Possibilities of Reducing Internal Scrap Rates and Increase Scrap Recyclability of Dilute Copper Alloys from Vertical Upwards Continuous Cast (VUCC) Process

Sammanfattning: Copper and copper alloys are important material systems for the electrification of society. The high workability of the materials makes them appropriate in numerous different applications which require highly conductive properties. One main advantage of Cu and Cu-bearing alloys is the eminent ability to be repeatedly recycled without losing the advantageous properties. This raises the question whether scrap alloys from secondary copper production can be reintroduced into continuous copper casting processes to increase the overall recyclability. The primary goal was to identify current scrap rates from the Vertical Upwards Continuous Cast (VUCC) process and assess methods to increase scrap recyclability. Scrap from the VUCC process was found to constitute of 16% of the total monthly production volume of CuMg0.49 alloy with a diameter of 30 mm at Elcowire AB. Scrap originated mainly from the process start-up phase and also from process related issues. Studies were carried out to evaluate if additional 400 ppm Mg decreased the start-up time and scrap rate. The method showed no beneficial results to decreasing the start-up time and further assessments are needed. No negative effect was observed regarding coil composition, but instead indicated the difficulties to control the Mg content in the melt throughout production. Mg losses to slag were found by the means of SEM and XEDS as MgO particles. The exposed Cu melt must therefore be more sufficiently protected, where an inert Ar gas flux may be applied. There is currently no feasible method to incorporate scrap into the VUCC process without redesigning the entire process. Produced scrap may instead be used in the SCR® rolling mill during ETP copper production, where results showed that the impurity content must be controlled, and Mg content is the main limiting factor. Further assessments are needed in terms of contaminant contribution to slag formation, effect on finished ETP copper and economic viability. The method does, however, show great promise and can be applied to various Cu-bearing alloys.