Determining process parameters for successful material reclamation of lead-free brass chips using hot forging operations: Lubrication

When small and hollow components are being manufactured, it is not uncommon that a majority of the workpiece material is removed by machining. A demand for parts made with lead-free brass alloys can potentially increase the manufacturing cost and therefore it is necessary to investigate ways to increase the material utilization. As part of a more resource efficient production, a method for reusing chips from metal cutting in brass using hot forging operations is investigated. In this study, the brass alloy CW724R is used. Different lubrication agents are used, including mineral oil and vegetable oil with and without addition of nano-sized graphite platelets, GnP, in the production of green compacts. Material properties of the green compacts and the finished products are analyzed using mechanical testing and microscopy. Quality of the finished product is evaluated using multi-variable regression analysis. The results of the statistical analysis indicate the best mechanical properties when using 0.2 - 0.25 vol. % GnP suspension in oil and 0.15 - 0.2 wt. % oil mixed with the chips before compaction. Microscopy shows diffusion bonding between the chips after forging, yet some porosities is still observed. This indicates potential for the investigated material reclamation method.