Influence of the Oxidation-Reduction Process on the Surface and Sub-surface Microstructure of Intercritically Annealed CMnSi TRIP Steel
SCIE
SCOPUS
- Title
- Influence of the Oxidation-Reduction Process on the Surface and Sub-surface Microstructure of Intercritically Annealed CMnSi TRIP Steel
- Authors
- Gong, YF; De Cooman, BC
- Date Issued
- 2011-01
- Publisher
- IRON STEEL INST JAPAN KEIDANREN KAIKAN
- Abstract
- The surface and sub-surface of an intercritically annealed Si-bearing CMnSi TRIP steel were investigated by high resolution transmission electron microscopy after pre-oxidation in a N-2+0.3 vol-% O-2 atmosphere and subsequent reduction in a N-2+10 Vol-% H-2 atmosphere. After the initial pre-oxidation the surface consisted of areas covered with a thick Fe3O4 oxide with an open porous structure and areas covered with a thin compact Fe3O4 film connected to the steel by xMnO.SiO2 oxide bridges connecting the oxide film to the matrix. Both porous and compact oxide contained embedded grains of MnO. A grain boundary network of amorphous SiO2 was formed in the steel subsurface under the porous Fe3O4 after the pre-oxidation treatment. No internal oxidation was observed below the compact Fe3O4 layer. Whereas, the Fe3O4 was fully reduced to metallic Fe after reduction annealing, the selective oxides MnO, c-xMnO.SiO2 (x>1) and a-xMnO.SiO2 (x<0.9) were unaffected by the reduction annealing. As no amorphous a-SiO2 or a-xMnO.SiO2 (x<0.9) film forming oxides were present at the surface of the Si-bearing TRIP steel after the pre-oxidation and reduction annealing, the treatment is believed to lead to an improved wettability of the surface by liquid Zn during hot dip galvanizing and Zn-coatings which are free of bare spot defects. Zn-coating adhesion problems may however arise from the formation of large pores at the Fe3O4/steel interface, which are still present after the oxide reduction.
- Keywords
- TRIP steel; oxidation-reduction; hot dip galvanizing; INTERNAL OXIDATION; HIGH-TEMPERATURES; ALLOYS; CARBON; IRON; DIFFUSION; MAGNETITE; OXIDES
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/17440
- DOI
- 10.2355/isijinternational.51.630
- ISSN
- 0915-1559
- Article Type
- Article
- Citation
- ISIJ INTERNATIONAL, vol. 51, no. 4, page. 630 - 637, 2011-01
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- There are no files associated with this item.
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