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STEEL PLATE AND SECTIONS

STEEL PLATE AND SECTIONS. by GROUP-E MEMBERS 1 JUDE RINALDO 2 JUDE PRADEEP 3 AARYL D ’ SA 4 SWAROOP SUNDER.

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STEEL PLATE AND SECTIONS

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  1. STEEL PLATE AND SECTIONS by GROUP-E MEMBERS 1 JUDE RINALDO 2 JUDE PRADEEP 3 AARYL D’SA 4 SWAROOP SUNDER

  2. Describe the three processes used for the manufacture of steel? Explain the common properties of steel that is commonly used today and state the importance of various grades of steel and aluminium alloys

  3. STEEL • steel is the basic shipbuilding material in use today • Steel may be regarded as an iron-carbon alloy, usually containing other elements. There are three particular processes currently used for the manufacture of steel: • Open-hearth process • Oxygen or basic oxygen process( BOS process) • Electric furnace process In all these processes the hot molten metal is exposed to air or oxygen, which oxidizes the impurities to refine the pig iron into high quality steel

  4. Open-hearth process • The open-hearth uses a type of furnace called a regenerative furnace • Instead of a firebox at one end and a flue at the other, it has devices at each end for the intake and outflow of both fuel and air. • The air is preheated by a system of current reversals that causes very high temperatures

  5. Open-hearth process

  6. Open-hearth process Process • In the furnace, which has a wide, saucer-shaped hearth and a low roof, molten pig iron and scrap are packed into the shallow hearth and heated by overhead gas burners using preheated air • Fires blazed at both sides of the hearth, passing heated currents of air and gas alternately from each fire over the molten iron. • The waste gas passed into chambers above the two fires, trapping heat in special firebrick and making the next flow of gas even hotter. • The extreme heat eventually burned out the impurities in the iron, resulting in silvery white steel.

  7. Oxygen or basic oxygen process • The primary raw materials for the BOP are 70-80% liquid hot metal from the blast furnace and the balance is steel scrap. • These are charged into the Basic Oxygen Furnace (BOF) vessel. Oxygen ( pure) is "blown" into the BOF at supersonic velocities. • It oxidizes the carbon and silicon contained in the hot metal liberating great quantities of heat which melts the scrap. • The product of the BOS is molten steel with a specified chemical analysis at 2900°F-3000°F. • From here it may undergo further refining in a secondary refining process or be sent directly to the continuous caster where it is solidified into semi-finished shapes: blooms, billets, or slabs.

  8. Electric furnace process • The electric are furnace (EAF) is the principle furnace type for the electric production of steel. • The primary application of the EAF is for the re-melting of steel scrap. • however, EAF’s can be charged with limited amounts of iron scrap, pig iron, and direct reduced iron. • With 100% of the charge coming from scrap it is difficult to control the purity and quality of the steel produced • manufacturers centered on EAF steel production have concentrated on market segments where steel quality is not as critical.

  9. Properties of steel The main properties can be classified as: • Tensile strength • Ductility • Hardness • Toughness

  10. Properties of steel • Tensile strength • It is a measure of the material’s ability to withstand the loads upon it in service. • Terms such as stress, strain, ultimate tensile strength, yield stress and proof stress are all different methods of quantifying the tensile strength of the material. • This is the main single criterion with reference to metals The two factors affecting tensile strength of steel are: • Carbon content of the steel • Heat treatment following manufacture

  11. Properties of steel • Ductility • This is the ability of a material to undergo permanent changes in shape without rupture or loss of strength. • It is particularly important where metals undergo forming processes during manufacture

  12. Properties of steel • Hardness • this is a measure of the workability of the material • It is used as an assessment of the machinability of the material and its resistance to abrasion

  13. Properties of steel • Toughness • This is a condition midway between brittleness and softness • It is often quantified by the value obtained in a notched bar test

  14. Various grades of steel • The various grades of steel that have been developed constitute the best available materials for hull construction • Depending on the features provided there are five grades of mild steel(A-E) designated by the societies • A special grade mark “H” is used by the classification societies to denote higher tensile steel • The steel for ship construction must be manufactured under approved conditions, and inspected, and prescribed tests must be carried out on selected specimens • Advance in steel production and alloying methods have resulted in good higher strength steel for ship construction Benefits arising from the use of these steels in ship construction include reduced structural weight Larger unit fabrications are possible for the same weight, and hence, less welding time

  15. Various grades of steel Some of the various grades of steel commonly used today are: • Traditional/ Original Japanese steel • AISI/American 1050/10xx • AISI/American 5160 • A2 Tool Steel • D2 Tool Steel • S-5 Steel • S-7 Steel • CK55 Krupp Steel • 50CRV4 • 420, 440A, 440B, 440C, 440V, ATS-34

  16. ALUMIINIUM ALLOYS • They have a particular applications in the construction of superstructures, especially on passenger ships • The increasing use of aluminium alloy has resulted from its several advantages over steel • The use of aluminium alloys in a structure can result in reduction of 60% of the weight of an equivalent steel structure This reduction in weight, particularly in the upper regions of the structure, can improve the stability of the vessel. This follows from the lowering of the vessel’s centre of gravity, resulting in an increased metacentric height

  17. ALUMIINIUM ALLOYS • The corrosion resistance of aluminium is very good • The properties required of an aluminium alloy to be used in ship construction are much the same as for steel • They can be formed into unusual shapes to suit particular applications some of the alloys of aluminium are: • AL-Li ( Lithium ) • Alumel (Nickel ) • Duralumin ( copper ) • Magnox ( magnesium oxide ) • Zamak ( zinc,aluminium,magnesium,copper )

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