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This study provides a thorough analysis of the fatigue resistance of two low-alloy ultrahigh-strength steels (UHSSs): Steel A (fully martensitic) and Steel B (martensitic–bainitic). The investigation focused on the fatigue behaviour, damage mechanisms, and failure modes across different microstructures. Fatigue strength was determined through fully reversed tension–compression stress-controlled fatigue tests. Microstructural evolution, fracture surface characteristics, and crack-initiation mechanisms were investigated using laser scanning confocal microscopy and scanning electron microscopy. Microindentation hardness (HIT) tests were conducted to examine the cyclic hardening and softening of the steels. The experimental results revealed that Steel A exhibited superior fatigue resistance compared to Steel B, with fatigue limits of 550 and 500 MPa, respectively. Fracture surface analysis identified non-metallic inclusions (NMIs) comprising the complex MnO-SiO2 as critical sites for crack initiation during cyclic loading in both steels. The HIT results after fatigue indicated significant cyclic softening for Steel A, with HIT values decreasing from 7.7 ± 0.36 to 5.66 ± 0.26 GPa. In contrast, Steel B exhibited slight cyclic hardening, with HIT values increasing from 5.24 ± 0.23 to 5.41 ± 0.31 GPa. Furthermore, the martensitic steel demonstrated superior yield and tensile strengths of 1145 and 1870 MPa, respectively. Analysis of the fatigue behaviour revealed the superior fatigue resistance of martensitic steel. The complex morphology and shape of the NMIs, examined using the 3D microstructure characterisation technique, demonstrated their role as stress concentrators, leading to localised plastic deformation and crack initiation. [ABSTRACT FROM AUTHOR]

One of the main factors determining the final properties of metal products is the quantity, morphology and distribution of non‑metallic inclusions in steel. The article deals with the issues related to the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, in order to improve the quality of the products. During the experimental work on the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, second grade calcium carbide according to GOST 1460–81 was used. To determine the contamination of steel with non‑metallic inclusions, sampling was carried out from hot‑rolled products obtained from continuously cast billets. According to the results, it was found that the improvement of melt deoxidation in melts using calcium carbide can be achieved by increasing its consumption. In turn, the use of calcium carbide for deoxidation of the melt upon its release from the electric arc furnace into the ladle, instead of secondary aluminum ingots of grade AB87 according to GOST 295–98, helps to reduce the contamination of steel with non‑metallic inclusions.

The study focuses on the effect of rare earth elements (REM) in mischmetal on the morphology and chemical composition of non-metallic inclusions in pre-oxidised steel. Calculations were carried out using the WYK_STAL computer program according to two calculation models, considering/ignoring the sulphur partition coefficient at the liquid steel-liquid slag interfacial boundary. It was found that the chemical composition of the resulting precipitates is a consequence of the order in which deoxidising additives were admixed. Simulations confirmed the presence of Ce oxides and sulphides. This was also confirmed by the analysis of samples taken from the steel ingot after laboratory melting. Non-metallic inclusions Ce2O3 and CeS, and the complex of precipitates: La2O3-Ce2O3 was also identified in the steel. Introduction of mischmetal in the final stage refining is the most effective method. Therefore, the oxygen content is reduced below 0.001%, and the sulphfur content can be reduced to 0.004%.

Open-cell ceramic foams are widely used as filters for the purification of molten metals due to their high permeability and high efficiency for capturing non-metallic inclusions. With the consideration of manufacture and filtration behaviour, most filters are produced by replica methods. The intrinsic multiscale porous structure requires the ceramic foams to have sufficient strength. As a consequence, different processing approaches, material compositions and characterizations are investigated. Meanwhile, to further enhance the filtration performance, the functionalization of ceramic foam filters is often conducted with surface coating. This review summarizes the processing and characteristics of ceramic foam filters (CFFs), the nature and formation of non-metallic inclusions (NMIs), the filtration mechanism and applications of CFFs. The characterization of mechanical and filtration performance, as well as the corresponding strengthening and functionalization methods are also presented.

Improving the competitiveness of steel companies is linked to sustainable, quality-compliant steel production. Therefore, new steel production technologies contributing to increased cleanliness of steel are continuously being developed and optimized. One way to achieve a high steel quality is to use electro slag remelting (ESR) technology. In this paper, the principle of ESR technology and the importance of fused slags for optimizing the process are outlined. The aim of this work was to analyze the main thermophysical properties of steel and fused slags used in the ESR process. Determination of the properties of steel and slags was performed using the FactSage calculation software, which involved the calculation of the liquid and solid temperature of steel and slags, the calculation and construction of quaternary diagrams, and the calculation of viscosity. The resulting quaternary diagrams revealed the substantial influence of chemical composition on melting temperatures of slags. In order to validate the acquired results, a CrNiMoV-type steel was subjected to investigation of its metallographic cleanliness and evaluation of its mechanical properties; the ESR process was shown to significantly improve the cleanliness of the steel and improve the mechanical properties of the steel compared to its cleanliness and quality when produced via vacuum degassing (VD) technology. During the ESR process, the average size of non-metallic inclusions was reduced from 20 μm to 10 μm, and the maximum size of non-metallic inclusions was reduced from 50 μm to 28 μm. The mechanical properties of the steel produced using ESR technology were impacted as follows: the ductility increased by 10%, contraction increased by 18%, notched toughness at 20 °C increased by 46%, and at −40 °C (respectively −50 °C) it increased by 30%. [ABSTRACT FROM AUTHOR]

This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic–pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality. [ABSTRACT FROM AUTHOR]

The research results presented in the article constitute the next stage of a planned series of experiments on the process of refining steel from a dispersive non-metallic phase by its filtration method. The paper presents the results of experiments carried out using an innovative design of multi-hole ceramic filters, the filter holes of which have an elliptical shape. Analyses of the macro and microstructure and purity of the steel before and after the filtration process reflect the course of the research and confirm that this can be an effective and cheap method of its refining from non-metallic inclusions. The results presented are the first of their kind in the world and confirm that the shape of the filter holes of multi-hole ceramic filters may have a significant impact on the efficiency of the steel filtration process. The non-metallic phase identified at the ceramic filter-steel interface corresponds to the reaction products of the deoxidation of aluminum steel. [ABSTRACT FROM AUTHOR]

The effect of cooling rate and Nb addition on the phase transformation, microstructures, and mechanical properties of thermomechanically controlled hot-rolled low-carbon CrNiMnMoB ultrahigh-strength steel were studied. The aspects impeding Nb's benefits on hardenability, phase transformation, and mechanical properties were investigated. The hot rolling process was simulated, and a continuous cooling transformation diagram was constructed for the studied steels. Microstructures were analysed using laser scanning confocal microscopy and field emission scanning electron microscopy, with the latter also used for in-depth investigations of the non-metallic inclusions. Transmission electron microscopy was employed to investigate the precipitate characteristics. The concentrations of Nb in the solution and precipitates were quantified for the martensitic and granular bainitic structures. The effect of Nb in solution on phase transformation and strengthening is diminished, and the hardness is reduced by Nb precipitation at an early processing stage. Decreasing the cooling rate promotes the formation of granular bainitic structures rather than martensite. After being subjected to hot rolling followed by water quenching and air cooling, the microstructures are autotempered martensite and fully granular bainite, respectively. Various non-metallic inclusions, including Al2O3, MnS, and Al2O3–MnS, MnS·BN, Al2O3·BN and MnS·Al2O3·BN were observed. The number density and area fraction of non-metallic inclusions in the Nb-containing steel and the air-cooled samples are higher than those observed in the Nb-free and water-quenched samples. Adding 0.04 wt% of Nb slightly increased the strength, but the toughness properties dropped, mainly due to the higher number density and area fraction of non-metallic inclusions and primary large precipitates.

This paper presents an analysis of non-metallic inclusions occurring in high-silicon steels containing about 3% Si of terms of their type, volume fraction and morphology. The inclusions were divided into 3 main groups: oxides, sulfides, nitrides which together can also form complex. The work was based on numerous metallographic observations in two sections (longitudinal and transverse to the rolling direction). The study was performed on three casts differing in chemical composition. The analyzed casts were characterized by a different content of non-metallic inclusions, which can be associated with slight differences in chemical composition. The analyzed results showed that the most common inclusions were oxides and nitrides. Sulfides occurred sporadically.

The Gleeble® simulator 3800 has been used to study the hot deformation behavior of EN25B steel in the presence of inclusions. The experimental flow stress values are analyzed to generate the processing map, which identified the safe deformation zone at two true strain levels with maximum of 50% deformation. At a comparatively lower true strain of 0.4, the safe zone locates in the high-temperature (1050 to 1150 °C) and high-strain-rate regime (2.5 to10 s−1). At higher strain (0.69), the safe zone moves to further right to a higher-temperature zone (1070-1150 °C) but extends further to lower strain rates (1.25 to 10 s−1). The amount of dynamically recrystallized grains was estimated under various deformation conditions, and it decreased with a decrease in temperature, irrespective of strain rates. The investigation of non-metallic inclusions (NMIs) was conducted via electrolytic extraction, followed by SEM and XCT examination. Inclusion size estimated by XCT analysis of electrolytically extracted inclusions on paper was found to be more accurate and ~ 50% higher than SEM analysis on the surface of the sample. At high strain rates and temperatures, the outcomes demonstrated the existence of harmless finer inclusions, validating the location of the safe zone. Additionally, a constitutive model for flow stress in steel of grade EN25 has been created. [ABSTRACT FROM AUTHOR]

The research results presented in the article constitute the next stage of a planned series of experiments on the process of refining steel from a dispersive non-metallic phase by its filtration method. The paper presents the results of experiments carried out using an innovative design of multi-hole ceramic filters, the filter holes of which have an elliptical shape. Analyses of the macro and microstructure and purity of the steel before and after the filtration process reflect the course of the research and confirm that this can be an effective and cheap method of its refining from non-metallic inclusions. The results presented are the first of their kind in the world and confirm that the shape of the filter holes of multi-hole ceramic filters may have a significant impact on the efficiency of the steel filtration process. The non-metallic phase identified at the ceramic filter-steel interface corresponds to the reaction products of the deoxidation of aluminum steel.

This study shows how computer vision, a field of artificial intelligence (AI), can be used to gain access to morphological information for a better process understanding and furthermore, how it can be implemented in the evaluation of active tracing experiments. Non-metallic inclusions (NMIs) play a crucial role in determining the chemical and physical properties of the final steel product. The active tracing technique allows for tracking the formation and modification mechanisms of detrimental NMIs throughout the steelmaking process by adding rare earth elements (REEs) to the melt. The interaction of REEs with NMIs results in the formation of traced multiphase particles and, therefore, lead to challenges for accurate evaluation by automated scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). However, obtaining information about the REE distribution in traced NMIs without extensive, time-consuming human effort is not feasible using the existing method. A two-step classification process with AI was established, which included training and testing of two random forest classifiers (RFC). The first RFC achieved for the binary NMI/non-NMI classification an accuracy of 94.8 %. Four different morphology-based classes were considered in the second classification, whereas traced homogeneous NMIs and NMIs with a high La content got classified with a precision exceeding 90 %. However, caution is required in interpreting results for traced heterogeneous NMIs, as they have a higher prediction error of 37.2 %.

This study provides a thorough analysis of the fatigue resistance of two low-alloy ultrahigh-strength steels (UHSSs): Steel A (fully martensitic) and Steel B (martensitic–bainitic). The investigation focused on the fatigue behaviour, damage mechanisms, and failure modes across different microstructures. Fatigue strength was determined through fully reversed tension–compression stress-controlled fatigue tests. Microstructural evolution, fracture surface characteristics, and crack-initiation mechanisms were investigated using laser scanning confocal microscopy and scanning electron microscopy. Microindentation hardness (HIT) tests were conducted to examine the cyclic hardening and softening of the steels. The experimental results revealed that Steel A exhibited superior fatigue resistance compared to Steel B, with fatigue limits of 550 and 500 MPa, respectively. Fracture surface analysis identified non-metallic inclusions (NMIs) comprising the complex MnO-SiO2 as critical sites for crack initiation during cyclic loading in both steels. The HIT results after fatigue indicated significant cyclic softening for Steel A, with HIT values decreasing from 7.7 ± 0.36 to 5.66 ± 0.26 GPa. In contrast, Steel B exhibited slight cyclic hardening, with HIT values increasing from 5.24 ± 0.23 to 5.41 ± 0.31 GPa. Furthermore, the martensitic steel demonstrated superior yield and tensile strengths of 1145 and 1870 MPa, respectively. Analysis of the fatigue behaviour revealed the superior fatigue resistance of martensitic steel. The complex morphology and shape of the NMIs, examined using the 3D microstructure characterisation technique, demonstrated their role as stress concentrators, leading to localised plastic deformation and crack initiation.

In order to raise the hardness and strength of the surface layer of mechanical components and induce favorable residual compressive stresses, case‐hardening procedures have become established in the heat treatment of steel. In this work, a calculation concept for the fatigue strength of components that have been case‐hardened through carburizing heat treatment is being developed. The residual stress and the load stresses in complex‐shaped, carburized materials are determined using a finite element (FE) model. The fatigue limit of the components is derived using probabilistic methods and taking into account hardness gradients, residual stresses, and non‐metallic inclusions. The model is validated with available axial bending fatigue test data and then used to predict the rotating bending fatigue limit of samples with various geometries and heat‐treatment conditions. This work demonstrates the capability of combining probabilistic and FE‐based modeling to represent complex interactions between variables that affect the fatigue of heat‐treated components, such as steel cleanliness, notch shape, case‐hardening depth, or loading conditions. Highlights: Combined FE‐based and probabilistic methods can predict fatigue strength accurately.Interplay of heat‐treatment output, geometry, load, and material is considered.Crack initiation position gets shifted by increased case‐hardness depth.Fatigue strength reduction due to defects in steel depends on load concentration. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of non-metallic inclusions occurring in high-silicon steels containing about 3% Si of terms of their type, volume fraction and morphology. The inclusions were divided into 3 main groups: oxides, sulfides, nitrides which together can also form complex. The work was based on numerous metallographic observations in two sections (longitudinal and transverse to the rolling direction). The study was performed on three casts differing in chemical composition. The analyzed casts were characterized by a different content of non-metallic inclusions, which can be associated with slight differences in chemical composition. The analyzed results showed that the most common inclusions were oxides and nitrides. Sulfides occurred sporadically. [ABSTRACT FROM AUTHOR]

Foreign non‐metallic inclusions can significantly reduce the low‐cycle fatigue (LCF) life of powder metallurgy (PM) superalloy and greatly affect the safety and reliability of aeroengines. In this paper, LCF experiments on PM FGH96 superalloy with and without inclusions were conducted. Effects of inclusions on the fatigue life and damage mechanism of FGH96 alloy are discussed by fractography analysis. Parameters related to inclusion characteristics such as strength–inclusion coefficient are proposed. By introducing characteristic parameters of inclusions, the LCF life prediction models are established based on the Manson–Coffin relationship, which significantly improved the prediction accuracy and reduced the scattering band by a factor of 2. Highlights: By performing strain‐controlled low‐cycle fatigue tests at different strain amplitudes, statistical analyses were carried out to assess the influences of size, location, and type of inclusions on LCF life, with a quantitative relationship established between them.The change law of LCF life of powder metallurgy superalloy under different inclusion conditions is summarized. Effects of inclusions on the LCF life of FGH96 alloy were clarified and applied to the establishment of fatigue life prediction models considering characteristic parameters of non‐metal inclusions.A modified Manson–Coffin life prediction model considering inclusion characteristics is proposed to support the safety and reliability assessment of turbine disks made of PM superalloy FGH96.By introducing characteristic parameters of inclusions, the LCF life prediction models are established based on the Manson–Coffin relationship, which significantly improved the prediction accuracy and reduced the scattering band by a factor of 2. [ABSTRACT FROM AUTHOR]

Since steel cleanness comes to the fore of steel producers worldwide, it is necessary to understand the formation mechanism and modification of non-metallic inclusions (NMIs) in more detail. One central point is the identification of the source of especially interfering NMIs to prevent their evolution in the future. The present study applies two approaches to determine the source of NMIs in Ti-stabilized ultra-low carbon (ULC) steels—the active and the passive tracing. Both approaches are applied to an industrial experiment. The active tracing technique is focused on investigating the clogging layer formation in submerged entry nozzles and, hence, the origin of alumina particles. This method adds rare earth elements (REEs) directly to the melt to mark pre-existing deoxidation products at a certain point of the steelmaking process. The main concern of the passive method, the so-called REE fingerprint, is the determination of the source of mesoscopic NMIs. For the REE fingerprint, the pre-existing concentration of REEs in different potential sources and the investigated NMIs are measured by using an inductively coupled plasma mass spectrometer (ICP-MS). The resulting patterns are compared after normalizing the contents to chondrites, and the NMIs' origins are identified. Concerning the EDS analysis and the resulting patterns from the REE fingerprint, the mold slag and, respectively, the casting powder were the sources of the investigated NMIs. [ABSTRACT FROM AUTHOR]

OJSC “BSW – Management Company of Holding “BMC” produces high‑quality steel used in the automotive, railway, and oil and gas industries. The production of these steel grades involves controlling a range of quality parameters for both continuous cast and hot‑rolled steel billets to ensure the required mechanical, technological, and operational properties of the finished products. The steelmaking process aims to obtain high‑quality steel with the desired microstructure – low levels of harmful impurities and non‑metallic inclusions (hereinafter referred to as NV). This article describes the work and results obtained in the development of the technology for producing hot‑rolled grade 62PP steel, using the example of low‑hardenability carbon steel intended for the production of springs used in vehicle suspension.

This paper presents a theoretical criterion and approach for determining the relationship between the critical hydrogen concentration for hydrogen-induced cracking (HIC) initiation and the type and size of non-metallic inclusions. We used plate-like MnS and sphere-like Al2O3 as representative inclusions for in-depth analyses. Our results indicate that decreasing inclusion size increases the hydrogen concentration required for HIC initiation, particularly in the range of small inclusion sizes. Al2O3 exhibits a higher susceptibility to HIC than MnS. Each type of inclusion has a specific hydrogen concentration below which crack initiation cannot begin. The critical concentration for HIC initiation in the entire steel corresponds to the lowest value among these concentrations. This study provides a quantitative and comprehensive solution to this issue.

This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic–pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality.

We review and analyse the reasons of destabilizing the chemical composition and mechanical characteristics reinforcing low-carbon steels and present ways to solve these problems. As determined, both the instability of the chemical composition and the non-metallic inclusions of an elongated and acute-angled shape, containing an excessive amount of gas and other impurities, reduce the service life of the finished metallurgical product and lead to a deterioration in the quality of the finished product. As established and proven, one of the ways to maximize the chemical-composition stabilization and to improve mechanical characteristics, as well as the quality of the reinforcement, is the steel-melts’ processing with multifunctional-action modifiers. As determined, the St1kp steel, like other low-alloy steels, is a multicomponent system consisting of 17 or more components. Each of the impurities, as well as deoxidizing modifier elements (Al, Ti, Mg), can change significantly the composition of non-metallic inclusions, the main matrix, cementite, grain size, mechanical characteristics, and their stability. As established, after modification, the St1kp-steel grain structure is almost 2 times finer, after which it can be asserted safely that such a material can last longer. As revealed, all mechanical-characteristics’ parameters of the modified metal met the requirements of the State Standards (DSTU) 2770-94 and exceed the serial ones. This is especially important for reinforced concrete structures, since the insufficient level of mechanical characteristics and their instability cannot guarantee the reliability and durability of their operation. As noted, during the solidification of the modified ingot, mainly volumetric crystallization takes place, and not heat-sink-oriented crystallization, as for serial metal. The predominant mechanism of bulk crystallization is one of the main reasons for the stabilization of the chemical composition and the increase in the mechanical-characteristics’ level of steels under the complex influence of alloying components and harmful impurities of steel both serial and modified with multifunctional modifiers of melts. As proved in the work, after modification, the morphology of non-metallic inclusions is significantly improved. As a result, the quality of the finished reinforcement is significantly increased.

In this work, high temperature experiments of high Al molten steel contacting with crucible and slag were performed to investigate the effect of crucible–slag–steel reaction on transient evolution of inclusions in the high Al molten steel. Processing samples were taken for the chemical compositions of steel and also the inclusions have been characterized by using SEM and EDS AZtec. FactSage macros have been applied to simulate the evolution of molten steel composition and inclusions in molten steel during steel-slag reaction and comparing to the experimental results. Due to the steel–crucible–slag reactions especially under the condition of the high Al molten steel, the Ca and Mg transferred from slag and crucible to the molten steel and then subsequently led to the evolution of Mg and Ca-containing inclusions. The Mg inclusions transferred from MgAl2O4 to MgO inclusions while Ca transferred to steel and modified MgAl2O4 at crucible interface to form CaMgAl2O5 phase. The FactSage macros modeling did agree reasonably well with the experimental results.

Duplex stainless steel is a unique material for cast products, the use of which is possible in various fields. With the same chemical composition, melting, casting and heat treatment technology, pitting and crevice corrosion were observed at the interphase boundaries of non-metallic inclusions and the steel matrix. To increase the cleanliness of steel, it is necessary to carefully select the technology for deoxidizing with titanium or aluminum, as the most common deoxidizers, and the technology for modifying with rare earth metals. In this work, a comprehensive analysis of the thermodynamic data in the literature on the behavior of oxides and sulfides in this highly alloyed system under consideration was performed. Based on this analysis, a thermodynamic model was developed to describe their behavior in liquid and solidified duplex stainless steels. The critical concentrations at which the existence of certain phases is possible during the deoxidation of DSS with titanium, aluminum and modification by rare earth metals, including the simultaneous contribution of lanthanum and cerium, was determined. Experimental ingots were produced, the cleanliness of experimental steels was assessed, and the key metric parameters of non-metallic inclusions were described. In steels deoxidized using titanium, clusters of inclusions with a diameter of 84 microns with a volume fraction of 0.066% were formed, the volume fraction of which was decreased to 0.01% with the subsequent addition of aluminum. The clusters completely disappeared when REMs were added. The reason for this behavior of inclusions was interpreted using thermodynamic modeling and explained by the difference in temperature at which specific types of NMIs begin to form. A comparison of experimental and calculated results showed that the proposed model adequately describes the process of formation of non-metallic inclusions in the steel under consideration and can be used for the development of industrial technology. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of EN30B steel in the presence of inclusion has been studied using the Gleeble® simulator 3800. The processing maps are developed to identify the range of parameters (temperature, strain, and strain rate) for a safe deformation zone. Safe deformation zones are identified at various strain levels. The safe zone is found to lie in the high temperatures (1110 to 1150 °C) and high strain rates (6 to 10 s−1) at lower deformation (true strain = 0.4), which subsequently moves to low strain rates (0.1 to 0.8/s) and wide temperature regime (1000 to 1150 °C) at higher strain labels (0.6 to 1.2). With the shear band generation, there is a competition between favorable and unfavorable microstructural evolution, which shifts the safe zone at various strain levels. The evolution of inclusions and cracks at different strain rates and temperatures is examined using SEM and correlated with the processing maps. Cracks were initiated at compound inclusions and propagated in the lower temperatures and higher strain rate regimes, identified as the unstable plastic deformation zone in the processing map. An estimated higher volume fraction of the dynamically recrystallized grains in the safe deformation zone attributed to arresting the cracks. [ABSTRACT FROM AUTHOR]

Super 13Cr steels, which combine high strength and excellent corrosion resistance, are the optimal choice for developing and exploiting complex oil and gas wells, particularly in high-CO2 environments. In this study, we conducted a corrosion assessment of several high-strength steels of the 13Cr type with different alloying systems. We identified the primary parameters responsible for the corrosion resistance of these steels based on our research findings and suggested ways to optimize their chemical composition and select the most economically viable option. We demonstrate the importance of selecting the appropriate alloying system and the impact of non-metallic inclusions (NMIs) on the corrosion properties of the high strength 13Cr material. [ABSTRACT FROM AUTHOR]

The dissolution of Al2O3 non-metallic inclusions in slag containing FeO was investigated in this study. The slag system used in the experiments was a quaternary system of CaO-SiO2-Al2O3-FeO. The composition of the slag was studied by fixing the basicity (CaO/SiO2 ratio) to 1 and varying the FeO content to 10 and 20 wt%. In addition, the experimental temperature was varied to 1550 °C, 1575 °C, and 1600 °C to study the effect of temperature on the Al2O3 dissolution behavior. The experimental equipment used was a single hot thermocouple apparatus. The dissolution rate of Al2O3 particles increased linearly with increasing temperature and FeO content. In addition, the mass transfer activation energy of Al2O3 dissolution in FeO 10 wt% and FeO 20 wt% was calculated through an Arrhenius-type analysis. The obtained mass transfer activation energies were 159 and 189 kJ/mole, respectively. [ABSTRACT FROM AUTHOR]

The non-metallic inclusions in steel mainly come from the deoxidization process of molten steel. Based on the different deoxidization processes of GCr15 bearing steel produced by a domestic steel plant, the single deoxidization curves of Al, Si, and Mn and the compound deoxidization curves of Al-Si and Si-Mn under pure molten iron and GCr15 bearing steel production conditions were calculated with the FactSage 8.1 thermodynamic software. The results show that the deoxidization curves under the two conditions are quite different. At the same time, the Al-Ti deoxidation equilibrium curve under the condition of GCr15 bearing steel was calculated. It was found that when [Ti] < 0.0015% in the steel, the equilibrium deoxidation product was Al2O3, and no titanium oxide was generated. Finally, a thermodynamic calculation and analysis of the effect of rare-earth Ce content on the modification of inclusions in GCr15 bearing steel were carried out. The results showed that when T = 1873 K, the rare-earth Ce treatment of aluminum deoxidized the GCr15 bearing steel; when [Al] = 0.015%, Al2O3 inclusions increased with the increase in [Ce] content, and the evolution path was Al11O18Ce→CeAlO3→Ce2O3. When [Si] = 0.28%, [O] > 50 ppm, and CeCrO3 and [O] 0.012% appeared. CeS inclusions appeared in the steel, and the final equilibrium product was CeS + Ce2O3. When [Ce] < 0.012%, CeS was not produced in the steel, and only Ce2O3 existed. [ABSTRACT FROM AUTHOR]

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.

The hydrogen induced cracking (HIC) resistance of four (4) L80 casing steels, with different nominal compositions and processing conditions, was determined using the NACE TM0284 HIC test. Microstructural and inclusion characterization of each steel was undertaken using optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The morphology (equivalent diameter, aspect ratio and major length) of inclusions over identical analysis regions were measured for each steel. In total, >15,000 inclusions were characterized. Non-linear models correlating inclusion morphology with the measured values of CLR (crack length ratio) and CTR (crack thickness ratio) were developed. The models show that both CLR and CTR are complex functions of the diameter (equivalent) of oxide-based inclusions and the major length of the manganese sulfide (MnS) stringers. The models show that oxides 20 μm exhibited a significant and escalating negative impact on HIC resistance comparable to long (>50 μm) MnS stringers.

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.

In the recent years, the demand for clean steel in critical applications e.g. in construction or transportation industry has increased. In view of the research and developments in the steel production and refinement it seems logical to pursue new approaches on the refractories and to evaluate the existing ones. Within this study zirconia castables stabilized by yttria or magnesia with additions of an alumina or an alumina-magnesia based binder were developed. The influence stabilizer and binder type on the phase evolution of the zirconia castables was investigated. The physical, mechanical and thermomechanical properties were evaluated. Subsequently, the zirconia castables were tested in a steel casting simulator under industry-oriented conditions. Alterations in surface chemistry and morphology were studied via optical light and scanning electron microscopy. Using an automated feature analysis, the solidified steel was investigated regarding the formation of non-metallic inclusions during steel casting experiments to identify their type and frequency.

The fabrication of MgO–C refractories containing MgO–C recyclates is a current approach for saving resources and energy. However, it must be ensured that the steel quality is not adversely affected, particularly with regard to non-metallic inclusions. The present study investigates MgO–C refractories containing different proportions of MgO–C recyclates (up to 83%) in contact with 16MnCr5 steel melt and a slag. A recyclate-free MgO–C material served as a reference. The tests were performed in a steel-casting simulator. By an automated feature analysis of the solidified steel, manganese sulfide and complex alumina-manganese sulfide inclusions were found to be the predominant ones in all steel samples. No negative influence of the recyclate on the inclusion count and the size distribution of the inclusions, the latter being determined for the sum of alumina and alumina-manganese sulfide as well as for the manganese sulfide inclusions, was observed.

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.

One of the main corrosive environments in gas processing is the moisture condensation condition in the vapor phase and variable wetting on the inner surface of equipment. In this case, steel microstructure and non-metallic inclusion content affect formation and development of corrosion defects of carbon and low alloy steels. It is shown that localization of carbon dioxide corrosion within a welded seam of X65 steel proceeds more intensively than within basic metal. Tests conducted in a specially designed stand under variable wetting conditions show that at the surface of 09Mn2Si steel local defects in the form of corrosion pitting occur in places where corrosion products are carried away. The morphology (density, continuity, etc.) of corrosion products (FeCO3) formed affects their potential barrier properties with respect to carbon dioxide corrosion of steel. Use of corrosion inhibitors prevents generation of local damage on steel under the action of media containing CO2. [ABSTRACT FROM AUTHOR]

One of the main corrosive environments in gas processing is the moisture condensation condition in the vapor phase and variable wetting on the inner surface of equipment. In this case, steel microstructure and non-metallic inclusion content affect formation and development of corrosion defects of carbon and low alloy steels. It is shown that localization of carbon dioxide corrosion within a welded seam of X65 steel proceeds more intensively than within basic metal. Tests conducted in a specially designed stand under variable wetting conditions show that at the surface of 09Mn2Si steel local defects in the form of corrosion pitting occur in places where corrosion products are carried away. The morphology (density, continuity, etc.) of corrosion products (FeCO3) formed affects their potential barrier properties with respect to carbon dioxide corrosion of steel. Use of corrosion inhibitors prevents generation of local damage on steel under the action of media containing CO2. [ABSTRACT FROM AUTHOR]

The results presented in this paper are the next planned stage of research on the process of steel refining from dispersoid non-metallic phase by means of its filtration. The acquired results of macro and microstructure anlyzes, as well as steel cleanliness before and after the filtration process, reflect the course of the research and attest that it can be an effective and cheap method of refining it from non-metallic inclusions. Presented results confirm that the slenderness of a filter has a significant impact on the effectiveness of the steel filtration process. Products of deoxidation have been identified on the filtration surface of ceramic filters. [ABSTRACT FROM AUTHOR]

The results presented in this paper are the next planned stage of research on the process of steel refining from dispersoid non-metallic phase by means of its filtration. The acquired results of macro and microstructure anlyzes, as well as steel cleanliness before and after the filtration process, reflect the course of the research and attest that it can be an effective and cheap method of refining it from non-metallic inclusions. Presented results confirm that the slenderness of a filter has a significant impact on the effectiveness of the steel filtration process. Products of deoxidation have been identified on the filtration surface of ceramic filters.

Damage in bearings is closely associated with the presence of microstructural alterations, known as white etching areas (WEAs) and white etching cracks (WECs). One of the main reasons for the creation of these microstructural alterations is the presence of defects in the material, such as non-metallic inclusions. Manganese sulfides and aluminum oxides are widely reported in the literature as the most common types of non-metallic inclusions found in bearing steels. This study classifies 280 non-metallic inclusions in an investigated bearing steel according to several criteria: bonded/debonded with the matrix, size, shape, orientation angle, depth below the raceway surface, and chemical composition. Contrary to the findings in the literature, this investigation reports that the chemical composition of the inclusion (MnS + Al2O3) is of secondary importance when considering factors for damage initiation. The orientation of the microstructural alterations is observed to coincide with the high-stress regions, indicating a relation between the formation of butterfly wings and the white etching crack. In our investigation, butterfly wings typically exhibit a 45-degree pattern originating from the non-metallic inclusions. Conversely, the white etching crack starts from the non-metallic inclusion at a shallower angle in correspondence to the raceway. This can be attributed to the stress state, which corresponds to a region where extensive white etching cracks are formed. In conclusion, the microstructural observations demonstrate that the state of non-metallic inclusion—i.e., whether they are bonded or not to the steel matrix—plays an essential role in initiating rolling contact fatigue damage. [ABSTRACT FROM AUTHOR]

The most economical way to move liquids and gaseous hydrocarbons is by using pipelines. According to several international organizations and oil companies, the use of fossil fuels will continue in the following decades. For this reason, it is important to continue studying different corrosion mechanisms and their origins. One of the mechanisms that provoke small leaks, affecting pipeline hermeticity, is pitting corrosion. It is well-known that non-metallic inclusion dissolution can trigger pit nucleation. As pitting corrosion is recognized to be random in nature, it is also interesting to study the random nature of the inclusions present in API 5L X60 steel. Probability distributions commonly used to describe pitting corrosion characteristics are appropriate for studying inclusion characteristics. The size of inclusions plays a key role in pit nucleation because small inclusions tend to generate more defects, especially when these inclusions are compounds of MnS, and the steel is immersed in a corrosive solution. The results of this research work show that there is a close relationship between the random nature of pitting corrosion and inclusions. [ABSTRACT FROM AUTHOR]

The influence of non-metallic inclusions (NI) on the corrosion resistance of austenitic-martensitic stainless steel deposited in one layer with PP-Nd-30Kh20MH flux-cored wire under AN-26 flux has been studied. It has been established that in the deposited metal there are non-metallic inclusions of complex composition and structure, including those containing calcium and its compounds with other elements, which are classified as corrosion-active, accelerating corrosion. [ABSTRACT FROM AUTHOR]

The behavior of heterophase of the eutectic type inclusions (ETI) under different conditions of plastic deformation of industrial steels is studied. It is established that metal near inclusions damages with the formation of cracks and deformational cavitites caused by their melting. The melting temperatures of different ETI, as well as the temperature intervals for the formation of microdamages of various types during their deformation, were established. The melting of eutectic inclusions at the initial stages of deformation causes a sharp growth of cracks and cavities in steels, which promotes their red brittleness. [ABSTRACT FROM AUTHOR]

Heat-resistant P91 martensitic steel is used to produce high-temperature steam pipelines in (ultra) critical power plants. However, non-metallic inclusions are inevitably produced in the metallurgical process. The type, composition, morphology, quantities, size and distribution of these inclusions have significant influences on the properties of materials. The present work developed an original position statistical distribution analysis method to characterize non-metallic inclusions in P91 steel based on scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). Two samples from P91 steel pipes fabricated by different processes were examined. The non-metallic inclusions in these samples could be divided into spherical oxides, strand-shaped oxides, spherical sulfides, spherical oxygen–sulfur compounds, strip sulfides and other inclusions. The amount, proportional area, particle sizes, original positions and statistical distribution results of non-metallic inclusions in different processed samples were assessed, and the causes and effects of these inclusions were analyzed. This novel method could provide diversified information on inclusions, which is helpful for the improvement of metallurgical processes and service performance evaluations. [ABSTRACT FROM AUTHOR]

Few reports exist on the effect of the basicity of refining slag on inclusions in 15-5PH stainless steel and its removal efficiency. In this study, the effects of various basicities on the formation and removal efficiency of inclusions in molten steel were investigated. To investigate the effect of the chemical makeup of slag on the non-metallic inclusions in liquid steel, laboratory experiments and thermodynamic calculations were conducted on CaO-MgO-SiO2-Al2O3-CaF2 slag with various slag basicities and 15-5PH stainless steel. In the steel samples that had reacted with high-basicity slag samples, the magnesium content and aluminum yield were higher. Thermodynamic findings according to the ion and molecule coexistence theory showed that log ( a SiO 2 3 / a Al 2 O 3 2 ) decreases as slag basicity increases. This increases the Al concentration in liquid steel while decreasing the Si content. Log ( a MgO 3 / a Al 2 O 3 ) also increases, increasing the Mg content of the molten steel. With this, the transformation order of oxide inclusions is Al2O3 → MgAl2O4 → MgO. High-basicity slag increases the attachment of slag to inclusions and generates MgAl2O4 inclusions that are more easily adsorbed by inclusions in molten steel, thereby improving the cleanliness of molten steel. [ABSTRACT FROM AUTHOR]

Non-metallic inclusions (NMIs) in steels have been the focus of various experimental studies due to their detrimental character. While isolated processes, such as agglomeration or dissolution, have been well investigated, holistic in-situ views with high-temperature confocal scanning laser microscopy (HT-CSLM) have been rare. In this work a novel and suitable method is presented to simultaneously observe agglomeration, movement, detachment, and dissolution of non-metallic inclusions by combined the melting of steel and slag with a dual-crucible approach. Therefore, different steel/slag combinations were tested. It is shown that, with transparent that does not become tarnished by the ions stemming from the steel, the steel's surface and non-metallic inclusions are observable. Furthermore, technological limitations are discussed, including restrictions regarding the melting point of steels and certain steel/slag combinations. [ABSTRACT FROM AUTHOR]

A combined filtration system was investigated for the first time in the present work. A reactive filter was immersed in a steel melt containing artificially generated endogenous inclusions. After extracting the filter, the melt was poured through a second filter and into a crucible where it cooled down. The second filter had a pure aluminum oxide flame-sprayed coating, in order to prevent reactions and only remove pre-existing inclusions. It was observed that the immersion of a reactive, coated filter generally resulted in larger inclusions. When no casting was performed, or when the second filter was omitted, smaller remaining inclusions were found. Calcium aluminate based coatings resulted in the creation of new multiphase inclusions (and less alumina). Although these results cannot be directly compared with state-of-the-art industrial filtration procedures, active filtration seems so far the most promising approach to produce steel of improved quality. In addition, filters with a calcium aluminate-based coating might be interesting in the production of steel with tailored inclusions for special applications.

The kinetics of solid-state reactions involving non-metallic inclusions (NMIs) in steel is a topic of growing interest due to the need to understand the effects of heat treatments on NMI composition and stability. In this study, a High Temperature Environmental Scanning Electron Microscope (HT-ESEM) is utilized to conduct in-situ observations of various types of NMIs, including calcium aluminate complex, CaS, MgAl2O4-CaS, MnS, and TiN, in steels at temperatures of 800 °C and 900 °C for different holding times. The observed morphological variations in the NMIs indicate a decrease in the fractions of CaS and MnS, promoting void formation and ferrite–austenite phase transformation. To estimate the NMI reactions with the residual atmosphere in the sample chamber during experiments, HT-ESEM-driven thermodynamic calculations have been performed using FactSage 8.2 software. These calculations provide valuable insights into the interpretation of the experimental data, facilitating a better understanding of the complex NMI reactions in steel.

The article presents the results of studying non-metallic inclusions (NI) after extra-furnace treatment of the 13Cr9Mo2Co1NiVNbNB steel melt to produce large-sized ingots. The objects of the study were laboratory samples (the first batch), and samples obtained after melting in industrial furnace, followed by modification and double vacuuming (the second batch). Previously, using the Fact Sage software, modeling of the NI formation processes was carried out. The data were obtained on the possible NI composition and amount in this steel. The composition, the contamination index, parameters of NI in samples have been studied. It was established that in the samples of the first batch, the main part of the NI consisted of chromium- and manganese-containing oxides, which occupy more than 94% of the total area of the NI. In the samples of the second batch, the main part of the NI was represented by aluminum containing systems. It was shown that the average size of NI in the samples after extra-furnace treatment differs slightly (5%–12%), however, the contamination index in industrial samples after vacuum treatment and especially after modification and repeated vacuum treatment was reduced by more than 10 times. The results obtained allow to recommend vacuum treatment and complex modification with calcium and boron as measures to prevent the formation of NI and to improve metallurgical quality when smelting large ingots using complex alloy steels.