Cleavage initiation in Ti microalloyed steels
- Ohio State Univ., Columbus, OH (United States)
The toughness of two microalloyed, thermomechanical control process steels were investigated (steels A and B). Steel A was microalloyed with 0.076V, 0.028Nb, and 0.011 Ti, while steel B contained 0.048Ti. Coarse grain heat affected zone (CGHAZ) specimens were produced by Gleeble simulation. Toughness was measured using instrumented precracked Charpy, Charpy-V-notch, and double crack, 4-point bend tests. Optical and scanning electron microscopy were used for microstructural and fractographic analysis. In all cases, steel A showed better cleavage resistance than steel B. SEM fractography revealed no distinct features at the initiation sites of steel A. At the initiation sites of steel B, however, TiN inclusions were consistently found; their existence verified by EDS. Without exception, when a TiN related initiation site was located, a piece of TiN was found in each mating fracture surface. Evidence of matching river patterns within the inclusion halves, frequent sidecracks within the inclusions, and the absence of microvoiding established the cleavage initiation mechanism in steel B as the fracturing of brittle TiN particles. By quantitative microscopy it was estimated that about 0.0016wt% of steel B`s Ti (less than 3.5% of the total) was tied up in the TiN inclusions. This indicates that, depending on casting schedule, TiN related toughness degradation could potentially occur in steels with modest Ti content.
- OSTI ID:
- 234248
- Report Number(s):
- CONF-951026-; ISBN 0-87170-555-9; TRN: IM9624%%289
- Resource Relation:
- Conference: Materials Week `95, Cleveland, OH (United States), 29 Oct - 2 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of High performance structural steels: 1995 conference proceedings; Asfahani, R. [ed.]; PB: 321 p.
- Country of Publication:
- United States
- Language:
- English
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