Inclusion Removal Research Articles

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.

Effect of Refining Slag Composition on the Cleanliness of Oriented Silicon Steel

To improve the cleanliness of oriented silicon steel, industrial experiments are performed under different refining slag composition conditions. The results show that the use of medium‐basicity refining slag (w(CaO)/w(SiO2) = 2.3–2.6, w(CaO)/w(Al2O3) = 2.3–2.6) results in higher steel cleanliness with lower Al2O3 volume fraction, and smaller inclusions. In addition, the thermodynamic equilibrium between the oriented silicon steel slag and the molten steel is investigated at a temperature of 1873 K (1600 °C) to understand the effect of different slag compositions on the oxygen content and Al2O3 absorption capacity. Furthermore, a mathematical model is introduced to describe the behavior of inclusions at the steel–slag interface as well as to predict the removal of oxide inclusions during the slag‐refining process. The experimental and predicted results for inclusion removal after slag refining are in good agreement.

Bubble plume effects on the flotation kinetics of nonmetallic inclusions based on experimental observations

AbstractSteelmaking has shown an increasing concern toward nonmetallic inclusions, leading to new technologies in the secondary metallurgy of steel. Although the typical inclusion removal procedure is by injecting inert gas into the ladle, this vessel does not fulfill all the requirements to accept a porous structure tailored to produce “clean steels.” Consequently, the spotlight has moved to the tundish, the last vessel before solidification, in which gas injection can continuously operate. Therefore, this work focuses on understanding the influence of typical gas flow rates (10–60 NL/min) on the kinetics of inclusion flotation, considering two bubble diameters (0.6 and 1.1 mm). For this purpose, experimental measurements were conducted in a water model, where glass hollow spheres played the role of inclusions, and their concentration was fitted by an exponential decay. In general, injecting bubbles into the system contributed positively to a faster and greater flotation of particles. The smaller bubbles led to a higher maximum efficiency, whereas the larger ones allowed a shorter time scale (i.e., a faster removal), defining a trade‐off to tune the bubble size. Regarding the gas flow rate, the results indicate an optimum range to decrease the time scale, and suggestions for bubble curtains in tundishes are drawn.

Effect of Pouring Techniques and Funnel Structures on Crucible Metallurgy: Physical and Numerical Simulations

In the planar flow casting process of amorphous strips, the flow behavior of molten metal and the inclusion content in the crucible are crucial to the morphology and magnetic properties of the material. This study conducts a comparative analysis of the effects of non-immersed and immersed funnels, as well as various funnel structures, on the fluid flow and inclusion removal efficiency in the crucible by integrating numerical and physical models. The findings reveal that for the same pouring flow rate, the diameter of the liquid column in non-immersed pouring conditions is smaller than that of the funnel outlet, leading to a faster injection flow velocity. As a result, the melt in the crucible is subjected to severe impacts, accompanied by an increased possibility of slag entrapment. Conversely, immersed pouring substantially reduces the velocity of the molten metal at the funnel outlet, thereby extending the residence time in the crucible and diminishing the volume of the dead zone. Additionally, the molten metal backflows due to the negative pressure formed in the inner chamber of the funnel. The design of a trumpet-shaped funnel increases the effective volume while reducing the height of the backflow fluid, consequently reducing the velocity of the molten metal at the funnel outlet and prolonging the residence time. Compared to the conventional pouring process with the non-immersed funnel, the outlet velocity is reduced from 1.1 m/s to 0.12 m/s by adopting the immersed funnel with an inverted trapezoidal trumpet structure. This reduction results in a stable flow state, a 9.69% reduction in the dead zone volume fraction, and a 22.96% increase in average inclusion removal efficiency. These improvements demonstrate that a crucible funnel with a well-designed structure and the implementation of an immersion process can significantly improve the metallurgical effects in the planar flow casting process.

Removal and distribution behaviors of inclusion particles in the steel melt under different rotation modes during continuous casting

This work investigated the removal and distribution behaviors of non-metallic inclusion particles caused by the flow of molten steel under two rotational modes, i.e. from edge to center (E-C) and from center to edge (C-E). Three-dimensional mathematical models discovering the relation between fluid flow, temperature distribution, solidified shell growth of large round bloom, and the movement of inclusions were established to investigate the mechanism of the differences. The obtained results show that under the C-E rotational mode, the removal rate of inclusions is 7 times and the highest local agglomeration number density of inclusions is reduced by 38.4 % compared to the E-C rotational mode. The current work proposes that the C-E rotating flow of molten steel can effectively raise the removal and uniform distribution of inclusions, thereby providing a new strategy for effective control of inclusion during the continuous casting process utilizing the novel electromagnetic metallurgy.

Effect of Ferrosilicon Deoxidation on the Evolution and Removal of Oxide Inclusions in 55SiCr Spring Steel

Effect of Ferrosilicon Deoxidation on the Evolution and Removal of Oxide Inclusions in 55SiCr Spring Steel

Numerical Investigation on Transient Flow and Inclusion Removal Behavior in Tundish During Ladle Change Process

The removal of inclusion particles is an important function of tundish metallurgy. During ladle change, the liquid level fluctuation around the ladle shroud is severe, which may affect the effectiveness of inclusion removal. In the present study, the fluid flow characteristics and inclusion‐removal behavior in the tundish during ladle change are investigated by numerical simulation method. And the effectiveness of flow control devices on the flow characteristics of molten steel is evaluated. It is found that the escape rate of inclusion particles during ladle change is ordered as emptying process < steady process < filling process. The proper combination of weir, dam, and turbulence inhibitor can optimize the conditions for the floating and removal of inclusion particles to the greatest extent. In the tundish with weir and dam, the escape rates of inclusion particles with sizes of 10, 50, and 100 μm throughout the entire ladle change period are respectively reduced by 9.8%, 1.6%, and 1.4%, compared to not using flow control devices. With a combination of weir, dam, and turbulence inhibitor, the escape rates of the three types of inclusion particles are reduced by 24.7%, 9.9%, and 1.2%, respectively.

International Benchmark for Total Metabolic Tumor Volume Measurement in Baseline 18F-FDG PET/CT of Lymphoma Patients: A Milestone Toward Clinical Implementation.

Total metabolic tumor volume (TMTV) is prognostic in lymphoma. However, cutoff values for risk stratification vary markedly, according to the tumor delineation method used. We aimed to create a standardized TMTV benchmark datasetallowing TMTV to be tested and applied as a reproducible biomarker. Methods: Sixty baseline 18F-FDG PET/CT scans were identified with a range of disease distributions (20 follicular, 20 Hodgkin, and 20 diffuse large B-cell lymphoma). TMTV was measured by 12 nuclear medicine experts, each analyzing 20 cases split across subtypes, with each case processed by 3-4 readers. LIFEx or ACCURATE software was chosen according to reader preference. Analysis was performed stepwise: TMTV1 with automated preselection of lesions using an SUV of at least 4 and a volume of at least 3 cm3 with single-click removal of physiologic uptake; TMTV2 with additional removal of reactive bone marrow and spleen with single clicks; TMTV3 with manual editing to remove other physiologic uptake, if required; and TMTV4 with optional addition of lesions using mouse clicks with an SUV of at least 4 (no volume threshold). Results: The final TMTV (TMTV4) ranged from 8 to 2,288 cm3, showing excellent agreement among all readers in 87% of cases (52/60) with a difference of less than 10% or less than 10 cm3 In 70% of the cases, TMTV4 equaled TMTV1, requiring no additional reader interaction. Differences in the TMTV4 were exclusively related to reader interpretation of lesion inclusion or physiologic high-uptake region removal, not to the choice of software. For 5 cases, large TMTV differences (>25%) were due to disagreement about inclusion of diffuse splenic uptake. Conclusion: The proposed segmentation method enabled highly reproducible TMTV measurements, with minimal reader interaction in 70% of the patients. The inclusion or exclusion of diffuse splenic uptake requires definition of specific criteria according to lymphoma subtype. The publicly available proposed benchmark allows comparison of study results and could serve as a reference to test improvements using other segmentation approaches.

Study of inclusions-removal and slag-metal dispersion phenomenon in gas-stirred ladle

Abstract The slag-metal interface serves as a crucial locus for both chemical reactions and the adsorption of inclusions during secondary refining. This study first comprehensively reviews the methods of inclusions removal and then establishes a cold-state experiment using a water-oil system to reappear the phenomenon of slag-metal dispersion and inclusion adsorption. The distribution of slag droplets under varying slag volumes is analyzed in terms of the effect of bottom blow rates. Simultaneously, the volumetric fraction of oxygen on the slag-eye surface is analyzed. The result proved that the increase in oil layer thickness or the gas flow rate increase the volume of entrained oil. The dimensionless depth of entrained droplets was positively associated with gas flow rate or oil thickness. The dimensionless depth of “large droplets” and “small droplets” was in the range of 0–25 % and 0–60 %, respectively. Moreover, analysis of the gas composition above the slag-eye in a water-oil system is used to determine the degree of secondary oxidation. The oxygen volume fraction over the surface of the slag-eye decreases with the increase of gas flow rate. The oxygen volume fraction over the surface of the slag-eye is 1.51 % when the gas flow rate is 9 L/min.

Study on inclusion removal in two-strand tundish with gas curtain considering bubble-inclusion attachment

ABSTRACT Application of a gas curtain is one of the main means to improve the cleanliness of liquid steel in tundish. In particular, the bubble-inclusion attachment is one of the important ways to remove inclusions, which cannot be ignored. The bubble size and gas flow are the main parameters of the gas curtain. In this paper, the Euler–Lagrange–Lagrange approach is used to study the three-phase interaction behaviour of liquid steel, bubble, and inclusion. The effects of inclusion size, bubble diameter, and gas flow on inclusion removal rate were studied with normal continuous casting conditions. The calculation results show that the cleanliness of molten steel can be improved by replacing the dam with a gas curtain. In the range of gas flow rate from 1.35 to 2.15 Nm3 h−1, the removal rate of bubble-inclusion attachment and total inclusion removal rate increase with the increase of gas flow. In the range of diameter from 4.5 mm to 6.0 mm with the same gas flow, the total removal rate and bubble-inclusion attachment removal rate increase with the bubble size decrease. The results provide a reference for improving the cleanliness of molten steel by properly increasing the gas flow and reducing the bubble size in industrial operations.

Inclusion Removal Process of Homogeneous CuCr50 Alloy In-Situ Synthesized by Al-Mg Composite Strengthening Reduction Coupling Slagging.

To overcome the problem of Cr2O3 and Al2O3 inclusions in CuCr50 alloy prepared by aluminothermic reduction method, in this paper, a novel methodology for strengthening metal-slag separation through in situ slagging is proposed. CuCr50 alloys were prepared by metallothermic reduction using Al and Al-Mg as reducing agents, and the physical properties of the slag, such as viscosity, density, and surface tension, were adjusted by controlling the proportion of CaO in the slagging agent in the raw material to achieve good separation of the slag-metal. The results show that with the ratio of CaO increased, CaO and MgO were coupled to make slag, which combined with Cr2O3 and Al2O3 to form CaCr2O4, MgCr2O4, and CaAl4O7 in the slag, thus reducing the content of impurities in the alloy. When RCaO/(CaO + Al2O3 + MgO) = 20%, the Cr content ranged from 46.61% to 47.09%, the inclusions accounted for 1.60%, the Cr particle size was refined to 20 µm, the number of Cr spherical crystals accounted for 9.88%, the conductivity reached 14.96 MS/m, and the hardness reached 100.23 HB. After heat treatment, the Cr phase was refined in the alloy, the conductivity increased from 14.96 MS/m to 18.27 MS/m, and the hardness increased from 100.23 HB to 103.1 HB. This method is expected to provide an effective method for the preparation of CuCr50 contact materials.

Numerical and experimental studies on the effects of molten steel viscosity on fluid flow, inclusion motion, and temperature distribution in a tundish

Tundishes are refractory vessels that are used to control the flow of molten steel, promote the removal of inclusions, and increase the homogeneity of temperature and composition during continuous casting processes by optimizing their geometric shape. The flow of molten steel in tundishes is a high-temperature process, and the optimization of the tundish structure is carried out by numerical and physical simulations. In numerical simulations, the viscosity of molten steel is generally set to a constant value; however, in industrial scenarios, the molten steel viscosity is variable with temperature. In the present work, the effects of molten steel viscosity varying with temperature on fluid flow, inclusion motion, and temperature distribution in a tundish were investigated by numerical simulations based on the modification of the top heat flux of the tundish, and the results were further verified by an industrial experiment. The removal rate of inclusions obtained from the industrial experiment was 40.40%. In numerical simulations, the inclusion removal rates were 50.85% and 40.67% when the fluid viscosity was constant and variable, respectively. Hence, when the molten steel viscosity was variable, the numerical simulation result was closer to the experimental one. The industrial experiment revealed that the temperature difference between the edge flow and the middle flow on the tundish liquid surface was 0 K. In numerical simulations, when the top heat fluxes of the tundish were 15 000 and 100 W/m2, the temperature differences on the tundish liquid surface were 5.95 and 0.16 K, respectively.

Physical and Numerical Study on Right Side and Front Side Gas Blowing at Walls in a Single‐Strand Tundish

The compromise between inclusions removal by small bubbles and proper agitation of fluid flow in tundish by gas blown is challenging. The single‐strand tundish without flow control devices (bare tundish) is used to study the effects of side‐wall gas blowing on the flow field. The water model, particle image velocity measurement and computational fluid dynamics simulation are used to study bubble behavior, fluid flow field, and tracer transport. A large horse shoe vortex and a short circuit flow at the bottom are formed in the bare tundish. Gas blowing at the outlet‐side wall of the tundish creates multiple vortices in the right‐side region, with blowing rate and position greatly influencing the surface flow within the tundish. Gas blowing at the front‐side wall creates a large spiral vortex, agitating the fluid in the tundish and improving the flow field. Increasing the blowing rate strengthens the vortex in the right region, but raising the blowing position affects surface flow and creates a counterclockwise flow toward the shroud. In all schemes, gas blowing at a low position on the front‐side wall with a small gas flowrate is the optimized scheme which shows the smallest dead volume and enhances surface flow.

Multiphase modelling of inclusion removal by bubble adhesion in the submerged entry nozzle with centrifugal swirling flow

Multiphase modelling of inclusion removal by bubble adhesion in the submerged entry nozzle with centrifugal swirling flow

Numerical Modeling of Electron Beam Cold Hearth Melting for the Cold Hearth

The electron beam cold hearth melting (EBCHM) process is one of the key processes for titanium alloy production. The unique characteristic of this pyrometallurgy process is the application of the cold hearth, which is responsible for controlling the Low-Density Inclusions (LDIs) and High-Density Inclusions (HDIs) in the melt. As a key process of inclusion removal, the information such as melt residence time in the cold hearth is directly related to the control of metallurgical defects in the ingot, and may also affect the composition distribution of the ingot. In this paper, the details for the physical phenomena, namely the evolution of the pool, the evolution of the flow, and the evolution of the component in the cold hearth during EBCHM are investigated using a modified multi-physical numerical model. The effects of melting temperature and melting speed on these phenomena were investigated. The purpose is to provide more fundamental knowledge and to further enhance the applications of EBCHM for more titanium alloys.

Cleansing the molten steel due to the dispersed in-situ phase induced by the composite sphere burst reaction I. Composite sphere design

In the present investigation, a novel fine inclusion removal technology due to the dispersed in-situ phase induced by composite ball burst reaction was put forward. A composite sphere with this function was designed and the composite sphere burst process at steelmaking temperature was analysed. The results indicate that the compact strength of the composite ball is so high that it will not break up as it intrudes into the molten steel. The composite sphere has a high thermal stability at steelmaking temperature. Usually, the composite sphere burst reaction takes place after it has intruded into the molten steel for a few seconds. The fine bubbles and slag droplets can be released due to the composite sphere burst reaction. Compared with the conventional technology, the bubbles and slag droplets induced by this novel technology are much finer. The size distribution of the bubble and the slag droplet is between 20 and 200 μm. The dispersion of these fine bubbles and slag droplets contributes to collision with inclusion.

Role of Longitudinal Temperature Gradients in Eliminating Interleaving Inclusions in Casting of Monocrystalline Silicon Ingots

Infrared analysis reveals the presence of interwoven inclusions, primarily comprised of silicon nitride and silicon carbide, in the casting process of monocrystalline silicon ingots. This study investigates how the longitudinal temperature gradient affects the removal of inclusions during the casting of monocrystalline silicon ingots through simulations and comparative experiments. Two monocrystalline silicon ingots were cast, each using different longitudinal temperature gradients: one employing smaller gradients and the other conventional gradients. CGSim (Version Basic CGSim 23.1) simulation software was utilized to analyze the melt flow and temperature distribution during the growth process of quasi–monocrystalline silicon ingots. The findings indicate that smaller longitudinal temperature gradients lead to a more robust upward flow of molten silicon at the solid–liquid interface, effectively carrying impurities away from this interface and preventing their inclusion formation. Analysis of experimental photoluminescence and IR results reveals that although inclusions may not be observed, impurities persist but are gradually displaced to the top of the silicon melt through a stable growth process.

Cleansing the molten steel due to the dispersed in situ phase induced by the composite sphere explosion reaction II. Inclusion removal

Industrial trials have been carried out on the base of the former experimental research and the CaCO3 proportion in composite sphere, feeding amount, and composite sphere feeding mode have been investigated. The fine inclusion removal mechanism has been analyzed. The results indicate that feeding composite sphere in RH degasser is a novel process and small inclusion in the molten steel can be removed effectively. CaCO3/CaO ratio in composite sphere has a great effect on the inclusion removal efficiency. More feeding times and a little feeding amount can increase the composite sphere utilization efficiency. Compared with the conventional inclusion removal technology, the number density of the oxide inclusion can be decreased to a lower level and the inclusion size becomes much finer. Using this novel process, T.O. in the as-cast slab can approach to 6 ppm.

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

Effect of titanium on the wettability between Fe-P-Ti alloy and Al2O3 substrate

It is of significance that the wettability between the molten alloy and the Al2O3 affects the inclusion removal, nozzle clogging and refractory erosion. In the present work, the wettability between the Al2O3 substrate and Fe–P–Ti alloys with different Ti content was investigated by using the sessile droplets method. The interfacial characteristics were investigated by scanning electron microscope (SEM). The contact angles between the sintered Al2O3 substrate and Fe–P–Ti alloys with 0, 0.05, 0.10 and 0.15 ​wt% Ti are 100.1°, 97.3°, 94.5° and 90.5°, respectively. The oxidation of [Al] and [Ti] in the molten alloys leads to the formation of the oxides on the droplets. With the increase of Ti content in the Fe–P–Ti alloys, the formed oxides change from Al2O3 to Ti-containing oxides. The reaction between [Ti] and Al2O3 substrate in the interface results in the formation of Ti-containing oxides. The quantity of the interfacial oxides increases with the increase of Ti content in the alloys. As a result, the synergetic effect of the formation of the interfacial products and the oxides on the surface of droplets leads to the decrease of the contact angles between the Al2O3 substrate and Fe–P–Ti alloys due to the increase of Ti content.