Ultrasonic Inspection of Cast Iron with a Focusing probe

Abstract

In the conventional ultrasonic inspection of cast iron, a dead zone of probe and surface roughness makes ultrasonic inspection of near-surface flaws such as blow holes and pin holes difficult. In this paper, an improved technique of ultrasonic inspection using a focusing probe is applied to various types of artificial defects in cast iron. The results show that with a water distance such that the focal point of the ultrasonic beam locates beneath the flaw, echo of the near-surface echo on an A-scan display. The surface roughness causes the echo height of both surface echo and flaw echo to fluctuate, but their fluctuations become smaller with decreasing water distance. The scanning graphs of flaw echo height show a wavy pattern and a flat-shaped pattern reflected from the small flaw and plane flaw, respectively. The C-scan display is an effective method for presentsing the distribution of flaws.