Advanced Methods and Technologies in Metallurgy in Russia

The effect of yttrium and germanium microalloying on the structure and properties of the near-β-titanium alloy VT35 sheets in the state after the vacuum annealing, quenching, and subsequent continuous heating has been studied using optical and transmission electron microscopy, X-ray and thermal analysis, and miсrohardness. It has been found that yttrium microalloying leads to the formation of Y₂O₃ oxide particles in the alloy. It is shown that the yttrium oxide particles play a dual role in the alloy. Firstly, these particles being at the grain boundaries impede its movement during heating to a single-phase β-region, i.e., they inhibit a grain growth. Secondly, they affect the stability of the β-solid solution to the processes of decomposition during the subsequent heating by linking the oxygen in the alloy. It is found that the germanium microalloying unlike yttrium microalloying does not lead to the chemical compound formation. During heat treatment germanium being in a solid solution affects the grain structure and phase composition of the alloy less than yttrium.

The results of phase composition, microstructure, mechanical properties, and characteristics of static and dynamic fracture toughness study as well as specimens’ surface fractographic analysis for more than 20 experimental and industrial Fe-Ni-Co-Mo-Ti-, Fe-Ni-Mo-Ti-, and Fe-Cr-Ni-Mo-Ti-based high-strength maraging steels are presented. The influence of maraging steel metallurgical production technology, their heat and thermal-mechanical treatment, and level of alloying elements forming the reinforcing intermetallic particles is highlighted. Main microstructural opportunities of crack resistance and structural strength enhancement of the studied steels by adjusting the volume fraction and morphology of intermetallic, austenitic grain size, providing microstructure with metastable retained and reverted austenites, and eliminating the embrittlement effect of grain boundary carbonitride particles are defined. It is shown that the ratio of the named factor contribution considerably depends on the achieved level of high-strength maraging steel fracture toughness.

The paper is devoted to the studying of silicide particle precipitation in the near-α- and two-phase (α + β) titanium alloys. It is shown that in Ti-Al-Si-Zr alloys, three different types of particles are precipitated: (Ti, Zr)5Si3 (S1), (Ti, Zr)6Si3 (S2), and (Ti, Zr)2Si (S3). The types of precipitated particles depend on the heat treatment modes and an alloying element ratio. The investigation of silicide particle influence on the mechanical properties of the alloys has shown that silicides S1 reduced viscosity characteristics, while silicides S2 and S3 were found to reduce the heat resistance due to the depletion of solid solution by Al and Si and to impede the formation of α2-phase particles. Microstructural characterization has been performed using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The orientation relationships between silicides and matrix phase were identified by electron diffraction.

Qualitative and quantitative analysis of the distribution of structure components of Fe-Ni-Co carbon-containing invar alloy with 0.6%C has been performed. It has been shown that the cooling rate during crystallization affected volume percentage and dispersity of graphite. The alloy crystallized at a high cooling rate has demonstrated higher volume percentage and dispersity of graphite than the alloy crystallized at a low cooling rate. Both alloys have displayed similar behavior of the coefficient of thermal expansion. During the heating the constant values of thermal expansion were kept up to 200 °C. However, the minimal thermal expansion has been observed in the alloy crystallized at a high cooling rate. The explanation for that might be the following: the content of carbon into the γ-phase is lower in the alloy crystallized at a high cooling rate than in that crystallized at a low cooling rate. As thermal expansion is caused by γ-phase properties, the reduction of carbon into the γ-phase results in the minimal coefficient of thermal expansion.

Austenitic stainless steel P2000 with 0.07 C-16 Cr-13 Mn-0.71 Si-3 Mo-0.82 N (wt.%) was investigated in different structural states formed as a result of hardening treatment, which consisted of hot plastic deformation, annealing with quenching in water and aging or cold plastic deformation by rolling with or without aging. Transmission electron microscope, X-ray diffractometer, and Faraday balance magnetometer were used for study of structure and magnetic properties of the steel. After quenching from 1150 °C and aging at 500 °C which resulted in the formation of an ordered phase CrN in austenite, the steel demonstrated high strength and ductility without spontaneous magnetization (up to 0.2 A·m²/kg), in addition to high resistance to pitting corrosion. Nonmagnetic austenite structure was also obtained under cold plastic deformation and was characterized with high density of dislocations and deformation twins and, as a consequence, chemical homogeneity of the austenite. Thus, the chemical heterogeneity of γ-solid solution due to dissolution of the intermetallic χ-phase can be considered the main reason for appreciable spontaneous magnetization of the investigated steel.

An amorphous and nanocrystalline ribbon is produced applying the technology of rapid molten metal quenching. The chemical composition of the alloy is required to contain elements ensuring the amorphous structure formation in the course of quenching. A great number of various chemical elements in amorphous and nanocrystalline alloys contribute to the complex process of the structure formation in the course of heat treatment of the amorphous precursor. The results of an investigation into the melts’ property of iron-based amorphous and nanocrystalline alloys are presented in the paper. The structure has been shown to influence magnetic and mechanical properties of the material in preparing the melt before casting.

The complex multilayer protective coatings for single-crystal cooled rotor blades of the high-pressure turbine (HPT) were investigated. It was shown that in the initial state, the outer zone of the coating consisted of the beta-phase, containing 20–24% (wt.) Al. The inner coating layer consisted of a mixture of alloyed β-, γ′- and γ-phases, and at the boundary with the alloy, there was the alloyed β-phase containing 18% (wt.) Al. For alloys ZHS36VI and ZHS32-VI, the complex coating provided a gain of durability up to 25–30%.

Basic technological characteristics of a designed water-drop cooling device (irrigation density, its distribution on the cooled surface, and temperature dependence of the heat transfer coefficient) were determined. The effect of technological and design spraying jet parameters on the cooling capacity of large steel parts (hot rolling mill rolls) was obtained. Among the technological parameters under consideration was the water pressure in front of spraying jets and the number of spraying jets in a cooling device. The varied design parameters were the diameters of the spraying jet channels, the distance between the jets, the distance to the cooled surface, and the operating mode of the cooling device. The experimental data was used to obtain the correlation between listed parameters and basic technological characteristics of spraying jets in order to apply the uniform cooling of mill rolls during heat treatment.

An examination of the heat treatment division was conducted based on experimental studies on supercooled austenite transformation in high-strength silicon steel and finite element modeling by means of Heat Treatment Solution (SYSWELD) package. Austenite phase transformations during cooling with various cooling rates of the steel under consideration were studied using dilatometry and metallography techniques as well as hardness measurements. Temperature dependence of the coolant heat transfer coefficient was calculated by means of inverse heat transfer equation solution. The experimentally obtained data was utilized for numerical modeling of the heat treatment process of the steel parts under consideration in accordance with the existing industrial technology. During modeling data analysis, some deviations from the assigned heat treatment technology were revealed. Disturbances of the assigned heat treatment technology resulted in the product quality mismatch. After the elimination of the detected heat treatment process deviations, a required distribution of microstructure and hardness was obtained along the cross section of the heat-treated parts. This led to a significant quality improvement of the steel product under consideration.

The problem of a rational application of alloying elements, in particular, nickel saving, is now successfully resolved when designing carbonless austenitic Cr-Mn steels with a high nitrogen content. In order to predict the corrosion properties of steels and have optimized their chemical composition, a large group of austenitic stainless steels alloyed with nitrogen have been studied for pitting corrosion. Investigated steels were tested after hot rolling and annealing at 1050 °C followed by quenching. Pitting corrosion resistance tests were carried out on a Voltalab 10 PGZ100 device with the VoltaMaster 4 software in a 3.5% sodium chloride solution using a chlorine-silver reference electrode. It was shown that nickel-free Cr-Mn steel with a high nitrogen content (0.8 wt. %) has a significantly higher resistance to pitting corrosion (E_pit = 1.4 V) than the other steels. There were also obtained dependences of resistance to pitting, PREN (pitting resistance equivalent number) and MARС (measure of alloying for resistance for corrosion) of the nitrogen content in the steel. On the basis of the results of electrochemical studies and calculation of PREN and MARС, the correlation equations relating the pitting potential with the chemical composition of nitrogen-containing steels have been proposed.

The amount and composition of binary and ternary eutectics in the structure of high-manganese steels as well their crystallization temperature were estimated by the proposed model which was developed on the basis of the Scheuer’s and Schroeder’s equations. For experimental verification of the calculation results, about 40 bars of 40 mm diameter by different content of elements, wt.% [C] = 0.2–1.6, [P] = 0.02–0.31, and [Mn] = 12–14, were produced by melting with different rate of crystallization. It was shown that the higher the crystallization rate, the fewer eutectics were found in the structure of bars at the same content of carbon. Moreover the amount of binary eutectic is mainly determined by the carbon, while the phosphorus mainly increases the amount of ternary eutectic in the steel. By transmission electron microscopy (TEM) of replicas, the composition of ternary eutectic corresponds to γ + (Fe, Mn)₃C + (Fe, Mn)₃P with content of carbon of 1.4 wt.% and phosphorus of 7.3 wt.%. Estimated crystallization temperature of binary eutectic γ + (Fe, Mn)₃C was 1510–1530 K, and the ternary eutectic 1250 K.

A method of complex metallurgical estimation of manganese raw materials for ferroalloy production is proposed in the present article. The proposed method of complex estimation of manganese raw materials includes (1) thermodynamic calculations of manganese reduction from raw materials in FeMn and SiMn production processes, (2) calculation of specific material and energy consumption for ferroalloy production, (3) selection of rational technology for raw materials processing (production of FeMn or SiMn) on the basis of chemical composition and calculations, and (4) experimental estimation of physico-chemical characteristics of manganese raw materials such as softening temperatures and specific electric resistance of materials and charge mixtures on their basis. Availability of material specimens defines whether the method of complex metallurgical estimation can be applied in calculation or experiment-calculated form. Complex estimation of different manganese ores, concentrates, and technogeneous materials allows one to compare their metallurgical value and choose the most suitable one for ferroalloy production.

Research and development of technological aspects allowing the involvement of domestic manganese ores into ferroalloy production to cover the needs of national steelmaking are of interest to the Russian metallurgical industry. As domestic manganese ores have low manganese and high phosphorus content, they have to be subjected to processing and dephosphorization. One of the most promising manganese ore deposits among proven ones is the Usinskoe mining deposit with the biggest reserves of manganese in Russia. Manganese ores of Usinskoe mining deposit have comparatively low manganese content (18–22%) and high concentration of phosphorus (0.2–0.3% and more). On the basis of previous research and development results, a technological scheme was proposed for carbonaeous and oxide ores of Usinskoe mining deposit. Chemical composition of manganese concentrates allows us to propose technological schemes of manganese ferroalloy smelting. Chemical compositions of final ferroalloys and technological schemes, including specific consumption of materials, are given in this paper.

Generation of technogeneous waste in production of ferroalloys and possible solutions for recycling are presented in the article. A lot of by-products are generated at the stage of ferroalloy production: slags, raw materials and ferroalloy fines, sludge, dusts and some other materials. Chemical composition and quantities of slags, dusts and sludge in production of manganese, chromium and silicon alloys are given. Ferroalloy production waste can be recycled in ferroalloy production process or allied production chains. Possible applications of technogeneous raw materials in ferroalloy and allied production technologies are considered. Involvement of ferroalloy production waste into ferroalloy production technology requires deliberate decisions, as performance characteristics of furnaces in ferroalloy production depend on quality of raw materials (manganese ores, chromites, etc.). It is proposed to find a recycling solution on the basis of precise estimation of physic-chemical characteristics of materials.

Formation of iron-carbon melts is governed by carbonization of liquid metal (semiproduct) in modern steelmaking technology. Changes in structural condition of liquid melt show dynamics and results of melt formation before equilibrium state. Kinematic viscosity is considered as a structural-sensitive property of melt. New data on the relation of melt oxidization, melt formation dynamics and sulphur concentration are presented in this paper. It is shown that negative influence of impurities is sufficient at comparatively low content ([O] > 8 ÷ 10 ppm, [S] > 1 ÷ 2 ppm). Principle of complex carbonization and deep refining of melt is proposed on the basis of laboratory experiments.

It is known that one of the approaches to raise furnace productivity is to increase the gas pressure within the working capacity of the blast furnace and also the enrichment of the blast with oxygen. However, this approach cannot be realized due to the technological features of each blast furnace; in particular, the smelting processes of titano-magnetite raw materials. Thermodynamic analysis and modelling of kinetics and head transfer processes in blast furnace determine the conditions under which pressure could be increased in the furnace and enrichment of the blast with oxygen that provides the production of high purity pig irons. These conditions of high-quality iron ore materials and coke were recommended for implementation at the blast furnace. It is possible to increase the specific productivity of blast furnace by more than 10% and significantly reduce the specific consumption of coke. The mathematical model developed could be used to solve technological problems.

Blowing-in is a starting period of blast furnace operation after construction or major repair. The current approximation methods of blowing-in burden analysis are based on blowing-in practice of previously commissioned blast furnaces. This area is theoretically underexplored; there are no common scientifically based methods for selection of the burden composition and blast parameters. The purpose of this paper is the development and scientific substantiation of the methods for selection of the burden composition and blast parameters in the blast furnace during the blowing-in period. Research methods are based on physical regularities of main processes running in the blast furnace, system analysis and application of modern principles for development and construction of mathematical models, algorithms and software designed for automated control of complex production processes in metallurgy. As a consequence of the research made by the authors, the following results have been achieved:

Modern iron and steel works are, as a rule, equipped with powerful distributed control systems (DCS) and databases. Implementation of DCS systems solves the problem of storage, control, protection, entry, editing and retrieving of information as well as generation of required reporting data. The most advanced and promising approach is to use decision support information technologies based on a complex of mathematical models. A model decision support system for control of blast furnace smelting is designed and operated. The basis of the model system is a complex of mathematical models created using the principle of natural mathematical modeling. This principle provides for construction of mathematical models of two levels. The first-level model is a basic state model which makes it possible to assess the vector of system parameters using field data and blast furnace operation results. It is also used to calculate the adjustment (adaptation) coefficients of the predictive block of the system. The second-level model is a predictive model designed to assess the design parameters of the blast furnace process when there are changes in melting conditions relative to its current state. Tasks for which software is developed are described. Characteristics of the main subsystems of the blast furnace process as an object of modeling and control – thermal state of the furnace, blast, gas dynamic and slag conditions of blast furnace smelting – are presented.

Advances in modern science and technology are inherently connected with the development, implementation, and widespread use of computer systems based on mathematical modeling. Algorithms and computer systems are gaining practical significance solving a range of process tasks in metallurgy at manufacturing execution systems (MES) level (systems controlling industrial process) of modern automated information systems at the largest iron and steel enterprises in Russia. This fact leads to the necessity of developing information-modeling systems based on mathematical models that will take into account the physics of the process, the basics of heat and mass exchange, the laws of energy conservation, and also the peculiarities of the impact of technological and standard characteristics of raw materials on the manufacturing process data. Special attention in this set of operations for metallurgic production is devoted to blast furnace production, as it consumes the greatest amount of energy, up to 50% of the fuel used in ferrous metallurgy.

The paper deals with the requirements, structure, and architecture of BF Process Engineer’s Automated Workstation (AWS), a computer decision support system of MES level implemented in the industrial control system (ICS) of the Blast Furnace Plant at Magnitogorsk Iron and Steel Works. It presents a brief description of main model subsystems as well as assumptions made in the process of mathematical modeling. Application of the developed system allows the engineering and process staff to analyze online production situations in the blast furnace plant; to solve a number of process tasks related to control of heat, gas dynamics, and slag conditions of blast furnace smelting; and to calculate the optimal composition of blast furnace slag, which eventually results in increasing technical and economic performance of blast furnace production.

Steady thermal performance of a blast furnace determining its productivity and specific fuel consumption for one ton of hot metal depends on many factors. One of the main factors is the use of blast heated up to a high temperature. A continuous supply of hot blast to the blast furnace is provided by operation of the system consisting of three or four regenerative hot stoves. Energy efficiency of thermal performance of blast heating equipment significantly affects the technical and economic features of blast furnace smelting. In the total consumption of fuel equivalent, the share of thermal resources for blast heating is 10–12%. The hot blast stoves consume up to 30–35% of blast furnace gas. At present, most blast furnaces use hot blast at the temperature of 1150–1250°C; blast furnaces use hot blast stoves of different designs: stoves with an internal combustion chamber, stoves with an external combustion chamber, and top combustion or shaftless stoves (Kalugin design). The analysis of different thermal conditions in stoves has shown that Kalugin shaftless stoves are the most advanced and promising stoves in terms of energy efficiency and minimum environmental impact. The tendency for increased hot blast temperature was implemented in Kalugin stoves by means of energy efficiency improvement through the recovery of thermal energy of combustion products which are formed during checkerwork heating. The use of this energy in heat pipes for heating blast furnace gas and air supplied to the stove pre-chamber has resulted in an increase of the blast temperature and reduction of the BF gas consumption for heating. Moreover, the specific coke consumption for iron smelting was also reduced. These findings have been confirmed by heat balance analysis and by experience of commercial stove operation.

Problems of emissions of greenhouse gases into the atmosphere occur and influence the content of these gases in the atmosphere, thus driving global climate change. Carbon dioxide, which is representative of greenhouse gases and emissions into the atmosphere, is usually connected with the use and combustion of organic fuel containing carbon. In various technological processes, the specific rate of organic fuels can differ considerably, and the character of these technological processes can intensify the influence of emissions of carbon dioxide. The metallurgical enterprises are a source of considerable emissions of greenhouse gas – carbon dioxide. The iron and steel industry which consumes all over the world a significant amount of organic fuel is necessary, including, in particular, coked coal and coke, natural gas, fuel from coal dust, etc. During metallurgical processes, original technological fuel gases, such as blast furnace and coke-oven gas, are generated and used in processes which are sources of already secondary emissions of carbon dioxide. The purpose of the present work is to present a discussion of the character and models of carbon dioxide emissions with reference to such an energy-intensive process as ferrous metallurgy.

In this report, we can identify five types of technological processes which are described: the heating furnace, oxygen convertor and coke-chemical processes, the blast furnace process, and the electric arc furnace. For each type the rated formula for the definition of carbon dioxide emissions is received, and examples of calculations are shown.

A methodology based on a two-stage approach was developed for process technology selection. The first stage includes evaluation of available technologies, followed by a short listing of the best technologies based on mass and energy-balance modeling, financial analysis, and risk analysis. The second stage involves detailed analysis using refined input data, mass, and energy-balance modeling, and capital and operating cost estimation, as well as a detailed financial analysis. A case study covering selection of ironmaking technologies for a company located in the Russian Federation is presented to illustrate the critical elements of the methodology developed and the analysis carried out.

It is shown that the existing methods for determination of thermal properties of materials are based on application of some solutions of the heat conduction problem without regard to internal heat sources. Therefore, these methods allow determining only effective values of thermal characteristics of the material which are true for specific conditions of heat treatment. This paper deals with a new method which makes it possible to determine (with known calculated values of heat capacity and density of the material) the dependence of five thermal parameters, i.e., thermal diffusivity coefficient, thermal conductivity coefficient, rate of internal heat source, as well as effective values of thermal diffusivity and thermal conductivity coefficients, on the temperature of heating (cooling).