Search

The acid and ammoniacal-carbonate hydrometallurgical industrial processes of the Cuban nickeliferous mines produce yearly, thousands tons of solid wastes, which are dumped in big waste dams that pollute the environment and, besides, they occupy big extensions of possible cultivated land areas. These hydrometallurgical tailings present appreciable contents of various minerals, which contain iron, aluminum, chrome, nickel, silicon, among other heavy metal elements. These nickel-ferriferous wastes constitute an attractive raw material source, which can be useful to obtain products of substantial demands and high use value. The aluminothermic process, using wastes (shavings and sawdust) of the aluminum carpentry and this metal's scrap, offers an attractive metallurgical method for the elaboration of the nickeliferous solid waste. Aluminopyrometallurgical process offers commendable economic and energetic saving advantages and, besides, does not produce residual solids; therefore, this method belongs to the cleaner-production range. By means of the aluminothermic process of these nickeliferous tailings, a similar metal to a white iron and a slag of alumina and various spiels type with high grade of abrasion are simultaneously obtained. [ABSTRACT FROM AUTHOR]

The raw materials traditionally used as sources of chromium carriers (ferrochromium, chromium oxide and chromium powder) in application chromizing processes present a high price and some difficulties for ferrochromium grinding. In this work there is an assessment of the effect that has the use of the products of a reduction aluminothermic chromium concentrate on the characteristics and properties of diffusive chromium carbide complex coatings. To assess the coatings optical microscopy, micro - hardness test, Ray - X diffractometry and Energy Dispersive Ray - X Spectroscopy was used. It has determined that the implementation of diffusive treatments using a treatment regimen of 1 000 °C - 4 h giving complex carbides chromium coatings in three substrates researched (AISI 1055 steel, W108 tool steel and grey cast iron). The layers do not differ by their morphology of those reported in previous work and are characterized as having similar levels of microhardness and similar or high thicknessesthat achieved using conventional sources carrying chromium in chromizing. Also coatings are highlighted by high contents of chrome that possess (among 65 and 71 % for steel AISI 1055). In addition, it was found that mixtures of products made with the reduction of chromium concentrate possess the ability to make chromium necessary for the normal development diffusive process with a durability of at least four processes without the need for its revival, for the experimental conditions used. [ABSTRACT FROM AUTHOR]

In many ore deposits chromium is present as complex oxides known as chromospineless which show high chemical stability especially towards halides, affecting negatively its possible use as a chromium source in diffusive treatments. In this work, the aluminothermy reduction of one chromite concentrate from Merceditas deposit was studied and their products were characterized, with the objective of using it as raw material in chromizing. In order to make the grain size analysis, two samples were prepared. First the concentrate was crushed in a ball mill and later was screened in two sieve sets, with maximum openings of 100 and 200 µm . The mixture of the reduction products of the concentrate was characterized, using RX difractometry and infrared spectroscopy. It was corroborated that when using treatment D (55 mm; 4 h; 950 °C), the metallic aluminum peaks disappears; the relative intensity of chromopicotite diminished and the higher relative intensity of reflection peaks were occupied by chromium and ferrochromium. These results allow to anticipate that the resulting compound is suitable as chromium source in diffusive treatments. [ABSTRACT FROM AUTHOR]

In this work it is carried out an assessment of the influence of the carbon contents in the base metal on the morphology of carbide layers and adjacent zones, which were obtained by using refractory saturate mixture elaborated from refractory chromite for steels AISI 1045, AISI 1055 W108 and gray cast iron. It is also analyzed the effect of carbon content in the base metal on the depth, micro-hardness values and phase composition of the carbide layer achieved for those steels. The carbide coatings obtained are defined for to be maximum micro-hardness values of » 1600 Hv20, levels depths among 9-23 mm (for an exposition regime of 1 000 °C-4 h), and due to the fact that they are formed by (Cr, Fe)23C6 y (Cr, Fe)7 C3 phase. [ABSTRACT FROM AUTHOR]

In this paper it is exposed the obtention of concentrating of the zeolitic phases by means of centrifuge with heavy liquids starting from the zeolitic cryptocrystalline rock. By means of the results of the chemical analysis of the zeolitic concentrated and the x-ray diffraction, the crystalochemical formulas of zeolitic mineral of Tasajera deposit rocks are determined, as well as their solid product (seudofaujasite), obtained from the hydrothermal basic reaction the concentrated was subject of. An assessment of the ionic exchange capacities of the zeolitic mineral and of its hydrothermal solid product is made, being based on the crystallochemical formulas and on the experimental results. Lastly, the hydrothermal reaction is formulated and by means of it is determined experimentally the efficiency of this hydrothermal process experimentally. [ABSTRACT FROM AUTHOR]

The article points out some health risks caused during the welding process, a well extended work in the sugar industry. It makes emphasis on health damages caused by the resulting smoke of this process, and it provides some of the necessary measures for avoiding or diminishing these hazardous effects. [ABSTRACT FROM AUTHOR]

This paper shows a valuation of different methodologies used to calculate the Transfer Coefficients (Kt) of alloy elements during the metallurgist process of Submerged Arc Welding taking in account the contribution of alloy elements starting from flux and from the wire-electrode. It is experimentally determined the chromium and manganese Kt in ceramic and commercial HF-600 flux. [ABSTRACT FROM AUTHOR]

The present work approaches the obtaining of manganese flux to be used in Submerged Arc Welding (SAW). This study starts with a transformation of a manganese mineral by the increase of temperature and the addition of other minerals. These conditions modify the binary system MnO-SiO2 and the behavior of the flux. A comparative analysis of the technological behavior of the flux during the welding process as well as the chemical and mechanical properties of the junctures in relation with trademark fluxes are presented. [ABSTRACT FROM AUTHOR]

In the production of sulfuric acid by the contact method, catalysts with more than 4 % vanadium pentoxide are used, which go out of service once they are completely exhausted. In the present work, the recovery, by acid leaching, of the vanadium contained in exhausted catalysts from the Patricio Lumumba Factory was evaluated. A full factorial design of experiments was carried out (23) where the following were analyzed as independent variables: temperature, solid/liquid ratio and sulfuric acid concentration and as dependent variables: vanadium concentration and leaching performance. The processing allowed obtaining a liquid phase composed of the sulfates of the metals leached with sulfuric acid, which have vanadium concentrations between 1,448 mg/l and 3,730 mg/l. The evaluated processing allows, from the liquid phase obtained, recovering the vanadium for its industrial use, where the solid waste generated is not polluting, which is favorable for the protection of the environment. [ABSTRACT FROM AUTHOR]

In Cuba important chromium mineral reserves exist. Within the Cuban chromites deposits Merceditas for its levels and exploitation stands out. In this work the mineralogical characterization of chromite concentrated belonging to the deposit previously mentioned is presented and its possible use as carrying silicon and chromium source in diffusive process is valued. The determination of the chemical composition of the concentrate was carried out by means of the gravimetric and volumetric methods, whereas for the identification of its phases techniques of Infrared and Mössbauer Spectroscopies, and X-Rays diffraction were used. Additionally the statistical parameters of the grain sized distribution from a sifted process were determined. It is established from its chemical composition, that the concentrate is refractory and that the chromium, iron, aluminum, magnesium, silicon and calcium appear in different proportions. The chromium and silicon content in the concentrate and its relation are similar to the previous reports for the application from diffusive processes of simultaneous saturation with both elements, whereas the levels of aluminum and magnesium combined with oxygen guarantee the refractivity of mixtures. Also, it was corroborated that the mineralogical phases were chromopicotite, antigorite and chlorite and it was concluded that its main phase is the chromopicotite. Finally, it was established that it has an average diameter of 513 µm, obliquity of a 0.93 and a dispersion of 1.83. [ABSTRACT FROM AUTHOR]

The use of slag of iron production is presented in cupola furnace ovens in sugar industry companies for the obtaining of a matrix of a flux for recovery of pieces by submerged arch in this sector. From the analysis of the characteristics of the slag generated in the mentioned foundries their processing outline is conceived for the adaptation to the characteristics of the matrix of a flux agglomerate for the recovery of pieces that responds to a wide demand range, contributing to an increase in the durability of machine elements and to the decrease of the slag like residual solids. [ABSTRACT FROM AUTHOR]

A characterization of coating obtained from the cuban chromite and boric acid as sources of the saturating elements using optical microscopy, x-ray diffractometry and scanning electronic microscopy was carried out. The layers present phases of complex chromium carbides of the type (Cr, Fe) 23 C6, (Cr, Fe)7 C3. The contents of chromium and iron in the layers vary with the saturated mixtures composition. [ABSTRACT FROM AUTHOR]

In this work the simultaneous method of solid saturation is applied to obtain chromium carbide layers alloyed with boron on steel using chromite ore and boric acid as sources of the diffusion elements. The saturates mixtures was obtain from aluminothermy previous way to the process of saturation. By means of a experiment design the influence of the variables studies relation chromium/boron in the saturate mixtures and type of tool steel on the thickness and the micro-hardnesses of the diffusive layers. The obtained coatings are characterized by maximum levels of micro-hardness between 1800 and 1900 Hv20 and thicknesses of agreed layer with the regime of saturation and the used substratum. [ABSTRACT FROM AUTHOR]

In this paper a quantitative physical characterization of the chromite concentrated with refractory characteristic belonging to the deposit Merceditas is presented, using for it technicals of infrared and Mössbauer spectroscopies, X-ray difractometry, chemical and grain size analysis. It settles down that the concentrate is constituted by the phases mineralogical well-known as chromopicotite, antigorite and chlorite, being determined its respective cristalo-chemical formula. By means of the techniques of thermal analysis (DTA, TG and DTG) the thermal behavior of a mixture of chromite concentrated and aluminum is studied with the purpose to valuing the possibilities of the products of the reduction like component of saturating mixtures for the thermodifusives surfaces of chromium and silicon in steels. [ABSTRACT FROM AUTHOR]

The internal combustion motors are the main energy and source of the harvesting and transportation that intervene in the crop of sugar cane. This work exposes the evaluation of the properties obtained in the layers of the recovered-by means of recharges with the process SAW-stumps of crankshafts of different motors of internal combustion, with the use of an alloyed agglomerate flue developed in the Welding Research Center (CIS) of the Central University "Marta Abreu" de Las Villas. This flue is dedicated to recharging the surfaces that work subjected to the friction waste, basically crankshafts and other axis-like parts. A forecast is also done of the working capacity of different alternatives by means of wear tests. The results are valid for a great range of crankshafts built of different materials, of motors already well known or new ones recently introduced in the country. [ABSTRACT FROM AUTHOR]