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Customers from all kinds of industries need valves of all varieties for their high-demand processes. Valves are available in a huge number of materials for any application imaginable. A few of these materials are PVC, carbon steel, stainless steel, cast iron, and ductile iron. In this post we will focus on two of those materials: ductile iron and cast iron. The argument of "ductile vs. cast iron valves" has been going on for decades, as not everyone knows the differences.
Luckily, comparing valves made of ductile iron and cast iron is simple, as these materials have just a few major differences. We will outline properties of both materials and then go through the pros and cons of each. By the end of this blog post, you will be an iron expert!
Cast iron (also known as gray iron) is a type of metal that has been in use for hundreds of years. It is an alloy made from 96%-98% iron, 2%-4% carbon, and small amounts of silicone. It has impressive temperature tolerance, with some cast iron capable of handling temperatures over F (C). When it comes to pressure, cast iron's strength depends on its pressure class. The two most common are class 125 and class 250. At less extreme temperatures, class 125 cast iron flange is rated for pressures between 150 and 200 psi. Class 250 cast iron is a bit tougher, with pressure ratings from 300 to 500 psi. These pressures can vary by end type.
Cast iron is strong and will usually go undamaged even after going through intense vibrations. The main drawback of cast iron valves is that they are not very ductile at all. Virtually any bending will cause cast iron to crack and become useless. One great quality of cast iron is that it is not very expensive. As far as metals go, cast iron is usually the most economical option, which makes it a solid alternative for people on a budget.
The second material we're looking at is ductile iron. Ductile iron is a more modern iron alloy that is made with nodule-shaped graphite. This gives the material excellent ductility, so it will not necessarily break when bent. The temperature limit is a bit lower than cast iron, but it is still quite high at F (730C). When it comes to pressure, ductile iron valves also use pressure classes: 150 and 300. At standard outdoor temperatures, class 150 ductile iron keeps a seal up to 250 psi. Class 300 can stand up to pressures as high as 640 psi.
Ductile iron has excellent corrosion resistance, tensile strength, and yield strength. Unlike cast iron, ductile iron does not break when it is bent, so it is more suited for high demand applications. Ductile iron is a strong and reliable material for pipes, fittings, and valves. One drawback is price. Ductile iron is typically more expensive than cast iron due to its more complicated chemical makeup. If your application requires a tougher material, however, you may need to spend a little more.
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Now that we've looked at both options individually, we will compare and contrast ductile and cast iron valves. Hopefully, this will help you decide which is best for you! We will compare these materials on durability, ease of installation, and price, so you can learn the most important details. For some more technical differences, check out this helpful article.
There you have it! Now you know that this is not an "ductile vs. cast iron valves" kind of issue. One is not always better than the other. It all depends on what you are using it for!
The production process of ductile iron pipes is to add magnesium, calcium and other alkaline earth metals or rare metals to the raw materials of ordinary cast iron pipes. The casting processes of ductile iron pipes include continuous casting, hot die casting and water-cooled centrifugal casting, among which the water-cooling method is the most advanced process in the world today, and the technical performance of ductile iron in different processes is different.
Compared with ordinary cast iron pipes, it not only maintains the corrosion resistance of ordinary cast iron pipes, but also has the advantages of high strength, good toughness, thin wall, light weight, impact resistance, large bending performance, and convenient installation. Therefore, ductile iron pipes are not only widely used abroad, but also widely used in China. In many areas of our country, ductile iron pipes have been widely used in medium and small diameter water supply pipes.
Steel pipes can be divided into seamed steel pipes and seamless steel pipes , and seamed pipes are generally used in the middle of water supply pipes. Compared with ductile iron pipes, steel pipes have the advantages of good toughness, high tensile strength, thin pipe walls, high pressure resistance, long pipes, and fewer joints. The biggest disadvantage is poor corrosion resistance and high price. Therefore, in general, except for small-diameter pipelines and special projects (such as pipe jacking projects).Ductile iron pipes and prestressed reinforced concrete pipes (suitable for large-diameter pipes, the maximum diameter of which exceeds mm), with the following characteristics:(1) To save energy, the main materials are sand and stone, which can be obtained locally.(2) Heavy weight, brittle texture, difficult cutting and relatively difficult construction.(3) The working pressure is 20%-40% lower than that of the ductile ink tube, which is 0.15-0.25MPa.(4) The maximum deflection angle is 1.5 degrees, while the ductile iron pipe can reach a maximum of 3.0 degrees, so the terrain adaptability of the prestressed reinforced concrete pipe is poor.Compared with ductile iron pipes, PVC pipes are characterized by smooth inner wall, light weight, corrosion resistance, good anti-scaling performance, and low price, but there are many disadvantages, mainly as follows:(1) It is easy to age, expands with heat and contracts with cold, so it should not be exposed to sunlight for a long time, and the storage room temperature should not be greater than 40°C.(2) Low strength, poor compressive performance, improper construction can easily cause deformation.(3) The rigidity is poor, the flexibility is poor, and it is easy to cause mouth leakage.1) The ductile pipe has the characteristics of withstanding high water supply pressure, resisting external loads and adapting to changes in geological conditions. It can be applied to areas with poor geology and crossing roads without additional processing of steel pipes. In addition, it has strong corrosion resistance and can be applied to Coastal and saline areas. At present, it is widely used in underground pipeline projects, and large-scale pipeline installation projects can better reflect its advantages of convenient installation and low labor intensity.2) The ductile iron pipe has good sealing performance and is not easy to leak, which can reduce the leakage rate of the pipe network and reduce the daily maintenance cost of the pipe network.3) Ductile iron pipes adopt flexible joints, which are more convenient for construction operations, can improve construction efficiency, improve construction conditions, and reduce construction costs. Most of the joints are connected by rubber rings, which are easy to operate, can shorten the construction period, and reduce construction costs.4) The tensile strength of ductile iron far exceeds that of gray cast iron, but is equivalent to that of steel. Therefore, for parts subject to static loads, the use of ductile iron saves material and is lighter than cast steel. The performance of ductile iron with different substrates varies greatly, and ductile iron has better fatigue strength.1. The installation of ductile iron pipes is greatly affected by human factors such as operational reasons.2. The corrosion resistance of the steel pipe is poor and the price is high. Therefore, in general, except for small-diameter pipelines and special projects (such as pipe jacking projects).3. Ductile iron pipes are generally not used in high-pressure pipe networks and have low pressure resistance. Because the pipe body is relatively bulky, machinery must be used for installation. If there is water leakage after the pressure test, all the pipes must be dug out, the pipes should be hoisted to a height that can be placed in the clamps, and the clamps should be installed to prevent water leakage.Spherical graphite has a smaller splitting effect on the metal matrix than other shapes of graphite, which can make the strength of cast iron reach 70-90% of the strength of the matrix structure, the tensile strength can reach 120kgf/mm2, and it has good toughness.The chemical composition of ductile iron except iron is usually: carbon content 3.0-4.0%, silicon content 1.8-3.2%, manganese, phosphorus, sulfur total not more than 3.0%, and appropriate amount of spheroidizing elements such as rare earth and magnesium.