Research of Magnetizing Roasting of Iron Ore Before Beneficiation and Dephosphorizing

There are quite a lot of iron ore deposits in the world with increased (0.75%) phosphorus content, which is an obstacle to their involving in production. Research of removal of detrimental impurities from such iron ores has a great prospect. On the experimental base of OJSC VNIIMT, it was studied dephosphorizing technology at which after preliminary magnetizing roasting and subsequent dephosphorization of iron ore with aqueous solution of sulfuric acid the least residual phosphorus content in concentrate was observed. Research of influence of temperature and duration of magnetizing roasting on iron content and residual phosphorus content in dephosphorized concentrate was studied. The influence of specific consumption of solid reductant (brown coal) on the quality of magnetite concentrate was also studied. Based on the results of the experiment, the optimal technological parameters of magnetizing roasting of iron ore before beneficiation and subsequentdephosphorization were selected. Keywords: magnetizing roasting, beneficiation, dephosphorizing, research, rotary furnace, optimal process parameters, iron content, residual phosphorus conten

Synchrotron Sub-μ X-ray Tomography of Kirkendall Porosity in a Diffusion Couple of Nickel-Base Superalloy and Nickel after Annealing at 1250 \ub0C

Kirkendall porosity that forms during interdiffusion in a diffusion couple of nickel-base superalloy CMSX-10 with pure nickel is investigated. The diffusion experiments are conducted at a temperature of 1250 \ub0C, where the strengthening γ′-phase is partially dissolved. The porosity is studied by X-ray sub-μ tomography with a spatial resolution of about 0.353 μm3 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. It is found that depending on the distance from the interface the Kirkendall pores take different shapes: octahedral, rounded pyramidal, drop shaped, dendritic, pear shaped, and joint shapes. Such a variety of pore morphologies indicates a complex multistage process of porosity nucleation and growth under vacancy supersaturation of different degrees. The experimental findings are interpreted on the basis of the results of diffusion modeling. It is shown that the kinetics of porosity growth is essentially influenced by the dissolution of the γ′-phase

Iron Ore Dephosphorization of Gara Djebilet Deposit By Hydrometallurgical Method

For industrial use, iron-ore concentrates shall correspond to definite requirements regarding both basic substance content – iron as well as phosphorus content. Decreased phosphorus content in iron-ore concentrate can be received by the method of hydrometallurgy (desalinization of phosphorus by mineral acid). On theexperimental base of OJSC VNIIMT, a laboratory research was carried out regarding iron ore dephosphorization; as a result maximum possible content of phosphorus was obtained in a final product. The optimal technological parameters of sulphuric acid desalinization were defined that have an effect on quality of phosphorus removal of iron ore magnetite concentrate: size degradation of roasted concentrate; phosphorus removal duration; pulp heating temperature effect; sulphuric acid-specific consumption. Keywords: desalinization, iron ore, concentrate, pulp, sulphuric acid, phosphorus content, optimal parameter

Creep behavior of a γ′-strengthened Co-base alloy with zero γ/γ′-lattice misfit at 800 °C, 196 MPa

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Deformation and structural behavior of an experimental γ′-strengthened Co-base alloy during creep at 800 °C and 196 MPa have been investigated. The characteristic features of this alloy are zero γ/γ′-lattice misfit and a fine γ/γ′-microstructure. In the initial condition, the γ′-precipitates in this alloy are small (size of about 100 nm), have polyhedral morphology, and are separated by the very narrow γ-channels (width of about 10 nm). The tests performed up to about 1% creep strain (about 500 h creep time) gave creep curves with a slow constant strain rate and without an apparent transient creep, typical for superalloys with nonzero misfit. In this initial stage of creep, entering of the narrow γ-channels by dislocations is blocked by a strong Orowan force. The micromechanism of creep was identified as an octahedral glide of 〈011〉 superdislocations simultaneously in two phases, γ and γ′. The γ/γ′-microstructure with zero misfit shows no rafting but rapidly coarsens isotropically. It is concluded that zero misfit is beneficial at the initial stages of the creep but is unfavourable for long-term creep because of the continuous microstructural coarsening

Results of the Application of the Original Method of Surgical Treatment of Patients with Severe Hallux Valgus

Background. Traditional methods of surgical treatment of severe Hallux valgus (HV) lead to a large number of complications and poor results. In order to avoid complications and improve the quality of treatment, an original technique of double osteotomy of the first metatarsal bone has been proposed.The aim of the study was to conduct a comparative assessment of the results of applying the original technique in the treatment of patients with severe Hallux valgus.Materials and methods. A retrospective analysis of the treatment of 95 patients operated on at the Seversk Clinical Hospital for severe Hallux valgus in the period from 2008 to 2016 was performed. The study group included 60 patients who underwent surgery according to the original method. In a comparison group of 35 people, Logroshino's surgery was performed. Clinical, radiological, surgical and statistical research methods were used.Results. The final assessment of the results 1 year after the operation showed an unacceptably high number of Hallux valgus relapses, complications, and unsatisfactory results in the comparison group. The use of original approachesfor osteotomy of the first metatarsal bone in patients of the study group allowed to significantly improve treatment results and achieve good results in 85 % of cases.Conclusion. The proposed surgical technique is effective and shows statistically significantly better results 1 year after surgery. Application of the original technique will improve the results of surgical correction of the severe degree of Hallux valgus, which consists in reducing the number of complications and improving functional indicators

Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature

The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288°C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no gamma' strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g., the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional area Psi of [001] crystals reached nearly 100 pct, while for a [111] crystal Psi=62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from (011){111} octahedral slip

A Vacancy Model of Pore Annihilation During Hot Isostatic Pressing of Single Crystals of Nickel-Base Superalloys

An improved diffusion model of pore annihilation during hot isostatic pressing of single crystals of nickel-base superalloys is proposed. The model considers dissolution of pores by emission of vacancies and their diffusion sink to low-angle boundaries. The calculation, which takes into account pore size distribution,predicts the kinetics of pore annihilation similar to experimental one

Mental Health and the COVID-19 Pandemic: Hardiness and Meaningfulness Reduce Negative Effects on Psychological Well-Being

Background. The COVID-19 outbreak and the measures taken to curb it have changed people’s lives and affected their psychological well-being. Many studies have shown that hardiness has reduced the adverse effects of stressors, but this has not been researched in the Russian COVID-19 situation yet. Objective. To assess the role of hardiness and meaningfulness as resources to cope with stress and minimize its effects on psychological wellbeing. Design. The study was conducted March 24-May 15, 2020 on a sample of 949 people (76.7% women), aged 18-66 years (M = 30.55, Me = 27, SD = 11.03). The data was divided into four time-periods, cut off by the dates of significant decisions by the Russian authorities concerning the COVID-19 pandemic. The questionnaires were: Beck Anxiety and Depression Inventories, Symptom Check-list-90-R, Noetic Orientations Test, and Personal Views Survey-III. Results. Welch’s ANOVA showed significant differences between the time-periods in meaningfulness, hardiness, anxiety, depression, and the General Symptomatic Index (GSI) (W = 4.899, p < 0.01; W = 3.173, p < 0.05; W = 8.096, p < 0.01; W = 3.244, p < 0.022; and W = 4.899, p < 0.01, respectively). General linear models for anxiety, depression, and GSI showed that biological sex, chronic diseases, self-assessed fears, and hardiness contributed to all of them. In all three models, hardiness had the most significant impact. Anxiety was also influenced by the time factor, both in itself and in its interaction with hardiness levels. With less hardiness, more anxiety occurred over time. Conclusion. Hardiness was shown to be a personal adaptive resource in stressful situations related to the COVID-19 pandemic. © 2020. Lomonosov Moscow State University. All Rights Reserved