Papers by Keyword: Hardening

Abstract: Carburizing is a method for obtaining a sturdy material surface. This hard surface is used for machine elements that intersect with other materials, so failure due to wear can be avoided. However, this increase in hardness has always been followed by decreased ductility. This condition certainly lowers the fatigue life of the material. For that, it is necessary to compromise between surface hardness and ductility. This study used AISI 1045 steel, which has a surface roughness of 0.4 and 4.7 μm with carburation media used, is a mixture of 80% coconut shell charcoal and 20% Barium carbonate. The sample was given the pack carburization treatment at 850°C and holding time for 3 hours, and then cooled in the open air. The samples were reheated at 850°C, holding time for 17 minutes, and then cooled with airflow at speeds of 10.34, 15.51, and 20.06 m/s for 30 minutes. This research shows that the surface of steel with a roughness of 0.4 μm has excellent performance with the hardness and corrosion level respectively 228.6 HV and 2.3586 mpy at cooling airflow rate of 20.06 m/s while the fatigue life of material occurs at the speed of airflow cooling 10.43 m/s.

Abstract: The article considers issues of increasing wear resistance of cast iron products by methods of thermochemical treatment of their surface layer. Methods are proposed to solve the problem of wear from cast iron of grade EN-JS1060 due to development of technological processes of strengthening treatment. Alternative versions of strengthening technologies are represented by nitrocarburizing, liquid nitriding and carbonitration. Results of examination of control samples at increasing loads after 200 N before catastrophic wear are given. Comparative analysis of these results showed that samples after carbonitration and liquid nitriding had the greatest bearing capacity (1000 N). Carbonitration is selected as a most preferred option of the surface hardening treatment. Non-poisonous cyanoacid salts are used to realize it.

Abstract: The article deals with the problems of withstanding harsh temperatures by steel and iron. The authors of the work discuss iron denser high-temperature of γ modification and maximums and minimums of impact. In addition, the article analyses the transformations of iron and anomalies of properties: peak of heat capacity, acceleration of diffusion, etc. The authors take into account the consensus on the causes of polymorphism and the theoretical model of ferromagnetism. Besides, there is a consideration of "transformation" in interaction between Fe atoms that produce anomalies of steel properties. It is necessary to note the transformation detected by anomalies of any properties including mechanical. In the presented work the authors have made an attempt to prove transformations in iron at ~650 °C on the basis of extreme values of hardness and microhardness, metallographic structure, parameters of fine structure, precipitation resistance force depending on temperature. Therefore, the analysis of literature sources on physical and mechanical properties of iron and its derivatives has been made.

Abstract: This research examines the effect of size and weight fraction of the eggshell particles added on the hardening of the Al metal reinforced by eggshell Particles using the program MINITAB 16. Powder technology method has been used to produce a composite material, The composite material was obtained by adding different weight fractions (0,2, 6,10 and 12 wt. %) and the size (100,240,350,510and 670um) of eggshell particles to aluminum powder. It samples was composed by using pressing of single action then accompanied directly by process of sintering at 474°C under the inert gas effect conditions. it was concluded that the best hardening of (72.6971 Mpa) can be obtained when the variables were (Xi = 12 wt%) and (X2 =100um). The lights value of Xi and X2, obtained using the programs, was used in practice giving hardening (74Mpa) which it nearly similar to that obtained by program. Also results show that the variables weight fraction (X1) & Particle Size (X2) have a significant effect on hardening. Moreover, the hardening increases with increasing weight fraction. While hardening value decreases gradient with down eggshell particle size.

Abstract: The study is aimed at surface strengthening of jewelry tools. Samples in the form of a tool with a flat and curved surface profile are considered. Macrophotographs of jewelry korneisen at different stages of wear, as well as after restoration and strengthening are given. The results of the influence of chemical-thermal and thermo-friction treatments on the structure and properties of U7 and U8A steels used for jewelry tools are presented. The methodology of experimental researches is given. The equipment used for each of the hardening methods investigated in this work is considered. Auxiliary media and features of sample preparation for the experiment are also described. Photos of samples and some equipment at different stages of the study are given. Data on the distribution of microhardness, photographs of microstructures in cross section of samples after different types of hardening are presented. A comparison of the strengthening efficiency of the samples after the use of different processing methods is performed.

Abstract: The results of a study of the influence of shapes of samples, as well as the presence of internal cavities and their shapes, on the nature of wave strain hardening (WSH) are presented. The peculiarity of the method lies in the impact of a stream of pulses on the processed material, while instant wave states, which affect the microhardness maps in the workpiece are formed in the material. These studies were carried out for the first time on a specially designed stand. The studied grades of materials were: steel 45 and bronze BRAZH 9-4. As a result of the studies performed, the geometric shape of the samples and cavities in them was revealed, which contribute to an increase in microhardness.

Abstract: The purpose of the study is to study the possibility of using secondary resources of metallurgical production, namely: steel-making slag and carbon dioxide in the production of vibropress products for construction purposes. The tests were carried out with the complete replacement of the coarse aggregate in the concrete mixture with steelmaking slag and varying the hardening processes. The optimal condition for strength gain is hardening in carbon dioxide at an increased pressure of 0,2 MPa.

Abstract: The solution to the problem of large industrial cities with a developed metallurgical industry is the creation of environmentally friendly conditions for the life of the population through the disposal of industrial waste. The studies carried out have shown that the developed technology makes it possible to widely use steel-making slags and carbon dioxide emitted into the atmosphere in the production of small-piece wall stones with high operational properties. It is shown that only slag is required to obtain wall material without the use of a hydraulic binder.

Abstract: The article discusses the existing theories of physical and chemical processes occurring in artificial stone based on a cement binder, affecting the dynamics of strength gain. A mathematical model of the continuously increasing strength of the cement stone according to the logarithmic law has been investigated. The authors questioned the adequacy of the application of such theories to exclude the factor of hardening time from experiments aimed at identifying the effect of such measures as the use of surfactants, mineral additives, changes in the water-cement ratio, etc., on the strength gain. The authors proposed to study the influence of such factors on the dynamics of changes in the strength of cement stone as a more efficient tool. The main arguments of the theory of abrupt strength gain and destruction of cement systems are presented. The authors planned an experiment to plot the dynamics of the strength gain of an artificial stone based on a cement binder to assess the relevance of the problem. During the experiment, two batches of specimens were tested, six specimens in each at 3-, 7-, 14-, 28-, 56-and 84-day age, respectively. The values obtained during the experiment showed significant differences at an early age of hardening. The theoretical curves of variation of strength in time were obtained based on the experimental data, within the framework of the existing theory of the strength gain of an artificial stone based on a cement binder. The simulation results were compared with the experimental results and with each other. The arguments were put forward for and against existing theories based on the results of the analysis of experimental studies and theoretical calculations.

Abstract: The sharp side of a steel axe is often broken. This part is usually forged into a tapered shape until the front edge is thin and sharp. The purpose of this study was to determine the effect of tempering on the structure and hardness of a steel axe made of AISI 5160 leaf spring steel which has undergone a forging and hardening process. The as-received samples were obtained from a commercial market after undergoing a forging process to reduce their thickness from 10 mm to 5.5 mm in the base part and 1 mm in the front edge part. The hardening process was carried out by heating the samples at a temperature of 850 °C followed by rapid cooling in an isorapid oil. The samples were then tempered with tempering temperatures of 300 °C, 350 °C, and 400 °C. The hardness of the tempered samples was evaluated using a Vickers microhardness tester in three different locations; the base, the middle, and the front edge of the tapered samples. To analyze the property change, the microstructure of the tempered samples was observed using SEM and EDS. The result showed that the hardness of the samples decreased with the increase in tempering temperature. The hardness of the front edge was higher than that of the middle and base part of the tempered samples. The faster cooling rate inside the thinner part was responsible for the higher hardness. The microstructure showed that the martensitic structure that emerged after the hardening process turned into fine tempered martensitic and secondary carbides. The size and amount of carbides increased with increasing tempering temperature