Vol 60, No 5-6 (2016)

Computer implementation of mathematical models, algorithms, and computer programs is given for resolving a set of production problems in the field of blast furnace production introduced into Magnitogorsk Metallurgical Combine. Requirements are considered for the structure and architecture of a computer system for support of solutions adopted for an MES-level Blast Furnace Technologist workstation. A short description is provided for the main model sub-systems, and also assumptions made during mathematical modeling. Use of the systems makes it possible for engineering and production personnel to perform operational analysis of a blast furnace workshop situation, to resolve a number of production problems for controlling blast furnace heat, gas-dynamic, and slag regimes, and also to calculate the optimum blast furnace charge composition, which finally provides an improvement in blast furnace production technical and economic operating indices.

Kinetics of austenite phase transformation in previously deformed steels of different alloy systems during continuous cooling are studied. It is shown that with a basic chemical composition of 0.06% C and 1.55% Mn–Nb–Ti alloying with chromium (0.19%) leads to the formation after cooling of an almost identical microstructure, as also with addition of molybdenum (0.14%), from the point of view of fineness and hardness. An optimum steel alloy system is suggested from an economic point of view that provides the required set of properties for rolled sheet more than 30 mm thick of strength category X65 produced under conditions of the VMZ (Vyksa) sheet rolling complex (5000 mill).

The change in microstructure is considered for silicon-manganese and low-carbon steels under conditions modeling prolonged thermal action. Metal structure and property degradation is revealed. It is shown that prolonged thermal action creates conditions for the occurrence of thermal deformation ageing, the initial stage of recrystallization, and also pearlite spheroidization.

On the basis of analyzing 22 melts of high-strength steel (σ_0.2 = 428–886 MPa) of different grades 3–25 mm thick produced within countries of the European Union by thermomechanical rolling technology, the effect of chemical composition and structure on a set of mechanical properties is studied. It is shown that yield strength of high-strength steels is due to titanium, niobium, and vanadium carbonitrides. The contribution of titanium to steel strength is greater than that of niobium by a factor of three, and by a factor of 16.5 for vanadium. An increase in steel yield strength above 750 MPa leads to its inclination towards an increase in impact strength anisotropy coefficient K_a. In the concentration range 0.001–0.08 wt.% Ti, the value of K_a = 1–2 is independent of Ti content, but increases sharply to K_a = 3.8 with a Ti content in steel of 0.09 to 0.14 wt.% giving rise to a requirement for limiting Ti content to not more than 0.08 wt.%. A marked effect of Ti and Al concentration on high-strength steel impact strength is established with entirely ductile failure KCV^max. According to x-ray-spectral analysis data, coarse (with a size of 2.2–2.8 μm) inclusions have a complex structure. During formation, inclusions contain up to 15–17 wt.% Al, and then an outer layer forms upon them having up to 29–42 wt.% Ti.

Research is carried out for preparation of ferrosilicotitanium by self-propagating high-temperature synthesis (SHS) using ferroalloy powders as starting materials. On the basis of data obtained, industrial technology is developed and assimilated for producing ferrosilicotitanium for alloying pipe steels instead of a high percentage ferrotitanium. An industrial test batch is prepared and tests are carried out successfully under Magnitogorsk Metallurgical Combine conditions.

The possibility of using a rotary-disk sectional wire brush has been investigated for the nanostructuring of metal products’ surface layer and the subsequent application of functional coatings. It was established that a nanostructured surface layer with fragment dimensions up to 0.13 μm can be obtained by a percussive-frictional method that is similar to high-rate plastic deformation. The microtopography of specimen surfaces was studied under different processing modes.

Existing designs and manufacturing techniques for filters with a slot-hole structure are analyzed. It is proposed that slotted filter tubes be made by the method of deformational cutting. The method has been realized by through wall slotting of longitudinally corrugated welded metal pipe. Options are discussed for the basic structure of complexes designed to make slot-hole filtering pipes.

The combined rolling–extrusion of a porous aluminum billet is simulated mathematically using the finite-element method and QFORM V8 software. A three-dimensional problem statement with one plane of symmetry is used. The fields of displacement rates, stresses, temperatures, strains, and density are plotted. It is concluded that the distribution of these parameters is asymmetric about the processing axis. It is revealed that the density achieved in the process is close to that of the compact material.

The spent lining of aluminum electrolyzer is one of the most environmentally hazardous wastes of the aluminum industry due to its content of up to 0.2 wt.% cyanide and up to 40 wt.% fluorides. The majority of spent lining is accumulated near aluminum plants in specially equipped landfills, where it can interact with water and air, with formation of toxic compounds and alkaline solutions that could lead to ground water contamination. At the same time, spent lining is of specific value due to presence of fluoride and up to 30 wt.% carbon. Known technology for processing spent lining with preparation of cryolite in operation at some aluminum plants has lost its importance after introduction of dry gas cleaning and a change-over to electrolysis technology using acidic electrolytes. This has led to a substantial reduction of cryolite requirement. Therefore, at present more attention is devoted to technology for producing aluminium fluoride, including from spent lining. This article provides a brief review of known technology for processing aluminum electrolyzer spent lining. Technology is provided for preparing aluminium fluoride product containing fluorine of 55–59 wt.%; thus, there is a reduction in fresh AlF₃ consumption of about 4–6 kg/ton Al. Laboratory test results are provided.

Results are given for analysis of agglomerate and pellet physicochemical properties. It is shown that with transfer of blast furnace smelting into an operating regime with a high proportion unfluxed pellets in a charge requires changing the main slag regime parameters, and also the furnace charging regime. It is established that due to the difference in agglomerate and pellet physicomechanical properties, and also as a result the high corrosiveness of primary slag obtained using unfluxed pellets, it is necessary to change the regime for material charging into a furnace. With an increase in the proportion of Sokolovo-Sarbaiskii Ore Mining and Processing Combine pellets in Magnitogorsk Metallurgical Combine blast furnace charge, there is a reduction in amount of magnesium in final blast furnace slags. This is accompanied by an increase in molten slag viscosity, a reduction in its sulfur absorbing capacity, and also an increase in the temperature range for iron ore mix melting with an increase in bottom gas pressure drop and limiting melt blast force.

Features of structure and property formation are studied for cold-rolled product in two-phase ferriticmartensitic steels by modeling heat treatment in a continuous annealing unit (CAU) of six laboratory melts of different chemical composition intended for preparing steels of different strength classes according to EN10338:2013. Steel of some melts, apart from alloying with elements currently used extensively, are additionally alloyed with aluminum. Hot- and cold-rolling processing regimes simulate those used under production conditions. Results of modeling heat treatment in a CAU by different regimes show an increase in strength and a reduction in ductility properties with a reduction in overageing temperature. Rolled product of steel alloyed with aluminum has lower strength properties, ratio of yield to ultimate strengths, but better relative elongation values.

The article is devoted to a study of corrosion resistance of low-alloy steels, in relation to chemical composition, heat treatment conditions, other steel properties, and heat treatment regimes. The effect of chemical composition, degree of deoxidation, and steel cleanliness with respect to nonmetallic inclusions on steel corrosion resistance is demonstrated, including those that may be used as a main layer in corrosion-resistant bimetals.

The growth of the modern aluminum industry is characterized by a search for methods of increasing the capacity of electrolyzers, reducing emissions into the environment, and reducing energy consumption. In the production of aluminum, the specific electricity consumption can be reduced and current efficiency increased by decreasing the distance between the anode and cathode and at the same time reducing the horizontal currents in the molten aluminum. The horizontal component of the current density can be reduced by placing electrical insulation between the cathode carbon block and the bloom on the section ‘crust boundary – projection of the anode periphery on the bottom block’. Heatproof materials with the following properties are technologically most effective and economical for use as electrical insulation: good adhesion to steel, chemical resistance to cryolite-alumina melt, and quite low ultimate strength in compression. Low strength and stiffness are needed because during thermal expansion of the materials in the bottom block during the period of heating the tank to the working temperature with high resistance to compression there is a risk of the load increasing on the carbon cathode block and cracks forming in it. Moreover, such properties of the material will make it possible to decrease the risk of fracture of the cathode carbon block if the volume of the electric-insulation insert increases as a result of the electrolyte penetrating into it. The results of the investigations of the mechanical properties of some heatproof materials for use as electrical insulation of blooms in aluminum electrolyzers at high temperatures are presented in order to optimize the composition.

The effect of temperature and duration of contact melting on composition, structure, and properties of coating of the Cu–Ti system is studied. It is shown that an increase in temperature with short exposures facilitates preparation of a finer structure and an increase in coating hardness. An increase in contact melting duration leads to structural component coagulation and a reduction in coating average hardness values. Equations are obtained for determining processing parameters for explosive welding and hightemperature heating regimes for forming a coating of required thickness and phase composition.

The results of a study of the influence of the parameters of laser heat-treatment of a metal surface on the formation of the color gamut in the zone of exposure to a laser beam are presented. The prospects for using laser marking of the surface of a metal part can be greatly increased by controlling the color of the applied image. The ‘color’ version of the method of laser marking can be effectively used in the metallurgical industry to protect against counterfeiting of articles made from unique essential alloys used in, for example, the aerospace industry.