核电主管道用316LN不锈钢焊缝热老化脆化的趋势

开展了核电站主管道用316LN不锈钢焊缝在325、365和400℃下1.5万h的加速热老化试验,测量了不同热老化时间下焊缝的冲击性能和焊缝铁素体的纳米硬度。以纳米硬度作为热老化脆化参量,利用Arrhenius方程得出该焊缝热老化激活能约为93.1kJ/mol;并以焊缝室温冲击功为预测参数,通过拟合的方法获得了焊缝热老化脆化预测方程;利用热老化激活能和热老化脆化预测方程预测了主管道用316LN焊缝在服役温度下60年寿命期内的热老化脆化趋势。试验结果表明,随着热老化时间的增加,焊缝的冲击韧性显著下降,焊缝中铁素体纳米硬度快速增加。预测结果表明,在运行15年内主管道焊缝韧性迅速下降,在随后的运行过程中下降趋缓。

Tendence of thermal aging embrittlement of weld of primary pipe made of 316LN stainless steel in nuclear power plant

To evaluate thermal aging of primary pipe for nuclear power plant in life time, accelerated thermal aging experiments of weld of primary pipe made of 316LN stainless steel were performed at 325, 365 and 400?? for 15000h. Charpy impact energy and nanohardness of ferrite phase of weld were tested for different thermal aged time. Taking the nanohardness as the standard of thermal aging embrittlement, the thermal aging activation energy for weld of 316LN,93.1 kJ/mol was obtained by Arrhenius Formula. Meanwhile, taking the Charpy impact energy of weld at room temperature as the prediction parameter of thermal aging embrittlement, the equation for prediction of thermal aging embrittlement of weld was obtained by fitting method. Finally, the Charpy impact energy of the weld during 60 operation years at actual operation temperature was estimated by thermal aging activation energy and the prediction equation. The experimental results indicate that the nanohardness of the ferrite phase in the weld increases quickly, and the impact toughness decreases sharply with increase of thermal aging time. The predicted results show that the toughness of the weld decreases fast in the early 15 years, and then decreases slowly.