Ductile iron is a strong, durable, flexible, and elastic material. Its mechanical properties are similar to steel, far exceeding standard cast iron, and its comprehensive properties are close to steel. Ductile iron is a solid metal object, which is produced by pouring molten nodular iron into the cavity of the mold. While inside the cavities of the mold the iron then cools and hardens into the desired shape. Ductile iron usually contains more than 3% carbon; it can bend, twist, or deform without breaking. Thanks to these properties, it has been successfully used to produce castings with high strength, toughness, and wear resistance. Ductile iron is the most used cast iron material today only second to grey cast iron. In this article we will give you an overview of this unique material including some historical background, the main properties of ductile iron, its applications and advantages.
Ductile iron was invented in 1943 by Keith Millis, along with Alber Gagnebin, and Norman who improved cast iron by adding magnesium to strengthen it. In the 1950s and 1960s ductile iron became more and more popular for many commercial applications due to its useful qualities. Cast iron and ductile iron have opposite physical properties due to their different microstructures. The graphite and carbon contained in the cast iron appear in the form of flakes. Tensile loads higher than the natural tensile strength of cast iron will lead to cracks and quickly spread out from the stress points in the flake microstructure. As a result, the cast iron hardly elongated. It is a brittle material, so its use in tensile and impact load applications is limited. The graphite in spheroidal graphite cast iron appears spherical, so it is sometimes called spheroidal graphite. The term nodular cast iron stems from the shape of the carbon nodules in this type of cast iron This unique microstructure makes ductile cast iron more resistant in terms of bending and impact loads when compared to traditional cast iron.
Ductile iron is a type of cast iron, but due to the round graphite structure cast into metal, it is more fatigue and wear-resistant than cast iron. Thanks to the spherical graphite ductile iron can withstand greater impacts, while also incorporating great elongation properties.
Ordinary grey cast iron also contains a small amount of graphite, but they look like wavy lines, called scales, as opposed to the graphite balls commonly found in ductile iron. The only way to actually graphite is with a microscope. Ductile iron is composed of, obviously, iron (about 95%) and a combination of carbon, silicon, manganese, magnesium, phosphorus, sulfur, and copper. Sometimes more copper is added to increase strength, and more nickel or chromium is added to increase corrosion resistance. In this case, 15-30% of iron is replaced by other elements.
One of the biggest benefits of using ductile iron is that they are much stronger than grey cast iron.
Ductile iron is more resistant to wear and therefore has long-lasting power. This makes it ideal for applications requiring more resistance due to friction. In these cases, the graphite structure can act as a dry lubricant. This type of iron has good heat dissipation capacity and is usually not difficult to process, but it is more difficult to process than ordinary grey cast iron. It is very suitable for use on large machines because it can suppress sound and vibration better than steel.
There are several advantages that ductile iron has for designers:
1. It is easily cast and machined
2. The strength-to-weight ratio is excellent
3. Lower cost compared to steel
4. A unique combination of toughness, low-cost manufacturing, and reliability
Ductile iron has higher strength and ductility than grey cast iron. These characteristics enable it to be effectively used in a variety of industrial applications, including pipes, auto parts, wheels, gearboxes, pump casings, racks in the wind power industry, etc. Ductile iron does not break like grey iron, so it can be used safely in impact protection applications such as bollards. The best uses of iron using ductile are for applications where you need strong, more wear-resistant metals. Some of the most common applications are the manufacture of automotive parts such as car and truck axles, connecting rods, gears, and gearboxes, and cylinders. But there are many more industries that make use of the properties of iron ductile to manufacture components or products like housings, manifolds, machine tooling, oil well pumps, and others.
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