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Mossbauer Spectrometry Study of Aging Deterioration in Duplex Stainless Steel

双相不锈钢时效劣化的穆斯堡尔谱研究

基本信息

批准号：
07650805
负责人：
KUWANO Hisashi
金额：
$ 1.41万
依托单位：
Muroran Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Cast duplex stainless steels which are used as the pump casings and valve casings in the cooling system of atomic power plants are degraded in the mechanical properties after avery long term use. The life time of the steel may be evaluated by the activation energy obtained by the accelerated test performed at temperatures higher than the operation temperature. The present study aims to investigate the origin of the degradation and to measure the activation energy for the commercial CF3M cast duplex stainless steel aged at 623-723K.The average intemal magnetic filed of Fe, <H>, in the ferrite measured by Mossbauer spectroscopy increases with agin time. The change in <H> corresponds to a decrease in the mean Cr content that in dicates the phase decompositon of ferrite. The activation energy for the <H> change is obtained to be about 180kJ/mol.The ferrite hardness increases with aging time corresponding with the <H> change. The activation energy obtaine from the hardness change are 160-17 … More 0kJ/mol which is consistent with one mentioned above. These results suggest that the hardness change is ascribed to the phase decomposition which is controlled by the volume diffusion of Cr or Fe atom in ferrite.V-notch Charpy impact energy, CE,measured at 273K decreases with aging time. The decrease is mainly ascribed to the phase decomposition of ferrite. However the activation energy of 63kJ/mol obtained for the CE Change is unconsistent with those mentioned above. The CE change is assumed to be expressed by a tanh function : CE (t, T) =A-B {1+tanh [(logt-C- (Q loge/RT)) /D]}, in which unknown parameters are detemined experimentally by a least square fit. Charpy energy curves at the operation temperature of PWR and BWR are calculated from the above result.if a 30J value is assumed to guarantee areasonable ductility, 50years of life time will be expected for the PWR and BWR application.There is a good corelation between the average intemal magnetic field change and the Charpy impact decrease. Mossbauer spectroscopy may be useful for anondestructive evaluation of the aging embrittlement. Less

铸造双相不锈钢作为核电站冷却系统中的泵壳和阀壳，经过长期使用，其力学性能下降。钢的寿命可以通过在高于操作温度的温度下进行加速试验获得的活化能来评估。本文研究了CF 3 M铸造双相不锈钢在623- 723 K时效过程中，铁素体中Fe的平均内磁场随阿金时间的增加而增加的原因，并测定了时效过程的激活能<H>。这种变化<H>对应于平均Cr含量的降低，表明铁素体的相分解。结果表明，相变激活能<H>约为180 kJ/mol，铁素体硬度随时效时间的延长而增加<H>。由硬度变化求得的激活能为160-17 关于我们 0 kJ/mol，与上述结果一致。结果表明，合金的硬度变化是由Cr或Fe原子在铁素体中的体积扩散所控制的相分解引起的，273 K下的V形缺口夏比冲击功CE随时效时间的延长而降低。降低的主要原因是铁素体的相分解。然而，获得的CE变化的活化能63 kJ/mol与上述结果不一致。假设CE变化由双曲正切函数表示：CE（t，T）=A-B {1+tanh [（logt-C-（Q logge/RT））/D]}，其中未知参数通过最小二乘拟合实验确定。根据上述结果计算了压水堆和沸水堆运行温度下的夏比能量曲线，如果假定30 J的值能保证合理的延性，则压水堆和沸水堆的寿命可望达到50年，平均内部磁场变化与夏比冲击降低有很好的相关性。穆斯堡尔谱可用于非破坏性评价时效脆化。少