The connecting pipe in solar hot water system is made by TIG welding of thin-walled stainless steel and copper. As the welding of stainless steel and copper belongs to dissimilar metal welding and their physical properties are very different, thus the welding process is difficult and it is likely to cause a variety of defects in the welding process. In this paper, ANSYS software is used to simulate the welding process of stainless steel and copper, and the residual stress distributions in the welding process are obtained. The results show that: at the end of the welding cooling, large residual stress (253MPa) is remained in the junction area of the starting and ending position of welding, which is close to the yield strength of material at the same temperature. Therefore, there will be greater deformation in the junction area and more cracks inside. Meanwhile, the stress distributions of stainless steel and copper tubes in the welding process are greatly different. Different volume changes emerge in two tubes, which are harmful to the welding seam and also leads to the unfitness of dimensional tolerance of welding parts, resulting in the scrapping of welding parts. The results provide references and theoretical basis for the welding technology of dissimilar materials.

Direct-to-blister copper smelting is an important smelting process due to its short process, low energy consumption and environmental protection. This study attempts to use high-grade chalcocite as the raw material for direct-to-blister smelting to realize the production of blister in a single furnace. The issues and required conditions of the process are analyzed from the thermodynamics viewpoint. By adjusting the ratio of iron to silica, the flux content and other raw material components, the direct-to-blister smelting is finally realized in a lab-scale. The copper recovery is over 82%, and the copper loss in the slag is analyzed in detail. This work offers a theoretical guidance for the short-process smelting of high-grade copper concentrate.

In this study, the spot welding of rapidly solidified Ni-19.8%Sn alloy foils has been conducted by a micro-type capacitor discharge welder. The configuration and microstructural morphology of the joint were examined experimentally and he temperature of the micro nugget was analyzed numerically. The results show that the micro-joint consists of an oblate spheroid nugget and a 2.0~3.0 m thick bond zone. The microstructure of the joint is fine and homogeneous and there is no coarsening sign in the parent materials near nugget. During solidification, the cooling rate of nugget is so high to the order of 106K/s that the eutectic reaction of L  α-Ni + Ni3Sn was suppressed or at least partly suppressed and almost all of the liquid within the joint solidified into supersaturated α-Ni. Therefore, the joint microstructure which is consistent with the microstructure of the alloy foils shows the characteristics of rapid solidification. In addition，a kind of streamline due to vortex flow in micro nugget, with dispersed dross distributes in cluster along the streamline, is formed under electromagnetic force and electrode pressure.