TiN-containing high-heat-input welding steels: Optimizing Ti/N ratio and precipitation temperature for enhanced low-temperature impact toughness in coarse-grained heat-affected zones
To enhance the low-temperature impact toughness of the coarse-grained heat-affected zone (CGHAZ) in high-heat-input welding steels, TiN-containing steels with tailored Ti and N contents were designed. The effects of Ti/N ratio and TiN precipitation temperature on particle stability, austenite grain...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-05-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425013201 |
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| Summary: | To enhance the low-temperature impact toughness of the coarse-grained heat-affected zone (CGHAZ) in high-heat-input welding steels, TiN-containing steels with tailored Ti and N contents were designed. The effects of Ti/N ratio and TiN precipitation temperature on particle stability, austenite grain refinement, microstructural evolution, and low-temperature impact toughness were systematically investigated through in situ observations via high-temperature confocal laser scanning microscopy, thermodynamic modeling, and scanning electron microscopy. The results demonstrate that elevating the TiN precipitation temperature within austenite while reducing the Ti/N ratio enhances TiN thermal stability, thereby refining austenite grains (minimum size: 79.9 μm) and improving CGHAZ toughness (peak value: 227 ± 12 J at 400 kJ/cm heat input). However, excessive precipitation temperatures induce coarse TiN particles (2–4 μm) via liquid-phase precipitation, while excessively low Ti/N ratios elevate free nitrogen levels, both of which degrade toughness by promoting cleavage fracture initiation. A critical ''ideal content region'' was identified, balancing TiN stability (precipitation temperature: 10–20 °C below solidus) and Ti/N ratio (2.0–2.5), which optimizes grain boundary pinning and minimizes embrittlement. |
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| ISSN: | 2238-7854 |