Cast iron manhole covers are divided into ductile iron manhole covers and gray iron manhole covers. Generally speaking, ductile iron manhole covers of the same weight have stronger compressive strength than gray iron manhole covers The material used for gray iron manhole covers is generally HT200, while the material used for ductile iron manhole covers is generally QT500-7
Characteristics of ductile iron manhole covers:
Good resilience. The impact value of medium carbon steel is more than 10 times that of gray iron materials.
Strong corrosion resistance. The water spray corrosion test shows that the corrosion amount after 90 days is only 1/40 of steel pipes and 1/10 of gray iron pipes. The service life is twice that of gray iron pipes and five times that of ordinary steel pipes.
Good plasticity. The elongation rate is ≥ 7%, similar to high carbon steel, while the elongation rate of gray iron material is zero.
High intensity. The tensile strength ó b is ≥ 420MPa, and the yield strength ó s is ≥ 300MPa, which is the same as low-carbon steel and three times that of gray iron materials.
Due to the microstructure of spherical graphite in ductile iron, ductile iron is superior to cast steel in reducing vibration ability, making it more conducive to reducing stress. One important reason for choosing ductile iron is that its cost is lower than that of cast steel. The low cost of ductile iron makes this material more popular, with higher casting efficiency and lower machining costs.