Оптимізація складу флюсу NaCl-KCl для підвищення якості очищення алюмінієвих сплавів

• Дата: 2025
• Автори: Петриченко, С.В., Коваленко, В.В., Ямшинський, М.М., Биба, Є.Г., Лук’яненко, І.В., Мініцький, А.В., Кивгило, Б.В., Барабаш, М.Ю.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Physico-technological Institute of Metals and Alloys 2025
• Теми: вторинні алюмінієві сплави; флюс NaCl–KCl; очищення розплаву; мікроструктура; механічні властивості; неметалеві включення; ливарні властивості
• Онлайн доступ: https://www.metalsandcasting.com/index.php/mcu/article/view/306
• Назва журналу: Metal and Casting of Ukraine

The study is devoted to optimizing the composition of flux based on sodium chloride (NaCl) and potassium chloride (KCl) to improve the quality of secondary aluminum alloys obtained from various types of aluminum scrap, including armor scrap, household scrap, industrial chips, and return scrap from own production. The aim of the work is to analyze the effect of a binary eutectic mixture of NaCl-KCl (50 mol% NaCl and 50 mol% KCl) on the chemical composition, microstructure, mechanical and casting properties of alloys, as well as to determine the optimal flux dosage to ensure high quality castings suitable for use in the aviation industry. During the study, different types of aluminum scrap were used, which made it possible to evaluate the effectiveness of the flux in the processing of raw materials with varying levels of contamination. The flux was added in concentrations of 1%, 2%, 3%, 4%, 5%, 10 %, and 15 % of the melt mass after drying at 120 °C to remove moisture. The samples were poured into a metal mold pre-treated with non-stick paint at a temperature of 200 °C. The results showed that the use of NaCl-KCl flux contributes to a significant purification of the melt from non-metallic inclusions, oxides (Al2O3, MgO, SiO2) and gases, in particular hydrogen, which improves the quality of the alloy. The maximum aluminum content (95.13 %) was achieved with 15 % flux, which indicates the effective removal of impurities such as silicon, magnesium, manganese, and zinc. In particular, the silicon content is reduced to 0.54-0.90 % already at a flux content of 1 %, which indicates its high efficiency in removing silicon inclusions. However, excessive fluxing (over 5 %) leads to a decrease in the content of alloying elements, which negatively affects the plasticity of the alloy. Studies of temporary tensile strength showed that the optimal flux concentration range (3-5 %) provides maximum strength up to 235 MPa and fluidity up to 585 mm, which is associated with effective melt cleaning and viscosity reduction. At the same time, an increase in flux concentration to 15 % contributes to a decrease in plasticity (relative elongation decreases from 4.41 % to 1.32 %, narrowing from 4.52 % to 0.85 %) due to a decrease in silicon eutectics and the formation of brittle phases. Microstructural analysis confirmed that at a flux content of 2-4 %, a homogeneous structure with a plastic type of fracture is formed, while at 15 %, brittle intergranular cracking is observed due to excessive slag formation. The fluidity of the alloy increases in the range of 5-10 % flux due to a decrease in viscosity and the removal of inclusions, but excess flux (over 10 %) reduces this indicator due to the formation of thick slag films and local cooling of the melt. An optimal flux content of 3 to 5 % provides a balance between purification, preservation of alloying elements, and high fluidity, making the alloy suitable for precision casting. Thus, NaCl-KCl flux is effective for cleaning secondary aluminum, allowing for increased aluminum content, reduced impurities, and improved mechanical properties. An optimal flux concentration of 3 to 5 % is recommended for industrial use, as it ensures high alloy quality, energy efficiency, and compliance with standards for high-tech applications.