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

作　　者：杨秀芝 张李超 史玉升 YU Shengfu DONG Chunfa HUA Wenlin LI Xuan 

机构地区：[1]State Key Laboratory 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, Huangshi 435003, China [3]Institute of Mechanical Engineering, Wuhan Textile University, Wuhan 430073,China

出　　处：《Journal of Wuhan University of Technology(Materials Science)》2018年第1期177-184,共8页武汉理工大学学报（材料科学英文版）

基　　金：Supported by the National 863 Program of China(No.2015AA042505);State Key Laboratory of Materials Processing and Die&Mould Technology of Huazhong University of Science and Technology(No.P2018-014);Major Science and Technology Project in Guangdong Province(No.2014B010130001)

摘　　要：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.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.

关 键 词：heat affected zone （HAZ） impact toughness EBSD BAINITE 

分 类 号：TG142.1[一般工业技术—材料科学与工程]