铸态Ti–44Al–4Nb–(Mo, Cr, B)合金的热变形行为及热加工图

利用Gleeble热模拟机研究了铸态Ti-44Al-4Nb-(Mo,Cr,B)合金在1 050～1 200℃、0.005～0.5s-1下的热变形行为,并基于所得的真应力-真应变曲线绘制了热加工图。另外,通过透射电子显微镜(TEM)研究了片层和γ相的变形机制。结果表明,该合金是典型的应变速率和温度敏感材料,它的热加工性能较好,在1 100、1 150℃温度下的低应变速率区域以及1 200℃温度下高应变速率区域比较适合热加工。再结晶是流变软化的主要原因,较高的变形温度和较低应变速率有利于再结晶晶粒的进行。片层结构的变形机制为片层扭折,而γ相的主要变形机制为位错滑移和变形孪晶。     

Selection of load–haul–dump machines for hard mineral mining in difficult mining and geological conditions

In focus is selection of load–haul–dump machines for hard mineral mines. The authors offer substantiation procedures for tuck-and-shovel systems of mining in difficult ground conditions. In terms of Kyrgaisky Sredni open-cut located in the Erunakovo coal district in Kuzbass, using the Lerchs–Grossman algorithm, the principles and sequence of forming efficient application domains for different specification trucks and shovels within a mine field are presented.     

Solid–liquid separation equipment selection and modelling

The ease with which data may be entered into, and extracted from, electronic databases using Internet based applications is providing new opportunities for understanding and modelling of complex systems. An expert system for solid–liquid separation equipment selection and elimination, using an Internet based interface coupled to such a database, is described. Also, a database containing filtration constants for a variety of different minerals is provided and an illustration of how these constants may be used in mathematical simulations of filtration processes is given. A simple experimental procedure, which can be performed using only a single test where the pressure during filtration is incrementally increased, can provide the necessary filtration constants for the simulation procedure. Hence, the database of filtration constants can be easily expanded using experimental data from this, or similar procedures. An experimental technique that measured the in situ concentration of the forming filter cake, via electrical conductivity measurements, was used to compare the simulated local cake concentrations, using the filtration constants, against the measured ones. The agreement between the simulated cake concentrations and the measured ones was excellent.     

Hydrothermal precipitation of arsenic compounds in the ferric–arsenic (III)–sulfate system: thermodynamic modeling

It is known that Fe (III) and As (III), through in situ oxidation, can precipitate to form a crystalline ferric arsenate under specific conditions of temperature and pH. A thermodynamic model is built to investigate this process. The development and the use of chemical speciation model have lead to simulate the distribution and the concentration of chemical species of the ferric–arsenate (III)–sulfate system at 293.15–553.15 K temperatures range. The modeling predictions are compared to experimental data measured by the authors. It was shown that a reasonable prediction could be made if different modeling approaches are used. The paper compares different approaches in thermodynamic modeling and discusses also the validity of different extrapolation models used at high temperatures.     

BX1–315弧焊机的设计

通过对焊弧稳定燃烧的分析,说明交流焊机必须有陡降的外特性,即焊机的漏抗必须较大且可调。BX1-315焊机调整漏电抗的方法是在初、次级绕组间增加一个动铁芯分磁回路,以改变焊机的漏抗,进而改变焊接电流。简要地论述了BX1-315焊机的设计方法。     

Collectability of physically adsorbed xanthate ion–dixanthogen associates

Under discussion is collectability of ethyl and butyl xanthate species resulted from nonstoichiometric interaction with oxidizer. It is visually proved that solution contains fine micro-drops stabilized by negative charge. The size and ζ–potential of micro–drops are determined together with the spreading velocity of emulsion over water surface. The mentioned velocity is higher than the spreading velocity of products of non-stoichiometric interaction between xanthate and heavy metal salt. The products of interaction between xanthates and oxidizers are known as desorbable species (DS), as at the moment of rupture of water film between mineral particle and air bubble they can detach from particle surface and attach to air–water interface. Spreading of DS over the interface forces water out of the film. The forces applied to liquid in the film from the side of DS of ethyl and butyl xanthates are evaluated. The volume–flow rate of water from the film is related with the surface pressure of reagent species active at the air–water interface. The surface pressure of dixanthogen–xanthate emulsion is evaluated as a function on initial concentration of xanthate. Collectability of the reagent depends on the surface tension of DS solution and is governed by the structure of hydrocarbon fragment of the agent.     

Study of silver leaching with the thiosulfate–nitrite–copper alternative system: Effect of thiosulfate concentration and leaching temperature

Thiosulfate system is considered an interesting alternative leaching process for precious metals. Nevertheless, most of the literature published on these conventional thiosulfate leaching solutions has been focused on the use of ammonia and copper to generate the cupric tetraamine complex, which acts as a catalytic oxidant for silver. However, ammonia toxicity is also a detrimental issue in terms of the process sustainability. For that reason, thiosulfate–nitrite–copper solutions were studied as an alternative less toxic system for silver leaching.In this work, the effect of the thiosulfate concentration (0.07 M, 0.1 M and 0.15 M) and temperature (room temperature, 30, 35, 40 and 45 °C) on the metallic silver leaching kinetics is presented for the S₂O₃–NO₂–Cu system. The results show that the thiosulfate concentration plays an important role in the S₂O₃–NO₂–Cu–Ag system since it controls the silver leaching kinetics. On the other hand, an increase in temperature favors the silver recovery.Finally, the SEM–EDS analysis, the X-ray mapping and the X-ray diffractograms show that the solid silver particles are coated by a Cu, S and O layer for the 0.07 M and 0.1 M thiosulfate experiments, which is consistent with the formation of antlerite (Cu₃(SO₄)(OH)₄); while the 0.15 M thiosulfate scenario produced a layer composed only of Cu and S, revealing the formation of stromeyerite (CuAgS). The UV–Visible technique confirmed the in-situ generation of copper–ammonia complexes for the 0.07 M leaching condition; however, these complexes are not formed at the 0.15 M condition.     

Quantitative estimate of rotary–percussion drilling efficiency in rocks

The factors that have significant influence on efficiency of rotary–percussion rock drilling with downhole machines are discussed. The results obtained in physical simulation of dynamic driving of rock-breaking indenters in rocks are reported. The results are analyzed from the standpoint of the phenomenon of alternating response of rocks to dynamic impacts.     

Digestion kinetics of arsenic removal from enargite–tennantite concentrates

Copper sulfide concentrates with high contents of deleterious impurities such as arsenic and antimony must be pretreated before conventional smelting to prevent atmospheric pollution with toxic compounds. In this work, the selective removal of arsenic and antimony from enargite–tennantite concentrates by a hydrometallurgical process was studied. The process consists of an alkaline digestion using a small volume of concentrated NaHS–NaOH solutions to obtain soluble arsenic and antimony compounds and insoluble copper sulfides. The soluble arsenic and antimony is separated from the copper sulfide by water leaching of the digested material. The experiments were carried out using a copper–arsenic concentrate with 15.1% As and 1.42% Sb. The results showed that the digestion temperature and the concentrations of NaHS and NaOH were the most important variables affecting the rate of arsenic and antimony removal. The rate of the digestion reaction was analyzed by using the unreacted shrinking core model controlled by the diffusion of S²⁻ ions through the layer of the product copper sulfide. An experimental activation energy value of 57 kJ/mol was determined for the arsenic removal in the range of temperature of 60–90 °C.     

Seismic–Geomechanical Control of Water-Impervious Strata in Potassium Mines

The safety control system for water-soluble mineral mining in complicated ground conditions is presented. The system is based on geomechanical interpretation of surface and underground seismic monitoring data. Mathematical modeling of water-impervious strata takes into account the whole set of geological and geotechnical factors determined from the seismic observations. It is shown that the seismic–geomechanical monitoring allows stress state control in waterproof strata, which ensures prompt decisionmaking on extra protection and minimizes accident risks.     

Analysis of Two-Phase Gas–Water Flow in Carbonate Reservoirs

Gas–water relative permeability (GWRP) is measured in the tests of full-diameter cores. Based on the obtained GWRP curves, the standard normalized curves are plotted for three types of carbonate reservoirs: matrix pore, fracture and solution pore. The corresponding gas and water two-phase flow model was deduced by considering stress sensitivity and non-Darcy effect, and the IPR curve calculation and analysis of gas wells of the three types were carried out. Based on huge gap between the matrix and fracture permeability, the phenomenon of gas drive water mainly exists in the cracks. So the conventional gas–water relative permeability of fractured gas reservoirs was modified.