中文摘要：

随着钢板厚度的增加,焊接难度加大,且存在焊接裂纹缺陷的可能性也增大.为防止钢结构厚板焊接接头的脆性断裂,采用三点弯曲试样,以裂纹尖端张开位移（CTOD）为指标,对厚度为150mm的Q345B钢板对接焊缝低温下的断裂韧性进行试验研究.分析了焊缝金属和热影响区断裂韧性CTOD值δm随温度的变化关系,并用Boltzmann函数对断裂韧性-温度曲线进行拟合,结合试样断口的扫描电镜图分析了断裂的微观机理.试验结果表明：焊缝金属和热影响区的CTOD值δm随温度的降低而降低,从20℃～-60℃,降幅分别达78%和91%;热影响区CTOD值δm比焊缝金属和母材均要小.试验积累了厚板对接焊缝的断裂韧性数据,为低温地区钢结构厚板对接焊缝脆性断裂的预防提供了技术基础.

英文摘要：

To prevent brittle fractures in thick plate steel structures,the fracture toughness of butt welded joints fabricated from 150 mm thick Q345B steel plates were tested at low temperature by three-point bending specimens and crack tip opening displacement（CTOD） was applied as a fracture toughness index.The relationships between fracture toughness CTOD δm and temperature for weld metal and heat affected zone（HAZ） were analyzed through Boltzmann curve fitting from toughness versus temperature data.Furthermore,the fracture mechanism of the tested specimens were investigated with scanning electron micrographs.The test results indicated that the fracture toughness CTOD values δm for weld metal and HAZ reduced as the temperature decreased.From 20 ℃ to-60 ℃,the CTOD values δm for weld metal and HAZ reduced by 78% and 91%,respectively.Compared to the base metal and weld metal,the CTOD values δm for HAZ were much lower.In this study,rich experimental data were collected for fracture toughness of thick plate butt weld,so as to form the technical basis for preventing brittle fracture of thick plate steel structures in cold regions.