The main component of milling cast iron covers or nodular cast iron by spheroidization and inoculation by spherical graphite, effectively improve the mechanical properties of cast iron, especially the plasticity and toughness increased, resulting in higher than the strength of carbon steel.
The development of nodular cast iron manhole cover after decades of development, its comprehensive performance is close to the steel, it is based on its excellent performance, has been successfully used in casting complex stress, strength, toughness and wear resistance requirements of the higher parts.
Ductile iron covers are generally round and square, in the urban areas of highways, generally used round, because the circular manhole cover is not easy to tilt, can better protect the safety of pedestrians and vehicles。 Use the circular, mainly taking into account the circular covers through its center of each diameter length is the same, so if the covers were passing vehicles rolled up, because no matter how rolling, the diameter will be slightly wider than the wellhead, will not fall to the wellhead to manhole cover。
And if the square is used, because the square diagonal is obviously longer than each of its side length, such a manhole cover is rolled up, it is easy to fall into the well along the diagonal line of the wellhead, resulting in security risks。 If the wellhead is circular or smaller than the manhole cover, the square manhole cover will not fall into the well。
Here is the question of the maximum use and savings of a material. The wellhead is used depends on the size of the wellhead, if to a non square manhole cover installed in the above area is far greater than the wellhead, then the material utilization and practical value of nature is not directly using the circular covers more effective, saving material covers also ensures the safety of the wellhead.
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