Floating graphite on top of Heavy Section Ductile Iron

In order to study the effect of composition on the morphology of thick and large section graphite, bulk sampling was carried out on the stepped test block. The floating graphite on the top of the section and the abnormal graphite distortion distribution in the center of the block were observed and studied. At the same time, the physical and chemical properties of the cross section samples were tested.

On the top of test block of section e3-3, e3-6 and e3-9 with wall thickness of 400mm, a layer of dark black graphite floating layer appears on the top of the test block of section e3-3, e3-6 and e3-9 (as shown in the figure). The height of graphite floating layer varies from 20 mm to 50 mm, and the thickness of graphite floating layer increases with the increase of carbon equivalent.

On the sections with wall thickness of 150 mm and 70 mm, the metal color is uniform, there is no color difference layer suspected of graphite floating, and no graphite floating defect is found.