Effect of Welding Heat Input on Microstructure and Impact Toughness in the Simulated CGHAZ of Low Carbon Mo-V-Ti-N-B Steel

Qiao, Mingliang; Fan, Huibing; Shi, Genhao; Wang, Leping; Wang, Qingfeng; Liu, Riping

doi:10.3390/met11121997

Cited by 5 publications

(4 citation statements)

References 37 publications

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“…The morphologies of the fiber and radiation zones were also observed at high magnification. With the increase in E j , the shape of the dimples in the fiber zone change from small, round, and deep to large, shallow, and parabolic, indicating a decrease in the degree of plastic deformation in this zone [14,32]. In the radiation zone, with the increase in E j , the size of the cleavage surface gradually increases.…”

Section: Effect Of E J On the Impact Fracture Characteristicsmentioning

confidence: 98%

“…However, the atmospheric corrosion resistant electrodes contain more Si [8,9], Cr [10], and other alloy elements, and it is easy to form coarse granular bainitic ferrite (GBF) and more hard phase martensite/ austenite (M/A) constituents during the phase transition process [11,12]. It has been widely established that the microstructure of this brittle hard phase is closely related to welding heat input (E j ) or high-temperature residence time [13,14]. To ensure good welding efficiency and toughness of joints, appropriate limits of welding E j are generally specified for the welding of steel structures [15].…”

Section: Introductionmentioning

confidence: 99%

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Effect of heat input on the microstructure and impact toughness of submerged arc weld metal for high-performance weathering steel

Li,

et al. 2023

Mater. Res. Express

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This study aims to elucidate the appropriate heat input (Ej) range for submerged arc welding (SAW) of high-performance weathering steel. Generally, by increasing Ej, the welding efficiency can be improved, but the toughness of the weld metal may be deteriorated. Therefore, SAW was employed to produce the weld microstructure under varying Ej from 20 to 50 kJ/cm. The Charpy V-notch impact tests were conducted at −40℃, and the weld microstructures were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The results indicate that the weld microstructures consist of polygonal ferrite (PF), acicular ferrite (AF), granular bainitic ferrite (GBF), and martensite/austenite (M/A) constituents under each Ej. With the increase in Ej, the proportion of PF increases, while AF and GBF are coarsened, and the area fraction (fM/A) and mean size (dM/A) of M/A constituents increase monotonically. Further, the fraction (fMTA>15°) of high-angle grain boundaries (HAGBs) with the misorientation tolerance angles (MTAs) greater than 15° is reduced, while the mean equivalent diameter (MEDMTA≥15°) of ferrite grains with HAGBs increases. Accordingly, with the increase in Ej, the impact toughness of weld degrades from 128.4 to 47.6 J. The higher degree of micro-strain concentration caused by the increase in M/A size and area leads to the formation of larger microcracks under small plastic deformation, while the reduced HAGBs have a lower inhibition effect on crack propagation. Finally, the impact toughness decreases with the increase of Ej. Overall, the findings suggest that the Ej of SAW should not exceed 40 kJ/cm in the construction of high-performance weathering steel.

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Section: Effect Of E J On the Impact Fracture Characteristicsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Effect of heat input on the microstructure and impact toughness of submerged arc weld metal for high-performance weathering steel

Li,

et al. 2023

Mater. Res. Express

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“…Researchers have proposed many ways to improve the properties of the heat-affected zone of high heat input welding steel in order to improve welding efficiency and obtain excellent HAZ properties. For example, under the premise of low-carbon-equivalent alloy design [8][9][10], combined oxide metallurgy technology [11], Ti-B technology [12], TiN technology [13], etc., have been suggested. As the control of TiN particles is relatively stable, it has been widely used in industrial production.…”

Section: Introductionmentioning

confidence: 99%

Effects of Ti/N Ratio on Coarse-Grain Heat-Affected Zone Microstructure Evolution and Low-Temperature Impact Toughness of High Heat Input Welding Steel

Liu,

Wang,

et al. 2023

Coatings

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Coarse-grain heat-affected zone (CGHAZ) properties of steel deteriorate when it is welded using high heat input, which always restricts the promotion and use of high heat input welding steel. TiN particles significantly inhibit the growth of austenite and improve the microstructure and properties of high heat input welding steel. Effects of different Ti/N ratios on the CGHAZ microstructure and properties of high heat input welding steel were studied using welding thermal simulations and in situ observations. Results showed that a higher Ti/N ratio led to the abnormal growth of austenite grains and promoted the nucleation and growth of lath ferrite, which made the microstructure of the CGHAZ heterogeneous. In contrast, austenite grains were more uniform at a lower Ti/N ratio. Thus, the microstructure was refined, the brittle structure was reduced, and the properties of the CGHAZ were improved. In addition, when Ti/N = 5.85, the impact absorption energy of the CGHAZ obviously fluctuated. However, when Ti/N = 2.82, the impact absorption energy of the CGHAZ was higher and more stable. These results provided a new idea for the development of high heat input welding steel based on TiN theory.

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“…Compared to single-wire submerged arc welding (20 kJ/cm ≤ heat input ≤ 50 kJ/cm), the heat input (E j ) of double-wire submerged arc welding (heat input ≥ 50 kJ/cm) has a large amount of deposited metal per unit time, which can significantly save production time and cost and reduce the labor intensity of workers. However, with higher E j , severe coarsening of the microstructure occurs, which deteriorates the mechanical properties of weld metal [2,3]. The weld metal composed of a large amount of acicular ferrite (AF) has a higher impact toughness due to a higher proportion of high-angle grain boundaries (HAGBs) and a precise interlocking structure [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Influence of Heat Input on the Microstructure and Impact Toughness in Weld Metal by High-Efficiency Submerged Arc Welding

Zhao

et al. 2023

Metals

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The development of high-efficiency multi-wire submerged arc welding technology in bridge engineering has been limited due to the high mechanical performance standards required. In this paper, weld metal was obtained by welding at three different high heat inputs with the laboratory-developed high-efficiency submerged arc welding wire for bridges. The effect of changing different high heat inputs on the microstructure and impact toughness of high efficiency submerged arc weld metal was systematically investigated by cutting and Charpy V-notch impact tests at −40 °C, using optical microscopy, scanning electron microscopy, energy-dispersive electron spectroscopy, electron backscatter diffraction, and transmission electron microscopy to characterize and analyze. With the increase in heat input from 50 kJ/cm to 100 kJ/cm, the impact absorption energy decreased significantly from 130 J to 38 J. The number of inclusions in the weld metal significantly decreased and the size increased, which led to a significant decrease in the number of inclusions that effectively promote acicular ferrite nucleation, further leading to a decrease in the proportion of acicular ferrite in the weld metal. At the same time, the microstructure of the weld metal was significantly coarsened, the percentage of high-angle grain boundaries was decreased, and the size of martensite/austenite constituents was significantly increased monotonically. The crack initiation energy was reduced by the coarsened martensite/austenite constituents and inclusions, which produced larger local stress concentrations, and the crack propagation was easier due to the coarsened microstructure and lower critical stress for crack instability propagation. The martensite/austenite constituents and inclusions in large sizes worked together to cause premature cleavage fracture of the impact specimen, which significantly deteriorated the impact toughness. The heat input should not exceed 75 kJ/cm for high-efficiency submerged arc welding wires for bridges.

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Effect of Welding Heat Input on Microstructure and Impact Toughness in the Simulated CGHAZ of Low Carbon Mo-V-Ti-N-B Steel

Cited by 5 publications

References 37 publications

Effect of heat input on the microstructure and impact toughness of submerged arc weld metal for high-performance weathering steel

Effect of heat input on the microstructure and impact toughness of submerged arc weld metal for high-performance weathering steel

Effects of Ti/N Ratio on Coarse-Grain Heat-Affected Zone Microstructure Evolution and Low-Temperature Impact Toughness of High Heat Input Welding Steel

Influence of Heat Input on the Microstructure and Impact Toughness in Weld Metal by High-Efficiency Submerged Arc Welding

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