to practical non-isothermal conditions. Rolling loads and torques are calculated using Sims theory with an accurate prediction of mean flow stress. Examples of rolling niobium microalloyed steel plate and the effect of initial grain size illustrate the capabilities of SLIMMER and show some of the validation of the predictions.
281 citations
TL;DR: A set of integrated mathematical models for simulating hot rolling and controlled cooling of wire rods and bars has been developed through extensive laboratory research work and validation against carefully monitored results from industrial mills.
Abstract: A set of integrated mathematical models for simulating hot rolling and controlled cooling of wire rods and bars has been developed through extensive laboratory research work and validation against carefully monitored results from industrial mills.Experimental tests have been carried out on C-Mn and eutectoid steels selected as representative of the various applications of wire rods and bars.Static and dynamic recrystallization of austenite, fraction of transformed austenite, final microstructures and mechanical properties are all calculated by modelling physical phenomena and using quantitative relationships between the microstructural and kinetic parameters and the process variables, i.e. strain, strain rate, temperature and time.The models have been applied to predict the microstructure evolution during hot rolling and to investigate the effect of working conditions and recrystallization mechanisms on the formation of heterogeneous austenitic microstructures.The effects of the cooling pattern on the temperature profile and the austenite phase transformation have also been studied to prevent: coarse pearlite and martensite formation at the centre of wire rods which have cores enriched in C and Mn; surface hardening of bars when water tube cooling systems are used to control the temperature at the cooling beds.The models provide an important insight into the process that is beneficial to enhance the quality of long products.
129 citations
TL;DR: In this paper, a mathematical model for calculating phase transformations in steels during rapid heating and cooling is presented, based on a rule of additivity, which is modelled by Johnson-Mehl-Avrami law.
Abstract: A mathematical model for calculating phase transformations in steels during rapid heating and cooling is presented. It is based on a rule of additivity. The isothermal kinetics are modelled by Johnson-Mehl-Avrami law. The model describes the kinetics of austenitization during heating, the state of austenite at the end of heating (carbon content, grain size), the kinetics of transformations during cooling, the final microstructure and hardness. The model is worked out firstly on dilatometric specimens without thermal gradients in order to validate the modelling and the input data. Then the application of the model to massive cylinders heated up and cooled down with high thermal gradients is presented.
122 citations
TL;DR: In this paper, the behavior of various impurities such as carbon, phosphorus, boron, calcium, aluminum, iron and titanium in metallurgical-grade silicon has been investigated during electron beam button melting with various modifications.
Abstract: Behavior of various impurities such as carbon, phosphorus, boron, calcium, aluminum, iron and titanium in metallurgical-grade silicon has been investigated during electron beam button melting with various modifications. Carbon, phosphorus, calcium and aluminum were removed by Electron Beam Remelting (EBR) treatment under 10–2 Pa for 30 min. Ninety percent of carbon, 75% of aluminum, 89% of calcium and 93% of phosphorus was removed. The lowest content of these impurities were 15 ppmw C, 470 ppmw Al, 150 ppmw Ca and 3 ppmw P, respectively. First order rate equation was used for the removal of carbon, calcium and aluminum, and second order equation fit for the dephosphorization. Rate constants for calcium, aluminum and carbon ranged from 0.01 to 0.1 min–1. That of phosphorus was from 0.003 to 0.01 ppmw–1·min–1.
102 citations
TL;DR: In this article, the mathematical models for predicting microstructural evolution and mechanical properties of hot strips have been reviewed, and the fundamental idea of their modelling is introduced, as well as the future work and prospective of the mathematical model in hot strip rolling.
Abstract: Mathematical models for predicting microstructural evolution and mechanical properties of hot strips have been reviewed. The metallurgical features of the hot strip rolling are discussed and the fundamental idea of their modelling is introduced.As applications of the mathematical models, the on-line prediction of the microstructure and strength, the resistance to hot deformation and the cooling curves affected by the heat evolution due to transformation are given.Finally, the future work and prospective of the mathematical model in hot strip rolling is also presented.
96 citations
TL;DR: In this paper, Li et al. measured the thermal conductivities of pure hematite, magnetite, and wustite using the laser flash method as reference value and summarized them in the form of an empirical equation k = 1/(AT+B).
Abstract: Thermal conductivities of dense pure hematite, magnetite and wustite measured using the laser flash method as reference value have been summarized in the form of an empirical equation k=1/(AT+B). Wustite shows an almost constant and the relatively low thermal conductivity due to the lattice imperfection. Thermal resistivities, 1/k, of three iron oxides appear to change linearly as a function of temperature up to the Tammann temperature.Effective thermal conductivities of fired, nonfired pellets and sinter, reduced into magnetite, wustite and metallic iron by CO-CO2 or H2 gas, have also been systematically measured in the temperature range from room temperature to 1273 K. The porosity of samples was found to change from 20 to 62% by the reduction from hematite to metallic iron. Measured effective thermal conductivity values of these iron ore agglomerates are remarkably smaller than those of dense materials due to the existence of pore. Effective thermal conductivities of metallic iron and hematite strongly depend on temperature. There is no significant difference in the effective thermal conductivities of reduced samples at the same reduction degree.The measured effective thermal conductivity values have been well-explained by the modified unit cell model originally proposed by Luikov when considering the structure composed of core part and connecting part in the solid phase. This model also clearly identify the distinction of solid structure in samples originated from the difference in preparation and reduction degree.
94 citations
TL;DR: In this paper, the effects of work-hardening of austenite on the nucleation and growth rates of various phases are discussed and a mathematical model of transformation kinetics from workhardened Austenite is also presented.
Abstract: To make quantitative prediction of microstructure in HSLA steels produced by isothermal or continuous cooling transformation, transformation kinetics of various phases were modeled thermodynamically. Five kinds of phases, i.e. polygonal ferrite, Widmanstatten ferrite, pearlite, bainite and martensite, and 10 alloying elements were taken into account. A program was developed on the basis of this model. Out line of the involved transformation kinetics are presented in this paper. The effects of work-hardening of austenite on the nucleation and growth rates of various phases are discussed and a mathematical model of transformation kinetics from work-hardened austenite is also presented.
92 citations
TL;DR: In this paper, a mathematical model for the prediction of the microstructural evolution and the mechanical properties of the steel plates produced by TMCP enables this integrated control, which consists of four modules such as heating, rolling, cooling, and mechanical properties in which the metallurgical phenomena occurring at each step are calculated.
Abstract: For manufacturing the steel plates with good mechanical properties by Thermo-Mechanical Control Process (TMCP), the manufacturing conditions are necessary to be controlled in an integrated manner through the reheating step to the accelerated cooling step. The present mathematical model for the prediction of the microstructural evolution and the mechanical properties of the steel plates produced by TMCP enables this integrated control. The present report describes the flow and the each equation of the model and the comparison between the calculated results with this model and the data obtained by the rolling experiments.The model consists of four modules such as Reheating, Rolling, Cooling and Mechanical Properties in which the metallurgical phenomena occurring at each step are calculated. The characteristic of the model is shown as follows:(1) The effect of work hardening of austenite by rolling in non recrystallization temperature region is represented as the effect of average dislocation density (ρ) accumulated in austenite grains. The nucleation rate of intragranular ferrite and that of grain boundary ferrite are distinctively formulated as functions of ρ.(2) The effects of microalloying elements are considered in the formulation of metallurgical phenomena and mechanical properties such as pinning and solute drag effects on the grain growth of austenite at the reheating step, the restraining effect on recovery and recrystallization of work-hardened austenite at the rolling step, the restraining effect of solute elements on the progress of transformation at the cooling step, and the solution hardening and the precipitation hardening for the mechanical properties of the plates.
91 citations
TL;DR: The sessile drop profile method was combined with X-ray radiography to develop a precise method to measure interfacial tension and contact angles of liquid metals at high temperatures and in a variety of atmospheres as discussed by the authors.
Abstract: The sessile drop profile method was combined with X-ray radiography to develop a precise method to measure interfacial tensions and contact angles of liquid metals at high temperatures and in a variety of atmospheres. An accurate method of digital image processing was developed to capture, enhance and determine the coordinates of the X-ray shadow image of the droplet. Laplace's equation was then solved numerically to allow a non-subjective determination of interfacial tension and contact angles.Examples of the determination of the interfacial tension of mercury in argon, of liquid iron at 1 550°C under various CO/CO2 gas mixtures, of iron carbon alloys and of liquid iron in contact with a lime-alumina-silica slag at 1 550°C, are given.
TL;DR: In this article, the effects of retained austenite on press formability were investigated, using austempered 04C-Si-12Mn sheet steels with high tensile strength of more than 980 MPa.
Abstract: Effects of retained austenite on press formability were investigated, using austempered 04C-Si-12Mn sheet steels with high tensile strength of more than 980 MPaThe results showed plausible relationships between formability and initial volume fraction of retained austenite (Vγ0) With an increase in Vγ0, height of stretch forming increased linearly to its maximum at about 02Vγ0, and bending as well as expanding of a mechanically ground hole were gradually improved to the best at 015 to 02Vγ0 On the other hand, expanding of a punched hole was slightly deteriorated with increasing Vγ0 in less than 015-02Vγ0 These various types of formability were all extraordinarily deteriorated beyond 02Vγ0 in stretch forming and 015-02Vγ0 in the othersIt was concluded that these effects of retained austenite on formability can be clearly understood in terms of Vγ0 and k: a rate constant relating rate of deformation-induced transformation with uniaxial tensile strain, as a parameter showing stability of retained austenite in press forming
TL;DR: In this paper, a new type compound roll which is composed of high-carbon high speed steel of outer shell and forged steel of core material to meet the requirement of high reliability as well as high wear resistance was developed.
Abstract: In the field of hot strip mill finishing train, the demands for not only high quality of sheet product shape and sheet surface condition but also high productivity and energy saving in rolling are increasing. In this circumstance, we have developed completely new type compound roll which is composed of high-carbon high speed steel of outer shell and forged steel of core material to meet the requirement of high reliability as well as high wear resistance.After many experiments, the first trial of this new compound high-carbon high speed steel rolls was made in 1987 in finishing train of hot strip mill. Since then more than one hundred fifty new compound rolls have been used in hot strip mill finishing train. These new compound rolls are contributing the high productivity of rolling and the improvement of sheet products.
TL;DR: In this paper, the development of a software package DICTRA for simulation of diffusional reactions in multicomponent alloys and a databank for multi-component diffusivities is described.
Abstract: The development of a software package DICTRA for simulation of diffusional reactions in multicomponent alloys and a databank for multicomponent diffusivities is described. Applications concerning heat treatment of low-alloy steels and martensitic stainless steels are discussed.
TL;DR: In this paper, a ceramic loop filter has been developed for the reduction of non-metallic inclusions in steel, which can be adjusted widely by varying the string and loop diameters respectively.
Abstract: For the reduction of non-metallic inclusions in steel, a ceramic loop filter has been developed. Void size of the filter can be adjusted widely by varying the string and loop diameters respectively. Characteristics of the loop filter, such as an inclusion removal efficiency and filter medium resistance were investigated in laboratory. From the experimental results, the mechanism of the filtration was discussed, and it was concluded that firstly the inclusion particle is entrapped onto the filter surface by the interception, secondly glued there by the attraction force based on the molten steel surface tention, and finally bonded by sintering.
TL;DR: In this article, a review correlates the mechanism proposed so far to explain the abnormal electrodeposition behavior of iron-group metal alloys and shows that the mechanism is not the only one that can explain the anomalous behavior of binary alloys.
Abstract: Almost 300 kinds of binary alloys have been electroplated so far modify surface properties of substrates. Electrodeposition of iron-group metal alloys has been studied most intensively for last 16 years. This trend was caused not only by the excellent properties of the coatings that were useful for many industrial applications but also by the fact that their electrodeposition behavior was interesting from an academic point of view. This review correlates the mechanism proposed so far to explain the abnormal electrodeposition behavior of iron-group metal alloys.
TL;DR: In this paper, the anisotropy of the grain boundary energy is incorporated into the model and the suppression of grain growth is observed and the grain size and the edge number distributions become broad.
Abstract: The temporal evolution and morphology of two-dimensional grain growth are simulated by Monte Carlo simulation techniques. In the simulation, the anisotropy of the grain boundary energy is incorporated into the model. Compared with the case in which no anisotropy of boundary energy is assumed, the suppression of grain growth is observed and the grain size and the edge number distributions become broad. The occurrence of the wetting phenomena is considered to be responsible for the broadness of the grain size distribution in the structure simulated by a model in which anisotropy of boundary energy is incorporated. The pinning effect of precipitates on growth kinetics is also studied by the model. The size of pinned grain is found to varied with inverse square root of the particle volume fraction. The size distribution of pinned grain structure is narrower than that of the pinning-free grain structure with the same anisotropy of grain boundary energy. The average size of n-sided grain is proportional to the grain edge number, n. The effect of the anisotropy of grain boundary energy on the n-dependence of the average grain size is not evident. The nearest neighbor sides correlation like Aboav-Weaire relation is observed in both grain structures computed by Potts model and modified Potts model. The conversion of Monte Carlo step to real time is attempted based on diffusion controlled mechanisms. The estimated grain size with use of the conversion formula in pure iron at 1273 K is in good agreement with that evaluated by the empirical formula derived on the basis of experimental result.
TL;DR: In this article, experimental studies on the bubble behavior in submerged gas blowing were carried out with liquid Wood's metal, and the results showed that the radial distribution of gas fraction and bubble frequency can be described by a Gaussian function and the bubble size distribution obeys a log-normal function.
Abstract: Experimental studies on the bubble behaviour in submerged gas blowing were carried out with liquid Wood's metal. About 440 kg of Wood's metal at 100°C was contained in a ladle-shaped glass vessel with an inner diameter of 40 cm. The liquid metal was stirred by nitrogen, argon or helium respectively through a nozzle positioned centrically or eccentrically at the bottom. The bubble plumes were investigated under different gas flow rates and nozzle diameters by determination of local gas fraction, bubble frequency, size distribution and rising velocity of bubbles.The measurements show that the radial distribution of gas fraction and bubble frequency can be described by a Gaussian function and the bubble size distribution obeys a log-normal function. Except for the region near the nozzle the mean rising velocity of bubbles is nearly constant over the radius. The influence of blowing conditions on these variables was estimated.
TL;DR: In this article, an approach to predict mechanical properties of hot-rolled multi-phase steels referring to the stress-strain curves is proposed, which is based on regression analysis about the relationships between properties and chemical compositions and processing factors.
Abstract: An approach to predict mechanical properties of hot-rolled multi-phase steels referring to the stress-strain curves is proposed. Different from a conventional approach of regression analysis about the relationships between properties and chemical compositions and processing factors, a proposed one is based on the analysis and application of stress-strain curve: several commonly used mechanical properties such as yield strength, tensile strength, uniform elongation, total elongation, work-hardening exponent (n) and Vickers hardness, are derived systematically from the stress-strain curve of a multi-phase steel, which is calculated by using concentration factor, i.e., strain partition ratio and stress-strain curves of constituent phases. Stress-strain curves of individual component structures such as ferrite, pearlite, bainite, and martensite are expressed by Swift's equation. Physical background of the concentration factor is discussed by examining theoretical models of deformation for two-phase materials. Evaluation of plastic relaxation related to microstructural topology might be the most difficult point of this approach and some trials are presented.
TL;DR: In this paper, the authors reviewed the phenomena by which wetting and the Marangoni effect participate or may participate in iron and steelmaking processes, and the concept of wetting conventionally defined for the system of gas-liquid-solid was applied to the systems of liquid 1-liquid 2-solid, liquid-solid 1-solid 2 and gas liquid 1 liquid 2.
Abstract: This article reviews the phenomena by which wetting and the Marangoni effect participate or may participate in iron and steelmaking processes. The concept of wetting conventionally defined for the system of gas-liquid-solid was applied to the systems of liquid 1-liquid 2-solid, liquid-solid 1-solid 2 and gas-liquid 1-liquid 2. In these systems, local corrosions of refractories at the interfaces of gas-slag and metal-slag, slag foaming, bubble dispersion into metal phase, and interaction of inclusions with solidification fronts were described in relation to the wetting and the Marangoni effect. Rates of reactions of gas-metal, and metal-slag were briefly introduced as examples of possible participation of the Marangoni effect.
TL;DR: In this paper, a computer model which predicts complex precipitation behavior quantitatively in Nb-Ti bearing steel has been developed on a theoretical basis, and both the acceleration of precipitation rate and the refinement of precipitates particles due to hot deformation are also quantitatively explained.
Abstract: A computer model which predicts complex precipitation behavior quantitatively in Nb-Ti bearing steel has been developed on a theoretical basis. The solubility and composition of the complex precipitates, and the chemical driving force of the precipitates from supersaturated austenite are estimated by means of thermodynamic analysis of regular solution composed of four-binary compounds. The change in dislocation density which acts as a nucleation site during hot working is calculated by using dislocation theory. And the time dependence of volume fraction and the particle radius of strain induced precipitation are also predicted on the basis of classical nulceation theory. In order to estimate the effect of deformation on nucleation, the change in elastic energy of dislocation with nucleation is calculated.Experimental results showed that combination of Nb and Ti addition, decreased the solubility of carbonitrides and accelerated the precipitation rate from supersaturated austenite because of the formation of complex precipitates. Such experimental results are in good agreement with the prediction by the present model. And both the acceleration of precipitation rate and the refinement of precipitates particles due to hot deformation are also quantitatively explained.
TL;DR: In this article, the removal of boron from metallurgical-grade silicon was investigated by applying an Ar/H2O plasma treatment to develop a new production technique for low-cost solar grade silicon.
Abstract: The removal of boron from metallurgical-grade silicon was investigated by applying an Ar/H2O plasma treatment to develop a new production technique for low cost solar-grade silicon (SOG-Si).The concentration of boron in MG-Si decreased from 35.7 to 0.4 ppmw, satisfying the requirement for SOG-Si, using Ar+1.24vol%H2O plasma gas for 25 min of melting time. It has been demonstrated that the overall rate of elimination of boron is controlled by the diffusion of boron in silicon melts. The removal of boron is affected by the kind of plasma operating gas with the highest elimination rate of boron by Ar/H2O plasma. The experimental findings support that boron in silicon reacts with oxygen in gas only at the plasma-impinging area.It may be said that only this technique has the possibility to lower boron content of silicon down to the required 0.1 ppm for SOG.
TL;DR: In this article, the surface tension of liquid iron alloys and liquid slags, contact angle between solid and liquid phases, and interfacial tension between liquid and liquid phase, are summarized on the basis of currently published articles.
Abstract: Interfacial properties and adsorption behavior play an important role in the progress of heterogeneous reactions, so accurate values of these properties are required as the basic knowldge to examine the interfacial phenomena in iron- and steel-making processes. In this review, data for surface tension of liquid iron alloys and liquid slags, contact angle between solid and liquid phases, and interfacial tension between liquid and liquid phases, are briefly summarized on the basis of currently published articles.
TL;DR: In this paper, the effect of principal rolling variables on the degree of microstructural refinement during processing of Ti-V-(Nb) steels via recrystallization controlled rolling is investigated.
Abstract: The static recrystallization characteristics (grain size, kinetics) have been established for Ti-V-(Nb) austenites and used as the basis for a theoretical evaluation of microstructural evolution during hot rolling of plate. In this context, particular attention has been focussed on so-called recrystallization controlled rolling, whereby a fine as-rolled ferrite garin size is obtained via transformation from an austenite which has been substantially grain refined via static recrystallization. The model is shown to forecast a behaviour which is in acceptable accord with practical plate-rolling experience. Furthermore, the rolling model has been used in a systematic theoretical investigation of the effect of principal rolling variables on the degree of microstructural refinement during processing of Ti-V-(Nb) steels via recrystallization controlled rolling.
TL;DR: In this article, an experimental model was constructed to clarify the mechanism for separating inclusions from molten steel strongly stirred with a rotating electro-magnetic field, where the ingot obtained had its maximum oxygen content at the axis of rotation, which was partly explained by the centripetal force acting on inclusions during rotation of the mnolten steel.
Abstract: An experimental model was constructed to clarify the mechanism for separating inclusions from molten steel strongly stirred with a rotating electro-magnetic field.Molten steel was rotated and solidified in a crucible. The ingot obtained had its maximum oxygen content at the axis of rotation. The existence of this maximum area can be partly explained by the centripetal force acting on inclusions during rotation of the mnolten steel.Many coagulating inclusion pairs were observed in the ingot, with the radii of the inclusions forming coagulating pairs being concentrated in the range from 10 to 50 μm. This phenomenon was explained using Saffman's model, which shows the probability of gradient collision between inclusions in turbulent eddies. This inclusion coagulation effect suggests the high deoxidation capability of rotating molten steel in an electro-magnetically stirred ladle.
TL;DR: In this paper, the entrainment phenomena occurring at liquid/liquid interfaces during passage of single bubbles have been investigated using the systems water/cyclohexane, mercury/water, and mercury/silicon oil.
Abstract: The entrainment phenomena occurring at liquid/liquid interfaces during passage of single bubbles have been investigated using the systems water/cyclohexane, mercury/water, and mercury/silicon oil. Measurements were performed on the increase of the continuous interfacial area, the residence time of the bubble at the interface, the length of the liquid jet of the lower phase drawn upwards, the number and size of droplets of the lower phase in the upper phase, the residence time of the droplets and their velocity of fall. Dimensionless correlations were derived for some of these quantities, and some consideration is given of the application of the data in mass transfer models.
TL;DR: In this article, the authors present recent developments and future trends in high Cr ferritic heat resistant steels, such as TR1100, TR1200, TB9 and TB12.
Abstract: The article presents recent developments and future trends in high Cr ferritic heat resistant steels. Research programs are underway worldwide to improve the performance of 8 to 13% Cr ferritic steels for high temperature applications of up to 650°C. We developed the super 12% Cr heat resistant steel called TAF steel in 1956. The creep rupture strength of TAF steel is two or three times higher than those of H46 and AISI422 at 600 and 650°C. Our research in this area was well ahead of work being conducted in other countries.Recently the author succeeded in developing TR1100, TR1200, TB9 and TB12 with excellent high temperature properties and room temperature toughness through the improvement of TAF steel. In the near future, these new steels will be applied to turbine rotors, blades, and boiler tubes for advanced supercritical power plants, to fuel cladding, wrapper and steam generator tubing for fast breeder reactors, and to first wall materials for conceptual fusion reactors. These steels are a key to making these plants and reactors practical.
TL;DR: In this paper, the effect of adding a titanomagnetite to two sintering ore blends, containing 10 and 20% pisolitic limonite respectively, was investigated.
Abstract: Titanium containing compounds are valuable materials for addition to the blast furnace to extend operational compaigns. However, the addition of these materials via the sinter plant has been known to create problems. This study investigates the effect of adding a titanomagnetite to two sintering ore blends, containing 10 and 20% pisolitic limonite respectively. The addition of up to 2% titanomagnetite did not affect the sintering parameters or sinter quality. Increasing the titanomagnetite levels to greater than 3% also had no significant influence on sintering but a signficant deterioration in sinter RDI was recorded. Results also showed that the deterioration in RDI was greater for the blend containing more pisolitic limonite.SEM studies carried out on the product sinters found most of the titanium in the glass phase. The mechanical properties of the glass was characterised using indentation fracture mechanics. Although some difficult was experienced, due to the small and disperse nature of the glass, addition studies using artifically manufactured glass indicated that the fracture toughness of the glass decreased with increasing titanium levels. It is postulated that because glass in the weakest phase in sinter and is widely dispersed any reduction in its fracture toughness will increase the vulnerability of the sinter to crack propagation, thereby increasing sinter RDI. It is also postulated that increasing the pisolitic level increased melt formation and the dispersion of the glass phase, resulting in a further deterioration in sinter RDI.