| In determining non-metallic inclusion rating in steel, the efficiency and reliability of conventional manual method and computer aided automatic method using image analyzer have been investigated. To see the effect of shape change of the inclusions on the cleanliness value based on existing test standards, the test coupons examined were taken from continuously casted slab, hot rolled plate and from cold rolled sheet where some inclusions were extremely elongated. Results show that the cleanliness values determined by two methods agree fairly well for both samples with globular oxide inclusions and with properly elongated inclusions. For samples with extremely elongated inclusions, however, the cleanliness value processed by image analyzer tends to be smaller than that of manual count. It appears that the automatic method gives faster and more reliable cleanliness value since the image analyzer determines the value in area fraction instead of in point fraction. |
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