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Ductile Iron Manhole Covers
  • Ductile Iron Manhole Covers

    Ductile iron manhole covers are a kind of ductile iron products. Ductile iron is obtained by ballning and inoculation to obtain spherical graphite, which effectively improves the mechanical properties of cast iron, especially improves the plasticity and toughness, so as to obtain higher strength than carbon steel. Ductile iron is a kind of high strength cast iron material developed in the 1950s with its comprehensive performance close to that of steel. It is based on its excellent performance and has been successfully used in casting some of the complex, strength, toughness and wear resistance Requires higher parts. Ductile iron has rapidly developed into gray cast iron, the application of a wide range of cast iron materials. The so-called "iron on behalf of steel", mainly ductile iron.

    Ductile iron manhole covers are divided into round and square, the main components: carbon content greater than 2% iron-carbon alloy, elongation ≥ 7%

    Ductile iron manhole covers are generally divided into round and square, in the urban areas of the road, the general use of circular, because the circular manhole covers are not easy to tilt, to better protect the safety of pedestrians and vehicles. The use of a circle is mainly due to the fact that the circular manhole covers are passing through each of their diameters in the same length, so that if the manhole covers are rolled by the passing vehicle, the diameter of the manhole covers will be slightly higher than the lower Wide, manhole covers will not fall into the wellhead.

    And if the square is used, because the diagonal of the square is significantly longer than each of its sides, such a well is rolled, it is easy to fall along the diagonal direction of the wellhead, causing security risks. If the wellhead is rounded or significantly smaller than the manhole, the square manhole covers will not fall into the well. Here is a matter involving the maximum use and savings of a material. The use of the manhole covers depends on the size of the wellhead, and if it is necessary to install a square well in the area above the wellhead, then the use and practical value of the material naturally do not directly use the circular manhole covers are more effective, both the material of the manhole covers, To ensure the safety of the wellhead.

    And in the countryside and the use of cable wells, the general use of square, which can better prevent the introduction of rain and other liquid.

    Ductile Iron Manhole Cover Features

    Ductile iron manhole covers are mainly made of ductile iron out of the manhole covers, the quality of this well manhole covers the quality of the ball to the problem. Casting commonly used paint is rust-proof asphalt paint, of course, the surface of the ductile iron manhole cover is also treated by spraying rust-proof asphalt paint. Ductile iron manhole covers have an advantage, is due to ductile iron high strength, good toughness, making the ductile castings than the same type of gray cast iron manhole covers light about 30%.

    Impact value and carbon steel in detail, gray iron material is more than 10 times.

    Strong corrosion resistance. Spray corrosion test, ninety days of corrosion is only 1/40 of the steel, gray iron pipe is 1/10. Life is 2 times the gray iron pipe, 5 times the ordinary steel pipe.

    Good plasticity. Elongation ≥ 7%, similar to high-carbon steel, and gray iron material elongation is zero.

    Tensile strength ób ≥ 420MPa, yield strength ós ≥ 300MPa, and low carbon steel is the same, three times the gray iron material.

    Due to the microstructure of nodular graphite, the ductile iron is superior to cast steel in reducing the vibration ability, so it is more beneficial to reduce the stress. One of the important reasons for choosing ductile iron is that ductile iron is less expensive than cast steel. The low cost of ductile iron makes this material more popular, with higher casting efficiency and less machining costs for ductile iron.

    The strength of ductile iron and the strength of cast steel are comparable. Ductile iron has a higher yield strength, the yield strength of the lowest 40k, while the yield strength of cast steel is only 36k. In most municipal applications, such as: water, salt water, steam, etc., ductile iron corrosion resistance and oxidation resistance are more than cast steel.


    Ductile iron castings have been used in almost all major industrial sectors where they require high strength, plasticity, toughness, abrasion resistance, severe heat and mechanical shock, high temperature or low temperature resistance, corrosion resistance and dimensional stability. In order to meet these conditions of use, ductile iron has many grades that offer a wide range of mechanical and physical properties.

    Such as the International Organization for Standardization ISO1083 provides most of the ductile iron castings, mainly non-alloy production. Obviously, this range includes high strength grades with tensile strength greater than 800 N / mm and elongation of 2%. The other extreme is a high plastic grade with an elongation greater than 17% and a lower strength (minimum of 370 N / mm). Strength and elongation are not the only roots of the designer's choice of material, while other decisive important properties include yield strength, modulus of elasticity, abrasion resistance and fatigue strength, hardness and impact properties. In addition, corrosion resistance and oxidation resistance and electromagnetic properties may be critical to the designer. In order to meet these special uses, developed a group of austenitic ductile iron, usually called proud Ni-Resis ductile iron. These austenitic ductile iron, mainly with zinc, chromium and manganese alloy, and included in international standards.

    (1) Strict requirements of the chemical composition of the original iron liquid requirements of carbon and silicon than gray cast iron, reduce the ductile iron manganese, phosphorus, sulfur content

    (2)Iron liquid temperature than gray cast iron to compensate for the ball, the treatment of iron liquid temperature loss.

    (3) To carry out the ballification treatment, that is, to add molten iron liquid agent.

    (4) To join the inoculant for inoculation treatment.

    (5) Ductile iron flow is poor, shrinkage is large, so the need for a higher pouring temperature and a larger pouring system size, rational use of riser, cold iron, the use of sequential solidification principle.

    (6) Heat treatment.

    Ductile Iron Manhole Covers Iinstallation

    In order to ensure the normal use of cast iron manhole covers, pay attention to the installation quality, so that the size of accurate, easy to install, easy to open, clean appearance, according to check the technical specifications of cast iron manhole covers, specially formulated the following installation rules:

    The brick masonry masonry shall be constructed in accordance with the size of the manhole designed by the Design Institute to determine its inner diameter or length * width, and the radius (if it is the best for construction according to the actual construction). When forming the well, it is important to note that the inner diameter of the wellhead should be consistent with the inner diameter of the wellbore. The well manhole covers should be flat with the road surface. Concrete or asphalt will be poured into the well laying, the lid should be opened in time to clean, to avoid mortar or asphalt will check the manhole covers and the seat into one, so as not to affect the future open.

    Cement roadway seat installation, in the wellhead brick body with C25 concrete casting 20CM thick ring beam smooth, be sure to keep the seat of the Quartet real, the overall formation, not loose, and in the manhole cover cast wide 40CM concrete casing (If it is cement pavement, can also be cast width of 20CM concrete protection ring, and reinforced with steel) maintenance period to 10 days or more.

    In order to maintain the appearance of the appearance of the manhole cover, the surface pattern and writing clear, in the construction of asphalt pavement application of thin metal manhole cover in the manhole covers or scrap oil brush manhole cover to prevent the asphalt oil sprayed on the manhole cover; in the cement road construction, The plastic film manhole covers the manhole covers to prevent the cement mortar from damaging the surface of the manhole covers, damaging the surface patterns, writing, and cleaning the manhole covers surface with water at the end of the day.

    When installing the cast iron manhole covers on the asphalt pavement, it is important to pay attention to avoid the direct grinding of the construction machinery. When the road is cast as a whole, the holes should be reserved slightly larger than the wells in the pavement. (All concrete pavement should be installed in the second stone after the completion of grinding) to ensure the quality of manhole manhole cover to extend the service life.

    Above all please use, the construction unit attention, due to improper installation or vehicle overload caused by damage to the manhole covers, do not belong to the scope of warranty, do not bear joint and several liability.

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