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EVALUATION OF EMBRITTLEMENT OF WELD METAL IN PRIMARY COOLANT CIRCUIT.

主冷却剂回路中焊缝金属脆化的评估。

基本信息

批准号：
10680484
负责人：
KUWANO Hisashi
金额：
$ 2.18万
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：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10680484/
关键词：
Spinodal decomposition Phase separation Mossbauer effect Embrittlement Charpy impact Aging effect Life time Pressurized water reactor ステンレス鋼

项目摘要

Two thick panels of SUS304 type stainless steel were welded by SUS308 type stainless steel using submerged arc welding process. A change in the compositional and toughness of the weldmetal during aging at temperatures of 350℃ and 425℃ have been investigated by Mossbauer spectroscopy and Charpy impact testing.The width of the internal magnetic field distribution curve increased in the initial stage of aging followed by an increase in the paramagnetic absorption peak. And also the mean internal magnetic field increased with aging time. These experimental results led to a conclusion that the ferrite undergoes spinodal decomposition. The activation energy for the ferrite decomposition was estimated to be about 160-200kJ/mol. The change in the decomposition fraction of ferrite with aging time was interpreted by the sum of two hyperbolic tangent curves. A calculated curve was presented to predict the change in the composition of ferrite during aging at 320℃ by using an equation combined the activation energy.Charpy impact tests have been undertaken at 0℃ . Reductions in the Charpy impact energy were measured by aging at the above temperatures. In order to take account of the combined effect of aging time(t) and temperature(T), an aging parameter : p(T,t)=logt+0.4343(Q/R)(1/673-1/T), was introduced. The Charpy impact data were plotted as a function of p(T,t) to give a best fit value of Q = 125kJ/mol , for which all experimental points fell on a single master curve. The experimental data were fitted to a hyperbolic tangent function, U = UィイD20ィエD2+D{1+tanh(p(T, t)-E)/F}. The aging time required for the Charpy impact energy to drop to a half of that of the unaged weldmetal was estimated as 500kh at 320℃ on the basis of the above equation.

采用埋弧焊工艺，将两块SUS 304型不锈钢厚板与SUS 308型不锈钢进行焊接。用穆斯堡尔谱和夏比冲击试验研究了350℃和425℃时效过程中焊缝金属的成分和韧性的变化，时效初期内磁场分布曲线宽度增加，顺磁吸收峰增加。随着时效时间的延长，平均内磁场逐渐增大。这些实验结果得出的结论是，铁素体进行spinodal分解。铁素体分解的活化能约为160- 200 kJ/mol。铁素体分解分数随时效时间的变化可用两条双曲正切曲线之和来解释。采用结合激活能的方程，给出了320℃时效过程中铁素体成分变化的计算曲线，并进行了0℃夏比冲击试验。通过在上述温度下老化来测量夏比冲击能的降低。为了考虑时效时间（t）和温度（T）的综合影响，引入了时效参数：p（T，t）=logt+0.4343（Q/R）（1/673-1/T）。将夏比冲击数据绘制为p（T，t）的函数，以给出Q = 125 kJ/mol的最佳拟合值，其中所有实验点都落在单个主曲线上。将实验数据拟合为双曲正切函数U = U D20 D2+D{1+tanh（p（T，t）-E）/F}。根据上述公式，估算出320℃时，夏比冲击功降至未时效时的一半所需的时效时间为500 kh。