MEASURING METHOD OF GRAIN SIZE OF STEEL MATERIAL USING PULSE LASER LIGHT

摘要

PURPOSE:To permit an on-line inspection of the grain size of the steel material having a high temperature and moving at a high speed without contact by using the spread of the width of an ultrasonic pulse detected as a mechanical displacement. CONSTITUTION:With its diameter decreased by means of a lens 3, a high-power pulse laser beam having a short time-width is applied to the surface 1a of the steel material 1 to generate ultrasonic pulse wave in the steel material 1 in an acoustic point source manner. Then the mechanical displacement produced on a surface 1b when the ultrasonic wave having propagated through the steel material 1 reaches the surface 1b is detected by means of a detector 4. The spread of the width of the ultrasonic pulse detected as the mechanical displacement of the surface 1b is measured to obtain the grain size of the steel material 1.