Russian Metallurgy (Metally)最新文献

A systematic study of the influence of various types of mechanical action on magnetic properties and energy losses during remagnetization in electrical steels was carried out. Using a specially designed and manufactured experimental setup, samples of various types of electrical steels were studied at magnetization reversal frequencies of up to 5 kHz and magnetic induction amplitudes of up to 1.9 T. It was found that the deterioration of magnetic properties occurs to a lesser extent during the manufacture of samples by waterjet cutting compared to laser processing. It was shown that as a result of heat treatment at 900°C in vacuum, the magnetic properties are restored to their original values. The experimental results of measuring energy losses during frequency magnetization reversal were compared with theoretical models.

The deformation behavior and microstructural evolution of a Co–28Cr–6Mo alloy during uniaxial compression tests have been analyzed. The tests are carried out at 1000, 1100, and 1200°C and strain rates of 1, 10, and 50 s^–1 using a Gleeble 3800 machine. Deformation resistance curves are obtained and the peak stresses are determined. The deformation behavior of the alloy is characterized by an increase in the flow stress with the strain rate and by its decrease with increasing temperature. The peak stress is recorded at higher strains when the temperature decreases or the strain rate increases. Deformation in the temperature range of 1000–1100°C is accompanied by strain hardening and partial dynamic recrystallization. After deformation at 1200°C, the microstructure of specimens consists of equiaxed recrystallized grains, and the microhardness does not depend on the strain rate. At the same time, an increase in the strain rate at 1000–1100°C leads to a slight decrease in the microhardness. The data obtained can be used for selecting deformation conditions for the Co–28Cr–6Mo alloy using industrial metal forming methods.

The specific features of galvanic deposition of a tin–bismuth alloy from a sulfuric acid electrolyte and the influence of ultradispersed diamonds (UDDs) on the deposition kinetics are considered. The deposition kinetics is accompanied by diffusion hindrances that are caused, to a lower extent, by the delivery of discharged tin and bismuth ions to the cathode surface and, to a higher extent, by the diffusion of these ions through a dense adsorption film of hide glue on the cathode surface. Electrons sequentially add to tin(II) ions, and the rate-determining step is the addition of the first electron. The introduction of UDDs into the electrolyte accelerates the deposition of a tin–bismuth alloy and increases the scattering power of the electrolyte, which is related to the chemisorption of tin ions on the highly developed UDD surface.

Computer simulation of longitudinal rolling is performed for different combinations of the diameters of the upper and lower rolls: 600–600, 590–600, 570–600, and 300–600 mm. The rolling for each variant of combinations of working roll diameters has been carried out in three passes (the initial strip thickness is 2 mm; the gap between the rolls is 1.4 mm in the first pass, 0.98 mm in the second pass, and 0.66 mm in the third pass. The methods have been proposed for determining the lengths of the arc of contact and of the actual deformation site, and the lengths of external zones have been estimated.

Abstract—A technological process of hot die forging of a crosspiece has been developed using QForm computer simulation. The influence of the technological parameters on the force parameters and the filling of the die cavity is investigated. The state of stress and the temperature fields in a forging, the optimum shape and sizes of the initial workpiece ensuring the minimum technological forces, forging passes, the optimum conditions for filling the die cavity, and forging cooling conditions are determined. The optimum forging scheme has been determined.

Data on the estimation and selection of working gases for powder plasma build-up welding are reported. Being selected appropriately, these gases protect molten metal against oxidation and stabilize arcing. The industrial use of plasma methods with a properly selected gas medium makes it possible to cover machine parts and equipment components by wear-resistant coatings. Mobile equipment for plasma build-up welding based on a KamAZ motor truck has been designed, as applied to which the thermophysical behavior of hot hydrocarbons has been considered. Recommendations for its use and operation control are given.

An electron-microscopic study of the structural-phase composition of materials for late graphitizing modification of cast iron melt is carried out in the mold pouring bowl (FeSi75 lump (AO Chelyabinsk Electrometallurgical Integrated Plant (ChEMK))) and inside the mold (cast insert in the sump under the riser). The shape and location of the main phases with their individual morphological features, namely, size, casting defects, etc., are analyzed. A conclusion was made about a positive effect of ferrosilicon repeated remelting in the manufacture of the cast insert.

The results of a set of experimental studies of the properties of epoxy–sand composites used to repair parts of road-building machines are presented. The effect of the pretreatment of the particulate filler on the properties and structure of the composite was evaluated. The stability of the epoxy–sand composites in a harsh environment (deicing agent) was studied. The friction coefficients of the epoxy–sand composites were determined. It was found that a decrease in the filler concentration provides better resistance of the epoxy–sand composites to harsh environments and the best wear resistance.

A procedure and results of estimating the adhesion strength of a fiber–matrix system are presented. Carbon and basalt fibers are used, and a composition of epoxy resin and an amine solidifier is applied as a polymer matrix. The results of strength tests on the estimation of the adhesion strength by the pull-out method using two types of samples are presented: macro- and microsamples differ in the accuracy of determining the contact area between a fiber and the polymer matrix. The values of adhesion strength of microsamples based on elemental fibers are found to be lower than those of macrosamples, but the determination accuracy is substantially higher than that for the macrosamples.

Thermal analysis (TA) of modified gray cast iron (GCI) and vermicular graphite cast iron (VGCI) treated by foreign and domestic graphitizing and spheroidizing modifiers is conducted on a TA device using data processing software. Cooling curves (current temperature measured in solidification time, T–t) and the derivatives of the cooling curves (temperature change rates vs. the solidification time, dT/dt–t) have been constructed under the AO AVTOVAZ iron foundry conditions.