Vol 62, No 5-6 (2018)

The Aksu Ferrous Alloy Plant is a firm producing high-carbon ferrochrome, manganese, and silicon alloys at a total production volume of over 1 million metric tons/yr. Smelting Shop 1 has six 33-MW RKZ enclosed electric ore-reducing furnaces. Two of the electric manganese-ore smelting furnaces have been affected by gas-treatment deficiencies due to the formation of volatilized finelydispersed wettable dust with high adhesion and cohesion. The dust load on the bag filters is 40 times higher when smelting manganese ore than when smelting chromite ore in similar electric furnaces. The FROP-25300 bag filters currently installed for collection of manganese dust cannot currently ensure that the gas meets design requirements for residual dust content due to the low efficiency of reverseblowdown bag regeneration. For this reason, some of the gas from the electric furnaces escapes as fugitive gas into the shop, producing a highly gas-contaminated atmosphere. Normalization of dust treatment system operations will require pre-treatment of gases from one of the electric ferromanganese smelting furnaces by installing a dust elimination system — NIIOGAZ group cyclones or a DU-3000 centrifugal inertial dust eliminator, but with a diameter of 4 m — upstream of the smoke extractor as recommended in this paper

The capabilities of analytical control systems and their applicability in sinter production are considered. Industrial experiments showed that continuous control of the chemical composition of the components of sinter burden can improve the quality of sinter and save up to 8 kg of limestone and 1 kg of coke per ton of sinter produced.

Kinetics of nitrogen absorption and desorption by melts of the Fe–C system with surface and volumetric oxidation in a stream of oxygen containing 0.2% of nitrogen with an initial metal temperature of 1350–1600°С, [С] = 0.8–3.8%, oxygen flow 0.24–1.8 liter/(minŊkg), are studied. It is established that there is excess chemical potential of nitrogen in a boundary layer compared with the nitrogen content in a gas stream.

A lack of domestic technology for preparing aluminum-erbium master alloy intended for improving the physicomechanical properties of aluminum alloys gives rise to the importance of creating technology for aluminothermal reduction of erbium compounds from chloride-fluoride melts. Thermodynamic analysis of aluminothermal reduction of erbium fluoride and oxide taking account of intermetallic compound Al₃Er formation makes it possible to determine the thermodynamic possibility of the process. The phase composition of fluxes used for preparing master alloy of the Al–Er system from erbium fluoride and oxide is studied. Experimental data are provided for aluminothermal preparation of Al–Er master alloy from erbium fluoride and oxide. The effect of mixing melt and preliminary remelting a mixture of salts and zernolite, and the structure and phase composition of the master alloy specimens obtained are studied.

Features of gold cementation from cyanide solutions with electrolytic zinc powder are studied. The test powders are prepared by electro-extraction of alkaline solutions after leaching zinc-containing dust. Cementation is conducted in two regimes: under pressure (Merrill–Crowe process) and a fluidized bed regime. It is established that with respect to degree of gold extraction and specific consumption of test dendritic powder it is no worse or surpasses powders prepared by vapor condensation used traditionally in the gold extraction industry. The features established may be explained by physical features of powders prepared by electro-extraction from alkaline solutions.

The morphology and elemental composition of Al–12% Si powder grade AKD12 of three fractions are studied. Powder is prepared in an original molten metal gas spraying unit UR-9 in a high-purity nitrogen atmosphere. Results are provided for measurement of mechanical properties, a study of outer surface morphology and the failure surface of objects prepared by selective laser melting from AKD12 powder fraction less than 45 μm. It is shown that the mechanical properties of these objects surpass these indices for analogs produced overseas, i.e., ultimate strength σ_u = 245 MPa with relative elongation δ = 12%.

Results are provided for a study of the elemental and phase composition of PAO Northern Pipe Plant electric steel smelting furnace gas cleaning dust. Dust particle shape and size are evaluated. X-ray microanalysis is used to determine the elemental composition of dust particles art local sampling points. It is shown that zinc in dust is found predominantly in calcium and magnesium ferrites, and also in spinels.

Thermodynamic modeling is performed for phase formation of nitrogen-containing steel 04Kh20N6G11M2AFB during crystallization, solidification, and cooling that shows crystallization proceeds through δ-ferrite. In this case depending on alloying element content within the limits of the grade composition δ-ferrite may exist both at temperatures corresponding to the cuidus — solidus interval, and also be retained below the solidus temperature. Ingot metal is examined comprehensively in different ingot zones in order to study structure formation throughout the ingot volume, alloying element liquation, and nonmetallic inclusion and secondary phase composition and distribution.

A new efficient method of casting tubular billets by directional solidification without the use of a core is proposed making it possible to obtain a fine-grained dense structure of cast iron due to intensive onesided heat removal and excess supply to the solidification front of superheated liquid phase during the entire billet formation time in a metal water-cooled mold (crystallizer). It is shown that the method makes it possible to obtain a prescribed final cast iron structure by creating a certain cooling regime for castings outside the mold. In the positive effect of directional solidification of the melt inherited by iron a decisive role is played by the formation of a dense structure and a more dispersed carbide eutectic with a favorable carbide morphology, which determines the good cast iron wear resistance. The results of studies confirm that the new casting method provides production of workpieces with a prescribed phase composition and improved physical, mechanical, and operating properties. The effect is considered of various factors of the formation of workpieces from different types of cast iron: gray alloyed with lamellar graphite, high-strength and high-chromium, and also Niresist cast iron, on the structure, properties and service life of components for critical purposes of general, mining and oil refining engineering.

Based on test results for low-alloy steel of strength categories X42–X70 the effect is established of loading and strength properties on sulfide stress corrosion (SSC) cracking resistance with uniaxial tension. A favorable effect is demonstrated for a reduction in loading factor and an increase in strength on an increase in steel SSC resistance. The level of steel yield and ultimate strengths providing good SSC resistance is determined.

We describe the results of an experimental study of longitudinal and transverse variations in wall thickness at the ends of pipes after rolling in a stretch-reducing mill (SRM). We found that the largest “contribution” to the scatter in wall thickness comes from internal hexagon produced in the pipes by the reduction-mill drawing schedule and the roll pass design. A mathematical model was developed based on current high-speed SRM mode calculation procedures, and the plastic tension coefficients, rolling diameters, and roller speeds for each SRM stand in steady-state rolling mode were calculated. The pipe wall thicknesses calculated using the mathematical model were similar to those obtained experimentally. The accuracy of the pipe inside diameter was determined.

Physical and chemical testing of sulfate product, obtained as a result of high-temperature treatment of ore from the Kundybai field with sulfuric acid mixture at 500°C revealed the presence of cerium oxide corresponding to natural cerianite (CeO₂). A mechanism of its formation is proposed, which includes a stage of cerium sulfate (Ce(SO₄)₂) formation followed by its dissociation to CeO₂. The presence of this compound in the sulfate product allowed establishing the temperature required to further conduct the sulfation process and prevent cerianite formation.

It is known that the main factor specifying the dispersity of spraying of particles of metallic powders is the energy of blowing, which is, as a rule, controlled by the speed of supply of gaseous energy carrier to the jet of the melt. We study the modes of manufacturing and, on the basis of the results of computer simulation, develop special tooling for the procedure of dispersion of powders of solder aluminum alloys. We consider technical and technological schemes of getting powders from aluminum alloys intended for soldering the waveguides. The computer investigations of the influence of the geometry of structural elements of equipment on the parameters of dispersion of the AK12Ts10 melt are carried out by using the Solidworks Flow Simulation package for engineering analysis. In this case, it is assumed that the speed of the gas (argon) jet at a temperature of 20°С at the site of collision with the melt must be maximum for the identical other conditions (initial pressure, gas temperature, and temperature of the melt). We establish the dependences necessary and sufficient for the design of structural elements of the equipment and the creation of technological modes guaranteeing the realization of conditions of stability of the process of dispersion of the metal melt in getting powder of the required fraction (70 μm) in a laboratory installation. We present a description of the installation intended for the dispersion of AK12Ts10 melts with the help of which we prepared a pilot batch of a powder fraction 70 μm in size with a mass of 400 g. This batch was then delivered to the Reshetnev “Information Satellite Systems” Enterprise for industrial tests aimed at soldering aluminum waveguides. The tests of the paste in the course of soldering of elements of the waveguides under industrial conditions exhibited positive results.