P92钢持久寿命若干预测技术的分析

发布时间：2018-01-29 09:30

  本文关键词： TTP参数法 蠕变模型 应力松弛 寿命预测　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：P92钢是以Cr-Mo钢为基础,通过添加V、Nb以及1.8%W元素使得具有高温抗蠕变性,高热导性等优异性能,成为超(超)临界机组主蒸汽管道的重要用材。然而P92钢在高温高压长期服役时会发生蠕变行为,晶界产生蠕变孔洞使得高温构件失效,因而精确预测寿命和持久强度对高温炉管的使用年限和设计极其重要并从而确保高温构件的安全运行。传统的寿命预测TTP参数法以及基于蠕变的θ投影法和修正法均被提出,但基于TTP参数法中参数影响因素及参数值的敏感性研究关注较少,蠕变外推的寿命预测中相当部分主要以预测方程是否与蠕变实验曲线吻合为判定准则,而对于人们更为关注的外推效果的评述则不够。同时基于应力松弛方法在此钢中寿命预测鲜有报道。本论文运用P92钢的数据,比较分析不同的TTP参数法寿命预测精度并基于M-H参数法分析不同影响因素寿命预测之间的差异；基于蠕变曲线进行持久寿命外推中,分析不同蠕变模型持久寿命预测的差异并分析了基于蠕变速率的分段拟合法在持久寿命预测中的结果；基于应力松弛法转化蠕变数据进行寿命预测的结果分析等并客观分析三种方法在寿命预测精度上的优缺性。主要结论如下：(1)持久断裂时间对持久寿命外推的精度影响不大,短时持久断裂数据外推到10万小时的持久寿命与所有持久断裂数据外推结果几乎一致。应力影响因素对持久寿命预测精度影响较大,温度补偿越多的应力数据段进行寿命预测精度越高,反之越低且预测结果偏高。传统TTP参数法均能较好的进行数据的归一并预测,不同TTP参数法寿命预测精度相差不大,M-S常数值B的变化和OSD常数值P的变化对持久寿命外推结果影响很大。(2)综合比较不同蠕变模型进行持久寿命外推的分析结果,结果表明：复合模型比θ投影法更好描述P92钢的蠕变行为；外推蠕变速率时,0投影法的外推结果发生较大偏折,而复合模型的预测结果更接近实际变化趋势;5%-50%范围内的断裂应变对寿命预测结果影响较小,0投影法和复合模型预测的持久寿命值之间差距小。但均在600℃进行持久寿命时预测值偏高真实值；基于蠕变速率与时间曲线的分段拟合结果与修正模型持久寿命外推一致；蠕变模型关联Monkman-Grant关系持久寿命外推曲线偏高于真实值。(3)运用应力松弛方法并关联TTP参数法进行持久寿命外推,结果表明较高温度时持久寿命预测精度越高,反之越低；在不同温度下,Norton应力指数大约在9.6到11.6,激活能大致为412 KJ·mol-1,蠕变微观机制是位错滑移机制；通过激活体积的计算,随着温度的升高,激活体积增大。
[Abstract]:P92 steel is based on Cr-Mo steel. By adding VNb and 1.8W elements, P92 steel has excellent properties such as high temperature creep resistance and high thermal conductivity. It has become an important material for the main steam pipeline of supercritical unit. However, the creep behavior of P92 steel will occur during the long service at high temperature and high pressure, and the creep holes in grain boundary will lead to the failure of high temperature components. Therefore, it is very important for the service life and design of high temperature furnace tube to accurately predict the life and lasting strength and to ensure the safe operation of high temperature components. The traditional life prediction TTP parameter method and theta projection method based on creep are used. Amendments were proposed. However, based on the sensitivity study of parameter influencing factors and parameter values in TTP parameter method, less attention has been paid to the life prediction of creep extrapolation. Whether the prediction equation is consistent with the creep experimental curve is the criterion in life prediction of creep extrapolation. However, it is not enough to comment on the extrapolation effect that people pay more attention to. At the same time, there are few reports based on stress relaxation method to predict the life of this steel. In this paper, the data of P92 steel are used. The life prediction accuracy of different TTP parameter method is compared and the difference between different influencing factors is analyzed based on M-H parameter method. In the extrapolation of durable life based on creep curve, the difference of durable life prediction between different creep models is analyzed, and the results of subsection fitting method based on creep rate in durable life prediction are analyzed. The results of life prediction are analyzed based on the creep data transformed by stress relaxation method, and the advantages and disadvantages of the three methods in the accuracy of life prediction are analyzed objectively. The main conclusions are as follows: 1). The rupture time has little effect on the accuracy of the extrapolation of the durable life. The rupture life extrapolated to 100,000 hours is almost consistent with the extrapolation results of all the rupture data, and the stress influencing factors have a great influence on the prediction accuracy of the rupture life. The higher the precision of life prediction in the stress section with more temperature compensation, the lower the prediction result is and the higher the prediction result is. The traditional TTP parameter method can be used to predict the data better. The life prediction accuracy of different TTP parameter methods is not different. The variation of M-S constant B and OSD constant P have a great influence on the extrapolation results of durable life. The results show that the composite model is better than theta projection method in describing the creep behavior of P92 steel. When the creep rate is extrapolated, the extrapolation results of the projection method are deflected greatly, while the predicted results of the composite model are closer to the actual trend. The fracture strain in the range of 5- 50% has little effect on the life prediction results. There is a small difference between the value of durable life predicted by the projection method and the composite model, but the predicted value is higher than the true value when the lasting life is carried out at 600 鈩，

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