Q690CFD高强钢焊接热影响区的断裂韧性

选用Gleeble-1500试验机模拟了两种成分Q690CFD高强钢的焊接粗晶热影响区(CGHAZ)，测试了CGHAZ的冲击韧性，并通过三点弯曲试样，测试了CGHAZ的CTOD特征值. 利用SEM对CTOD试样断口及近断口区裂纹扩展行为进行了分析. 结果表明,示波冲击止裂功及CTOD特征值δm/c/u(8)随温度降低呈明显下降趋势；将CTOD特征值δm用Boltzmann函数拟合后所得脆韧转变温度与示波冲击变化规律相对应；两种成分钢的CTOD失稳裂纹扩展路径与近断口区组织亚结构中大角度晶界和M/A分布位置有关.

Fracture toughness of CGHAZ of Q690CFD high-strength steel

The coarse grain heat affect zone (CGHAZ) of Q690CFD high-strength steel with two different compositions was simulated with Gleeble-1500 test machine to investigate its impact toughness, and the values of CTOD were measured by a series of three point bending tests. The fracture behavior of crack tip in CGHAZ was analyzed based on the fractography of CTOD samples with SEM. The results show that the variation trend of fracture toughness (critical CTOD valuesδm/c/u(8) and instrumented extension energy) declined with the decrease of temperature. The ductile-brittle transition temperature, fitted by Boltzmann function, was accordant with the variation tendency of instrumented impact. The path of crack propagation in CGHAZ of two different Q690CFD steels was determined by the position of high angle boundaries (≥15°) and M/A islands in metastructure nearby the fracture zone.