Q690D钢材十字形焊接接头高温后的断裂破坏试验研究

为研究Q690D高强度钢材及焊缝连接件在常温和高温后的断裂性能,选取代表实际梁柱节点局部焊接构造的十字形焊接节点试样,完成了常温和一系列高温后Q690D钢材和ER80-G焊缝金属的单轴拉伸试验,得到了钢材和焊缝金属在不同高温后的弹性模量、屈服强度、极限强度和延伸率.开展了常温和高温后十字形焊接接头的单调拉伸试验和超低周...

Experimental Research on Post-fire Fracture Failure of Q690D Steel Cross-shaped Welded Joints

In order to study the fracture properties of Q690D high strength steel and welded joints at room temperature and after high temperature, the cross-shaped welded joints representing the actual local welding structure of the beam-to-column joints were selected, and a series of uniaxial tensile tests of Q690D steel and ER80-G weld metal at room temperature and after high temperature were conducted. The elastic modulus, yield strength, ultimate strength and elongation of steel and weld metal after high temperatures were obtained. The cross-shaped welded joints at room temperature and after high temperature were tested under monotonic loading and ultra low cyclic loading. The fracture mechanism of Q690D high strength welded joints was analyzed while the effect of post-fire temperature and loading condition on the fracture behavior of steel and welded joints was discussed. The results show that when the temperature is higher than 600 ℃, the post-fire strength of steel and welded joints decreases and the post-fire deformability increases. The strength of Q690D steel decreases after 800 ℃ high temperature, but the mechanical properties of ER80-G weld metal do not change obviously, causing the result that fracture failure of welded joint does not occur at the weld but at the base metal under monotonic loading after 800 ℃ high temperature. The bearing capacity and deformation capacity of welded joints under cyclic loading are lower than those under monotonic loading. The mechanical properties of steel, weld metal as well as the welded joints obtained from the tests are able to provide basic test data to develop fracture analysis models considering the post-fire effect.