Ductile Iron Manhole Cover Performance:

Grey iron castings are widely used in almost all major industrial sectors, which require high strength, plasticity, toughness, wear resistance, resistance to severe thermal and mechanical impacts, resistance to high or low temperatures, corrosion resistance, and dimensional stability. To meet these varying service conditions, there are numerous grades of ductile 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 non-alloyed condition. Clearly, this category includes high-strength grades with tensile strengths exceeding 800 N/mm² and elongation of 2%. At the other end are high-plasticity grades with elongation greater than 17%, corresponding to lower strength (as low as 370 N/mm²). Strength and elongation are not the sole basis for material selection by designers; other critical properties include yield strength, elastic modulus, wear resistance, fatigue strength, hardness, and impact properties. Additionally, corrosion resistance, oxidation resistance, and electromagnetic properties may be crucial for designers. To meet these requirements, a group of austenitic spheroidal irons, commonly referred to as Ni-Resist spheroidal irons, has been developed. These austenitic spheroidal irons are primarily alloyed with zinc, chromium, and manganese and are listed in international standards.

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

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

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

Due to the spheroidal graphite microstructure of ductile iron, it outperforms cast steel in reducing vibration capabilities, thus being more conducive to stress reduction. One significant 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.

Graphite cast iron has comparable strength to cast steel, with a higher yield strength starting at 40k, compared to cast steel's 36k. In most municipal applications, such as water, saltwater, steam, etc., the corrosion and oxidation resistance of graphite cast iron exceeds that of cast steel.