Thermal Decoating and Composition Controlled of Aerospace Aluminum Alloys
QIAN Guoyu1, WANG Zhi1, SUN Zhi1, LIU Chunwei1, YAN Pengcheng2
1 Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China 2 Boeing (China) Co. Ltd, Beijing 100027, China
Abstract: The refractory inorganic salt coating and high zinc content in the mixed waste were the main cause of the retired aircraft of green and efficient recycling difficult. The characteristics of the coating containing inorganic salts and the thermal decomposition mechanism were studied by means of thermogrity, roasting and washing. The volatilization and removal of Zinc (Zn) from aluminum alloy melts under vacuum-electromagne-tic field were investigated by means of calculation and the coupling strengthening of vacuum-electromagnetic. A new method for recovering waste aviation aluminum materials by roasting-washing and vacuum-electromagnetic strengthening was proposed. The study of characteristics and decomposition of coating showed that the thermal decomposition of coating with BaCrO4 and SrCrO4 and other inorganic salt underwent the process of macromolecule organic matter-scorch matter-inorganic film. The inorganic film was closely attached to the cracked aluminum alloy surface, which makes it difficult to remove by washing with clean water. The deep removal of inorganic salt coating was realized by 15% dilute nitrate damage to the cracked surface and erosion to the inorganic salt, and the average content of inorganic components such as Cr, Ba and Sr on the surface of aluminum alloy decreased to less than 0.1%. The study of the vacuum-electromagnetic removing Zn showed that beneficial element magnesium (Mg) can be removed simultaneously during Zn removal. The removal of Zn and Mg was enhanced with the increase of temperature (750—900 ℃), and the degree of Zn volatilization was greater than Mg. When kept at 900 ℃ for 60 min, the content of Zn and Mg decreased to about 0.03% and 0.05% respectively. Further comparative study of 50 Hz and 200 Hz showed that the higher frequency of 200 Hz and higher power (10 kW) were more conducive to the rapid depth removal of Zn, and the removal rate of Zn increased to 0.28%/min within 10 min (0.28%/min at 50 Hz). Taking the mixed waste with the weight ratio of 2024 and 7075 used aviation aluminum as 1∶1 as the object, the new method of roasting-wash, vacuum-electromagnetic strengthening was adopted to prepare the aluminum alloy satisfying the composition requirements of 2024 aluminum alloy.
1 http://www. afraassociation. org/. 2 http://www. afraassociation. org/news.cfm? newsid=162. 3 Menzie W D, Barry J J, Bleiwas D I, et al. The Global Flow of Aluminum From 2006 Through 2025. U.S. Geological Survey,2010. 4 Green J A S. Aluminum Recycling and Processing for Energy Conservation and Sustainability. ASM International,2007. 5 Nancy M. Energy and Environmental Profile of the U.S. Aluminum Industry. U.S. Department of Environment,1997. 6 Kvithyld A, Meskers C E M, Gaal S, et al. JOM,2008,60(8),47. 7 Lytle F W, Greegor R B, Bibbins G L, et al. Corrosion Science,1995,37(3),349. 8 Sinko J. Progress in Organic Coatings,2001,42(3-4),267. 9 Bierwagen G P, Tallman D E. Progress in Organic Coatings,2001,41(4),201. 10 Lerma J A R M, Jung I H, Broch U M E. Metallurgical and Materials Transactions B,2016,47B,1976. 11 Boeree C R. Zinc removal from aircraft aluminium-alloy scrap. Master's Thesis, Delft University of Technology, Netherlands,2011. 12 Utigard, T A. JOM,1998,50,38. 13 Zhang L. Mineral Processing and Extractive Metallurgy Review,2000,32(3),150. 14 Lerma J A M. Recycling of aerospace aluminum components into new valuable products. Ph. D. Thesis, McGill University, Montreal, QC,2016. 15 Kvithyld A, Kaczorowski J,Engh T A. TMS Annual Meeting & Exhibition, Washington,2004,pp.151. 16 Meskers C E M, Reuter M A, Boin U, et al. Metallurgical and Materials Transactions B,2008,39,500. 17 Vyazovkin S, Burnham A K, Criado J M, et al. Thermochimica Acta,2011,520(1-2),1. 18 Zhang J L. China Foundry Machinery & Technology,1996(5),51(in Chinese). 张健林.中国铸造装备与技术,1996(5),51. 19 Xu J W, Chen X H, Zhang Y. China Foundry,2003(11),66. 徐加文,陈宪宏,张毅.铸造,2003(11),66.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2021, Vol. 35 
