Nodular cast iron manhole cover is mainly made of nodular cast iron. The quality of this manhole cover involves the problem of spheroidization rate. The commonly used paint for castings is anti-rust asphalt paint. Of course, the surface of the ductile iron manhole cover is also sprayed with anti-rust asphalt paint. An advantage of ductile iron manhole covers is that due to the high strength and toughness of ductile iron, ductile iron manhole covers are about 30% lighter than gray cast iron manhole covers of the same type.

　　 Good toughness. The impact value is detailed with that of medium carbon steel, which is more than 10 times that of gray iron.

　　 Strong corrosion resistance. In the water spray corrosion test, the corrosion amount in 90 days is only 1/40 of that of steel pipes and 1/10 of that of gray iron pipes. The service life is twice that of gray iron pipes and 5 times that of ordinary steel pipes.

　　 Good plasticity. The elongation is ≥7%, which is similar to that of high-carbon steel, while the elongation of gray iron is zero.

  high strength. Tensile strength ób≥420MPa, yield strength ós≥300MPa, which is the same as low-carbon steel and three times that of gray iron materials.

　　 Due to the nodular graphite microstructure of nodular cast iron, nodular cast iron is superior to cast steel in terms of vibration reduction ability, 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 spheroidal graphite cast iron makes this material more popular, the casting efficiency is higher, and the machining cost of spheroidal graphite cast iron is reduced.

　　 The strength of ductile iron is comparable to that of cast steel. Nodular cast iron has a higher yield strength, with a minimum yield strength of 40k, while the yield strength of cast steel is only 36k. In most municipal applications, such as water, salt water, steam, etc., the corrosion resistance and oxidation resistance of ductile iron exceed those of cast steel.