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

作者：Junjie Hao, Chao Sheng Wang, Hua Duan, Yan Ping Zhu, Guo Yuan, Guodong Wang · 发表于：Journal of Materials Research and Technology · 年份：2025 · DOI：10.1016/j.jmrt.2025.05.164 · 被引用次数：10 · 研究领域：Microstructure and Mechanical Properties of Steels、Metal Alloys Wear and Properties、Metal and Thin Film Mechanics

ABSTRACT 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.