The electronic structure and spin state of pristine rhodochrosite and rhodochrosites with Mn atoms substituted by Ca, Mg or Fe atoms were calculated by density functional theory (DFT), and the magnetism of rhodochrosites was investigated by calculating their spin magnetic moment. The results show that substituting Mn atoms in rhodochrosite for Ca, Mg or Fe atoms can weaken the magnetism of rhodochrosite, and, among the four types of atoms, Mn atoms exhibit the highest saturation magnetization, followed by Fe atoms. The magnetic field and spin magnetic moment generated by the relative motion of ion core to electron of Mn²⁺ are larger than those of Ca²⁺, Mg²⁺ and Fe²⁺.

For recovering the cobalt in a sulfur-cobalt concentrate mainly occurring as isomorphism in pyrite and magnetite, an experimental study was carried out by adopting roasting and leaching process. The results show that the sulfur-cobalt concentrate, at the fineness of -0.074 mm 80%, was firstly roasted at 620 ℃ for 3 h by adding sodium sulfite as an aid at an amount of 5% of the mass weight of sulfur-cobalt concentrate, and then leached for 2 h at 90 ℃ with sulfuric acid at an amount of 20% of the mass weight of sulfur-cobalt concentrate, liquid-solid ratio of 2∶1, leading to a cobalt leaching rate of 85.85%. It is found that sulfur-cobalt concentrate is transformed into hematite after oxidizing roasting, and cobalt in the roasted ore mainly exists in the form of cobalt oxide and cobalt sulfate.

The process mineralogy and separation feasibility of an ilmenite ore from Xinjiang were comprehensively studied to recover iron and titanium resources from the gravity separation concentrate. The process mineralogy results show that the valuable minerals therein include ilmenite, manganese-bearing ilmenite, titanium-bearing magnetite and magnetite, while the gangue minerals therein are predominantly tremolite, riebeckite, garnet and sphene. After one stage of grinding, iron minerals were collected with one stage of low intensity magnetic separation. Then, two stages of high intensity magnetic separation were adopted to recover titanium minerals. The titanium rough concentrate was treated by a flotation for desulfurization and a flotation process consisting of one stage of roughing, one stage of scavenging and four stages of cleaning. The whole process produced an iron concentrate grading 63.93% TFe at 69.11% recovery, presenting a good separation index, and a titanium concentrate was obtained with grade of 32.59% TiO₂ at 28.04% recovery. It is found that low TiO₂ content and high content of iron-bearing silicate gangue minerals are the main factors affecting the ilmenite beneficiation indicators.

In order to analyze the strength variation characteristics of cemented backfill mass at different temperatures under dynamic loading, a SHPB impact test was performed to study the mechanical properties of cemented backfill mass under dynamic loading during the energy evolution process. The results show that the compressive strength of the cemented backfill mass under dynamic loading increases as the curing temperature rises, and presents obvious splitting tensile failure. It is also found that the stress-strain curves of backfill mass at different curing temperatures are similar, all consisting of three stages: quasi-elastic stage, plastic deformation stage and post-peak failure stage. The backfill mass experiences a wave impedance effect. At an approximate strain rate (100 s^-1), about 77% of the energy is reflected and about 2% of the energy is transmitted through the backfill mass during the impact process. As the curing time is prolonged and the curing temperature rises, the energy absorption density and transmissive energy of the backfill mass increase. The micro-analysis shows that with the rise of curing temperature, the internal hydration reaction of backfill mass occurs at a higher rate, leading to higher degree of hydration and more hydration products. Those hydration products gradually fill in the internal pores of backfill mass, resulting in denser microstructure. It further confirms that increasing curing temperature can improve the early strength of backfill mass.

In the east side of Yanqianshan Iron Mine of Anshan Iron and Steel Company, the transition from open-pit to underground mining causes failure and collapse of rock slope. In order to solve this problem, tests were performed by adopting numerical simulation and the base friction model to analyze the failure process and failure mode. The different collapse angles at different mining stages were explored, and development process of collapse area was summarized in terms of fissures. It is found that as mining operation proceeds, the collapse angle is reducing due to disturbance of mining activity; the collapse area undergoes four stages, including progressive fissure enrichment, deformation during aging, growth of slip surface, and collapse formation; and the slope failure in the east side of Yanqianshan Iron Mine is predominantly attributed to the sliding crack model of deformation.

To study the motion characteristics of particles in hydraulic lift pipelines during deep-sea mining, a set of particle image processing technique was proposed, including image preprocessing, binarization processing, morphological operations, edge detection of particles, and overlapping segmentation. This technique was used to identify and extract particle information from cross-sectional images of pipe obtained from hydraulic transportation simulation experiments, and the distribution and motion patterns of particles within the pipeline were also analyzed. The results show that the larger particles tend to aggregate near the pipe wall, where fluid flows at a lower velocity; the smaller particles are mainly concentrated at the center of the pipeline with the fluid at a higher velocity. The distribution of the average particle velocity along the radial direction of the pipeline follows a parabolic law of variation. The average velocity decreases as particle size increases, and also the velocity reaches the maximum at the center of pipe and then gradually decreases towards the wall. It is found that the proposed particle image processing technique can be effective in analyzing the motion characteristics of particles in pipeline.

When ultra-high strength steel with tensile strength more than 1 600 MPa and BS700 high-strength steel with tensile strength more than 760 MPa are joined together by metal active gas welding, weld cracks are prone to occur in the seam of joint. To solve this problem, comparative welding tests were performed by using ER70-G or ER307Mo welding wire with diameter of 1.0 mm, respectively, with initial welding current of 160-180 A, voltage of 21-24 V, and final welding current of 190-210 A, voltage of 23-26 V. The comparison of process and weldability show that welding with ER307Mo can lead to the sample with bending property obviously better than that by welding with ER70-G. The sample after welding with ER70-G can be found to have micro-cracks not going through the whole cross section of welding seam, with cracking rate on the cross section of seam reaching 35.29%, but no cracks are found on the section of welding seam by using ER307Mo. It is concluded that the ER307Mo welding wire is more suitable for welding ultra-high strength steel and BS700 high strength steel. The study has solved the cracking problem in the joint of ultra-high strength steel and BS700 high strength steel, which can provide a solution for the welding of dissimilar high-strength steel with larger difference in tensile strength.

Based on the current situation and demand in the field of commercial aircraft engine bracket, analysis and review of research progress in magnesium alloy were presented in terms of formability, corrosion resistance and flame retardancy, and the prospects of applications of magnesium alloys in aircraft engine bracket were also discussed.

The surface of 38CrMoAl steel was processed by ion nitriding at 560 ℃ with the mixture of nitrogen and argon as nitrogen source. After that, the friction and wear property of 38CrMoAl steel was studied. The results show that as the N₂ volume fraction in the mixed gas increases, the thickness of nitrided layer increases, and the surface hardness of the nitrided layer increases first and then decreases. By adjusting the volume fraction of N₂ in the mixed gas, the number of active nitrogen atoms can be changed, thus leading to the change in the phase composition of the nitrided layer. With N₂ and Ar in a volume ratio of 2∶3, γ′-Fe₄N phase is the major phase and ε-Fe_2-3N phase is the minor phase in the nitrided sample. With N₂ and Ar in a volume ratio of 3∶2, the nitrided layer has ε-Fe_2-3N phase as the major phase andγ′-Fe₄N as the minor phase. Compared with the substrate material, the ion-nitrided sample has a smaller friction coefficient and higher wear-resistance. With N₂ and Ar in a volume ratio of 3∶2, the ion-nitrided sample has its compound layer in a thickness of 21.4 μm, and its average friction coefficient up to 0.26, presenting good wear resistance. The mechanisms of friction and wear include fatigue, abrasion and oxidation.

By adjusting the pH value of electrokinetic remediation cathode and adding enhancers, the total removal rate of Cr from the contaminated soil by electrokinetic remediation technology was increased. Then, the change of energy consumption and law of Cr migration and distribution during the electrokinetic remediation project were explored. The results show that EDTA, citric acid and hydrochloric acid can significantly enhance the total Cr removal rate during the electrokinetic remediation process. The total removal rates of Cr were 24.47% and 23.24% respectively after 7 days of electrokinetic remediation without adjusting the pH value of the cathode, by adding EDTA and citric acid into the soil. The pH value of the cathode isn't adjusted, which results in an obvious polarization effect. In contrast, the total removal rates of Cr were 44.20% (4.9 times as much as the blank) and 36.80%, respectively, after 7 days of electrokinetic remediation with the pH value of the cathode controlled, by adding hydrochloric acid and citric acid to the soil, respectively. Controlling the pH value of the cathode can effectively prevent the precipitation of Cr in the cathode region, thus enhancing the removal rate of Cr, but won't significantly increase the energy consumption of the electrokinetic remediation process. This method can greatly increase the total removal rate of Cr in contaminated soil by electrokinetic remediation, which is of significance in guiding the remediation of heavy metal contaminated soil.