钢箱梁焊接接头的断裂韧度评定

Evaluation of welding procedure specification with crack tip opening displacement in steel box beam

采用冲击试验评定钢箱梁焊接工艺存在局限性,指出用裂纹尖端张开位移(CTOD)试验评定钢箱梁焊接工艺的优越性。介绍了焊接工艺CTOD断裂韧度评定的方法。针对港深西部通道香港段后海湾大桥钢箱梁焊接建造,运用英国标准BS7448对两项拟用焊接工艺进行CTOD试验评定。结果表明,埋弧自动焊工艺焊接接头的CTOD断裂韧度较高,该工艺可以直接用于钢箱梁焊接施工;而焊条电弧焊工艺焊接接头的CTOD断裂韧度较低,经扫描电子显微镜断口分析和X射线分析,发现其原因是焊缝中心存在气泡、微裂纹、夹杂物和硫等有害元素。试验评定结果为港深西部通道香港段后海湾大桥钢箱梁焊接质量控制提供了依据。

The limitations and problems of evaluation of welding procedure specification(WPS) of steel box beam with impact test were analyzed.It is necessary to use the crack tip opening displacement(CTOD) test to evaluate WPS of steel box beam.The CTOD test was presented.Two WPS used for the fabrication of steel box beam of back-gulf Bridge in Hong Kong-Shenzhen Western Corridor was designed and evaluated with CTOD test according to BS7448.The results are as follows:1) The values of CTOD fracture toughness in welded joints of submerged arc welding(SAW)are higher.The welding procedure specification of SAW can be directly applied to the fabrication of steel box beam.2) The values of CTOD in welded joints of shielded metal arc welding(SMAW) are lower.Hence the welding procedure specification of SMAW should be amended.It is found by scanning electron microscope that there are gas holes and micro-cracks and inclusion and harmful sulphur in the welding position.