The chemical composition of ductile iron, excluding iron, is typically: 3.6–3.8% carbon, 2.0–3.0% silicon, and a total of no more than 1.5% manganese, phosphorus, and sulfur, along with appropriate amounts of rare earth elements and magnesium as spheroidizing agents.
Ductile iron possesses high strength, high plasticity, wear resistance, and corrosion resistance. According to ISO 1083, ductile iron castings offer a wide range of mechanical and physical properties, such as high-plasticity grades with tensile strength greater than 800 N/mm² and elongation greater than 17%, or grades with a minimum tensile strength of 370 N/mm². Ductile iron manhole covers exhibit excellent performance in important indicators such as compressive strength, seismic resistance, and service life.
The ductile iron used for manufacturing drainage manhole covers should comply with the requirements of GB/T 1348-2019.
The surface of drainage well covers should be intact and smooth, with clear and undamaged patterns, markings, and lettering. They should be free of burrs, sharp edges, warping, and deformation. The material should be uniform, and the surface quality of castings should comply with the relevant provisions of CJ/T 511-2017. The allowable height difference between the well cover and the well base after closing is ±1mm.
Inspection well covers should have patterns and markings that allow for quick identification of the pipeline well type, inspection well cover load rating, manufacturer, and other information.
