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Pure copper was subjected to high-pressure surface rolling (HPSR) to obtain a surface gradient layer. Effects of HPSR parameters on the surface microstructure and microhardness of Cu were investigated by using optical microscopy, transmission electronic microscopy, X-ray diffraction, and the microhardness test. The HPSR surface layer has a gradient microstructure consisting of increasingly refined grains with decreasing depth from the treated surface (DFS). The thicknesses of the refined surface layer can be up to ~1.8 mm, and the grain size of the topmost surface is down to ~88 nm, depending on the HPSR parameters including pressure, time, and temperature. Microhardness of HPSR samples increases with decreasing DFS, with a maximum of ~2.4 times that of the undeformed matrix. The present results indicated that HPSR could be an effective method for the production of a mm-thick surface layer on Cu with gradient microstructure and property.

This paper introduces a new process to process noble lead by vacuum distillation, which is produced from the fire reduction smelting of lead anode slime with a large number of valuable and precious metals. Lead anode slime is important as a raw material for the extraction of precious metals. However, some of the shortcomings of the traditional process, such as serious pollution, complex processes, large resource consumption, and low metal recovery rate, must be overcome. Based on a study of the saturated vapor pressure in the metal and vapor–liquid equilibrium diagram of a binary system, we carried out a large-scale recovery experiment for bismuth and lead with the enrichment of silver and copper. The experimental results show that the copper and silver contents in the residue are higher than 80%. Secondary continuous vacuum distillation resulted in a residue with a Ag content of less than 20 g/t. At the same time, the direct yield of silver from the whole process is higher than 99%, and the evaporation contents of Pb and Bi are above 90%. Achieved a comprehensive recovery of valuable metals recycling.

This paper introduces a new process for refining crude lead by vacuum distillation. The saturated vapor pressures of lead and impurity elements were calculated, and the removal effect of impurity elements was quantitatively predicted using the vapor-liquid equilibrium diagram. In addition, the low temperature followed by high temperature vacuum distillation method and the high temperature followed by low temperature method were adopted to adjust the order of impurity removal. The refining effect was experimentally studied using these two methods, and the best parameters were determined. The predictions are in close agreement with the experimental results. Based on theoretical and experimental analyses, a new, clean and efficient process for refining crude lead was developed. First, the crude lead was distilled by vacuum distillation at 10 Pa and 1673 K for 30 min, and then, the volatiles and residues were collected. Second, the volatiles were vacuum distilled at 10 Pa and 1273 K for 30 min. The removal rates of Cu, Sn, Ag, Zn, Sb and Bi were 99.73%, 99.72%, 96.23%, 90.78%, 74.80% and 8.82% respectively, and the purity of Pb reached 99.03%.