Study on the ultrasonic attenuation and false indications of austenitic stainless sleet Steel weldment

스테인레스강(鋼) 용접부(熔接部)의 초음파감쇠(超音波減衰) 및 거짓신호(信號)에 관(關)한 연구(硏究)

Some studies have been made on the effects of the attenuation on the result of ultrasonic examination of austenitic stainless steel weldment and also on the cause of false indications. The differences in the amplitudes and the metal paths of the ultrasonic examinations have been measured experimentally, for two kinds of waves, one passed through only the parent material and the other one through the weldment. The effect of probe angles and frequency on the examination data have been investigated using the shear wave. It has been found that the false indications were caused by back reflection from the weld metal surface due to the characteristics of ultrasonic wave propagation. It has been confirmed that the probe of $2.25\;MHz\;and\;60^{\circ}$ is the best choice in the ultrasonic examination and that the correction of amplitude for attenuations is necessary.