The Effect of Graphite Form on the Decarburization of Cast Iron (2nd Report)

Three kinds of cast irons (2.5%C, 1.5%Si) having different graphite forms in the same chemical compositions have been heated at 1000° for 4 hours in CaO powder to perform non-oxidation decarburization, and the decarburization phenomena have been investigated. It is found that the chill cast and then graphitized specimens having comparatively large graphite particles are more difficult to decarburize than the chill cast, quenched and then graphitized specimens having small graphite particles. In the same carbon content, the finer the graphite particle is, the larger the whole surface area and the easier the decarburization becomes. But the decarburization proceeds significantly in the specimens which were slowly cooled from melt and then graphitized, which is caused by the invasion of oxygen through the alloy along the cracks between the flaky graphite and the austenite at the decarburizing temperature.