Density Of Inclusions Research Articles

Effect of nitrogen content and cerium treatment on the characteristics of inclusions in non-oriented silicon steel

The electric arc furnace (EAF) short process is an important technical path for the future production of green steel, while the higher nitrogen content limits the production of high-grade steel plates, represented by non-oriented silicon steel (NOSS). Under this background, the influence of nitrogen content and cerium treatment on the characteristics of inclusions in NOSS was investigated. Thermodynamic analysis reveals that increasing nitrogen content raises both the initial precipitation temperature and the mass fraction of AlN. NOSS with varying nitrogen contents were smelted in a resistance furnace by top-blowing nitrogen gas (simulating high nitrogen content NOSS produced using EAF), and then cerium treatment was performed on the high nitrogen content NOSS. The inclusions were qualitatively and quantitatively characterised by scanning electron microscope (SEM, Sigma 300). The results indicate that as nitrogen content increases from 0.0013 to 0.0043 wt%, the number density of submicron-sized inclusions, which are more harmful to NOSS properties, increases from 95.43 to 126.64 mm−2. These inclusions are mainly pure MnS and nitrides (AlN and AlN + MnS). After cerium treatment, the modification of sulphides and coarsening of AlN resulted in a decrease in the number density of submicron inclusions. With 0.0086 wt% cerium, the lowest observed number density of submicron-sized inclusions is 14.58 mm−2. The heterogeneous nucleation between AlN and Ce-S was confirmed using the edge-to-edge matching model combined with electron backscattered diffraction.

Influence of inclusions on the pitting behavior of cast duplex stainless steels and patch weld layers

Abstract The relationship between the corrosion resistance of cast duplex stainless steel welded joints and inclusions was investigated by metallographic characterization, electrochemical tests, in-situ tests, scanning electron microscopy (SEM) combined with energy dispersive X-ray spectrometry (EDS) and other methods. The results showed that inclusions were the main sites for pitting corrosion initiation in cast 2205 welded joints, and the MnS portion of the composite inclusions preferentially dissolved to form micro-pits, which triggered pitting corrosion. In addition, the density of inclusions in the heat-affected zone (HAZ) was high and the average size of inclusions was larger, resulting in poorer pitting resistance in the HAZ. And pitting was more likely to occur and subsequently a large pit was developed which ultimately leads to failure.

Formation and evolution of inclusions in Q355B steel deoxidised with silicon and manganese

Q355B is extensively utilised owing to its superior mechanical properties. Nevertheless, the inclusions generated during the deoxidation process with aluminium and the treatment with calcium in steelmaking can profoundly influence these properties. Consequently, this study explores the inclusions formed during the manufacturing process of Q355B utilising silicon–manganese deoxidation alloys in an industrial setting. Furthermore, this research evaluates the deoxidation efficacy of the silicon–manganese alloy and elucidates the fluctuations in oxygen and nitrogen concentrations throughout the entire process. This study further investigates the types, number density, size, morphology and transformation processes of the inclusions generated throughout the Q355B production using silicon–manganese deoxidation alloy; additionally, electrolytic treatment was performed on the cast billets to extract large inclusions. The findings reveal that the deoxidation efficiency of the SiMn alloy is enhanced at relatively low temperatures and with a high manganese-to-silicon ratio. The predominant cause for the increase in total oxygen content in the molten steel during the smelting process is the exposure of the molten steel to secondary oxidation. Manganese–silicon deoxidation adequately fulfils the production requirements for Q355B. Oxide inclusions predominantly comprise Si–Mn-type oxides and their evolved inclusions; during the evolution process, aluminium-containing spinels generate calcium aluminium silicates in conjunction with CaO present in the slag. The number density of inclusions consistently decreases; however, it may subsequently increase due to secondary oxidation and slag entrapment. Throughout the evolution process, inclusions continuously aggregate and grow, resulting in an increasing proportion of large inclusions, while small-sized sulphide inclusions precipitate during the continuous casting process. The analysis of the isothermal ternary phase diagram of the slag system, in conjunction with the electrolytic results of the cast billets, confirms the occurrence of secondary oxidation and slag entrapment during the smelting process. Thermodynamic software calculations elucidate the formation and evolution of composite inclusions, offering critical insights for composition control to mitigate the associated hazards of composite inclusions. Thermodynamic and kinetic calculations of precipitates clarify the solidification conditions and temperature required for the precipitation of MnS, demonstrating that the size of the precipitates is negatively correlated with the cooling rate and positively correlated with the concentration of the strongly segregated element sulphur.

Effect of direct alloying of manganese ore–cored wires on the composition and quality of molten steel

This research involved investigating the effects of different manganese ore addition methods on the quality of molten steel. From the thermodynamic point of view, when carbon powder, an aluminium block, silicon carbide, ferrosilicon and other reducing agents were added during the refining process, the manganese yield substantially increased at 1550 °C; the reduction abilities of the involved reducing agents were in the following order: aluminium block > silicon > silicon carbide > graphite. For top-slag addition, the mass transfer rate of manganese was lesser in molten steel than in slag, indicating that it was the limiting factor. For nonaluminium deoxidation, the inclusions in high-carbon steel were primarily manganese sulfide (MnS), along with a small amount of silicates. Medium-carbon steel contained small amounts of silicon oxide, magnesium oxide and alumina. In aluminium deoxidation, the inclusions in the involved steel were primarily alumina. The average inclusion size for cored-wire alloying with ferrosilicon as the reducing agent was 2.10 μm, with the inclusion density and manganese yield being 0.10/μm 2 and 93.46%, respectively. This alloying process was found to be optimal for direct alloying of manganese ore.

On the role of soft and non-perturbative gluons in collinear parton densities and parton shower event generators

The Parton Branching method offers a Monte Carlo solution to the DGLAP evolution equations by incorporating Sudakov form factors. In this approach, the Sudakov form factor can be divided into perturbative and non-perturbative components, with the non-perturbative part being analytically calculable under specific conditions. We first examine forward evolution and demonstrate that including soft and non-perturbative gluons (through the non-perturbative Sudakov form factor) is essential for the proper cancellation of divergent terms in parton density evolution. This non-perturbative component is also important for Transverse Momentum Dependent (TMD) parton distributions, and within the Parton Branching framework, it is constrained by fits to inclusive collinear parton densities. Additionally, we explore the impact of this non-perturbative Sudakov form factor on backward parton evolution and its effects on parton and hadron spectra originating from initial state showers. Our results show that soft and non-perturbative gluons significantly influence inclusive distributions, such as Drell–Yan transverse momentum spectra. However, we found that soft and non-perturbative gluons have a minimal impact on final state hadron spectra and jets.

Effect of heat input on microstructural evolution and impact toughness in dissimilar weld metals between medium Mn and V-microalloyed steel

High-quality weld metals are a prerequisite for ensuring the integrity of dissimilar steel welded joints. This research investigates the influence of heat input on the inclusion characteristics, variant selection, crystallographic texture, and resultant impact toughness of dissimilar weld metals used in joining heavy-plate medium Mn steel (MMS) and V-microalloyed steel (VMS). Results revealed that inclusion density decreased but its size increased as heat input increased from 10 to 15 and 20 kJ/cm, which alters in the nucleation mechanism of acicular ferrite (AF) from intragranular nucleation to sympathetic nucleation. The percentage of AF initially rose from 81.3 % to 83.2 %, and then declined to 79.1 %. Variant selection also transitioned from random to specific due to the variation in transition temperature and nucleation mechanism. Meanwhile, the fraction of unfavourable crystallographic texture increased from 1.5 % to 22.9 % and 26.1 %. Impact toughness was higher (128 J) at 10 kJ/cm compared to 15 kJ/cm (108 J) and 20 kJ/cm (110 J) owing to its smaller inclusion size and a lower percentage of unfavourable crystallographic texture. These findings offered theoretical guidance for selecting welding parameters in industrial applications for dissimilar welded joints of MMS and VMS.

Microstructure Evolution and Cryogenic Impact Toughness Changes in Ce‐Containing Novel Cryogenic High‐Mn Austenitic Steel Weld Metals under Different Heat Inputs

The Ce‐containing novel cryogenic high‐Mn austenitic steel weld metals under different heat inputs are prepared by submerged‐arc welding to provide a satisfactory welding parameter scheme and further optimize its cryogenic impact toughness. The effect of heat input on microstructure, inclusion, and cryogenic impact toughness of weld metals are investigated via optical, scanning electron microscopy, electron backscatter diffraction, electronic probe microanalyzer, and cryogenic impact test. The results show that the dendrite arm spacing, segregation ratio of Mn, Si, and C elements and average effective grain size of the weld metals gradually increase, and the proportion of high‐angle grain boundaries decrease with the heat input increase from 11.91 to 20.24 kJ cm−1. The type of inclusions of weld metal with different heat inputs are all Ce2O3 and Ce2O2S. The number density of inclusions decreases monotonically from 5976 to 4912 mm−2, while the average size increases from 0.32 to 0.45 μm with the heat input increased. The increase in heat inputs consistently decreases the mean cryogenic impact toughness of weld metals from 123 to 102 J. The higher proportion of high‐angle grain boundaries and finer inclusions at lower heat input play the critical role in improving the cryogenic impact toughness.

Effect of Ca Addition on Inclusions, Microstructures, and Impact Toughness of Coarse‐Grained Heat‐Affected Zone After High‐Heat Input Welding in Mg‐Deoxidized Shipbuilding Steel Plates

Effect of Ca addition on inclusions, microstructures, and impact toughness of coarse‐grained heat‐affected zone (CGHAZ) in Mg‐deoxidized shipbuilding steel plates after high‐heat input welding (HHIW) of 400 kJ cm−1 are investigated. Characteristics of inclusions and their effect on microstructures and impact toughness are elucidated. With the addition of Ca, number density of inclusions decreases from 384 to 273 mm−2, but average size increases from 1.23 to 1.32 μm. Number densities of inclusions such as MgAl2O4, MgAl2O4 + MnS, Mg–Al–Ti–O + MnS, MgO + MnS, and TiN + MnS, which are observed to induce intragranular acicular ferrites (IAFs) formation, decrease from 3.0, 15.3, 18.8, 16.5, and 18.1 to 0.2, 1.2, 4.4, 3.0, and 6.3 mm−2, respectively. Observed Ca‐containing inclusions of diameter over 2.5 μm in Mg–Ca steel cannot serve as the effective nucleation sites for IAFs formation. Contents of IAFs and polygonal ferrites decrease from 73.20% and 19.96% to 54.34% and 5.63%, respectively. Frequency of high‐angle grain boundaries decreases from 70.5% to 51.3%. The CGHAZ fracture morphology changes from ductile fracture to brittle fracture with the area proportion of the fibrous zone decreasing from 56.5% to 0%. Hence, the impact toughness of CGHAZ decreases significantly from 175 to 23 J at −20 °C after HHIW.

Effect of Ti–Mg–Ce Complex Deoxidation on the Inclusions and Mechanical Properties of S355 Steel

Oxide metallurgy technology not only refines the microstructure but also modifies the type, density, and size of inclusions. This study examines the impact of Ti–Mg–Ce composite deoxidation on the inclusions and mechanical properties of S355 steel used for heavy‐duty H‐beams. Compared to base alloy, Ti–Mg–Ce‐added alloy features a higher presence of inclusions such as MgO, TiN (containing Ce), TiOx, and TiS, except for SiO2, Al2O3, MnS, and MnO. Following Ti–Mg–Ce composite deoxidation, the number density of inclusions increases by 16.4%, and the equivalent diameter, length, and width of the inclusions decrease by 41.0%, 41.2%, and 37.9%, respectively. The length of large‐angle grain boundaries in the same area increases by 20%, and the average grain size reduces by 12.5%, resulting in an enhancement of yield strength by 23.6 MPa, tensile strength by 37 MPa, total elongation by 2.1%, and impact energy by 92 J. By employing Ti–Mg–Ce composite deoxidation to optimize inclusions and microstructure, the strength, plasticity, and toughness of the experimental steel are significantly improved.

Study on the effect of rare earth Ce on the modification of sulfide inclusions in U71Mn heavy rail steel

In this paper, the directional modification behavior of rare earth Ce on sulfide inclusions in steel is studied by thermodynamic calculation and experiment methods, and the mechanism of directional modification of rare earth Ce on sulfide inclusions in U71Mn heavy rail steel is proved. The results show that U71Mn heavy rail steel contained more large-sized inclusions and their distribution is more concentrated without the addition of rare earth Ce element. After the addition of rare earth Ce element, the average size of sulfur-containing inclusions in the steel decrease from 5.22 μm to 1.85 μm, and the number density of sulfur-containing inclusions in the steel increase from 83.65 mm−2 to 217.68 mm−2, indicating that the number of sulfur-containing inclusions in the steel increases after the addition of Ce element, and more small-sized sulfur-containing inclusions will form in the steel. The addition of rare earth Ce element can effectively reduce the existence of large-sized inclusions in the steel and modify large-sized inclusions into small-sized inclusions.

Enhancing the Pitting Corrosion Resistance of Fe‐36Ni Invar Alloy via Introducing Mg

The primary objective of this study is to investigate the corrosion resistance of Fe‐36Ni Invar alloys with varying Mg contents in a 3.5 wt% sodium chloride solution. The electrochemical results reveal that the incorporation of Mg amplified the corrosion behavior of Fe‐36Ni Invar alloy. The inclusion compositions undergo a transformation with the increase of Mg content, evolving from MnO–MnS in 0 Mg alloy to MnO–MnS–MgO in 0.0015 Mg alloy, and ultimately to MnS–MgO–MgS in 0.0030 Mg alloy. During the corrosion process, the small‐sized MnS–MgO–MgS inclusions exhibit greater stability compared to the MnO–MnS inclusions, rendering them less susceptible to attack and dissolution. Adding Mg diminishes the size and number density of inclusions, which effectively decreases the susceptibility to pitting initiation. The introduction of Mg refines the microstructure and elevates the fraction of twin boundaries, which also is responsible for the enhancement of corrosion resistance.

Effect of CaO–Al2O3–SiO2–MgO(–CaF2) refining slag system on inclusions in silicon–manganese deoxidized spring steel

In order to make the refined slag match various grades of spring steel, high-temperature equilibrium experiments were conducted in the laboratory to study the effect of CaO–Al2O3–SiO2–MgO refining slag with varying basicity, Al2O3 content, and CaF2 additives on inclusions containing Al (Al2O3) in silicon–manganese-deoxidised steel. The results show that the control effect of low basicity refining slag on inclusions is better than that of high basicity slag. The soluble aluminium increases with the increase of the basicity of steel slag and the Al2O3 content in inclusions is positively correlated with the Al2O3 content in slag. When the relative adsorption capacity of the refined slag is 6 × 10−3, the area density of Al-containing inclusions in steel is at a low level. Low basicity slag with low Al2O3 is good, and it is more suitable for producing high-end spring steel. To produce middle- and low-end spring steel, the refining slag system with a basicity of about 2–2.5, Al2O3, MgO, and CaF2 content is about 10% can be used. Among them, a small amount of CaF2 improves the liquidity of steel liquid, improves its relative adsorption capacity to Al-containing inclusions, and can control the production of Al-containing inclusions in the steel.

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

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

Very high-T hydration in the lower gabbro section of Semail ophiolite, Hydrous components of the lower crust at fast-spreading ridge

Totally fresh black gabbros are observed locally at the very base of the gabbro section in southern Semail ophiolite. Devoid of medium to low-temperature diffuse alteration, the black gabbros are characterized by cloudy plagioclase marked by a high density of hydrothermal inclusions below the optical microscope resolution, evolving into diopside and pargasite crystals ∼10 μm sized. They record hydration at temperature over 900 °C as shown by their major elements composition. Focused Electron Backscattered Electron Diffraction (EBSD) study of the crystalline inclusions, suggests a phase transition from diopside to amphibole, and traces consistent crystallographic relationships of diopside inclusions with their host plagioclase. The detailed geometry of the microcrack system traces a complete fluid path from inter-grain cracking, to plagioclase intra-grain network, possibly thermally-induced. The evidence of solid-state deformation overprinting the magmatic textures suggests that twinning mechanism in plagioclase controls the intra-grain diffusion of hydrous fluids. Located at the interface of the Moho Transition Zone (MTZ) and semi-brittle lithosphere, the ‘black gabbros’ record a narrow domain where focused fluid flow induces rapid cooling below the gabbro solidus at the lowest limit of the magma chamber.

Pitting behavior of austenitic stainless-steel welded joints with dense inclusions and methods to enhance pitting resistance

PurposeThis study aims to assess the pitting resistance of austenitic stainless steel welded joints fusion zone (FZ) with high density of inclusions before and after surface treatment, including potentiostatic pulse technique (PPT) and pickling.Design/methodology/approachThe potentiodynamic polarization tests and critical pitting temperature tests were carried out for estimating pitting resistance. The PPT and pickling were performed as surface treatment. Scanning electron microscope (SEM) and energy dispersive spectrometer were used for characterize the microstructure and elemental distribution. Electron back-scattered diffraction (EBSD) was used to assess the portion of phases and morphology of grains.FindingsThe weld metal exhibits a higher degree of alloying compared to the base metal, and it contains d-phase and sulfur-containing inclusions. Sulfur-containing inclusions serve as initiation sites for pitting, and they diminish the pitting resistance of weld metal. Both PPT and pickling can remove sulfur-containing inclusions, but PPT causes localized dissolution of the weld metal matrix around the inclusions, while pickling does not. Because of the high density of inclusions, certain pits initiated by PPT are significantly deeper, which makes the formation of stable pitting easier. Because of the high density of inclusions, certain pits initiated by the PPT are deeper. This characteristic facilitates the progression of these initial defects into fully developed, stable pits.Originality/valueAnalysis of pitting initiation in shielded metal arc welding FZ with PPT and ex situ SEM tracking observation. Explanation of why the PPT surface treatment is not able to enhance the pitting resistance of stainless steel with a high inclusion density.

Observation of inclusions and intra-granular ferrite evolutions at the HAZ of low-carbon steel with different thermal histories

This study investigated the formation and growth of intra-granular ferrite with inclusions (TiN, MnS) in the heat-affected zone (HAZ) of a welding joint in low-carbon steels. The relationship between the cooling rate and the density and size of inclusions was analyzed. An orientation relationship akin to the Baker–Nutting relationship was identified between TiN and ferrite, while the orientation relationship between MnS and ferrite approximated the Kurdjumov–Sachs relationship. At low cooling rates, in the absence of nucleation support from TiN and MnS inclusions, the microstructure in the HAZ comprised Widmanstätten ferrite. Additionally, the shape, size, and density of primary ferrites and Widmanstätten ferrite in steels were influenced by sulfur content.

Achieving spatial balance in environmental surveys under constant inclusion probabilities or inclusion density functions

AbstractIn environmental and ecological surveys, well spread samples can be easily obtained via widely adopted tessellation schemes, which yield equal first‐order inclusion probabilities in the case of finite populations of areas or constant inclusion density functions in the case of continuous populations. In the literature, many alternative schemes that are explicitly tailored to select well spread samples have been proposed, but owing to their complexity, their use should be preferred only if they allow us to achieve a valuable gain in precision with respect to the tessellation schemes. Therefore, by means of an extensive simulation study, the performances of tessellation schemes and several specifically tailored schemes are compared under constant first‐order inclusion probabilities or constant inclusion density functions.

Effect of Different Calcium and Magnesium Treatments on the Evolution of Nonmetallic Inclusions in AH36 Ship Plate Steel

Comprehensive thermodynamic calculations and high‐temperature experiments are performed to systematically evaluate the effect of calcium and magnesium additions on the modification and control of inclusions in AH36 ship plate steel. The results show that Al2O3 or MgAl2O4 inclusions are formed under the casting temperature conditions. Calcium treatment modifies the inclusions into calcium aluminate, of which components partially fall into the liquidus region, and the aspect ratio and number density of inclusions became smaller, avoiding nozzle clogging, but the inclusions are easy to gather and grow up, which would affect the steel properties. Magnesium treatment modifies the inclusions into dispersed magnesium‐aluminum spinel with small size. However, the number density and aspect ratio of inclusions increase, as well as the melting points of inclusions are high, which would easily cause nozzle clogging. When calcium–magnesium synergistic treatment, with the increase of magnesium proportion, the inclusions types increased, and the liquidus area of inclusions became narrower until it disappeared. Synergistic treatment with more calcium and less magnesium (Ca2Mg1) is optimal since the inclusions were fine and diffuse, and the corresponding liquidus area of inclusions is wider than the calcium treatment.

Robust high capacity in-plane elastic wave transport in 2D chiral metastructures

Novel 2D tri-chiral metastructures with mass inclusion are proposed in this work. Compared to conventional 2D honeycomb metastructures, these superior metastructures have a wide in-plane low-frequency bandgap (BG) and single Dirac cone (DC) simultaneously. Ligament width and inclusion density are both key factors for tuning the DC and low-frequency BGs. Due to the superior dispersion properties, metamolecules analog of quantum spin Hall effects (QSHEs) are built by the band folding method, and topological phase transition is obtained by shrinking/expanding distance between the mass inclusion and metamolecule center. Topological interface states (TISs) are observed between the two domains with distinct topological properties. To further enhance energy capacity of in-plane elastic wave transport, a 2D heterostructure is constructed by doping waveguiding layer at the topological interface. As expected, robust high capacity in-plane elastic wave transport is realized, named as topological waveguide states (TWSs). While TWS velocity remains unaffected, an increasing number of waveguiding layers additionally leads to a reduced bandgap width and transition from TWSs to conventional edge states (CESs). Average transmitted energy is also observed to increase almost linearly with the thickness of waveguide layer. By virtue of the robust high-capacity wave transport, two potential applications for energy focusing and beam splitting are clearly demonstrated. Besides, the temperature field is introduced into the 2D topological heterostructure to widen the operating frequency of TWSs. Fortunately, TWSs can be tuned to the lower frequency range by increasing temperature, and retain gapless and high-capacity characteristics. Last but not least, we demonstrate that temperature can be used as a switch for in-plane topological wave transport. The proposed 2D chiral metastructures have great potentials to serve as building blocks for multifunctional topological devices.

Computer-Based Evaluation of α-Synuclein Pathology in Multiple System Atrophy as a Novel Tool to Recognize Disease Subtypes

Multiple system atrophy (MSA) is a neurodegenerative disorder with variable disease course and distinct constellations of clinical (cerebellar [MSA-C] or parkinsonism [MSA-P]) and pathological phenotypes, suggestive of distinct α-synuclein (αSyn) strains. Neuropathologically, MSA is characterized by the accumulation of αSyn in oligodendrocytic glial cytoplasmic inclusions (GCI). Using a novel computer-based method, this study quantified the size of GCIs, density of all αSyn pathology, density of only the GCIs, and number of GCIs in MSA cases (n = 20). The putamen and cerebellar white matter were immunostained with the disease-associated 5G4 anti-αSyn antibody. Following digital scanning and image processing, total 5G4-immunoreactive pathology (ie, neuronal, neuritic, and glial) and GCIs were optically dissected for inclusion size and density measurement and then evaluated applying a novel computer-based method using ImageJ. GCI size varied between cases and brain regions (P < .0001), and heterogeneity in the density of all αSyn pathology including the density and number of GCIs were observed between regions and across cases, where MSA-C cases had a significantly higher density of all αSyn pathology in the cerebellar white matter (P = .049). Some region-specific morphologic variables inversely correlated with the age of onset and death, suggestive of an underlying aging-related cellular mechanism. Unsupervised K-means cluster analysis classified MSA cases into 3 distinct groups based on region-specific morphologic variables. In conclusion, we developed a novel computer-based method that is easily accessible, providing a first step to developing artificial intelligence–based evaluation strategies for large scale comparative studies. Our observations on the variability of morphologic variables between brain regions and cases highlight (1) the importance of computer-based approaches to detect features not considered in the routine diagnostic practice, and (2) novel aspects for the identification of previously unrecognized MSA subtypes that do not necessarily reflect the current clinical classification of MSA-C or MSA-P.