Application of an alternative current in the processing of cobalt-containing nickel-based alloys

The versions of electrochemical processing of multialloyed nickel-based alloys are studied. These are the processing of the compositions (wt %) 57.0–70.0 Ni, 5.0–10.5 Co, 8.0–20.0 Cr, 1.2–5.0 Mo, 5.0–11.0 W, 2.0–2.9 Ti, 0.8–1.2 Nb, and 5.1–6.0 Al using an industrial-frequency alternating current and sulfuric acid electrolytes, namely, the dissolution of Ni-(10.0–15.0 wt %) Co alloys resulting from primary pyrometallurgical refining and direct dissolution. The rates of electrochemical dissolution of multialloyed nickel-based alloys under the action of a direct current and an industrial frequency (50 Hz) alternating current and the current efficiencies of the processes as functions of the temperatures and concentrations of sulfuric acid in electrolytes are compared. The optimum conditions of alloy dissolution are determined, and large laboratory studies are performed. A principal scheme of ac processing of the alloys is suggested.     

Production of high-strength tubes made of steels of type 15GFB

A unit for making L-class high-strength pump-compressor tubing composed of low-carbon, low-alloy steels of type 15GFB is now being used on the 140 mill in the tube-rolling shop at the Rustavi Metallurgical Plant. The steel 15GFB pump-compressor tubing made by the technology that was developed has the following service properties: σ_y = 630–670 N/mm², σ_u = 730–780 N/mm², δ = 18–22%, ψ = 55–60%, KCU = 1.6–2.2 MJ/m². The percentage of ductile fracture at room temperature is 85–95%. __________ Translated from Metallurg, No. 1, pp. 79–80, January, 2006.     

Magnesiothermal Synthesis and Consolidation of the Multicomponent Powder Ceramics in the Zr–Si–Mo–B System

This work is devoted to the fabrication of ZrB2–ZrSi2–MoSi2-based composite powder ceramics by self-propagating high-temperature synthesis (SHS) according to the scheme of magnesium thermal reduction from oxide feedstock and its subsequent hot-pressing (HP) consolidation. The combustion of reaction mixtures has rather high adiabatic temperatures in a range of 2060–2120 K and burning rates in a range of 8.3–9.4 g/s. The end product yield of the magnesiothermal reduction is 34–38%. The resulting powder contains 13–47% ZrB2, 21–70% ZrSi2, 2–32% ZrSi, and 10–18% MoSi2, depending on the composition of the initial reaction mixture; has high structural homogeneity; and consists of composite polyhedral particles with an average size on the order of 8 μm. The structure of ceramics consolidated by HP from the SHS powder is homogeneous and includes needle ZrB2 grains distributed in the ZrSi2 matrix, MoSi2 inclusions of various morphologies, and inclusions of ZrSiO4 silicate distributed over the ZrSi2 grain boundaries. The HP-formed samples have a high degree of homogeneity of the chemical composition and residual porosity of 2.5–7.4%.     

Zirconium alloys produced from far eastern minerals

The zirconium alloy produced from zirconium concentrate by the electroslag method contains 27–35% Si, 19–38% Zr, 0.3–0.5% W, 3–6% Al, 2–5% Mg, and 0.1% Ca; the remainder is iron. This alloy increases the impact strength of steel by 30–70%, reduces the chill blemishing, and improves the strength of iron castings.     

Use of powders of the tungsten—Rhenium alloys for the preparation of impregnated cathode skeletons. II. Emission capabilities of barium containing impregnated cathodes with tungsten—Rhenium alloy skeletons

The dependence of the emission properties of barium-containing impregnated cathodes on the rhenium content, phase composition, and pore structure of the metallic skeleton was studied. Skeletons were prepared from mixtures of elemental W and Re powders, as well as from W—Re alloy powders. The lowest work function (π(1300 K)=1.97–1.99 eV) was observed in cathodes containing 50–80 mass % Re. The use of W—Re alloy powders with additions of highly dispersed aluminum oxide for the preparation of skeletons increased the lifetime of impregnated cathodes by 2–2.5 times. Such cathodes possessed a stable and uniform grain structure which was resistant to recrystallization and grain growth, thus they had a stable skeleton structure. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 25–30, January–February, 1999.     

Behavior of multilayer steel-bronze composites on frictional loading

Tribological aspects are examined for layered composites made by consolidation. Dry friction tests at sliding speeds of 1.6–4.3 m/sec show that this multilayer antifriction material is better by 1–2 orders of magnitude in wear resistance than the initial material. The multilayer composite can withstand a load increased by an order of magnitude without losing its viability under the conditions of surface-structure adaptation. Deceased. Translated from Poroshkovaya Metallurgiya, Nos, 1–2(411), pp. 38–44, January–February, 2000.     

Heap leaching of copper from the ores of Volkovskoe deposit

Heap leaching of oxidized, complex, and waste copper ores of the Volkovskoe deposit is considered. Based on the results of an investigation, the preliminary granulation of milled ore with sulfuric acid (25–75 kg/t ore) is recommended. Introduction of this procedure leads to a decrease in the leaching time by 15–30% and allows one to obtain solutions more concentrated by copper. For 90–100 days, the recovery of copper into the solution amounted to 65–72% for the waste ore, 76–78% for the oxidized ore, and 46–50% for the complex ore. An increase in leaching time leads to an increase in the recovery of copper from all types of ores.     

Thermodynamic properties of calcium hexaboride

The temperature dependence of the heat capacity of CaB₆ in the range 20–2500 K was calculated. The calculated results were confirmed by experimental measurements in the range 198–673 K, and standard enthalpy and entropy values were calculated. A recommended standard enthalpy of formation of CaB₆ was obtained from data in the literature. Equations for the thermodynamic functions of CaB₆ in the range 298.15–2500 K were obtained, which are suitable for the thermodynamic analysis of processes involving calcium hexaboride. Institute for Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 63–66, July–August, 1997.     

Effect of carbon on volume changes during the sintering of an iron-chromium material

The effect of carbon added in the form of either cast-iron powder or graphite on the sinterability of chromium steel was investigated. The growth and instability of volume change during sintering produced by cast-iron additions was explained as a result of a thermally activated after-effect in the solid phase, and the formation of FeCr₂O₄ around particles of Kh30. Substitution of graphite for cast iron in the powder charge prevented oxidation of the chromium-rich particles, and resulted in low and stable shrinkage (0.1–0.8%) after sintering in the range 750–1250°C. Scatter in the degree of volume change was reduced from 1.5–2.0 to 0.1–0.3%. Iron-chromium material obtained with the use of graphite had improved strength properties as well as high produceability. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 38–42, May–June, 1998     

Study of a blast-furnace smelting technology which involves the injection of pulverized-coal fuel, natural gas, and an oxygen-enriched blast into the hearth

Studies were made of features of a blast-furnace smelting technology that involves the injection of natural gas (NG), oxygen (O₂) and pulverized-coal fuel (PCF) into the hearth. The technology has been implemented in the compensation and overcompensation regimes, which has made it possible to maintain or improve the gasdynamics of the furnace, the conditions for the reduction of iron oxides, the heating of the charge, and PCF combustion in the tuyere zone as PCF consumption is increased and coke use is decreased. Under the given conditions, with the blast having an oxygen content of 25.64–25.7%, the hearth injection of 131–138 kg PCF and 65–69 m³ NG for each ton of pig iron has made it possible to reduce coke consumption by 171–185 kg/ton pig (30.2–32.7%), reduce the consumption of comparison fuel by 36–37 kg/ton (5.2–5.3%), and lower the production cost of the pig iron by 43–49 hryvnas/ton (3.7–6.4%). Here, furnace productivity has increased 3.8–6.5%, while the quality of the conversion pig iron remains the same as before. Measures are being implemented to further increase the level and efficiency of PCF use. __________ Translated from Metallurg, No. 5, pp. 41–44, May, 2006.     

Phase equilibria in titanium-rich alloys of the Ti — Fe — Nb — Al system

Isothermal cross sections at temperatures of 750°C and 550°C of the phase diagram of the quaternary system Ti — Fe — Nb — Al in the region of titanium-rich alloys for a constant aluminum content of 5 mass % were plotted using metallography, x-ray diffraction, and local x-ray spectral analysis. In the temperature range 550–750°C in alloys with 5 mass % aluminum, the maximum solubility of iron in α-titanium reaches ∼2 mass % for a niobium content of 3 ± 0.5 mass %. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(412), pp. 27–32, March–April, 2000.     

Thermodynamic Properties and Phase Equilibria of Nd–Ni Alloys

Isoperibolic calorimetry has been used for the first time to determine the mixing enthalpies of binary Nd–Ni liquid alloys in the range 0 < xNi < 0.5 at 1733 K and range 0.55< xNi < 1 at 1773 K. The binary Nd–Ni melts are characterized by significant negative mixing enthalpies with a minimum of –33.9 ± 0.8 kJ/mole at xNi = 0.63 and 1750 K. In the temperature range studied (1733–1773 K), the mixing enthalpies of the melts are described by polynomial ΔH = xNi (1 – xNi )× × (–75.32 – 103.41 xNi + 273.45$$ {x}_{Ni}^2 $$ – 817.02$$ {x}_{Ni}^3 $$ +548.58$$ {x}_{Ni}^4 $$). The ideal associated solution (IAS) model was used to calculate the activities of components, molar fractions of associates, Gibbs energies, and mixing entropies using our ΔH and $$ \varDelta \overline{H}i $$ and literature data on the formation enthalpy of nickelides and the Nd–Ni phase diagram. All intermediate phases were considered stoichiometric, with zero excess heat capacity. Five associates were selected for the calculation: Nd2Ni, NdNi, NdNi2, NdNi3, and NdNi5. Most of them agree in composition with the intermetallides in this system. Only one of them does not exist in solid state. This is associate Nd2Ni, whose composition is close to that of the Nd7Ni3 intermetallide. The activities of the Nd–Ni melt components show high negative deviations from ideal solutions. Associates of simplest composition, NdNi and NdNi2, are predominant in the melts. The mixing entropies of Nd–Ni liquid alloys are negative (minimum value is close to –6.4 J/mole · K). All our thermodynamic properties indicate that there is strong energy of interaction between Ni and Nd. The liquidus curves of the Nd–Ni system were calculated using the IAS model parameters.     

Effect of Phase Composition on Magnetoresistive Properties of LaMnO3+x

We have studied the magnetoresistivity, thermoelectric power, and magnetic susceptibility of lanthanum manganite LaMnO_3+x with different γ-Mn₂O₃ contents at 77–300 K. The specimens were obtained by high-temperature direct synthesis of lanthanum and manganese oxides. For all the specimens, we established ferromagnetic ordering with Curie point 220–245 K, accompanied by appearance of negative magnetoresistivity, catastrophic growth of magnetic susceptibility, and semiconductor conductivity. The maximum negative magnetoresistivity (δ_H ≈ −13%) is characteristic for two-phase samples with the lowest oxygen content. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 87–93, May–June, 2005.     

Phase equilibria in vanadium-rich alloys of the V-Ni-Al system

Vanadium-rich alloys of the V-Ni-Al system were studied by the methods of metallographic, x-ray diffraction, and electron beam microprobe analysis. The boundaries of the phases, and the vertices of the conoidal triangle αβσ, in the vanadium corne, of the 1200°C isothermal section were determined. The maximum solubility of aluminum in the σ-phase is 6 at. %. The homogeneity range of the NiAl-based β-phase is very broad; the maximum solubility of vanadium in β reaches 41.5 at. %. The maximum solubility of nickel in the vanadium solid solution is 25 at. %. Alloys containing 15–20 % Al and 20–30% Ni exhibit a tendency to dispersion haraen and, therefore, might serve as a basis for the development of a new generation of radiation-resistant materials. Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 43–47, July–August, 1997.     

Thermodynamic analysis of the reaction of titanium with boron carbide in a self-propagating high-temperature synthesis regime

Adiabatic temperatures, thermal characteristics, and the concentration of reaction products in the system Ti−B₄C containing 1–99 mass % B₄C are determined by thermodynamic analysis using the ASTRA package of programs. In order to prepare alloys of titanium with titanium boride and titanium carbide in a self-propagating high-temperature synthesis regime a mixture with 10–13 mass % B₄C is recommended, and for alloys of boron carbide with titanium carbide a mixture containing 53–70 mass % B₄C is recommended. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 72–76, March–April, 1999.     

Current state of development of new ceramic materials (review of foreign literature)

The current state of development of advanced ceramic materials abroad is reviewed. The volume of production of powders and parts from advanced ceramics in the world, North America, Japan, and Western Europe for 1989–1995, and the structure of their application are shown. Prospects for advanced ceramics development up to the year 2000 are discussed. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 101–113, January–February, 1999.     

Thermodynamic properties of scandium-copper compounds

We have determined the Gibbs energy, the enthalpy, and the entropy of formation for the compounds ScCu₄, ScCu₂, and ScCu by measuring the emf of galvanic cells in the temperature range 845–980 K. We compared the experimental results obtained with known literature data. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 87–91, January–February, 2006.     

Preparation and properties of oxide films of the rare earth metals

The properties of films of rare earth metal oxides obtained by evaporation of the metal in an oxygen atmosphere are given. The deposits were highly dispersed and crystallized with a cubic type-Mn₂O₃ structure. The data obtained include: width of the forbidden band (4–6 eV), refractive index (1.89–2.05), specific electrical resistance (10¹⁴–10¹⁵ ω·cm), breakdown voltage (10⁶–10⁷ V/cm), etc. It is shown that films of REM oxides are promising as passive elements of microcircuits, transparent coatings, temperature and heat-flow sensors. These examples by far do not exhaust the possibilities for use of such films. Materials Science Institute. Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 107–111, January–February, 1998.     

Laws of capillary transport in porous materials prepared from titanium alloy VT6 fibers

A study was made of the kinetics of capillary absorption of ethanol in highly porous (70–75%) materials prepared from discrete fibers of titanium alloy VT6 (specimen dimensions 330×20×(0.4–1.3) mm). The fibers, 3 mm in length and 20–140 μm in diameter, were obtained by rapid solidification from the melt. Capillary transport against the force of gravity up to the equilibrium height of capillary rise was investigated in an atmosphere of saturated ethanol vapor. Experimental data on the rate of absorption were analyzed with reference to the properties of the pore space structure—effective pore size, tortuosity of the pore channels, and free surface area. The laws of capillary transport of ethanol in porous materials composed of titanium alloy VT6 fibers, discrete copper fibers, and grade VTEM-2 titanium powder were compared. It was shown that, with regard to the speed of absorption, the advantage of fiber materials over those made from powder is attributable to the less convoluted pore channels in the former. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 67–74, January–February. 1997.     

Developing and mastering a technology for making steel with a sulfur content no greater than 15 ppm

The converter shop at the Azovstal’ combine has developed and successfully introduced a technology for making steel that contains no more than 15 ppm sulfur. The combine has already produced commercial batches of tube steel with a maximum sulfur content of 6–15 ppm. Reducing carbon content from 0.10–0.12 to 0.07–0.08% and lowering sulfur content from 40–70 ppm to 6–15 ppm have improved the quality of the metal of the slabs and rolled products made by the combine. Among these improvements: a decrease in axial porosity and axial segregation in the slabs, an improvement in the ductility characteristics of the rolled metal, a reduction in the degree of contamination of plate metal by nonmetallic inclusions, and a decrease in the incidence of plate rejection in ultrasonic tests. __________ Translated from Metallurg, No. 3, pp. 46–49, March, 2006.