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Current gear design guidelines and standards have given little or no consideration to the increase in strength that can be achieved by using ultra-clean steels. In order to fully exploit the potential of ultra-clean steels, it is therefore necessary to use higher-quality calculation methods that combine FEM stress calculations with local strength calculations. Therefore, the aim of this paper is to extend the inclusion-based model to allow for the calculation of the tooth root bending strength of gears with different steel cleanliness. For this purpose, a material analysis of 20MnCr5 with three different degrees of cleanliness is carried out and the respective material defect distribution is determined. In order to be able to represent the determined material defect distributions of the different cleanliness grades in the inclusion-based model, the model is extended accordingly, and a sensitivity analysis is carried out on the influence of the material defect distribution functions on the tooth root bending strength calculation. Finally, the model is applied to a pulsator test to verify the applicability of the model. The results of the verification show that the calculation of the mean bending strength of gears in pulsator investigations is generally possible with the extended inclusion-based model. The inclusion-based model thus offers the potential to improve the statistical significance of pulsator test results by supplementing the limited number of practical test points with the virtual test points of the inclusion-based model. [ABSTRACT FROM AUTHOR]

To understand the effect of the interactions between Ce‐treated steel and refractory on steel cleanliness, the high‐temperature reaction behaviors of Ce‐treated Al‐killed steel with different refractories (MgO, Al2O3, MgO⋅Al2O3, and CeO2) are investigated in laboratory at different times (30–90 min), and the inclusions in steel and the total oxygen contents of the steel are also analyzed. The results show that when the MgO refractory contacts with conventional Al‐killed steel grades, MgO‐Al2O3 spinel is generated as the reacted layer at the boundary; while it reacts with Ce‐treated steel, MgO–Al2O3 spinel is also formed, but it further transforms into Ce2O2S and CeAlO3 with time. In the Ce‐treated steel, CeAlO3 is proved as the stable phase; thus, the reacted layer of CeAlO3 can also be detected at the edges of Al2O3, MgO⋅Al2O3, and CeO2 refractories. Ce treatment leads to more serious degradation of refractory, and the thickness of the reacted layers at the steel–refractory boundary decreases with time due to the spalling of the layer, resulting in the formation of many CeAlO3 macroinclusions in steel and the rise of total oxygen contents of the steel. [ABSTRACT FROM AUTHOR]

Non-metallic inclusions are pivotal in shaping steel's mechanical properties, thus necessitating the need to manage them effectively in steel production. Enhancing steel cleanliness is a top priority, driving innovations in inclusion removal and modification techniques. The choice of modifiers for inclusions is a critical aspect of this effort. While conventional calcium alloys are commonly used in the industry, they often yield inconsistent results due to their high reactivity and low recovery rates. To address these challenges, this study explores the use of barium-bearing alloys, specifically calcium barium silicon (CaSiBa), as an alternative inclusion modifier. Barium uniquely lowers calcium's vapour pressure and enhances its solubility in steel, thereby improving calcium recovery and its effectiveness in modifying inclusions. The findings show a substantial enhancement in calcium recovery, resulting in cleaner steel with superior mechanical properties. Using CaSiBa alloy shows promise for improving steel quality, resulting in steel products with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

Non-metallic inclusions are pivotal in shaping steel's fatigue, impact, and tensile properties, highlighting the need to manage them effectively in steel production. Enhancing steel quality is a top priority in the industry, driving innovations in inclusion removal and modification. The choice of deoxidizers and modifiers for inclusions is a crucial aspect of this endeavour. Current industry practice predominantly employs calcium treatment for steel, utilizing various calcium alloys. However, traditional calcium alloys exhibit inconsistent results due to their high reactivity and low recovery rates. To address these issues, this study explores the application of barium-bearing alloys, specifically calcium barium silicon (CaSiBa), as an alternative inclusion modifier. Barium has the unique ability to reduce the vapour pressure of calcium while increasing its solubility in steel, thereby enhancing calcium recovery and its effectiveness in inclusion modification. A comprehensive approach involving trials with CaSiBa cored wire, metallographic and mechanical evaluations was undertaken. The results demonstrated a remarkable improvement in calcium recovery, cleaner steel with better mechanical properties. The findings suggest that the use of CaSiBa cored wire can significantly enhance steel quality, making it a promising advancement in steelmaking technology, leading to higher-quality steel products with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

Herein, the control of steel composition and evolution of inclusions during the electroslag remelting (ESR) of NiCrMoV high‐strength steel are investigated by laboratory experiments and thermodynamic calculations. The effects of slag systems, atmosphere protection, and surface quality of the consumable electrode are discussed. Results show that slag containing 5% TiO2 and 2% SiO2 is beneficial for controlling Ti and Si losses in steel during the ESR. Using argon gas protection reduces the total oxygen (TO) and nitrogen contents in ESR ingots and improves steel cleanliness, while it has little influence on the types of inclusions. The oxide scales on the electrode surface lead to the reoxidation of liquid steel during the ESR. The TO content increases to 113 ppm and Si, Ti, Als, and Mn contents in ESR ingots are considerably reduced. The inclusions are transformed from Al2O3–CaO–TiOx–MgO to MnO–SiO2–Al2O3–TiOx. Thermodynamic calculations reveal that the decrease in temperature promotes the precipitation of Ca2Ti2O5 and Ca2Ti2O6 in inclusions. As the oxygen content from reoxidation increases, the formation of SiO2 and MnO in inclusions in ESR ingots is promoted. Appropriate process parameters are proposed to control the composition and cleanliness of steel during the ESR. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Current gear design guidelines and standards have given little or no consideration to the increase in strength that can be achieved by using ultra-clean steels. In order to fully exploit the potential of ultra-clean steels, it is therefore necessary to use higher-quality calculation methods that combine FEM stress calculations with local strength calculations. Therefore, the aim of this paper is to extend the inclusion-based model to allow for the calculation of the tooth root bending strength of gears with different steel cleanliness. For this purpose, a material analysis of 20MnCr5 with three different degrees of cleanliness is carried out and the respective material defect distribution is determined. In order to be able to represent the determined material defect distributions of the different cleanliness grades in the inclusion-based model, the model is extended accordingly, and a sensitivity analysis is carried out on the influence of the material defect distribution functions on the tooth root bending strength calculation. Finally, the model is applied to a pulsator test to verify the applicability of the model. The results of the verification show that the calculation of the mean bending strength of gears in pulsator investigations is generally possible with the extended inclusion-based model. The inclusion-based model thus offers the potential to improve the statistical significance of pulsator test results by supplementing the limited number of practical test points with the virtual test points of the inclusion-based model.

The deoxidation in Ti containing Al killed IF steels is a vital parameter that directly influences the steel cleanliness. In this study, the evolution of steel compositions and inclusion characteristics during RH refining of IF steels were investigated by industrial trials involving three Al-Ti deoxidation modes, which were adding Ti-Fe 2 min after Al deoxidation in Mode I, adding Al and Ti-Fe simultaneously in Mode II, and adding Ti alloys with two equal batches at 3.2 min and 5 min after Al deoxidation in Mode III. The results showed that nitrogen pickup of several ppm was observed with Ti-Fe alloy addition. Therefore, nitrogen content in alloys should be strictly controlled. The main inclusions were single alumina particles, alumina clusters, alumina cluster with Al-Ti oxides, and Al-Ti complex oxides. Mode III had less amount of Al-Ti oxides compared with Mode I, and Mode II had a much higher proportion of Ti bearing inclusions than Mode I and Mode III at RH end. For Mode I & Mode III, the inclusion removal rate was 0.33–0.35 min−1 before adding Ti, and slowed down to 0.14 min−1 for Mode I and 0.22 min−1 for Mode III after Ti-Fe addition. While for Mode II, the rate was only 0.18 min−1. Mode III was the recommended mode for its excellent steel cleanliness and high Ti yield with slight elongation of RH treating time. [ABSTRACT FROM AUTHOR]

The slag-metal reactions between Si-killed 316L stainless steel and the fluxes rice hush ash (RHA), RHA + CaO–SiO2 (flux A), and RHA + CaO–Al2O3 (flux B) were conducted in an induction furnace at 1773 K to investigate the effects of the various fluxes on the reoxidation behavior of the liquid steel. The total oxygen (T.O) content in the liquid steel increased when the steel reacted with RHA and RHA + A fluxes, whereas T.O decreased when the liquid steel reacted with RHA + B flux. The number density of non-metallic inclusion (NMI) in the steel reacted with RHA, RHA + A, and RHA + B fluxes increases, stays constant, and decreases, respectively. The increase in the number density of NMI is due to the reoxidation of the molten steel caused by the dissociation reaction of SiO2. However, the number density of NMI in the steel decreased since B flux has a higher value of physicochemical factor, i.e., log(ΔC/η), where η is slag viscosity and ΔC represents concentration difference between initial content and saturation limit of target oxide in slag. The reoxidation reaction caused by the presence of SiO2 in the fluxes and inclusion absorption (dissolution) reactions are competitive or coupled each other. Higher SiO2 activity in the fluxes (such as RHA) resulted in easier formation of SiO2-rich inclusions. However, the SiO2 activity in Flux A and Flux B is lower than that in RHA, and the MnO–SiO2 and SiO2 inclusions in the Si-killed steel were reduced by Al to form MnO–SiO2–Al2O3(-Cr2O3) system inclusions in the steels reacted with Flux A and B, respectively.

JSW Steel, Vijayanagar works operates a 44 T, eight-strand billet caster for continuous casting. Such large volume tundish has large differences between the central and the end strands from the shroud which affects the cleanliness and solidification between different strands. With an aim to improve the steel cleanliness in central strands, water modelling studies were carried out in a 0.25-scale perspex water model. Different configurations of dams were studied under steady and unsteady state conditions. The combination of the wedge and V-shaped dam configuration resulted in increasing the mean residence time of the central strand without affecting the flow behaviour of the last strands. Residence time at central strands increased by 15% and does not affect the vortex formation height. It was further validated on a plant scale tundish. Plant trials demonstrated a reduction in inclusion area percentage by 21% confirming the improved steel cleanliness in central strands. [ABSTRACT FROM AUTHOR]

Interactions between inclusion particles and the steel–slag interface directly affect the inclusion removal efficiency and thus influence steel cleanliness. Herein, the three‐phase interactions are resolved using the volume of fluid (VOF) method coupled with a dynamic overset mesh. The simulation is able to capture the instantaneous interface deformation and predict the particle motion driven by capillary force. The model validity is first demonstrated by comparison with analytical results. Then, a parameter study is conducted to examine the most influential factors governing the separation process. The results show that the system's wetting condition and the slag viscosity have a decisive effect on particle behavior at the interface (separation or entrapment). From an energy perspective, a better wetting condition generates more energy sources, and the interfacial energy is efficiently transformed into the particle's kinetic energy within a less viscous environment, thus leading to better separation. Besides, a criterion for predicting particle behavior is developed based on a modified Reynolds number (Reγ, relevant to fluid properties) and a quantity related to particle dynamics (ζ). The current work brings insights into the interfacial phenomenon during inclusion removal, which can be incorporated into large‐scale simulations to estimate the removal efficiency more accurately. [ABSTRACT FROM AUTHOR]

Magnesia-carbon (MgO–C) refractories are used in steelmaking processes as lining materials. We performed lab-scale tests at 1600 °C and a pO2 of 10−15 atm to determine the effect of Al and Si antioxidant level, time and slag composition on the amount and nature of inclusions in the steel and on the corrosion and infiltration of the refractory. In all steel samples, a pick-up of Al, Si and C was observed. For the refractories containing antioxidants, longer holding times seem to increase the number density of inclusions, especially in combination with a slag with lower MgO content. For the given experiments, the beneficial role of antioxidants against slag corrosion was not observed, possibly due to the low pO2, which prevented C oxidation. As both MgAl2O4 and SiC, formed in the refractory, react and dissolve in the slag infiltrating in the refractory, they do not play a protective role.

This article is aimed to study theoretical knowledges related to deep steel desulfurization and their practical application in specific production conditions. The main goal of this study was to verify the efficiency of added CaSi to processed heats in two batches, i.e., first for deep desulfurization at the beginning of the secondary metallurgy and then in a second smaller batch at the end of that process for final modification. At the beginning of the secondary metallurgy process, it was crucial to prepare a suitable chemical composition of ladle slag with advantageous properties for good assimilation of sulfur-based inclusions from desulfurization reactions. Samples were taken of final basic oxygen furnace slag, ladle slag before the deep desulfurization process at the beginning of secondary metallurgy and ladle slag at the end of processing. Detailed cleanliness analyses of steel samples taken from mold during the casting were performed using the Automated Steel Cleanliness Analyses Tool. For better understanding and interpretation of the obtained cleanliness results and their relationship, the following defined parameters were used: ratio of "Ca/Al" oxide inclusions, percentage of "liquid" inclusions and area of CaS inclusions. [ABSTRACT FROM AUTHOR]

The total oxygen content(T. O),non-metallic inclusions and the relationship between them in pipeline steel,gear steel,tire cord steel and Q235 steel,which were taken from industrial products,were systematically investigated by ASPEX automatic scanning electron microscope(SEM),which can scan large area metallographic specimen,and thermodynamic software Thermo-Calc was used to calculate and validate. The obtained results indicate that non-metallic inclusions are greatly influenced by the production process of steel. With the inclusion size increasing,the amount of inclusions in this size range decreases. Both quantity and area of inclusions increase sharply when T. O increases from less than 0.002% to 0.01%. When T. O is lower than 0.002%,it only shows good positive relationship with the area of all inclusions per square mm steel samples. T. O indicates the area of inclusions in steel more accurately than the quantity of inclusions. Large sized inclusions appear accidentally. The experimental results agree very well with thermodynamic calculations and the content of T. O,[S] in steel.

In situ study of the inclusion dissolution behavior in a slag utilizing high-temperature confocal scanning laser microscopy helps to understand the phenomenon of the removal of non-metallic inclusions from liquid steel before the casting process. The current work introduces an image processing procedure to automate and measure the inclusion diameter during its dissolution. Silica and alumina particle dissolution were considered as they appear differently when suspended in the slag (bubble-like transparent and solid-like opaque, respectively). The procedure consists of two parts: (1) morphological isolation and construction of the inclusion, and (2) inclusion diameter calculation. The inclusion diameters could be successfully measured over a series of images and showed good agreement with the manually measured diameters. The image processing procedure has the advantages of significant time saving and standardization compared to manual measurements. [ABSTRACT FROM AUTHOR]

Laboratory experiments were performed using two kinds of heating furnaces to investigate the quantitative effect of ladle filler sands (LFS) on the cleanliness of a bearing steel at the casting start of the first heat and non-first heats of a casting sequence. After the direct addition of LFS into the molten steel, which was the condition of the first heat, inclusions in steel changed from MgO · Al2O3 to Al2O3. As the LFS/steel ratio increased from 0 to 1:600, the number density of inclusions significantly increased from 5.3 #/mm2 to 14.5 #/mm2 and the area fraction of inclusions sharply increased from 7.8 ppm to 60.6 ppm, inducing the sharp increase of T.O to 16.1 ppm. After the reaction between the LFS contained tundish covering powder (TCP) and the molten steel, inclusions in steel were separated into a MgO-Al2O3 system and a CaO-Al2O3(-MgO) system. With the increase of LFS/TCP ratio to 1:12, the average MgO content in inclusions decreased to 19.1 wt% while the Al2O3 content increased to 77.0 wt%, meanwhile, the T.O content increased to 6.0 ppm and the [Al] content decreased to 50 ppm. Based on experimental results and the thermodynamic analysis, the detrimental effect of LFS on the steel cleanliness of non-first heats was much slighter than that of the first heat owing to the use of high-basicity TCP. Accordingly, more efforts should be made to prevent the LFS charging into the molten steel at the casting start of the first heat of a casting sequence during the industrial production. [ABSTRACT FROM AUTHOR]

Non-metallic inclusions, especially large or clustered inclusions, in steel are usually harmful. Thus, the microscopic analysis of test specimens is an important part of the quality control. This steel purity analysis produces a large amount of individual inclusion information for each test specimen. The interpretation of the results is laborious and the comparison of larger product groups practically impossible. The purpose of this study was to develop an easy-to-use tool for automatic interpretation of the SEM analysis to differentiate clustered and large inclusions information from the manifold individual inclusion information. Because of the large variety of the potential users, the tool needs to be applicable for any steel grade and application, both for liquid and final product specimen, to analyse automatically steel specimen inclusions, especially inclusion clusters, based on the INCA Feature program produced data from SEM/EDS. The developed tool can be used to improve the controlling of the steel purity or for automatic production of new inclusion cluster features that can be utilised further in quality prediction models, for example.

The multiphase flows involving steel—slag—air phases in a two‐strand tundish during ladle change are investigated using mathematical modeling. Experimental results from water modeling are used to validate the simulated results. Tundish cover powder (TCP) and steel samples are taken from eight heats in one sequence to evaluate the effect of the multiphase flows during ladle change on the composition of the TCPs and steel cleanliness. Furthermore, the effect of the refilling time on the air entrainment and slag aperture during ladle change is analyzed and discussed. It is found that the strong turbulent flows in the tundish impact zone during ladle change promote the mix of the two‐layer cover powder, which consists of a basic TCP layer at the bottom and a top layer of rice hull balls. It results in a significant change in the composition of the TCPs and gradually deteriorates the steel cleanliness by the slag—steel reaction. Increasing the refilling time can effectively decrease the amount of entrained air and area of slag layer aperture in the tundish bath during ladle change. To reduce the steel reoxidation during ladle change, the refilling time should be larger than 184 s. Moreover, a new TCP is developed instead of the top layer of rice hull balls in industrial production. The use of the new TCP significantly improves the steel cleanliness in the tundish. [ABSTRACT FROM AUTHOR]

During ladle refining process, argon gas is purged into the ladle for stirring the molten steel bath to eliminate thermal and composition gradients and to achieve inclusion flotation. Operating parameters like purging location, porous plug configuration and argon flow rate primarily affect liquid steel refining. The efficiency of ladle processing is often quantified through mixing time. To optimize the mixing time and the associated process parameters for improved bath homogenization and inclusion flotation under different operating conditions, water modeling studies using 0.2 scale perspex model and computational fluid dynamics studies using ANSYS CFX v14.5 have been carried out through fluid profile assessment and mixing time comparison. Comparative study was made between single plug, dual plug and top lance purging configurations. The studies helped in identifying the optimum argon purging rates and configurations under normal operational practices. Under abnormal operating conditions involving purging failure from either of the two porous plugs, usage of a top lance along with the single working porous plug has been investigated and found to improve mixing and inclusion flotation in the ladle equivalent to dual plug operation. The lab scale studies have been validated on plant scale through inclusion mapping and found to be in close agreement. [ABSTRACT FROM AUTHOR]

Abstract: Non-metallic inclusions in molten steel mainly originate from refractory-slag-steel interactions during continuous casting and influence its cleanliness remarkably. The objective of this paper was to apply a new approach of minimising non-metallic inclusions by interaction with a suitable MgO-C-based lining material. With the purpose of investigating the efficiency of MgO-C and MgO-CMA-C to reduce endogenous inclusions, immersion tests were performed in a metal casting simulator at 1650 °C. Investigations of the inclusions were carried out by a special automatic SEM. [ABSTRACT FROM AUTHOR]

The process of vacuum degassing occurs during the secondary refining of special steels. Its main function is to remove undesirable gases. However, during this process, flotation phenomenon and inclusions absorption are reported. The aim of the present work was to study the slag viscosity and vacuum degassing (tank type) capacity in steel cleanliness from an industry perspective. To achieve this objective, slag and steel samples were taken before and after the vacuum stage. The results in steel cleanliness were related to a kinetic stirring parameter (βs) of the vacuum station and to the effect of slag viscosity. The removal of inclusions during the vacuum stage reached 64, 75 and 78% in the diameter ranges of 2.5-5, 5-15 and ≥ 15 µm, respectively. After the degassing process, the composition of non-metallic inclusions seemed to approach the slags' chemical compositions. The stirring process in the vacuum degassing station promotes a significant decrease in the inclusion densities for the 2.5-15 µm diameter range and also in the sulfur content in liquid steel. Regarding the effective viscosities of slags, it was concluded that lower values (0.20 Pa.s) increased slag capacity in inclusion removal, whereas higher values (> 0.40 Pa.s) were detrimental to steel cleanliness.

The aim of the current study is to clarify the influence of steel cleanliness on the fracture during wet wire drawing of high strength high carbon very fine filaments. Methodologies for inclusion identification and for inclusion count were developed. Ninety percent of the fractured filaments were associated with an inclusion which was SiO2, or SiO2-CaO or SiO2-MgO. The fracture of the wires resulted from debonding of the inclusion from the matrix. Inclusion density assessed from total oxygen content in the wire was successfully and reliably obtained. Inclusions exhibited a wide range of sizes but mostly around 6 μm. The inclusion density did not appear as the only parameter that affects the fracture occurrence. An important effect of size and of chemical composition of the inclusions was found. A critical size of inclusions for fracture was observed but it depends on the chemical composition of inclusions. [ABSTRACT FROM AUTHOR]

The cleanliness and defects for cold-rolled steel sheet caused by inclusions are greatly influenced by parameters in the metallurgical processing. Good control of parameters during the processing can lead to a better product. In this paper, data mining was used to explore the influence of parameters on defects in steel sheets. A decision tree model was established and it was found that the oxygen content before deoxidation, the end-point temperature of the converter, and the temperature before deoxidation had a great impact on the defects in the cold-rolled sheet that were caused by inclusions. This finding was confirmed by experiments with infrared absorption, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and automatic inclusion analysis methods. After optimization according to results from the model and experiments, the defect rate caused by the inclusions was reduced from 0.92% to 0.38%. [ABSTRACT FROM AUTHOR]

The work addresses the production of medium-Mn steels with an increased Al content. The special attention is focused on the identification of non-metallic inclusions and their modification using rare earth elements. The conditions of the thermomechanical treatment using the metallurgical Gleeble simulator and the semi-industrial hot rolling line were designed for steels containing 3 and 5% Mn. Hot-working conditions and controlled cooling strategies with the isothermal holding of steel at 400°C were selected. The effect of Mn content on the hot-working behaviour and microstructure of steel was addressed. The force-energetic parameters of hot rolling were determined. The identification of structural constituents was performed using light microscopy and scanning electron microscopy methods. The addition of rare earth elements led to the total modification of non-metallic inclusions, i.e., they replaced Mn and Al forming complex oxysulphides. The Mn content in a range between 3 and 5% does not affect the inclusion type and the hot-working behaviour. In contrast, it was found that Mn has a significant effect on a microstructure.

The aim of this study is to determine the optimal chemical composition of the tundish flux, which can efficiently absorb macro and micro inclusions from 16MnCrS5 case hardening steel. Computation of phase diagram is used as an approach to understand properties and behavior of tundish slags in casting conditions. Thermodynamic computation of steel − slag reactions is performed to find out the capability of different tundish slags to absorb inclusions. Industrial trials are, then, carried out with the slags to verify their functionality, when casting several heats in sequence. Results show that by tailoring tundish slag composition the steel cleanliness can be improved. Basic Ca-Mg-aluminate type slags have potential for wide use, as they can be easily adjusted chemically stable against the steel and have ability to absorb inclusions. The slag optimization is, however, a complex issue depending for example on the steel grade. [ABSTRACT FROM AUTHOR]

A numerical model based on computational fluid dynamics was used to simulate the effect of non-isothermal conditions on melt flows in a multi-strand billet caster tundish. To start with, water was used as the operating fluid in a one-third scale tundish to calculate the fluid flow and temperature fields under isothermal and non-isothermal conditions. The model was then extended to the full-scale tundish with molten steel as the operating liquid in order to simulate the conditions in a real plant. It was observed that using step inputs of 10° and 23° for water and steel cases, respectively, changed the fluid flow patterns significantly, more so at locations far from the inlet, due to stronger buoyancy-driven natural convective flows. The temperature distribution and inclusion trajectories within the tundish were also affected due to the presence of non-isothermal conditions. [ABSTRACT FROM AUTHOR]

A mathematical model was built to simultaneously analyse the effects of non-isothermal conditions and flow-control device on steel quality in a real steelmaking tundish. Liquid steel was used as the operating liquid with a step-input of 23° in a full-scale delta-shaped multi-strand billet caster tundish fitted with a standard impact pad (SIP). The changes in flow pattern and temperature fields of liquid steel in the tundish under isothermal, step-up and step-down conditions were thoroughly studied. Similar to the case of a bare tundish, buoyancy effects were seen to dominate at regions away from the ladle shroud. The presence of SIP modified the flow patterns and resulted into markedly different values of RRI as compared to bare tundish. Finally, the calculated results were qualitatively compared to results obtained from a real steelmaking tundish. [ABSTRACT FROM AUTHOR]

This paper details the study of interstitial aluminium impact on non-metallic inclusion occurrence on the basis of individual samples examination taken during steel production and processing. The aim was to identify and describe the relation between the content of interstitial aluminium in metal volume and the concentration of non-metallic inclusions on AlxOy basis occurring in steel. The identification of the non-metallic inclusions occurring in liquid steel was within this study implemented by the (AES) method based on the atom emission spectrometry evaluating the presence of the respective elements in the metal volume. This method works on a principle of emitted light from the existing source with a high voltage spark. The results of this study indicate a correlation between the interstitial aluminium content and concentrations of non-metallic inclusions on the AlxOy basis.

Production practices of IF (interstitial free) steel grades intended for the most qualitatively demanding automotive applications calls for their continuous optimization. Precise control of steelmaking operation conditions leads to a minimization of clogging issues during their casting, but is also related to surface quality imperfections of finished material. With the aim to study the impact of RH degasser practices on cleanliness of the IF steel grades, the influence of heat chemical reheating was verified. While detailed analyses confirmed overall worse results and a higher presence of specific nonmetallic particles on steel samples collected from such treated heats, the limited reheating practice did not seem detrimental.

A quantitative method for assessing the influence of steel cleanliness on the fatigue life of rolling bearing raceways is presented. The approach systematically accounts for the effect of the highly variable stress state within raceways. Finite element analysis is used to determine the stress state in the bearings. A fracture mechanics model for the safe stress amplitude as a function of inclusion size is employed from Lewis and Tomkins. The size and number of large inclusions in a large volume of steel are estimated by the Generalised Pareto Distribution. These three elements are combined to determine the failure probability of the raceway in an example rolling bearing. A sensitivity analysis to the various microstructural input parameters is conducted. It is found that the size distribution of the larger inclusions is the most important factor in controlling the fatigue resistance of rolling bearings, and that residual stresses must be considered to produce realistic predictions. [ABSTRACT FROM AUTHOR]

Steel cleanliness as measured by nonmetallic inclusion content in steel plays a major role in ajfecting bearing durability. A high-fidelity virtual bearing life test model was developed to predict the impact of inclusions on bearing fatigue life. This model analyzes distributions of inclusion size, shape, orientation, and location, and computes stress alterations to bearing material due to inclusions and the resulting life reduction. Comparisons between model predictions and experimental test results were made, confirming the validity of the model. Parametric studies were conducted to explore the effects of inclusion counts, inclusion size distributions, and the effect of overall bearing size on bearing life. A regression equation was proposed based on simulation results, linking the bearing life reduction factor (LRF) to the accumulative inclusion length within the stressed volume under contact load. [ABSTRACT FROM AUTHOR]

In the current research study, a mathematical model was developed to study the dissipation phenomena inside a new design of ladle shroud and its effects on flow patterns and inclusion removal rate. The New Ladle Shroud performance is evaluated in a conventional slab tundish, and the results are compared to different flow control arrangements. The velocity of the entry jet is decreased and the bulk flow is well controlled, the inclusion removal rate is improved, and compared to those arrangements where turbulence inhibitors are used. [ABSTRACT FROM AUTHOR]

The connection between the cleanliness of 52100 type bearing steels and their reliability has been well documented. Most research over the past 30 years has focused on sensitive compositional control during metallurgical refinement, leading to steels so clean that industrial cleanness standards are no longer suitable for quantifying further improvements. There is less literature, however, detailing the mechanism by which different impurities initiate rolling contact fatigue (RCF). Early work focused on comparing fatigue lives with cleanness ratings, which include a worst field analysis to determine the inclusion content and post-failure analysis to determine damage nucleation sites. The stress concentrations around discontinuities in the steel matrix can now however be visualised using computational modelling techniques. There is now a much clearer picture of how non-metallic inclusions (NMIs) nucleate fatigue damage by causing changes in the subsurface microstructure, including white etching regions in the form of butterflies. Size, morphology, distribution and type of inclusion are important factors for determining their role in RCF and the ability to control these variables could lead to improved performance. The inclusion character is greatly influenced by the steelmaking process, from initial melt through to casting, as well as hot deformation. While the impact of microchemical banding on RCF is not well understood, the effect of microsegregation on the phases that form can be modelled using simple calculations. Hot rolling techniques also influence the steel cleanliness, as NMIs can be plastically deformed or broken up and voids can be introduced around them, thus affecting the interface with the matrix. Understanding the microstructure evolution from materials characterisation and the ability to model the process could establish an optimum degree of rolling reduction. This could greatly aid the production of large bearings, as some manufacturers currently make them from very large ingots to achieve the necessary reduction ratio and therefore required level of performance. [ABSTRACT FROM AUTHOR]

The aim of this work was to analyse the influence of the nozzle structure and parameters on the molten steel flow in beam blank continuous casting. A three-dimensional steady state finite element model was developed to compute the flow field and the meniscus fluctuation in the mould. The volume of fluid model was used to track the free surface evolution at the meniscus. It can be concluded that compared with a through conduit submerged entry nozzle (SEN), a three lateral hole SEN will reduce the impact depth, change greatly the velocity at the free surface and intensify the fluctuation of the free surface. As a whole, the fluid flow in the mould will be improved, which will help to melt the mould powder and improve the absorption of non-metallic inclusions, thus improving steel cleanness. The most rational rake angle for the three lateral hole SEN is 9°. Meanwhile, the SEN immersion depth should be in the range 200-250 mm if the casting speed is about 0·9-1·1 m min-1. [ABSTRACT FROM AUTHOR]

In order to increase the beam blank cleanliness, the aim of this work is to analyse the flow field in the mould of beam blank continuous casting, to find the factors influencing the strand cleanliness and then to optimise the process parameters. A three-dimensional steady finite element model was developed to simulate and analyse the turbulent flow field in the mould. The volume of fluid model was used to track the free surface evolution at the meniscus. The influences of processing parameters, such as casting speed and nozzle parameters, on the molten steel flow in the strand (such as vortex location, liquid steel impact depth, velocity and fluctuation of the liquid steel at free surface) were analysed and the optimum processing parameters determined based on mass calculation. The results of this research project have been applied in actual production, and it has been shown that they are very useful and efficient for improving the steel cleanliness and controlling the surface cracks on the beam blank web. [ABSTRACT FROM AUTHOR]