Hasil untuk "Mining engineering. Metallurgy"

Biao KONG, Jianhui ZHONG, Wei LU et al.

The method of sensing coal spontaneous combustion temperature based on acoustic wave technology has the advantages of wide application scenarios and real-time continuity, but the precursor characteristics of acoustic wave signals in the process of coal spontaneous combustion have not yet been revealed. The study of acoustic effects and precursor characteristics in the process of coal spontaneous combustion provides a theoretical basis for the detection and warning of coal spontaneous combustion by acoustic wave method. The article firstly theoretically analyses the thermal damage rupture evolution process and acoustic wave transmission characteristics of coal rock. Three sizes of coal spontaneous combustion acoustic wave information testing systems were established to test the infrasound, acoustic emission and acoustic sound velocity information during coal heating and combustion. Using linear fitting, multiple fractal theory, Fourier transform and other methods, the paper analyse the temporal characteristics, temperature correlation, spatial characteristics, nonlinear characteristics and spectra of acoustic signals to reveal the precursor characteristics of acoustic signals in the process of spontaneous combustion of coal. The results show that with the increase of coal temperature, the infrasound sound pressure value increases paroxysmally, and the ringing counts, energy value and acoustic sound velocity of acoustic emission signals are positively correlated with the temperature. The infrasound signals and acoustic time changes were more obvious in the pre-coal spontaneous combustion period. The acoustic emission signal increases and changes more significantly after 100 ℃. The acoustic signal has spatial characteristics. With the increase of the distance from the heat source, the ringing count and energy change by decreasing. The speed of sound at different distances increases with increasing temperature, and the R2 of the speed-temperature fitting equation exceeds 0.9. The infrasound and acoustic emission signals have multiple fractal characteristics during coal heating and correspond well with the thermal rupture of spontaneous coal combustion. In addition, the main frequency of infrasound waves migrated and the amplitude of the main frequency increased during the process of coal warming. Finally, the acoustic emission test was carried out in the high-temperature anomaly area of the coal field. The acoustic emission signals in the temperature anomalies change significantly.

Yang Liu, Fu Wang, Jing Wang et al.

Misaligned grains present significant challenges in the directional solidification of complex-shaped industrial gas turbine (IGTs) blades made from Ni-based superalloys using the Bridgman method. These defects are closely associated with the bending of the solid/liquid (S/L) interface isotherm, a phenomenon heavily influenced by its relative position to the insulation baffle during solidification. The location of this isotherm is determined by the withdrawal rate employed. This study develops a simplified mathematical model that integrates blade and mold geometries, processing parameters affecting heat transfer, and the morphology of the liquidus isotherm. The model aims to design adaptive strategies for varying the withdrawal rate to control misaligned grain formation during directional solidification. By leveraging this theoretical framework, optimal adaptive withdrawal rate strategies were automatically generated, effectively flattening the liquidus isotherm and controlling misaligned grain formation in both dummy and actual IGT blades. This model, tailored to automatically design adaptive withdrawal rate routes, offers a robust strategy for producing misaligned-grain-free IGT blades.

Xudong Kang, Zhaoxin Du, Zhen Wang et al.

In order to reduce the deformation resistance, the rolling process of metastable β titanium alloys is generally carried out in the β single-phase state, which causes the problem of non-uniform grain size during the subsequent annealing process, thus affecting the alloy properties. Here we first solution-treated the as-cast Ti–15Mo–3Al-2.7Nb-0.2Si alloy at 740 °C to obtain α + β phase, then cold rolled it with a reduction of 60 %, and finally annealed it at 710–810 °C for 2–240min. Characterization of the annealed metastable β alloy revealed that α phase was involved in the rolling deformation at the same time and recrystallized on the β matrix during the subsequent annealing process, known as equiaxial dispersion, which impeded the recrystallization of the β grains, and ultimately an ultrafine crystalline microstructure of α + β phases with an average grain size of less than 2 μm was obtained.

Hexin Tian, Fachang Zhao, Dongmei Ma et al.

<b>The</b> Al-Si alloy prepared by the traditional powder metallurgy method has the problems of difficult sintering and low mechanical properties. In this paper, rotary extrusion combined with rapid solidification/powder metallurgy technology (RS/PM) is proposed and designed to produce an Al-10Si alloy. In subsequent sintering at different temperatures, better metallurgical bonding between particles can be achieved to fulfil the aim of improving the mechanical properties of the material. Additionally, the continuous preparation of materials can be achieved. Finally, it is verified that the density of the Al-10Si alloy sintered at 525 °C is 2.61 g/cm³, reaching 97.0% of the theoretical density, and the tensile strength reaches 336 MPa, which is much higher than that of the alloy prepared by the traditional casting method and powder metallurgy method.

Guang-Ling Song, Andrej Atrens

This review summarizes recent insights into the Mg corrosion mechanism, clarifies many critical controversial points regarding the Mg corrosion behaviour, and updates some efforts made to extend the industrial application of Mg alloys. Based on the new understandings gained so far, future research directions are also suggested in the review. This review has the following logic. The first section “1. Scope” is a consolidation of the new understandings or developments regarding the Mg corrosion mechanism and the new applications for Mg alloys. It also highlights some key points for the review. The second section “2. Widely accepted knowledge” briefly summarizes the general understanding of Mg corrosion gained so far, which acts as the foundation for the following sections. The third section “3. Recently deepened insights” mainly briefs on some new insights into Mg corrosion phenomena based on recent findings. Different interpretations on the corrosion behaviours are comprehensively discussed in the fourth section “4. Controversial points” and the conclusions are drawn in the subsection “4.5 Clarified points”. Apart from the fundamental understandings, various efforts in the application of Mg alloys are presented in the fifth section “5. New applications”. Following the research tendency as indicated in the review, prioritized research areas are suggested in “6. Future directions”. The review is concluded with “7. Concluding remarks” at last.

Anton Seleznev, Nestor Washington Solis Pinargote, Anton Smirnov

In the original article [...]

E. Khoroshilov

The article analyzes the current state of Russian-Canadian economic relations, examines trends in bilateral trade and accumulated direct investments. It is shown that Russian exports to Canada are now back to the levels seen before 2014, while Canadian exports to Russia have not been able to recover from the consequences of a sharp deterioration in bilateral relations. It is concluded that Canada supplies Russia mainly with products with high added value, while Russian exports to the Canadian market are dominated by raw materials and low-value products. It is indicated that the scale of Russian-Canadian investment cooperation has significantly decreased after 2014. However, there is noticeable Russian presence in the Canadian metallurgical industry and agricultural machinery engineering, while Canadian companies have strong positions in Russian mining sector and vehicle engineering. It is noted that Russian-Canadian economic relations remain hostage to the hostile policy of the ruling circles of Canada towards Russia.

Gubanov Roman S.

Introduction. The structure of coal mining in Russian deposits is heterogeneous due to significant imbalances dictated by different geological and engineering conditions of mining in different regions of the country. Due to the consequences of the COVID-19 pandemic and the crisis associated with it, the dynamics of coal production is not stable, and in recent years there has been a decline in economic growth in companies in the coal sector of the Russian economy. Today it is important to focus on the development of new deposits, the search for safer and more reliable ways of mining. This will make it possible to optimize coal mining management mechanisms and provide solutions to the problems of increasing economic efficiency in the coal sector of the Russian Federation. Research objective is to scientifically substantiate the reasons and conditions for the formation of long-term demand for resource potential for the extraction of energy and coking coal using situational analysis. Methods of research. In order to study the problems of the coal sector development, a scenario analysis of the dynamics and structure of coal mining in Russian deposits was carried out. As a result, hypotheses about the need for complex extraction of energy and coking coal grades were confirmed. It has been scientifically proven that the introduction of open-underground geotechnology in Russian deposits serves as a way to rationalize mining operations, and increases the final effect of coal mining. Results. The characteristics of the main types of coal reserves in Russian deposits are presented. Of practical importance is the study of the dynamics of A-Property coal production in 2020–2021 in various companies. Conclusions. As a result of the conducted research, the article draws an important conclusion about the need to expand the practice of obtaining and using anthracite, despite its high level of rarity of extraction. The organization of new methods of anthracite extraction and use in the industry will improve the production of metallurgical raw materials.

Lin Li, T. Jiang, Bojian Chen et al.

Jie Ning, Suck-Joo Na, Chen-hong Wang et al.

High-nitrogen austenitic stainless steel (HNASS) has many excellent properties, such as high strength and toughness, high strain-hardening ability, strong corrosion resistance and low magnetization compared with the traditional widely used Ni–Cr austenitic stainless steel. The high nitrogen content in HNASS leads to the welded joint in the risk of many problems, such as nitrogen escape and loss, nitride precipitation, formation of pores and thermal cracks, resulting in the poor welding performance. The HNASS joints without obvious defects were obtained by metal inert gas (MIG) welding and laser-MIG hybrid welding, separately. The microstructures and properties of welded joints were compared. The nitrogen content in fusion zones of the two joints was tested by an oxygen, nitrogen and hydrogen analyzer. The tensile strength and the impact absorption energy of laser-MIG hybrid welded joint were about 27% and 20% higher than those of MIG welded joint, respectively. It could be attributed to the stronger solid solution strengthening effect resulted by the high nitrogen content of laser-MIG hybrid welded joint. The finer grains and the reduction of ferrite and precipitation phase in the microstructure of laser-MIG hybrid welded joint contributed to the improvement of toughness.

Paweł Sikora, Marek Wesołowski

This paper presents the results of numerical simulations carried out to confirm the influence of former mining activities on deformation of the mining terrain. The assessment of deformation changes was carried out with the use of FLAC3D program based on the finite difference method. Numerical calculations were carried out for the example of actual mining operations in seams 703/1-2 and 707/2 of “Marcel” Coal Mine. Taking into account the influence of the model’s plastic features and the so-called activation of a higher occurring seam in conducted simulations enabled obtaining a very good description of the measured subsidence. Based on the results one may state that numerical model can be used to assess the influence of former mining activities and the direction of conducted exploitation on deformations of the mining terrain. These factors are not recognized by geometric-integral theories commonly used for predicting the influence of mining operations on the surface. The results presented in this paper confirm that the applied method of simulating the phenomenon of reactivation of post-mining goafs is correct.

article editorial

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Mehreen Iqbal, Zain-ul-Abdin, T. Naseem et al.

S. Zairov, Sh. R. Urinov, R. U. Nomdorov

Involvement of deep deposits in mining predetermined the trend of development of open pit mining towards increasing the depth of open pits. The main limitation imposed on drilling and blasting in the near-contour zone of an open pit is the need to protect the pit walls and engineering structures on the walls from seismic effects of huge blasts. As practice shows, the most effective and proven method of protecting pit walls is the use of blasting by presplitting method, creation of a shielding gap and a shielding layer of blasted rock mass, i.e. pre-splitting of the pit walls, preceding the huge blast. Therefore, the study of stress-strain state of the near-contour rock mass, determination of the parameters of blastholes for edge pre-splitting (preliminary shielding gap formation) in open pits is an urgent task. The analysis of the pit wall design and stress-strain state of rock mass at Kokpatas deposit exploited by Navoi Mining and Metallurgical Combine allowed to determine the model, as well as the method for calculating stress-strain state of the rock mass. When assessing stability of the pit walls, an approach known as the displacement method was used. Applying the boundary integral equations method allowed to develop an algorithm for calculating stresses in the rock mass for the conditions of Kokpatas deposit. A technique has been developed for experimental studies of blasting contour blasthole charges (blasting by pre-splitting method) using models, allowing to study fracturing on volumetric models and wave interaction by the method of high-speed video recording of the blasting process in transparent models, as well as to determine the parameters of stress waves during blasting in samples of real rocks. A method for formation of stable pit wall slopes, an excavator method for bench pre-splitting on ultimate envelope (contour) of a pit, and a method for initiating blasthole charges in the near contour zone of a pit have been developed and implemented in the industry.

Y. Ghorbani, G. Nwaila, Munyar Chirisa

ABSTRACT Metal accounting is becoming an area of growing focus because of the requirement for the resulting data to feed directly into financial reports. It is vital in the fulfillment of best corporate governance practices and to provide assurance on metallurgical processes. The current metal accounting practices deliver a number of important measures, but an essential change in the approach toward data integrated and auditable metal accounting system is an indispensable need. This work aims to present a systematic framework toward a highly reliable method in metal accounting. The proposed approach introduces a novel mining to product metal accounting scheme and conceptualization of an intelligent metallurgical and metal accounting information management system (MMAIMS). An open cast gold mine in South Africa is presented as a case study. Based on the results and discussions that we have presented in this study, it has been shown that the proposed intelligent MMAIMS will result in improved plant process control, transparent financial reporting, and a suitable understanding of interrelationships between different process activities. The intelligent MMAIMS approach will eradicate data security risks related to multiple-user environment spreadsheets, create reliability in data used for decision-making and operation data synchronization. End to end metal accounting process visibility across the whole process will advance the audibility and transparency of metal accounting from mine to product, and enable good corporate governance and financial reporting of the salable metal product concerning smart mining and mineral processing concept.

Vladislav I. Galkin, Artur Nikolaevich Koltyrin

To solve the problems accompanying the development of forecasting methods, a probabilistic method of data analysis is proposed. Using a carbonate object as an example, the application of a probabilistic technique for predicting the effectiveness of proppant hydraulic fracturing (HF) technology is considered. Forecast of the increase in the oil production of wells was made using probabilistic analysis of geological and technological data in different periods of HF implementation. With the help of this method, the dimensional indicators were transferred into a single probabilistic space, which allowed performing a comparison and construct individual probabilistic models. An assessment of the influence degree for each indicator on the HF efficiency was carried out. Probabilistic analysis of indicators in different periods of HF implementation allowed identifying universal statistically significant dependencies. These dependencies do not change their parameters and can be used for forecasting in different periods of time. Criteria for the application of HF technology on a carbonate object have been determined. Using individual probabilistic models, integrated indicators were calculated, on the basis of which regression equations were constructed. Equations were used to predict the HF efficiency on forecast samples of wells. For each of the samples, correlation coefficients were calculated. Forecast results correlate well with the actual increase (values ​​of the correlation coefficient r = 0.58-0.67 for the examined samples). Probabilistic method, unlike others, is simple and transparent. With its use and with careful selection of wells for the application of HF technology, the probability of obtaining high efficiency increases significantly.

Dina Ewis, Ahmed Gomaa Gomaa Talkhan, Abdelbaki Benamor et al.

The effect of temperature, time and rotation speed of FT-GTL process water on the corrosion rate of API X-120 carbon steel was investigated. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used to determine the carbon steel corrosion rate under temperatures ranging from 293 to 323 K and rotation speed of 0, 500, 1000, 2000 rpm when the immersion time was 0.5, 1, and 2 h. The corrosion rate increased with temperature and rotation speed but decreased with immersion time. SEM, XRD, and XPS analyses of the corroded surfaces confirmed the formation of iron oxide and ferric oxide as the main components of the protective layer.

M. Sears, G. Esterhuizen, I. B. Tulu

S. McCue, G. Hocking, M. Dallaston et al.