Ductile iron manhole covers are mainly made of spheroidal graphite cast iron. The quality of such manhole covers is related to the problem of nodularity. The commonly used coating for processing castings is rust-proof asphalt paint. Of course, the surface of nodular cast iron manhole covers is also spray-treated with rust-proof asphalt paint. The nodular cast iron manhole cover has an advantage, because the nodular cast iron manhole cover has a high strength and good toughness, which makes the nodular cast manhole cover 30% lighter than the same type of gray cast iron manhole cover.
Features of Ductile Iron Manhole Covers:
Good toughness. The impact value is similar to that of medium carbon steel, and is more than 10 times that of gray iron material.
Strong corrosion resistance. In the water spray corrosion test, the corrosion amount in the 90-day period is only 1/40 of the steel pipe, which is 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 ≥7%, which is similar to that of high-carbon steel, while the elongation of gray iron materials is zero.
High strength. Tensile strength ób≥420MPa, yield strength ós≥300MPa, which is the same as low-carbon steel, and is three times that of gray iron material.
Due to the ductile iron microstructure of nodular cast iron, nodular cast iron is better than cast steel in terms of weakening vibration 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 ductile iron cast iron makes this material more popular and more efficient, and reduces the machining costs of ductile iron bench leg.
The strength of nodular cast iron is comparable to that of cast steel. Ductile 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 are better than cast steel.
Ductile Iron Bench Leg
Ductile iron castings have been used in almost all major industrial sectors, which require high strength, plasticity, toughness, wear resistance, severe thermal and mechanical shock resistance, high or low temperature resistance, corrosion resistance and dimensional stability. In order to meet these changes in use conditions, many grades of ductile cast iron are available, providing a wide range of mechanical and physical properties.
Most of the nodular cast iron castings, as specified by the International Standards Organization ISO1083, are mainly produced in non-alloyed state. Obviously, this range includes high-strength grades with a tensile strength greater than 800 Newtons / mm and an elongation of 2%. At the other extreme are high-plastic grades with elongation greater than 17% and correspondingly lower strength (minimum 370 Newtons / mm). Strength and elongation are not the only roots for a designer's choice of ductile iron lamp post’s materials, but other decisive and important properties include yield strength, elastic modulus, wear resistance and fatigue strength, hardness and impact properties. In addition, corrosion resistance and oxidation resistance as well as electromagnetic performance may be critical to the designer. In order to meet these special uses, a group of austenitic ductile iron was developed, usually called Ni-Resis dead ductile iron. These austenitic ductile irons are mainly alloyed with zinc, chromium and manganese and are listed in international standards.