Effective Microstructure Unit in Control of Impact Toughness in CGHAZ for High Strength Bridge Steel

The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope（OM）, scanning electron microscope（SEM）, electron backscattering diffr...

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Published inJournal of Wuhan University of Technology. Materials science edition Vol. 33; no. 1; pp. 177 - 184
Main Author 杨秀芝;张李超;史玉升;YU Shengfu;DONG Chunfa;HUA Wenlin;LI Xuan
Format Journal Article
LanguageEnglish
Published Wuhan Wuhan University of Technology 01.02.2018
Springer Nature B.V
Subjects
Bainite
CGHAZ;微观结构;扫描电子显微镜;控制;钢;热输入;EBSD;SEM
Chemistry and Materials Science
Cleavage
Crack propagation
Electron backscatter diffraction
Electron microscopes
Electrons
Fracture surfaces
Fracture toughness
Grain refinement
Heat affected zone
High strength
Impact strength
Materials Science
Microstructure
bainite
heat affected zone (HAZ)
impact toughness
EBSD
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Summary:The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope（OM）, scanning electron microscope（SEM）, electron backscattering diffraction（EBSD） and transmission electron microscope（TEM）, and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. With decreasing heat input, both bainite packet and block are significantly refined, and the toughness has an increasing tendency due to the grain refinement. The fracture surfaces all present cleavage or fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of high strength bridge steel.
Bibliography:YANG Xiuzhi1,2, ZHANG Lichao1, Sill Yusheng1, YIU Shengfi1, DONG Chunfa2, HUA Weulin2, LI Xuan3 （1. State Key Laboratoly of Materials Processing and Die ＆ Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; 2. Institute of Mechanical Engineering, Hubei Polytechnic University, ttuangshi 435003, China; 3. Institute of Mechanical Engineering, Wuhan Textile University, Wuhan 430073, China）
42-1680/TB
heat affected zone （HAZ）; impact toughness; EBSD; bainite
The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope（OM）, scanning electron microscope（SEM）, electron backscattering diffraction（EBSD） and transmission electron microscope（TEM）, and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. With decreasing heat input, both bainite packet and block are significantly refined, and the toughness has an increasing tendency due to the grain refinement. The fracture surfaces all present cleavage or fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of high strength bridge steel.
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
ISSN:1000-2413
1993-0437
DOI:10.1007/s11595-018-1803-2