The cast iron grate is also the manhole cover. The casting of the manhole cover is divided into cast iron, ductile iron and bronze manhole cover
Ductile iron manhole cover is mainly made by ductile iron manhole cover, the quality of this manhole cover is involved in the problem of spheroidization rate. Ductile cast iron manhole covers have an advantage, because of the high strength of ductile iron, good toughness, so that the ductile cast iron manhole covers than the same type of gray cast iron manhole covers about 30% lighter.
At the same time:
1. Good toughness. The impact value is similar to that of medium carbon steel, which is more than 10 times of gray iron material.
2. Strong corrosion resistance. In the water spray corrosion test, the corrosion amount in 90 days is only 1/40 of that of steel pipe and 1/10 of that of gray iron pipe. The service life is 2 times of gray iron pipe and 5 times of ordinary steel pipe.
3. Good plasticity. Elongation ≥7%, similar to high carbon steel, but gray iron material elongation is zero.
4. High intensity. The tensile strength ob ≥420MPa and yield strength OS ≥300MPa are the same as low carbon steel and 3 times as gray iron material.
Because of its nodular graphite microstructure, ductile iron is better than cast steel in reducing vibration capacity, so it is more beneficial to reduce stress. An important reason for choosing ductile iron is that ductile iron costs less than cast steel. The low cost of ductile iron makes this material more popular, more efficient, and reduces the machining cost of ductile iron.