Stabilization of Self-slaking Slags from Ferroalloy Production

In this study, the process of stabilization for highly basic self-slaking slags of ferroalloy production by various boron-containing materials were studied: tincalconite, colemanite, and ulexite (produced in Turkey). The viscosities and temperatures of crystallization for the initial boron-containing materials are determined. Under laboratory conditions, high-base slag melts were treated with boron-containing materials to obtain slags containing 0.25 and 0.5% B2О3. It was shown that the addition of boric anhydride to the studied slag melts extends the homogeneous-liquid state interval and reduces their viscosity by 1.2–1.6 times, therefore B2О3can be used as a tool for controlling slag mobility in industrial conditions. The industrial tests were conducted to stabilize the slag of low-carbon ferrochrome using powdered calcined, briquetted, and fused colemanite. After treatment, slags contained 43–47% CaO, 0.18–0.45% B2О3. The results of pilot-industrial experiments show that all applied boron-containing materials ensure slag stabilization and differ only in the degree of boron recovery. Fused colemanite showed the highest results in the recovery of B2О3(up to 98%), a commercial product was obtained which fully complies according to the technical characteristics with the requirements of Specification TU 0798-69-00186499-2014 “Crushed stone and sand from ferroalloy slags. Technical conditions.” Keywords: ferroalloy, slag, self-slaking slag, stabilization, boron, two-calcium silicat

The Reduction of Boron By Silicothermal Method

Thermodynamic modeling (TM) of the boron reduction process from the CaO–SiO2– MgO–B2O3 oxide system by silicon of ferrosilicon of FeSi65 and FeSi75 grades has been carried out. TM is made using the HSC 6.12 Chemistry software package developed by Outokumpu Research Oy (Finland). The equilibrium composition of oxide CaO-SiO2-MgO-B2O3 and metallic Si-Al-Fe systems was determined using the Equilibrium Compositions module in a given temperature range of 1400–1700∘C and a gas phase pressure of 1 atm. The effect of silicon of ferrosilicon grades (FeSi65 and FeSi75) on the degree of boron reduction (

Multiple stars: Physics vs. dynamics

We review physical and dynamical parameters of multiple stars. Possible scenaria of multiple star formation are discussed: their birth in dense cloud cores and the decay of small stellar groups and clusters. We compare physical and dynamical features of simulated multiple stars formed by these processes with the actual multiple stars. Multiplicity function, their period, eccentricity and mass ratio distributions, hierarchy of the structures are analysed. Also we discuss multiple systems where the apparent ages of the components are different. Such diferences can be explained by poor evolutionary tracks for low-mass stars, by formation of such systems by capture or by merging of components during dynamical evolution of multiple stars. © 2008 Springer-Verlag Berlin Heidelberg

Dynamical stability of the quadruple systems HD 68255/6/7 and HD 76644

We analyze the dynamical stability of the hierarchical quadruple systems HD 68255/6/7 and HD 76644 via numerical integration of the equations of motion of the four-body problem, with a chainlike regularization of close stellar interactions. The observational errors were taken into account using Monte Carlo simulations, assuming that they possessed a Gaussian distribution. HD 68255/6/7 is probably stable, while HD 76644 is unstable with a probability exceeding 0.97 and with a disruption time of no more than 105 years. The influence of the observational errors and possible scenarios for the formation of unstable multiple stars are discussed. © Pleiades Publishing, Inc., 2006

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

Development of the New Method for Oxidized Nickel Ore Processing

In modern conditions of sharp fluctuations in nickel prices on world markets, the problem of profitability of processing Russian poor oxidized nickel ores (ONO) has arisen. As an alternative to the previously existing in Russia, a sulphidation-reducing smelting on a matte, a hydro-pyrometallurgical method has been proposed for the preparation of complex nickel-, chromium-, manganese-containing ferroalloys. At the first stage, hydrolytic precipitation (with sodium hydroxide) is considered as a method of processing production solutions from heap leaching of ONO. It is established that at pH = 5.5, Al is completely removed in the precipitate as hydroxide. After washing from impurities and calcining, a concentrate containing 50 wt.% Al was obtained. At the second stage, at pH = 9.5, more than 99% of nickel and cobalt oxides, as well as 92% oxide concentrate contains, by weight. %: 67 NiO; 3 CoO; 20 MnO; 9 MgO; 0,2 S. At the third stage, a pyrometallurgical method for smelting complex ferroalloys of the Fe-Ni-Cr- Mn-Si system using refractory ferrosilicochrome as a reducing agent is proposed for the processing of nickel-containing concentrate. The scheme of hydro pyrometallurgical method of ONO processing includes: crushing, heap leaching, hydrolytic precipitation to obtain an aluminum-cobalt and nickel concentrates, silicothermic smelting to obtain complex nickel, chromium, manganese ferroalloys, for smelting of suitable stainless steels. Keywords: oxidized nickel ores, nickel, cobalt, manganese, leaching, precipitation, roasting, metallotherm

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

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