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.

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

Improvement on Toughness of Weld Heat Affected Zone of Cu-Containing Low Alloy Steel of Long Scale Forging for Offshore Applications by Optimizing Chemical Composition

2019 ◽  
Author(s):  
Yuta Honma ◽  
Gen Sasaki ◽  
Kunihiko Hashi ◽  
Fumiyoshi Minami
Keyword(s):  
Chemical Composition ◽  
Alloy Steel ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Low Alloy Steel ◽  
Crack Tip Opening Displacement ◽  
Welding Condition ◽  
Input Condition ◽  
Haz Toughness ◽  
Weld Heat

Abstract Copper-containing low alloy steel based on ASTM A707 5L grade is widely used for structural parts of offshore wells. Applications of the steel for Ultra-deepwater development require excellent low temperature toughness from the viewpoint of marine accident prevention. However it is difficult to stably obtain good weld joint toughness because the welding condition is inevitably scattering. With those backgrounds, this paper focuses on metallurgical factors controlling the HAZ toughness of A707 modified steel. Potential factors considered are the grain size, M-A and precipitates. A challenge is demonstrated to improve the HAZ toughness by optimizing the Cu and Mn contents. In this study, we investigated mechanical properties including crack tip opening displacement (CTOD) and we observed microstructure using welding tests or various weld heat cycle specimens. The weld heat affected zone (HAZ) of a conventional material had good toughness for the low heat input condition. However it was remarkably decreased for the high heat input condition due to the precipitating martensite-austenite constituent (M-A) in local brittle zones (LBZ). The weld test results indicated the importance of suppressing the formation of M-A in order to improve toughness in the HAZ of the steel. Thereby, we challenged the optimization of chemical composition for HAZ toughness improvement. Cu had no bad influence on the HAZ toughness. It was demonstrated that the HAZ toughness is recovered by good use of Cu precipitates in SC cycle. Moreover the area fraction of M-A is decreased in keeping with Mn content, which leads to the improvement of the ICCG HAZ toughness. Based on our study, the recommended amounts of Cu and Mn are more than 1.0 mass% and less than 0.6 mass%, respectively, to ensure the HAZ toughness, especially ICCG HAZ toughness.

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