Experiments on Toughness Deterioration of Brittle Region at Welded Joints of Steel Beam to Column

1995年日本兵库地震中，钢结构梁柱焊接节点经常发生断裂。特别是在靠近沿着焊缝的母材中发生了许多断裂。我们推测这种断裂是由于远离焊接熔合区的脆性区的韧性劣化引起的。使用常规钢和新开发的钢结构用钢进行了以下两种关于脆性区的强度和韧性的实验。焊接接头板的拉伸试验1）梁翼缘接头焊接到100m2）柱接头焊接到100m2。对梁与柱焊接接头的梁进行了弯曲试验，试验参数除钢种外，还包括层间温度、焊接线能量和根部间隙。在焊接板拉伸试验中，未发现焊接区附近脆性区韧性劣化导致母材断裂.梁翼缘焊接到隔板上的一个试样在层间温度为440 ° C和焊接热输入为29 Kj/cm时，在焊接区附近的脆性区域出现梁翼缘断裂。而其他试件的脆性区没有梁翼缘断裂。

Fractures at welded joints of steel beam to column were frequently observed in 1995 Hyogo Earthquake. Especially, many fractures occurred in the base metal near along the welding line. We presumed that such fractures derived from the toughness deterioration of the brittle region which was apart from a welding fusion zone. The following two kinds of experiments on the strength and the toughness of the brittle region were performed using conventional steels and a newly developed steel for the steel structure.1. Tension tests of plates with a welded joint1) Beam flange joint welded to diaphragm2) Column joint welded to diaphragm2. Bending tests of beams with beam joint welded to columnInterpass temperature, weld heat input and root gap were adopted as the parameters in addition to the steel grades in the experiments.The following results were obtained from the experiments :1. No fractures of the base metals due to the toughness deterioration of the brittle region near the welded zone were produced in the welded plate tension tests.2. One specimen with the beam flange welded to the diaphragm at an interpass temperature of 440* and weld heat input of 29 Kj/cm exhibited the beam flange fracture of the brittle region near the welded zone. But the other specimens had no beam flange fractures of their brittle regions.