Mössbauer and magnetometric studies of uncommon magnetic properties of ordered (B2 type) Fe-Al alloys

This work presents experimental data on the Mössbauer and magnetic measurements of ordered Fe_65.9Al_34.1 (B2 type) alloy depending on temperature and external magnetic field. The results obtained show that the ground magnetic state of the alloy cannot be referred to any of the known types of magnetic ordering. A model of local magnetic moments is proposed, in which the amplitude and the sign of a local magnetic moment are determined by its local chemical surroundings. The model suggests the existence of local magnetic moments that are antiparallel to the total magnetization of the alloy: the magnetic moment of a Fe atom with five and more Al atoms in the nearest surroundings is antiparallel to the total magnetization. Within the framework of the model proposed, a quantitative agreement of the calculated and experimental values of the average magnetic moment of the Fe atom in the alloy has been obtained. It is shown that in the B2 superstructure there appear magnetic inhomogeneities of a nanometer scale, which consist of magnetic moments that are parallel and antiparallel to the total magnetization. The behavior of the magnetic and Mössbauer parameters depending on the temperature and the applied magnetic field indicates the existence of collective fluctuations of magnetic moments. The quantity of Fe atoms in such fluctuating ensembles, as evaluated from the data on the magnetization, is compared with their quantity in the magnetic inhomogeneities.     

Analysis of titanium reduction in a blast furnace

By combined study of heat-transfer and reduction processes, the factors that determine the blastfurnace reduction of titanium oxides are analyzed.     

Processes for boosting coke quality

The temperature stress in coke pieces of different sizes is calculated during cooling by sprayed water. In the range 650–200°C, no cracks are formed if the cooling time is more than 13 min. The benefits of the new cooling method are outlined. Examples of industrial-drum application are presented. In coke production, drums may provide great benefits.     

Structural state and magnetic properties of cementite alloyed with manganese

Using X-ray diffraction analysis, M?ssbauer spectroscopy, and magnetic measurements, the structure, parameters of hyperfine interactions, localization of Mn atoms in the lattice, coercive force, and specific saturation magnetization have been investigated in the mechanically alloyed and annealed cementite (alloyed with manganese) of compositions (Fe_{1 ? x} Mn _x )₃C (x = 0?C0.12). It has been shown that strongly deformed cementite resides in the low-coercivity state and, after annealing in the vicinity of 500°C, in the high-coercivity state. Alloying with manganese reduces the coercive force, the specific saturation magnetization, and the Curie temperature of cementite. Inhomogeneities of the distribution of manganese atoms indicate the temperature dependence of the coercive force of mechanically alloyed and annealed cementite samples.     

Effect of Structural-Phase Composition on Magnetic Properties of Iron Powders Ground in Carbonaceous Medium Doped with Surface-Active Substance

In the process of intense grinding of iron powders in heptane with addition of oleic acid, the particles' dimensions reduce, their shapes change, and the particles are saturated with carbon, oxygen, and hydrogen atoms, which diffuse to the regions of mosaic block boundaries and form weakly ordered clusters and iron-based phases. The coercive force increases from 8.5 to 92 A/cm as a result of grinding. In the process of anneal, ordered phases Fe₃C and Fe₃O₄ are produced from disordered clusters and phases, which leads to an increase in the coercive force to 220 A/cm.     

The effect of cementite on the formation of the magnetic hysteresis properties of thermally treated carbon steels

The role of cementite in the mechanisms of formation of the coercive force of high-purity 60 and 13 model steels and 9A and 12A industrial steels after quenching and subsequent medium- and high-temperature tempering is determined from the analysis of the temperature dependences of the coercive force. It is shown that cementite as a hard-magnetic phase plays an important part in the formation of the dependence H _c (T _temp) measured at room temperature. The maximum contribution caused by the coercivity of cementite to H _c of the model steels is proportional to the volume content of cementite. In the industrial steels, an effect on the coercivity of cementite is produced by carbideforming unavoidable impurities.     

Improving the energy efficiency of blast furnaces at PAO NLMK

Analysis of measures used to reduce energy expenditures shows that methods in which a single parameter is changed are ineffective. Coordinated adjustment of several parameters is required. Theoretical analysis reveals the combinations of parameters with the greatest effect. The influence of the granulometric composition of the sinter on the blast-furnace efficiency is considered in terms of the influence of the mean piece size on the reduction rate and the gas dynamics of the upper furnace region. When the reaction FeO + CO = Fe + CO₂ reaches equilibrium, the heat consumption in smelting is reduced by increasing the smelting rate. Analysis of specific approaches to reducing the heat consumption in blast furnaces for the example of PAO Novolipetskii Metallurgicheskii Kombinat (NLMK) indicates the basic measures that decrease heat consumption: optimization of the iron ore by reducing the proportion of the >45 mm fraction; increase in output of the blast furnaces to 75–90 t/day (per m² of hearth); operation with the highest permissible pressure (in terms of the charging-unit design); increase in hot strength of the coke to 60–62%; pulverized- coal injection at 140 kg/t of hot metal; and optimization of the ore distribution over the furnace radius. Between 2013 and 2016, those measures decreased coke consumption by more than 10 kg/t of hot metal. In addition, the total consumption of carbon fuel was reduced.     

Application of Computer-Based Training Software Systems for Upgrade Training of the Process Personnel of Blast Furnace Shops

Metallurgist - The NLMK has introduced a computer-based training software system (CTS) for advanced training of the process personnel. The implementation of the system made it possible to improve...     

Tests of Briquettes for Mechanical Strength

Metallurgist - The expediency of applying the test methods for sinter and pellets to determine the mechanical strength of blast-furnace briquettes is considered. Based on numerical modeling, the...