Papers by Keyword: Slags

Abstract: The study of the influence of the physical and mechanical properties of concrete on various hydraulic binders on the corrosion resistance of steel reinforcement has been carried out. As a binder, the following were considered: CEM I 42.5 N and a slag-alkaline binder (SAB) based on ground granulated blast-furnace slag of Novolipetsk Metallurgical Plant (NMP). For comparative tests, concretes of class B 25 (M300) were used on granite aggregate with a fraction of 2,5-7,5 mm. Indicators of physical and mechanical properties such as: compressive strength, porosity, water absorption coefficient and weight loss coefficient of reinforcement at the age of 28, 90 and 180 days are criterial. 5 % aqueous solutions of NaCl, Na₂S0₄ were used as working media in assessing the corrosion resistance of reinforcing steel; MgS0₄. It has been established that steel reinforcement in slag-base concrete (SBC) has high corrosion resistance, both in an aqueous solution of NaCl and in solutions of Na₂S0₄ and MgSO₄. Slag-alkali concretes are characterized by low porosity, lower water absorption coefficient in comparison with concretes based on Portland cement.

Abstract: It has been demonstrated that shock-vibrating activation of minerals is a prospective method to impact the ore; it may be used to intensify chemical and physical-chemical processes of mineral raw material processing and preparation. Differences in the composition and phase properties, obtained both in terms of continuous and periodic modes, are in the fact that in the first case loadings deal with interlayer space preserving layered nature of the mineral. When the mode is continuous, then the disturbances cover the octahedral layer though elementary constituent – tetrahedrons – are preserved. It has emerged that the most important advantage of high reacting capability of activated minerals is in the fact that leaching of some ores may be performed in chlorhydric acid at the expense of transformation of some silicate components into a specific state – loose packing of basic silicate chain. Consequently, shock-vibrating activation has become a basis to develop a method of leaching process intensification as well as a method to control phase formation.

Abstract: The aim of this work is to study the difference between the crystalline phases of used fluxes and obtained slags after Shielded Metal Arc Welding (SMAW). It is well known that The weld pool solidifies into the weld metal while the lighter molten flux floats on the top surface and solidifies as a slag layer that can be easily removed .The effects of individual flux ingredients as well as their interaction effects on weld metal composition have been investigated in this paper. The mass concentrations between fluxes (FA, FB and FC) and slags (SA, SB and SC) summarize the physico-chemical behavior of elements transfer between base metal, filler metal, flux and slag forming during welding of pipelines by SMAW process. The analysis of different fluxes phases and slags by X-ray diffraction allowed to detect the presence of different crystalline phases, which were formed at low temperature (T <1000°C) heat treatments, and during fluxes confection. As for the slags, the presence of new crystalline phases which have been formed at high temperatures.

Abstract: It has been demonstrated that vibratory impact mineral loading results in the formation of solid solutions. A technique to determine concentration dependence of inversion degree of solid binary solutions according to the known values of their components activity has been proposed. Values of thermodynamic functions of the solutions mixing in terms of statistic formulas as well as by means of immediate processing of the experiment have been determined.

Abstract: In order to Figure the common defect in large section special steel forging and find the solution, systematic study was carried out on hundreds of large section special steel forgings in a domestic famous steel mill. The steels included: low-carbon steel Q345D/E, medium-carbon steel 27SiMn, high-carbon steel GCr15SiMn, stainless steel 20Cr13. Both the amount and type of all the defect in the above steel were calculated and analyzed. The results showed that the common defects of the steel were slags, inclusions, loose (cavity) and inner cracks. The evolution of the cavity in the ingot during forging process was simulated by a numerical simulation software Deform-3D. The inner cracks in Q345D/E and 27SiMn initiated after A→F+P transformation The cracks in GCr15SiMn formed after the precipitation of net-like proeutectoid carbides. The cracks in 20Cr13 formed after the precipitation of net-like carbides. The internal cause of the cracks was relevant to composition segregation and internal stress in the forging. The external cause was connected with effect of slow cooling. Based on the above study, a set of new process was proposed and put into industrial application, with the result that the qualified ratio of flaw inspection in the above steel mill was improved from 20% to above 87%.

Abstract: Diffusion phenomena are of great importance in materials processing wherein atomic, molecular or ionic species are distributed within a phase or among different phases. Though the phenomenological equation describing the diffusion phenomena including the bulk flow arising out of diffusion in fluid and the phenomena of Kirkendall shift in substitutional solids are the same, these processes are often treated independently. Some discussion on this aspect is presented in the theoretical aspects of diffusion. Owing to the complexity of atomic interactions, prediction of diffusion coefficients in condensed systems from first principles may not be that reliable; Experimental determination of diffusion coefficients is essential. In the second section, some novel experimental techniques developed recently to measure diffusion coefficients in the solid state as well as liquid systems including those in slags are described. In the last section, two case studies on application of diffusion phenomena in process metallurgy are presented emphasizing the importance of these in metallurgical processing.

Abstract: The MgO-C bricks are extensively used as lining work on different steel containers. Due to the high temperatures of the process, these refractories are subjected to severe wear and corrosion processes, principally in the area of contact with the slag. These slags have variable contents of CaO, SiO₂, Al₂O₃, MgO and FeO, varying in composition according to the process stage. In this paper, cup tests were performed at 1650 °C during 2 hours in air, using two commercial MgO-C bricks. They were put in contact with two different grades of slags, one with high basicity (HB) and the other rich in FeO (RF). The corrosion degree suffered by the refractory materials were analyzed and compared. Microstructural observations were performed in order to postulate the probable corrosion mechanisms acting on each material. The results establish that, in the case of HB slag, the attack is carried mainly through the filler region (matrix). In the case of RF slag attack, it is observed that Fe is the main specie that diffuses through the matrix area of the bricks, and to a lesser extent through MgO grains. In both cases, the quality of the raw material used in manufacturing each refractory bricks, be playing an important role in the corrosion degree.