Microstructures of Heat-Affected Zone in Niobium Containing Steels
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- Yang J. R.
- Institute of Materials Science and Engineering, National Taiwan University
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- Huang C. Y.
- Institute of Materials Science and Engineering, National Taiwan University
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- Chiou C. S.
- Institute of Materials Science and Engineering, National Taiwan University
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Abstract
In order to understand the effect of niobium additions on the microstructures of the HAZ (heat-affected zone) in mild steels, a plain C-Mn steel (without niobium content) and three niobium containing steels with 0.01, 0.02 and 0.04 mass%Nb, respectively were investigated through simulated HAZ experiments with the heat inputs of 2×106, 5×106 and 8×106 J/m. The microstructures of simulated coarse-grained HAZ have been examined by optical metallography and transmission electron microscopy. It was found that the addition of niobium had a significant effect on the transformation. For high energy heat inputs (8×106 and 5×106 J/m), the additions of niobium evidently retarded the pearlite formation even in the case of 0.01 mass%Nb containing steel; the microstructures of coarse-grained HAZ of niobiumcontaining steels consisted mainly of secondary Widmanstätten ferrite, but that of the niobium-free steel comprised a large amount of pearlite besides secondary Widmanstätten ferrite. In the condition of low energy heat input (2×106 J/m), the microstructures of coarse-grained HAZ of niobium-containing steels were all similar and consisted mainly of interlocking ferrite plates with small amounts of bainite and Widmanstätten ferrite; while that of the niobium-free steel comprised Widmanstätten ferrite and martensite with a small quantity of pearlite. The results from Charpy impact test indicated that the niobium-containing steels treated with the heat input 2×106 J/m could possess higher toughness than those treated with the heat inputs of 5×106 and 8×106 J/m. It is proposed that the interlocking ferrite structure, which forms in niobium-containing steels under 2×106 J/m heat input, improves the toughness property.
Journal
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- Materials Transactions, JIM
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Materials Transactions, JIM 40 (3), 199-208, 1999
The Japan Institute of Metals
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Details 詳細情報について
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- CRID
- 1390282679225304704
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- NII Article ID
- 130003422593
- 10003805764
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- NII Book ID
- AA10699969
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- COI
- 1:CAS:528:DyaK1MXjsFWqu70%3D
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- ISSN
- 2432471X
- 09161821
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- NDL BIB ID
- 4689660
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- Text Lang
- en
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- Data Source
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- JaLC
- NDL
- Crossref
- CiNii Articles
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- Abstract License Flag
- Disallowed