12Kh18N10T Steel Research Articles

Mathematical Modeling of the Corrosion Behavior of Austenitic Steels in Chloride-Containing Media During the Operation of Plate-Like Heat Exchangers

Mathematical models that describe the dependences of the critical temperatures of pitting formation of AISI 304, 08Kh18N10, AISI 321, 12Kh18N10T steels in model circulating waters with pH 4…8 and chloride concentrations from 350 to 600 mg/l on their chemical composition and structure have been developed. They are based on linear squares regressions and a feed-forward neural network for reduced feature numbers. Using the developed mathematical models, it was found that the critical pitting temperatures of these steels increase with an increase in the pH of the circulating water, the number of oxides up to 3.95 μm in size, the average distance between titanium nitrides, the Cr content and a decrease in the concentration of chlorides in the circulating waters, the average distance between oxides and average austenite grain diameter. At the same time, it was found that the geometric dimensions of the steel structure most intensively affect their pitting resistance in circulating waters, and the effect of their chemical composition is minimal and is determined by the amount of Cr, which contributes to an increase in the pitting resistance of steels, probably increasing the solubility of nitrogen in the austenite solid solution. It is proposed to use the developed mathematical models to select the optimal heats of these steels for the production of heat exchangers and predict their pitting resistance during their operation in circulating waters.

Formation of silicated layer of austenitic pipe steel with different pipe sizes

Tubular furnaces of hazardous production facilities are unique technical devices, and serve for open fire heating of various process media to relatively high temperatures. Some of the furnaces, such as pyrolysis furnaces, hydrogen conversions are also reactors that serve to decompose the hydrocarbon feedstock into separate components. The most important element of the structure is a tubular coil. The effect of high temperatures and working media on the coil metal inevitably leads to metal degradation by forming various defects, changing the structure and mechanical properties for the worse. One of the most unfavorable moments is considered saturation of the surface layers of the metal with carbon or another - carburization of the metal. When the metal is carburized, its embrittlement occurs and the probability of brittle destruction increases. All this can lead to frequent shutdown of furnaces for repairs and significant costs. One way to contain the active diffusion of carbon into the metal may be to silicate the surface of the coil elements using different silicating mixtures, since silicon can effectively delay carbon incorporation. In this work, studies are carried out on the peculiarities of the formation of a silicated layer in fragments of pipes with dimensions of 160x6 mm, 32x2 mm, 57x4 mm made of steel 08Kh18N10T depending on the holding time in the silicating mixture.

Investigation of the structure and properties of a fivelayer titanium-steel explosion-welded composite material after technological stages

The paper presents the results of studies of a five-layer composite material consisting of three layers of titanium VT20 alloy and two layers of stainless 08Kh18N10T steel after explosion welding (EW) and subsequent processing, including hot rolling (HR) and heat treatment (HT) at temperatures of 800, 850 and 900 °C with a holding time of 1 to 100 h to form a layered intermetallic composite (LIC), which has a combination of plastic layers of the original alloys and intermetallic interlayers in contact with them, the presence of which provides the necessary strength characteristics at elevated temperatures. The structure, microhardness, and chemical composition of the diffusion zones of the composite were studied using optical and electron microscopy, X-ray spectral and X-ray diffraction analyses. It is shown that, after EW, the joint zones have a characteristic wavy profile with areas of melted and crystallized metal–flashes, which are solid solutions based on titanium, iron, and Cr(Fe)2Ti intermetallic compound. Hot rolling and HT under the specified conditions led to diffusion processes of main steel elements into the titanium alloy, resulting in the formation of diffusion interlayers adjacent to the steel and titanium alloy, the composition and thickness of which depend on temperature and holding time at certain ratios of chemical elements and phase composition.

Oil and gas steels surface hardening investigation by anodic plasma electrolytic treatment

The paper is devoted to research of anodic plasma electrolytic method for hardening steels of various classes, widely used in the oil and gas industry (there were tested such grades of steels, like 20, 09G2S, U10, 18Kh2N4VA, 12Kh18N10T). Hardening was carried out in an electrolyte containing 8% ammonium chloride, 5% glycerol, and 3% carbamide for 3–5 min. Studies have shown that low- and medium-carbon steels form hardened surface layers up to 150–200 micrometers deep from the surface with an increase of microhardness up to 4.66 times, relative to the original structure. High-alloy steels have a smaller hardening zone (up to 70 micrometers) and a smaller increase of microhardness (up to 1.49 times). The wear resistance of treated steels is enhanced from 27.7% (for steel 12Kh18N10T) up to 86.6% (for steel 09G2S) in comparison to their initial state. The investigation of corrosion behavior of samples tested in 5% NaCl solution using potentiodynamic Tafel curves method is showed also the enhance of corrosion resistance of strengthened steels samples by anodic plasma electrolytic treatment in comparison to untreated samples.

Практическое использование результатов исследований технологических процессов формирования твердофазных соединений проволок в контролируемой газовой среде при создании листовых пористых сетчатых материалов с заданными свойствами

A specific feature of the structure-forming elements used for the manufacture of porous mesh materials is a high specific surface area and a complex configuration of wire meshes, which excludes the possibility of using wire cutting for welding. The research shows that cleaning in Freon-113 is an effective way to remove mineral oils, paraffins, fats and some other contaminants from the mesh surface, since this solvent is stable, non-flammable, non-explosive and does not interact with the workpiece material. In addition, improving the quality of mesh cleaning is achieved by superimposing ultrasonic vibrations in the range of 20...40 kHz. The study introduces flow layouts for the porous materials manufacture by pressure welding of wire meshes from steel 12Kh18N10T and titanium alloy VT2. Findings of the research show that welding envelopes of meshes made of steel I2XI8HI0T by rolling in evacuated makes it possible to obtain porous elements with sufficiently high mechanical and technological properties. It is possible to implement this process on any sheet rolling mill, which is its significant advantage. The paper gives the modes of welding by rolling and diffusion welding of meshes in the manufacture of porous materials. Within the study, we developed a mathematical model that makes it possible to predict the ultimate interlaminar strength for given values of technological parameters of the processes for manufacturing sheet blanks. It is proposed to control the interlayer strength by comparing the calculated data and the results of testing the samples for separation in accordance with the developed methodology. It is advisable to evaluate the control of strength, plasticity in the sheet plane and their anisotropy by comparing the calculated data and the results of testing specimens under conditions of biaxial tension, implemented during hydrostatic buckling through a round matrix.

Исследование влияния состава контролируемой газовой среды и температуры на качество твердофазных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials are designed for the manufacture of products with a given shape and size, as well as hydraulic, filtering, thermal and other properties. At the same time, they must have the necessary mechanical and technological properties, which are formed to a large extent by the quality of weld solid-state bonds of mesh wires. Findings of the research that the increase in the strength of wire bonds during manufacture of porous mesh materials is influenced by the conditions for removing oxide layers by means of choosing the optimal protective gas environment and heating temperature during welding. The analysis of the processes occurring at the boundary of the metal–oxide and oxide–gas phases made it possible to establish that, depending on the structure of the alloy, the heating temperature, the composition and partial pressure of the gas protective environment, not only additional oxidation or thinning of the oxide layers but also gas saturation of the work surface are possible. For the manufacture of sizeable sheet porous mesh materials with high accuracy in thickness, the use of welding by rolling in a protective gas environment is the only possible process. Depending on the chemical composition of the wires, it is possible to carry out mesh briquette rolling welding on vacuum rolling mills, in an argon atmosphere of controlled purity and in evacuated envelopes. Within the research, we studied the influence of the composition of the gas environment and the process temperature on the quality of weld bonds and found that it is advisable to manufacture VT2 alloy sheet porous mesh materials by hot rolling in a vacuum mill and in an inert gas environment with a controlled composition. Porous mesh materials made of 12Kh18N10T steel can be made by hot rolling in vacuum envelopes, and products with limited dimensions can be made by diffusion welding. The study also specifies the modes of technological processes for manufacturing porous mesh materials made of VT2 alloy and 12Kh18N10T steel by rolling welding and diffusion welding.

Образование сварных твердофазных соединений проволок при изготовлении пористых сетчатых материалов из стали 12Х18Н10Т

The experience of using turbine blade shells based on porous mesh materials in aerospace products and high-temperature gas turbines has shown that they are subject to destruction when under the influence of pressure fluctuations. So, first of all, fatigue failure occurs, in those permeable shells where there are no high-quality connections of structure-forming elements. It has been established that in diffusion welding and rolling welding, the strength of welded bonds increases with an increase in the process temperature, as well as in the vacuum depth and deformation time in diffusion welding. Research findings show that at strain rates of 10–2…1.0 s–1, the low quality of welded joints is explained by the high deformation resistance of microroughnesses on the contact surfaces of the wires and the low rate of diffusion mass transfer in the connection zone. The study establishes that under the conditions of diffusion and impact welding in vacuum, the formation of a solid-phase joint is possible on the entire surface of the macrocontact. At the same time, in percussion welding, the influence of the temperature value in the investigated interval on the quality of welded bonds is much lower than that for processes with lower loading rates. Practical recommendations are given for determining the optimal modes of wire mesh welding in the manufacture of porous mesh materials made of 12Kh18N10T steel.

Development of Production of Continuous Cast Billets of Grade 08Kh18N10T Steel for Fabricating Hot-Rolled and Pressed Pipes

Development of Production of Continuous Cast Billets of Grade 08Kh18N10T Steel for Fabricating Hot-Rolled and Pressed Pipes

Introduction of tungsten carbide into 08Kh18N10T corrosion-resistant steel and its effect on mechanical properties

Interfacial phenomena and reactions between tungsten semicarbide (W2C) and corrosion-resistant steel melt have been studied using wetting experiments. This process was followed by the method of high­temperature contact heating of W2C substrate and a metal sample made of 08Kh18N10T steel. It was established that wolfram carbide has good indicators of wettability by corrosion-resistant steel, wetting angle is 135 – 145°. Composition of the substrate surface has been studied by electron scanning microscopy to determine composition of reaction products. Analysis of the obtained results allows us to state that content of chemical elements varies over the entire contact area, but pattern of their distribution there is uniform. Due to the obtained data we can make an assumption about the applicability of combination of these components to create dispersed-hardened materials. To this end, experiments have been carried out to produce dispersedly hardened centrifugal cast blanks with various types of casting – horizontal and vertical. To obtain experimental materials, the horizontal and vertical type centrifugal casting was introduced into tungsten semicarbide ingots in an amount of 1 % wt. After producing experimental materials, a number of mechanical properties were studied, such as tensile strength, yield strength and hardness. The experimental results allow us to conclude that the use of dispersed hardening in process of centrifugal casting makes it possible to obtain metal materials with increased mechanical properties. Indicators of ultimate strength increase (for all samples on average) by 2.49 %, yield strength – by 2.27 %, hardness – by 5.02 %, which correlates with the provisions on metals physico-chemical properties when using dispersed hardening technologies.

Influence of Welding Regimes on Structure and Properties of Steel 12KH18N10T Weld Metal in Different Spatial Positions

Influence of Welding Regimes on Structure and Properties of Steel 12KH18N10T Weld Metal in Different Spatial Positions

Research of the Influence of Cutting Conditions on the Temperature Field during Turning

Numerical simulation of the temperature field and parameters of the turning process of workpieces made of 45 and 12Kh18N10T steels is performed. The front angle of the cutter, as well as the coefficients of chip friction on the front surface of the tool μ1, the flank surface on the workpiece μ2, and the coefficient of friction on the yield stress μ were selected as variable parameters. The degree of influence of the variable parameters on the tangential component of the cutting force, the friction force on the front and flank surfaces of the cutting tool, the power of heat sources, contact temperatures and the average temperature of the workpiece is estimated.

Влияние предварительной химической обработки на качество твердофазных сварных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials with an organized structure, stable and reproducible properties are used in the manufacture of filter elements, thermal protection systems, rocket and turbojet engines, and other products with a given set of properties. The interlayer strength of such materials is significantly affected both by the modes of plastic deformation and welding and by the technology of preliminary chemical cleaning of the wire mesh surface. Etching work-pieces in a mixture of inorganic acids and organophosphorus complexones reduces the thickness of oxide films and additionally activates the contact surfaces in the welded joint. The study introduces the etchant solutions for treating VT1-0 titanium and corrosion-resistant 12Kh18N10T steel wires. The solutions increase the strength of the welded joints made by vacuum rolling welding and diffusion welding, compared with similar processes without pretreatment. The study also specifies the modes of technological processes of chemical etching and diffusion welding of 12Kh18N10T steel meshes, which provide maximum interlayer strength.

MANUAL ARGON-ARC WELDING OPTIMIZATION OF DIFFERENT AUSTENITE STEELS 12KH18N10T AND AISI 316

The paper presents the results of testing the tendency to intergranular corrosion of welded joints of dissimilar steels 12Kh18N10T and AISI 316 without heat treatment, as well as after quenching and stabilizing annealing. By welding control samples, optimal parameters of argon-arc welding were determined for pipes with a diameter of 42 mm and a wall thickness of 3.5 mm. A filler wire was selected according to Scheffler diagram.

Two Approaches to the Study of Temperature Effect on the Dissipative Properties of Materials

In order to study the effect of temperature changes on the dissipative properties of materials, two approaches are used. The first approach implies introducing some temperature function under the sign of the integral in the heredity theory equation and simultaneously taking into account the dependence of the elastic modulus on temperature. As a result, based on experimental data on the thermal creep of soils, the expression for determining the hysteresis energy losses under the periodic voltage changes was obtained depending on temperature changes.According to the second approach, the expression for determining the hysteresis energy losses under isothermal conditions at different temperatures was obtained by introducing into the heredity theory equation an approximation of the experimental dependences of instantaneous deformation and temperature creep parameters for steel Kh18 N10T.

Influence of microcracks on Poisson's ratio during plastic deformation of austenitic steel

We researched the influence of damage accumulation on the Poisson's ratio measured by echo-pulse acoustic method during plastic deformation of 12Kh18N10T steel. On the basis of the obtained experimental data we calculated the partial contributions to the change in the Poisson's ratio of damage accumulation and formation of the strain induced martensite phase. The characteristics of stable cracks forming near strain-induced martensite particles at small degrees of plastic strain have been analyzed by computer simulation. The theoretical dependence of the change in the Poisson's ratio due to crack formation during plastic deformation has been constructed. A good agreement between the experimental data and theoretical calculations has been obtained. Keywords: plastic deformation, austenitic steel, Poisson's ratio, martensite transformation, dislocation, mesodefect, configurational force method.

Влияние микротрещин на коэффициент Пуассона при пластическом деформировании аустенитной стали

We researched the influence of damage accumulation on the Poisson's ratio measured by echo-pulse acoustic method during plastic deformation of 12Kh18N10T steel. On the basis of the obtained experimental data we calculated the partial contributions to the change in the Poisson's ratio of damage accumulation and separation of the strain induced martensite phase. The characteristics of stable cracks forming near strain martensite particles at small degrees of plastic strain have been analyzed by computer simulation. The theoretical dependence of the change in the Poisson's ratio due to crack formation during plastic deformation has been constructed. A good agreement between the experimental data and theoretical calculations has been obtained.

Mechanical properties and microstructure of 12Kh18N10T steel obtained by selective laser melting

Stainless 12Kh18N10Т steel powder with dispersion of 25...68 µm and experimental samples obtained on its basis by selective laser melting (SLP) are studied. The microstructure of the samples is characterized by continuity, absence of pores and cracks and was a solid solution of austenite. The microhardness of samples obtained from the powder by the SLP method is higher than that of a standard compact alloy, the time resistance and elongation are 665 MPa and 53 % respectively. The surface of the fractures of the samples is characterized by a pronounced viscous type.

Study of wear characteristics under conditions of dry sliding friction of 08Kh18N10T steel after electrolysis-free boriding

Effect of liquid electrolysis-free boriding on tribotechnical characteristics of 08Kh18N10Т steel is studied. It is established that after boriding at temperature 900 °С and 5 h soaking it is formed a boride two-phase layer with thickness of 30...35 microns and transition zone with thickness of 10 microns. The microhardness in FeB and Fe2B phases is 2000...2100 and 1800...1900 HV 0.1 respectively. The wear tests under dry friction conditions showed that coefficient of friction for specimens made of 08Kh18N10Т steel without treatment and with boriding in pair with counterbody made of ShKh15 steel is 0.83 and 0.85 respectively. At the same time, the wear intensity of samples with boration is an order of magnitude less than that of samples without treatment, and on average is 7.7 · 10–6 mm3 /(H · m) instead of 8.5 · 10–5 mm3 /(H · m). The average depth of the wear track of the sample with boriding is 5 times less than that of the sample without treatment.

Quantitative analysis of degradation of P-1-201 coil structure made of steel 08Kh18N10T

Structural changes in materials during long-term operation in a stressed state and temperature exposure play a key role in the softening of the material, and, consequently, in ensuring the service life of technological pipelines and vessels of oil refining equipment and main pipelines.

Разработка технологии тонкослойного лазерного модифицирования хромоникелевой стали 12Х18Н10Т

Разработка технологии тонкослойного лазерного модифицирования хромоникелевой стали 12Х18Н10Т