Ductile Iron pipe is centrifugally cast by pouring molten iron against the inside wall of an externally cooled rotating metal mold. The DeLavaud casting process incorporates a metal mold which has a peen pattern on its inside diameter. This peen pattern is transferred to the pipe during the casting process. There are several reasons why the mold has this peen pattern in 4- 42” sizes. The peen pattern helps dispense thermal shock and helps the mold pick up the molten iron by increasing surface friction between the mold and the iron as the mold is rotated. Additionally, before casting each piece of pipe, an inoculating dry spray is distributed on the inside of the mold. The peen pattern on the mold acts as an anchor pattern that holds and evenly distributes the inoculant. This inoculant increases nodule count, helps refine the grain and nodular size, minimizes carbides, and makes the pipe more easily annealed. The inoculant also acts to deoxidize the iron, thereby preventing the formation of pin holes.
48-64” pipe do not have a peen pattern. The process is a chill-free wet spray casting process. A refractory slurry is sprayed on the inside of the mold followed by the inoculating dry spray. Because of the slurry, no peen pattern is required to hold and evenly distribute the inoculant.