P92钢接头Ⅳ型开裂蠕变孔洞临界值的分析及应用  

Analysis and application of critical value of type Ⅳ cracking creep hole in P92 steel joint

作　　者：杨超[1] 石仁强 Yang Chao;Shi Renqiang(Jiangsu Frontier Electric Technology Co.,Ltd.,Nanjing 211102,China)

机构地区：[1]江苏方天电力技术有限公司,南京211102

出　　处：《焊接》2024年第9期62-68,共7页Welding & Joining

摘　　要：【目的】分析P92管道接头热影响区发生Ⅳ型开裂的蠕变孔洞临界值的影响因素,得到蠕变孔洞临界值计算方法,为评估接头开裂风险提供依据。【方法】收集服役后发生Ⅳ型开裂的P92接头,在未开裂处取样进行610℃下不同应力条件的高温持久蠕变试验,然后使用光学显微镜、电子显微镜观察服役开裂接头和持久断裂接头热影响区的蠕变孔洞分布形貌,并借助图像分析软件测量蠕变孔洞的面积分数,同时使用硬度仪测试热影响区软化情况,最后综合测试结果分析细晶区软化程度和接头应力水平对蠕变孔洞临界值的影响,并拟合应力、显微硬度、孔洞临界值三者之间的函数关系。【结果】研究发现,P92钢接头细晶区相比于接头其它区域软化速度更快,但软化作用并非其发生Ⅳ型开裂的必要条件,当应力水平较高时,细晶区没有发生明显软化时就可以触发蠕变开裂;得到接头轴向应力水平、蠕变孔洞面积分数临界值和显微硬度的函数关系式。【结论】引起Ⅳ型开裂的蠕变孔洞面积分数临界值与相对应力水平(轴向应力与硬度的比值)有关,相对应力水平越高,蠕变孔洞临界值越小,接头安全性就越低;通过测量接头细晶热影响区的蠕变孔洞面积分数和显微硬度,可以估算开裂接头的轴向应力水平,也可以评估在役未开裂接头的Ⅳ型开裂风险。[Objective]The factors influencing the critical value of the creep hole in the HAZ of P92 pipeline joint were analyzed,and the calculation method of the critical value of the creep hole was obtained,which provides a basis for evaluating the joint cracking risk.[Methods]The P92 joints with type Ⅳ cracking after service were collected,and the samples were taken from the uncracked parts for high temperature sustained creep test under different stress conditions at 610℃.Then,the distribution morphology of creep holes in the HAZ of the cracked joints and permanently fractured joints were observed by optical microscope and electron microscope,and the area fraction of the creep holes was measured by image analysis software.At the same time,hardness tester was used to test the softening of the HAZ.Finally,synthesizing the test results the influence of the softening degree of the fine crystal zone and the stress level of the joint on the critical value of the creep hole was analyzed,and the functional relationship between the stress,hardness value and the critical value of the hole were fitted.[Results]It was found that the fine-grained zone of P92 steel joint has a faster softening rate than other areas of the joint,but the softening was not the necessary condition for type Ⅳ cracking.When the stress level was high,the creep cracking could be triggered when the fine-grained zone did not significantly soften.The functional relations of the joint axial stress level,the critical value of creep hole area fraction and microhardness were obtained.[Conclusion]The critical value of creep hole area fraction causing type Ⅳ cracking was related to the relative stress level(the ratio of axial stress to hardness).The higher the relative stress level,the smaller the critical value of creep hole and the lower the safety of joint.The axial stress level of cracked joints could be estimated by measuring the creep hole area fraction and microhardness in the FGHAZ of the joints,and the type Ⅳ cracking risk of uncracked joints in s

关 键 词：超(超)临界机组 P92管道 Ⅳ型开裂 蠕变孔洞 

分 类 号：TG407[金属学及工艺—焊接]