Uses Of Various Steel InCivil EngineeringBY:- Engr. Ahmad Sameer NawabKardan University Kabul, Afghanistan
METALS Metals are the backbone of all engineering projects and products.Various metals are used in one form or the other. Metals are foundas compounds like oxides, sulphates, carbonates, phosphates etc.in nature. These compounds are known as ores. Ores are treated to removethe impurities and get the metal .
•Metals are… Solid at room temperature,except mercury, which is liquid•Metals have… very high melting point.•Metals are… shiny when they cut.•Metals are… good conductors of heat andelectricity.•Metals are… usually strong & malleable sothey can be hammered intoshape.METALS CHARACTERISTICS
METALSFerrous Non-Ferrous AlloysContaining iron & Do not contain iron. A mixture ofalmost all are e.g. aluminium, metals, or amagnetic. copper, silver, gold, metal & smalle.g. mild-steel, lid, tin etc. amount ofcast-iron, tool- other substanceSteel etc.Ferrous Alloys Non-Ferrous Alloyse.g. e.g. brass (copper + zinc)stainless steel bronze (copper + tin )steel + chromium
OCCURRENCE OF IRON Iron is never available pure in nature. It has to beextracted in the form of pig iron from the various ironores. Pig iron is the crudest and wrought iron is the purestform of iron. The ores from which iron is extracted are:i. Magnite : it contains 70 to 75% iron.ii. Haematite : It has about 70% iron.iii. Iron Pyrites: It has about 47% iron.iv. Siderite: It contains 40% iron
PIG IRON To remove impurities from the iron ore carbon and flux are addedwhile melting it. The refined product so obtained is the crudest form of iron and iscalled pig iron. It is cast into rough bars called pigs.Properties: It is hard and brittle as such it is neither ductile nor malleable. It is difficult to bend. It melts easily. The fusion temperature is 1200 o C.
PIG IRON It can be hardened but not tempered. It can be magnetized. It has very high compressive strength but very weak intension. It does not rust. It cannot be welded.USES: cast iron, wrought iron and mild steel are obtainedby refining the pig iron. Because of its high compressivestrength it is used in columns, base plates, doorbrackets , wheel and pipe work.
CAST IRON Pig iron is remelted with limestone and coke and pouredinto moulds of desired shapes and sizes to get purerproduct known as cast iron. Moulding remelted pig iron removes impurity and gives amore uniform product, Carbon contents in cast iron vary from 2 to 4.5%.
CAST IRONPROPERTIES: Its structure is coarse crystalline and fibrous. Freshly fractured surface has grayish white appearance. It is brittle. It cannot withstand shocks and impacts. It cannot be welded. It cannot be magnetized. It does not rust. It is fairly hard and cannot be worked with a hand file.
CAST IRONUSES: It is used for casting, rain water pipes, gratings, railings,balustrades( staircase side railing). Because of high compressive strength it is used inmaking columns, supports for heavy machinery, carriagewheels etc. It is the basic material for the manufacturing of Wroughtiron and steel.
WROUGHT IRON If all the carbon and other elements in pig iron areoxidized and may be left with 0.25 percent of carbonthen we obtain wrought iron. It is by far the purest form of iron in which the totalimpurities do not exceed 0.5%.PROPERTIES: Its structure is fibrous and has silky luster. It is ductile and malleable. It is tough and can withstand shocks and impact betterthan cast iron.
WROUGHT IRON It can be forged and welded. It rusts easily It is unaffected by saline water. It cannot be permanently magnetized.USES :It is used in making roofing sheets, corrugatedsheets, rods, gas and water pipes, boiler tubes andornamental iron works such as grills gates and railingand window guards.
STEEL The essential difference between cast iron and steel isthe amount of their carbon contents. Steel goes on becoming harder and tougher with theincrease in its carbon contents. Up to a content of 1.5% all the carbon gets intochemical combination with iron and none of its exist infree state. If carbon contents increase beyond 1.5% then it doesnot combine with iron and is present as free graphite. Atthis stage metals falls in a category of cast iron.
STEEL For a material to be classified as steel there should beno free graphite in its composition. If there is any free graphite in it then it falls in thecategory of cast iron.
CLASSIFICATION OF STEEL Depending upon carbon content steel is classified intofollowing categories.Steel Carbon content1. Dead steel < 0.15%2. Mild steel 0.15 to 0.3%3. Medium carbon steel 0.3 to 0.8%4. High carbon steel 0.8 to 1.5%High carbon steel with carbon percentage over 1% is alsoknown as cast steel or carbon tool steel
MILD STEEL Steel where carbon content is 0.15 to 0.3% is calledmild steel, low carbon steel or soft steel. It is ductile and malleable. It is more tough and more elastic than wrought iron andcast iron. It corrodes easily. It is equally strong in tension and compression.
MILD STEEL(USES)1. In construction work it is chiefly used as rolled structuralsections like I-section, T-section, angle iron.2. Mild steel round bars are extensively being used asreinforcement in reinforced cement concrete.3. Plain and corrugated sheets of mild steel are used as roofcovering.4. It is also used in the manufacturing of various tools andequipments, for rail track, transmission towers and industrialbuilding.
HIGH CARBON STEEL In this steel the carbon contents is between 0.55 to1.5%. High percentage of carbon in it renders it harderand tougher. It is more tough and elastic then mild steel. Comparatively it is more stronger in compression than intension. It withstand shocks and vibrations
HIGH CARBON STEEL1. It is used in making tools such as drills, files andchisels.2. Fine quality of cutlery is made of high carbon steel.3. It is used to manufacture those parts of machinery thatneed a hard, tough, durable material capable ofwithstanding shocks and vibration
HIGH TENSION STEEL It is essentially a low carbon steel and the percentage ofcarbon is kept lesser than 0.15%. It is also termed ashigh tension steel. Because of increase tensile strength, lesser weight of itused, as compared to mild steel at the same job. Thestructure thus becomes lighter. It withstand atmospheric corrosion better. It is tougherand more elastic. It is more brittle and less ductile thenmild steel. High tension steel wires are extensively used inreinforcing prestressed concrete structures.
REINFORCING STEEL Plain cement concrete being strong in compression butweak in tension. Mild steel or high tension steel is embedded asreinforcement in the concrete to make it stronger intension. Though flats and square bars can be used asreinforcement yet the round bars are extensively usedfor the purpose