Russian Metallurgy (Metally)最新文献

Secondary oxidation processes using various slag mixtures are studied, and material and thermodynamic calculations are performed for the existing industrial and promising neutral mixtures relative to titanium and aluminum in liquid steel based on MgO and CaO with the minimum silicon oxide (SiO₂) concentration. Recommendations for reducing secondary oxidation through a slag in a tundish for corrosion-resistant steel have been developed.

The possibilities of controlling the morphology and size of the structural constituents in a VT22 titanium alloy by changing the temperature and time parameters of treatment are demonstrated. A coarse-lamellar structure with α lamellae more than 20 μm long is found to form in the alloy upon cooling from the β region at a rate of 0.002 K/s, and a fine-grained α + β structure with α particles less than 0.3 μm in size forms during thermohydrogen treatment, which includes high-temperature vacuum annealing.

Changes in the microstructure and hardness of the metal deposited with flux-cored wires 2.0 and 1.6 mm in diameter, which are characterized by different contents (from 9.8 to 29 wt %) and types of titanium carbide, are studied during their deposition with a nonconsumable electrode. The structure of the deposited metal is shown to contain both retained coarse titanium carbide and fine titanium carbide particles no more than 10 μm in size. The effect of nickel added to the composition of flux cored wire charge, both in the form of pure nickel and as part of TiC + Ni composite granules prepared by combined processing of nickel and titanium carbide powders in a planetary mill, on changes in the structure formation and the hardness of the deposited metal is studied. The use of nickel in the flux cored filler wire is shown to decrease the amount of introduced titanium carbide and to increase the hardness.

The physicomechanical properties of the welds produced by laser and argon-arc welding of EK-61 alloy manufactured by 3D printing and a traditional method are studied. The results of metallographic studies of the welded joints are presented.

A Ti–38Zr–11Nb titanium alloy and its modifications with various silver concentrations (1–3 at %) are studied. The alloy is considered as an alternative to a Ti–6Al–4V alloy, which comprises toxic elements. A production method, which includes argon arc melting, remelting, and annealing, is presented. Annealing is shown to ensure a uniform silver distribution and a slight increase in the grain size. X-ray diffraction analysis reveals the β phase of titanium. An analysis of the microhardness demonstrates an increase in the titanium β phase content as the silver content increases to 3 at %.

The problem of depositing electrospark coatings with increased contact continuity is considered. Data on the causes limiting the coating thickness and the well-known methods for increasing it are provided. A new method for deposition of thick-layer coatings has been developed, and the results of its application are analyzed.

The following problems of determining the terms of the heat balance equation at the solid–gas boundary are considered: convective heat flux, conductive heat flux, and radiative heat flux when an air plasma flow moves around a heat-resistant material sample. The problems of estimating the catalytic properties of the surface and the contribution of chemical recombination reactions of atoms to the overall heat balance are also solved. A polycrystalline SiO₂ sample with known thermophysical properties is taken as the object of study. Since measuring the gas-dynamic parameters of plasma is associated with great difficulties, only the radiative component of a heat flux can be determined experimentally by measuring the sample surface temperature using optical methods. Numerical simulation of the external flow around the sample and its nonstationary heating on a holder allowed us to estimate the convective component of the heat flux and the heat flux density increment caused by the catalytic properties of the surface Δq_w taking into account the thermal conductivity of the sample material and radiation from its surface. Calculations are performed using the kinetics of dissociation and exchange reactions in a gas mixture of O₂, N₂, O, N, NO, O⁺, NO⁺, and e^– using the Navier–Stokes equations.

A comprehensive model is developed for the assimilation of calcium from a cored wire; it takes into account heat transfer, sheath melting, the release and possible evaporation of calcium, and its subsequent reaction with nonmetallic inclusions in steel. The developed mathematical model is used to perform numerical calculations of the injection of a cored wire into steel for various operating regimes.

Industrial steel casting data are subjected to statistical processing, and a mathematical model and an algorithm for calculating an adaptive coefficient for the heat flux density of a copper mold are developed. The statistical processing of industrial data is shown to reflect the influence of the casting speed on the temperature drop of the cooling water at the inlet and outlet of the mold walls. The calculation of the adaptive heat flux coefficient with allowance for industrial data allows a computer model of heat flux density distribution over the copper wall to be adapted to the operation of a real mold. The presented results can be useful for controlling slab formation and improving the efficiency of monitoring the thermal characteristics of the mold.

The existing two-stage cast iron–steel production scheme is shown not to meet modern requirements for rational environmental management, ecology, energy and resource conservation and not to correspond to the modern level of science. The currently recognized theories of metal reduction (direct and indirect reduction, absorption-autocatalytic, diffusion-kinetic, etc.) describe processes on an atomic-molecular level. Based on the electronic theory of reduction developed by us, the reduction process is presented as the sequential operation of two electrochemical cells, namely, a carbon fuel cell, which liberates electrons from oxygen anions, and a solid-electrolyte electrolysis cell, which returns these electrons to the cations to be reduced. The advantages of a hydrogen fuel cell are noted, and an assumption is made about the possibility of developing a device combining the advantages of traditional electrolysis of oxide melts using the electricity from an electrical network and solid-electrolyte electrolysis with a fuel cell.