Metallographic studies of structural-phase states formed in the section of the flange of the wheel band during surface plasma hardening were conducted. It is shown that the formation of several structural zones of different micro hardness is distinctly observed in the depth of hardening, which indicates the formation of a graded-layered structure. It has been confirmed that at superfast heating rates that occur during surface plasma quenching, phase and structural transformations are shifted to high temperatures, greatly changing the kinetics of nucleation and growth of the new phase (austenite). This forms a fine-grained austenite, which turns into a highly disperse martensitic structure, unattainable by traditional methods of heat treatment. It is shown that the main factor leading to strong hardening of the surface layer during plasma treatment is the formation in the near-surface zone of a nonequilibrium metastable structure, which goes over to a narrow zone of complete and incomplete quenching with an inhomogeneous and distorted structure of highly disperse martensite with a high level of internal stresses. The complete wear of the unstressed flange of the tire wheel band is 1.9 mm in 1.1 years, and for hardened flanges, wear is 0.7 mm for 2.6 years.
In relation to solid-rolled wagon wheels the advantages of differentiated quenching of all wheel elements are shown in comparison with quenching of only wheel rim rolling surface. It should be noted that larger possibilities to enhance performance characteristics of heavy duty details and products can be fulfilled using the technology of overall hardening including the differentiated quenching and surface plasma processing. It is established that along with the improvement of mechanical properties plasma processing after volume quenching allows for a considerable increase of crack resistance of surveyed grades in comparison with volume quenching without plasma processing. The martensite structure of the strengthened layer during such overall processing in comparison with the martensite structure of volume and strengthened base is characterized by high level of particle size that is specified by reduction of the original austenite grain due to very high heating and cooling speeds as well as small time of steel stay at high temperatures. In order to increase hardness and resistance against cracks generation plasma processing and preliminary volume quenching are recommended. A composite working layer with high wear and crack growth resistance and relatively soft and plastic core are developed in details and products volume quenched when surface plasma strengthening.
The effect of different oxidants on extraction of uranium from low grade ore was studied. Leaching was performed using sulfuric acid solutions at a concentration of 10 to 30%. Ferric sulfate Fe2(SO4)3, ammonium persulphate (NH4)2S2O8, and potassium permanganate KMnO4 at different concentrations were used as oxidants in different variants of the experiment. In addition, solutions collected at Vostok deposit containing 6.86 g/L Fe3+ and 106 cells/mL of the bacteria Acidithiobacillusferrooxidans were used for leaching. The rate of uranium extraction with sulfuric acid solutions without oxidants was low and did not exceed 19.4%. Addition of oxidants made it possible to increase rate of uranium extraction. In the presence of ferric sulfate, ammonium persulphate, and potassium permanganate rates of uranium extraction were up to 68, 95.2, and 69.6%, respectively. The rate of uranium leaching in the experiments with the AMD sample was high and reached about 95%. Therefore, it can be concluded that using not only oxidizing agents, but AMD, which are formed during the natural oxidation of sulfide minerals contained in the ore of the deposit, can significantly increase the rate of uranium recovery.
BACTERIAL AND CHEMICAL LEACHING OF GOLD-BEARING ORE FROM THE SHOKPAR DEPOSIT BY ACIDITHIOBACILLUS FERROOXIDANS CULTUREAnnotation. The periodic mode of bacterial-chemical leaching of gold-bearing ore from the Shokpar Deposit using the A. ferrooxidans culture was studied under laboratory conditions. Have been performed previous steps prior to the leaching process, such as culturing of Acid.ferrooxidans microorganisms, granulometric analysis of ore composition from the Shokpar Deposit. During 13 days of the oxidation process and when setting the optimal temperature and humidity, it was possible to achieve the actual value according to the test results -0.116 mg/l gold.
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