This study investigates changes in the phase-structural state and chemical composition of fragments from an experimental large-scale casting of VCh50 grade cast iron, with wall thicknesses ranging from 18 to 54 mm, produced by LZ PZM LLC. The properties of these fragments were found to deviate from the requirements of GOST 7293-85, with the degree of deviation depending on the fragment thickness. We suggest that these discrepancies are characteristic of large-scale castings with significant wall-thickness variations. Using regression analysis, the influence of various factors on the mechanical properties of the casting and the magnitude of their deviation from the standard requirements was quantitatively determined. Computer modeling revealed the influence of the wall thickness on the cooling rate, undercooling, and duration of graphite nucleation and growth within austenite, as well as graphite degradation processes during secondary graphitization. Derived regression equations revealed that pearlite content and graphite nodularity predominantly determine the achievable mechanical properties of hypoeutectic high-strength cast iron in cast blanks. Combined with published data, these equations form the basis for optimizing modifier selection for both ladle and in-mold introduction.
The main disadvantage of bioleaching technology is slow kinetics compared to other high-intensity hydrometallurgical processes. Current research focuses on accelerating the electrochemical dissolution of minerals. Several factors influencing this process have been identified, including the presence of impurities in a solid crystalline structure, the formation of galvanic pairs between different minerals in the ore, and the presence of specific ions in the solution. When these ions come into contact with the solid surface, they alter its electrochemical properties. Consequently, introducing suitable catalytic components can significantly improve the reaction rate and metal recovery into solution. This review synthesizes existing research to provide a comprehensive overview of the field and establish a foundation for future work. The review catalogs metal ions that have the potential to catalyze the bioleaching of various ores and minerals, such as chalcopyrite, arsenopyrite, and complex sulfides, and it describes the roles and mechanisms of specific ions, including Ag+, Hg2+, Bi3+, and Cu2+. Additionally, the article examines how different metal ions impact the bioleaching of low-grade ores and identifies their most effective concentrations.
This study investigates the structure and physicochemical properties of multicomponent Cr–Ni–Si–Fe alloys, which are of significant scientific and practical interest in the modern metallurgical industry. The primary research objective was to determine how chemical composition influences key alloy characteristics, such as melting temperature and density. These properties determine the technological suitability of the alloy for steel processing. Correlations between the crystallization temperature ranges and the density of the alloys with their nickel, chromium, and silicon content were established. A particular focus was placed on the role of silicon, which, at elevated concentrations, promotes the formation of intermetallic phases. The results of microstructural analysis reveal a complex phase composition in the studied alloys, comprising metallic solid solutions based on iron alongside intermetallic compounds. These findings hold significant practical importance for designing novel ferroalloy compositions with tailored properties, thereby enabling their effective application in metallurgical processes.
The article presents the results of systematization and analysis of the literature data concerning the structure and composition of heat-resistant coatings based on nickel and iron aluminides. A description of the most well-known current technological approaches to obtaining such coatings (SHS, mechanical alloying, spraying, surfacing, various deposition approaches) is given.
This study examines a method of enriching the oxygen content of the air supplied to blast furnace tuyeres. This method involves secondary oxygen injection via a specialized spraying device into the main air supply pipeline. A schematic of an oxygen distribution station equipped with hardware to control the delivery parameters to the mixing unit is presented. Physical and mathematical models were developed to calculate gas flow velocity and oxygen concentration distributions in the main pipeline after mixing. The results of the numerical modeling analysis show how variations in the secondary injection input parameters affect the required flow velocities and uniform oxygen concentration distribution across the enriched air cross-section.
Hadfield steel, a high-carbon, high-manganese alloy, is widely used where materials must withstand extreme impact, abrasion, and deformation. It uniquely combines exceptional work-hardening capacity with high ductility and strength. Components made from Hadfield steel are typically produced by casting, with their final properties being developed through subsequent heat treatment. Selecting the appropriate heat-treatment regimen represents one of the most effective methods for tailoring the required properties and ensuring long service life. This work provides a review and comparison of the most significant research from the last two decades concerning the influence of heat-treatment parameters on the structure and properties of Hadfield steel.
Fracture toughness, or the resistance of materials to crack propagation, is an important component of the structural strength of steels and alloys. The most widely used criterion in linear fracture mechanics is the critical stress intensity factor known as plane-strain fracture toughness (KIc). The significant scatter in KIc values observed in practice is typically caused by structural differences between specimens. However, obtaining accurate KIc values for evaluating ductile materials is possible given an acceptable level of constraint on plastic deformation at the fatigue crack tip. Traditionally, this is achieved by increasing specimen dimensions, which is often limited by the size of the rolled stock. In this regard, nonlinear fracture mechanics criteria have been developed, such as the energy criterion (Cherepanov-Rice integral (J-integral) or Jc) and the deformation criterion (critical crack tip opening displacement (CTOD) or δc). Variations in fracture toughness levels across different specimens (for a given structural state of the material) are generally due to the varying morphology of nominally identical structures. However, multiscale structures are often heterogeneous, even within a single specimen. In such cases, there is a high risk that fracture toughness criteria may become a misleading average. To refine approaches for determining nonlinear fracture mechanics criteria, the crack opening geometry and propagation patterns were analyzed for specimens made of heat-treatable structural steels 38KhN3MFA-Sh and 15Kh2NMFA-Sh with varying degrees of structural heterogeneity. By using a traditional fracture toughness testing scheme, the Jc and δc criteria were determined, while accounting for stable crack growth and the curvature of the crack front.
The chemical composition of a highly basic sinter was calculated using a feedstock with a high proportion of iron-bearing waste materials. Calculations confirm that the use of high-basicity sinter (1.2–4.0 units per ton) can drastically cut limestone consumption. Specifically, charging 350 kg per ton of hot metal into a furnace operating on low-basicity pellets (0.32–0.36 units) provides the required flux balance. This consequently reduces the specific coke rate and increases blast furnace productivity.
For the efficient operation of a blast furnace air tuyere, it is necessary, on the one hand, to try to increase the completeness of the reaction of natural-gas combustion inside the blow channel and, on the other hand, to protect the inner cup of the tuyere against burnout. As one of the techniques used for simultaneous solving these problems, we can mention the installation of a heat-insulating ceramic insert into the blow channel of the tuyere. In the present paper, we consider the possibility of varying the geometry of the blow channel as a result of formation of the surface topography on the insert in the form of either an annular groove or a spiral on the surface of the insert made to enhance the completeness of combustion reaction already in the blow channel. The processes of motion of liquid media, heat exchange, and natural gas combustion in the blow channel of the blast-furnace tuyere containing an installed ceramic insert with a groove of triangular section in the form of a ring or a spiral were simulated in the Ansys 21.2 medium. It is shown that the creation of a groove of this kind on the inner surface of the insert leads to an increase in the total amount of heat released as a result of combustion of natural gas, which is confirmed by the increase of the CO2 content, temperature, and blast speed at the exit of the tuyere.
Zr35Hf17.5Ti5.5Al1.5Co7.5Ni12Cu10-aluminum composites were fabricated by spark plasma sintering. The influence of sintering temperature on the structure, mechanical properties, and phase composition of the metallic glass was investigated. Phase transformations in the composite were studied using in situ synchrotron radiation diffraction. The disordered amorphous structure of the glass was preserved at a sintering temperature of 500 °C. An increase in the sintering temperature to 600 °C promoted the formation of HfAl3 and CoZr4 intermetallic compounds, resulting in an increase in hardness to 690 ± 7 HV0.2. Thermal analysis of the sintered composite revealed four distinct stages of structural and phase transformations, characterized by the sequential formation of intermetallic phases with varying compositions.
The required mechanical and physical properties of 05G2MB low-carbon, low-alloy steel sheets in strength classes K60–K65 are achieved by forming dispersed ferrite-bainite structures. These sheets are intended for producing large-diameter electric-welded pipes and are processed using thermomechanical controlled processing (TMCP). Accurately quantifying the thermal effects of austenite decomposition greatly improves the precision with which the microstructural state of steel can be predicted, which is crucial for modeling and controlling the TMCP process. This study collected experimental data on temperature versus time profiles of thermally uniform samples subjected to different cooling intensities. Cooling intensity was characterized by the derivative of the specific heat flow power with respect to metal temperature (dW/dT), ranging from 10 to 520 W/(kg·°C). The specific thermal effects of austenite decomposition were found to be 75.2–93.3 kJ/kg for ferrite formation, 107.7–126.0 kJ/kg for upper bainite formation, and 84.2–95.4 kJ/kg for lower bainite formation.
Laboratory simulations on a Gleeble 3800 thermomechanical simulator were carried out for low-carbon shipbuilding steel of grade EZ35 to develop technological solutions for thermal and Thermo-Mechanical Control Process (TMCP) that produce a fine, homogeneous ferrite–pearlite microstructure with a ferrite grain size uniform across the plate thickness by hot working alone, without subsequent heat treatment. After austenitizing at 1150 °C, none of the TMCP schedules tested produced a homogeneous fine-grained microstructure. In contrast, austenitizing at 900 °C followed by hot working in the fully austenitic temperature ranges 890–820, 880–810, and 870–800 °C and final cooling at 1 °C/sec resulted in a ferrite–pearlite microstructure with a uniform ferrite grain size; the grain size decreased as the deformation temperature range was shifted to lower temperatures. Lowering the deformation finishing temperature to 790 °C and below led to abnormal ferrite grain growth and the appearance of coarse ferrite grains with tortuous boundaries in the final microstructure at a low post-deformation cooling rate of 1 °C/sec. It was established that increasing the post-deformation cooling rate from 1 to 5 °C/sec suppresses abnormal ferrite grain growth and ensures a homogeneous fine-grained microstructure when TMCP schedules with austenitizing at 900 °C are used and deformation is completed in the two-phase (γ+α) region. The results also show that, in low-carbon low-alloy steel EZ35, the recrystallization of hot-worked ferrite during intercritical deformation is significantly retarded at temperatures below 750 °C. Based on these findings, a new two-stage TMCP schedule is proposed that produces in EZ35 steel a homogeneous fine ferrite–pearlite microstructure with required strength and high density of high-angle grain boundaries in the ferrite.
The authors have carried out a comparative analysis of the capabilities of various methods for assessing porosity of 3D-printed samples of a new six-component intermetallic beta-solidifying TiAl alloy Ti–44.5Al–2V–1Nb–2Cr–0.1Gd, at.
Flow curves describing the rheological properties of the AK7 alloy within a temperature range of 375–425 °C and a strain rate range of 0.01–50 s⁻1 were established using a Gleeble 3500 thermo-mechanical simulator. The data were used to simulate the alloy hot rolling process using a computer. For the as-cast state, the model predicted crack formation at a total reduction of 35
The paper is devoted to the development and commercial application of the method of pressure control in a continuous heating furnace that takes into account the compensating influence of metal discharge dampers. Based on the actual technological data, we deduce a differential equation (in the form of an aperiodic link of the first order), which describes the influence of metal discharge dampers on the pressure drop inside the furnace. On the basis of this equation, we develop a method for the predictive control, which enables us to compensate the influence of discharge dampers. The method was checked in a metal-heating furnace No. 2 of the Rolling Shop No.1 at the A. A. Ugarov OEMK JSC and by analyzing the results of experiments aimed at comparing different methods of compensation of pressure drops. The developed method makes it possible to reduce the pressure drop (by 5
Owing to their wear resistance and high corrosion resistance, iron-aluminum intermetallic alloys are used in aircraft engineering, shipbuilding, and mechanical engineering, mainly as protective coatings for structural components operating at elevated temperatures or in corrosive media. Interest in these alloys is largely driven by the wide availability and relatively low cost of their constituent elements. However, multistage, complex routes required to develop the target microstructure and properties, along with the costly equipment involved, hinder the wider adoption of binary iron-aluminum alloys and limit the range of products made from them. A potential alternative to conventional production routes for Fe-Al alloys is the single-stage exothermic remelting of thermite charges composed of fractions of an aluminum-containing alloy mixed with metallurgical mill scale. This approach not only enables the recycling of hard-to-utilize industrial by-products, but also makes it possible to produce fully intermetallic components. A series of preliminary experiments demonstrated that several process parameters of exothermic remelting can be controlled, thereby affecting the final alloy chemistry, microstructure, and microhardness. The novelty of this work lies in evaluating the combined effect of the thermite-charge component ratio and the process temperature conditions on the compressive strength and fracture behavior of specimens produced from experimental iron-aluminum alloys.
This article addresses challenges of lowering the production costs of mineral raw materials and mitigating the environmental impact of natural leaching from spent ores. The feasibility of comprehensively processing such materials depends on developing new methods to modify mineral properties. A typology of minerals based on their propensity for metal leaching has been developed. The technology under investigation is of particular interest for deposits with technologically accessible ores, which mining enterprises exploit in complex geological settings.
The development of the oil and gas sector, as well as solid mineral mining enterprises, is now concentrated in the northernmost and most remote regions of the country. It is well-known that the service life of specific components and parts of excavators, bulldozers, and loaders decreases significantly in the Arctic and Subarctic regions of Russia. An analysis of damaged gear wheels removed from mining equipment operating in northern latitudes revealed that accelerated gear pair failure can be attributed to various external factors and product quality deficiencies. This study investigated how the chemical composition of tooth material and the segregation of impurity atoms at grain boundaries influence the resistance to metal fracture and the development of contact damage during long-term, low-temperature operation. The results demonstrate that tests determining the threshold stress intensity factor K1rth for sustained crack growth can be used to model the initiation and propagation of delayed quench cracks. These cracks occur along the boundaries of inherited austenite grains in the surface layers of driven gear teeth in traction transmission systems.
We consider some methods of visual space modeling of the metal flow over the tool–workpiece contact surface and construct the diagram of contact stresses for the process of volume stamping of flat profiled blanks. The results obtained by different methods are characterized by good agreement. The proposed methods make it possible to predict form changes in the blanks and the formation of defects in the macrostructure of the deformed material, as well as to control the process of form changes in the forgings.
