In view of interference of the existence of selenium in determination of gold and silver in crude selenium sample, the sample with an addition of concentrated sulfuric acid was firstly heated to remove selenium. Then, sodium chloride solution was added to precipitate silver therein, and the obtained residue after filtration was taken for gold and silver determination using fire assay by gravimetry. Thus, a process of heating with sulfuric acid to remove selenium followed by fire assay gravimetry was established for continuous determination of gold and silver in crude selenium, and the effects of residual selenium, sulfuric acid dosage and heating time on the determination results were also discussed. Furthermore, such continuous determination process was also compared to the industrial standard method in terms of the analysis of gold and silver in crude selenium. By using the proposed continuous method, the relative standard deviations (RSD₇) of gold was within a range of 0.54%-1.30%, and the RSD₇ of silver was within a range of 0.28%-0.39%. The spike recovery of gold was 94.6%-101.3%, and the spike recovery of silver was 96.3%-100.1%. It is shown that the analysis results are consistent with those by industrial standard method. It is concluded that the proposed determination method, being fast and accurate, is suitable for determination of gold and silver in crude selenium.

A copper-lead-zinc polymetallic sulfide ore, being characterized by complex dissemination of main minerals and intimate intergrowth of valuable minerals and gangue, was taken for study. In an experiment, the raw ore grading 0.21% Cu, 2.37% Pb and 3.01% Zn was treated with a weak-alkali process, consisting of Cu-Pb bulk flotation, Cu/Pb separation and Zn flotation. With A22 as a copper-lead bulk flotation collector, TZ01 and zinc sulphate as depressants of zinc and sulfur minerals, CZ08 as a zinc flotation collector, sodium sulfite and CMC as depressants for Cu/Pb separation, a copper concentrate grading 22.09% Cu at 70.48% recovery, a lead concentrate grading 59.48% Pb at 89.35% recovery, and a zinc concentrate grading 45.00% Zn at 86.96% recovery were yielded.

Fe-Cr-B based wear-resistant coating was prepared on the surface of 45 steel by ultra-high-speed laser cladding. The effects of laser power, scanning speed and powder feeding speed on the aspect ratio and crack of single pass cladding layer were studied by orthogonal experimental method, and the effects of overlap rates on the surface quality of cladded layer was also studied. The optimal process parameters were determined as follows: laser power of 2 300 W, scanning speed of 250 mm/s, powder feeding speed of 24 g/min, and overlap rate of 70%. The results show that the hardness of the coating is between 754HV_0.2 and 831HV_0.2, which is 2.36 times to 2.60 times of the matrix hardness. Under the same conditions, the volume wear of the coating is only 3.64% of electroplated hard chromium coating.

In order to comprehensively utilize iron-containing dust and consume alkaline residue from petrochemical industry, a sintering pot test was conducted by adding iron-containing dust and the alkaline residue from petrochemical industry into raw materials for sintering. The results show that an addition of iron-containing dust and the alkaline residue from petrochemical industry can not only improve vertical sintering speed, utilization coefficient, yield rate and tumbler index, but also lead to increased content of alkali metals and Zn, as well as falling in the TFe content in the sintered ores. Thus, the sintered ore presents poor reduction performance, and poor low-temperature reduction pulverization indices. It is found that the raw material with the addition of iron-containing dust at an amount of 0.5% and the addition of alkaline residue from petrochemical industry at an amount of 0.05% can meet the requirement for feed to furnace, and also make it possible for the comprehensive utilization of iron-containing dust and consumption of alkaline residue from petrochemical industry.

Flotation tests were conducted for a low-grade copper-nickel sulfide ore with high content of mud and magnesium oxide from Xinjiang. Using sodium carboxymethyl cellulose and sodium silicate as a combined inhibitor, butyl xanthoxanthate and butyl ammonium black as a combined collector, a closed-circuit test with a flowsheet consisting of a Cu-Ni bulk flotation and a Cu/Ni separation produced a copper concentrate grading 25.11% Cu at 79.90% recovery, with MgO content of 2.02%, as well as a nickel concentrate grading 6.98% Ni at 75.01% recovery, with MgO content of 5.32%. It is concluded that effective recovery and separation of copper and nickel can be actualized.

A typical metal mine with a smelter in Hunan Province was taken as an example, and 22 key factors affecting the environmental risk diffusion path of heavy metal pollution area were chosen based on data crawling and on-site case investigation, as well as systematical sorting. Nemerow integrated pollution index (NIPI) of soil was calculated using Nemerow pollution index method, and then was used to aid the identification of key factors. Results show that atmospheric deposition and soil permeability are selected as the environmental risk diffusion path for heavy metal pollution of soil based on the analytic hierarchy process, and the key factors for environmental risk diffusion include distance from pollution source, PM₁₀ content in air, hard cover on ground surface, anti-seepage measures, soil pH value and soil organic matter (SOM) content. It is found that the NIPI of the soil is positively correlated to soil pH value, SOM, PM₁₀, but negatively correlated to the distance from pollution source, hard cover on soil surface and anti-seepage measures. The correlation coefficient fits well with the factor weight (R²=0.63).

316L stainless steel coatings were prepared on the surface of 304 stainless steel by using laser cladding at different scanning speed, and then metallographic microscopy, X-ray diffractometer, scanning electron microscopy and microhardness tester were adopted respectively to investigate the macroscopic morphology, phase composition, microscopic structure and microhardness for the coatings. The results showed that the 316L coating had a single-phase austenitic structure, and as the scanning speed increased, the grain size of the coating became smaller due to the reduction in the laser power density and heat input, and an increase in the cooling speed. It is found that the microhardness of the coatings is positively correlated with scanning speed, and the 316L coatings prepared by laser cladding at a scanning speed of 1 400 mm/min presents the highest microhardness of about 275HV_0.3. The improvement of the microhardness of the coating is ascribed to the effect of solid solution strengthening caused by lattice distortion combined with the effect of fine crystal strengthening. The wear test showed that the average friction coefficient of 316L coatings was significantly lower than that of 304 stainless steel substrate. And the 316L coating prepared by laser cladding at 1 400 mm/min has a friction coefficient of 0.424 and wear rate of 2.29 × 10^-6 mm³/(N·m), and is prone to abrasive wear.

Experiments on tempering at different cooling rates were conducted for annealed 30CrMnSiA steel to investigate the effect of cooling rate during tempering on the properties of tempered 30CrMnSiA steel and its microstructure evolution. The results show that the cooling rate during tempering has brought slight effect to the hardness, and a certain influence to impact properties of 30CrMnSiA steel. After tempering at 510 ℃, the 30CrMnSiA steel has its surface mainly subjected to compressive stress and the center subjected to tensile stress. A faster cooling rate during tempering will result in a higher residual stress on the surface of the sample. During the tempering process, C element mainly combines with Fe element to form Fe-C compounds, while a trace of C element, together with Cr and Si elements, forms Cr-C compounds and Si-C compounds. It is found that the rapid cooling rate has slight effect on the content and size of carbides.

Magnetic separation tests were carried out by adopting a pulsating high gradient magnetic separators (HGMS) for low-grade manganese rhodochrosite ores from Yingjiang County of Yunnan Province, with more than 50% passing size of the raw ore finer than -0.019 mm, TMn grade of 6.72% and manganese carbonate content of 84.97%. Based on the laboratory test applying a SLon-100 type cyclic pulsating HGMS, a pilot test was conducted with a SLon-500 type vertical ring pulsating HGMS, by adopting an optimized processing flowsheet consisting of one roughing, one scavenging and a cleaning process of the scavenging concentrate, a manganese concentrate was produced with TMn grade and recovery of 16.77% and 87.61%, respectively.

Experimental study on flocculation sedimentation was carried out in a laboratory for the lead processing tailings from a lead-zinc mine, and the flocculant type, flocculant dosage and feed concentration were all investigated. Then, the selected flocculant was applied into a lead-zinc-sulfur flotation. The results show that the anionic PAM flocculant AX868 presents a better sedimentation effect, and its addition into the flotation system leads to the obtained flotation indicators equivalent to those by using clear water. It is found that an addition of 20 g/t AX868 into the thickener with a diameter of 36 m can meet the sedimentation requirements in industrial production.