Influence of gas atmosphere dew point on the selective oxidation and the reactive wetting during hot dip galvanizing of CMnSi TRIP steel
SCIE
SCOPUS
- Title
- Influence of gas atmosphere dew point on the selective oxidation and the reactive wetting during hot dip galvanizing of CMnSi TRIP steel
- Authors
- Lawrence Cho; Seok-Jae Lee; Myung-Soo Kim; Young Ha Kim; De Cooman, BC
- Date Issued
- 2013-01
- Publisher
- SPRINGER
- Abstract
- The selective oxidation and reactive wetting of intercritically annealed Si-bearing CMnSi transformation-induced plasticity steels were investigated by high-resolution transmission electron microscopy. In a N-2 + 10 pct H-2 gas atmosphere with a dew point (DP) ranging from 213 K to 278 K (-60 degrees C to 5 degrees C), a continuous layer of selective oxides was formed on the surface. Annealing in a higher DP gas atmosphere resulted in a thinner layer of external oxidation and a greater depth of internal oxidation. The hot dipping was carried out in a Zn bath containing 0.22 mass pct Al, and the bath temperature was 733 K (460 degrees C). Coarse and discontinuous Fe2Al5-xZnx grains and Fe-Zn intermetallics (zeta and delta) were observed at the steel/coating interface after the hot dip galvanizing (HDG) of panels were annealed in a low DP atmosphere 213 K (-60 degrees C). The Fe-Zn intermetallics were formed both in areas where the Fe2Al5-xZnx inhibition layer had not been formed and on top of non-stoichiometric Fe-Al-Zn crystals. Poor wetting was observed on panels annealed in a low DP atmosphere because of the formation of thick film-type oxides on the surface. After annealing in higher DP gas atmospheres, i.e., 263 K and 278 K (-10 degrees C and 5 degrees C), a continuous and fine-grained Fe2Al5-xZnx layer was formed. No Fe-Zn intermetallics were formed. The small grain size of the inhibition layer was attributed to the nucleation of the Fe2Al5-xZnx grains on small ferrite sub-surface grains and the presence of granular surface oxides. A high DP atmosphere can therefore significantly contribute to the decrease of Zn-coating defects on CMnSi TRIP steels processed in HDG lines. DOI: 10.1007/s11661-012-1392-1 (C) The Minerals, Metals & Materials Society and ASM International 2012
- Keywords
- TRANSFORMATION-INDUCED PLASTICITY; HIGH-STRENGTH STEELS; INTERNAL OXIDATION; SURFACE; ALLOYS
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/13133
- DOI
- 10.1007/S11661-012-1392-1
- ISSN
- 1073-5623
- Article Type
- Article
- Citation
- METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, vol. 44A, no. 1, page. 362 - 371, 2013-01
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