Inclusion Collision Research Articles

Numerical Simulation of Inclusion Collision Growth and Removal in a Tundish with Intermittent Induction Heating

Numerical Simulation of Inclusion Collision Growth and Removal in a Tundish with Intermittent Induction Heating

Research on directional solidification combined with electron beam melting and refining for recycling of FGH4096 alloy scraps

The constraints of traditional manufacturing techniques have led to the generation of a considerable amount of waste superalloy, causing substantial resource wastage. The primary concern with waste superalloys lies in the excessive presence of inclusions and impurity elements, rendering them unsuitable for further utilization. This study proposes the use of directional solidification combined with electron beam melting and refining (EBMR) to prepare FGH4096 superalloy ingots (Φ120 mm), which offers a promising approach to produce large-sized powder superalloy master alloy ingots with high-purity and high homogeneity. It is found that the secondary dendrite arm spacing and the size of the γ’ phase in the alloy are significantly reduced after EBMR treatment. The concentration of O and N can be decreased to 5.7 and 0.6 ppmw, respectively. The size of inclusion can be reduced below 8.69 μm and the inclusion numbers reduce by over 50 % compared with both conventional ingots. A droplet transfer mode and melt convection mode mechanism have been proposed, which accurately predicts the melting temperature and melt flow. A quantitative study is conducted on the influence of inclusion density, the contact angle between inclusions and melt, and the surface tension of the melt on capillary forces. The results indicate that the capillary forces between inclusions in the melt range from 1.8 × 10−19 N and 1.9 × 10−17 N. Furthermore, the collision-aggregation behavior of inclusions in the melt is discussed, and an estimate of the tendency of inclusion collision-aggregation is provided. The enrichment of inclusions in the EBMR ingot is primarily the result of turbulent collision. The Marangoni effect and the extremely high surface temperature of the melt promote the collision and agglomeration of inclusions, causing them to accumulate rapidly at the melt surface. Moreover, the thorough removal of inclusions through the decomposition and dissolution process of the electron beam offers theoretical backing for the preparation of superalloys through electron beam melting and high-purity refining.

Numerical study on inclusion collision, coalescence and removal in an extra-thick slab continuous casting mold with M-EMS

Surface flaw detection is one of the main problems of extra-thick slab. In practice, it is considered that the application of mold electromagnetic stirring (M-EMS) is an effective means to reduce the inclusions located at the subsurface of thick slab. The present study conducted numerical studies on the inclusion transports in an extra-thick slab continuous casting mold with the effects of M-EMS. The influences of M-EMS on the inclusion collision, coalescence and removal were revealed. The predicted results indicate that the majority of inclusions entering the mold are smaller than 20 µm. The application of M-EMS promotes the collision, aggregation, and flotation of these inclusions. When the inclusions entering the mold are larger than 30 µm, the flotation removal of inclusions significantly increases, and the collision and aggregation among inclusions decreases accordingly. Furthermore, the predicted results show that inclusions larger than 200 µm in size are unlikely to follow the downward flow into the lower region of the mold, with the primary removal location concentrated near the nozzle. Large-size inclusions have been quantitatively extracted from samples with and without M-EMS using galvanostatic electrolysis method. The results indicate that the inclusions of various sizes in the slab surface layer are reduced when M-EMS is employed. Notably, inclusions sized 50–150 µm show the most significant reduction, with their mass density decreasing from 38.17 mg/10 kg to 15.11 mg/10 kg. This demonstrates a substantial reduction in large-size inclusions on the slab surface layer following the introduction of M-EMS in the mold.

Numerical simulation of collision-coalescence and removal of inclusion in split swirling flow tundish

The swirling flow generated by the swirling chamber of the split swirling flow tundish can effectively promote the collision and growth of inclusions. The split swirling flow tundish can promote the removal of inclusions by improving the flow field. In this work, the CFD-PBM coupling model was applied to simulate the transport, aggregation, and floating removal of inclusions in the split swirling flow tundish, and compared with a same-size T-type tundish. The results indicated that the swirl flow can effectively promote the collision-coalescence of inclusions. Comparing the flow field of the split swirl tundish and the T-type tundish, the dead flow fraction of the two tundishes is similar, but the plug flow fraction of the split swirling flow tundish is 4.5% larger than the T-type tundish. Monitoring the volume concentration of inclusions at the outlet of the two tundishes, the inclusion removal rate of the T-shaped tundish and split swirling flow tundish are 29.28% and 34.33%, respectively. Therefore, the split swirling flow tundish is stronger than the T-shaped tundish in removing inclusion. Especially in the removal of small inclusions, the number density of 1.00–28.64 µm inclusions at the outlet of the split swirling flow tundish is 29.97%–65.91% lower than the T-type tundish, the split swirling flow tundish enhances the removal of small inclusions.

Simulation of Inclusion Removal in Bottom-blowing Ladle with Tracking the Collision of Inclusions and Bubbles in Transient Time Steps

Simulation of Inclusion Removal in Bottom-blowing Ladle with Tracking the Collision of Inclusions and Bubbles in Transient Time Steps

Phase analysis of complex non-metallic inclusions in Al-deoxidized 42CrMo4 steel after contact with MgO–C refractories

This study extensively investigated characteristic non-metallic inclusions in oxidized and deoxidized 42CrMo4 steel after contact to MgO–C refractories, proposing possible formation and modification mechanisms of non-metallic inclusions. The structures and compositions of different inclusion species were analyzed, revealing various types: crystalline, amorphous, and complex inclusions containing both crystalline and amorphous phases. The latter always consisted of an amorphous Mn–Si–Al–O matrix containing various crystalline phases such as Al2O3, MnAl2O4 and/or MnTiO3. The formation of amorphous Mn–Si–Al–O inclusions was attributed to steel melt oxidation, while pure crystalline corundum inclusions resulted from both the steel melt oxidation and deoxidation. Alumina inclusions exhibited different shapes, likely because of variations in aluminum and oxygen supersaturation in the steel melt during their formation. Complex inclusions were suggested to form through precipitation on existing inclusions and mutual collision of pre-existing inclusions, facilitated by the non-wetting behavior of solid alumina inclusions in the steel melt.

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.

Multiphase Simulation on the Collision, Transport, and Removal of Non-metallic Inclusions in the Molten Steel During RH Refining

Multiphase Simulation on the Collision, Transport, and Removal of Non-metallic Inclusions in the Molten Steel During RH Refining

Modeling method for rock heterogeneities and multiple hydraulic fractures propagation based on homogenization approach and PHF-LSM

Hydraulic fracturing is an important technique to enhance the production rate of oil and gas. We extend the functions of Permeability-based Hydraulic Fracture, Level Set Method (PHF-LSM) by including homogenization approaches to take into account the influence of the heterogeneities of rock media at both mesoscale and macroscale during hydraulic fracture propagation. The center position pattern of mesoscale heterogeneities is generated by introducing the Fast Poisson Disk (FPD) approach with an inherent parameter controlling the randomly distributed inclusions, and we developed an algorithm to detect inclusion collision by binary image matrix calculation. The level set function is used to describe the distributed joints at the macroscale. Both numerical and theoretical homogenization approaches are applied to study the characteristics of the material properties of rock matrices with randomly distributed hard inclusions at the mesoscale. Based on these results, we adopt the Mori–Tanaka (MT) and the Halpin–Tsai (HT) methods to homogenize the elasticity parameters (elastic modulus and Poisson’s ratio) and the hydraulic conductivity of the rock material, respectively. The Voigt upper bound is applied to estimate the tensile strength of the rock material at the integration points. A series of numerical simulations first indicated that the proposed method can model multi-scale heterogeneous rock that contains both the influences of macro-heterogeneities, e.g., distributed joints, and meso-heterogeneities, e.g., randomly distributed inclusions. Second, the development of pore pressure and stress path varied at the injection point, on the fracture path and on a joint. Finally, both the macro- and meso- heterogeneities influenced the propagation of multiple hydraulic fractures with joints significantly influenced the propagation path of the fractures, and increased injection number Np enhanced the height of the equivalent fracture zone when Np<5.

TIPS: Transaction Inclusion Protocol With Signaling in DAG-Based Blockchain

Directed Acyclic Graph (DAG) is a popular approach to achieve scalability of blockchain networks. Due to its high efficiency in data communication and great scalability, DAG has been widely adopted in many applications such as Internet of Things (IoT) and Decentralized Finance (DeFi). DAG-based blockchain, nevertheless, faces the key challenge of transaction inclusion collision due to the high concurrency and the network delay. Particularly, the transaction inclusion collision in DAG-based blockchain leads to the revenue and throughput dilemmas, which would greatly degrade the system performance. In this paper, we propose “TIPS”, the Transaction Inclusion Protocol with Signaling, which broadcasts a signal indicating the transactions in the block. We show that with the prompt broadcast of a signal, TIPS substantially reduces the transaction collision and thus resolves these dilemmas. Moreover, we show that TIPS can defend against both the denial-of-service and the delay-of-service attacks. We also conduct intensive experiments to demonstrate the superior performance of the proposed protocol.

Transient Evolution of Nonmetallic Inclusions in a Si–Mn‐Killed Stainless Steel with Cerium Addition

Laboratory experiments are performed to study the transient evolution of inclusions in Si–Mn‐killed stainless steels with additions of 40, 100, and 400 ppm cerium. With the increase of the cerium content in the molten steel, the evolution path of inclusions is Al2O3–SiO2–MnO–CaO → Ce2O3–Al2O3–SiO2–MnO–CaO → Ce2O3 → Ce2O3–CeS. The addition of 40 ppm cerium gradually increases the Ce2O3 content in liquid oxide inclusions. After the addition of 100 ppm cerium, inclusions first evolve to Ce2O3–Al2O3–SiO2–CaO–CeS, then to Ce2O3. The CeS is generated as a transient product then disappears. After the addition of 400 ppm cerium, liquid Al2O3–SiO2–MnO–CaO inclusions are modified to solid Ce2O3–CeS ones. The addition of 40 ppm cerium into the steel lowers the size from 1.74 to 1.53 μm. After the addition of 100 and 400 ppm cerium into the steel, the size of inclusions immediately decreases due to the formation of small Ce2O3–CeS inclusions and then increases owing to the collision of solid inclusions. A higher cerium content in the steel promotes the collision of Ce‐rich inclusions.

Liquid Inclusion Collision and Agglomeration in Calcium-Treated Aluminum-Killed Steel

This work addresses conflicting results in the literature regarding liquid inclusion agglomeration. To assess whether liquid calcium aluminates do agglomerate in liquid steel, laboratory experiments were performed: melting electrolytic iron, deoxidizing the melt with aluminum and subsequently calcium treating the deoxidation products (alumina and magnesia-alumina spinel inclusions). Under laboratory conditions, solid spinels and alumina inclusions were successfully modified, producing a new population of much smaller calcium aluminate inclusions. The new population of inclusions forms because the presence of calcium in the liquid steel destabilizes alumina and MgO-alumina inclusions, which then dissolve into the melt. The liquid inclusions exhibited a weak but statistically significant tendency to agglomerate. Laboratory results were assessed in the light of different collision mechanisms. Agglomeration mainly occurs by Stokes and laminar fluid flow collision when no external stirring is imposed. Monte Carlo simulations of collisions agree reasonably well with experimental results. For industrial conditions, where the liquid steel is agitated by argon bubbling and/or electromagnetic stirring, turbulent collisions dominate.

Application of Tanks-in-Series Model to Characterize Non-Ideal Flow Regimes in Continuous Casting Tundish

This study describes a new tanks-in-series model for analyzing non-ideal flow regimes in a single-strand tundish. The tundish was divided into two interconnected tanks, namely an inlet tank and an outlet tank. A water model experiment was carried out to separately measure the residence-time distribution (RTD) of the two tanks. Drift beads were adopted in the water model experiment to simulate the non-metallic inclusions in molten steel. Dead volume fraction was evaluated by analyzing measured RTD curves. The ratio between mixed flow volume and plug flow volume was proposed as a new criterion to evaluate the inclusion removal. In the inlet tank, a higher mixed flow fraction was preferred to effectively release turbulent kinetic energy and enhance inclusion collision growth. In the outlet tank, a higher plug flow fraction was preferred to facilitate inclusion removal by flotation. The optimal positions of the weir were recommended based on the RTD analysis and the inclusion removal from the results of water model experiments. A theoretical equation was derived based on the tanks-in-series model, providing a good fitting function to analyze the experimental data. The confirmation test was performed by applying computational fluid dynamics simulations of liquid steel flow in the real tundish.

In-situ observation of ancient co-fusion steelmaking process based on HT-CLSM

Observing and analyzing the microstructure of zone samples had been an essential concept in the study of co-fusion steelmaking. High-temperature confocal laser scanning microscope (HT-CLSM) provided a new method in the in-situ observation and real-time analysis of the co-fusion steelmaking process. In this research, a series of experiments had been designed based on Shen Kuo’s The Dream Pool Essays (a famous ancient Chinese literature) and carried out by HT-CLSM. The results showed that a new interface was formed with the phase transition during the heating process, which had an essential influence on promoting the carbon diffusion rate in co-fusion steelmaking. The cast iron zone occurred in mushy solidification because of decarbonization. There were collision, aggregation, and other behaviors of inclusions in the cast iron zone and they moved towards the boundary, which led to the purity of the matrix and the aggregation of a large number of inclusions at the boundary.

Effects of Multiple-Hole Baffle Arrangements on Flow Fields in a Five-Strand Asymmetric Tundish.

This paper reports on the re-engineering of standard five-strand tundish designs into a five-strand asymmetric tundish, which resulted in a non-uniform rate and bias for each strand. We sought to improve the casting conditions by optimizing the liquid steel flow-field in the tundish. Both a water modelling experiment and a numerical simulation were performed to analyze the flow-field according to various diversion hole diameters and injection angles. The results showed that the average residence time decreased as the diameter of the diversion holes increased. As the injection angle was increased, the average residence time initially decreased and then increased. The liquid steel from the ladle shroud rapidly extended to the #2 and #3 strands in the original tundish, which reduced the likelihood of inclusion collision and coalescence.

Modelling of non-metallic inclusions in steel

ABSTRACTIn the current paper, extensive studies of the current authors on the modelling of non-metallic inclusions were summarised. Kinetic studies included the nucleation, collision and agglomeration of inclusions, the interaction between inclusion and bubble in the molten steel, the motion, collision, and removal of inclusions in the molten steel during refining and continuous casting and the entrapment of inclusions in a continuous casting slab strand. Thermodynamic studies included the deoxidation of steel and precise calcium treatment of Al-killed steels. The variation in the composition of inclusions during heating treatment of stainless steels was summarised. The studies ranged from nanoscale of molecules to sub-mili meter scale of inclusions within a meter scale metallurgical vessels, over 10 order in size, and clarified mechanisms for the generation, growth, motion and removal of inclusions in steel.

Quasi-Symmetric Transfer Behavior in an Asymmetric Two-Strand Tundish with Different Turbulence Inhibitor

The task of the tundish is to supply and distribute the molten steel with the similar temperature and the similar inclusion mass concentration to the continuous casting mold. But it is difficult for the asymmetric tundish to accomplish this task. Thus, the scheme about the asymmetric turbulence inhibitor and the baffle wall with guided holes is proposed to optimize the tundish. In order to have a deep insight into the metallurgical behavior in the asymmetric tundish, numerical simulation is applied to describe the fluid flow, the heat transfer, RTD (residence time distribution) curve, and inclusion collision aggregation behavior. Numerical results show that the predicted temperature and inclusion concentration agree with the industrial experimental data. In the asymmetric two-strand tundish, the asymmetric turbulence inhibitor and the baffle wall with guided holes can extend the mean residence time at the left outlet, reduce the temperature difference between the two outlets, and prompt the inclusion removal rate at the left outlet.

Formation of Multi-Type Inclusions during the Cooling and Solidification of Steel: A Trend Model

This paper presents a trend model of the competitive formation of multi-type inclusions during the cooling and solidification of steel. The model is able to predict the evolution of various inclusions, including their type, composition and size distribution. In the calculations, the thermodynamic library, ChemApp, was applied to perform a thermodynamic equilibrium calculation. Homogeneous nucleation, diffusion-controlled growth and dissolution were employed to simulate the size distribution evolution. At the same time, the collision of inclusions of the same type were considered in a simplified way. The inclusion stabilities were validated by laboratory experiments, which offered a strong basis for the simulations. Using the proposed model, the influence of alloying temperature and oxygen content on the formation of multi-type inclusions was investigated. The results indicated that decreasing the alloying temperature resulted in a higher number density and finer size of different oxides. The oxygen content affected the formation of various oxides in different ways. The predictions, based on the mechanism of competitive nucleation and growth, are discussed and explained. It is believed that the calculations deepen the understanding of the competitive formation of multi-type inclusions. The predicted trends provide a valuable reference for inclusion control and experiment design.

Collosion and Absorption Behaviors of Inclusions on Refractory

AbstractThe paper is dedicated to analysis the inclusion behavior in steel using theoretical calculation and simulation of water. The aim is to establish collision and absorption model of inclusions on refractory. The article discusses the variation of critical stay speed and critical shear with the radius of inclusions in the process of colliding, rebounding and absorbing. The results show the critical stay speed and critical shear of alumina respectively surpasses 1 cm·s−1and 1 N·m−2, while titanium dioxide separately exceeds 4 cm·s−1and 10 N·m−2for the inclusions that radius is less than 2.5 μm. If the inclusions occur rebound after colliding, the inclusions that radius is less than 7 μm will still be absorbed by the surface, while the inclusions that radius is more than 10 μm can easily reenter the steel. The model coincides with the water simulation results and it is of good adaptability.

Agglomeration of Non-metallic Inclusions at the Steel/Ar Interface: Model Application

Inclusion agglomeration is an important element in several industrial problems during steelmaking, such as nozzle clogging. In parallel work by the authors, a revised Kralchevsky-Paunov model has been established and the performance of this model has been validated against the experimental data from in-situ observations using confocal laser scanning microscopy. In this work, the revised model has been applied to quantitatively evaluate the attractive capillary force for the agglomeration of various inclusions at the interface between Ar and liquid iron/steel. A parametric study of the effects on the capillary force of the inclusion density, contact angle between the inclusion and liquid steel, and the surface tension of the liquid metal are quantitatively investigated. The results show that inclusion density and contact angle have a more marked effect on the capillary force than surface tension of liquid metal. Moreover, the inclusion agglomeration behavior in the liquid iron/steel matrix is discussed. The coagulation coefficient of various inclusions is calculated. Both the calculation results of the attractive capillary force of inclusions at the interface between Ar and liquid iron/steel and coagulation coefficient of inclusions in the liquid iron/steel matrix can offer a close agreement; moreover, the order of magnitude of inclusion agglomeration tendency is suggested. By using the coagulation coefficient, the inclusion collision volume and collision rate are calculated and the effects of inclusion composition, size, and number density are investigated. The evaluation results show that the tendency for affecting inclusion collision is inclusion number density > inclusion size > inclusion composition.