CLEANLINESS EVALUATION METHOD OF STEEL BY IMMERSION ULTRASONIC INSPECTION METHOD

摘要

PPROBLEM TO BE SOLVED: To provide a method allowing accurate evaluation of the cleanliness of a steel by carrying out fast detection and evaluation of non-metallic inclusions in response to the type of a steel product by using an immersion ultrasonic inspection method. PSOLUTION: The method is for evaluating the cleanliness of a steel, and it is provided with a process of sampling a test piece of steel which is an evaluation object from the forged steel product, a process of detecting the non-metallic inclusion existing in the test piece by using the immersion ultrasonic inspection method, and an inclusion evaluating process of evaluating the cleanliness of steel on the basis of a result obtained by the detecting process. In the inclusion evaluating process, the cleanliness of steel is evaluated by excluding a range of the following (1) or a range derived from an equation of the following (2) from an inclusion evaluation object range as a range where porosities are distributed in response to the carbon concentration of the test piece. (1) when the carbon concentration (C%) is 0.4%, the range (%) to be excluded from the center of the test piece is 30. (2) when the carbon concentration (C%) is 0.4%, the range (%) to be excluded from the center of the test piece is 27.3(C%)+19.1. PCOPYRIGHT: (C)2004,JPO&NCIPI