Level Of Mechanical Characteristics Research Articles

Metallurgical aspects in production of nickel high-temperature alloy disk blanks obtained by hot forging

The main metallurgical aspects that must be taken into account in the production of disk blanks with a diameter of up to 300 mm by hot forging are presented using the example of a nickel high-temperature alloy of the VZh179 type. The temperatures of phase transformations in the material under study are determined using the method of differential thermal analysis. On the basis of these data, the temperature-time modes of heat treatment of disk forgings are selected. The computer simulation of the hot forging process is carried out in the QForm 3D software package. The distribution fi elds of temperature and intensity of plastic deformation over the forging volume are determined. The optimal modes of hot forging and heat treatment of a nickel heat-resistant alloy are selected, which ensure high manufacturability and a level of mechanical characteristics that meets the requirements of technical specifications.

Deoxidation and modification of steels with reduced silicon content

The object of research is the processes that affect the mechanical characteristics of steels after the treatment of melts with silicon-free complex master alloys according to existing technologies. One of the most problematic places is the negative effect of silicon on the weldability of low-alloy steel, sharply increasing the heterogeneity of welds in sulfur and phosphorus and increasing their susceptibility to hot cracks. The cyclic strength of welded joints decreases markedly with an increase in the silicon concentration of steel. Also in this case, there is a threat of the formation of silicon monoxide, which significantly increases the fragility of the finished steel products. Also, steels processed with alloys containing silicon are prone to decarburization, the formation of surface defects during hot working and graphite formation, which reduces their endurance limit. In the research it was possible to prove that the use of silicon-free complex ligatures (SFCL) in smelting made it possible to obtain an increase (2–3 times) in the entire complex of mechanical and operational properties, especially ductility, impact strength at normal and negative test temperatures (cold resistance) , fatigue strength. In some cases, the level of properties of cast metal reaches the deformed version of its manufacture, for example, rolled products and even metal obtained by electroslag remelting. Processing of the melt of various BKL steels when tapping from the furnace into a pouring ladle instead of aluminum master alloys, silicocalcium and ferrocerium (according to the current technology) provided the required level and high stability of the mechanical properties of 20GML steel. Also, thanks to the use of BCL, it was possible to reduce the consumption of ligatures and deoxidizers by 4.2 kg per ton of liquid metal and increase the yield of rejection of casting defects by 6–10 %. It has been established in the work that BCL treatment leads to stabilization of the chemical composition, refinement of the grain structure of steels, as well as an increase in its dispersion and the level of mechanical characteristics.

Recycling of Cable Products

A process flow design for the processing of waste cable products into semi-finished products in the form of small copper chops is proposed. The proposed scheme, which eliminates requirement for melting operations, is based on the implementation of a number of special techniques in the preparation of raw materials with the subsequent application of briquetting, extrusion and drawing operations using annealing operations in the final segment. In the aggregate form, this approach provides for the production of rods and wires with the required level of mechanical characteristics and a reasonable combination of structural components, allowing the development of proposed areas of practical application of products made from recyclates.

Agglomerated flux for welding of corrosion-resistant high-strength nitrogen-containing steels

ABSTRACT The problems of Russian welding materials for welding highly alloyed austenitic steels that are not inclined to intergranular corrosion are considered. A new agglomerated flux for welding with austenitic welding materials is developed. Slag composition is selected that ensures a stable welding process, good separation of the slag crust and the formation of a seam. The possibility of introducing ferroalloys and metal powders through the flux ensures the necessary level of mechanical characteristics of the weld metal, and increases also the resistance of the weld metal to hot cracks and pore formation.

Perfection of the technology of corrosion-resistant sheet rolled stock production at JSC “Ural Steel”

Manufacturing of field oil pipelines require mainly pipes of 09ГСФ and 13ХФА steels, which correspond to the K52 class of strength. The pipe products and connection details of field oil- and oil products pipelines must meet increased requirements to their resistance against aggressive media, containing water and hydrogen sulfide. At the JSC “Ural Steel”, a unified comprehensive technology of production sheet rolled stock of 09ГСФ and 13ХФА steels in a wide range of assortment. The steels ensure the requirements to hydrogen fracturing as per NACE TM0284 and sulfide corrosion fracturing under stress method A of NACE TM0177 standard. The regimes of controlled sheet rolling with accelerated after-deformation cooling following by a high tempering elaborated. The technology regimes ensure necessary level of mechanical characteristics, corresponding to K52 class of strength. To ensure a satisfactory flatness of sheets, variants of the steels chemical composition depending on finished sheet thickness recommended. The elaborated production regimes ensure metal high resistance at low temperatures and actual value of the impact toughness KCV –40 exceeding considerably the standard requirements. It was shown, that decrease of relation Ca/S in the metal down to ~0,6–1,0 at Sulphur content less than 0.002% does not result in corrosion resistance decreasing and also minimizes the steel liquation inhomogeneity and contamination by non-metallic inclusions. The technology elaborated at JSC “Ural Steel” ensures the possibility of industrial production of corrosion-resistant rolled stock of 09ГСФ and 13ХФА steels in a wide range of assortment.

Submicronic nanostructured spherical zirconium-cerium powders for products of an orthopedic stomatology

The method of the ultrasonic spraying pyrolysis (USP) synthesized submicronic ceramic powders of structure of ZrO2+12 mol.%CeO2 intended for the subsequent manufacture on their basis of ceramic implants in an orthopedic stomatology. It is shown that (URP) allows to receive microspherical powders of zirconium-cerium ceramics, the multiparticle agglomerates having narrow dispersion and not forming in itself difficult the separable. The exemplars baked from new aerosol powders on the level of mechanical characteristics are close similar to characteristics for the ceramics manufactured of ultradispersed powders.

Effect of processing at the steel vacuum processing unit (SVPU) on desulfurization of unmodified and modified KP-2 steel

The object of the research is the processes of statistical processing of the chemical composition of KP-2 wheel steel. One of the most problematic places in the smelting of modern steel is the stability of the chemical composition due to the use of uncontrolled content of scrap, charge and standard modifiers, which are made by the fused method. To eliminate this problem, multifunctional modifiers were used during the study. This is due to the fact that the KP-2 steel modification method proposed in this article has a number of features. In this case, the influence modifiers of multifunctional action on the installation of vacuum processing of steel on desulfurization of wheel steel KP-2, obtained under the conditions of the open joint-stock company «Interpipe NTRP» (Dnipro, Ukraine), is established. In particular, when treating a steel melt with multifunctional modifiers, not only a refining effect occurs, but also an increase in the stability of the chemical composition and level of mechanical characteristics of the KP-2 wheeled steel. This is confirmed by the coefficients of variation and interfusion difference presented in the article (span), obtained by statistical processing of a large data set – 442 serial heats and 1 modified (6 wheels). Thanks to the multifunctional modification, the level of mechanical characteristics and the quality of the finished wheels really increases. Compared with similar mass-produced materials, such as FeSi, FeCa, FeMn, SiCa, the use of new multifunctional modifiers in KP-2 wheel steel provides a significant reduction in the mass fraction of sulfur than in the same metal that is processed in the traditional way. It is established that the use of multifunctional modifiers changes the shape of non-metallic inclusions to globular and reduces their number, which also increases the level of mechanical properties of KP-2 wheel steel. The obtained coefficients of variation prove that the mechanical characteristics of KP-2 modified steel are more stable than in serial melts of the same steel. This will increase the demand and quality of these railway wheels.

ВПЛИВ УМОВ ІЗОТЕРМІЧНОГО ГАРТУВАННЯ НА ПСЕВДОПРУЖНУ ПОВЕДІНКУ БЕЙНІТНОГО ЧАВУНУ


 
 
 
 Application of ductile cast iron ADI is feasible and cost-effective, provided that there is a clear understanding of the mechanisms for the formation of their high complex mechanical properties. The use of such materials for the production of variable parts of machinery, or in other units of automobile and machine building will significantly extend the life of the equipment. It is established that the level of mechanical characteristics of the ADI cast iron varies in full accordance with the theoretical concepts of the influence of the tempering temperature on the formation of mechanical properties of such materials. The previous plastic deformation does not affect the mechanism of formation of pseudo-elasticity. The tendency to dampening increases with an increase in the temperature of isothermal quenching. The damping behavior of a material is a consequence of the formation of pseudo-elastic twins in the structure of the transformed martensite.
 
 
 

Thermodynamic state parameters of a system as a prognostic factor of strength properties of composites with different natures of a surface

It is shown that, upon the modification of filler particles by a polymer film of the same nature as the polymer matrix, intermolecular bonds become stronger in a boundary layer between a polymer and a filler and the level of mechanical characteristics of polymer composite increases correspondingly. In order to ensure the working capacity of the metal-epoxy primer-polyethylene system, along with cohesive and adhesive properties of epoxide polymers, it is also necessary to take into account acid-base properties of solid metal and polymer surfaces.

Railroad rails made of bainitic steel

Results are presented from a study of the mechanical characteristics and microstructure of rails made at the Novokuznetsk Metallurgical Combine from steel alloyed with manganese, silicon, chromium, molybdenum, and vanadium. It was established that obtaining high strength and hardness in the steel by increasing its contents of carbon and alloying elements has an adverse effect on the service properties of rails made of steels with a bainitic structure. Normalizing is the most effective means of increasing strength and improving microstructure. The required level of mechanical characteristics can be obtained by tempering the steel at 350–370°C. The adverse effect of cold straightening-which is manifest in a reduction in the rails’s impact toughness-can be offset by subjecting the steel to preliminary tempering or normalizing and tempering. Rather than further increasing the strength of rail steel to improve its overall quality, this objective is better served by making sure that the steel is cleanly made, that the rails have little or no curvature, and that the residual stresses in the steel are favorably distributed.

Effects of nitriding on titanium alloy strength and plasticity

Studies have been made on the effects of temperature and time on nitriding and from the pressure of the nitrogen on the strength and plasticity of pseudo-α and α + β titanium alloys. Factors are observed that provide for retaining a high level of mechanical characteristics.