Metals

Given the importance of nickel in lithium-ion batteries and the expectation of the growth in electric vehicles and electrical devices, the demand for nickel in battery production is expected to increase dramatically. Nickel is primarily sourced from laterite saprolite ore, and there is now substantial interest in moving from ferronickel smelting technology to nickel matte technology in its processing to produce high-grade nickel. This research involved a thermodynamic modelling and lab–scale experiment on the smelting of nickel matte. Nickel concentrate from laterite saprolite was used, and CaS, produced from commercially available gypsum, was employed as a sulfurizing agent. The matte smelting experiment was conducted at 1500 °C to optimize CaS and C consumption. During smelting with CaS, matte particles form, although sufficient reduction of nickel and iron from the concentrate is not achieved. By consuming carbon, the reduction potential of iron is increased, and this process, along with enriching the matte with iron, aids in the transportation of nickel. At a nickel grade in the matte with a Ni/Fe ratio of approximately 1, the nickel recovery only reached 63%. Upon achieving a nickel recovery exceeding 93%, the Ni/Fe ratio reached 0.44, corresponding to a nickel grade reduction to 22.78%. By employing analytical techniques and thermodynamic modelling, we have successfully determined the sulfidizing of nickel, identified the ideal CaS and C additions, and characterized the structure and quality of the slag produced during nickel matte smelting, supplying vital technological data necessary for practical application.

In this work, a laser lap-welded joint of galvanized steel/Mg and a laser lap-welded joint of galvanized steel/Mg assisted by ultrasonic vibration were compared. By adjusting the laser beam power and ultrasonic amplitude, the appropriate welding process parameters were obtained. The weld formation, microstructure and mechanical properties were studied and analyzed. The results indicated that the addition of ultrasonic vibration generated an excitation force with a certain frequency and amplitude on the weldment, making the molten metal in the molten pool produce ultrasonic forced vibration, and producing the effects of cavitation, acoustic streaming, mechanical stirring and heat, thus reducing welding residual stress and welding-deformation, porosity and incomplete-fusion defects. In addition, it can make the fusion zone transition evenly, improve the wettability, refine the weld grain, and reduce the average grain area from 583 μm² to 324 μm². Moreover, the distribution of Mg-Zn reinforcing phase at the interface was more uniform and denser, and the maximum tensile shear strength increased from 179.9 N/mm to 290 N/mm, indicating that the addition of ultrasonic vibration was conducive to improving the comprehensive mechanical properties of the joint.

As the work hardening rate increases during the cold drawing of non-heat-treated steel (NHT steel), a significant loss in ductility and toughness can occur, leading to reduced formability and part quality. In this study, a bidirectional drawing process consisting of alternating forward and reverse passes is proposed to mitigate these issues and enhance the mechanical performance of the steel. Mechanical property evaluations, including tensile testing and three-point bending tests, were conducted to assess the effects of bidirectional drawing compared to conventional unidirectional drawing. The results showed that the bidirectionally drawn wire maintained a similar tensile strength to that of the unidirectionally drawn wire at a 70% area reduction, while exhibiting a 12% improvement in elongation. Microstructural analysis revealed grain refinement and reduced texture anisotropy in the bidirectionally drawn specimens, contributing to the observed enhancement in ductility. These findings indicate that bidirectional drawing is a promising approach for improving the formability and overall quality of high-strength, NHT steel components.