ductile Cast iron pipes are used for water supply, drainage and gas pipelines. They include cast iron pipes and fittings. Labor intensity is small. According to different casting methods, it is divided into continuous cast iron pipe and centrifugal cast iron pipe, centrifugal iron pipe is divided into sand type and metal type. According to different materials, it can be divided into gray cast iron pipe and ductile cast iron pipe. According to the interface form, it is divided into flexible interface, flange interface, self-anchor interface and rigid interface. Among them, the flexible cast iron pipe is sealed with a rubber ring; the flanged cast iron pipe is fixed with a flange, and the inner gasket is sealed with a rubber flange gasket; the rigid interface is generally larger in the cast iron pipe socket, and after the straight pipe is inserted, it is sealed with cement. This process is now Basic elimination.