Write on the following building materials * Steel * Cast iron * Aluminium * Pipes used in building construction * Light roofing materialsConsidering the following; * Definition * Sources * Types * Uses * Advantages/disadvantages * Limitation
STEEL AS A BUILDING MATERIAL
Steel is a structural material which consists mostly of iron and carbon. It can, however, contain other additives which might change the steel's properties. Steel can be hot rolled or cold formed into structural shapes, such as the familiar "I" beam. Steel has the same strength in tension as it has in compression, unlike concrete. The use of steel structures permits designers to experiment with many architectural forms and artistic expression which are more difficult to build in conventional concrete framed structures. With steel, more challenging and creative designs can now be considered leading to buildings that are aesthetically distinctive and if high build quality. A steel building is a metal structure with steel for the cladding and internal support. Such buildings are used for a variety of purposes including storage, office space and living space. Steel is 100% recyclable material without degradation and its recycling rate can go up to beyond 60% for the constructional steel in some countries. It is important to note that; constructional steel must be continuously promoted as a strong alternative building material in the global construction market in order to convince building owners, the design community and building contractors to build in steel against the other traditional building systems.
SOURCES OF STEEL
Steel requires the mining of iron ore, coal, limestone, magnesium, and other trace elements. To produce steel, iron must first be refined from raw ore. The iron ore, together with limestone and coke (heat-distilled coal) are loaded into a blast furnace. Hot air and flames are used to melt the materials into pig iron, with the impurities (slag) floating to the top of the molten metal. Steel is produced by controlling the amount of carbon in iron through further smelting. Limestone and magnesium are added to remove oxygen and make the steel stronger. A maximum carbon content of 2% is desired. Other metals are also commonly added at this stage, to produce various steel alloys. These metals include magnesium, chromium, and nickel, which are relatively rare and difficult to extract from the earth’s crust. The molten steel is either moulded directly into usable shapes or milled.
TYPES OF STEEL
According to varying carbon content
* Dead Mild Steel (Less than 0.15 % Carbon )
* Mild Steel (0.15 – 0.30 % Carbon)
* Medium Carbon Steel (0.30 -0.80 % Carbon)
* High Carbon Steel (0.80 -1.50 % Carbon)
* Cast Steel / Carbon Tool Steel (More than 1.50 % Carbon) Properties and Uses of Mild Steel
1. Ductile & malleable, More tough and more elastic than cast iron and wrought iron 2. More prone to rusting than wrought iron, Corrodes quickly, Easily forged, welded & riveted, Withstands shocks & impacts well, Not much affected by saline water 3. Equally strong in tension, compression and in shear, Difficult to harden and temper Sp. Gravity 7.8 4. Used as rolled structural sections like I-section; T-section; channel Section; angle irons. Plates round and square rods 5. Mild steel Round bars used as reinforcement and Mild steel tubes are used in structures 6. Plain and Corrugated mild steel sheets are used in roofing Properties and Uses of Medium Carbon Steel
1. Granular structure, More tough & elastic than mild steel , Easier to harden & to temper 2. More difficult to forge and to weld, Stronger in compression than in tension or in shear, Withstands shocks and vibrations better 3. Used for making tools such as dills, files, chisels and for making those parts that are hard , tough and...
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