Effect of deoxidizers (phosphorous and carbonaceous) on high-purity cast copper

The production of high-purity copper castings (99.9%) faces the challenge of oxygen-induced porosity, which severely impairs copper properties. For this reason, copper refining (deoxidation) becomes a mandatory step in the process. This study investigated the impact of three deoxidizing agents on the physical and chemical properties of molten copper in an environment that simulates industrial practice. The deoxidizing agents were graphite powder (C), phosphor copper (CuP15%), and calcium carbide (CaC 2 ). The experimental methodology involved casting specimens in a gas furnace, with the controlled addition of each deoxidizer at three dosage coefficients (under-dosage, stoichiometric dosage, and over-dosage) based on the stoichiometry for removing 600 ppm of oxygen. Additionally, “control” tests using only copper chips were performed to serve as a control group and isolate the effects of the deoxidizing agents. The samples were then subjected to chemical characterization by optical emission spectroscopy, eddy current electrical conductivity measurement (non-destructive testing), and quantitative porosity analysis via ImageJ. The results revealed significant differences in the impact of each deoxidizer on the molten copper. The control samples (without active deoxidizer) established a baseline highlighting the necessity of deoxidation. The control sample maintained a conductivity between 78% and 84% IACS (International Annealed Copper Standard). Graphite reached a minimum of 73.42% IACS, and the conductivity of CaC 2 did not exceed 80% IACS. Graphite and CaC 2 exhibited numerous and refined porosity, in contrast to the control sample, which had large and dispersed pores (up to 8.13 mm 2 ). Morphological analysis of the pores suggests slow reaction kinetics of the carbon-based agents, which resulted in continuous gas generation (CO) within the mold during solidification. In contrast, CuP15% proved to be the most effective agent, with porosity values lower than the control sample and resulting in the highest electrical conductivity of 87.3% IACS found in the research. This study contributes to the optimization of copper production processes, providing clear parameters and scientific evidence for the metallurgical industry.