Ductile iron manhole covers are a type of malleable iron commodity.Malleable iron obtains spherical high-purity graphite based on spheroidization and creation,which reasonably improves the physical properties of pig iron,greatly improves plastic deformation and ductility,and thus achieves higher compressive strength than carbon steel.Malleable cast iron is a high toughness pig iron raw material that developed in the 1950s.Its comprehensive shape is close to steel,and based on its characteristics,it has been successfully used to forge some parts with complex supports,high compressive strength,ductility,and wear resistance.Malleable cast iron has rapidly developed into a widely used raw material for pig iron,which is only secondary to steel castings.Simply put,'replacing steel with iron'refers to malleable cast iron.

　　The ductile iron manhole cover cannot be opened according to its circular opening,while the square ductile iron manhole cover will fall into the hole if inserted diagonally.Having a"mouth"to maintain the outer cover represents that the hole at the bottom is smaller than the outer cover,so that other appearances are sufficient.(Triangle or other curves with stable overall width also serve this purpose,but the production and manufacturing of circular covers are much easier.)

　　The total area of circular ductile iron manhole covers is smaller than that of square ones,which can reduce the raw materials required for ductile iron manhole covers,indicating lower cost.The hand hole structure on the surface of the rolling bearing and the mechanical equipment included ensure flatness and prevent falling traffic.The application of CNC lathes for circular casting parts is much easier to produce and process.

　　The ductile iron manhole cover does not need to be rotated to align with both ends of the ductile iron manhole cover.The circular ductile iron manhole cover can be easily moved according to flipping.