Ductile iron manhole covers are generally divided into round and square ones. In terms of urban road administration, round manhole covers are generally used, because round manhole covers are not easy to tilt, which can better protect the safety of pedestrians and vehicles. The use of circle is mainly based on the fact that the length of each diameter of the round manhole cover passing through its center is the same. In this way, if the manhole cover is rolled up by passing vehicles, its diameter will be slightly wider than the lower wellhead no matter how it is rolled up, and the manhole cover will not fall into the wellhead.
Nodular well cover is one of the products of nodular cast iron. Nodular graphite is obtained from nodular cast iron through spheroidizing and inoculation treatment, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, thus obtaining higher strength than carbon steel. Ductile iron is a kind of high-strength cast iron material developed in the 1950s. Its comprehensive performance is close to that of steel. It is precisely based on its excellent performance that it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness and wear resistance. Ductile iron has rapidly developed into a widely used cast iron material, which is second only to gray iron. The so-called "replacing steel with iron" mainly refers to nodular cast iron.
If the square is used, because the diagonal of the square is significantly longer than the length of each side, when such a well cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, causing potential safety hazards. If the wellhead is round or significantly smaller than the well cover, the square well cover will not fall into the well. This involves the maximum utilization and saving of materials. The use of the wellhead depends on the size of the wellhead. If it is necessary to install a square well cover with an area much larger than the wellhead, then the utilization and practical value of the materials are naturally less effective than that of the round well cover, which not only saves the materials of the well cover, but also ensures the safety of the wellhead.
In rural areas and cable wells, square is generally used to prevent rainwater and other liquids from entering.
Composition of ductile iron well cover:
Pig iron is an iron carbon alloy with a carbon content of more than 2%. The carbon content of industrial pig iron is generally 2.5% - 4%, and contains elements such as C, SI, Mn, S, P, etc. It is a product of smelting iron ore through blast furnace. According to the different forms of carbon in pig iron, it can be divided into steelmaking pig iron, casting pig iron and nodular cast iron. Cast iron in which the precipitated graphite is spherical. Spherical graphite has less splitting effect on metal matrix than flake graphite, making the strength of cast iron reach 70~90% of the strength of matrix structure, and the tensile strength can reach 120 kgf/mm2, and it has good toughness. The chemical composition of nodular cast iron except iron is generally 3.6~3.8% carbon content, 2.0~3.0% silicon content, no more than 1.5% manganese, phosphorus and sulfur content, and appropriate rare earth, magnesium and other nodulizing agents.
