Size Distribution Of Inclusions Research Articles

An Online Monitoring System for In Situ and Real-Time Analyzing of Inclusions within the Molten Metal.

Traditional methods for assessing the cleanliness of liquid metal are characterized by prolonged detection times, delays, and susceptibility to variations in sampling conditions. To address these limitations, an online cleanliness-analyzing system grounded in the method of the electrical sensing zone has been developed. This system facilitates real-time, in situ, and quantitative analysis of inclusion size and amount in liquid metal. Comprising pneumatic, embedded, and host computer modules, the system supports the continuous, online evaluation of metal cleanliness across various metallurgical processes in high-temperature environments. Tests conducted with gallium liquid at 90 °C and aluminum melt at 800 °C have validated the system's ability to precisely and quantitatively detect inclusions in molten metal in real time. The detection procedure is stable and reliable, offering immediate data feedback that effectively captures fluctuations in inclusion amount, thereby meeting the metallurgical industry's demand for real-time analyzing and control of inclusion cleanliness in liquid metal. Additionally, the system was used to analyze inclusion size distribution during the hot-dip galvanizing process. At a zinc melt temperature of 500 °C, it achieved a detection limit of 21 μm, simultaneously providing real-time data on the size and amount distribution of inclusions. This represents a novel strategy for the online monitoring and quality control of zinc slag throughout the hot-dip galvanizing process.

Scanning electron microscopy analysis of non-metallic inclusions for making steels with superior mechanical properties

The objective of this novel research was to further understand the type, size and areal distribution of the non-metallic inclusions in bearing steels by applying state-of-the-art scanning electron microscopy (SEM) analysis in order to develop steels with superior properties. Ten samples were taken from bearing steel grade 52100 and analysed by SEM. It was concluded that SEM allows deeper understanding regarding the type, morphology, size, and distribution of the non-metallic inclusions by covering larger sample areas and accurate automatic energy dispersive X-ray microanalysis of the inclusions. While most of the non-metallic inclusions had an equivalent circle diameter (ECD) smaller than 20 µm, the main type of inclusions with ECDs larger than 20 µm were calcium aluminates. As the higher sulphur will tend to create sulphide type of inclusions and the lower sulphur will shift the inclusions towards calcium aluminate oxide types, it is recommended to keep the sulphur content at amounts above threshold that calcium aluminates appear.

Modeling the Precipitation of Aluminum Nitride Inclusions during Solidification of High‐Aluminum Steels

High‐aluminum advanced high‐strength steels have received increasing interest due to their excellent combination of strength and ductility. The control of nonmetallic inclusions in steel is among the most important issue for the production of high‐aluminum steel. This study proposes a model for the evolution of size distributions of AlN inclusions during solidification of steel based on the Kampmann–Wagner numerical model and microsegregation calculation. Both homogeneous (pure AlN) and heterogeneous precipitations (AlN+oxide or MnS) are described using homogeneous nucleation and free growth models of Greer et al. respectively. The model is applied to calculate the size distributions of AlN in high‐Al (up to 5%) Fe–Cr–Al steels and high‐ and medium‐manganese steels and validated by the experimental data in the literature. The model correctly describes the influence of cooling rates on the precipitation of AlN in Fe–Cr–Al steels and high‐manganese steels, and the sizes of AlN are reduced and the number densities of AlN inclusions are increased by increasing the cooling rate. The effects of nitrogen and aluminum concentration in medium‐manganese steel on inclusion precipitation are investigated by the model calculation. The increases in nitrogen and aluminum concentration facilitate the homogeneous precipitation of AlN inclusions.

Automated feature analysis as a tool for non-metallic inclusion analysis in solidified metals

In-depth analysis of the non-metallic inclusion population in solidified metals is essential considering the high cleanliness requirements for metallic components. For this purpose, automated feature analysis (AFA) is a powerful inclusion analysis tool, providing statistical supported information about quantity, elemental composition, morphology and size of inclusions. However, thorough data evaluation is imperative to ensure accurate and reliable results. The paper introduces the key principles of evaluating AFA data, emphasizing its capabilities and constraints by utilizing four large datasets obtained from solidified steel blocks, each containing a minimum of 4000 features. Additionally, methodologies for identifying characteristic inclusion species within a dataset, constructing suitable rulefiles for inclusion classification through statistical analyzes, and interpreting the resulting outcomes are presented. The size distribution of inclusions is analyzed using population density functions, focusing on the absolute inclusion count within specific size ranges. Cluster analysis is presented considering the inclusions‘ positional parameters.

Oxide Inclusions in Aluminum-deoxidized Ultra-low CarbonSteel

RH (Ruhrstahl-Heraeus) degassing process was confirmed to be an effective method for making the steel cleaner by comparing the samples before and after RH degassing, mainly on the area of the total inclusion, the total number of inclusions, the mean area of inclusions, and inclusion size distribution. Four main types of inclusions including alumina and titanium oxides, and Al-Ti-O complex oxides were studied by analyzing their formation mechanisms, compositions, and morphology using SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectroscopy). Thermodynamic analysis through kinetic simulations of the different stages of RH degassing was conducted by the FactSageTM software package. Based on the equilibrium amount of oxides in the liquid steel, the effects of system temperature, oxygen contents, and alloy additions on the formation of inclusions and nozzle clogging were discussed to improve the steel’s cleanliness.

Modeling of oxide inclusions in steel casting

A model is presented that predicts the amount and location of oxide inclusions in steel castings. A number and size distribution of inclusions, defined about a mean diameter, enters the casting system at its inlet during the filling process and are transported to their final locations in the casting. Model parameters for inclusion density, drag and wall friction are used to calculate the motion and locations of the oxide particles. Model results are presented to study the effects of casting shape and surface orientation on the final inclusion locations and distributions within castings. These results are compared with inclusion tracking experiments where the geometry of the gating system and orientation of casting cope surfaces affect the final distribution of inclusions in the castings. Measured and simulated inclusion area percent coverage, inclusion count and mean diameter are compared for a range of modelling parameters and inclusion size distributions. The size and number distribution at the casting system inlet, and other model parameters, are determined which provide the best agreement between measured and simulated inclusion area, count, and size.

Effect of cooling rate on non-metallic inclusion formation and precipitation and micro-segregation of Mn and Al in Fe–23Mn–10Al–0.7C steel

The present study assesses the influence of the cooling rate on the morphology, composition, number density, size distribution of inclusions, and microsegregation of elements in Fe–23Mn–10Al–0.7 steel. The results indicate that with the increase of cooling rate from 5.1 K/s to 14.51 K/s, the total number density of inclusions increases from 28 mm−2 to 32 mm−2, with no change in the type of inclusions, the average size of MnS inclusion decreases from 9.57 μm to 5.21 μm. The precipitation and growth of MnS inclusion are predicted according to the coupled model, matching well with the experimental results. Furthermore, it is observed that AlN inclusion formed in the liquid steel can float up to the surface of the liquid steel, reducing the dissolved nitrogen content in the steel. As the cooling rate increases, the size and density of AlN inclusions on the liquid steel surface decrease. Combining the lattice mismatch of inclusions and the pushing and engulfment behavior of inclusions, the effect of cooling rate on the MnS precipitation for Al2O3 and AlN is analyzed. Moreover, under different cooling rates, Al segregation is very remarkable and it is low in interdendritic regions but high in dendrite stems.

Effects of Rare Earth La–Ce Alloying Treatment on Modification of Inclusions and Magnetic Properties of W350 Non-Oriented Silicon Steel

In order to study the effects of rare earth La–Ce alloying treatment on the characteristics of inclusions in non-oriented silicon steels, industrial experiments were conducted studying the composition, morphology, size and quantity of inclusions in W350 non-oriented silicon steel during the RH (Ruhrstahl-Hereaeus) refining process and tundish process, after rare earth treatment. The products were analyzed by means of ICP-MS (inductively coupled plasma mass spectrometry), SEM/EDS (scanning electron microscope-energy dispersive spectrometry), and ASPEX (automated SEM/EDS inclusion analysis). The research results showed that the types of inclusions in experimental steel changed significantly after rare earth treatment. The types of inclusions after RE (rare earth) treatment are typically rare earth composite inclusions that are mainly composed of (La, Ce)Al2O3, and conventional inclusions. The addition of rare earth promotes the agglomeration of inclusions; the morphologies of the inclusions are mostly blocky, and some are distributed in long strips. After rare earth treatment during the RH refining process, the number of inclusions with sizes of 1.0~3.5 μm in the experimental steel is increased, and the average size of the inclusions is 2.66 μm. In addition, the number of inclusions larger than 4 μm in the specimens increases due to the collision and growth of inclusions caused by the RH circulation. After rare earth treatment during the tundish process, the number of micro inclusions with sizes of 1.0~2.5 μm in the specimen steels decreases, while the number of inclusions larger than 5 μm increases. The size distribution of micro inclusions in hot-rolled sheets after rare earth treatment was studied using TEM (transmission electron microscopy). In the specimens without rare earth, the content of micro inclusions (≤1 μm) is 51,458.2/mm2 and the average size is 0.388 μm. In the specimens with rare earth added, the content of micro inclusions (≤1 μm) is 24,230.2/mm2 and the average size is 0.427 μm. Compared to sheet produced by the original process, the iron loss of the 0.35 mm finished experimental sheet is reduced by 0.068 W/kg, and the magnetic induction is increased by 0.007 T. The iron loss of the 0.50 mm finished experimental sheet is reduced by 0.008 W/kg, and the magnetic induction is increased by 0.004 T. After rare earth treatment, the average size of micro inclusions increases and the magnetic properties are obviously improved.

Modification of Rare Earth Ce on Inclusions in W350 Non-Oriented Silicon Steel

In this paper, the effect of rare earth Ce content on the morphology, composition, type and size distribution of inclusions in W350 non-oriented silicon steel was investigated by means of ICP-MS (inductively coupled plasma mass spectrometry), SEM/EDS (scanning electron microscope-energy Dispersive Spectrometer), and ASPEX (automated SEM/EDS inclusion analysis). The results showed that with the increase of Ce content in the steel, the modification sequence of inclusions was CeAlO3→Ce2O2S→CexSy. The type and size distribution of inclusions in the steel obviously changed with the difference in added Ce content. When the added Ce content in the steel was 10 ppm, 14 ppm, 20 ppm and 30 ppm respectively, the rare earth inclusions were mainly CeAlO3-Ce2O2S. Furthermore, when the added Ce content increased to 60 ppm, the rare earth inclusions were mainly Ce2O2S with a small amount of CeAlO3 contained in part inclusions. When the added Ce content increased continually to 95 ppm, the rare earth inclusions were mainly CexSy-Ce2O2S. The critical Ce content for the conversion between CeAlO3 and Ce2O2S was 41 ppm. To ensure that inclusions transform from CeAlO3 to Ce2O2S, the Ce content in the steel should be greater than 41 ppm. Under the current experimental conditions, it was found that when the Ce content was 20 ppm, the number density and proportion of inclusions in the steel were lower, and their average size was larger. When the added Ce content increased to 95 ppm, the number density of inclusions in the steel significantly increased, which deteriorated the steel cleanliness.

COMBINED TECHNIQUES AND RELEVANT IMAGE PROCESSING FOR QUANTITATIVE STATISTICAL CHARACTERIZATION OF INCLUSIONS IN ELASTOMERS

ABSTRACT The properties of elastomeric materials are strongly influenced by the inclusions resulting from the ingredients and the elaboration process. A methodology is proposed to differentiate the inclusions harmful for fatigue (larger than a few micrometers) in elastomers according to their chemical nature, and to characterize them quantitatively with sufficient statistics. Three techniques are used and compared: digital optical microscopy (OM), scanning electron microscopy (SEM) associated with energy dispersive X-ray spectroscopy, and X-ray micro-computed tomography (μ-CT). Six materials are used to challenge the methodology. In addition to the usual metal oxides and carbon black agglomerates, three atypical types of inclusions are highlighted, generating specific detection difficulties. A relevant image analysis procedure is developed to automatically detect the inclusions from the acquired images, more objectively and accurately than with the classical thresholding methods. The morphology and the spatial distribution of the different inclusions populations are then determined. μ-CT is the most comprehensive and accurate method for classification and statistical characterization of inclusions. Furthermore, relevant data on the size distribution of inclusions can be obtained using backscattered electrons (SEM-BSE) or digital OM. SEM-BSE provides more accurate results than digital OM.

Effect of cerium on microstructure and microsegregation behavior of novel cryogenic high-Mn austenitic steel weld metal

The novel cryogenic high-Mn austenitic steel weld metal with four different cerium (Ce) contents were prepared under submerged arc welding by adding cerium dioxide and calcium silicon reducing agents into the flux to refine the solidification structure and alleviate the microsegregation. The effects of the Ce element on the microstructure, inclusion, and microsegregation behavior of weld metal were systematically investigated via optical, scanning, and transmission electron microscopy and using an electronic probe micro-analyzer. The results showed that the dendrite arm spacing of high-Mn austenitic steel weld metal was significantly reduced with an increase in the Ce content from 0.018 to 0.087 wt%. The typical inclusions in the weld metal were mainly Al2O3, CeAlO3, Ce2O3, and Ce2O2S for the Ce content ranging from 0 to 0.087 wt%. The number density and the size distribution of effective inclusions influenced the microstructure variation. Numerous small-sized effective inclusions (Ce2O3 and Ce2O2S) in the weld metal with 0.087 wt% Ce were distributed at the dendrite core, promoting the nucleation for austenite during the solidification and refining the dendrite structures. The co-segregation of Mn, C and Si occurred in the interdendritic regions. The segregation ratio of Mn, C and Si gradually decreased with the increase in Ce content, alleviating the element microsegregation.

Spall Fracture of Solid and Molten Copper: Molecular Dynamics, Mechanical Model and Strain Rate Dependence

In this study, we formulate a mechanical model of spall fracture of copper, which describes both solid and molten states. The model is verified, and its parameters are found based on the data of molecular dynamics simulations of this process under ultrahigh strain rate of tension, leading to the formation of multiple pores within the considered volume element. A machine-learning-type Bayesian algorithm is used to identify the optimal parameters of the model. We also analyze the influence of the initial size distribution of pores or non-wettable inclusions in copper on the strain rate dependence of its spall strength and show that these initial heterogeneities explain the existing experimental data for moderate strain rates. This investigation promotes the development of atomistically-based machine learning approaches to description of the strength properties of metals and deepens the understanding of the spall fracture process.

Characterization of Inclusion Size Distributions in Steel Wire Rods.

The control of inclusions in steel components is essential to guarantee strong performance. The reliable characterization of inclusion populations is essential not only to evaluate the quality of the components but also to allow the use of analytical procedures for the comparison and discrimination of inclusion populations. In this work, inclusion size distributions in wire rod specimens from six plant-scale heats were measured and analyzed. For the measurements, the metallographic procedure specified in the ASTM E2283 standard was used. The population density function (PDF) approach and the extreme value statistical procedure specified in the ASTM E2283 standard were used to analyze the whole size distribution and the upper tail of the size distribution, respectively. The PDF approach allowed us to identify differences among inclusion size distributions and showed that new inclusions were not formed after the liquid steel treatment process. The extreme value statistical procedure led to the prediction of the maximum inclusion length for each heat, which was used for the statistical discrimination of heats. Furthermore, the estimation of the probability of finding an inclusion larger than a given inclusion size using the extreme value theory allowed us to order the heats for different critical inclusion sizes.

Evolution of inclusion populations in Al-killed steel during the steelmaking process

The increasing demand for higher steel inclusion cleanliness has motivated control over the formation and evolution of inclusions during the production process. To generate knowledge of the formation and evolution of inclusions during the production of Al-killed steel slabs, the evolution of the chemical composition and size distribution of inclusions throughout the process, including ladle furnace (LF) treatment and continuous casting (CC), was studied. Liquid steel sampling was conducted throughout the process. The chemical composition was measured using the EDS technique, and the size distribution analysis was performed with the population density function (PDF) approach. The upper tail of the size distributions was analyzed by generalized extreme value (GEV) theory. Evolution of the chemical composition of inclusions involved the following path: solid Al2O3 solid Al2O3-MgO partly liquid Al2O3–MgO–CaO fully liquid Al2O3–MgO–CaO. The PDF analysis accounted for the evolution of the size distribution, which was supposed to be driven by the balance of the coalescence/growth and collision/breakage of inclusions and their removal. Finally, the GEV approach allowed us to describe the evolution of large inclusions and compare inclusion populations in terms of survival probability.

Influence of Pulse Current on Inclusion Properties of Alumina in Molten Steel

In the process of metal purification, the study of controlling the morphology and size distribution of non-metallic inclusions in steel based on electric fields has attracted extensive attention. However, the action mechanism of electric fields on inclusions in liquid steel has not been clearly identified. In this paper, the influence of pulse current on the quantity, size, and distribution of alumina inclusions in liquid steel was explored through a high-temperature energization experiment, and the action mechanism of pulse current was expounded based on the angle of interface free energy. The results show that the number of small alumina inclusions in the steel after electric pulse treatment (the pulse current density was 0.1–3 A/cm2, the frequency was 100 Hz, and the pulse waveform was a square wave) was significantly increased compared with the sample without electric pulse treatment, and the particle size was concentrated at 2–5 μm, and the inclusions were concentrated in the upper and lower parts of the sample. However, in the samples without electrification treatment, the large particles of inclusions are the majority, the particle size was concentrated at about 10 μm, and the inclusions were concentrated in the upper and middle parts of the samples. When the pulse current was applied to the molten steel, the interfacial free energy of the internal system of liquid steel alumina inclusion was reduced, the nucleation of alumina inclusion was promoted, the aggregation growth between alumina particles was inhibited, and then the migration and distribution of inclusions were also affected. The experimental results could provide technical support for high-quality steel smelting production to a certain extent.

A microporous MgO-MgAl2O4 functional refractory for small inclusions removal of tundish: Preparation and parameters optimization

A microporous MgO–MgAl2O4 gas-permeable brick was fabricated for use in tundish to remove small inclusions in liquid steel using argon bubbles, based on the optimization of particle gradation. The effect of activated alumina addition on the properties and pore size distribution of microporous MgO–MgAl2O4 bricks was investigated. The flow rate parameters of argon for inclusion removal were optimized. The results showed that the microporous MgO–MgAl2O4 permeable brick, prepared by adding 5 wt% activated alumina, had a minimum average pore diameter of 10.9 μm and greater air permeability compared to no introduction of activated alumina. The thermal stability was significantly improved due to the long cone-shaped magnesium-rich spinels generated by the solid-state reaction between magnesium oxide and activated alumina distributed in the pores; this further remodeled the structure of the pores. The addition of more activated alumina caused a sharp drop in the volume density and strength and formed more spinels, with the morphology of spinels changing from long cone to octahedron with larger average pore size; these are not beneficial to the production and application of gas-permeable brick. When the flow rate was 60 L/min, the total oxygen content (T.[O]) in the billet was reduced by 7 ppm, the content of pores and cracks in the billet decreased dramatically, and the removal rates of inclusion size distributions of 20–50 μm, 50–100 μm, and >100 μm in the billets increased by 15%, 20%, and 61%, respectively.

NaCl Crystals as Carriers for Micronutrient Delivery.

Iron deficiency leading to anemia is one of the most severe and important nutritional deficiencies in the world today. To combat this deficiency, the fortification of food products with iron is a natural way to increase the global iron uptake. Here, we report a novel strategy for iron encapsulation in NaCl crystals via microscopic inclusions containing dissolved iron salt. The liquid inclusions embedded in the crystal insulate the reactive iron salts from their environment while assuring that iron is in a soluble and bioavailable form. While the size distribution of inclusions remains independent of the evaporation conditions, their density increases during crystallization at lower relative humidity. Using Raman confocal microspectroscopy, we have been able to analyze the morphology, length/thickness ratio, of inclusions and show that inclusions evolve toward a plate-like structure with the increase in size. By growing a pure NaCl shell around the iron-containing NaCl crystals, the stability of the composite crystals can be even further enhanced. The role of halite crystals as a carrier for iron fortification opens the way for the delivery of other types of micronutrients by including them in table salt.

Slow Migration of Brine Inclusions in First-Year Sea Ice

We derive a thermodynamically consistent model for phase change in sea ice by adding salt to the framework introduced by Penrose and Fife. Taking the salt entropy relative to the liquid water molar fraction provides a transparent mechanism for salt rejection under ice formation. We identify slow varying coordinates, including salt density relative to liquid water molarity weighted by latent heat, and use multiscale analysis to derive a quasi-equilibrium Stefan-type problem via a sharp interface scaling. The singular limit is under-determined and the leading order system is closed by imposing local conservation of salt under interface perturbation. The quasi-steady system determines interface motion as balance of curvature, temperature gradient, and salt density. We resolve this numerically for axisymmetric surfaces and show that the thermal gradients typical of arctic sea ice can have a decisive impact on the mode of pinch-off of cylindrical brine inclusions and on the size distribution of the resultant spherical shapes. The density and distribution of inclusion sizes is a key component of sea ice albedo which factors into global climate models.

Profiling inclusion characteristics in submerged arc welded metals of EH36 shipbuilding steel treated by CaF2–TiO2 fluxes

EH36 shipbuilding steel has been submerged arc welded under 6 kJ mm−1 heat input employing CaF2–TiO2 fluxes. Ensuing weld metals have been examined with an emphasis on inclusion characteristics. Compositional-wise, the inclusion ensemble is largely categorised as a complex Ti-containing type. It is demonstrated that, as a function of TiO2 content, the average Ti content in the inclusions is gradually enhanced, which is compensated by the simultaneous reduction of Al and Mn. Meanwhile, inclusion size distribution curves show log-normal patterns with the frequency peaks ranging from 0.3 to 0.4 μm. Furthermore, inclusion number density and volume fraction show a definitive increasing trend, which are concurrent to the O uptake from 110 to 210 ppm enabled by TiO2 decomposition.

Mechanical characterization of highly heterogeneous brittle materials by optical techniques

Fragmentation processes like crushing and grinding are complex and extensively energy-consuming activities in the mining and mineral processing industry. By studying the processes and the typically brittle material involved in a virtual environment, i.e. numerical simulations, knowledge will be gained to support improvement of the efficiency and thereby meet established environmental goals. Although, a challenge is the lack of experimental data both for calibration and validation hampering the development of constitutive models. As a case of study, a mechanical characterization of MnSiFe-slag was performed. X-ray Computed Tomography was used for 3D imaging and quantitative characterization of the material texture, with focus on the shape, size and spatial distribution of inclusions. Diametral and axial compressive tests under quasi-static conditions were used to load the mineral material and obtain a strain field (ε) during increasing and cyclic loading until failure accounting for progressive damage. The evolution of the strain captured by digital image correlation (DIC) techniques exposed a mechanical behavior of composite-like material where random failure of the components caused high variability of the elastic parameters. These were found to be load dependent and they are strongly related to the ability of the material to internal re-arrangement during loading. Irreversible damage affects the structure of the material and it is perceived as non-linearities in the load–strain curves. It was found a degradation of the material under repetitive loading. A decrease of the elastic modulus exposes a weakening of the matrix and dominant behavior of the inclusions on the mechanical response of the material.