Cast Iron Relevance - Coursework Example

Cast Iron - Still Relevant Today April 24, 2012 Cast Iron - Still Relevant Today 1. Introduction Some materials that were useful in earlier days have now become irrelevant due to discovery of better ones and advancement of technology. Metals are still very important elements in our life today and are used in a number of areas including manufacture of vehicles, bridge and house constructions, and even making household items such as furniture and utensils. However, whether a particular type of metal is still relevant today is a subject that needs to be investigated. In this report, cast iron is put into focus to determine whether it is still relevant today. Emphasis is laid on its engineering properties; implications for its use and how it is used; source of its raw materials; how it is produced, fabricated and recycled; its value for specific uses; its economic aspects; and its regional and/or national significance. 2. What is cast iron? Cast iron is a metal alloy that contains iron, and often, silicon and carbon. The iron used to make cast iron is mainly the pig iron. Cast iron exhibit different colours when it breaks depending on the constituents or impurities in it. Carbide impurities are responsible for the white colour in white cast irons. They also cause the straight fracturing of the metal. Grey cast iron contains graphite flakes that cause deflection of a crack, which in turn results in multiple cracks in the cast iron when it fractures. 3. Engineering properties Cast iron has a number of essential engineering properties that makes it still relevant in modern uses and demands for materials. It has low melting point, good machinability property, good fluidity, is easily castable, resistant to wear and deformation, and durable. It is also resistant to weakening and destruction by rust (oxidation). These properties of cast iron make it suitable for a number of uses, including in making pipes, and automotive and machines parts. However, Leupen (2006) has noted that the use of cast iron in making gear gearbox cases, and engine cylinder heads and blocks is declining significantly. The comprehensive strength of grey cast iron is comparable to that of medium and low carbon steel. However, it is less resistant to shock and has lesser tensile strength than steel. Because of graphite constituent in grey cast iron, machine slides made of grey cast iron exhibit a free-working action. Cast iron is also brittle and can easily be fractured when hammered with a very heavy object. Its low melting point (between 1150 and 1200°c) might not be suitable for heat resistant constructions. 4. Engineering requirements and implications for its use and how it is used a. Raw materials The availability of raw materials for cast iron production contributes to the relevance of cast iron in modern applications. The primary raw material of cast iron is pig iron, which is itself a product of iron ore processing. It is rare for iron to exist in its pure form, and so it is commonly found as iron oxides. The iron oxides, which are referred to as iron ores, are initially converted to pig irons before conversion into various iron types. Since pig iron is very brittle due to its high carbon content, it has limited uses; converting it to cast iron is one way of increasing its uses. b. Production, fabrication and recycling The production of cast iron has been relatively easy and with modern technology it is even easier. This ferrous alloy is produced by re-melting the pig iron, combining it with elements (mainly silicon and carbon), and removing contaminants (or rather impurities). The iron is then cast through a technique that uses moulds. Fearn (2008) has explained that the use of moulds to produce cast iron products is still very efficient today. Sometimes burning the molten iron to remove sulphur and phosphorous also removes carbon, necessitating carbon replacement. The levels of silicon and carbon are adjusted according to the intended application of the cast iron. The excellent machinability property makes cast iron a suitable metal for fabrication. The grey cast iron contains graphite, which makes it easy to cut the iron. It is easily castable and is an excellent choice for making items of sophisticated shapes. Fearn (2008) has concurred that because of its good fluidity characteristic, cast iron is an excellent choice for making casting of items with complex shapes. Perhaps the recyclability of cast iron is one reason that it is still relevant today. The melting of the pig iron is often done together with scrap steel and iron, coke carbon, and lime stone (Leupen, 2006). It means that used cast iron can be put back in the production process of cast iron. The advantages recycling cast iron are substantial, including reduction of environmental pollution and availing raw materials c. Why cast iron is essential or preferable for a specific uses Cast iron is still preferable for a number of uses due to its appealing properties. It is used to produce cookware and cooking utensils because it is not only resistant to heat but it is also very durable. K. Budinski and M. Budinski (2007) have mentioned that cast iron is used to make cookware such as pans, pots and skillets so that when cured the cookware can add some iron into food. Cast iron is used to make inexpensive utensils such as spoons, and tongs, barbeque grills, and grill presses (Fearn, 2008). A study conducted by Takamori, Yoshiaki and Halada (2002) to determine the properties of aluminium and casting iron alloy revealed that cast iron properties are highly enhanced making suitable for manufacture of inexpensive and suitable drink cans. The durability and strength properties of cast iron have made the metal a suitable choice manufacturing items used in home, building constructions, and other structures. Cast iron is still used to make automotive parts, furniture, skillets, staircases and handrails, and door steps. Leupen (2006, p.53) has stated that cast iron columns are preferred over masonry walls in building constructions because they take less space while providing comparable strength to that provided by masonry walls. Cast iron is widely used to make door steps because it is heavy (Fearn, 2008, p.53). Even though its use in automotive and machine parts is declining, cast iron is still used in making gearbox cases, and engine cylinder heads and blocks. However, today, steel is preferred over cast iron for bridge constructions because it is stronger and more supple; cast iron is has low tensile strength (Leupen, 2006; McClelland, 1997, p.252). Cast iron is also preferred over plastic pipes because it reduces noises produced by water running in pipes. Plastic PVC pipes are limited by these noises and it is even worse when the running water is hot. Cast iron also has advantages over plastic because they are more environmentally friendly and not linked as a carcinogen. d. Economic consideration The price of cast iron is comparable to and sometimes better than that of various alternative materials, including steel, aluminium, and plastic PVC. Fearn (2008) has mentioned that cast iron products are less expensive than steel products. e. National and regional significance of cast iron Cast iron is valuable to any nation and region as a metal to support various industries, including building constructions, household and furniture, automotive and machines, utensils, and piping. It also can be a source of foreign income for a country or region producing it. The use of cast iron promotes recycling of steel and iron, contributing to the solutions of improving the environment. As in case of piping, it is an alternative to plastic PVC, which is noted as a cause of cancer (Fearn, 2008). It means that cast iron can save a nation from cost associated with cancer. 3. Conclusion Even though its usage is declining, cast iron is still used for a number of applications, including manufacture of automotive parts, pipes, home items, and building constructions. It is easily produced, fabricated and is recyclable. It is also inexpensive and beneficial to a country in terms of providing materials for various constructions. It recyclability is beneficial to the environment. References Budinski, G. K. & Budinski, M.K. (2007 ). Engineering materials properties and selection. (9th edn.). Upper Saddle River, New Jersey: Pearson. Fearn, J. (2008). Cast iron. Oxford, United Kingdom: Osprey Publishing. Leupen, B. (2006). Frame and generic space. Rotterdam, Netherlands: 010 Publishers. McClelland, P. D. (1997). Sowing modernity: America's first agricultural revolution. Ithaca, New York: Cornell University Press. Takamori, S., Yoshiaki, O., Halada, K. (2002). Aluminium-alloyed cast iron as a versatile alloy. Materials Transactions, 43(3): 311 – 314. Read More