Preparation Of Oxygen-free Copper By CaB6 Thermal Reduction Method And Its Reaction Process

Anaerobic copper is a kind of pure copper with high conductivity,high chemical purity,low impurity content,and an extremely low oxygen content.Therefore,it has excellent conductivity and thermal conductivity,and is widely used in electronics and communication industries.In recent years,the chemical composition standards of oxygen-free copper at home and abroad together with the physical properties inspection standards of some copper materials have been upgraded continuously,therefore producing high-quality and low-cost oxygen-free copper is a major issue to deal with.However,compared with developed countries,there is a certain gap in the depth of theoretical research and technological operation level of oxygen-free copper in China.Therefore,it is of great significance to study the deoxidation process and production process of electrolytic copper for improving the quality of oxygen-free copper.The research content of this subject can be devided into the following three parts:(1)The process of preparing calcium boride deoxidizer by thermal reduction was studied,and the chemical,physical and morphological analysis of the prepared calcium boride was carried out.(2)The existing form of oxygen in raw material electrolytic copper was studied,and the thermodynamic analysis of the chemical reaction was carried out on this basis,providing a theoretical basis for the preparation of oxygen-free copper by thermal reduction of calcium boride.(3)The temperature range of deoxidization smelting for the preparation of oxygen-free copper by thermal reduction of calcium boride was investigated.On this basis,the optimum technological parameters of single factors such as the amount of calcium boride,deoxidization temperature and deoxidization time on the deoxidization degree,conductivity and mechanical properties of electrolytic copper were studied.Through the research,the main results of this paper are as follows:(1)Calcium boride was prepared by direct current arc furnace thermal reduction,and purified by acid pickling.The purified calcium boride was qualitatively analyzed by XRF,phase analysis(XRD)and micro-morphology analysis(SEM,TEM).The results show that the main phase of the raw material is CaB6 with cubic crystal form,and a small amount of CaB6 exists in other atom ratio.(2)XRF qualitative analysis,chemical quantitative analysis,phase analysis(XRD)and microscopic morphology analysis(SEM,TEM)of raw material electrolytic copper were carried out,the results show that oxygen exists as cuprous oxide in copper.On this basis,the thermodynamic process of preparing oxygen-free copper with thermal reduction of calcium boride was studied.Gibbs free energy of the reactionis obtained(ΔGθ=2533983-2.9647).(3)TG-DSC thermal analysis of raw material electrolytic copper and cuprous oxide reagent was carried out to determine the optimum deoxidation temperature range.On this basis,the deoxidization experiment of calcium boride was carried out.The effects of deoxidization temperature,time and calcium boride content on Deoxidization rate,electrical conductivity and mechanical properties were studied.The optimum technological conditions were obtained:at 1200℃,adding 0.7%calcium boride,stay for 3 minutes to deoxygenate,the oxygen content of the product is about 30 ppm,the relative conductivity is 99.3%,the tensile strength is 305.8 MPa and the elongation is 34.8%.