960MPa高强度钢材对接焊缝的低温断裂韧性

The Fracture Toughness of Butt Weld at Low Temperature of 960 MPa High-strength Steel

对14 mm厚的960 MPa结构钢材的对接焊缝进行了低温断裂韧性试验,采用三点弯曲试件,以裂纹尖端张开位移CTOD为指标,对960 MPa高强度钢材焊缝的断裂行为进行分析。计算出母材、焊缝区和热影响区的断裂韧性CTOD临界值δm与温度的关系,采用Boltzmann函数对其结果进行拟合分析,得到韧脆转变温度,并对其断裂微观机理进行分析。结果表明:断裂韧性CTOD临界值δm随温度降低呈下降趋势,与Q235、Q345、Q390及Q460相比,960 MPa高强度钢材的δm值最低,其焊接热影响区的δm值比焊缝金属和母材均小,其韧脆转变温度也较高(-12.45℃),低温冷脆特征更加显著。

A series of three point bending tests of 960 MPa high-strength steel at low temperature were carried out in the present study, five temperature points were selected for the tests, and the crack tip opening displacement was taken as the fracture toughness index. The fracture behavior of butt weld of 960 MPa steel were analyzed based on the experimental phenomenon, the relationship between frac- ture toughness and temperature was investigated and the test data were fitted by the Boltzmann func- tion, and the fracture micro mechanism was analyzed by electron microscope scanning. The results show that the variation trend of fracture toughness （critical CTOD values δm） is decline as temperature decreas- es, the δm values of 960 MPa steel are lower than that of Q235, Q345, Q390 and Q460 steels, and the values of the HAZ are lower than that for base material and weld metal, and the ductile-brittle transition temperature for HAZ（-12.45 ℃） is higher than that for base material and weld metal as well.