Vol 62, No 9-10 (2019)

Based on the results of experimental radial-shear rolling of continuously cast anodic copper billets (rods) using a 10-30 mini-mill at 750 and 850°C, a part-through fracturing from within the billets has been discovered. The volume of cavities formed as a result of such fracturing appears to be more significant at 750°C. A simulation of rolling under experimental conditions was performed using DEFORM software, and the efficiency of applying a finite-element analysis computing environment for predicting fracturing was evaluated. An adequate correlation was established between the obtained estimates of the metal ductility under different deformation temperatures, as well as the probability of formation and dimensions of discontinuities and experimental data. The comparison between the shrinkage cavity depths of the billets based on the results of computer simulation has shown that the ductility of the rod material is higher at 800°C. Based on the analysis of variation in values of the rigidity coefficient under stress condition along the radius of the billet near the end of it, as well as analysis of the path described by the points located along the billet radius in the “cumulative deformation – rigidity coefficient under stress condition” coordinates while in the deformation zone, obtained as a result of computer simulation, it has been established that fracturing at 750°C should be more significant than at 800°C. Recommendations are provided regarding further use of the results of computer simulation to estimate the size of the regions, within which fracturing is expected to occur under the given rolling conditions.

Among many factors influencing steel resistance to hydrogen induced cracking, the sulfur content in the metal and steel modification technology with calcium are of particular importance. In assessing the impact of process parameters on HIC resistance many authors do not consider their effect on production process efficiency and other quality indicators. The combined effect of calcium and rare earth metals on hot-rolled steel quality is described (with respect to steel HIC resistance, and contamination of metal by nonmetallic inclusions) in this paper. Formation of nonmetallic inclusions containing calcium and rare earth metals is described, and nonmetallic inclusions in the metal with different versions of modification are analyzed. The optimum amount of calcium and cerium required for obtaining stable results for HIC resistance in low-carbon micro-alloyed steels while retaining good rolled steel surface quality is determined.

Enhancement of product quality and reduction of production costs/energy consumption/environmental impact for steel smelted in arc furnaces both require improvements to out-of-furnace or ladle processing, and deoxidation in particular. A production process was developed for deoxidation briquettes based on the requirement that they be highly transportable and suitable for long-term storage while complying with deoxidation efficiency specifications (deoxidizer utilization, concentration of non-metallic inclusions, and duration of deoxidation process). We show that steel deoxidation briquettes meeting shape and density requirements can be produced using powder metallurgy technology. Such briquettes provide improved entrainment with the steel during the mixing process, meaning that the briquette components are able to melt more thoroughly as they are absorbed by the molten metal.

The paper presents technological and configuration solutions for new complexes of cast iron desulphurization by mono-injection of magnesium in the medium-size ladles (80–130 tons of cast iron). As a result, cast iron desulphurization (up to ≤ 0.001% of sulfur content), ladle slag correction, and cast iron purification from sulfur are achieved. Magnesium injection is provided by two-nozzle lances at the magnesium supply rate of 6.5 to 16.0 kg/min. The “free board” height of the ladles is 0.20 to 0.55 m (0.42 m, on average). The sulfur content of cast iron decreases from 0.025–0.094% to ≤ 0.001–0.002%. The actual technological parameters and main process characteristics are provided based on the results of commercial cast iron processing runs at 4 lately commissioned desulfurization complexes.

A brief analysis is provided for the energy consumption to overcome the resistance of a gas layer generated during electrolysis beneath the aluminum electrolytic cell anode, and basic concepts are provided for reducing the volume of a gas layer beneath the anode. A technical solution is proposed providing separation of the self-baking anode into individual units in a common anode housing that improves significantly not only energy, but also ecological parameters of the aluminum electrolyzer. Mathematical modeling is provided for anode gas behavior under a monoblock and a self-baking anode block. On the basis of analyzing the data obtained it is revealed that the use of a block anode reduces the electrolyzer energy required in a cell by 3–5%, improves cell productivity by 10–12%, and reduces by half the number of burners in used in the electrolysis vessel.

A model is developed for austenite flow stress dynamics during hot deformation that makes it possible to construct stress-strain curves at different temperatures, and strain rate in relation to steel chemical composition. The model is verified on the basis of independent published data and good convergence of the results obtained is demonstrated. Stress calculations are performed using the model during hot rolling for steel strengthened due to a system of titanium carbide interphase precipitates. The effect of adding titanium and molybdenum on temperature for the end of recrystallization is established.

In order to manufacture hot-reduced pipe from welded pipe billets in a continuous stretch-reducing mill (SRM) 20–102 coiled hot-rolled product is used of normal precision with respect to thickness, specified in GOST 19903. The actual value of longitudinal difference in thickness for the main mass of coiled rolled product comprises 70% of the proportion of pipe tolerance with respect to thickness, which makes it difficult to satisfy the specifications of GOST 10704 and GOST 3262 for pipe wall thickness, and also increases the metal consumption factor for a ton of finished product.

Due to development of a rapid algorithm and a calculation program for reduction production regimes, rational calibration of rolls, pipe stretching between mills and stands in a 22-stand SRM, a control system for hot-reduced pipe manufacturing technology is created and introduced. As a result of this the longitudinal difference in pipe wall thickness compared with the longitudinal difference in strip wall thickness is reduced by an order of magnitude. This makes it possible to manufacture pipe in the minus range of permissible values for deviation of wall thickness, to reduce the metal consumption factor, to increase the output of finished product, to reduce specific energy expended in pipe rolling in the SRM, and to assimilate manufacture of a thin-walled range of pipes.

We discuss the operating principle and design features for an improved mechanical flux feed system to be used in continuous slab-casting machine molds; this system provides increased reliability and operational efficiency, and is easier to maintain. We describe experimental results for the operating parameters of a combined drive for use in such a mechanical flux feed system, as well as validation of the design, kinematic and power consumption parameters for such drives.

Methods are analyzed for stabilizing self-disintegrating slags in melting low-carbon ferrochrome, and the main reasons for breakdown are considered. Four methods are shown for stabilizing oxide melts of which a promising method for preventing breakdown under contemporary production conditions for chromium ferroalloys by mixing melts is a reduction in the content of dicalcium silicate with a reduction in the CaO/SiO₂ ratio in oxide melt to a value of less than 1.4. However a reduction in CaO/SiO₂ slag basicity to < 1.7 leads to a reduction in the degree of chromium reduction. With a the aim of maintaining a high degree of chromium extraction into molten metal it is proposed to conduct melting with excess siliceous reducing agent, which undoubtedly leads to an increase in silicon in the ferrochrome obtained. A study of the molten slag characteristics showed that with an increase in silicon content in metal up to 5% there is a reduction in the residua content of Cr₂O₃ in slag to 6%. The fundamental possibility of obtaining on an industrial scale non-disintegrating slag with a residual content up to 6.0% Cr₂O₃ with basicity > 1.33 is demonstrated by experiment (during melting low-carbon ferrochrome containing not less than 5% Si). However, according to the specifications of GOST 4757–91 and the international standard ISO 5448-81 the silicon content in low-carbon ferrochrome should not exceed 1.5%, in view of which the silicothermal process for process for preparing ferrochrome by a mixing method should be separated into two stages. The first stage is preparation of siliceous semiproduct (low-carbon ferrochrome containing Si ≈ 5%) and non-disintegrating slag with reduced basicity (CaO/SiO₂ = 1.3–1.4). The second stage is refining the semiproduct with respect to silicon with preparation of highly basic slag (CaO/SiO₂ = 1.8–1.9) and ferrochrome with the required silicon content (less than 1.5%). The possibility of obtaining a non-disintegrating slag during melting low-carbon ferrochrome with subsequent processing into building rubble will make it possible to improve the ecological situation in the vicinity of ferroalloy enterprises, to reduce slag dump and adjacent territory contamination and dust content, and also to reduce the amount of slag, loss of chromium, and to increase productivity of the process with a reduction in specific consumption of lime and electrical energy.

Outline algorithms for the calculation of forces, prediction of tube failure, changes in wall thickness variation, and check of the process constraints in roller-type cold rolling of tubes are presented. Roller-type cold rolling was simulated to predict the accuracy of rolling and to improve the rolling schedules. Changes in the wall thickness variation were simulated by the finite-element method. The accuracy of the simulation was evaluated: the calculated forces are different from the observed ones by no more than 15%, which validates the algorithms developed. The rolling schedules are analyzed using a previously developed software. The proposed schedules can be used to produce tubes from corrosion-resistant steel.

Results are provided for a comprehensive study of the structure and properties formation of microalloyed pipe steel produced in an AO United Metallurgical Company (Vyksa) casting and rolling complex conducted under laboratory and industrial conditions. The features of structure formation established are used to create steel compositions for electrically welded pipes and coiled rolled product manufacturing technology corresponding to steels strength classes up to K60 with improved toughness and cold resistance.

The effect of chemical composition and microstructure parameters on corrosion resistance of carbon and low-alloy steels in neutral aqueous media, typical for oil-field pipeline operating conditions, is studied in order to develop requirements for the specified characteristics to improve steel equipment service life. It is shown that a large amount of interfacial nano-sized precipitates in steel, (even with sizes of 2–3 nm or less) mainly of vanadium carbide (carbonitride), and to a markedly lesser extent with niobium carbide, is present. A significant reduction in the corrosion resistance of steel due to the formation of such particles is observed with an increase in the vanadium content in steel more than 0.065–0.07%.

The article provides results of testing excess introduction of vanadium into a molten aluminum cell through baked anodes. This stage of special technology is preliminary and required before the boriding heavy metal impurities in molten aluminum. The requirement of a preliminary stage is dictated by the presence of an insulating aluminum carbide layer on the surface of the carbon hearth that reduces the efficiency of aluminum boriding technology. The specific properties of vanadium and its compounds make it possible to organize chemical cleaning of the cathode from an Al₄C₃ layer, replacing it with a VC substrate. It is shown that with constant introduction of vanadium into melt dynamic equilibrium is established between vanadium and its compounds entering the cell and removed from it. Stabilization of a VC-coating requires organization of boriding technology for molten electrolyte and aluminum, creating a viscous low-mobility layer of a metal-boride Me–B suspension wetted with aluminum on the hearth.

At present, push benches are not currently used in Russia because the experience of their operation in the USSR gave negative results. The history of application of push benches and the possibility of extension of the assortment of produced pipes are discussed. We present the analysis of the available data on the productivity and assortment of contemporary push benches. The advantages and disadvantages of modern pipe-rolling plants with push benches in the current economic situation are considered. The comparison of the characteristics of reeling mills reveals numerous significant advantages of push benches over the continuous reeling mills.

Pearlite transformation is a necessary step in the production of ultra-high strength wires and nanostructured bainitic steels. The initial austenite grain size has an important influence on the bainite and pearlite transformation. The effect of austenitizing temperature on the austenite-to-pearlite transformation in a medium-carbon steel was investigated by using a Gleeble 1500 simulator. The initial austenite grains coarsened from 33.7 to 68.5 μm when the austenitizing temperature increased from 850°C to 1100°C. The phase-volume percentage and interlamellar spacing of the pearlitic microstructure decreased from 86.6% to 5.2%, and from 114 nm to 110 nm, respectively, in the same austenitizing temperature range. The starting temperature of the pearlite transformation was inversely proportional to the austenitizing temperature. The pearlite-transformation temperature range (43–48°C) did not change visibly with austenitizing temperature. The Vickers hardness of the transformed microstructure (pearlite + martensite) was proportional to the austenitizing temperature.