Characterization and Formation Mechanism Analysis of Leakage Defects in Hot-dip Galvanized Automotive Steel Plate Based on Focused Ion Beam Cutting Sample Preparation
WEI Langlang1, TIAN Xiugang2, LIANG Jian1, MIAO Bin1,*, YANG Feng2, LI Yang2, ZHENG Shijian1,*
1 School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300401, China 2 Technical Center of Tangshan Iron and Steel Group Co., Ltd., Tangshan 063000, Hebei, China
Abstract: Leakage defects are easily formed during the hot-dip galvanizing process of advanced high-strength automotive steel plates. It is generally believed that the segregation of alloy elements causes the leakage defects ranging from tens to hundreds of micrometers. These defects can be well characterized and analyzed through metallographic microscopy and scanning electron microscopy to determine their formation reasons. However, for leakage defects with sizes of several micrometers like pinhole leakage defects and other ones with attached structures, conventional plane or cross-sectional specimen observation cannot provide precise characterization, restricting the understanding of their formation mechanism. By adopting the focused ion beam (FIB) cutting technique, this work prepared cross-sectional samples at certain leakage defect positions of the galvanized layer of 780 MPa dual-phase steel automobile plate, and performed internal structure and composition distribution characterization at the defect-substrate interfaces via transmission electron microscopy. The results indicate that there are two types of micrometer-level leakage defects in the galvanized layer, of which the formation mechanism differs from the general understanding. The first type (type-Ⅰ) of leakage defects are caused by the tiny pit defects on the steel plate surface before galvanizing, and have internal interface layers’ phases and composition similar to those in the non-leakage area. The second type (type-Ⅱ) of leakage defects mainly originate from the surface residual iron particles detrimental to the normal galvanizing reaction, and have loose attached structures. Hence it is recommended to focus and reduce surface pit defects and remove surface residual iron particles at the rolling stage of steel plates in order to inhibit the formation of these two types of micrometer-level leakage defects in the galvanized layers of 780 MPa dual-phase steel and other advanced high-strength galvanized automotive steel plates.
1 Liu H, Li F, Shi W, et al. Surface and Coatings Technology, 2012, 206, 3428. 2 Wang J, Huang Q D, Liu J, et al. Chinese Journal of Materials Research, 2018, 32(8), 631 (in Chinese). 王劲, 黄青丹, 刘静, 等. 材料研究学报, 2018, 32(8), 631. 3 Fan C L, Li Q H. Hebei Metallurgy, 2013(6), 37 (in Chinese). 范春磊, 李庆华. 河北冶金, 2013(6), 37. 4 Guo T X. Steel Rolling, 2007, 24(2), 55 (in Chinese). 郭太雄. 轧钢, 2007, 24(2), 55. 5 Yang H L, Zhang S G, Hong J Y, et al. Chinese Journal of Materials Research, 2014, 28(1), 23 (in Chinese). 杨洪林, 张深根, 洪继要, 等. 材料研究学报, 2014, 28(1), 23. 6 Jin X, Bi W, Wang L, et al. Engineering Failure Analysis, 2020, 115, 104598. 7 Li X J, Ma E Q, Xiao Y Y, et al. Metallurgical Power, 2022(3), 11 (in Chinese). 李雄杰, 马二清, 肖洋洋, 等. 冶金动力, 2022(3), 11. 8 Li Y, Cui Y, Xu H W, et al. Electroplating & Finishing, 2013, 32(5), 32 (in Chinese). 李研, 崔阳, 徐海卫, 等. 电镀与涂饰, 2013, 32(5), 32. 9 Ma M N, Song J S, Hou G J, et al. Metallurgical Management, 2022(14), 96 (in Chinese). 马孟宁, 宋吉硕, 侯耿杰, 等. 冶金管理, 2022(14), 96. 10 Deng Z J, Lin C J. Surface and Coating, Metallurgical Industry Press, China, 2017 (in Chinese). 邓照军, 林承江. 表面与涂镀, 冶金工业出版社, 2017. 11 Shi L J, Xie Y K, Zuo Y, et al. Electroplating & Finishing, 2019, 38(21), 1172 (in Chinese). 施刘健, 谢义康, 左岳, 等. 电镀与涂饰, 2019, 38(21), 1172. 12 Wu X S, Cui Q Y, Zheng X F, et al. Chinese Metallurgy, 2018, 28(2), 57 (in Chinese). 巫雪松, 崔秋艳, 郑晓飞, 等. 中国冶金, 2018, 28(2), 57. 13 Wu Q W, Zhao A M, Yao S, et al. Materials Science Forum, 2018, 913, 294. 14 Bi W Z, Jin X Y, Wang L. Baosteel Technical Research, 2015, 9(3), 54. 15 Aslam I, Li B, Martens R L, et al. Materials Characterization, 2016, 120, 63. 16 Jin X, Hu G, Wang L, et al. Surface and Coatings Technology, 2020, 382, 125172. 17 Zhu M, Jin X Y, Chen G. Baosteel Technology, 2022(2), 1 (in Chinese). 朱敏, 金鑫焱, 陈光. 宝钢技术, 2022(2), 1. 18 Chu S J, Jin X Y, Bi W Z. Steel, 2021, 56(12), 126 (in Chinese). 储双杰, 金鑫焱, 毕文珍. 钢铁, 2021, 56(12), 126. 19 Wang K K, Hsu C W, Chang L, et al. Surface and Coatings Technology, 2020, 396, 125969. 20 Chen K F, Aslam I, Li B, et al. Metallurgical and Materials Transactions A, 2019, 50, 3748. 21 Deng Z J. Development and microstructure of 600 MPa grade high aluminum cold rolled dual-phase steel. Ph. D. Thesis, Wuhan University of Science and Technology, China, 2012 (in Chinese). 邓照军. 600 MPa级高铝系冷轧双相钢的开发及微观组织研究. 博士学位论文, 武汉科技大学, 2012. 22 Liang J, Miao B, Xiong Z L, et al. Applied Surface Science, 2023, 614, 156153.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2025, Vol. 39 
