| 摘要 |
PURPOSE:To make content ratios measurably without increasing errors in spite of presence of ruggedness and thickness fluctuation on surfaces by determining the content ratios based on the propagation time ratio of ultrasonic longitudinal and transverse waves. CONSTITUTION:A ferritic stainless steel slab 11 or the like which is rolled to thickness D is constituted of dendrite parts 10-1, 10-2, and free crystal parts 10-3 or the like of the thickness (d). If the propagation times Tl, Ts of the ultrasonic longitudinal and transverse waves reciprocating in this slab 11 are measured by way of an ultrasonic wave generating and detecting coil 32 or the like and the ratio between the times Tl and Ts is determined, the free crystal rate F=d/D is calculated based on the equation I without measuring the thickness D. Hence, the content ratio of two kinds of structures of the metallic material is measured without increasing errors in spite of presence of ruggedness and thickness fluctuation on the surfaces. Here, Vl1, Vl2 are the velocities of sound of longitudinal waves in the free crystal parts and dendrite parts; Vs1, Vs2 are the velocities of sound of the transverse waves in the free crystal parts and dendrite parts. |
