Effect of high heat input welding on the microstructures, precipitates and mechanical properties in the simulated coarse grained heat affected zone of a low carbon Nb-V-Ti-N microalloyed steel

Zhang, Jing; Xin, Wenbin; Ge, Ziwei; Luo, Guoping; Peng, Jun

doi:10.1016/j.matchar.2023.112849

Cited by 15 publications

(10 citation statements)

References 52 publications

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“…Previous studies have shown that the microstructural transformations during the welding process influence the microstructure of the HAZ, especially within the CGHAZ, consequently affecting its low-temperature impact toughness [25][26][27]. In this study, the low-temperature impact toughness obtained in the CGHAZs of Steel 1, 2 and 3 are quite different, which should be influenced by the difference in microstructures.…”

Section: Hardness Of the Simulated Cghazmentioning

confidence: 65%

Effect of Pre-Weld Heat Treatment on the Microstructure and Properties of Coarse-Grained Heat-Affected Zone of a Wind Power Steel after Simulated Welding

Wang,

Shang

2024

Metals

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The effect of pre-weld heat treatment on the microstructure and low-temperature impact toughness of the coarse-grained heat-affected zone (CGHAZ) after simulated welding was systematically investigated through the utilization of scanning electron microscopy (SEM) and electron back-scattering diffraction (EBSD). The Charpy impact test validated the presence of an optimal pre-weld heat treatment condition, resulting in the highest impact toughness observed in the CGHAZ. Three temperatures for pre-weld heat treatment (690, 720 and 750 °C) were used to obtain three different matrices (Steel 1, Steel 2, Steel 3) for simulated welding. The optimal pre-weld heat treatment is 720 °C for 15 min followed by water quench. Microstructure characterization showed that there is an evident microstructure comprising bainite (B) in Steel 1 and Steel 2 after pre-weld heat treatment, while the addition of martensite (M) with the pre-weld heat treatment temperature exceeds Ac1 by almost 60 °C (Steel 3). These differences in microstructures obtained from pre-weld heat treatment influence the refinement of high-temperature austenite during subsequent simulated welding reheating processes, resulting in distinct microstructural characteristics in the CGHAZ. After the optimal pre-weld heat treatment, Steel 2 subjected to single-pass welding thermal simulation demonstrates a refined microstructure characterized by a high density of high-angle grain boundaries (HAGBs) within the CGHAZ, particularly evident in block boundaries. These boundaries effectively prevent the propagation of brittle cracks, thereby enhancing the impact toughness.

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Section: Hardness Of the Simulated Cghazmentioning

confidence: 65%

Effect of Pre-Weld Heat Treatment on the Microstructure and Properties of Coarse-Grained Heat-Affected Zone of a Wind Power Steel after Simulated Welding

Wang,

Shang

2024

Metals

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“…Consequently, this leads to a rapid decline in the ferrite nucleation sites and a significant increase in bainite transformation. [36] During the bainite transformation, bainite laths usually grew from the PAGB to the interior of grains, and the newly formed laths cannot propagate across these PAGB, [37] which indicates that there is a positive relationship between bainite grain size and size of prior austenite grain. Consequently, compared to S810 steel, S910 and S1010 steels exhibit greater average grain size.…”

Section: Microstructural Evolution Characteristicsmentioning

confidence: 99%

The Low‐Temperature Toughness Improvement of High‐Strength Low‐Alloy Steel Due to the Microstructural Changes Caused by the Reheating/Rolling Temperature

Liu,

Zhao,

Tian

et al. 2024

steel research int.

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Herein, the microstructure, low‐temperature toughness, and fracture characteristics of high‐strength low‐alloy (HSLA) steel prepared by various thermomechanical control processes are systematically studied. Three different reheating/rolling temperatures are designed to obtain microstructures with different prior austenite grain sizes: 20.12 μm (S810), 27.58 μm (S910), and 35.19 μm (S1010). After hot rolling, S810 steel with smaller prior austenite grain size can provide high‐density deformed grain boundaries that promote ferrite phase transformation. The S910 and S1010 steels predominantly undergo bainite transformation as the prior austenite grain size and rolling temperature increase. Also, excellent low‐temperature toughness is obtained by reducing the reheating/rolling temperature (i.e., S810 steel), reflecting that Charpy impact energy of the core of the steel plate is 118.53 J at −120 °C. High performances is mainly attributed to the higher ferrite content, grain refinement, lower dislocation density, and higher proportion of high‐angle grain boundaries. Furthermore, fracture morphology analysis demonstrates that the S810 steel exhibits ductile fracture and noticeable plastic deformation at −120 °C, while S910 and S1010 steels exhibit brittle fracture and rapid crack propagation. These findings manifest the applicability of the suggested technique in preparing HSLA steel with excellent low‐temperature toughness.

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“…Among them, the coarse-grained heat-affected zone (CGHAZ) is the region always showing the worst toughness because of the formation of coarse austenite grains and undesirable microstructure [5][6][7]. Previous studies [4,[8][9][10][11][12] have extensively investigated the effects of welding heat input, cooling rate, alloy composition, post-weld heat treatment and other parameters on the microstructure and properties of the weld joint. However, a recent study [13] has also found that segregation in steel plates can also affect the microstructure and mechanical properties of high-strength steel before and after welding.…”

Section: Introductionmentioning

confidence: 99%

Effect of Segregation Band on the Microstructure and Properties of a Wind Power Steel before and after Simulated Welding

Wang,

Liu

et al. 2024

Metals

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This article uses scanning electron microscopy (SEM) and electron back-scattering diffraction (EBSD) to study the effect of C and Mn segregation on the microstructure and mechanical properties of high-strength steel with 20 mm thickness used for wind power before and after simulated welding. A Gleeble-3500 (GTC, Dynamic Systems Inc., Poestenkill, NY, USA) was used to study the microstructure evolution of the simulated coarse-grained heat-affected zone (CGHAZ) of experimental steel under different welding heat inputs (10, 14, 20, 30 and 50 kJ/cm) and its relationship with low-temperature impact toughness (−60 °C). The results indicate that alloy element segregation, especially Mn segregation, significantly affects the impact toughness scatter of the steel matrix, as it induces the formation of low-temperature martensite or hard phase, such as M/A (martensite/austenite) constituent. In addition, segregation also reduces the low-temperature impact toughness of the simulated welding samples and increases the fluctuation range. For high-strength steel with yield strength higher than 460 MPa used for wind power generation, there is an optimal welding heat input (~20 kJ/cm), which enables the simulated coarse-grained heat-affected zone (CGHAZ) to obtain the highest impact toughness due to the formation of lath bainite (LB) and the finest crystallographic block units. Excessive or insufficient heat input can induce the formation of coarse granular bainite (GB) or lath martensite (LM), leading to a larger size of crystallographic block units, reducing the hindering effect of brittle crack propagation and deteriorating low-temperature impact toughness.

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Effect of high heat input welding on the microstructures, precipitates and mechanical properties in the simulated coarse grained heat affected zone of a low carbon Nb-V-Ti-N microalloyed steel

Cited by 15 publications

References 52 publications

Effect of Pre-Weld Heat Treatment on the Microstructure and Properties of Coarse-Grained Heat-Affected Zone of a Wind Power Steel after Simulated Welding

Effect of Pre-Weld Heat Treatment on the Microstructure and Properties of Coarse-Grained Heat-Affected Zone of a Wind Power Steel after Simulated Welding

The Low‐Temperature Toughness Improvement of High‐Strength Low‐Alloy Steel Due to the Microstructural Changes Caused by the Reheating/Rolling Temperature

Effect of Segregation Band on the Microstructure and Properties of a Wind Power Steel before and after Simulated Welding

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