Alumina Inclusions Research Articles

Characterization of the Three-Dimensional Morphology and Formation Mechanism of Inclusions in Linepipe Steels

The characterization of the three-dimensional (3D) morphology and modification of inclusions in linepipe steel plates were investigated in the present work. The deoxidation products, Al2O3 inclusions, were modified into deformable calcium aluminate inclusions by calcium treatment in order to efficiently prevent nozzle clogging. The effect of sulfur content on the morphological characteristics and chemical composition of inclusions by calcium treatment were analyzed by extracting inclusions from steel matrix using non-aqueous electrolyte and automatic scanning electron microscopy connects with energy-dispersive spectrometer. The evaluation of the effect of calcium treatment was proposed using the 3D morphology of inclusions. Meanwhile, the modification and control of inclusions in the linepipe steel were studied by thermodynamic calculation on calcium treatment with the strategy of reducing the size of inclusions before calcium treatment, and controlling the contents of [Al], [Ca], and total oxygen in a reasonable narrow range during calcium treatment. The modification and transformation process of alumina inclusions was revealed as Al2O3 → MgO-Al2O3 → CaO-MgO-Al2O3-CaS (after calcium treatment) → CaO-Al2O3-CaS. A kind of high-melting MgO-Al2O3 core was wrapped by the low-melting component of CaO-Al2O3 indicating an incomplete reduction of MgO and Al2O3 by calcium.

Effect of surfactant Te on the behavior of alumina inclusions at advancing solid-liquid interfaces of liquid steel

The effect of surfactant Te on the behavior of alumina inclusions at advancing solid-liquid interfaces of liquid steel was studied by adding Te to liquid steel before Al deoxidation at 1873 K. After water-quenching, the spatial distribution homogeneity of alumina inclusions in the steel matrix was characterized using the Dirichlet tessellation method. The deterioration of this homogeneity with increasing the addition of Te indicates that Te facilitates pushing of alumina inclusions. This phenomenon was discussed based on the thermodynamics of an asymmetric thin liquid film confined by an advancing solid-liquid interface and a particle. The surface excesses of Te at the solid-liquid and particle-liquid interfaces were theoretically demonstrated to decrease when an alumina inclusion moves towards the solid-liquid interface, thereby weakening the effect of Te on the solid-liquid and particle-liquid interfacial energies. Based on this, effect of surfactants was incorporated in the models predicting the critical velocity VC.

Effect of Refractory on Nonmetallic Inclusions in Al-Killed Steel

To understand the effect of refractory on the evolution of inclusions in the secondary steelmaking, steel samples were taken at different stages of the process train. Laboratory experiments were carried out using different refractories (alumina, spinel, and MgO). In the laboratory study, the types of inclusions considered were alumina, spinel, and calcium aluminate. The focus was given to Al-killed steel. The results showed that alumina refractory and spinel refractory had little effect on all the three types of inclusions, while the effect of MgO refractory depended on the activity of dissolved oxygen in liquid steel. With lower oxygen activity, alumina inclusions could transform into spinel inclusions. No evident change could be found for spinel and calcium aluminate inclusions. When the oxygen activity was high enough, spinel inclusions could not be generated from alumina inclusions. The laboratory results helped in understanding the evolution of the inclusions in the industrial process.

Mathematical Modeling on the Growth and Removal of Non-metallic Inclusions in the Molten Steel in a Two-Strand Continuous Casting Tundish

In the current study, mathematical models were developed to predict the transient concentration and size distribution of inclusions in a two-strand continuous casting tundish. The collision and growth of inclusions were considered. The contribution of turbulent collision and Stokes collision was evaluated. The removal of inclusions from the top surface was modeled by considering the properties of inclusions and the molten steel, such as the wettability, density, size, and interfacial tension. The effect of composition of inclusions on the collision of inclusions was included through the Hamaker constant. Meanwhile, the effect of the turbulent fluctuation velocity on the removal of inclusions at the top surface was also studied. Inclusions in steel samples were detected using automatic SEM Scanning so that the amount, morphology, size, and composition of inclusions were achieved. In the simulation, the size distribution of inclusions at the end steel refining was used as the initial size distribution of inclusions at tundish inlet. The equilibrium time when the collision and coalescence of inclusions reached the steady state was equal to 3.9 times of the mean residence time. When Stokes collision, turbulent collision, and removal by floating were included, the removal fraction of inclusions was 16.4 pct. Finally, the removal of solid and liquid inclusions, such as Al2O3, SiO2, and 12CaO·7Al2O3, at the interface between the molten steel and slag was studied. Compared with 12CaO·7Al2O3 inclusions, the silica and alumina inclusions were much easier to be removed from the molten steel and their removal fractions were 36.5 and 39.2 pct, respectively.

Analysis of heat-release during TNT/Aluminum afterburning by means of numerical simulations

The present study investigates the afterburning from an explosion of a spherical 2,4,6-Tri-Nitro-Toluene (TNT) charge containing aluminum particles at four different Heights of Burst (HoB), to demonstrate that numerical simulations can facilitate the evaluation of the performance of Enhanced Blast eXplosives (EBX). The simulations are conducted using a two-phase Large Eddy Simulation model in Euler-Lagrange form, incorporating interaction between gaseous and solid phases by means of a two-way coupling. Finite rate Arrhenius chemistry is used to simulate the afterburning process, thereby enabling the examination of the separate heat-release contributions from carbon and aluminum afterburning reactions. The simulation results indicate the heat-release contribution from the aluminum reactions is significantly higher than from the carbon reactions, also does the heat-release from aluminum reactions, for all HoBs, fluctuate more in time compared to the heat-release from the carbon reaction. Most of the heat-release from carbon seems to occur at early times, after which the afterburning of carbon stagnates at a steady rate. The heat-release from aluminum reactions is more intermittent and is thought to be closely connected to the physical environment inside the mixing layer. Hence, the simulation results show that aluminum afterburning in EBX charges is strongly dependent on the mixing intensity, which is established by instabilities through shock-mixing layer interaction. Mixing intensity in its turn varies with HoB, as the shock propagation pattern is different for all HoB, indicating that in order to achieve maximum effect from aluminum inclusion to an explosive, HoB must be considered as a parameter.

Electrochemical Aspects of the ESR Process

Current passage in the ESR process is accomplished by at least two Faradaic reaction systems, one at the electrode/slag interface and another at the slag/ingot interface. The nature of these reactions has been investigated and is reported to be a function of the alloy composition, current density and slag composition. In this report, data generated from both DC and line- frequency AC ESR operations is used to relate laboratory investigations on these reactions to results obtained in industrial practice. The operating reaction in the line frequency AC melting of simple alloy steels is found to be principally the reversible anodic oxidation of iron (Fe/Fe2+). In the equivalent DC process there is in addition the cathodic deposition of aluminium, resulting in the formation of substantial amounts of D-type alumina inclusions in the ingot. The Faradaic reactions involve energy exchange which should be taken into account in the process energy balance. They also are likely to change the interface physical characteristics such as interfacial tension. The data is extended to the case of low frequency ESR furnaces in which it is found that the extent of the reactions is strongly dependent on current density. It is concluded that the presence of Faradaic reactions in low frequency furnaces is unlikely to lead to quality problems in the alloys and applications for which these processes are used. This conclusion appears to be supported by industrial practice and leads to a further conclusion that low frequency practices in large ESR furnaces could potentially be replaced by simpler DC systems.

A unified framework for producing CAI melting, Wark–Lovering rims and bowl-shaped CAIs

Calcium Aluminium Inclusions (CAIs) formed in the Solar System, some 4,567 million years ago. CAIs are almost always surrounded by Wark-Lovering Rims (WLRs), which are a sequence of thin, mono/bi-mineralic layers of refractory minerals, with a total thickness in the range of 1 to 100 microns. Recently, some CAIs have been found that have tektite-like bowl-shapes. To form such shapes, the CAI must have travelled through a rarefied gas at hypersonic speeds. We show how CAIs may have been ejected from the inner solar accretion disc via the centrifugal interaction between the solar magnetosphere and the inner disc rim. They subsequently punched through the hot, inner disc rim wall at hypersonic speeds. This re-entry heating partially or completely evaporated the CAIs. Such evaporation could have significantly increased the metal abundances of the inner disc rim. High speed movement through the inner disc produced WLRs. To match the observed thickness of WLRs required metal abundances at the inner disc wall that are of order ten times that of standard solar abundances. The CAIs cooled as they moved away from the protosun, the deduced CAI cooling rates are consistent with the CAI cooling rates obtained from experiment and observation. The speeds and gas densities required to form bowl-shaped CAIs are also consistent with the expected speeds and gas densities for larger, ~ 1 cm, CAIs punching through an inner accretion disc wall.

Characterization of the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy

Grade assessment of steel is generally performed via the metallographic method, which is timeconsuming and is not able to provide the elemental distribution information. In this paper, we present a method to measure the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy (LIBS). The measurement is performed in two basic steps: steel samples are polished using metallographic sand paper and the Al2O3 inclusion number and size distribution in a marked area are observed using scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) for further LIBS scanning analysis. The threshold intensity that distinguishes soluble aluminum and insoluble aluminum inclusions is determined using LIBS combined with the SEM/EDS statistical data. Carbon steel (the sample number is S9256) and bearing steel (the sample number is GCr15) are analyzed in scanning mode, and the number of Al2O3 inclusions in different size ranges is obtained from the statistical information derived from the Al2O3 size calibration curve. According to heavy and thin series for globular oxide inclusions grade assessment, the method we propose is comparable to the traditional metallographic method in terms of accuracy; however, the process is simplified and the measurement speed is significantly improved.

Gas/solid carbon branching ratios in surface-mediated reactions and the incorporation of carbonaceous material into planetesimals.

We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas/solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N2. This fraction varies from more than 99% for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO2, as well as a very wide range of organic molecules at very low concentration. Carbon deposits do not form continuous coatings on the catalytic surfaces, but instead form extremely high surface area per unit volume "filamentous" structures. While these structures will likely form more slowly but over much longer times in protostellar nebulae than in our experiments due to the much lower partial pressure of CO, such fluffy coatings on the surfaces of chondrules or calcium aluminum inclusions could promote grain-grain sticking during low-velocity collisions.

Formation Mechanism of CaS-Al2O3 Inclusions in Low Sulfur Al-Killed Steel After Calcium Treatment

The laboratory experiments of alumina inclusions modified by calcium treatment in Al-killed steel were carried out at 1873 K (1600 °C), and the inclusions in steel samples were characterized at 1, 5, and 10 minutes after calcium addition. The results show that the type of inclusions after calcium treatment was determined by the sulfur and T.O contents of steel. CaS-Al2O3 inclusions were obtained in steels with high sulfur and low T.O contents. The mass ratio between CaS and Al2O3 was determined by T.Ca and T.O contents of steel. The influence of holding time after calcium addition on the composition of inclusions was negligible. The thermodynamics for the formation of CaS-Al2O3 inclusions after calcium treatment was discussed, and a simple formation mechanism was proposed. Moreover, the CaO, Al2O3, and CaS contents in the inclusions were predicted through the sulfur, total calcium (T.Ca), and T.O contents, and it was found that the CaO content decreases with increasing S/T.O, while (pctCaS)/(pctAl2O3)1/3 increases with increasing T.Ca/T.O.

A Review on Prerequisites of a Set-Up for Particle Detection by Ultrasonic Waves in Aluminium Melts

In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of aluminium products and the effectiveness of the processes, a reliable and cheaper on-line detection method is needed. Ultrasonic detection has been used in steel industry, but relatively rare in aluminium industry, although it would theoretically allow for an online non-intrusive detection of the cleanliness of the melt. In this work, the current information on ultrasonic inclusion detection was gathered and recommendations were provided on the Prerequisites for a set-up for ultrasonic detection of non-metallic inclusions in aluminium as a contribution on previous works. It has been concluded that ultrasonic waves seem promising, and should be experimented more on an industrial level to have a clear view on the potentials of the method.

Transformation of LaOF into LaF3owing to Al3+in luminescent Eu3+-doped crystalline powders

Conversion of LaF3 into LaOF has been demonstrated in the literature through heat treatment of the samples. In this work, we investigated the possibility of converting LaOF into LaF3 using Al3+ in a combustion synthesis technique. The conversion was proposed by taking advantage of the affinity that aluminium has for oxygen. The morphological study via scanning electron microscopy has shown an increase in the porosity of the samples with the inclusion of aluminium. X-ray powder diffraction data analysis demonstrated complete crystallization and conversion of LaOF into LaF3 due to the presence of aluminium. A small fraction of LaAlO3 has been detected and it confirms that aluminium bonds with oxygen, as expected. The samples were also doped with the rare-earth ion europium as a luminescence probe. Stokes photoluminescence was produced using UV light (λ = 355 nm) and the spectral analysis of Eu3+ 4f–4f electronic transitions has confirmed that LaOF is converted into LaF3. The measured luminescence lifetimes of reactant and product are characteristic of Eu3+ in the compounds LaOF and LaF3.

Interaction between Alumina Inclusions in Molten Steel Due to Cavity Bridge Force

Interaction between Alumina Inclusions in Molten Steel Due to Cavity Bridge Force

Effect of non-metallic inclusions and shrinkage cavities on the dynamic fracture toughness of a high-strength G42CrMo4 cast steel

The formation and clustering of non-metallic inclusions was investigated by applying a steel casting simulator. In a fully controlled atmosphere, the oxygen content of the steel melt was intentionally increased. At a specified level, the steel was deoxidized by pure aluminum. After the treatment, the melt was cooled down in the crucible. The effects of the inclusions and the cavities were determined by means of metallography, tensile tests, dynamic fracture toughness tests, and fractography. Metallographic results show that alumina particles have a strong tendency to aggregate at the walls of the crucible. Neglecting this aggregation, a relatively homogeneous distribution of alumina inclusions was observed. Furthermore, the solidified steel exhibited manganese sulphide inclusions and shrinkage cavities. The results of the tensile tests revealed a relatively low ductility. Fractographic examinations showed that both non-metallic inclusions and shrinkage cavities promoted ductile fracture. Results of dynamic fracture toughness tests revealed a relatively large scatter in the dynamic crack resistance. This was analogously attributed to the damaging effect of the non-metallic inclusions and the shrinkage cavities. Fractographic investigations showed that not only alumina inclusions but preferentially manganese sulphide inclusions affected the failure behavior of the investigated steel.

空隙架橋力に基づく溶鋼中アルミナ介在物間の相互作用

空隙架橋力に基づく溶鋼中アルミナ介在物間の相互作用

Mathematical Analysis of the Dynamic Effects on the Deposition of Alumina Inclusions inside the Upper Tundish Nozzle

Mathematical Analysis of the Dynamic Effects on the Deposition of Alumina Inclusions inside the Upper Tundish Nozzle

The Use of Double Surface Treatments to Optimize the Fatigue Life of Components Made on Structural Steels

High intensity shot peening treatments have been combined with other different second treatments, such as low intensity shot peening, vibratory finishing and grit blasting with fine alumina powders, in order to optimize the fatigue life of a medium-alloyed, quenched and tempered, structural steel with a very high strength (2000MPa). Single low intensity shot peening treatments using ceramic balls were also used with the same objective.Roughness and residual stress profiles were measured, while the fatigue behavior was analyzed using a rotating bending fatigue equipment. Fracture surfaces were also analyzed in a scanning electron microscope (SEM) and the location of the fatigue crack initiation was detected.Although the maximum stress in our fatigue tests is always applied on the surface of the specimen, the appropriate surface treatment combinations were able to optimize the fatigue response of the steel until the point where the fatigue crack initiated in the specimen interior (subsurface nucleation), due to the microstructural stress concentration provided by small alumina inclusions present in the microstructure of the steel. The amplitude of the stress intensity factor necessary to propagate fatigue cracks in the studied steel and the intrinsic stress intensity factor threshold, ΔKth, were finally obtained.

Effect of Turning Parameters on Tool Wear, Surface Roughness and Metal Removal Rate of Alumina Reinforced Aluminum Composite

Now a day's demand of light materials is increasing continuously and MMC of aluminum playing a vital role to fulfill these demands due to their light weight, high strength and appreciable hardness etc. This study deals with the manufacturing of Aluminum based MMC of Alumina. Three samples were manufactured by sand casting with 2%, 4% and 6% of alumina by weight and mechanical properties like tensile Strength and Hardness were tested. Investigation reveals that mechanical properties enhanced in appreciable fashion as compared to pure aluminum. Turning on MMCs were carried out using uncoated carbide tool and coated tool. Turning test were performed at various speed, feed rate, depth of cut and percentage of alumina inclusion in MMCs. Furthermore tool wear, surface roughness and metal removal rate were investigated. Purpose of the study is to observe and understand the behavior of the turning parameters of composite materials under various operating conditions.

Effect of Alumina Morphology on the Clustering of Alumina Inclusions in Molten Iron

Effect of Alumina Morphology on the Clustering of Alumina Inclusions in Molten Iron

Population Evolution of Oxide Inclusions in Ti-stabilized Ultra-low Carbon Steels after Deoxidation

Population density function (PDF), which can eliminate the arbitrariness caused by the choice of the number and the size of bins compared to the well-used histograms, was introduced to analyze the amount of inclusions. The population evolution of oxide inclusions in forms of PDF in Ti-stabilized ultra-low carbon steels after deoxidation during industrial RH refining and continuous casting processes was analyzed using an automated SEM-EDS system. It was found that after deoxidation till the early stage of casting, the alumina inclusions exhibited a lognormal PDF distribution, and three factors including the existence of a large amount of alumina clusters, the generation of alumina from the reduction of Al-Ti-O inclusions and the reoxidation of molten steel were estimated as the reasons. The shape parameter σ was high after deoxidation and then decreased after Ti treatment, indicating that in a short period after deoxidation, the size of alumina inclusions was widely distributed. After Ti treatment, the distribution of inclusion size was more concentrated. The scale parameter m decreased with time during the whole refining process, indicating that the proportion of large inclusions decreased during refining. Contrarily, the Al-Ti-O inclusions presented a fractal PDF distribution except at the end of casting with fractal dimension D of 4.3, and the constant of proportionality C decreased with time during RH refining and increased during casting process. The reoxidation of steel by slag entrapped from ladle was considered as the reason for the lognormal PDF behavior of Al-Ti-O inclusions at the end of casting.