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The precipitation of Ni and Co mixes sulphides is one of the stages of the ammoniacal technological process in the cuban nickel industry, but the oxidation of sulphides disturbs its storage and transportation. This paper exposes results from chemical characterization by X-ray diffraction and mineragraphic analysis of mixed sulphides as well as from the kinetic investigation of the thermal oxidation of samples in isothermal and no isothermal regime. It's determined de most probable model and kinetic parameters of the physical-chemical transformations that occurs in oxidation process. It's concluded that oxidation of mixed sulphide concentrate follows 4 stages: lost of water and ammonio, degradation of superior sulphides, formation of sulphates and degradation of sulphates into oxides. Degradation of sulphides into oxides degradation of sulphides to oxides Nickel and cobalt sulphides obtained through leaching technology carbonates ammoniacal of laterític ferrous nickelitic ore is characterized and is studied in the kinetics of oxidation concentrated in nickel and cobalt sulphides applying the isothermic and not isothermic methods, being determined the most probable pattern and the kinetic parameters of the physical chemical transformations that take place in the process of oxidation. [ABSTRACT FROM AUTHOR]

This work presents a metallographic characterization of austenitic stainless steel AISI 321, which is the material of construction used in the pipe of the lateritic mineral screw conveyors operating in the nickel industries using Caron technology. A fractography was carried out by using macro and micro-analysis techniques; which allowed analyzing the fractures caused by spreading of cracks due to prolonged exposure to high temperatures (650-700 °C) in addition to manufacturing defects. Samples of steel used in the process were taken to determine the chemical composition and an optical microscopy was conducted to identify the intrinsic characteristics and the morphology of the cracks causing the rupture. Destructive testing trials were completed at the conveyor's operating temperatures. A microhardness testing for metal matrix and carbide hard compounds indicated high values for the latter elements, which act as stress concentrators when forming conglomerates. [ABSTRACT FROM AUTHOR]