The review describes methods of stress corrosion cracking (SCС) tests that implement various conditions for samples loading: at a constant static load or deformation, at a constant or increasing load of samples with a previously grown fatigue crack, with a slow strain rate. Such tests shall be carried out to determine the resistance of shipbuilding materials to be used in loaded ship structures in contact with seawater. Brief descriptions of the mechanism of stress corrosion cracking of steels and alloys are given. The necessity to carry out bench tests of steels and their welded joints, as well as models simulating individual units and elements of structures, is indicated. At this stage, conditions are ensured as close to operating conditions as possible due to exposure in various climatic zones of the world’s oceans (variations in temperature, chloride concentration, amount of dissolved oxygen, degree of biofouling, and their simultaneous impact). It is shown that during verification field tests (final stage) new materials promising for operation in marine conditions pass the final evaluation of corrosion resistance in the form of elements of ship structures and systems in the conditions of ship operation.

A technique was developed for the numerical analysis of the thermal state of long mandrels of a three-roll rolling mill using modern computer simulation software. The initial and boundary conditions were determined taking into account the peculiarities of rolling in a three-roll screw rolling mill on a long mandrel. The authors carried out a qualitative assessment of the thermal state of a long mandrel by means of visualized representation and established its significant inhomogeneity. Influence of the rolling temperature and diameter of the long mandrel were revealed. Small diameter mandrels are heated to higher temperatures (577 °C) with a significantly lower gradient between the axial zone and the surface. An increase in the mandrel diameter to 154 mm lowers the temperature of the outer surface to 530 °C and increases temperature gradient in the near-surface layers up to 18 °C/mm. So the temperature in the near-surface layers for a mandrel of 154 mm at a distance of 10 – 15 mm from the surface decreases from 530 °C to 315 °C. Features of the temperature field in the cross section were established taking into account thermal interaction of the sleeve with the mandrel in the zone of contact with hot metal and in gaps between the rolls. Temperature of the near-surface layers in the contact zone is 30 °C higher than in the gaps. Dependences of temperature of the cross-section characteristic points on the rolling time were determined, it has been established that in the first two seconds there is an intense growth according to the parabolic, and then according to the linear laws. Temperature of the central layers with a radius of 50 mm increases with a much lower intensity, by about 100 °С during the entire period of rolling, while during the same time, the near-surface layers are heated by 300 – 400 °С.

Ferrous metallurgy enterprises continuously fill dumps with steelmaking and blast furnace sludge with high zinc content. Sludge occupying significant territories of enterprises is not involved in production and harms the environment. Since zinc leads to the formation of deposits in the blast furnace, manufacturers cannot involve this sludge in sinter processing. In addition, working with sludge can lead to problems such as decrease in iron content in the sinter, decrease in productivity of sintering machines, and increase in fluctuations in the sinter chemical composition. At the same time, zinc-containing sludge can become a valuable secondary product. Zinc remains a scarce metal, which encourages the development of technologies for processing zinc-containing materials. Extraction of zinc from sludge is difficult because it is not in oxide, but in sulfate or sulfide forms. In this paper, the possibilities of zinc extraction from sludge using the FactSage software package are evaluated. The authors present results of thermodynamic calculations of the possibility of zinc extraction from four types of sludge from two Russian ferrous metallurgical plants – EVRAZ NTMK and MECHEL. The data of chemical and phase analyses of this sludge are considered, as well as simulated graphs of zinc extraction dependencies from them. The graphs were built on basis of the received data from FactSage package. Addition of the reducing agent to the sludge varied, as well as temperature of the process. In addition, the possibility of abandoning carbon as a reducing agent was evaluated. To save the reducing agent, an optimal mixture of the company’s sludge was selected, in which coke consumption can be minimized.

The probability of the existence of microheterogeneous states in Fe – Mn – C melts has been analyzed in accordance with the concepts of chemical thermodynamics. The microheterogeneous state of a chemically heterogeneous Fe – Mn – C melt was understood as the presence of dispersed Fe – C particles in it. These are suspended in the Mn – C medium and separated from it by an interface. The microheterogeneous state in Fe – Mn – C melts is destroyed as a result of heating to a temperature specific for each composition. The hypothesis of the microheterogeneous state of Fe – Mn – C melts is supported by a wide range of numerous experimental data on their thermodynamic and physical properties. The identification of anomalies in temperature dependences of physical properties of Fe – Mn – C melts has allowed for temperature values above which the melt superheating treatment (MST) causes destruction of microheterogeneity to be determined, i.e., liquid – liquid structure transition (LLT) in the melt. LLT is understood by the authors as a structural transition “microheterogeneous melt – homogeneous solution”. This is expressed as the destruction of the microheterogeneous state when the Fe – Mn – C melt is heated to a temperature specific for each composition (MST). The authors have previously analyzed the effect of LLT in Fe – Mn – C melts on the microstructure, crystal structure and mechanical properties of solid metal in submicrovolumes. This paper describes a method of theoretical determination of the temperature range where the microheterogeneous state of the Fe – Mn – C melt is thermodynamically stable. The thermodynamic stability of dispersed Fe – C particles in the Mn – C medium has been estimated according to the equations proposed by G. Kaptay for a regular solution. It was assumed that the interface between the dispersed particle (Fe – C) and the dispersion medium (Mn – C) is enriched with carbon. The paper demonstrates the possibility of existence in the Fe – Mn – C melt of dispersed Fe – C particles with sizes from 2 to 34 nm, distributed in the Mn – C dispersion medium and separated from it by an interface with increased carbon content. The estimated result is consistent with the data on the size of structural units of a viscous flow, obtained earlier within the framework of the theory of absolute reaction rates.

A new approach to obtain amorphous oxides was investigated both theoretically and experimentally using X-ray diffraction (XRD) and electron probe microanalysis (EPMA) techniques. In this work, the conventional sol-gel method was modified by the addition of malic acid as an oxidizing agent and successfully applied to obtain two oxides Al₂O₃ & Fe₂O₃ with the amorphous structure. The results of the modified sol-gel method were compared to those obtained by thermal decomposition of corresponding salts, and the advantage of new technique was clearly demonstrated. Thermal stability of the obtained amorphous oxides was examined by the differential scanning calorimetry (DSC). It was found that amorphous Al₂O₃ is stable up to 790 – 810 °C, while amorphous Fe₂O₃ recrystallises at about 160 – 180 °C, depending on the heating rate.

New cast austenitic Cr – Ni – Mn steel with 0.5 % N (grade 05Kh21AG15N8MF) surpasses cast steel of 18 Cr – 10 Ni type used for comparison in terms of the impact strength in the entire range of climatic temperatures. This part of the paper will pay attention to particles of non-metallic inclusions (NMI) in cast nitrogen-containing steel as a factor which affects mechanical properties under static and impact loading at low temperatures. NMI in laboratory metal consist of globular oxysulfides, with SiO₂ oxides in the central part and an outer layer formed by manganese sulfide MnS, with an average particle size of ~75 % up to 4 μm. During the steel impact bend test at –160 °C, these NMI do not initiate cracking and do not contribute to crack propagation as a fracture in isolated pits. Under tensile conditions at –110 °C, the yield strength of nitrogen-containing steel increases by more than 1.7 times in comparison with the properties at +20 °C. Ductility does not decrease when cooled to –110 °C. In this case, NMI particles are strongly deformed due to the development of cracks in their oxide part. Even when NMI reach the surface of a sample in the working part in the neck zone, they do not initiate cracking. Cracks at the “NMI/deforming metal” interface are not formed. Even with a random arrangement of particles in the form of chains along the axis of application of the tensile load, at a distance of 5 – 20 μm from each other, pores do not form around the particles or merge into a crack nucleus. The results obtained correlate with the literature data that NMI can act as stress relaxers in ductile steels.

In previous publications, it was shown that the use of low-carbon steels with bainite hardenability alloyed with chromium, molybdenum and other carbonitride-forming elements is promising for the production of cold-resistant and SCC (sulfide stress corrosion cracking)-resistant electricwelded tubing (tubing). Tubing is often operated in CO₂-containing corrosive environments, therefore, determining the steel resistance to this type of corrosion is an urgent task. It is known that the addition of chromium to steel increases not only its hardenability, but also its resistance to CO₂ corrosion. Influence of other alloying elements is not obvious. For the laboratory experiment, nine variants of the chemical composition of steels for the production of welded tubing were developed. The rolled test steels were investigated. Results of the studies of corrosion resistance of these steels are shown and compared. The authors made an assessment of influence of the main alloying elements on resistance to CO₂ corrosion. The steels with different contents of Cr, Mo, V, Mn, Zr were studied for resistance CO₂ corrosion at different temperatures. It has been established that the steel chemical composition and the test conditions determine the composition of CO₂ corrosion products, affect the process of formation and growth of corrosion products, thereby affecting corrosion resistance. Decrease in the corrosion rate of chromium-alloyed steels can be associated with the protective properties of the corrosion products formed during testing. Laboratory corrosion tests for resistance to CO₂ corrosion at an elevated temperature of 65 °C and subsequent studies of the formed corrosion products revealed a positive effect of chromium and molybdenum on the rate of general corrosion by mechanism of formation of dense corrosion products that perform a protective function.

Quantitative transformations of the structure at a depth of 0, 2, 5, 10 mm along the central and symmetry axis of the fillet of long differentially quenched rails head after extremely long-term operation (passed tonnage of 1770 mln. gross tons) were identified at macro-, micro- and nanoscale levels by methods of optical, scanning and transmission electron diffraction microscopy. At a macroscale level, the numerous shallow parallel cracks of contact fatigue are detected on the surface of working fillet, and on the surface of inoperative fillet there are only small spallings. The lateral wear of the rail was 2.5 mm and the vertical wear was 2 mm. Microstructure of the rail head metal corresponds to the requirements of standards and specifications of the Russian Railways. At microscale level, the transformation of cementite plates was established by cutting it with moving dislocations and dissolving with the escape of carbon to the dislocation lines, low- and high-angle boundaries. A decrease in microstructure dispersion is noted with a distance from the tread surface. At the nanoscale level, subgrain structure formed in the surface layers (subgrain size 110 – 200 μm) contains nanosized cementite particles (25 – 60 nm) localized at the joints and along the subgrain boundaries. It is supposed that this type of structure is formed as a result of dynamic recrystallization under megaplastic deformation in the process of extremely long-term operation of rails. The content of subgrain structure in the fillet layer is five-fold higher than that in surface layer of the tread surface. It was established that during operation, the transformation of lamellar perlite along the central axis of the head proceeds more slowly than along the symmetry axis of the fillet.

The paper presents one of the solutions to reduce the installed power and increase efficiency of hydraulic pump drive of high power pressing equipment used in metallurgical plants. The authors have developed a multistage hydraulic drive based on a block gear-multiplier. Plungers of all cylinders form a movable block, the cylinders – a stationary one. The mode of operation (reduction, multiplication) is provided by a combination of output cylinders supplying fluid to the power cylinder by switching some of them to drain. Analysis of a four-stage drive with a three-stage multiplier gearbox is presented in comparison with a simple pump drive. A four-stage drive with two output cylinders provides a reduction gear and two multiplier stages, with which a stage of fluid supply to the power cylinder directly from the pumps (pump stage) is combined. Power and kinematic parameters of the drive were determined by the power loading during the working stroke and speed mode during the working cycle (forward (idle and working stroke) and reverse stroke). It is advisable to use a multi-stage drive with a smoothly increasing load over the entire length of the working stroke (upsetting, drawing operations). Analysis of the basic and additional combination of stages for linearly increasing power load, which was determined by the pressure at the beginning of Р₀ , and the maximum pressure at the end of the working stroke Р_max was carried out. In the basic version, a gear stage (idle stroke), pump stage and two multiplier stages (working stroke) are sequentially combined. With an additional combination, the reduction stage covers idle stroke and initial part of the working stroke. Analysis was carried out under the condition of equality of pressure and power of the pumps in stages and the condition of equality of direct stroke time of the compared drives. The ratio of pump capacities was estimated. Dependences of the main parameters of the developed drive, reduction and multiplication factors were obtained. With the accepted initial data, it is possible to reduce the pressure and power of the developed drive pumps (in comparison with the simple one) by 28 – 37 % with an additional combination of stages (increases with an increase of an idle stroke). It is lower for the basic combination by 5 – 9 % (reduction is greater at lower idle stroke values). The use of an additional combination is limited by the ratio P₀/P_max ≤ 0/4.