Abstract
Toughness of the coarse-grained-heat-affected-zone (CGHAZ) strongly depends on the prior austenite grain size. The prior austenite grain size is affected not only by chemical composition, thermal cycle, and dissolution of second-phase particles, but also by the initial microstructure. The effect of base metal microstructure (ferrite/pearlite obtained by air cooling and martensite obtained by water-quenching) on Charpy impact toughness of the CGHAZ has been investigated for different heat inputs for high-heat input welding of a microalloyed steel. A welding thermal cycle with a heat input of 100 kJ/cm and 400 kJ/cm were simulated on the MMS-300 system. Despite a similar microstructure in the CGHAZ of both the base metals, the average Charpy impact energy for the air-cooled base metal was found to be higher than the water-quenched base metal. Through thermo-kinetic simulations, it was found that a higher enrichment of Mn/C at the ferrite/austenite transformation interface of the CGHAZ of water-quenched base metal resulted in stabilizing austenite at a lower A1 temperature, which resulted in a coarser austenite grain size and eventually lowering the toughness of the CGHAZ.
Original language | English |
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Article number | 4760 |
Journal | Materials |
Volume | 14 |
Issue number | 16 |
DOIs | |
State | Published - Aug 2 2021 |
Funding
Acknowledgments: Minghao Shi gratefully acknowledges the financial support from the China Scholarship Council.
Funders | Funder number |
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China Scholarship Council |
Keywords
- Charpy impact toughness
- Coarse-grained heat-affected zone
- Grain boundary ferrite
- Initial microstructure
- Prior austenite grain size