For the ductile iron pipe, everyone may be unfamiliar with it. It doesn't matter. Next, Xiaobian will give you a comprehensive introduction to the ductile iron pipe. I believe we will have a new understanding of the ductile iron pipe after reading the following introductions.
First, the history of ductile iron pipe
In 1947, British H. Morrogh discovered that graphite was spherical when yttrium was added to hypereutectic gray cast iron to a content of 0.02wt% or more. In 1948, American APGanganebin et al. showed that magnesium was added to cast iron and then inoculated with ferrosilicon. Spheroidal graphite was obtained when the residual magnesium content was greater than 0.04 wt%. Since then, nodular cast iron has begun large-scale industrial production. The history of the use of ductile iron pipes can be traced back to the approximately 21.14Km pipeline from the Seine to Versailles in the outskirts of Paris in 1668. After 300 years of time, the main body is still in use except for the repair and replacement of some pipes and joints.
Second, the status quo and prospect of ductile iron pipe in China
China's ductile iron pipe industry started its development in the early 1990s with the strong support of the China Town Water Supply Association. After nearly 20 years of practical use, its safety and practicality have been universally recognized by the water supply industry. The annual output has reached 2.2 million tons, which is 11 times that of 1990. As China is a country lacking water resources, China’s current urban water supply capacity is obviously insufficient, and some cities are seriously deprived of water. Among the 668 cities across the country, there are more than 300 cities with water shortages, accounting for 46%; of which there are more than 140 cities that are seriously short of water. , accounting for 21%, water-saving water-saving business is in the ascendant, ductile iron pipe has broad prospects for development.
Third, the characteristics of ductile iron pipe
Ductile iron pipe is a kind of cast iron pipe. The quality requires that the cast iron pipe's spheroidizing grade be controlled to be 1-3 grade (spheroidization rate is 80%), so the mechanical ductile iron pipe finished product library of the material itself can be better improved, having the nature of iron, steel performance. The annealed ductile iron pipe has a metallographic structure of ferrite plus a small amount of pearlite, good mechanical properties, excellent corrosion resistance, good ductility, good sealing effect, easy installation, and is mainly used for water supply and gas transmission in municipal, industrial and mining enterprises. , oil, etc. A certain amount of spheroidal graphite is distributed on the ferrite and pearlite matrix. The proportion of ferrite and pearlite in the matrix is ​​different according to the nominal diameter and the requirement on the elongation. The proportion of small pearlite is small. Generally not more than 20%, the general control of large diameter is about 25%.
Fourth, the performance of ductile iron pipe
A ductile iron pipe is a type of cast iron that is an alloy of iron, carbon and silicon. In nodular cast iron, graphite is present in the form of a sphere. Generally, the size of graphite is 6-7 grades. The quality of the cast pipe requires that the spheroidization grade be controlled to 1-3 (spheroidization rate ≥80%), so the material itself is mechanical. The performance has been improved, with the nature of iron, the performance of steel. Annealed ductile iron pipe, the metallurgical structure of ferrite plus a small amount of pearlite, good mechanical properties. Ductile iron pipe is mainly called centrifugal ductile iron pipe, it has the nature of iron, steel properties, excellent anti-corrosion properties, good ductility, good sealing effect, easy installation, mainly used for municipal, industrial and mining enterprises, water supply, gas transmission, Oil and so on. It is the first choice for water supply pipes and has a high price/performance ratio. Compared with PE pipe, from the installation time, the spheroidal pipe is easier and faster to install than the PE pipe, and the inner and outer bearing pressures are better after the installation; from the perspective of hermeticity and corrosion resistance, the sealing property of the spheroidized pipe is better after the installation. Corrosion resistance can be improved by a variety of anti-corrosion measures; from the hydraulic performance point of view, because the specification of the spheroid tube generally refers to the inner diameter, the specifications of the PE pipe generally refer to the outer diameter, because under the same specification, the spheroid tube can achieve greater runoff; In terms of comprehensive installation and maintenance cost, the ball-and-tube tube has a superior cost performance. Spray zinc on the inner wall, cement mortar anti-corrosion materials, etc.
Fifth, anti-corrosion treatment
Asphalt coating
Asphalt paint coating is used to transport gas pipelines. Preheating the tubes before painting can increase the adhesion of the asphalt paint and accelerate drying.
2. Cement mortar lining + special coating
This kind of internal anti-corrosion measures is suitable for pipelines that transport sewage, and can improve the corrosion resistance of the lining.
3. Epoxy coal asphalt coating
Epoxy coal tar coating is applicable to both gas pipelines and sewage pipelines. It is a two-component coating with high adhesion and a very smooth surface.
4. Epoxy ceramic lining
The epoxy ceramic lining is suitable for sewage pipelines and gas pipelines, but due to the difficulty and high cost of the manufacturing process, there are certain limitations in its use. Epoxy ceramic linings have excellent adhesion and finish and are an excellent anti-corrosion coating.
5. Aluminate cement coating or sulfate cement coating
Both of these special cement coatings are suitable for the internal corrosion protection of ductile iron pipes for sewage pipelines and improve the ability to resist the acid and alkali components in sewage.
6. Polyurethane coating
It is a new type of green special coating developed to meet the needs of environmental protection. It has good wear resistance and corrosion resistance.
The above is a brief introduction for Xiaobian. If you want to know more related information, please continue to pay attention to Qijia Consulting. More exciting consultation, please stay tuned.
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