| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of finding, by ultrasonic inspection, a pressure-bonded flaw under the surface of a bloom cogging-rolled from a continuously cast billet. SOLUTION: A method of determining a defect under the surface of a bloom 1 comprises: inspecting presence or absence of a pressure-bonded flaw 3 or a biting flaw 4 under the surface of the blooms 1 obtained by cogging-rolling the continuously cast billets composed of molten steel of the same charge; judging the result by level control; sampling a test piece through inspecting again the blooms 1 of the charge including a bloom 1 out of a predetermined level; and determining presence or absence of the pressure-bonded flaw 3 or the biting flaw 4 from a microphotograph and a macrophotograph of the test piece. Thus, the judgment prevents the bloom 1 with the pressure-bonded flaw 3 or the biting flaw 4 from flowing out to the next process. COPYRIGHT: (C)2008,JPO&INPIT
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