Papers by Keyword: Steel

Abstract: The results of the study on hydrogen diffusion through the metal membranes in the process of electrolytic hydrogenation and electron irradiation (energy of 40 keV , the current density is from 3 to 30 mA ) have been presented. It has been established that hydrogen release time from the membrane is determined by the parameters of the electron beam and its duration, and depends on the structure and the phase state of the metal membrane. The analysis of the hydrogen release time was done on a mass spectrometer connected to a vacuum chamber containing an electron gun and an electrolytic cell. The hydrogen diffusion coefficients when exposed to an electron beam were 2-3 times higher than under the same conditions without the electron beam irradiation. The results can be used in the technology of manufacturing of new materials with desired properties.

Abstract: This paper is devoted to the comparison of theoretically defined solidus and liquidus temperatures based on above mentioned theoretical methods with the results of high-temperature thermal analysis carried out on two devices (Netzsch STA 449 F3 Jupiter; Setaram SETSYS 18_TM). On large samples (23 g), the method of direct thermal analysis was applied. On small samples (200 mg), the experiments using differential thermal analysis were realized. It was found out that the solidus and liquidus temperatures for the studied steel grade can vary in dependence on the used determination method. The used methodology of thermal analysis is fully reproducible, and the these thermo-analytical results can be considered as necessary for the correct setting of critical parameters in applied research on the process of steel casting.

Abstract: The research on the process of steel filtration from non-metallic inclusions is currently entering the last phase of industrial experiments. Their positive effects confirm the previous theoretical assumptions and laboratory tests. The application of steel filtration as a permanent technological operation in the process of steel casting will remarkably improve its metallurgic purity. An additional advantage will be diminishing the probability of covering the outlet nozzle of a tundish. This paper presents an outline of the experiment results mentioned above.

Abstract: The present study aimed to explore possible thermal processing conditions of a steel AISI 43100, seeking the best combination of properties, especially strength and ductility. Different routes of heat treatments for continuous cooling were applied to the material, and the mechanical properties were evaluated by tensile and hardness tests. The microstructure and fracture micromechanisms were characterized by scanning electron microscopy (SEM). It was observed a strong influence of cooling rate on the formation of microstructure, reflecting directly in mechanical properties.

Abstract: In Petrobrás SA refineries, there are thousands of heat exchangers in which cooling water is treated for recycling, often by outsourced companies. In all of these refineries there happens shutdown for corrective maintenance of the exchangers by problems related to corrosion caused by the cooling water, requiring about four days to repair a unit. The shutdown of a production line results in loss of revenue between U$ 200,000.00 and U$ 300,000.00 per day. To control the cooling water quality, it is used coupons for corrosion analysis. Tests are limited to visual inspection and by mass loss analysis. In this work, inhibitors such as sodium nitrite, sodium dichromate and benzoic acid are used to protect metals immersed in water in order to avoid the corrosion and consequently the shutdown of the exchanger for corrective maintenance.

Abstract: A new method for combined thermo-mechanical treatment of steel 0.4 % C, 1.5 % Cr, 1.5 % Ni, 0.5 % Mo is developed. Thermo-mechanical processing includes hot forging and rapid cooling to the temperature range between the beginning and end of martensitic transformation. The final stage of heat treatment is heating up to the temperature of bainite transformation in which the remaining austenite transforms into a bainite structure and previously formed martensite tempers. In comparison with well known techniques of thermal treatment, the developed thermo-mechanical treatment increases the impact toughness of the steel by 2 times and fatigue crack resistance by 6 times (with equal values of strength parameters). The technological process of high-temperature thermo-mechanical treatment is recommended for treatment of high-strength blank forging.

Abstract: The possibility of obtaining of surface layers on low-carbon steel 20 by high-energy methods is shown. The features of structure formation in the surface layers after atmospheric electron-beam deposition of iron-graphite powder mixture and high-frequency current treatment are considered. It is shown that coatings with thickness of 2.6 mm and hardness of up to 8000 MPa are formed during atmospheric electron beam deposition. High-frequency current treatment allows to obtain coatings with thickness from 500 to 1600 μm, which hardness reaches 7000 MPa. Hardness increased is due to the formation of hypoeutectic cast iron structure or hypereutectoid steel during high-energy treatment, depending on the processing modes. It is expected that the increase in surface hardness will positively affect the wear resistance of high-carbon coatings.

Abstract: Structural investigations of steel surface layers alloyed with vanadium, titanium and graphite were carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis methods. Coatings were obtained by high-energy electron beam treatment. The titanium – vanadium ratio in initial powder mixtures was as 2:1, 1:1 and 1:2. TiC, a-Fe (ferrite), eutectic consisted of VC and a-Fe were the main structural components of the coating: With an increase of vanadium content shapeless TiC particles turned into dendritic; tertiary dendritic arms consisted of VC. In addition, it also resulted in an increase of carbide particle sizes. The volume fraction of strengthening particles in all coatings was approximately identical (18 %).

Abstract: The content of this paper are possibilities of using round timber in various public facilities structures (e.g. children ́s playgrounds) and in engineering constructions (e.g. watchtowers, bridges and footbridges). Specific problems of designing round timber structures, mainly in joints, are presented here.

Abstract: The PVD magnetron sputtering method is one of the most efficient methods enabling the spraying of the multi-component materials and almost unlimited setting of the chemical composition of coatings. The micro-and nanocrystalline coating structure favours the selective diffusion of chromium and other alloy additions that form compact oxide layers. The paper presents the study of coatings made in the process of magnetron sputtering of AISI310S grade chromium-nickel steel. The study covered coatings of the steel's composition with additions of 2-5% Si and of 2-5% Al. The resistance of the coatings at temperatures induced by electric current flow was assessed. The coatings provided a resistance element in the electric circuit, and the measurementof their temperature was made by the voltage drop indirect method. It was found that the steel coatings had a resistance of 0.176 Ω within the entire range of testing temperature, and their failure occurred at a temperature of 350°C due to cracking and delamination from the substrate. Introducing the Si or Al addition to the coatings resulted in an increase in coating resistance and temperature stability, respectively, to 450 and 400°C. Changes of coating’s phase composition and texture were not found. The resistance of the coatings with the Al and Si additions decreased with temperature due to their oxidation.