溶融亜鉛めっき浴中のトップドロスの構造解析と機械的性質

• Published in: 鉄と鋼 Vol. 105; no. 7; pp. 716 - 723
• Main Authors: 小西, 剛嗣, 三木, 順平, 柴田, 実奈, 根本, 侑, 潮田, 浩作
• Format: Journal Article
• Language: Japanese
• Published: 一般社団法人 日本鉄鋼協会 2019
• Subjects: crystal structure; electron back scattering diffraction; Fe2Al5Znx; intermetallic compounds; mechanical property; molten zinc; top dross
• ISSN: 0021-1575; 1883-2954
• DOI: 10.2355/tetsutohagane.TETSU-2018-127

In a molten zinc bath in a continuous galvanizing line (CGL), top dross particles crystallize as Fe-Al-Zn intermetallic compounds. These particles easily adhere to the steel sheets causing surface defects. Therefore, controlling the top dross particles is a key issue. The present study focused on the structural and mechanical characterizations of top dross particles using an electron probe micro analyzer, X-ray diffraction, electron back scattering diffraction, Vickers hardness measurement and nano-indentation measurement. The following results were obtained: (1) The crystal structure of top dross particles Fe2Al5Znx having Fe: 37~38 wt%, Al: 44~45 wt% and Zn: 18~19 wt% belongs to the orthorhombic system with a lattice constant of a=7.61 Å, b=6.48 Å and c=4.23 Å. The a axis of Fe2Al5Znx becomes shorter, while the b and c axes become longer compared to those of binary Fe2Al5. (2) The top dross particles with the faceted interface were postulated to coarsen by the mechanism of the anisotropic interface energy between the top dross particles and molten Zn as a driving force rather than by the aggregation mechanism. (3) The hardness and the elastic modulus of the top dross particles are the lowest in the [001] direction like Fe2Al5, and are lower than those of Fe2Al5. (4) The fracture toughness of top dross particles is approximately 1.1 MPa·m1/2, which is slightly lower than that of Fe2Al5.