Influence of deformation on the structure and mechanical and corrosion properties of high-nitrogen austenitic 07Kh16AG13M3 steel

The correlation has been studied between the structure of a high-nitrogen austenitic Cr-Mn-N steel formed in the process of combined hardening treatment, including cold plastic deformation (CPD), and its mechanical and corrosion properties. The structure and properties of commercial high-nitrogen (0.8% N) 07Kh16AG13M3 steel is analyzed after rolling by CPD and aging at 500 and 800°C. It is shown that CPD of the steel occurs by dislocation slip and deformation twinning. Deformation twinning and also high resistance of austenite to martensitic transformations at true strains of 0.2 and 0.4 determine the high plasticity of the steel. The contribution of the structure imperfection parameters to the broadening of the austenite lines during CPD is estimated by X-ray diffraction. The main hardening factor is stated to be lattice microdistortions. Transmission electron microscopy study shows that heating of the deformed steel to 500°C leads to the formation of the intermediate CrN phase by a homogeneous mechanism, and the intermtallic χ phase forms along the austenite grain boundaries in the case of heating at 800°C. After hardening by all investigated technological schemes, exception for aging at 800°C, the steel does not undergo pitting corrosion and is slightly prone to a stress corrosion cracking during static bending tests, while aging at 800°C causes pitting corrosion at a pitting formation potential Epf = -0.25 V. © 2013 Pleiades Publishing, Ltd

Local Corrosion of CR-Martensitic Steel Alloyed with Carbon and Nitrogen

The structure and mechanical properties of high-nitrogen martensitic steel 30X15AM were investigated. The tendency of steel to pitting and intergranular corrosion was studied by the method of metallographic analysis of the surface subjected to corrosion using the SIAMS 800 Photolab program in comparison with standard electrochemical methods. Both methods showed high resistance of steel to these types of local corrosion.Исследовали структуру и механические свойства высокоазотистой мартенситной стали 30Х15АМ. Склонность стали к питтинговой и межкристаллитной коррозии изучали методом металлографического анализа поверхности, подвергнутой коррозии, с использованием программы SIAMS 800 Photolab в сравнении со стандартными электрохимическими методами. Обе методики показали высокую стойкость стали к данным видам локальной коррозии

Re-establishing glacier monitoring in Kyrgyzstan and Uzbekistan, Central Asia

Glacier mass loss is among the clearest indicators of atmospheric warming. The observation of these changes is one of the major objectives of the international climate monitoring strategy developed by the Global Climate Observing System (GCOS). Long-term glacier mass balance measurements are furthermore the basis for calibrating and validating models simulating future runoff of glacierised catchments. This is essential for Central Asia, which is one of the driest continental regions of the Northern Hemisphere. In the highly populated regions, water shortage due to decreased glacierisation potentially leads to pronounced political instability, drastic ecological changes and endangered food security. As a consequence of the collapse of the former Soviet Union, however, many valuable glacier monitoring sites in the Tien Shan and Pamir Mountains were abandoned. In recent years, multinational actors have re-established a set of important in situ measuring sites to continue the invaluable long-term data series. This paper introduces the applied monitoring strategy for selected glaciers in the Kyrgyz and Uzbek Tien Shan and Pamir, highlights the existing and the new measurements on these glaciers, and presents an example for how the old and new data can be combined to establish multi-decadal mass balance time series. This is crucial for understanding the impact of climate change on glaciers in this region

Snow-cover reconstruction methodology for mountainous regions based on historic in situ observations and recent remote sensing data

Spatially distributed snow-cover extent can be derived from remote sensing data with good accuracy. However, such data are available for recent decades only, after satellite missions with proper snow detection capabilities were launched. Yet, longer time series of snow-cover area are usually required, e.g., for hydrological model calibration or water availability assessment in the past. We present a methodology to reconstruct historical snow coverage using recently available remote sensing data and long-term point observations of snow depth from existing meteorological stations. The methodology is mainly based on correlations between station records and spatial snow-cover patterns. Additionally, topography and temporal persistence of snow patterns are taken into account. The methodology was applied to the Zerafshan River basin in Central Asia – a very data-sparse region. Reconstructed snow cover was cross validated against independent remote sensing data and shows an accuracy of about 85%. The methodology can be used in mountainous regions to overcome the data gap for earlier decades when the availability of remote sensing snow-cover data was strongly limited

Structure and mechanical and corrosion properties of new high-nitrogen Cr-Mn steels containing molybdenum

The structure, mechanical properties, and pitting corrosion of nickel-free high-nitrogen (0.8% N) austenitic 06Kh18AG19M2 and 07Kh16AG13M3 steels have been studied in various structural states obtained after hot deformation, quenching, and tempering at 300 and 500°C. Both steels are shown to be resistant to the γ → α and γ → e{open} martensite transformations irrespective of the decomposition of a γ solid solution (06Kh18AG19M2 steel). Austenite of the steel with 19 wt% Mn shows lower resistance to recrystallization, which provides its higher plasticity (δ 5) and fracture toughness at a lower strength as compared to the steel with 13 wt% Mn. Electrochemical studies of the steels tempered at 300 and 500°C show that they are in a stable passive state during tests in a 3.5% NaCl solution and have high pitting resistance up to a potential E pf = 1.3-1.4 V, which is higher than that in 12Kh18N10T steel. In the quenched state, the passive state is instable but pitting formation potentials E pf retain their values. In all steels under study, pitting is shown to form predominantly along the grain boundaries of nonrecrystallized austenite. The lowest pitting resistance is demonstrated by the structure with a double grain boundary network that results from incomplete recrystallization at 1100°C and from the existence of initial and recrystallized austenite in the 07Kh16AG13M3 steel. To obtain a set of high mechanical and corrosion properties under given rolling conditions (1200-1150°C), annealing of the steels at temperatures no less than 1150°C (for 1 h) with water quenching and tempering at 500°C for 2 h are recommended. © 2012 Pleiades Publishing, Ltd

Mechanical and magnetic properties of high-nitrogen austenitic steel (HNS) 06H18AG19M2

Submitted by investigating the mechanical properties of focused bend testing of High-nitrogen austenitic steel (HNS) 06H18AG19M2 in air and 3.5% NaCl aqueous solution after hardening from 1150 °C, subsequent aging at 500 and 800 °C and equal channel angular pressing (ECAP) with different degrees of deformation. Also the studies of magnetic properties were conducted after different structural states of steel. It is shown that the steel is paramagnetic regardless of the mode of its processing, the exception is a state after quenching from 1200 ° C, when detected significant spontaneous magnetization of steel in an external magnetic field.Выполнены исследования механических свойств путем испытаний на сосредоточенный изгиб высокоазотистой аустенитной стали (ВАС) 06Х18АГ19М2 на воздухе и в 3,5%-ном водном растворе NaCl после закалки от 1150 °С, последующего старения при 500 и 800 °С, а также равноканального углового прессования (РКУП) с различными степенями деформации. Также проведены магнитные исследования стали в различных структурных состояниях. Показано, что сталь остается парамагнитной независимо от режима обработки, исключение составляет состояние после закалки от 1200 °С, когда обнаруживается значительная спонтанная намагниченность стали во внешнем магнитном поле

Comparison of Adsorption Coefficients of Argon, Krypton, and Xenon on Various Activated Charcoal Grades in Static Conditions

Coefficients of adsorption (Henry’s constants) of noble gases (argon, krypton, xenon) on activated charcoal grades AG-3, VSK-5, SKT-3, NWC 12x40 in the temperature range of 15 °C to 80 °C were determined. Temperature dependence parameters of Henry’s constants were determined with a calculation of isosteric adsorption heat values. The experimental data were used to calculate stationary operating conditions of a radiochromatographic column in NPP’s noble gas delay system. Out of all the studied charcoals, the results show that coconut charcoals VSK-5 and NWC 12x40 have the highest decontamination factor to airflow purification from radioactive noble gases. They far outweigh sulfur–potassium activated peat charcoal SKT-3 used presently at most Russian nuclear power plants. Activated charcoal AG-3 does not ensure the decontamination level required. The results also show that the overall decontamination factor depends heavily on temperature. Precooling gas flow at the adsorber’s input can considerably increase air decontamination factor from radioactive noble gases

Calculation of the Henry’s Constant and the Thickness of the Equilibrium Adsorption Layer of Radon in the Layer-by-Layer Measurement of the Sorbent Activity

The radioactive gas radon is ubiquitous in the environment and is a major contributor to the human inhalation dose. It is the second leading cause of lung cancer after smoking. Radon concentrations are particularly high in the air of radon-hazardous facilities—uranium mines and radioactive waste repositories containing radium. To reduce the dose load on the staff, air in these premises should be continuously or periodically purified of radon. Carbon adsorbers can be successfully used for this purpose. The design of sorption systems requires information on both equilibrium and kinetic parameters of radon dynamic adsorption. The traditional way of obtaining such characteristics of the sorbent is to analyze the breakthrough curves. The present paper proposes a simple alternative method for determining parameters of dynamic radon adsorption (Henry’s constant and equilibrium adsorption layer thickness) from the results of a layer-by-layer gamma-spectrometric measurement of the sorbent. The analytical equation for smooth distribution of radon activity in the sorbent layer is obtained based on equilibrium adsorption layer theory for elute chromatography (pulsed injection of radon into the column). Using the dynamic adsorption of 222Rn on AG-3 activated carbon as an example, both equilibrium (Henry’s constant) and kinetic (thickness of the equilibrium adsorption layer) parameters of the adsorption dynamics were calculated. It was shown that the exposure duration of the column bed in the air flow and superficial gas velocity do not affect the result of the Henry’s constant calculation. The dependence of the equilibrium adsorption layer thickness on the superficial gas velocity over a wide range of values (5–220 cm/min) is described by the van Deemter equation. It was shown that the optimum air flow velocity, which corresponds to the maximum effectiveness of the bed, is 15–30 cm/min. This corresponds to the minimum of the equilibrium adsorption layer thickness (about 0.6 cm). The developed mathematical model makes it easy to define both equilibrium and kinetic parameters of dynamic adsorption of radon based on discrete distribution of its activity over the sections of the adsorption column. These parameters can then be used to calculate and design gas delay systems. It can be useful for studying the sorption capacity of various materials relative to radon