| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for accurately measuring a hardness distribution of a member, a method for detecting an abnormality in heat treatment, and a high-performance rolling bearing whose bearing part has guaranteed hardness distribution and heat-treatment quality. SOLUTION: A material being tested is irradiated with ultrasonic pulses, and reflected waves reflected at depth positions between the surface of the material being tested and its center are received, whereby the intensity of each reflected wave is obtained. In accordance with the intensity of each reflected wave and the depth position at which it was reflected, a reflected waveform curve that represents a relationship between the distance from the surface of the material being tested and the intensity of the reflected wave is drawn. Based on a correlation between the intensity of the reflected wave and the percentage of self-hardened tissue and a correlation between the percentage of the self-hardened tissue and hardness as obtained by using a standard material, the intensity of the reflected wave is converted into hardness, whereby a hardness distribution curve for the material being tested is obtained. Further, whether the material being tested has an abnormality in heat treatment is detected in accordance with a value obtained by dividing, among the reflected waves, the intensity of the reflected wave attributed to the self-hardened tissue and having the highest intensity by the intensity of the reflected wave attributed to quench-hardened tissue and having the lowest intensity. COPYRIGHT: (C)2010,JPO&INPIT |
