Metallurgist最新文献

Coatings obtained by electro-spark deposition method using anode alloys based on NiAl and Ni₃Al were shown to increase heat resistance of steel grades St30 (AISI 1030) (up to 10 times) and 20Kh13 (AISI 420) (up to 4 times) under the thermal cycling conditions. The structure of anode alloys and coatings after thermal cycling at a maximal temperature of 900 °C was studied. By analyzing the surface structure of the coated samples, it was established that oxides with high Fe content (> 36 at. %) were mainly formed along the edges of the samples, while the sample faces exhibited microcrack formation. Some of the microcrack surfaces were found to contain oxide coatings with higher Fe content (> 56 at. %). By analyzing the cross-sectional structure of the coated samples, it was shown that coatings are made up of the following two layers: the bottom layer, which is located at the cathode interface and exhibits high Fe content (~ 80 at. %), and the top layer. The composition of the top layer is close to that of the anode alloy, and after thermal cycling, it develops transverse microcracks. It was found that the bottom layer of the coating acts as a barrier, which prevents the microcrack propagation to the cathode surface. In those places where the bottom layer is discontinuous, microcracks from the top layer reach the surface of the cathode, which causes the formation of oxides with high Fe content on their surfaces.

The effect of local high-speed intense dynamic action by a metal object (indenter) on the change in the structure of weld metal of high strength alloy steel welded with austenitic flux-cored wire with nitrogen is studied. It is established that after welding the weld metal structure consists of austenite and delta-ferrite (3 vol. %) with microhardness HV_0.1 200–250. After intense dynamic action weld metal is strengthened by a γ → ε → α’ mechanism due to work hardening and formation of deformation within the structure of α’-martensite in an amount of 10 vol.% and a small amount of ε‑martensite while maintaining the original amount of δ‑ferrite, and with an increase in microhardness by more than 1.7 times from the initial level.

When steel is smelted in electric arc furnaces, and during its subsequent treatment in ladle-furnace units, a significant amount of power is required. This power is supplied through the use of graphitized electrodes, which are pivotal for achieving the required temperatures. However, these electrodes are costly, significantly affecting the overall production costs. Therefore, efforts to reduce the cost of steel by minimizing the consumption of graphitized electrodes are crucial for metallurgists.

The primary factor influencing the consumption rate of these electrodes is their surface oxidation by oxygen present in the furnace atmosphere. Recent studies have shown that a magnesium hydroxide-based coating can significantly mitigate this issue. When applied to the surface of graphitized electrodes, this coating was shown to reduce their weight loss by 30–40% at the test temperature in an oxidizing atmosphere. Notably, as the temperature increases, so does the benefit of this weight loss reduction.

The efficacy of the tested can be attributed to its unique properties. Upon application to a graphitized electrode’s surface, the coating material penetrates deeply into the pores, effectively sealing them and forming a protecting layer over the surface. As the temperature rises, water within the coating evaporates, leaving behind a highly adhesive residue. At 350 °C, the Mg(OH)₂ in the coating decomposes to form MgO, which has a melting point of 2850 °C. This results in a high-density coating that acts as a barrier against atmospheric oxygen, thereby significantly slowing down the rate of graphite oxidation in the electrodes.

In 2019, the authors analyzed supply chains and noted the complete dependence of Russian manufacturers of bottom-hole assemblies of drilling strings on the supply* of nonmagnetic types of steel from other countries. Industry’s technical requirements for nonmagnetic types of steel were developed and approved, considering the operating conditions of drilling equipment. An audit of foundries in the Russian Federation was conducted. In 2020, by order of Proizvodstvennaya Kommercheskaya Firma (PKF) Gazneftemash, a pilot batch of rods made of austenitic nonmagnetic steel was produced at Ruspolimet facilities. Laboratory tests confirmed compliance to industry technical requirements, namely a yield strength of 1093 MPa, tensile strength of 1155 MPa, and impact work of 242 J. The authors analyzed the leading global practices in conducting field tests of products made of nonmagnetic types of steel, based on which a field industrial testing methodology was developed and approved. This article presents the results of the trial operation of products and proves the serial use of equipment made from nonmagnetic rods with a diameter of up to 95 mm. A defect analysis performed during trial field operations is presented, and opportunities for adapting the technological process for manufacturing rods of a diameter greater than 95 mm are identified.

The article addresses one of the most significant topics in the field of weapons science, i.e., the historical Damascus blades of the Indo-Persian region. By combining previously known typological and characteristic features of oriental Damascus blades with variations in the charge and fluxes of crucible melting, observed in the historical period from the 16th to the 19th centuries, a pattern regarding the presence or absence of specific process impurities in patterned steels was established. These steels were found exclusively in the Indo-Persian region. In terms of chemical composition, not all crucible steels with a pattern on the surface of the blade can be considered Damascus when compared with the finest examples of Oriental weapons. The chemical characteristics of Damascus blades in terms of the quantitative content of process impurities are described in detail and confirmed with specific examples. New data is published on the chemical composition of 20 pieces of Damascus steel weapons dated to the 17th–19th centuries, including a shamshir with the marks of Asad (Asadullah) Isfahan. The study presents various types of damascene patterns from private collections of K. Khaydakov and D. Sukhanov, with the appropriate chemical composition. It was concluded that, based on the chemical composition, macro-, and microstructure, Damascus crucible steels of the Indo-Persian region should be classified as a distinct group of historical blade steels manufactured prior to the decline of local technologies and the influence of European metallurgical production in the Indo-Persian region.

The dependencies establishing the relationship between the tensile stresses, maximum stresses, and parameters of asymmetric out-of-flatness of strips during elastic tension for the biquadratic law of stress distribution over the width have been obtained. A comparative analysis of the obtained dependences with those known for the quadratic law of stress distribution is performed. The obtained dependencies allow the stresses and parameters of out-of-flatness to be calculated more accurately in case of partial concealment of a defect in the stretched strip and, accordingly, its treatment modes to be adjusted (for example, during drawing, hot-dip galvanizing, and continuous annealing). A more accurate calculation of the maximum stresses along the width, taking into account the asymmetry of the defect, makes it possible to reduce the probability of strip breakage and stabilize the technology of their production. The obtained dependencies can be applied in automatic flatness control systems for the production of cold-rolled strips.

This study presents the outcomes of applying an integrated approach for assessing surface layer parameters of backup roll bodies in the continuous broad-strip hot rolling mill 2000 at Severstal. This approach includes several key aspects: the operational intensity of backup rolls, the increase in body hardness, wear across different stands in the continuous mill, and the determination of the material removed after the rolling campaign. To estimate the operational intensity of backup rolls within the mill stand during the campaign, the methodology suggests using the number of contacts with the working roll or the total length of strips rolled in each stand, alongside the linear load exerted on the rolls during inter-roll contact. Experimental findings have revealed that backup roll bodies exhibit varying degrees of wear and hardness increases across the continuous mill stands throughout the rolling process. The strip length and linear load in the stands have been determined to be crucial factors influencing the wear and hardness increase of backup roll bodies during a campaign. The research successfully derived a formula to illustrate how the length of rolled strips and the inter-roll load affect the increment of the roll bodies. Furthermore, an algorithm for predicting wear in three zones along the mill stands with a prediction accuracy of at least 85% was developed. The study proposes a method for calculating the necessary removal during backup roll grinding based on up-to-date data from the mill for the duration of the rolling campaign, which correlates with the roll’s operational intensity in the stand. The proposed solution aims to optimize roll consumption significantly.

Implementing this integrated approach to assess the condition of backup roll bodies, particularly within the context of the 2000 hot rolling mill at Severstal, satisfies the evolving requirements for roll operation. Additionally, it aligns with the new requirements for compiling a rolling schedule, ultimately enhancing mill productivity.

Tribooxidation is the main mechanism to adapt the cutting tool to extreme mechanical and thermal loads during high-speed cutting. Wear and tribooxidation processes in the single layer TiAlCrSiYN and multilayer TiAlCrSiYN/TiAlCrN non-stoichiometric coatings on cutting tools after dry cutting with speed of 500 m/min on the running-in and steady wear stages were studied by the set of modern surface analysis methods. The reasonable preference of the multilayer coating comparing to the single layer one was demonstrated. It was established that oxide films with an amorphous-nanocrystalline structure are formed on the surface of the wear hole. Their composition is close to k Cr₂O₃, TiO₂, Al₂O₃ (sapphire) and Al₂O₃ · 2(SiO₂) (Mullite 1:2). Prospects of yttrium addition in the complex nitride were estimated by quantum chemical calculations, which has shown that such polyvalent metals as Ti⁺⁴, Cr^+5,6, Y⁺⁴, Al⁺³ in a multicomponent nitride form a very complex spatially organized electronic structure of double and triple bonds with unoccupied π*-orbitals of nitrogen atoms. Quantum-chemical calculations of the oxidation susceptibility of these coatings with Y microadditions confirmed that this element is more inert than chromium and it is predominantly involved in the formation of interatomic bonds with Al, Ti, Cr affecting the mechanical properties of nitride coatings.

The thermophysical properties of metals and alloys play an important role in high-temperature equipment: without them, it is impossible to create reliable devices and structures in aviation, space and laser engineering, and nuclear power engineering, as well as to predict the behavior of materials under extreme conditions. From the scientific standpoint, it is interesting to study the thermophysical properties of pure metals and alloys derived from them across a wide temperature range as they constitute convenient models. The study of the thermophysical properties of aluminum alloys in relation to temperature is an important scientific problem that is of great practical significance.

The present article discusses the effects of gallium addition on the corrosion-electrochemical behavior, heat capacity, and changes in thermodynamic functions of the AlBe1 aluminum alloy. The addition of gallium (up to 0.5 wt%) was shown to increase the corrosion resistance of the initial alloy in NaCl electrolyte medium. In the cooling mode, the known heat capacity of a standard M00 copper specimen was used to determine the temperature dependence of heat capacity for the AlBe1 aluminum alloy doped with gallium. With rising temperature, the heat capacity, enthalpy, and entropy of alloys were shown to increase while the Gibbs energy decreased. With a higher amount of gallium, the heat capacity, enthalpy, and entropy of the AlBe1 aluminum alloy were found to increase, with the Gibbs energy decreasing.

At the Chelyabinsk Zinc Plant of the Ural Mining and Metallurgical Company, oxidized zinc and lead-containing raw materials are processed in Waelz kilns. Waelz oxides, containing chlorine and fluorine, are calcined in tubular rotary kilns. The results of studies on the halide removal are provided

– in the calcination process, chlorine is removed mainly in the form of zinc and lead chlorides, while in calcined oxide, chlorine remains in multicomponent difficult-to-digest substances;

– at an increase in the specific volume of exhaust gases from 300 to 820 m³/kg of chlorine, charged into the kiln, the residual chlorine content in the calcined Waelz oxide decreases from 5.2 to 0.05%;

– at the pilot kiln (length of 1.9 m, diameter of 0.2 m), tests were carried out to determine the specific volumes of exhaust gases and the gas flow velocity.

The following results were established

– within 1 h from the beginning of the experiment, the reaction proceeds in the diffusion-kinetic mode;

– when the velocity of gases at the outlet of the kiln decreases to 3 m/s, the sublimation occurs in the forced diffusion mode. This correlates with the data on the velocity of gases in a real industrial kiln;

– the capacity of the industrial kiln (L = 41 m, D = 2.5 m) is 8.0 t/h of waelz oxide using the calcined product (chlorine content of 0.05%) with a volume of kiln exhaust gases of 12–18 thous. Nm³/h at a temperature of 500–550 °C and the size of the charged waelz oxide pellets of 6–10 mm. When the pellet size is reduced to 2–4 mm, the kiln capacity increases from 8 to 10 t/h, while the chlorine content decreases from 0.05 to 0.04%.

On the basis of pilot tests, a cyclone cooler, capable of cooling 18,000–19,000 Nm³/h of gases with a temperature of 600 °C, was developed for the kiln.