Steel Micro-alloying with Boron: A Perspective Direction to Reduce the Consumption of Manganese Ferroalloys

Manganese ferroalloys occupy a strategically important place in the total production of ferroalloys, since no steel grade can be made without the manganese addition. Today, the metallurgical complex of Russia is fully dependent on imports of manganese products (raw ore and ferroalloys), so special attention should be paid to the issues of more rational use of manganese. In particular, one should more widely use the methods of direct micro-alloying of steel with manganese in steel-smelting units and ladle-furnaces unit (LFU) and expand the range of high-strength steel with reduced manganese content, micro-alloyed with high-performance elements. Among the micro-alloying elements, a special place is occupied by boron. Its introduction into the metal in the amount of 0.001–0.005% makes it possible to save expensive and scarce alloying elements, in particular manganese, and to provide an increase in the strength of steel without reducing ductility. The results of the studies of the physicochemical properties of slags of the system CaO–SiO2–B2O3–Al2O3–MgO had formed the basis for the technology development for the formation of basic boron-containing slags, that implementation at the LFU in the converter shop of JSC “ArcelorMittal Temirtau” provided the smelting of boron-containing steel economically doped with manganese with low-content of sulfur and high strength and plastic properties. The developed technology provided, depending on the steel grade, a boron content of 0.001–0.008% by weight, low concentration of sulfur in the metal, not more than 0.004–0.014% by weight, and reducing the manganese ferroalloys consumption from 0.5 to 1.4 kg/ton of steel. Keywords: pipe steel, manganese, sulfur, boron, mechanical properties, structur

Study of the Process of Alloying Steel By Nitrated Chromium

Experimental investigation of process of steel alloying by nitrated chromium was carried out. As raw material for metal-melt treatment, the steel containing 20.3% Cr; 11.2% Mn; 7.1% Ni; 1.46% Mo; 0.33% Si; and 0.05% C was used. As-cast samples of nitrated chromium (ФХH10 and ФХH20 grades) were used as alloying additives. The compositions of grades are 85.7% Cr; 8.0% N, and 73.9% Cr; 16.1% N, respectively. Experiments were carried out in high-temperature laboratory unit at 1500∘C. It was found that the degree of nitrogen transfer into steel reaches up to 84% at the application of as-cast specimen of nitrated chromium containing 8% of nitrogen and 1 min exposure time after addition to ferroalloy. Further high-temperature soaking of nitrated steel causes a dropdown of nitrogen concentration due to thermal dissociation of existed nitrogen-containing compounds in the melt and exhalation in gas phase. This prevents nitrogen transfer into the steel. It was demonstrated a possibility in principle of obtaining of chrome-manganese steel containing about 0.4–0.6% of nitrogen at melt alloying by nitrated chromium in air atmosphere at exposure time up to 15 min. Keywords: metallurgy, nitrogen, chromium, steel, digestion degree, physicochemical characteristic

Recycling of Waste Slag Upon Production of Manganese Ferroalloys

The mineral resources base of manganese ores is sufficiently large in Russia. However, their mining capacity is almost absent. This is due to the low quality of domestic manganese ores and the high content of phosphorus. To date, Russia has been obliged to import the commercial manganese ore, manganese-containing ferroalloys, metallic manganese, and manganese dioxide. To produce the high-carbon ferromanganese the composition of charge was developed. The optimum variant was that where 10–15% of manganese-containing raw materials were changed for waste slag. In this case, the phosphorus content in the high-carbon ferromanganese is lower by approximately 20 rel. % in comparison with the production of ferromanganese only from the manganese-containing raw materials. About 50–60 rel. % of manganese can be extracted from the waste slag of silicon-thermal production. To produce the hot metal, the composition of iron-bearing burden material was developed. The optimum variant was that where 100% of manganese raw materials were changed for the waste slag. In this case, upon production of hot metal, the specific consumptions of manganese raw materials and limestone were decreased by 100 and 20%, respectively. The phosphorus concentration in metal was lower by about 10 rel. % as compared to the production of hot metal only from the manganese raw materials. Up to 55% of manganese can be extracted from the waste slag of silicothermic production, which is irretrievably lost at present. Keywords: manganese ferroalloys, manganese-containing raw materials, waste slag, hot meta

Contribution of Hardening Mechanism to VVER-1000 RPV Welds Flux Effect

Systematic differences in the radiation embrittlement kinetics of steels irradiated with different fluxes requires a clear understanding and assessment of the mechanisms responsible for the flux effect. This paper presents results of research of hardening mechanism contribution to flux effect of VVER-1000 reactor pressure vessel (RPV) welds. Transmission electron microscopy (TEM) and atom probe tomography (APT) investigations were carried out. Studies of hardening phases of RPV-steel (VVER-1000) after accelerated irradiation allowed to estimate the contribution of the hardening mechanism to flux effect. Keywords: reactor pressure vessel, hardening mechanism, flux effec

РАВНОВЕСНОЕ РАСПРЕДЕЛЕНИЕ БОРА МЕЖДУ МЕТАЛЛОМ СИСТЕМЫ FE - C - SI - AL И БОРСОДЕРЖАЩИМ ШЛАКОМ

Using the HSC 6.1 Chemistry software package (Outokumpu) and simplex-lattice planning, the thermodynamic modeling of the boron equilibrium distribution between iron containing 0.2 % of C, 0.35 % of Si, 0.028 % of Al (in the terms and hereinafter indicated mass. %) and slag of the system СаО – SiO2 – Аl2O3 – 8 % МgO – 4 % В2O3 was carried out in a wide range of chemical composition and at temperatures of 1550 °С and 1600 °С. Adequate mathematical models in the form of III degree polynomial obtained for each temperature, describes the equilibrium distribution of boron between slag and metal depending on the slag composition. Mathematical modeling results are presented graphically in the form of diagrams of composition – boron equilibrium distribution. It is shown that slag basicity affects on the boron distribution coefficient. Thus, increasing the slag basicity from 5 to 8 at temperature of 1550 °С reduces the boron distribution coefficient from 160 to 120 and, as a consequence, increase the boron content in the metal from 0.021 % at LB = 159 to 0.026 % at LB = 121, that is, growth slag basicity is beneficial to the development of boron recovery process. The positive effect of the slag basicity on boron recovery process in the researched range of the chemical composition can be explained according to the slag phase composition and thermodynamics of boron reduction reactions. The temperature growth of the metal negatively affects the boron recovery. Equilibrium boron distribution coefficient increases by an average of 10 units with an increase in temperature to 1600 °C. The diagrams contain marked field of slag chemical composition with 53 – 58 % of CaO, 8.5 – 10.5 % of SiO2 and 20 – 27 % of Al2O3, providing boron distribution coefficients at level of 140 – 170 at temperature range of 1550 – 1600 °C and allowing to expect boron concentration in the metal at the level of 0.020 % at LB = 168 % and 0.023 % at LB = 139 at the 4 % of B2O3 in the slag initial. © 2017 National University of Science and Technology MISIS. All rights reserved

Search for signatures of reflected light from the exoplanet HD 189733b by the method of residual dynamical spectra

© 2015, Pleiades Publishing, Ltd. The goal of the present study is the development and testing of a method for spectral detection of the light of host stars reflected from their exoplanets. The presented method is based on the analysis of dynamical spectra, which make it possible to obtain high signal-to-noise residual spectra after host star spectrum deduction. These residual spectra contain information on the light reflected from an exoplanet and on its albedo. The first results of such research for the exoplanet HD 189733b are presented in the paper. We obtained a series of a few dozens moderate-resolution spectra of the host star HD 189733. Individual spectra have a high signal-to-noise ratio (≈700) and cover a considerable part of the complete orbital cycle of the exoplanet. The use of the developed method allowed us to achieve a characteristic contrast of the reflected light detection at a level of 5 × 10−4 from the continuum. Investigation of the dynamic spectra with this characteristic value as a detection threshold has not revealed obvious evidence of the host star light reflected from the planet. Nevertheless, the obtained threshold is high, which demonstrates the necessity of the development of the method for the exoplanet monitoring studies

Использование математической модели хроматографической колонки для обработки хроматограмм с перекрывающимися пиками

A method is suggested to process overlapping chromatographic peaks with the use of a mathematical model of the chromatographic column. The method enables determining the composition of the mixture to be analyzed even in case of completely overlapping peaks.Предлагается методика обработки неразделенных хроматографических пиков, использующая математическую модель хроматографической колонки. Методика позволяет рассчитать состав исследуемой смеси даже для полностью перекрытых пиков

Выбор разделяющих агентов с помощью газожидкостной хроматографии для экстрактивной ректификации биазеотропной смеси бензол - перфторбензол

Gas-liquid chromatography was used for estimating the selectivity of solvents for the separation of biazeotropic benzene - perfluorobenzene mixture based on extractive rectification.The selected optimal solvents enable two theoretically feasible variants of the mixture separation.Из ряда потенциально эффективных разделяющих агентов для процесса экстрактивной ректификации биазеотропной смеси бензол - перфторбензол с помощью газожидкостной хроматографии проведен отбор максимально селективных разделяющих агентов, которые обеспечивают два теоретически возможных варианта разделения смеси на компоненты

Search for and study of photometric variability in magnetic white dwarfs

© 2017, Pleiades Publishing, Ltd.We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70◦8247 with a likely period from several days to several dozen days and a half-amplitude of about 0.m 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0.m 005, and the likely period of this degenerate star lies in the 10–20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated “magnetic field–rotation period” diagram for the white dwarfs