核级阀门唇焊焊缝熔深的超声检测方法

Ultrasonic testing method for weld penetration of nuclear-grade valve lip welds

核电阀体唇焊焊缝熔深不足可能导致其在服役期内无预期断裂,由此引起的流质泄漏将引起严重的安全事故。因此,极有必要在阀体焊接完成后进行熔深测量以保证足够的焊缝强度。该研究针对阀体唇焊缝粗糙余高曲面声学耦合差、熔深测量难的问题,提出基于喷水式超声聚焦检测技术的唇焊焊缝熔深测量方法。首先,根据核电阀体唇焊焊缝结构特点提出唇焊熔深的超声聚焦测量方法;其次,通过构建检测过程的有限元模型分析焊缝余高曲率对声场聚焦能力的影响,给出余高曲率各异的焊缝检测时的水距修正方法,以便在预定熔深范围内形成高能聚焦声场;最后,分析和提取与唇焊结构相关的检测信号特征,结合金相分析方法修正声速。研究结果显示:通过水距修正可改善焊缝曲率半径变化对聚焦声场的不利影响,曲率半径28.5 mm时焦区声压幅度仅下降11%,基于特征脉冲时间间隔及声速修正可测定焊缝熔深;与金相试验对比,绝对误差小于0.06 mm,满足核电阀门唇焊焊缝熔深测量的需求。

The insufficient weld penetration of the lip welding of the nuclear power valve body may lead to the unexpected fracture of the weld during the service period,and thefluid leakage caused by the fracture will cause serious safety accidents.Therefore,it is necessary to carry out non-destructive penetration measurement after the completion of the valve body welding.Aiming at the problems of poor acoustic coupling and difficulty in weld penetration measurement of the rough and high-profile surface of lip welds,a lip weld penetration measurement method based on ultrasonic water-jet focused testing technology is proposed.Firstly,the method for measuring the weld penetration is proposed according to the structural characteristics of the lip welding seam of nuclear power valve.Secondly,thefinite element model of testing course is established to analyze the influence of the curvature of the weld reinforcement on the sound focusing ability,and the water distance cor-rection method is given to form a high-energy focused soundfield within the penetration rang in the detection of the weld with different reinforcement’s curvatures.Finally,the detection signal characteristics corresponding to the lip welding structure are analyzed and extracted,and the sound velocity of thickness measurement is corrected by combining the metallographic measurement method.The research results show that the adverse effect of weld curvature radius change on focused soundfield can be improved by water distance correction,the sound pressure amplitude of the focal zone is only reduced by 11%when the radius of curvature is 28.5 mm,and the weld penetration can be determined based on the characteristic pulse time interval and sound velocity correction.Compared with the metallographic test,the absolute error of ultrasonic measurement is less than 0.06 mm,which meets the requirements of non-destructive weld penetration measurement of valve lip welding in nuclear power plants.