Size Distribution Of Inclusions Research Articles

Spontaneous cracking of thermally toughened safety glass Part two: Nickel sulphide inclusions identified in annealed glass

The present paper is part two of a small series of three publications on spontaneous breakages of toughened glass. In part one, we deal with the detailed effects of the crystallographic and physical properties of the nickel sulphide species contained in those inclusions; we find that solely under this aspect, only c. 40% of the breakages in a Heat Soak Test (HST) according to, e.g., EN 14179-1:2006, would be physically able to cause a breakage in a façade. The present paper partly builds up on these findings. In the present paper, we prove experimentally that nickel sulphide inclusions are found everywhere in the raw glass section. On the other hand, their repartition is visibly influenced by gravitational settling. The resulting distribution profile is explained by a physical model. Further elaboration of this model allows to better understand the observed nickel sulphide inclusion size distribution in the raw glass. We show statistically that almost only nickel sulphide inclusions with size >55~upmu hbox {m}, situated in the middle glass portion, can lead to breakage in HST, in good correlation with data previously published. We quantify the nickel sulphide inclusions’ size impact based on the statistical evaluation of our dataset. Big nickel sulphide inclusions (>450~upmu hbox {m}) always cause very high breakage risk > 90%. On the other hand, we prove experimentally that only a minority of c. 1/4 of the nickel sulphide inclusions factually existing in raw glass leads to breakages in the HST carried out in the frame of our R&D project where the glass panes were only small and thin. In the normal building glass product mix this proportion is probably higher because in the HST, the mass-related breakage rate (in numbers per ton of glass) increases with increasing glass panes’ dimensions. In Part Three we evaluate datasets from field breakages and give an overall summary of the series.

Distribution of TiN inclusions in Ti-stabilized ultra-pure ferrite stainless steel slab

In order to clarify and control the silver defect on surface of cold-rolled sheet of the Ti-stabilized ultra-pure ferrite stainless steel, the distribution of TiN inclusions on the cross section of hot-rolled plate was studied using automated scanning electron microscopy/energy-dispersive X-ray spectroscopy inclusion analysis (ASPEX 1020 system). It was found that the number density decreases sharply from the surface to the center of the hot-rolled plate, whereas the average size increases. Then, the distribution of TiN inclusions on the cross section of continuously cast slab was investigated. Similarly, numerous small-sized TiN inclusions were generated at the subsurface of the slab. The average size rapidly increased and the number density dramatically decreased from the subsurface to 1/4 thickness, while from 1/4 thickness to 1/2 thickness, the increase in average size and the decrease in number density were slight. Thermodynamics results showed that TiN inclusion was formed below the liquidus temperature, which indicated that TiN inclusions could not be formed during secondary refining. Considering the microsegregation of solute elements and the equilibrium of TiN formation during solidification, TiN precipitated in the mushy zone when the solid fraction was close to 0.2. The growth of TiN was analyzed based on the diffusion-controlled growth model. With the increase in cooling rate, the time for TiN growth decreased and the size of TiN inclusions was diminished, which revealed the size distribution of TiN inclusions in the cast slab qualitatively.

The relationship between 100Cr6 steelmaking, inclusion microstructure and rolling contact fatigue performance

A processing-microstructure-performance approach is followed to study three bearing steel samples manufactured from the most frequently used continuous casting routes. The inclusion microstructures of the samples were altered by varying the metallurgy and hot working conditions. Inclusion size distribution information is obtained, showing the steel-making route that results in the highest cleanliness. 3D analysis of inclusion morphologies using electrolytic extraction indicates the irregularities on the surface to be favourable sites for crack nucleation under RCF. Flat-washer and ball-on-rod tests were conducted to study the rolling contact fatigue life of the steels, with the results from the flat-washer testing method being more representative for bearing life. This research suggests that early fatigue of bearings is governed by silicate fragmentation and late fatigue by TiN inclusions.

Evolution of Oxide–Sulfide Complex Inclusions and Its Correlation with Steel Cleanliness During Electroslag Rapid Remelting (ESRR) of Tool Steel

The evolution of CaO-Al2O3-MgO-(SiO2) inclusions associated with CaS during electroslag rapid remelting (ESRR) of the tool steel with ultra low oxygen (8 ppm) under protective atmosphere was investigated. Thermodynamic calculation was performed to evaluate the oxygen level of liquid steel and the inclusion evolution during ESRR with the help of FactSage software (CON2 database). The results demonstrated that the reoxidation of liquid steel took place during industrial ESRR, resulting in the oxygen pickup of approximately double content. The oxygen level in the steel was determined by [Al]-[O] equilibrium during ESRR, whereas FeO in the slag transferred oxygen into the liquid steel, as indicated by the significant oxygen pickup. The inclusions in the steel electrode are oxide–sulfide type of CaO-Al2O3-MgO partially wrapped with CaS. The original oxide inclusions that had not been removed in ESRR process were transformed to liquid CaO-Al2O3-SiO2-MgO inclusions through reacting with the dissolved oxygen supplied from the reoxidation of liquid steel and concerned elements in liquid steel during ESRR. These CaO-Al2O3-SiO2-MgO inclusions were invariably associated with patch-type or shell-type CaS, which hold different formation mechanisms. The inclusions ranging from 2 to 4 µm take up a dominant proportion (a little more than 50 pct of the total inclusions) in the remelted ingots, and those larger than 8 µm account for about 3 pct. Melting rates of ESRR not only exerted a negligible effect on the steel cleanliness and the removal efficiency of oxide inclusions, but also on the inclusion size distribution.

Statistical analysis of high cycle fatigue life and inclusion size distribution in shot peened 300M steel

In order to fully exploit the benefits of shot peening process in terms of fatigue performance, the proper choice of peening conditions is indispensable, which is largely material specific. In this study, the influence of 3 different peening conditions on the axial fatigue life of high strength 300M steel (modified AISI 4340) was investigated in the high cycle fatigue regime. A statistical estimate of 90% survival life at 95% confidence interval was made to rigorously compare the fatigue performance of the material with different surface conditions. The peening induced roughness, compressive residual stresses and their relaxation during cyclic loading were quantified. It was however revealed, that shot peening had no significant effect on this material when tested at 55% of yield strength (σy,0.2). The fatigue life was dominated by the larger non-metallic inclusions within the bulk material. An empirical relationship between inclusion size and fatigue life was proposed based on this observation. Furthermore, the inclusion size distribution was well described using Gumbel extreme value distribution allowing the largest inclusion to be predicted in a given volume of steel. The prediction results were in good agreement with the experimentally observed value of the largest inclusion size observed at a fatigue crack initiation site.

Numerical Simulation of Collision-Coalescence and Removal of Inclusions in a Tundish

Knowledge on the behavior of inclusions in molten steel is crucial to study the fluid flow in the tundish. In this study, an inclusion mass/population conservation model and fluid mass/momentum/energy conservation model were coupled to investigate the spatial distribution of the inclusion volume concentration and inclusion size in the tundish. In this model, collision-coalescence among inclusions occurs due to turbulent collisions and Stokes collisions. The numerical results predict an inclusion size distribution that agrees with experimental data. The inclusion volume concentration decreases while the inclusion characteristic radius increases along the flow path of the molten steel. Furthermore, it is easy for inclusions to collide and aggregate with each other at the guide hole of the baffle, because there is strong turbulent flow there. Also, the inclusion characteristic radius in the distributing chamber is greater than that in the receiving chamber, while the inclusion volume concentration in the distributing chamber is less than that in the receiving chamber.

Toward Better Control of Inclusion Cleanliness in a Gas Stirred Ladle Using Multiscale Numerical Modeling.

The industrial objective of lowering the mass of mechanical structures requires continuous improvement in controlling the mechanical properties of metallic materials. Steel cleanliness and especially control of inclusion size distribution have, therefore, become major challenges. Inclusions have a detrimental effect on fatigue that strongly depends both on inclusion content and on the size of the largest inclusions. Ladle treatment of liquid steel has long been recognized as the processing stage responsible for the inclusion of cleanliness. A multiscale modeling has been proposed to investigate the inclusion behavior. The evolution of the inclusion size distribution is simulated at the process scale due to coupling a computational fluid dynamics calculation with a population balance method integrating all mechanisms, i.e., flotation, aggregation, settling, and capture at the top layer. Particular attention has been paid to the aggregation mechanism and the simulations at an inclusion scale with fully resolved inclusions that represent hydrodynamic conditions of the ladle, which have been specifically developed. Simulations of an industrial-type ladle highlight that inclusion cleanliness is mainly ruled by aggregation. Quantitative knowledge of aggregation kinetics has been extracted and captured from mesoscale simulations. Aggregation efficiency has been observed to drop drastically when increasing the particle size ratio.

A two-step mechanism in nucleation of solid silica from Fe-O-Si melt

In order to control the structure and size distribution of silica inclusions in high purity steel, it is necessary to understand the nucleation mechanism of solid silica in molten steel. In high temperature reactions, crystallization begins with nucleation, which plays a crucial role in determining the structure and size of solid products. Nucleation originates in the formation of product intermediates. The structure and thermodynamic properties of silica clusters as the intermediate of solid silica products during nucleation were calculated by density functional theory. Comparison of thermodynamic properties of silica clusters and silicon deoxidation equilibrium experiment in liquid iron results shows the silica clusters with most of the dissolved silicon and oxygen in equilibrium; the molten iron silicon deoxidation reaction ([Si] [Formula: see text] [O] [Formula: see text] cannot reach thermodynamic equilibrium state, and some deoxidation products could only exist in the form of silica clusters but not the solid silica. Therefore, the nucleation process of solid silica in Fe-O-Si melt can be considered as a two-step process with silica clusters as intermediates. Finally, there are two paths of solid silica inclusion formation: one is that in the molten iron, the dissolved silicon reacts with the dissolved oxygen to form silica clusters, and clusters further nucleate and grow up; the second one is that silica clusters directly crystallized during the cooling process of the melt.

Anti-fouling of submerged entry nozzle with electric current pulse

An effective method for anti-clogging of submerged entry nozzle (SEN) was developed by imposing an electric current pulse (ECP) between the SEN and the stopper in the continuous casting process. The morphologies and components of the adhered inclusions on the inner wall of SEN were examined. The size distribution and amounts of inclusions in the steel slab were measured and compared before and after treatment with ECP. After ECP treatment, the tap hole of SEN was only slightly clogged, the inner wall became smooth and the thickness of adhered inclusions decreased by about 50%. The ECP effect was also reflected in the inclusion amounts of the formed steel slab, which decreased by approximately 30% compared to the non-treated sample. These improvements were attributed to the ECP transferring excess negative charges to the molten steel side and maintaining a low or even a zero electric potential difference between the SEN and molten steel, which decreased the wettability and the interaction between the two phases.

New algorithms for virtual reconstruction of heterogeneous microstructures

A new set of algorithms is introduced for the virtual reconstruction of heterogeneous material microstructures, in which morphologies of embedded particles/fibers are explicitly represented. As a pre-processing phase, a shape library containing morphologies of heterogeneities, parameterized in terms of Non-Uniform Rational B-Splines (NURBS), is extracted from digital data such as micro-computed tomography images. Two packing algorithms are then introduced to reconstruct an initial (raw) periodic microstructure: In the first approach, a set of hierarchical bounding boxes approximating particle shapes are employed to check for overlap. The second approach, which is specialized for fibrous microstructures, uses the NURBS representation of fiber centerlines during the packing process. An optimization phase is applied to build the final microstructural model, relying either on the Genetic Algorithm to selectively eliminate some of the inclusions or their sequential relocation within the raw microstructure. The objective functions of this optimization phase are designed to replicate the target statistical microstructural descriptors such as the volume fraction, size distribution, and spatial arrangement of inclusions. Several example problems are presented to show the application of these algorithms for synthesizing various heterogeneous microstructures, as well as their finite element modeling and simulation.

Effects of Rare Earth Lanthanum on the Solidification Structure and Hot Ductility of Fe-43Ni Expansion Alloy

AbstractEffects of lanthanum content on the solidification structure and the hot ductility of Fe-43Ni expansion alloy were investigated, the corresponding mechanisms were also discussed. The results showed that the macrostructures of the alloys were first significantly refined with increasing lanthanum content in the range of 0~0.025 % and then became coarse again with lanthanum content up to 0.04 %. La2O2S inclusions can serve as the effective inclusions sites promoting the refinement of the macrostructures. The changes of the macrostructures were influenced by the quantity density and the size distribution of La2O2S inclusions. The addition of 0.01–0.025 % lanthanum can improve the hot ductility over the whole testing temperature range, especially at 1000–1050 °C. The improvement of the hot ductility was mainly associated with the grain boundary strengthening and the acceleration of dynamic recrystallization by adding lanthanum. With addition of 0.04 % lanthanum, the hot ductility of the alloy became deteriorated, which was owed to the presence of brittle Fe-Ni-La intermetallic compounds.

Effect of the Tundish Gunning Materials on the Steel Cleanliness

AbstractTo clarify the interaction mechanism between distinct tundish gunning materials (GM) and liquid steel, two kinds of gunning materials, namely MgO, Al2O3 GM, were tested. SEM, EDS, XRD and chemical analysis were carried out for steel and GM to investigate the change of chemical composition of steel in contact with GM and the interface microstructure between steel and GM after high temperature holding experiments. The steel cleanliness in terms of inclusion number density, size and size distribution was evaluated. It was found that the reducible component, low-melting-point phases and the pores in GM were passageway for steel penetration. The Al2O3 GM was less prone to steel penetration due to its poor wetting and the dense transition layer. MgO GM provided more oxygen and showed a stronger oxidizing capacity due to its higher content of reducible oxides (10.5 wt.% SiO2+2 wt.% Fe2O3). The use of Al2O3 GM resulted in an improved steel cleanliness and consequently could be a promising refractory in the tundish lining.

Population Size Distribution of Rare Earth and Non-metallic Inclusions in 4130 and 8630 Steels

The purpose of this work was to find the population size distribution of rare earth and non-metallic inclusions in polished samples and filter paper samples of 4130 and 8630 steels. The steels had additions of either rare earth silicide or EGR grain refiner. Interest in rare earth-containing inclusions has increased due to their ability to refine the solidification structure of steel. However, the exact mechanism is not fully understood. To accurately determine size and composition, electrolytic dissolution with 2% TEA was employed to dissolve the steel matrix away. A scanning electron microscope examined the isolated inclusions on filter paper specimens. For comparison, other samples were analyzed in a more typical polished metallographic specimen. All heats had very similar inclusion sizes. Most inclusions were between 5 and 9 μm. There was a variation in inclusion composition between the 4130 and 8630 heats. The cause of this variability appeared to be due to random changes in the amount of reoxidation that occurred during tapping.

The Formation Mechanism of Mn–Al–O Inclusions in Fe–Cr–Mn Stainless Steel during Continuous Casting

The formation mechanism of Mn–Al–O inclusions in Fe–Cr–Mn stainless steel during continuous casting is investigated by industrial trials and thermodynamic calculation. The morphology, composition, and size distribution of inclusions in steel specimens are analyzed by scanning electron microscopy and energy dispersive spectroscopy. The main inclusions change from spherical Ca–Si–O and Ca–Si–Mn–O inclusions during LF refining to Mn–Al–O inclusions in continuous casting slab and hot‐rolled sheet. The size of most Mn–Al–O inclusions containing high MnO content is smaller than 4 µm. The formation of these inclusions is consistent with thermodynamic calculation, which indicates that MnO and Al2O3 inclusions are formed during continuous casting process. The calculation results of MnO and Al2O3 inclusions growth shown that the size of MnO inclusion (4 µm) is much larger than that of Al2O3 inclusion (0.4 µm) at the end of solidification, which also accords with the characteristics of inclusions in continuous casting slab and hot‐rolled sheet.

The influence of the carbon addition on the microstructure of a U-Nb alloy and the features of Nb2C inclusions

The effects of the carbon addition on the morphology, composition, size distribution and formation mechanism of inclusions in a U-5.5 Nb alloy were discussed. The influence of the carbon content on the microstructure and hardness were also investigated. The methods used in the present study were scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, optical microscopy, and hardness measurements. The results show that the carbon content obviously affects the morphology, size distribution and area fraction of the Nb2C inclusions. Moreover, characterization of the inclusion morphology shows that the Nb2C inclusions form in the liquid and subsequently grow, collide and agglomerate to form clusters. Meanwhile, the average grain size significantly decreases, and the hardness increases with increasing carbon content in the U-5.5 Nb alloy.

Characterization of Inclusion Populations in Mn-Si Deoxidized Steel

Four plant heats of Mn-Si deoxidized steel were conducted to follow the evolution of the inclusion population through ladle furnace (LF) treatment and subsequent vacuum treatment (VT). The liquid steel was sampled, and the chemical composition and size distribution of the inclusion populations were characterized. The Gumbel generalized extreme-value (GEV) and generalized Pareto (GP) distributions were used for the statistical analysis of the inclusion size distributions. The inclusions found at the beginning of the LF treatment were mostly fully liquid SiO2-Al2O3-MnO inclusions, which then evolved into fully liquid SiO2-Al2O3-CaO-MgO and partly liquid SiO2-CaO-MgO-(Al2O3-MgO) inclusions detected at the end of the VT. The final fully liquid inclusions had a desirable chemical composition for plastic behavior in subsequent metallurgical operations. The GP distribution was found to be undesirable for statistical analysis. The GEV distribution approach led to shape parameter values different from the zero value hypothesized from the Gumbel distribution. According to the GEV approach, some of the final inclusion size distributions had statistically significant differences, whereas the Gumbel approach predicted no statistically significant differences. The heats were organized according to indicators of inclusion cleanliness and a statistical comparison of the size distributions.

Single-step generation of metal-plasma polymer multicore@shell nanoparticles from the gas phase

Nanoparticles composed of multiple silver cores and a plasma polymer shell (multicore@shell) were prepared in a single step with a gas aggregation cluster source operating with Ar/hexamethyldisiloxane mixtures and optionally oxygen. The size distribution of the metal inclusions as well as the chemical composition and the thickness of the shells were found to be controlled by the composition of the working gas mixture. Shell matrices ranging from organosilicon plasma polymer to nearly stoichiometric SiO2 were obtained. The method allows facile fabrication of multicore@shell nanoparticles with tailored functional properties, as demonstrated here with the optical response.

Calculating of the True Sizes and the Numbers of Spherical Inclusions in Metal

Observing inclusions on a polished plane, researchers do not see these inclusions directly, but only their cross sections. Meanwhile, the given size of a section can be obtained from the inclusions of different sizes. The true sizes of the inclusions and their quantities are hidden from the researchers. This paper proposes a new method for determining the size distribution of inclusions derived from the size distribution of their sections. The method based on mathematical statistics allows evaluating the true sizes and quantities of inclusions. A notable feature of the method is that it enables a researcher to derive the confidence sets for the distribution functions. A special technique for testing the method has been developed. Numerous tests have shown good adequacy of the method.

Inclusions properties at 1673\u2009K and room temperature with Ce addition in SS400 steel

Inclusion species formed in SS400 steel with Ce-addition was predicted by thermodynamic calculation. The analysis of the inclusion morphology and size distribution was carried out by applying Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM). Nano-Fe3O4 particles were also found in cerium-deoxidized and -desulfurized steel and their shapes were nearly spherical. The complex Ce2O3 inclusions covering a layer of 218 nm composed by several MnS particles with similar diffraction pattern. Most importantly, the complex Ce2O3 characterized by using TEM diffraction is amorphous in the steel, indicating that Ce2O3 formed in the liquid iron and then MnS segregated cling to it.

Effect of Mg Addition on the Refinement and Homogenized Distribution of Inclusions in Steel with Different Al Contents

To investigate the effect of Mg addition on the refinement and homogenized distribution of inclusions, deoxidized experiments with different amounts of aluminum and magnesium addition were carried out at 1873 K (1600 °C) under the condition of no fluid flow. The size distribution of three-dimensional inclusions obtained by applying the modified Schwartz–Saltykov transformation from the observed planar size distribution, and degree of homogeneity in inclusion dispersion quantified by measuring the inter-surface distance of inclusions, were studied as a function of the amount of Mg addition and holding time. The nucleation and growth of inclusions based on homogeneous nucleation theory and Ostwald ripening were discussed with the consideration of supersaturation degree and interfacial energy between molten steel and inclusions. The average attractive force acted on inclusions in experimental steels was estimated according to Paunov’s theory. The results showed that in addition to increasing the Mg addition, increasing the oxygen activity at an early stage of deoxidation and lowering the dissolved oxygen content are conductive to the increase of nucleation rate as well as to the refinement of inclusions Moreover, it was found that the degree of homogeneity in inclusion dispersion decreases with an increase of the attractive force acted on inclusions, which is largely dependent on the inclusion composition and volume fraction of inclusions.