Papers by Keyword: Hardening

Abstract: During the operation of porcelain stoneware sometimes there is a type of defects associated with crumbling from the edge of tile. In addition, cracks occur when a small object is fallen and during transportation of the products. Compared to conventional ceramic floor tiles, porcelain stoneware has increased strength, which explains its high price. The brittle failure is most likely, due to the hardening of glassy phase of tiles during cooling stage of the firing process. As a rule, the quenching temperature depends on the chemical composition of the glassy phase formed during firing. Both the phase and chemical composition of porcelain stoneware, and the chemical composition of the glassy phase are determined.

Abstract: The paper considered the peculiarities of the numerical mathematical modeling of gradient hardening processes under conditions of complex local loading of the center of deformation. The authors described the mathematical model. They presented the results of modeling in the form of a picture of the change in Odkvist parameter with an increase in the number of passes. Data were given on the comparison of the results of experimental work and mathematical modeling.

Abstract: The purpose of this work is to study the structure and mechanical properties of an aluminum – magnesium system alloy after various types of heat treatment (quenching and ageing). The microstructure of an alloy has been studied by means of Zeiss OBSERVER.D1m microscope combined with a camera and image display on a monitor screen. Micro X-ray spectral analysis was performed by means of Carl Zeiss EVO 50 scanning electron microscope. The micro-hardness of the samples has been measured on prepared metallographic sections by means of DM8 micro-hardness meter. In the course of the process it has been found that quenching the Al-12,78% Mg alloy from temperatures of 430–440 ° C does not lead to the formation of a single-phase solid solution. Ageing at 100 ° C enables the formation of secondary phases. It was noted that with an increase in the quenching temperature, the micro-hardness increases slightly. An increase in the exposure time doesn’t influence greatly the micro-hardness of the alloy, while the structure remains practically unchanged.

Abstract: This work is devoted to the study of the influence of technological parameters of electrolytic-plasma surface quenching (EPQ) on the structure and surface properties of samples of bandage steel 2. In the electrolytic-plasma treatment, we performed the cathode mode in an electrolyte containing an aqueous solution of 20% carbamide (NH₂)₂CO and 20% sodium carbonate Na₂CO₃, on the installation of EPO with appropriate technological processing conditions. According to the electron-optical, X-ray phase studies, the phase composition of the steel after the EPQ was determined this differs from the initial one by the formation of cementite and iron oxides on the surface of the samples. It is established that the microhardness of the bandage steel 2 after the EPQ during heating for 4 seconds increases 2.4 times in comparison with the initial state.

Abstract: The article presents information on the technological characteristics and industrial use of chroming electrolytes. The modern electrochemical technologies of repairing worn-out parts of agricultural machinery are considered. Particular attention is paid to the use of chrome plating methods making possible to increase the durability and reliability of the parts recovered in electrolytes of different composition, allowing to obtain coatings with high physical-mechanical properties that determine their suitability for the operation in the process of use for their intended purpose. The use of self-regulating dilute chroming electrolytes makes possible to increase the productivity of the deposition process of chromium coatings significantly, to obtain high-quality coatings of chromium and iron, and high adhesion to the base material - carbon, alloyed steels, and cast iron. The deposition of metals using reverse, pulsed currents with adjustable anodic-cathodic ratio of amplitude values and its duration allows to influence electro crystallization, control the structure, texture and roughness of the formed precipitate, which makes possible to get with predetermined functional physical and mechanical properties for specific repair conditions and subsequent operation in agricultural machinery. The following modes are recommended for brilliant coatings: when reverse current τ (cat) / τ (an) = 50-70, τ (cat) = 4-7 min, D(cat) = 40-100 А / dm2, D(cat) / D(an) = 3-4, Т = 60-65 ° С; when impulse current D(cat) = 40-100 А / dm2, Т = 60-65 ° С, τ (imp) = 1.5-2.5 min, τ (pauses) = 5-10 sec., impulse ratio 1.07-1.15.

Abstract: The strain-hardening ability has been estimated using a methodologically simple engineering criterion. A simple engineering method estimates the ability of metals and alloys to strain-hardening by the hardness increase determining. The Rockwell hardness has been measured at the bottom of the indentation cup of the Brinell press indenter. The strain-hardening tendency is investigated by the “two hardness-measuring instruments” method for two austenitic manganese steels, 110G13L and 110G6L, with different austenite stability to strain martensitic transformation. This hardness estimating method can be applied without making special samples and using deforming equipment.

Abstract: In this article the experimental data of the hardness and wear resistance of chrome-manganese steels 35H3G2F and 35HGF, which are cemented in a highly active paste-like carburizer and hardened at various temperatures, are presented. Cementation and high temperature carbonitriding of these steels leads to a high content of the carbide phase in the diffuse layers and an increase of hardness and wear resistance. The effect of carbides on the hardenability of diffuse layers are investigated. The hardening temperature ranges of these steels and the effect of alloying elements on hardness are established. The mechanism of the phase formation of the highest hardness structures is described. The carbides influence on the wear mechanism of cemented in various modes steels is studied.

Abstract: The superficial microstructure, received by laser processing, is characterized by a high density of defects of a crystal structure and incompleteness of thermal phase and structural transformations. The degree of a neravnovesnost of such a structure can be estimated by means of multifractal ranges. As a measure for calculation of multifractals, it is possible to use any quantitative structural index, in particular, the area of microstructural objects, their perimeter and density of borders. The most informative is density of borders, which considers the area and perimeter of structural object. Microstructures of stainless steel 12kh18n10t in an initial state, after laser processing and a local laser alloying by hard-alloy powder from BK8 were investigated. Calculations of complex indicators of the structural organization of material, which showed, are executed on the basis of the multifratalnykh of ranges, that laser processing leads to, increase of orderliness and frequency. It indicates high degree of a neravnovesnost with which increase hardening increases.

Abstract: The article presents the results of a study of the effect of synthesized microdisperse additives of crystalline hydrates based on calcium sulfoaluminates on the properties of cement stone. The effectiveness of the use of a rotary pulsation apparatus (RPA) to obtain microdispersed additives is identified. The possibility of accelerating the hardening of cement stone by entering microdispersed additives into its composition is shown. It has been established that in the presence of microdispersed additives of crystalline hydrates in the cement stone, the phase composition of hydrate tumors changes, the amount of calcium hydrosilicates and ettringite increases, the porosity decreases and the strength of the cement stone increases. This provision is confirmed by the increase in the degree of cement hydration, the amount of bound water in all periods of hardening of the stone. It is proposed to use microdisperse additives, which play the role of primers for the crystallization of ettringite and calcium hydrosilicates, to increase the strength of cement stone in the early stages of hardening.

Abstract: The article presents physical regularities for the formation of the surface layer microgeometry of the parts while edge cutting machining of steels from the standpoint of the metal temperature strength and the dislocation-energy concept of the metals failure in the process of cutting. It is proposed to employ an approach that contemplates the use of the informative ability of the thermo-emf signal as an integrated index for the thermophysical properties of a workpiece and a tool in mathematical relations as per roughness parameter calculation.