Influence Of Non-metallic Inclusions Research Articles

Study on the Influence of Non-Metallic Inclusions on the Pitting Corrosion of API 5L X60 Steel

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.

Microstructure and Surface Topography Study of Nanolayered TiAlN/CrN Hard Coating

The microstructure and surface topography of PVD hard coatings are among the most important properties, as they significantly determine their mechanical, tribological and other properties. In this study, we systematically analyzed the microstructure and topography of a TiAlN/CrN nanolayer coating (NL-TiAlN/CrN), not only because such coatings possess better mechanical and tribological properties than TiAlN and CrN monolayer coatings, mainly because the contours of the individual layers, in the cross-sectional STEM or SEM images of such coatings, make it easier to follow topographic and microstructural changes that occurred during its growth. We investigated the effects of the substrate rotation modes on the microstructure and surface topography of the NL-TiAlN/CrN coating, as well as on the periodicity of the nanolayer structure. The influence of the substrate material and the ion etching methods were also studied, while special attention was given to the interlayer roughness and influence of non-metallic inclusions in the steel substrates on the growth of the coating. The topographical features of the NL-TiAlN/CrN coating surface are correlated with the observations from the cross-sectional TEM and FIB analysis. Selected non-metallic inclusions, covered by the NL-TiAlN/CrN coating, were prepared for SEM and STEM analyses by the focused ion beam. The same inclusions were analyzed prior to and after deposition. We found that substrate rotation modes substantially influence the microstructure, surface topography and periodicity of the NL-TiAlN/CrN layer. Non-metallic inclusions in the substrates cause the formation of shallow craters or protrusions, depending on their net removal rates during the substrate pretreatment (polishing and ion etching), as compared to the matrix.

Effect of Non-Metallic Inclusions on the Fatigue Strength Coefficient of High-Purity Constructional Steel Heated in Industrial Conditions

Steel fatigue strength testing is a process that requires large amounts of time, resources and appropriate equipment. The industry seeks to replace cumbersome destructive testing with non-destructive testing. Coefficients were developed that allow the comparison of the parameters of material properties. One such factor is the fatigue strength coefficient, which allows the estimate of fatigue strength using the known hardness of a given material. The fatigue strength factor should be developed for conditions that are as close to the industrial conditions as possible. It should take into account not only the expected properties of the material and the technological process but also its imperfections, e.g., the share of non-metallic inclusions and the steel microstructure. This paper presents the results of research on the influence of non-metallic inclusions on the fatigue strength coefficient of structural steel subjected to rotary bending. The tests were carried out in seven heats obtained in a 140-ton electric furnace under industrial conditions. The steel was desulfurized and refined with argon. The paper presents the bending fatigue strength of hardened and tempered steel at temperatures from 200 °C to 600 °C as a function of the relative volume of inclusions. The non-metallic inclusions occurring in steel were determined qualitatively and quantitatively. The derived fatigue strength coefficient, k, for different tempering temperatures makes it possible to estimate the fatigue strength of the analyzed steel as a function of its hardness for various microstructures represented by the respective tempering temperatures.

Influence of Non-Metallic Inclusions on Bending Fatigue Strength of High-Quality Carbon Constructional Steel Heated in an Industrial Electric Arc Furnace.

Non-metallic inclusions are one of the many factors influencing the strength of materials operating under variable loads. Their influence on the strength of the material depends not only on the morphology of the impurities themselves, but it is also closely related to the microstructure of the material. This microstructure is the matrix for non-metallic inclusions. This article discusses the results of a study investigating the effect of non-metallic inclusions on the fatigue strength of structural steel during rotary bending. The study was performed at 12 heats produced in an industrial plant’s 140-ton electric furnaces. Six heats were desulphurised, and six were refined with argon. This paper presents the bending fatigue strength of steel hardened and tempered at different temperatures, subject to the relative volume of inclusions. This paper also presents the dimensional structure of non-metallic inclusions divided by different two technologies. The research shows that the main fraction of non-metallic inclusions is Al2O3; the most numerous were impurities with a diameter of less than 2 µm; argon refining does not affect the proportion of non-metallic inclusions of large dimensions (with a diameter of over 15 µm); the influence of non-metallic inclusions on the strength of the steel is also related to the microstructure of the steel constituting the matrix of inclusions.

Influence of Non-Metallic Inclusions on Local Deformation and Damage Behavior of Modified 16MnCrS5 Steel

This work investigates a ferrite matrix with multiple non-metallic inclusions to evaluate their influence on the global and local deformation and damage behavior of modified 16MnCrS5 steel. For this purpose, appropriate specimens are prepared and polished. The EBSD technique is used to record local phase and orientation data, then analyze and identify the size and type of inclusions present in the material. The EBSD data are then used to run full phase crystal plasticity simulations using DAMASK-calibrated material model parameters. The qualitative and quantitative analysis of these full phase simulations provides a detailed insight into how the distribution of non-metallic inclusions within the ferrite matrix affects the local stress, strain, and damage behavior. In situ tensile tests are carried out on specially prepared miniature dog-bone-shaped notched specimens in ZEISS Gemini 450 scanning electron microscope with a Kammrath and Weiss tensile test stage. By adopting an optimized scheme, tensile tests are carried out, and local images around one large and several small MnS inclusions are taken at incremental strain values. These images are then processed using VEDDAC, a digital image correlation-based microstrain measurement tool. The damage initiation around several inclusions is recorded during the in situ tensile tests, and damage initiation, propagation, and strain localization are analyzed. The experimental results validate the simulation outcomes, providing deeper insight into the experimentally observed trends.

Influence of non-metallic inclusions on the corrosion resistance of cold-rolled low-carbon steels microalloyed with titanium

Influence of non-metallic inclusions on the corrosion resistance of cold-rolled low-carbon steels microalloyed with titanium

A novel methodology for fatigue assessment of high strength steels with non-metallic inclusions

In the present paper, the multiaxial critical plane-based criterion proposed by Carpinteri et al. is employed in conjunction with the √area-parameter model by Murakami and Yanase for the fatigue assessment of high strength steels, where the influence of non-metallic inclusions on fatigue life is taken into account. An experimental campaign, available in the literature and performed on AISI 4140 steel specimens, is analysed to evaluate the criterion accuracy. The obtained results in terms of fatigue lifetime are compared with those experimentally obtained, showing a quite satisfactory agreement.

INFLUENCE OF NON-METALLIC INCLUSIONS ON THE CORROSION RESISTANCE OF STAINLESS STEELS IN ARC SURFACING

The influence of non-metallic inclusions on the corrosion resistance of stainless steel of the austenitic-martensitic class, deposited in one layer with flux-cored wire under the flux by the arc method in the mode of stationary and pulsed arc burning, has been studied. In the latter case, the wire feed impulse was 0.5 and 0.7 Hz. The selected surfacing conditions, with both methods of the process, contribute to the formation of non-metallic inclusions of complex composition and structure in the deposited metal, including those containing calcium and its compounds with other elements, which are classified as corrosive, accelerating the occurrence of corrosion phenomena.

Influence of non-metallic inclusions on the high cycle fatigue strength of steels

In the present paper, a criterion for fatigue assessment of high strength steels is proposed, where the influence of non-metallic inclusions on fatigue life is taken into account. To such an aim, the Carpinteri et al. criterion is used in conjunction with the area-parameter model by Murakami and Yanase. An experimental campaign available in the literature is analysed to evaluate the criterion accuracy.

Influence of non-metallic inclusions on the high cycle fatigue strength of steels

Influence of non-metallic inclusions on the high cycle fatigue strength of steels

Influence of Non-metallic Inclusions in 316L Stainless Steels on Machining Using Different Cutting Speeds

This research focuses on providing a detailed characteristic of non-metallic inclusions (NMIs) in 316L stainless steels with and without Ca treatment after machining using different cutting speeds. The electrolytic extraction (EE) technique was used for three-dimensional determinations of the inclusion characteristics. Quantitative data from the fragile non-metallic inclusions (such as size, surface area, number) in chips obtained from different cutting speeds and materials were determined. The morphologies of NMIs in the chip samples were quite different compared to the original inclusions in the stainless steel samples before machining. It was proved that the deformation degree of soft inclusions such as MnS and CaO–SiO2–Al2O3–MgO–TiOx is dependent on the cutting speed as well as the temperatures and deformation degrees of the metal matrix during machining. The total surface areas of MnS inclusions increase from 2.8 to 3.8 times compared to the original total areas with an increased cutting speed. The total surface areas of soft oxide inclusions also increase from 1.1 to 3.5 times compared to the original total areas. In addition, the tool-chip contact lengths were also measured on the rake face of the tool, and the results were compared to the determined characteristics of the observed inclusions. It was found that the modification of NMIs by Ca treatment in 316L stainless steels is preferred for high cutting speeds.

Metallurgical methods of improving the machinability of structural steels to increase the productivity of processing in the conditions of automated production

The influence of non-metallic inclusions on the main indicators of steel machinability is investigated. The influence of non-metallic inclusions on the cutting force is determined. Generalized formulas for calculating tool life, cutting speed and cutting force components are proposed. Keywords: machinability, productivity, structural steel, non-metallic inclusions. anna_vik@mail.ru

Defects of the hardened layer at laser exposure

Purpose. It is necessary to investigate the influence of non-metallic inclusions on the formation of defects during laser processing. The aim of the work was to study the defects of the hardened layer of steels under laser action, associated with the presence of non-metallic inclusions. Methods. The materials for investigation were commercial steels containing different non-metallic inclusions. The specimens of different steels with preliminary polished surface were exposed to laser beaming on the installations GOS-30M and GUANTUM-16. The research methods were applied - petrography, X-ray microscopy (MS-46 Cameca) and optical microscopy (Neophot-21) to study defects and identify of inclusions. Results. It has been established that various types of defects appear on the surface and in the surface layer of steel under laser action, which are not connected and are associated with non-metallic inclusions. It is shown that non-metallic inclusions are the reason for the appearance of various kinds of defects in the hardened layer of steel products during laser processing (cracks, cavities, violation of the geometry of the hardened layer). The reasons for the appearance of defects associated with the presence of inclusions of various types are discussed. Scientific novelty. A classification of defects in the hardened layer is presented. The nature and features of the formation of defects, associated with the appearance of high-speed thermal stresses, structural inhomogeneity, as well as melting, thermal destruction and evaporation of inclusions emerging to the surface and located within the hardened layer, have been established. It is noted that the detected defects are ready-made centers of destruction of a steel product or part under conditions of static and dynamic loads, as well as contact stresses. Practical significance. It is shown that the unsatisfactory quality of the hardened layer associated with the presence of various kinds of defects near nonmetallic inclusions contributes to a decrease in the mechanical and operational characteristics of a steel product. The use of the obtained results will make it possible to develop technologies for laser processing of steels with regulated quality parameters of the hardened layer, which will prevent the formation of various kinds of defects.
 Keywords: steel; laser treatment; defects; cracks; hardened layer; non-metallic inclusions

Influence of Non-metallic Inclusions on Corrosive Properties of Polar Steel

Polar steel requires excellent toughness and corrosion resistance for breaking icy surfaces in low-temperature seawater environments. In this study, the effect of inclusions on the corrosion resistance of polar steel was examined. In the experiments conducted, the composition and morphology of the inclusions in steel were controlled using different deoxidation methods during steel refining. The morphology and composition of the corrosion-resistant active inclusions were analyzed using scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of polar steel was determined by measuring the saturation current density of the anodic dissolution of steel in a corrosive medium via an electrochemical method. The corrosion resistance under simulated seawater was also investigated under laboratory conditions. It was found that as the ratio of Al/Mg approaches the stoichiometric composition of the spinel (2.3–2.5), the inclusions become less active; as the ratio increases further, the corrosion-resistant activity increases due to the formation of MgAl2O4⋅CaO complexes, leading to an increase in local stress around the inclusions. If steel is deoxidized with Zr–Ti, small Zr–Ti complex oxides form in the steel, providing nucleation particles for the precipitation of spheroidized and uniformly distributed MnS. Therefore, steel deoxidized with Zr–Ti has better seawater corrosion resistance than Al-deoxidized steel.

Fractals Theory Application for Evaluation of Influence of Non Metallic inclusions on Mechanical Properties of S355J2 Steel

Influence of non-metallic inclusions in constructional S355J2 steel on mechanical properties has been evaluated by using fractal theory. Since point evaluation of non-metallic inclusions is fault tolerant to mechanical properties change. Point evaluation of experimental steel grades has been evaluated by 1-2 points. Correlation between mechanical properties of the steel (KV20, σ0.2, σB, δ) and fractal dimensions of non-metallic inclusions has been found. Mechanical properties of the steel have been ranking according to influence of fractal dimensions of non-metallic inclusions on the properties. It has been revealed that non-metallic inclusions, evaluated by their fractal dimensions, have strong effect on impact toughness of the steel S355J2 (R² = 0.89). It can be explained by reducing the metal matrix resistance to crack propagation due to non-metallic inclusions in the matrix. Method of mechanical properties ranging by non-metallic inclusions fractal dimensions allow to vary chemical composition of steel for main parameter obtaining. In this particular case for necessary impact toughness of constructional S355 steel narrower chemical composition of the steel should be chosen.

Оценка анизотропии механических свойств листового проката из углеродистой стали

The purpose of the article is to establish experimentally the effect of material inhomogeneity on the characteristics of strength ( σ в, σ 0.2) and plasticity (δ) on example of a rolled steel sheet. Uniaxial tensile testing was carried out on flat samples of hot-rolled sheet made of St3 alloy cut in three directions relative to rolling: along, across and at the angle of 450. The heterogeneity of structure was established by studying the fracture surface of the destroyed samples after tensile testing. A metallographic research and micromechanical testing (measurement of microhardness) of sections parallel to the fracture surface were carried out as well. The uniaxial tensile testing of flat samples resulted in obtaining the values of the characteristics of strength ( σ в, σ 0.2) and plasticity (δ). The analysis of fracture patterns, microstructure and microhardness values of the material allowed to reveal the structural heterogeneity caused by the presence of fibrousness and a banded ferrite-pearlite structure oriented along the deformation direction. The formation reason of the latter was the presence of oriented non-metallic inclusions - elongated plastic sulfides. The study determined that the material under investigation features the anisotropy of mechanical properties and structural heterogeneity. The values of the ultimate strength ( σ в) and yield strength ( σ 0.2) decrease from the longitudinal direction to the transverse direction (relative to the rolling direction) and vice versa (from the transverse to longitudinal direction) in the first case probably due to the influence of non-metallic inclusions (plastic sulfides) and, as a result, the banded ferrite-pearlite structure; in the second case due to the influence of fiber direction. The values of the relative elongation (δ) decrease from the longitudinal direction to the direction at an angle of 450 and then increase to the transverse direction as a result of different hardening of the material during plastic deformation. This is proved by the obtained microhardness values of the investigated sections and the values of the maximum applied loads during the tensile test. The obtained values are obviously the result of the influence of fiber orientation relative to the existing maximum tensile stresses.

Effect of non-metallic inclusions on fatigue life of high-speed railway bearings

In the process of smelting and manufacturing of high-speed bearing steel, non-metallic inclusions are always inevitable, which destroy the continuity of the metal matrix and decrease the fatigue life of high-speed railway bearings seriously. Under the condition of obtaining the position and the number of the maximum contact load of the high-speed railway bearings, according to the Hertz contact theory, the maximum contact stress σmax between the roller and the raceway of the high-speed railway bearings and the half-width b of the contact surface is calculated, and then the stress distribution equation of the contact surface is obtained. According to the basic theory of fatigue life, the local stress-strain method was used to analyse the influence of the distance, depth and quantity between the inclusions contained in the raceway of the outer ring on the contact surface stress and the fatigue life of the high-speed railway bearings. Quantitative relationship between the influence of non-metallic inclusions and the contact fatigue life of high-speed railway bearings was determined, which provided scientific bases in the smelting process of high-speed railway bearing steel.

Influence of non-metallic inclusions on the formation of the structure of the steel matrix in explosive loading

Purpose . The goal of this work was to study the localization of deformation near inclusions in steels with various types of metal matrix and the behavior of the inclusions themselves under pulsed loading. Methodology . Dynamic loading of the samples of steels E3 and 08H18N10T was carried out according to the scheme of throwing a thin plate. The calculated pressure was 80...90 GPa, strain rate 100 s -1 , exposure time 1.5 · 10 -6 s. The studies were carried out by several methods: metallographic (Neophot-21), electron microscopic (JSM-35). Findings . The features of local changes in the structure of the steel matrix near non-metallic inclusions under pulsed loading were studied. The processes of localization of deformation near inclusions in steels with various types of metal matrix and the behavior of the inclusions themselves under pulsed loading are discussed. The influence of the physical features of high-speed deformation on the formation of the structure of steels and the processes of its localization near inclusions were analyzed. It was established that stresses localized in a steel matrix near the inclusions cause their destruction. Scientific novelty . The analysis of plastic relaxation zones in a steel matrix was carried out, which made it possible to confirm the formation of regions with various orientations, which indicates a shear-rotational reorientation of these stress relaxation zones near inclusions as a result of plastic deformation having a wave nature. The general patterns of structure formation were determined and the influence of the crystal lattice type of the matrix of steels E3 and 08H18N10T on the development of localization of deformation processes near inclusions was shown. Practical relevance . Using the results obtained will allow us to develop pulsed pressure treatment regimes that allow you to influence the formation of the structure near non-metallic inclusions in various steels.

Nonmetallic Inclusions in 08Kh18N10T Steel as the Cause of Initiation of Defects in Heat-Exchange Tubes of Steam Generators of Nuclear Power Plants

We present the results of investigation of the microstructure of 08Kh18N10T steel in heat-exchange tubes after their long-term operation in steam generators of WWER-1000 power-generating units. We study the influence of nonmetallic inclusions on the degradation of the metal of heat-exchange tubes at the nuclear power plants. It is shown that nonmetallic inclusions located on the metal surface serve as a possible cause of the violation of passivation of the metal and the initiation of corrosion defects. Under the influence of operating factors, alternating stresses are formed in the metal, which leads to microfracture on the inclusion–metal interface and to the development of corrosion fatigue.

Influence of Nonmetallic Inclusions and Corrosion Products on the Wear Resistance of Railroad Wheels

Wear particles are formed at the contact surface of railroad wheels close to nonmetallic inclusions and corrosion products, which are associated with structural changes near the contact surface and reaction of the steel with the atmosphere. Such formation of wear particles is analyzed in the present work. The key factors responsible for the formation of the wear particles are identified, and their mutual influence is studied. That permits prediction of the wear at the wheels’ contact surface in different operating position. The wear of the contact surface is shown to be localized at the recess. The wear resistance of the contact surface may be increased by local laser treatment.