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Abstract Most research on nanocrystalline alloys has been focused on planned doping of metals with other metallic elements, but nonmetallic impurities are also prevalent in the real world. In this work, we report on the combined effects of metallic dopants and nonmetallic impurities on grain boundary energy and strength using first-principles calculations, with a Σ5 (310) grain boundary in Cu chosen as a model system. We find a clear correlation between the grain boundary energy and the change in excess free volume of doped grain boundaries. A combination of a larger substitutional dopant and an interstitial impurity can fill the excess free volume more efficiently and further reduce the grain boundary energy. We also find that the strengthening effects of dopants and impurities are dominated by the electronic interactions between the host Cu atoms and the two types of dopant elements. For example, the significant competing effects of metal dopants such as Zr, Nb, and Mo with impurities on the grain boundary strength are uncovered from the density of states of the d electrons. As a whole, this work deepens the field's understanding of the interaction between metallic dopants and nonmetallic impurities on grain boundary properties, providing a guide for improving the thermal stability of materials while avoiding embrittling effects. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

It is found from results of studying rolled steel from special alloyed steels of industrial grades 30G1R, 40Kh and laboratory grades 12KhN, 38KhGNM, 41Kh1 that a change in the ratio of Mn:S concentration in the range of 21-620, P content from 0.004 to 0.022 wt.%, non-metallic inclusions up to point 2.5 according to GOST 1778, N up to 0.010%, H up to 0.0005%, with total pressure created by gas-forming elements up to 1.05 atm, are not critical for occurrence of defects and rolling capacity for cold upsetting. Determination of the characteristics of NI, and CANI content in steel 40Kh round rolled product shows that metal corrosion resistance increases by more than a factor of three with a reduction in CANI2 content and inclusions of the system CaO-AlO-MgO containing up to 5 wt.% SiO, and the insignificant effect of other types of inclusions. A study of the metal of high-strength fasteners manufactured by JH (Taiwan), OF, AL (USA) shows that it has a significantly lower content of other types (corundum, calcium, aluminate, sulphide) of inclusions, and conversely better corrosion resistance. [ABSTRACT FROM AUTHOR]

A range of copper nanopowders (BET particle size 20–70 nm) has been prepared through a DC thermal plasma synthesis under varying operating conditions. A thermal evolution analysis was performed on these materials to quantify the nonmetallic impurities (O, C, N, H) which originated from the working and ambient environments. A temperature-programmed oxidation-infrared detection (TPO) was used for carbon and hydrogen determinations, an inert gas fusion-infrared/conductometric detection (GFA) for oxygen and nitrogen determinations. The TPO and GFA evolution patterns provided an insight into impurity speciation in terms of the free and chemically bound carbon, oxidic and adsorbed oxygen, as well as the possible types of organic functionalities. The impurity uptake and speciation were found to be a strong function of the operating conditions, including the choice of the plasma gas and the Cu feedstock. The operating conditions were identified under which the oxidation of the product nanopowder was minimized upon exposure to ambient laboratory environment. The product passivation during the synthesis was attributed to the presence in the working environment of the gaseous species (CO, CN), which are capable of strong chemisorption on the freshly prepared copper surface. [ABSTRACT FROM AUTHOR]

The effect of technology of introducing REM on the composition and shape of nonmetallic inclusions and physicomechanical properties of carbon and low-alloy steels for different purposes is analyzed, and criteria are provided for REM consumption in relation to sulfur and oxygen content within metal, making it possible to determine the optimum REM distribution with which there is an increase in ductility properties, impact energy, and sheet and plate anisotropy properties of the sheet are reduced. Microalloying of carbon and alloy steels and alloys with REM improves corrosion resistance, hot ductility, thermal shock resistance, and other operating properties. [ABSTRACT FROM AUTHOR]

Chemical composition, microstructure, contamination with nonmetallic inclusions, and corrosion resistance indices are studied for about twenty grades of steel. Dependences are determined for the effect of rolled product properties on pipe metal corrosion resistance indices. A concept of producing corrosion-resistant 'SeverkorYuni' steels is developed for use in the housing and utilities sector. [ABSTRACT FROM AUTHOR]

The effect of pipe billet production technology and of the order of introducing rare-earth elements and calcium on nonmetallic inclusion composition and morphology is studied. The correlation of inclusion morphology with corrosion resistance and casting suitability for steel in a CBCM is evaluated. [ABSTRACT FROM AUTHOR]

The present paper deals with the influence of non-metallic inclusions on fatigue life in the high cycle fatigue and the very high cycle fatigue regime. For that purpose, several castings of steel 42CrMo4 (AISI 4140, DIN EN 1.7225) were produced by using recently developed novel metal-melt filters. The specimens were tested in hot-isostatically pressed and heat treated condition. After fatigue failure every fracture surface was intensively investigated by scanning electron microscopy in order to define the type, the size, the chemical composition, the morphology and the location of the crack initiating discontinuity. Subsequently, Murakami’s √ area model was used for the evaluation of the influence of non-metallic inclusions on the fatigue life. In the present investigation four common types of chemical compositions of crack initiating discontinuities were identified. Furthermore, four different internal failure types and their influence on the fatigue life in cast steel were investigated and described. Thus, the present contribution proposes a basic correlation determined from fatigue lives in case of various internal crack initiation types. The key parameters for fatigue life prediction in case of internal fatigue failure in the very high cycle fatigue regime are (i) the size of the crack initiating discontinuity, (ii) the inclusion depth and (iii) the crack initiating failure type. [ABSTRACT FROM AUTHOR]

Results of a detailed study of continuously-cast low-alloy pipe steel metal demonstrate a significant difference in micro- and macrostructural states, including the presence and extent of equiaxed and columnar crystal areas in relation to the later stages of ladle treatment. A marked difference is also recorded in impact strength indices, hydrogen corrosion cracking resistance, and other service properties obtained for different rolled billets. It is established that as a result of adding large amounts of silicon- and manganese-containing ferroalloys in the later stages of ladle treatment or in the process of steel continuous casting there is formation of liquid silicate inclusions. Due to a high silica content during steel crystallization these inclusions are converted into a supercooled liquid or glassy condition and acquire irregular shape, filling the space between growing crystals. As a result of this they effectively reduce the intensity of mass- and heat-transfer during steel crystallization, block development of liquation processes, and facilitate an increase in the degree of metal structural and chemical inhomogeneity. As a consequence there is an increase by a factor of 2-2.5 in impact strength to extremely high values ( KCV more than 400-420 J/cm), and rolled product hydrogen cracking resistance. [ABSTRACT FROM AUTHOR]

Results are provided for a study of a steel 38KhN3MFA metal ingot weighing 1.53 ton cast with a head section cooler intended for producing hollow forgings. The position of pores and nonmetallic inclusion distribution is studied: oxides, oxysulfides, and sulfides. Features are revealed for the position and amount of pores and nonmetallic inclusions at three ingot levels: lower, central, and head sections. The effect of ingot head section cooling on crystallization and features of oxide, oxysulfide, and sulfide is revealed. [ABSTRACT FROM AUTHOR]

Analyzing failure causes of the parts made of heat resistant steel shows that one of the defining factors impacting the properties is concentration of harmful impurities both dissolved in steel and being in the form of nonmetallic inclusions. The latter, in turn, is considerably defined by the process of steel deoxidation. [ABSTRACT FROM AUTHOR]

A computer model is constructed to describe the formation of nonmetallic inclusions in high-carbon bearing steel. The effect of the steel's contents of aluminum, nitrogen, and oxygen on the formation of oxide and nitride phases during crystallization is analyzed, and it is established that the quantity of aluminum oxides formed depends non-monotonically on the aluminum content of bearing steel. Efficient deoxidation and microalloying with aluminum is proposed as an effective means of improving the quality of bearing steel. [ABSTRACT FROM AUTHOR]

Abstract: The conventional method to synthesize carbon nanotubes (CNTs) requires the use of metallic catalysts. However, the metallic particle impurities usually contaminate the CNTs, and are difficult to remove without introducing defects and contaminations. An alternative and more desirable approach is to grow CNTs directly on a substrate without further treatment being required. The review presents and discusses the current development of the controlled synthesis of SWCNTs and/or MWCNTs using non-metallic catalysts, which comprises of various ceramics and semiconductors as catalytic particles. All-carbon systems for CNT growth without employing any catalysts are also discussed. Despite the enormous strides in the synthesis of CNTs, the precise atomistic mechanism explaining their nucleation and growth still remains unclear. Therefore, the different growth systems proposed by several authors are also examined in this article. The review concludes with a summary and an outlook on the challenges and future directions in the metal-free-catalyst growth of CNTs. [Copyright &y& Elsevier]

Investigations were carried out into the relationship between the shape and composition of non-metallic inclusions, formed in the weld metal in welding E36 and AB steels with low-alloy wires under agglomerated fluxes of the MgO–CaF2–Al2O3–SiO2system, and the composition of the flux. It is shown that the increase in the fraction of circular non-metallic inclusions and the reduction of the fraction of elongated inclusions in the weld metal, like the reduction of the mean size of the inclusions, increase the impact work of the weld metal at the test temperature of − 40°C. [ABSTRACT FROM PUBLISHER]

Abstract: The objective of this study is to determine the threshold stress intensity factor for small cracks in high strength steels in a hydrogen environment by studying the failure of hydrogen pre-charged cylindrical specimens loaded in uniaxial tension. Fracture of these specimens under tension usually initiates at the largest nonmetallic inclusion contained in the specimen and such typical inclusions are Al2O3·(CaO) X and TiN. The onset of the failure process is the crack initiation and propagation from a cavity forming either through debonding along the inclusion/matrix interface or through cracking of the inclusion. By analyzing the stress intensity factor for planar cracks emanating from inclusions, we calculated the threshold stress intensity by using experimental measurements of the applied tensile stress at the failure of the specimen. The results indicate that the threshold stress intensity is a linear function of the size of the inclusion and the hydrogen concentration in the specimen upon failure. The size of the inclusion is calculated as , where area denote the area of the domain defined by projecting the inclusion surface on a plane normal to the cylindrical axis of the specimen. Analysis of the experimental data indicates that the threshold stress intensity decreases as the inclusion size decreases. The estimates of KTH obtained by this method through fracturing uniaxial tension specimens can be used as a lower bound of the resistance to hydrogen embrittlement (HE) of component of high strength steel containing small defects and cracks. [Copyright &y& Elsevier]

Titanium oxide inclusions in steel are well known to inhibit grain growth and act as nucleation sites for acicular ferrite because of absorbing manganese from the surrounding steel resulting in a manganese depleted zone around the inclusion. In this article, the inclusions resulting from TiO additions to low-alloyed C-Mn-Cr steel were studied. Different types of TiO containing materials were added to liquid steel before or during casting to get small titanium-oxide-rich inclusions in steel. The main goals were to find out what happens to TiO in liquid steel after addition and during cooling and to study further what type of inclusions are formed in the steel as a result of the TiO addition. Based on the thermodynamic calculations and the results of scanning electron microscope (SEM)-energy dispersive spectroscope (EDS) and SEM-electron backscatter diffraction (EBSD) analysis, TiO is first reduced to TiO in liquid steel at high temperatures and then to TiO during cooling at around 1573 K (1300 °C). Both reactions liberate oxygen, which reacts with Ti, Mn, and Al forming complex TiO-rich inclusions. The results also show that TiO additions result in more TiO + MnO inclusions compared with experiments with Ti addition and that the absolute amount of manganese present in the inclusions is much higher in experiments with TiO addition than in experiments with Ti additions. [ABSTRACT FROM AUTHOR]

Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting. [ABSTRACT FROM AUTHOR]

The main mechanisms are considered for formation and transformation of non-metallic inclusions based on alumina magnesia spinel, and the unfavorable effect on corrosion resistance of carbon and low-alloy steels in aqueous chlorine-containing media. Basic approaches are demonstrated making it possible to reduce the content of the inclusions in question in steel aimed both at reducing the content of inclusions during steel smelting, and on limiting the possibility of their transformation during steel continuous casting and hot rolling. [ABSTRACT FROM AUTHOR]

An integrated technology has been developed for obtaining continuous-cast slabs to be used in rolling plates for critical applications. Special filtration elements are installed in partitions inside the tundish to reduce the content of nonmetallic inclusions in the continuous-cast semifinished product. A channeled ceramic lance for injecting the steel with argon has been developed and installed in the bottom of tundishes to remove nonmetallic inclusions 20 μm or smaller. Metallographic studies confirm the effectiveness of the new technology for obtaining plates of high-strength steels. [ABSTRACT FROM AUTHOR]

Parameters of the process of out-of-furnace treatment of liquid steel in the ladle with participation of highly basic slag, which ensures the required level of purity with respect to corrosion-active nonmetallic inclusions, are determined with the help of methods of statistical analysis of production control data. [ABSTRACT FROM AUTHOR]

The main reason for the accelerated local corrosion of tubes is contamination of the steel by corrosion-active nonmetallic inclusions (CANI), which determine the metallurgical properties of tube steel in terms of their corrosion resistance. Studies have shown that there are two main types of corrosion-active nonmetallic inclusions: CANI1 — inclusions based on calcium aluminates; CANI2 — complex inclusions that contain calcium sulfide. In order to master to production of tubes of steel 20-PKS at the Volga Pipe Plant (VTZ), a study was made of the effect of the parameters of out-of-furnace treatments on the contamination of steel by CANI. 1. The mechanisms and main sources of formation of CANI in tube steels made by the VTZ were determined. The main reasons for the formation of CANI1 in furnace slag containing thermodynamically active CaO are mixing of the metallic and slag phases during the argon blow and the simultaneous introduction of additions to correct the chemical composition of the steel. Inclusions of the CANI2 type may be formed by deoxidation operations carried out with suboptimal proportions of added aluminum and calcium (lime). 2. The following measures are recommended to ensure that steel 20-PKS made by the VTZ is clean with respect to both types of CANI: • optimize the composition of the ladle slag (increase the average content of Al2O3, increase the average content of SiO2 as much as possible, and in any case decrease the average concentration of CaO); • keep the mass ratio of added CaO to added Al within the range 1.5–2; • continue the argon blow done after addition of the last batch of ferroalloys for at least 15–20 min; • ensure that the intensity of the blow is at least 0.5–1.5 m3/min. 3. Vacuum-degassing steel in the ladle after treatment on a ladle-furnace unit makes it possible to distribute the CANI more uniformly over the volume of the steel. [ABSTRACT FROM AUTHOR]

To refine existing standards on the content of corrosion-active nonmetallic inclusions (CANI) in semifinished products, the Sinarskii Pipe Plant has made a study of the change in the density and shape of CANI from the semifinished product to the finished pipe. The study was performed on three heats having a CANI density within the established norm (no more than 2 inclusions/mm2) and on six specimens with a CANI density greater than 2 inclusions/mm2. Researchers followed the change in inclusion density in relation to the degree of deformation of semifinished products of steel 20-PKS made by the Volga Pipe Plant. The semi-finished products were 120 and 156 mm in diameter and were used in pipe production. An analysis of the study results showed that CANI density in the finished pipe is no greater than 2 inclusions/mm2 if the CANI in the semifinished product are uniformly distributed, their average density is no greater than 2 inclusions/mm2, and their maximum density is no greater than 4 inclusions/mm2. It was determined that CANI density is not affected by the degree of deformation of the semifinished product. [ABSTRACT FROM AUTHOR]

The effect of defects in the structure of a slab on the set of properties of sheet steel 07G2FBYu used for large-diameter electrically welded pipes for oil and gas pipelines is investigated. The structure and content of nonmetallic inclusions are studied at the edges and in the middle of slabs. Types of inclusions are determined. The effect of the mode of double hardening and high-temperature annealing on the microstructure of the steel is analyzed, including its variation over the sheet width. Changes in the strength, ductility, and resistance to brittle fracture, stress corrosion, sulfurated hydrogen corrosion, and hydrogen-stress cracking are considered. A hypothesis that the stress-corrosion cracking in electrically welded pipes serving in pipelines depends on the contamination of the edge zone of the sheet steel with nonmetallic inclusions is considered. [ABSTRACT FROM AUTHOR]

Nonmetallic inclusions are harmful to the mechanical properties of every kind of steel produced worldwide. The greater the size of the inclusion present in the structure of a determined kind of steel, the greater its negative effect on the quality of the steel. Therefore, the objective of this work was to investigate the size, the quantity, the shape and the chemical composition of nonmetallic inclusions formed throughout the refining process of silicon-killed, low-carbon steel, as a function of the treatment time in a ladle furnace, trying to ensure the flotation of inclusions bigger than 25 μm. This investigation was carried out using a scanning electron microscope (SEM), with an analysis system using energy dispersive spectometry (EDS). Based on this work, it was possible to know more precisely the nature of the inclusions, the necessary time to ensure flotation of large inclusions, the efficiency of the slag to capture the inclusions, and the inclusion level of the steel throughout its refining process to try to obtain a higher quality steel product. [Copyright &y& Elsevier]

Nonmetallic inclusions are studied on grain boundaries in steel 1002FT by methods of scanning and transmission electron microscopy and microscopic x-ray spectral analysis. A special method is developed for evaluating the degree of contamination of the surface of intergrain fracture with segregations of specific morphology. The relation between the degree of the contamination and the properties of steel 10G2FT is determined. [ABSTRACT FROM AUTHOR]

A transient coupled mathematical model has been proposed to predict the motion and distribution of nonmetallic inclusions in the electroslag remelting process. The electromagnetic field, temperature distribution, flow pattern, solidification, and inclusion behavior were solved simultaneously. The Euler-Lagrange approach was used to describe the interaction between continuous phase and inclusions. The discrete phase model (DPM) was adopted to track the particles acted by a number of forces. An experiment under argon protection was implemented, and it agrees well with the simulation. The effect of inclusion diameter was also discussed. The experiment result shows that the typical inclusions in final ingot are Al2O3 core surrounded by an outer sulfide layer and pure MnS inclusions. The total area of inclusions increases from center toward ingot surface, while the average equivalent diameter decreases. The simulated result indicates a denser distribution of inclusions locations at the region ranging from 0.7 to 0.9 radii. Few inclusions are entrapped near the mold due to the strong descending flow. Moreover, the inclusion amount increases with height. The total amounts of inclusions with diameter of 2 μm, 5 μm, and 10 μm in ingot are 2199, 1871, and 1704, respectively. The imposed buoyancy and floatation contribute to this phenomenon. [ABSTRACT FROM AUTHOR]