卷 61, 编号 1-2 (2017)

Results are presented from a study of the contamination of a 24.2-ton ingot of the steel 38KhN3MFA by nonmetallic inclusions over its height and cross-section. It is shown that the pattern of contamination is different in each of these directions. Nonmetallic inclusions are compound oxide inclusions of manganese, silicon, vanadium, chromium, and aluminum, as well as sulfide and oxysulfide inclusions. The ingot was contaminated more by sulfides and oxysulfides than by oxides. It was established that the formation and morphology of the sulfide inclusions are complex phenomena which depend on aspects of the steel’s crystallization, the chemical composition of the melt, and its oxygen content. To obtain high-quality steel by vacuum degassing, it is necessary to ensure that the sulfur content is reduced to the lowest possible values. An inversely proportional relationship was found to exist between the impact toughness of the steel and the content of sulfides across the ingot. This finding is attributable to the accumulation of low-melting impurities ahead of the crystallization front and their displacement toward the central region of the ingot during solidification, which decreases impact toughness in this region.

Plasma-arc heating of periclase-carbonaceous refractory was experimentally tested. A high heating rate of 600°C/h was achieved. The experimental results were used to correct the thermal characteristics of raw refractory and to determine the energy characteristics of the arc discharge. Raw periclase-carbonaceous refractory has high heat conductivity (25 W/(m·K)) and low emissivity (0.3). The radiated power (130 kW) of the discharge is calculated from spectral measurements of an argon plasma arc with a current of 1000 A and an arc voltage of 150 V. The obtained data are used to specify the parameters of the CFD-model of plasma-arc heating of periclase-carbonaceous refractory.

It is detected that in some specimens of Damascus steel part of the excess cementite is of unusual origin, in contrast to excess phases of secondary cementite, ledeburite cementite, and primary cementite in ironcarbon alloys. It is revealed that a morphological feature of separate particles of cementite in Damascus steel includes anomalously large excess carbides in the form of irregular octahedral and prisms. It is shown that angular carbides form within the original metastable ledeburite colonies, and therefore they are called “eutectic.” It is established that unalloyed materials of the carbide class acquire Damascus properties steel properties during isothermal exposure on annealing, which leads to thermal separation of colonies of metastable ledeburite, to limitation of newly formed eutectic carbides, and to their subsequent coalescence. It is revealed that some sorts of Damascus steel, being within the field of white cast iron with respect to carbon content, do not contain broken ledeburite within their structure. It is shown that the pattern of carbide inhomogeneity entirely consists of eutectic of angular carbides of non-etching triangular-prismatic morphology.

This article examines one of the main methods for speeding up the production of cold-rolled tubes, which entails performing the rolling operation without intermediate annealing. A previously developed software package is used to analyze the main factors in the technology in order to find an efficient schedule for such rolling. Results are presented from a study of mechanical and plastic properties of tubes rolled by two variants, and it is shown that the rolling operation is unstable due to broad scatter of the plastic properties of the hot-rolled billets. It is best to roll tubes without intermediate annealing after their mechanical properties have been checked. Technological recommendations are given on the conditions for rolling stainless steel tubes without intermediate annealing.

It is shown that explosive welding may be used to create bimetal material exhibiting simultaneously high strength and good damping capacity. Bimetal strength is provided due to a layer of high-strength high-quality steel 30KhGSA, and damping capacity is provided as a result of using a layer of damping steel 60G40D. A heat treatment regime is revealed with which bimetal damping capacity surpasses that of alloy 60G40D as a result of forming a tetragonal distorted lattice and twinned structure of manganese-copper alloy.

It is shown that during continuous casting of high-strength aluminum alloy ingots of industrial dimensions there is a possibility of increasing the zirconium content to 0.4% if the production methods provide suppression of stable Al₃Zr. Melt temperature and time treatment makes it possible to prepare ingots of alloy 1973 without primary particles intermetallic with diameter of 97 mm containing 0.38% Zr and 178 mm in diameter containing 0.2% Zr. It is determined that the use of extra-furnace modification with addition of Al–5% Zr master alloy bar into the furnace tap-hole box and cavitation action of solidification in the molten pool of an ingot makes it possible to prepare ingots of alloy 01959 300 mm in diameter of guaranteed composition with alloying by zirconium for the lower limit of the technical specifications. It is shown that in spite of the presence within ingots of primary intermetallics the mechanical property level achieved complies with technical specifications for granule shape. Some increase (by 5–7% with respect to strength) of the properties of sections of granules is connected with an increase in fineness of all phases compared with a cast version.

Features are revealed for the inheritance of bimetallic rolled product of dendrite inhomogeneity of the cast structure of two-phase austenite-ferrite steel applied in the form of a cladding layer on a base of low-alloy steel. It is shown that the banded and fiber structure of a cladding layer on rolled product is the result of retention of chemical liquation and rebuilding of the surfacing dendritic structure. Results are given for quantitative analysis of specimen fractures tested in static tension in the form of two parameters, i.e., work for plastic deformation localization and specific area of a fracture surface characterizing the energy content of failure. Areas of the surface of all fractures having a complex configuration are determined with considerable accuracy due to the original procedure of digital measurement of a three-dimensional failure surface from results of photogrammetric exposure on a meso-macro-scale followed by recreation of a complete three-dimensional model of the relief. Quantitative properties of fractures are supplemented by the strength and ductility indices of bimetallic rolled product, which makes it possible to substantiate the optimum version of final heat treatment and material use taking account of carbon content in the main layer.

The expansion of aluminum pipes with variable wall thickness under internal pressure is simulated using ESI Virtual-Performance 2016.0 software based on the finite-element method. The convergence and accuracy of the solution is estimated by comparing with known solutions. It is established that internal pressure causes pipes with variable wall thickness to burst where the wall is the thinnest. The thinnest section of the pipe becomes even thinner, whereas the maximum wall thickness does not almost change. This increases the variation in the wall thickness, promoting the rupture of the thin wall. It is recommended to use pipes with minimum wall thickness variation to convey high-pressure fluid.

Iron ore reserves of the Bakal ore field are estimated. Chemical and phase compositions are provided for the main deposits. The efficiency of Bakal deposit utilization in blast furnace and steel smelting processes with different preparation methods is evaluated. It is shown that siderite may only be used as a combined raw material containing iron and magnesium.

Features are considered for steel smelting in an electric furnace based on analyzing the correlation of metallized pellet decarburization and melting. A method is developed and proposed for controlling the metallized pellet charging regime into and electric furnace bath through hollow electrodes with observation of synchronous performance of melting and loose material (pellets, lime, etc.) charging rate into the hightemperature zone beneath electric arcs. It is established that with supply of pellets into the space below electrodes taking account of intensification of metal decarburization and heating by means of an oxygenfuel burner technical, economic, and production energy indices are improved.

Results are given for a study of the structure and mechanical properties of manganese powder steels prepared by hot forging of porous workpieces in the presence of a liquid phase. The presence of a liquid phase during hot recompaction reduces energy expended in deformation and also the probability of manganese oxidation and sublimation that facilitates an improvement in steel strength and ductility properties.

Using x-ray phase, chemical, and thermal (20–1200°C) analysis methods, phase composition and thermal properties are evaluated for three specimens of quartz-containing materials used as fluxes in copper smelting production. It is established that quartz in specimens on heating to 1000–1200°C undergoes enantiothropic polymorphic transformation by a scheme: α-quartz → β-quartz → β-cristobalite. In order to evaluate the efficiency of using materials as fluxes for copper smelting production, equations are proposed for calculating fluxing capacity depending on their chemical and phase composition. A dependence is given for the amount of slag formed as a result of slagging flux impurity oxides on material phase and chemical compositions on whose basis losses of nonferrous and precious metals are evaluated. It is suggested that flux materials are heated to a temperature for the start of polymorphic transformations accompanying quartz recrystallization (~560°C) before charging into a metallurgical unit.

The available die assembly designs for hydrodynamic drawing cannot be used to produce difficult-to-form nichrome strips, which are employed as heating elements in commercial resistance furnaces. Due to intensive cold work hardening, the σ_u of nichrome reaches 1300 MPa. Nichrome also demonstrates high adhesion to the drawing channel of carbide dies (despite the use of top coating lubricant and effective lubrication), which also contributes to the heating of the die. This hampers achieving even semifluid friction conditions, required surface condition, and satisfactory tool durability. To prevent the failure of the hard-alloy inserts and to provide the fluid friction conditions, use is made of die assemblies consisting of a steel holder and hard-alloy inserts. The difference between the thermal expansion coefficients of hard alloy and steel ensures the appropriate tensile stresses, tight contact between the die components, and confinement of the lubricant