动载结构用高强钢Q960E热影响粗晶区疲劳寿命与△Kth的关系研究

Relationship Research of △Kth and Fatigue Life in the Heat-Effected Coarse Grain Zone for the Dynamic Structure High-Strength Steel Q960E

基于模拟焊接热循环试验，对动载结构用高强钢Q960E热影响粗晶区进行了疲劳寿命和裂纹扩展试验研究。通过得到Paris方程建立了不同焊接热模拟工艺下疲劳裂纹扩展门槛值△Kth在正弦脉动载荷下疲劳寿命值的近似线性关系。试验结果表明，疲劳寿命随疲劳裂纹扩展门槛值△Kth的增大而增加，其延寿微观机理在于组织中的结构取向存在差异，所形成的大角度晶界（不小于15°）可有效迫使裂纹转向，从而提高材料的疲劳寿命。

Based on the simulation of welding thermal cycle test, the fatigue life and crack propagation test of dynamic structure high-strength steel Q960E in the heat-affected coarse grain zone were investigated. The approximate linear relationship between fatigue crack propagation threshold value （△Kth） using Paris equation under different welding thermal simulation technique and fatigue life under different cyclic loading was obtained. The results showed that the fatigue life increased with the growth of AKth. The working micro-mechanism of prolonging life was due to the orientation differences of substructure, and the formation of large Angle grain boundaries （≥ 15°） was able to force the crack to swerve effectively, which improved the fatigue life of materials.