Papers by Keyword: Galvanizing

Abstract: The article is devoted to a comparative analysis of the technological processes of nanogalvanizing, in terms of composition and microstructure of diffusion zinc coatings, to obtain the necessary corrosion and mechanical properties. Three industrial processes have been considered, it is shown that they give a range of composition profiles and microstructure types for the coating. Based on the results of the analysis, promising areas of technology application are identified.

Abstract: An urgent need has been identified, associated with the validity of improving the process for the manufacturing of galvanized steel, in the analysis and improvement of each stage of production in the conditions of the particular cold-rolled shop of the Iron and Steel Work. As a novelty, the processes and equipment for cleaning a hot-rolled strip, pickling a strip, rolling of pickled strips, physicochemical surface treatment, zinc coating, passivation, and other elements were reviewed from the point of view of possible corrosion consequences of the production. For the first time in the considered production system, elements and operations, their errors and imperfections, which can lead to poor-quality coating, violation of the zinc layer and reasons that contribute to the corrosion of galvanized metal products in the future, were identified at each stage.

Abstract: The paper presents a new technological scheme for obtaining bimetallic materials of the composition "aluminum casting alloy - sintered iron powder" by the method of joint stamping. The results of experimental studies of the effect of process conditions on the physicomechanical properties of the starting materials and the adhesive strength of the final bimetal blank are presented.

Abstract: The galvanized steel structures may be inevitably corroded rapidly in the case of exposed to corrosive environments for long time, and these corrosive environments has been accelerated with increasing the environmental contamination due to the rapid development of industrial society. However, since the galvanizing method have the various merits compared to surface coating treatment in economical point of view, the galvanized steel have been extensively used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and various industrial fields etc.. Therefore, it has been made an effort to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, comparison evaluation on the corrosion resistance of three types of the test specimens, that is, three samples of pure galvanizing, galvalume and chromate treatment were investigated using electrochemical methods in 1% NaOH solution. The samples of chromate treatment and of galvalume exhibited the lowest and highest corrosion current density respectively in 1% NaOH solution. In addition, the sample of chromate treatment revealed the highest impedance at 0.01Hz, which is considered that the oxide film by chromate treatment is deposited on the surface of pure galvanizing sample. After drawing polarization curves, the corroded surface of the pure galvanizing specimen indicated pattern like as localized corrosion, moreover, the large amount of corrosive products was observed on the surface of galvalume sample. However, the smooth pattern nearly similar to general corrosion was observed at the corroded surface of the sample of chromate treatment. Consequently, it is considered that the chromate treatment is an optimum method compared to pure galvanizing and, galvalume treatment to improve corrosion resistance in 1% NaOH solution.

Abstract: The results of the studies of phase formation and the structural state of diffusional zinc coatings formed in zinc powder with nanocrystallized surface of the particles are presented. The sequence of iron-zinc phases formation during the process has been established, which is the reciprocal of those obtained during the annealing of "hot dip" coatings. The microstructure of δ-phase in the coating, a change in its texture and structural parameters through the thickness of the coating have been studied.

Abstract: The features of the growth and the structure of diffusion zinc coatings in the process of galvanizing in powders with nanocrystallized surface area, alloyed with iron, are studied. It is established that the increase in the iron content in the powder substantially increases the area of the zinc solid solution in iron at a constant speed rate of the layer of zinc-iron phases. This effect is accompanied by the change in the morphology of powder particles as a result of iron saturation.

Abstract: s In this study, Computational Fluid Dynamics (CFD) was used to simulate the flow and temperature distribution in zinc pot of hot-dip galvanizing process. The flow and temperature distribution in a base-case zinc pot was compared to that in other two optimized zinc pots, one of which had a dam between ingot and snout and another one had a reduced heating power. The simulation shows that the dam impedes the flow of low temperature liquid zinc around zinc ingot to strip and increases the fluctuation of zinc level. By reducing the heating power, however, the fluctuation of zinc level could be suppressed.

Abstract: Article presents the state of knowledge relating occurrences of liquid metals embrittlement. The results of experimental investigations of the LME phenomenon, reasons of its formation and influence of different parameters are described. In order to determine the basic mechanical properties of materials intended for research static tensile test was performed. Samples made of C66D and C70D steels with tensions stretching (500-800 MPa) at different values and kinds of loading during the hot dip metallization were investigated. Coating processes were made in zinc with 0.5% Bi addition and results were compared to zinc coating. The processes of hot dip metallization were done at 450°C temperature and immersion time 180 s. Coated samples were investigated by light microscope to specify possibility appear of LME effect.

Abstract: The paper presents the results of research on surface condition of zinc coatings. Profilometric studies were performed for zinc coatings formed in industrial continuous hot-dip galvanization process and for the same coatings after two years of use. The results include the geometrical shape of 2D and 3D surfaces, distribution of vertices on the surface and roughness and waviness profiles. The parameters R_a, R_z, S_a and S_z were used to define the surface roughness. The study was conducted using FRT Microprof optical profilometer with data acquisition and analysis by MARK III software package.

Abstract: The microstructures and mechanical properties of a high carbon DP steel and a low carbon Nb microalloying DP steel were investigated. The two types of DP steels have both qualified to meet European standard performance. But the high carbon content DP steel exhibits relatively low elongation and low hole expansion rate as well as poor bending performance. The martensite island in high carbon DP steel appears obvious band structure, and the size of martensite islands is big. Contrary, the matensite islands in low carbon and Nb microalloying DP steel are dispersed and fine, which lead to perfect comprehensive performance.