Effect of Heat Input on Impact Toughness of Coarse-Grained Heat-Affected Zone of a Nb-Ti Microalloyed Pipeline Steel

2012 ◽  
Vol 538-541 ◽  
pp. 2026-2031 ◽  
Author(s):  
Zhou Gao ◽  
Ran Wei ◽  
Kai Ming Wu
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Pipeline Steel ◽  
High Heat ◽  
Coarse Grained ◽  
Bainitic Microstructure ◽  
Homogenous Distribution ◽  
High Heat Input ◽  
The Impact

The effect of varying heat inputs (20, 100, 200 kJ/cm) on the microstructures and toughness of the simulated coarse-grained heat-affected zone of a Nb-Ti microalloyed pipeline steel were investigated utilizing optical and electron microscope. Results showed that the impact toughness of the coarse-grained heat-affected zone maintained a higher level at the heat input of 20 and 100 kJ/cm, whereas it dropped to a much lower level at the heat input of 200 kJ/cm. The good toughness was attributed to the grain refinement and the homogenous distribution of fine and elongated martensite/austenite constituents. The deterioration of toughness for high heat input simulated welding was mainly caused by the coarse bainitic microstructure and massive martensite/austenite constituents.

Effect of Welding Processes with High Heat Input on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone of a High-Strength High-Toughness Steel

2018 ◽  
Vol 937 ◽  
pp. 61-67
Author(s):  
Yu Jie Li ◽  
Jin Wei Lei ◽  
Xuan Wei Lei ◽  
Oleksandr Hress ◽  
Kai Ming Wu
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
High Strength ◽  
High Heat ◽  
Coarse Grained ◽  
Low Temperature Impact Toughness ◽  
The Impact ◽  
Welding Processes

Utilizing submerged arc welding under heat input 50 kJ/cm on 60 mm thick marine engineering structure plate F550, the effect of preheating and post welding heat treatment on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) has been investigated. The original microstructure of the steel plate is tempered martensite. The yield and tensile strength is 610 and 660 MPa, respectively. The impact absorbed energy at low temperature (-60 °C) at transverse direction reaches about 230~270 J. Welding results show that the preheating at 100 °C did not have obvious influence on the microstructure and toughness; whereas the tempering at 600 °C for 2.5 h after welding could significantly reduce the amount of M-A components in the coarse-grained heat-affected zone and thus improved the low temperature impact toughness.

Effect of Heat Input on Toughness of Coarse-Grained Heat-Affected Zone of an Ultra Low Carbon Acicular Ferrite Steel

2012 ◽  
Vol 538-541 ◽  
pp. 2003-2008 ◽  
Author(s):  
Zheng Hai Xia ◽  
Xiang Liang Wan ◽  
Xue Li Tao ◽  
Kai Ming Wu
Keyword(s):  
Electron Microscopy ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Acicular Ferrite ◽  
High Heat ◽  
Coarse Grained ◽  
Low Carbon ◽  
Ferrite Steel ◽  
The Impact

The effect of heat input on toughness of coarse-grained heat-affected zone of an ultra low carbon acicular ferrite steel were investigated when the welding was conducted with high heat input. Microstructural observations, energy dispersive X-ray spectroscopy analyses were conducted using optical microscopy, scanning electron microscopy and transmission electron microscopy, respectively. The microstructures of coarse-grained heat-affected zone consist of predominantly bainitic microstructure and a small proportion of acicular ferrite grains. The bainitic microstructures become coarsened with increasing heat input. The impact toughness of coarse-grained heat-affected zone remained at a higher level when the heat input ranged from 42 to 55 kJ/cm. It became not stable and dropped to a lower level when the heat input increased to 110150 kJ/cm. The enhancement in impact toughness was attributable to the MnS precipitation on the pre-formed Ti oxides as well as the formation of intragranular ferrite. When specimens were welded with higher heat input, the deterioration of impact toughness was caused by the coarsening of austenite grains.

Effects of oxygen content on microstructure and impact toughness of high heat input flux-cored wire weld metals

2018 ◽  
Vol 115 (4) ◽  
pp. 410
Author(s):  
Fengyu Song ◽  
Yanmei Li ◽  
Ping Wang ◽  
Fuxian Zhu
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Weld Metal ◽  
Oxygen Content ◽  
Heat Input ◽  
High Heat ◽  
Cored Wire ◽  
Weld Metals ◽  
High Heat Input ◽  
The Impact

Three weld metals with different oxygen contents were developed. The influence of oxygen contents on the microstructure and impact toughness of weld metal was investigated through high heat input welding tests. The results showed that a large number of fine inclusions were formed and distributed randomly in the weld metal with oxygen content of 500 ppm under the heat input condition of 341 kJ/cm. Substantial cross interlocked acicular ferritic grains were induced to generate in the vicinity of the inclusions, primarily leading to the high impact toughness at low temperature for the weld metal. With the increase of oxygen content, the number of fine inclusions distributed in the weld metal increased and the grain size of intragranular acicular ferrites decreased, which enhanced the impact toughness of the weld metal. Nevertheless, a further increase of oxygen content would contribute to a great diminution of the austenitic grain size. Following that the fraction of grain boundary and the start temperature of transformation increased, which facilitated the abundant formation of pro-eutectoid ferrites and resulted in a deteriorative impact toughness of the weld metal.

Impact Toughness Characteristics of SM570-TMC Steel Joint Using Welding Wire Containing 0.4% Nickel at Different Level of Heat Input

2020 ◽  
Vol 867 ◽  
pp. 117-124
Author(s):  
Herry Oktadinata ◽  
Winarto Winarto ◽  
Dedi Priadi ◽  
Eddy S. Siradj ◽  
Ario S. Baskoro
Keyword(s):  
Impact Toughness ◽  
Heat Input ◽  
High Heat ◽  
Optical Microscope ◽  
Butt Joint ◽  
Welding Wire ◽  
Steel Joint ◽  
Microstructure Observation ◽  
High Heat Input ◽  
The Impact

The study was conducted to evaluate the impact toughness of flux-cored arc welded of SM570-TMC steel joint under different heat inputs, 0.9 kJ/mm (low heat input) and 1.6 kJ/mm (high heat input). Welding wire containing 0.4%Ni was selected on this experiment. Multi-pass welds were performed on SM570-TMC steel plate of 16 mm in thickness with a single V-groove butt joint on flat position (1G). The evaluation consists of observations on microstructure using an optical microscope and SEM-EDS, and mechanical properties including tensile, microhardness Vickers and Charpy V-notch (CVN) impact test at temperatures of 25, 0 and-20 °C. Results showed that the impact toughness of the base metal (BM) was higher than the weld metal (WM) at all test temperatures. Hardness and impact toughness of WM at low heat input was observed higher than when applied a high heat input. The welded samples at low and high heat inputs had high of tensile strength, and the fracture seemly occurs on the BM. Microstructure observation showed that at a high heat input, larger grains and microsegregation were observed. It might affect on decreasing their impact property.

scholarly journals Effect of Ferritic Morphology on Yield Strength of CGHAZ in a Low Carbon Mo-V-N-Ti-B Steel

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1863
Author(s):  
Leping Wang ◽  
Huibing Fan ◽  
Genhao Shi ◽  
Qiuming Wang ◽  
Qingfeng Wang ◽  
...  
Keyword(s):  
Yield Strength ◽  
Heat Input ◽  
Low Carbon Steel ◽  
High Heat ◽  
Coarse Grained ◽  
Granular Bainite ◽  
Low Carbon ◽  
Fine Grained ◽  
High Heat Input ◽  
The Impact

For investigating the impact of ferritic morphology on yield strength (YS) of the high-heat-input welding induced coarse-grained heat-affected zone (CGHAZ) of a low carbon Mo-V-N-Ti-B steel, a group of particular welding heat inputs were designed to obtain different ferritic microstructures in CGHAZ. The tensile properties were estimated from typical samples with ferritic microstructures. The mixed microstructures dominated by the intragranular polygonal ferrite (IGPF), the intragranular acicular ferrite (IGAF), and the granular bainite (GB) were obtained at the heat inputs of 35, 65, 85 and 120 kJ/cm, respectively. When the main microstructure changed from IGPF to IGAF and GB, YS increased first and then decreased. The microstructure consisting mainly of IGAF possessed the maximum YS. As the main microstructure changed from IGPF to IGAF and GB, the contribution of grain refinement strengthening to YS was estimated to be elevated remarkably. This means the strength of CGHAZ in a low-carbon steel subjected to the high-heat-input welding could be enhanced by promoting the fine-grained AF and GB formation.

Investigation on the Weldability of a Zr-Ti Microalloyed Pipeline Steel X120

2012 ◽  
Vol 538-541 ◽  
pp. 1478-1483 ◽  
Author(s):  
Yu Qun Yin ◽  
Hong Hong Wang ◽  
Yong Kuan Yao ◽  
Li Li ◽  
Xuan Wei Lei ◽  
...  
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Room Temperature ◽  
Pipeline Steel ◽  
Coarse Grained ◽  
Fine Grained ◽  
Cycle Simulation ◽  
Welding Thermal Cycle ◽  
Temperature Impact

Welding thermal cycle simulation with the heat input of 12~25 kJ/cm and practical welding were undertaken to investigate the weldability of a Zr-Ti microalloyed pipeline steel X120. The microstructure in the simulated coarse-grained heat-affected zone was predominantly bainite. The Vickers hardness and room temperature impact toughness of simulated coarse-grained heat-affected zone is 276~297 (HV10) and 208~225 J, respectively. These results indicated that the X120 steel had good weldability. Practical plate welding with the heat input of 21 kJ/cm also showed that the Zr-Ti microalloyed pipeline steel X120 had high yeild strength (895 MPa) and low temperature (-30°C) impact toughness (183 J, 204 J and 208 J in the fusion line, coarse-grained heat-affected zone and fine-grained heat-affected zone, respectively).

scholarly journals Effects of Small Ni Addition on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone of High-Strength Low-Alloy Steel

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 718 ◽  
Author(s):  
Gang Huang ◽  
Xiangliang Wan ◽  
Kaiming Wu ◽  
Huazhong Zhao ◽  
Raja Misra
Keyword(s):  
Impact Toughness ◽  
Alloy Steel ◽  
Heat Affected Zone ◽  
High Strength ◽  
Coarse Grained ◽  
Low Alloy Steel ◽  
Ni Content ◽  
Ni Addition ◽  
Bainitic Microstructure ◽  
The Impact

The objective of the present study is to investigate the effects of nickel (Ni) on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steel. It was observed that the microstructure of CGHAZ predominantly consisted of bainite and a small proportion of martensite-austenite (M-A) constituents and acicular ferrite (AF). With increased Ni content, the percentage of M-A constituent decreased and AF increased; consequently, the impact toughness of CGHAZ increased. The study revealed that a small addition of nickel significantly affected the formation of M-A constituents and AF; however, no obvious influence was observed on the bainitic microstructure of high-strength low-alloy steel.

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