| 摘要 |
PURPOSE:To obtain a high strength ductile cast iron tube having high toughness bainite structure as matrix by using molten ductile cast iron having specified Si content and executing two step inoculations by Fe-Si series to the above- mentioned material to obtain high strength tube even only as cast condition and further specified cooling from austenite temp. range after pouring. CONSTITUTION:When the molten ductile cast iron having 2.4-3.0wt% Si content is poured into a mold 1 for centrifugal casting through a pouring runner 5 from a ladle 4, the inoculation by Fe-Si series is executed at chute part from the ladle 4 to a receiving port 5A of the runner 5 and at spout part from a tapping port 5B of the runner 5 to an inner surface of the metal mold 1. Then, the cast iron tube is formed by the centrifugal casting and during austenite range for its temp., hot water is supplied into the inner surface of rotating cast iron tube by a suitable means to cool rapidly until 300-450 deg.C, and after that it is cooled by air. In this way, the above-mentioned inoculation is desirable to be executed by 0.05-0.15wt% at chute part and 0.10-0.30wt% at spout part to the pouring cast iron amount.
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