Product Introduction

Nodular cast iron manhole cover is a kind of nodular cast iron products, nodular cast iron through spheroidization and inoculation treatment to obtain spherical graphite, effectively improve the mechanical properties of cast iron, especially improve the plasticity and toughness, so as to get higher strength than carbon steel. Ductile iron is a kind of high strength cast iron material developed in the 1950s, its comprehensive performance is close to steel, it is based on its excellent performance, has been successfully used to cast some complex forces, strength, toughness, wear resistance requirements of high parts. Ductile iron has rapidly developed into a cast iron material second only to gray iron and widely used. The so-called "iron instead of steel" mainly refers to ductile iron.

Product classification

Ductile iron manhole covers are generally divided into round and square, in the urban road administration, the general use of round, because the round manhole cover is not easy to tilt, can better protect the safety of pedestrians and vehicles. The use of the circle is mainly to consider that each diameter length of the circular manhole cover through its center is the same, so that if the manhole cover is rolled up by a passing vehicle, because no matter how it is rolled up, its diameter will be slightly wider than the following wellhead, and the manhole cover will not fall into the wellhead.

If the square is used, because the diagonal of the square is obviously longer than the length of each side, such a manhole cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, causing safety hazards. If the well head is rounded or significantly smaller than the cap, the square cap will not fall into the well. Here comes the question of maximum utilization and economy of materials. The use of the manhole cover depends on the size of the wellhead, if you have to install a square manhole cover with an area far larger than the wellhead, then the utilization and practical value of the material is naturally more effective than the direct use of the circular manhole cover, which not only saves the material of the manhole cover, but also ensures the safety of the wellhead.

Ductile iron manhole cover

In the countryside and cable Wells, square is generally used, which can better prevent the entry of liquids such as rain.

Ingredient

Pig iron is an iron-carbon alloy with a carbon content of more than 2%, and the carbon content of industrial pig iron is generally 2.5%--4%, and contains C, SI, Mn, S, P and other elements, which is the product of smelting iron ore by blast furnace. According to the different forms of carbon in pig iron, it can be divided into steelmaking pig iron, cast pig iron and ductile iron.

The precipitated graphite is spherical cast iron. The cutting effect of spherical graphite on metal matrix is smaller than that of flake graphite, so that the strength of cast iron can reach 70 ~ 90% of the strength of the matrix, the tensile strength can reach 120kgf/mm2, and it has good toughness. In addition to iron, the chemical composition of ductile iron is usually: carbon content 3.6 ~ 3.8%, silicon content 2.0 ~ 3.0%, the total amount of manganese, phosphorus, sulfur does not exceed 1.5% and an appropriate amount of rare earth, magnesium and other nodulators.

Other information

Ductile iron manhole covers are mainly made of ductile iron manhole covers, and the quality of this manhole cover involves the problem of spheroidization rate. The commonly used coating for the treatment of castings is anti-rust asphalt paint, of course, the surface of the ductile iron manhole cover is also treated by spraying anti-rust asphalt paint. Ductile iron manhole cover has one advantage, that is, due to the high strength and good toughness of ductile iron, the ductile iron manhole cover is about 30% lighter than the same type of gray cast iron manhole cover.

Features of ductile iron manhole cover

Good toughness. The impact value is similar to that of medium carbon steel and more than 10 times that of gray iron.

Strong corrosion resistance. Water spray corrosion test, 90 days of corrosion is only 1/40 of the steel pipe, is 1/10 of the gray iron pipe. The service life is 2 times that of gray iron pipe and 5 times that of ordinary steel pipe.

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

High strength. Tensile strength ob ≥420MPa, yield strength os ≥300MPa, the same as low carbon steel, is three times the gray iron material.

Due to the spheroidal graphite microstructure of ductile iron, ductile iron is better than cast steel in reducing vibration capacity, so it is more conducive to reducing stress. An important reason to choose ductile iron is that ductile iron is cheaper than cast steel. The low cost of ductile iron makes this material more popular, more efficient casting, and also reduces the machining cost of ductile iron.

The strength of ductile 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 exceed that of cast steel.

Property

Ductile iron castings have been used in almost all major industrial sectors, which require high strength, plasticity, toughness, wear resistance, resistance to severe thermal and mechanical shock, high or low temperature resistance, corrosion resistance and dimensional stability. In order to meet these changes in the conditions of use, ductile iron is available in many grades, providing a wide range of mechanical and physical properties.

Most nodular cast iron castings, as specified by the International Organization for Standardization ISO1083, are mainly produced in a non-alloying state. Obviously, this range includes high strength grades with tensile strength greater than 800 newtons/mm and elongation of 2%. At the other extreme are high plastic grades with elongation greater than 17% and correspondingly low strength (as low as 370 Newton/mm). Strength and elongation are not the only criteria for designers to select materials, but other critical properties include yield strength, modulus of elasticity, wear resistance and fatigue strength, hardness and impact properties. In addition, corrosion resistance and oxidation resistance as well as electromagnetic properties may be critical for designers. In order to meet these special uses, a group of austenitic ductile iron has been developed, which is usually called austenitic ductile iron. These austenitic nodules are mainly alloyed with zinc, chromium and manganese and are included in international standards.

Detection Systems

Copper Silica Sol Investment Casting

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