高产气井油管用13Cr-L80钢的腐蚀疲劳裂纹扩展行为

Corrosion Fatigue Crack Growth Behavior of 13Cr-L80 Steel for High-Production Gas Well Tubing

用复合磷酸盐完井液对取自13Cr-L80钢油管的紧凑拉伸试样进行预腐蚀处理,再进行疲劳裂纹扩展试验,通过分析疲劳裂纹扩展区形貌,研究了应力比(0.05~0.25)、加载载荷(10~14 kN)和载荷频率(0.6~1.8 Hz)对腐蚀疲劳裂纹扩展行为的影响。结果表明:随应力比增大,疲劳裂纹扩展区二次裂纹数量增多,13Cr-L80钢的裂纹扩展速率增大;随加载载荷增大,疲劳裂纹扩展区二次裂纹数量减少,裂纹扩展速率减小;载荷频率越高,疲劳裂纹扩展区二次裂纹数量越少,但裂纹尖端应变速率增大,裂尖变形更充分,导致裂纹扩展加快,试验中止时的循环次数减少。

Compact tensile specimens taken from 13Cr-L80 steel tubing were pre-corroded with composite phosphate completion fluid,and then was subjected to fatigue crack growth tests.By analyzing morphology of the fatigue crack growth zone,the effects of stress ratio(0.05-0.25),load(10-14 kN)and load frequency(0.6-1.8 Hz)on the corrosion fatigue crack growth behavior were studied.The results show that with increasing stress ratio,the number of secondary cracks in the fatigue crack growth zone increased,and the crack growth rate of 13Cr-L80 steel was improved.With increasing load,the number of secondary cracks in the fatigue crack growth zone decreased,and the crack growth rate was reduced.The higher the load frequency,the smaller the number of secondary cracks in the fatigue crack growth zone;but the strain rate at crack tips increased,and the crack tip deformation was more sufficient,leading to the fast crack growth,and the smaller number of cycles at test termination.