During the process of casting a metal part, a manufacturer forms a new solid shape by pouring molten metal into a mold and allowing the material to harden while assuming the conformation of the mold cavity. Three important ferrous castings have gained commercial significance:
Grey Iron– Steel as a commercial iron contains carbon up to 1.7%. Manufacturers sometimes refer to iron which contains a high percentage of graphite as “grey iron”. This cost-effective material has found wide utility although it does frequently display brittle properties.
Malleable Iron – Another specialized form of iron received the popular name “malleable iron” due to its property of exceptional softness. First developed hundreds of years ago, it contains significantly less carbon than cast iron. It permits machining readily after casting.
Ductile Iron – Ductile iron casting, produces strong ferrous metal parts which display the ability to withstand impacts well without rupturing easily. This malleable material has obtained many uses in the plumbing industry. Ductile iron casting creates pipes of many sizes; some manufacturers cast large pipes for underground use.
Today, manufacturers employ many technologies for creating useful iron and ferrous alloy products. Just a few popular commercial processes include die casting, sand casting, centrifugal casting and investment casting.
Cast iron gained popularity as a construction material during the Industrial Revolution. Yet this material possesses a brittleness which renders it unsuitable for some building purposes. During the 1940s, researchers reportedly discovered they could enhance cast iron alloys significantly by adding Magnesium as a constituent prior to casting. This modification changes the composition of cast metal parts on a granular level. It enhances strength and ductility.
Ductile iron, due to its enhanced ability to bend and withstand impacts without sustaining ruptures, gained popularity soon after its introduction into the commercial marketplace. Today, ductile iron castings still enjoy numerous applications. They have achieved particular prominence in the production of large pipes used by water and waste water systems. Reportedly, ductile iron has also found applications within the transportation and automotive industries.
The addition of Magnesium affects the properties displayed by ductile iron. This material demonstrates improved ductile and tensile strength, properties which contribute to its suitability in underground pipes subjected to repeated stress from shifting layers of earth. Ductile iron castings display greater strength than gray iron castings, for instance. They absorb impacts by bending, without rupturing readily.
Another property which contributes significantly to the popularity of ductile iron relates to its enhanced ability to resist corrosion compared with iron. Today, aging underground infrastructures in some urban areas have sustained problems due to the corrosion of heavy, brittle cast iron pipes installed decades ago (before the widespread use of ductile iron). By contrast, ductile iron pipes will withstand corrosion underground well for spans of 150 years, or more.
Ductile iron castings offer a number of distinct advantages as a commercial product.
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