Ductile iron manhole covers are primarily made from ductile iron, and the quality of these covers is closely related to the spheroidizing rate. The common coating for castings is anti-rust asphalt paint, and naturally, the surface of ductile iron manhole covers is also treated with anti-rust asphalt paint. A notable advantage of ductile iron manhole covers is that, due to their high strength and good toughness, they are approximately 30% lighter than gray cast iron manhole covers of the same type.

Features of Ductile Iron Manhole Covers:

Good toughness. Impact value is comparable to medium carbon steel, and over 10 times that of gray iron material.

High corrosion resistance. The water spray corrosion test shows that the corrosion after 90 days is only 1/40 of steel pipe and 1/10 of gray cast iron pipe. Its service life is twice that of gray cast iron pipe and five times that of ordinary steel pipe.

Good plasticity. Elongation ≥7%, similar to high-carbon steel, while grey iron material has zero elongation.

High strength. Tensile strength ób≥420MPa, yield strength ós≥300MPa, similar to low-carbon steel, and three times that of gray iron material.

Due to the spheroidal graphite microstructure of ductile iron, it is superior to cast steel in reducing vibration capability, thus more conducive to stress reduction. One important reason for choosing ductile iron is its lower cost compared to cast steel. The low cost of ductile iron makes it more popular, increases casting efficiency, and also reduces machining costs for ductile iron.

The strength of ductile iron is comparable to that of cast steel. Ductile iron boasts a higher yield strength, starting at 40k, whereas cast steel's yield strength is only 36k. In most municipal applications, such as water, saltwater, steam, etc., ductile iron exhibits superior corrosion and oxidation resistance compared to cast steel.

Performance:

Grey iron castings are nearly applied in all major industrial sectors, which require high strength, plasticity, toughness, wear resistance, resistance to severe thermal and mechanical shocks, tolerance for high or low temperatures, corrosion resistance, and dimensional stability. To meet these varying conditions of use, there are numerous grades of spheroidal cast iron available, offering a wide range of mechanical and physical properties.

Most gray iron castings, as specified by ISO 1083 of the International Organization for Standardization, are produced in a non-alloy state. Clearly, this scope includes tensile strengths greater than 800 newtons per millimeter.