Manhole Covers And Urban Sewer

Cast iron manhole covers are divided into ductile iron manhole covers and gray cast iron manhole covers. Generally speaking, ductile iron manhole covers of the same weight are more compressive than gray iron manhole covers. The material used for gray iron manhole covers is generally HT200, and the material used for ductile manhole covers is generally QT500-7. Ductile iron manhole covers are mainly made of ductile iron. The quality of this manhole cover is related to the spheroidization rate. The commonly used coating for treating castings is anti-rust asphalt paint. Of course, the surface of ductile iron manhole covers is also treated with anti-rust asphalt paint. One advantage of ductile iron manhole covers is that due to the high strength and good toughness of ductile iron, the ductile iron manhole covers are about 30% lighter than the same type of gray cast iron manhole covers. Good toughness. The impact value is similar to that of medium carbon steel, and it is more than 10 times that of gray iron material.
Strong corrosion resistance. In the water spray corrosion test, the corrosion amount in 90 days is only 1/40 of the steel pipe and 1/10 of the gray iron pipe. The service life is 2 times that of gray iron pipes and 5 times that of ordinary steel pipes.
Good plasticity. The elongation is a Y7%, which is similar to that of high carbon steel, while the elongation of gray iron material is zero.
high strength. Tensile strength A ba Y420MPa, yield strength A sa Y300MPa, which is the same as low carbon steel and three times that of gray iron material.
Due to the spheroidal graphite microstructure of ductile iron, ductile iron is superior to cast steel in terms of reducing vibration, so it is more conducive to reducing stress. An important reason for choosing ductile iron is that ductile iron is less expensive than cast steel. The low cost of ductile iron makes this material more popular, casting efficiency is higher, and the machining cost of ductile iron is less.
The strength of ductile iron is comparable to that of cast steel. Ductile iron has a higher yield strength, with a minimum yield strength of 40k, while cast steel has a yield strength of only 36k. In most municipal applications, such as water, salt water, steam, etc., the corrosion resistance and oxidation resistance of ductile iron exceeds that of cast steel.