Vol 62, No 1-2 (2018)

We describe a design concept for a data analysis system to support process automation for comprehensive management of the production process and economic performance of a metallurgical company, and for making automated technical and economic performance decisions. This topic has been widely discussed in the worldwide scientific literature, but the potential risks of automating the decision-making process have received scant attention. Certain applied problems will require development of procedures supported by a cost-benefit analysis of the automation tools.

We discuss various issues involved in processing of ferrous metallurgical waste, specifi cally blast-furnace and converter waste, using the ArcelorMittal Temirtau experience as an example. We study the methods currently used for disposition of these materials by the company and by the ferrous metallurgy industry as a whole, as well as potential reprocessing methods proposed by researchers in the CIS and other foreign countries. The analysis performed here indicates that blast-furnace slag is appropriate for use as a material in sub-bases for roads. We propose a method for improving the physical and mechanical characteristics of blast-furnace slag, including filling the pores in the slag with a cement/microsilica mixture and making the slag water-repellent with used motor oil. We describe the results of experimental studies performed on the resulting material. Given that the company produces 600,000 metric tons of blast furnace slag per year, using this approach for complete reprocessing and subsequent sale of the slag will reduce the production costs for ArcelorMittal Temirtau end products by 1.725 million US dollars per year, provide an alternative raw material for users, reduce environmental impacts, and conserve natural resources.

We present the results of investigation of the influence of boron-containing admixtures on the physical properties (viscosity and melting point) and the desulfurizing ability of ladle slags in the process of treatment of steel in ladle–furnace facilities. It is shown that the introduction of В2О3 in amounts of up to 4% in high-basic high-alumina slags significantly extends the range of their homogeneous liquid state and guarantees a high degree of desulfurization and microalloying of the metal with boron (0.001–0.004%).

Research is conducted within the scope of the Clean Steel project into reasons for variation of the metal level in a crystallizer and breakouts of the crystallizing metal skin in a thin-slab CCM, and also a study of reasons for defect formation in hot-rolled strip. Examples are provided of improved monitoring and control of the VMZ casting and rolling complex (CRC) technology. Implementation of the monitoring production technology – evaluation of metal product quality – operational adjustment of technology concept makes it possible to reduce the CCM emergency situation index to less than 0.5 ton/10⁵ tons of steel, and also to determine factors influencing the formation of transverse cracks over a rolling mark, and to remove defect formation.

Results are given for testing baked anodes for aluminum electrolyzers prepared from high-sulfur petroleum coke. In anodes of these cokes, there is an increase in vanadium content to 600 ppm that contaminates aluminum. By boriding aluminum, the possibility is established of using high-sulfur petroleum coke with a high heavy-metal content in production. It is shown that introduction of micro-additions of boron into molten electrolyte and aluminum makes it possible to reduce the vanadium content in metal from 200–220 to 100–120 ppm. The production regime in test electrolyzers remained stable for the test period. An associated effect of boriding melts is a fixed reduction in voltage loss in the cathode by about 30 mV that corresponds to a reduction in electrical energy of about 1700 US$ per year per electrolyzer (with a price of 0.02 US$/kW·h).

This work is devoted to studying formation of a rich zinc phase at the surface of continuously-cast brass billets. It is shown that the effect almost always occurs during brass continuous casting. A study of rich zinc phase formation is performed for small section ingots prepared by continuous casting vertically upwards. Microstructural analysis is conducted for sections of ingots in zones of rich zinc phase formation and its composition is determined. A mechanism is proposed for the formation of this phase including zinc sublimation and condensation in the shrinkage gap followed by spreading zinc over the ingot surface and partial dissolution within it of basic composition alloy. Methods are analyzed and proposed for minimizing this phenomenon under brass ingot continuous casting conditions.

We present the results of development of a complex mathematical model of formation of multicomponent batches of charge materials, their charging into the hopper of a bell-less top system, discharging from the hopper, and distribution over the backfill surface and show the possibilities of its technological application. The results of mathematical modeling can be used to improve the applied modes of charging and correct these modes in the case of addition of new components into the charge, they allow us to analyze the influence of the applied program of distribution of charge materials on the distribution of individual components (both in the iron ore and fuel parts of the charge), which makes it possible to select and adjust the program according to the results of predictive calculations prior to entering it into the charging control system. It is shown that the application of the mathematical model gives a possibility of making substantiated choice of rational parameters of the modes of charging of multicomponent charge and decreases the level of hazard of making inefficient decisions.

The problem of energy consumption in the ferroalloy industry has become an enormous challenge as the cost of energy permanently increases, while the reserves of good-quality raw materials are decreasing. Hence, the valorization of low-quality raw materials becomes necessary under the conditions of keeping the quality of products within the marketable range and low energy consumption. From the history of smelting of manganese alloys, it is known that the priority was always given to high-grade manganese-oxide ores because the quality of the ore has a great influence on numerous important parameters. This was mainly connected with the pyro metallurgical advantages offered by high-grade ores, including high manganese content (minimizing the materials consumption), lower power consumption caused by its oxide nature, and high fusibility. However, in the last 50 years, the ferroalloy industry faces the problem of application of the carbonate ores with an aim to compensate the depletion of the reserves of oxide manganese ores and meet the requirements of steelmaking in which manganese alloys find their primary use. In the present work, we study two manganese ores, namely, pure oxide and carbonate ores. A jones riffle was used for sample preparation. A jaw crusher and zip mill were used to decrease the size of particles, a graphite crucible was used as the container of the ore, and an induction furnace was used for smelting. Various proportions of oxides and carbonates manganese ore were mixed and smelted at 1550°C in the argon atmosphere for 1 h. The investigations of the ores and products were carried out by using the x-ray diffraction (XRD) method, an ICP-OES spectrometer, and a scanning electron microscope with energy dispersive spectrometer. It was shown that a marketable high-carbon ferromanganese can be produced with at least 75% Mn and a slag containing less than 20% MnO. The results obtained for oxide-carbonate blends with 90–10%, 80–20%, 70–30%, 60–40%, and 50–50% ratios met market requirements. However, the results accumulated for oxide-carbonate blends with 20–80% and 0–100% ratios showed that the alloys obtained as a result of smelting contained only 48% Mn and 68% Mn, respectively, despite the fact that the slag contained ≤20% MnО.

A trend in the development of modern electroslag remelting is the use of the ESR technology with replaceable consumable electrodes during melting and protection of smelting space by an inert gas in a cyclic electroslag remelting (CESR) regime. Industrial development of this technology at domestic enterprises is at an initial stage, and many questions related to features of remelting of high-alloy steels and alloys have not been studied practically. Information presented in this article reflects results of studying the CESR process in a model furnace EShP-0.5U of RPA TsNIITMASh and industrial smelting in the EShP-9.8 furnace of Ruspolimet.

The effect of structural characteristics (ferrite, ferrite + pearlite, sorbite) including morphology, size and distribution of nonmetallic inclusions of different morphology, sizes and distribution, on ductile–brittle transition in structural steels is considered. It is shown that an elementary ductile microcrack is initiated by particles of critical size. For steels with ferrite-pearlite and sorbite microstructure, the particle size (carbide, nitride and nonmetallic inclusions) is almost the same. The ductile–brittle transition is caused by competition of the size of the brittle and ductile (pits) microcracks. As a result, the critical brittleness temperature T_c in simplified form looks like \( {T}_c={T}_c^0+B{\Lambda}_d^{1/2}/{\Lambda}_b, \) where elementary microcracks Λ_b and Λ_d correspond to the size of a brittle crack of transcrystalline cleavage (Λ_b) and the size of ductile crack (Λ_d), Т_c⁰ reflects the contribution of different strengthening mechanisms to metal yield strength: dislocation, solid solution, grain size, precipitation hardening, and others, and B is a coefficient taking into account the stress-strain state in the fracture zone. As part of this model of failure, it becomes clear why for hardened steel the grain size does not change up to the recrystallization temperature, and yield strength and the value of T_c have a complex dependence on the tempering temperature. Since the steel has particles of different sizes, they initiate the occurrence of pits of different sizes. The larger the particle, the sooner a micropore originates around it and pit growth is faster. A wide range of pit sizes arises that causes a wide range of T_c values. A close connection is demonstrated for the width of the ΔT_c ductile–brittle transition temperature range with a change in the distance between particles, including between pearlite colonies. This relationship can be positive and negative, which is confirmed by experiment.

It is shown that addition of rare earth metals to cast corrosion-resistant high-temperature alloys facilitates a reduction in harmful impurities (oxygen, nitrogen, sulphur) and substantially increases operating characteristics. The microstructure in cast condition and after complete heat treatment is typical of hightemperature nickel alloys. It is established that exceeding the optimum REM content leads to eutectic γ′-phase melting that may cause a reduction in operating properties. The introduction of waste, including substandard materials, during melting does not lead to a reduction in operating properties.

Exhaustion of rich or readily enriched precious metal ores leads to involvement in operation of stubborn ores from which effective extraction of precious metals by traditional methods is impossible. Within stubborn ores, a considerable part of gold is finely associated with sulphide minerals, generally with arsenopyrite and pyrite, and remains inaccessible for leaching even with fi ne comminution. Presence of an active carbonaceous agent occluding cyanide complexes of gold from solutions is another reason for stubbornness of gold-bearing ores. The joint negative effect of both factors on enrichment gives rise to doubly stubborn ores. A reduction in gold extraction indicators during hydrometallurgical processing for ores and concentrates with sorption and active organic carbon is overcome in most cases by using ion-exchange resins and activated carbon, whereas recovery of gold bonded in sulfides requires breakdown of the mineral crystal lattice. For this purpose, oxidizing roasting, and autoclave or bacterial oxidation of sulfides in a pulp are usually applied. The last two methods are now the most widespread. At the same time, roasting gold ores and concentrates is applied at a number of the overseas enterprises. This shows that hightemperature processes remain the main methods for preparing gold-bearing ores and concentrates for leaching. On the basis of results of calculations, research, and design and engineering development, and industrial tests the authors conclude that it is possible to increase extraction of gold and silver in products from the Mai and Badran fields after pyrolysis in a rotary drum furnace. Compared with oxidizing roasting environmental protection issues are resolved. Procedures and production equipment schemes are developed.

The thermoplastic characteristics of high-manganese steels with different phosphorus and sulfur contents were investigated. The zero-ductility temperature and plasticity-temperature range of the high-manganese steels were reduced significantly with increase in phosphorus or sulfur content. The relationship between the initial forging temperature of the high-manganese steel and the content of phosphorus and sulfur can be expressed as T_ift = 1200 – 1530w_S – 1650w_P. The final forging temperature is 900°C, and the heating rate during the forging of the high-manganese steel crossing must be slow. The lifetime of the forged high-manganese steel crossing was almost doubled compared with conventional cast high-manganese steel crossing.