核电汽轮机焊接低压转子1∶1模拟件接头高周疲劳性能及门槛值预测

Study on high-cycle fatigue properties of one-to-one simulation specimen of low pressure turbine rotors welding joint and its threshold prediction

测试了25Cr2Ni2Mo V百万千瓦级核电汽轮机焊接低压转子1∶1模拟件埋弧焊接头的高周疲劳性能,高周疲劳断口分析表明,内部启裂源多为气孔,且有明显的分区现象.已有文献计算启裂区应力强度因子幅的公式多应用于内部夹杂物启裂的情况,文中针对模拟件埋弧焊接头高周疲劳裂纹椭球形气孔裂纹源,提出裂纹源形状影响因子对已有公式进行修正,建立了通过高周疲劳测试和断口观察预测疲劳裂纹扩展门槛值的方法.该方法通过白光干涉形貌仪确定启裂区的面积、采用对数拟合确定启裂源形状影响因子等手段,预测出埋弧焊接头焊缝区的疲劳裂纹扩展门槛值,并进行了模拟件埋弧焊接头的疲劳裂纹扩展门槛值的测试,结果一致,进一步验证了方法的合理性.

The high cycle fatigue properties of a submerged arc welding joint of one-to-one simulation 25Cr2Ni2 MoV specimen used in 1 000 MW nuclear power low pressure turbine rotors were studied. Most of the interior crack sources were porosities,and different zones on the fractured surface can be distinguished under scanning electron microscope. The existing expression on stress intensity factor of crack initiation is well suited to the inclusion. Considering the particularity of the elliptical shape of crack source,the sharp influencing factor for the crack source was introduced to revise the expression. Within the new expression,an approach to predict the threshold was established,by testing high cycle fatigue properties and observing the fracture surface. For the studied welding joint,white-light interfering profilometer was used to measure the area of the crack initiation zone,and logarithm fitting method was applied to get the sharp influencing factor. The predicted threshold value of the welding joint was found in a good agreement with the experiment result.