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.

Effect of Microstructure on High-Strength Low-Alloy Steel Welded Joint Toughness with Simulation of Heat-Affected Zone Coarse-Grained Area

Metallurgist ◽  
2021 ◽  
Vol 64 (9-10) ◽  
pp. 875-884
Author(s):  
K. G. Vorkachev ◽  
P. P. Stepanov ◽  
L. I. Éfron ◽  
M. M. Kantor ◽  
A. V. Chastukhin ◽  
...  
Keyword(s):  
Alloy Steel ◽  
Heat Affected Zone ◽  
Welded Joint ◽  
High Strength ◽  
Coarse Grained ◽  
Low Alloy Steel ◽  
Effect Of Microstructure

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.

Mechanical Behaviour of Intercritically Reheated Coarse-Grained Heat Affected Zone in High Strength Line Pipe Steels

2018 ◽  
Author(s):  
Madhumanti Mandal ◽  
Warren J. Poole ◽  
Thomas Garcin ◽  
Matthias Militzer ◽  
Laurie Collins
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Welding Process ◽  
Charpy Impact ◽  
High Strength ◽  
Coarse Grained ◽  
Fracture Mechanisms ◽  
Line Pipe ◽  
Secondary Cracks ◽  
The Impact

Multipass welding of high strength steels used for fabrication and joining of transmission pipelines presents a number of metallurgical challenges. A key concern is both the strength and toughness of the heat affected zone (HAZ) adjacent to both seam and girth welds. In this work, a systematic study has been conducted on regions of the heat affected zone in the base metal where the first welding pass produces a thermal excursion which results in a coarse-grained heat affected zone (CGHAZ). The subsequent weld pass involves intercritical annealing of this region, i.e. a microstructure associated with intercritically reheated coarse grain heat affected zone (ICCGHAZ). The small ICCGHAZ region is often identified as being particularly susceptible to crack initiation. This work was undertaken to understand microstructure development in this zone and how the ICCGHAZ may affect the overall performance of the HAZ. Gleeble thermomechanical simulations have been conducted to produce bulk samples representative of different welding scenarios. Charpy impact tests and tensile tests have been performed over a range of temperatures. It was found that when a continuous necklace of martensite-austenite islands form on the prior austenite grain boundaries (i.e. for a M/A fraction of ≈10%), the Charpy impact toughness energy is dramatically decreased and the ductile brittle transition temperature is significantly raised. Detailed studies on the secondary cracks have been conducted to examine the fracture mechanisms in the different microstructures. The results show that the lower bainite microstructures obtained after the 1st thermal treatment, representative of CGHAZ have excellent impact properties. The impact toughness of the microstructures typical of ICCGHAZ is strongly dependent on the composition as well as morphology and spatial distribution of the resulting martensite-austenite (M/A) islands transformed from inter-critically formed austenite. This zone can play a significant role in fracture initiation and thus needs to be considered in alloy and welding process designs.

scholarly journals Effect of Molybdenum on the Impact Toughness of Heat-Affected Zone in High-Strength Low-Alloy Steel

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1430
Author(s):  
Xiaoyan Wu ◽  
Pengcheng Xiao ◽  
Shujing Wu ◽  
Chunliang Yan ◽  
Xuegang Ma ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Alloy Steel ◽  
Heat Affected Zone ◽  
Laser Scanning ◽  
Lattice Misfit ◽  
High Strength ◽  
Optical Microscope ◽  
Low Alloy Steel ◽  
Number Density ◽  
The Impact

The microstructure, precipitates, and austenite grain in high-strength low-alloy steel were characterized by optical microscope, transmission electron microscope, and laser scanning confocal microscopy to investigate the effect of Mo on the toughness of steel. The microstructure was refined and the toughness was enhanced after the addition of 0.07% Mo in steel. The addition of Mo can suppress the Widmanstätten ferrite (WF) formation and promote the transformation of acicular ferrite (AF), leading to the fine transformed products in the heat-affected zone (HAZ). The chemical composition of precipitates changed from Nb(C, N) to (Nb, Mo)(C, N) because of the addition of Mo. The calculated lattice misfit between Nb(C, N) and ferrite was approximately 11.39%, while it was reduced to 5.40% for (Nb, Mo)(C, N), which significantly affected the size and number density of precipitates. A detailed analysis of the precipitates focusing on the chemical composition, size, and number density has been undertaken to understand the contribution of Mo on the improvement of steel toughness.

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.

Microstructure and Impact Toughness of High-Strength Low-Alloy Steel after Tempforming

2021 ◽  
Vol 122 (10) ◽  
pp. 1014-1022
Author(s):  
A. S. Dolzhenko ◽  
P. D. Dolzhenko ◽  
A. N. Belyakov ◽  
R. O. Kaibyshev
Keyword(s):  
Impact Toughness ◽  
Alloy Steel ◽  
High Strength ◽  
Low Alloy Steel
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