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Cast iron


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Cast iron

  2. 2. IRON 2 INTRODUCTION: Out of all the metals, the iron is the most popular metal and it has been in the construction activity since pre historic times. Iron is a chemical element with the symbol Fe and atomic number 26 It is available in abundance and it is estimated that it constitutes about 4.60% of the crust of the earth. In latin, the iron is known as ferrum and its chemical designation is Fe. The metals are grouped in the two categories. 1.FERROUS METALS: The ferrous metals contains iron as their main constituent. There are three important ferrous metals, namely, cast iron, wrought iron and steel. 2.NON FERROUS METALS: non ferrous metals do not contain iron as their main constituent. Eg. Aluminium, copper etc.
  3. 3. 3 Iron OreIron Ore Blast FurnaceBlast Furnace Pig IronPig Iron Smelted, Hammered, Re- heated, Rolled Smelted, Hammered, Re- heated, Rolled Smelted,Alloyed, RolledSmelted,Alloyed, Rolled Wrought IronWrought Iron Cast IronCast Iron Mild Iron(Steel)Mild Iron(Steel) Re- melted, Poured into sand molds Re- melted, Poured into sand molds
  4. 4. 4 COMPARISON BETWEEN WROUGHT IRON ,CAST IRON& STEEL Wrought iron Cast Iron Steel Compositio n Purest Contains up to 0.25% C Crude form containing 2-4% C Midway Melting point 1500 degree Celsius 1200 degree Celsius 1300-1400 degree Celsius Hardness Cannot be hardened or tempered Hard, hardened by heating & sudden cooling Can be hardened & tempered Strength compressive strength is 2.0 tonnes/sq cm ultimate tensile strength 3.15 tonnes/sq cm Comp. strength 6.3-7.1 tonnes/sq cm Ultimate tensile strength 1.26 to 1.57tonnes/sq cm. Comp strength 4.75 -25.2 tonnes/ sq cm Ultimate tensile strength is 5.51 to 11.02 t /sq m
  5. 5. 5 Wrought iron Cast Iron Steel Rusting Rusts more than Cast Iron Does not rust easily Rusts easily Malleability&D uctility Tough, malleable, ductile & moderately elastic Brittle & cannot be welded or rolled into sheets Tough, malleable & Ductile Reaction to sudden shock Cannot stand heavy shocks Does not absorb shocks Absorbs shocks Welding Easily welded Brittle and cannot be welded or rolled into sheets Rapidly welded
  6. 6. 6 Wrought iron Cast Iron Steel Uses Costlier than mild steel so being replaced by the latter. Withstand shocks without permanent injury so used in chains, crane hooks and railway couplings For parts that rust easily like water pipes, sewers, drain pipes etc. Making such parts of machines as are not likely to be subjects to shocks or tension Lamp posts, columns and Used as reinforcement in R.B. & R.C.C. Used in making St. members, bolts, rivets and sheets (plain and corrugated) Making cutlery, files & machine tools
  7. 7. 7 CAST IRON Cast iron used in Door Cast iron used in Bolt-nuts Cast iron is the name given to those ferrous metals containing more than1.7 % carbon. It is similar in composition to crude pig iron as produced by the blast furnace. Its structure is crystalline and relatively brittle and weak in tension. Composition of Cast Iron: Carbon - 2.5 to 3.7% Silicon - 1.0 to 3.0% Manganese - 0.5 to 1.0% Phophorus - 0.1 to 0.9% Sulphur - 0.07 to 0.10% Introduction:
  8. 8. 8 BRIEF HISTORY Cast iron has its earliest origins in China between 700 and 800 BC and in Europe it was first known in the 14th century. Until this period ancient furnaces could not reach sufficiently high temperatures. The use of this newly discovered form of iron varied from simple tools to a complex chain suspension bridge erected approximately 56 A.D. Cast iron was not produced in mass quantity until fourteenth century A.D. In 1325 A.D. water driven bellows were introduced which allowed for a greater draft to be fed to the pit, thus increasing temperatures. The next significant development in cast iron was the first use of coke in 1730 by an English founder named Darby. Coke could be used more efficiently than coal, thus lowering the cost and time necessary to yield a final product.
  9. 9. 9 In 1885 Turner added ferrosilicon to white iron to produce stronger gray iron castings. In the later 20th century the major use of cast irons consisted of pipes, thermal containment units, and certain machine or building entities which were necessary to absorb continuous vibrations.
  10. 10. MANUFACTURING PROCESS 10 cast iron is manufactured by remelting pig iron with coke and limestone. this is done in a furnace known as cupola furnace. The raw materials are fed from the top The cupola furnace is worked intermittently and it is open at the top. After raw material is placed, furnace is fired and blast of air is forced. The blast of air is cold as the impurities in pig-iron are removed by the oxidation. The impurities of pig iron is removed and pure iron is taken in the molten stage from the bottom of furnace. CUPOLA FURNACE The slag is also removed from the top of the cast iron. At regular intervals. Molten cast iron are led into moulds of required shapes to form what we known as cast iron.
  11. 11. PROPERTIES OF CAST IRON 11 It is strong in compression but weak in tension. The tensile and compressive strengh of cast iron of average quality is 150N/mm² and 600N/mm² resp. It does not rust easily. If placed in salt water, it becomes soft.  low melting pont Good fluidity It is hard but it is brittle also. It is not ductile hence it cannot be adopted to absorb shocks and impacts. Its melting temperature is about 1250 C.⁰ It shrinks on cooling.
  12. 12. EFFECT OF COOLING RATE 12 Slow cooling favours the formation of graphite and low hardness. Rapid cooling promotes carbides with high hardness. Thick sections cools slowly, while thin sections cools down quickly. Sand moulds cools slowly but metal chills can be used to increase cooling rate and promotes white iron.
  13. 13. 13 Cast iron is used in a wide variety of structural and decorative applications, because it is relatively inexpensive, durable & easily cast into a variety of shapes. AppLICATIONs Construction of machines and structures (HighTensile Strength) As Columns,balusters & Arches (High Compressive Strength)  Machine and car parts like cylinder heads, blocks, gearbox cases, cookware, pipes, etc. (Good Castability) machines internal detailing ColumnsArches in bridgeSwing Machine
  14. 14. 14 Stoves and firebacks, Vehicles engine (High thermal conductivity and specific heat capacity) Car Engine Used for Decorative purposes: Stoves Cookware (Good fluidity,elasticity) Design made on column gate design Decorative pattern
  15. 15. 15 DIsADvANTAGEs: Cast Iron Weight Cast iron is very heavy, and consequently is mush harder to install than regular PVC/ABS sewer pipe. Brittleness It is quite brittle and if accidentally knocked will easily break. Brittleness in cast Iron Its strength and stiffness deteriorate when subjected to high heat, such as in a fire. weak in tension and bending, so can’t be used as beams Can’t overcome from Environmental causes Or can’t absorb sudden shocks Resistance towards heat
  16. 16. EARLy sTRuCTuRAL usEs OF IRON IN buILDINGs 16 Cast iron is used for structural element between late 1830’s to1910 Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp edge or flexibility is required. It is strong under compression, but not under tension Architecturally Cast-Iron used in two ways: 1.Structural use 2.Architectural use 1.Structural use 1.The best way of using cast iron for bridge construction was by using arches, so that all the material is in compression. Bridge
  17. 17. EARLy sTRuCTuRAL usEs OF IRON IN buILDINGs 17 Cast iron is used for structural element between late 1830’s to1910 Architecturally Cast-Iron used in two ways: 1.Structural use 2.Architectural use Cast iron was the metal of choice throughout the second 19th century. It was a fire resistance material Large facades could be produced at less cost. Iron buildings could be erected with speed and efficiency.
  18. 18. It was a prominent style in the Industrial Revolution era when cast iron was relatively cheap and modern steel had not yet been developed. 18 Structural use Cast iron has been used for centuries, and was used in architecture •It was in 18th century Britain that new production methods first allowed cast iron to be produced cheaply enough and in large enough quantities to regularly be used in large building projects. • •One of the first important projects was The Iron Bridge in Shropshire, a precedent setting structure made almost entirely of cast iron. • However, it was grossly over-designed, and the makers (principally Abraham Darby) suffered financially as a result. •The quality of the iron used in the bridge is not high, and nearly 80 brittle cracks are visible in the present structure. •Later designers and engineers, such as Thomas Telford improved both the design and quality of the material in his bridges (for example, at Buildwas upstream of Coalbrookdale) and aqueducts (such as the world-famous Pontcysyllte Aqueduct in North Wales.) Close up view of cast-iron detailing at the Ca' D'Oro Building in Glasgow, Scotland, erected in 1872
  19. 19. THE IRON BRIDGE • The Iron Bridge crosses the River Severn in Shropshire, England. • It was the first arch bridge in the world to be made of cast iron, a material which was previously too expensive to use for large structures. • Carries pedestrian traffic Crack and repairs in bridge Cracked supports
  20. 20. CONSTRUCTION • Being the first of its sort, the construction had no precedent; the method chosen to create the structure was therefore based on carpentry. • Each member of the frame was cast separately, and fastenings followed those used in woodworking, such as the mortise and tenon and blind dovetailjoints, adapted as necessary to the different properties of cast iron. • Bolts were used to fasten the half-ribs together at the crown of the arch. • Very large parts were needed to create a structure to span 100 feet rising to 60 feet above the river. • The largest parts were the half-ribs, each about 70 ft long and weighing 5.25 tons. • The bridge comprises more than 800 castings of 12 basic types. • The bridge was raised in the summer of 1779, and it was opened on New Year's Day 1781.
  21. 21. 21 Columns Roof Trusses Long span roof 2.Cast iron columns had the advantage of being slender, compared with masonry columns capable of supporting similar weight. Buildings 2.Architectural use As an Architectural metal, it gives architectural design& building technology, while providing a richness in ornamentation, much cheaper than stones.
  22. 22. 22 . Its use gradually spread from architectural elements like shutter and door frames to facades composed of closely spaced iron columns and spandrel panels to interior columns.
  23. 23. 23 FAILURE : Oxidation or rusting occurs rapidly when cast iron is exposed to moisture or air. The casting process also left flaws in the cast iron (such as blow holes, bubbles, imperfectly joined seams) that serve to concentrate stress in unpredictable ways. Common problems encountered with cast iron construction include Badly rusted or missing elements. Impact damage Structural failures Broken joints Damage to connections Loss of anchorage in masonry Steel was becoming available nationally, and was more versatile and cost competative.
  24. 24. Compositions of Cast iron 24 The cast iron contains about 2-4% of carbon. In addition it contains the various impurities such as manganese, phosphorous, silicon and sulphur. 1. MANGANESE: (Below 0.75%)  It makes cast iron hard and brittle.  Its amount should therefore be kept below 0.75% or so. 2. SULPHUR: (Below 0.10%)  It makes cast iron brittle and hard.  Does not allow smooth cooling in sand moulds.  Its presence causes rapid solidification of cast iron and it ultimately results in blow holes and sand holes.  Sulphur content should be kept below 0.10% 3. SILICON: (Below 2.5%)  It combines with part of iron and forms a solid solution. Removes combined carbon from graphite form. If its amount is less than 2.5%, it decreases shrinkage and ensures softer and better casting. 2.PHOSPHORUS: (0.3-1%) It increases fluidity and also makes it brittle. When its amount is more than 0.3% the resulting cast iron is lacking in toughness and workability. Its % is some times kept as about 1-1.5 to get very thin casting.
  25. 25. 25 Comparative table Name Nominal compositi on [% by weight] Form and condition Yeild Strength Tensile strength Ductility Hardness Uses Grey cast iron C :3.4,  Si:1.8, Mn: 0.5 Cast Low High Low Average Engine cylin der blocks,  flywheels, ge ars machine- tool bases White cast iron C :3.4,  Si :0.7,  Mn: 0.6 Cast (as cast)  Lowest Low Lowest Highest Bearing surfa ces Malleable iron C :2.5,  Si :1.0,  Mn :0.55 Cast  (annealed) High High High Lowest Axle bearing s, track  whee,Colum n, arches Ductile Iron C :3.4,  P :0.1,  Mn:0.4, Ni:1. 0, Mg :0.06 Cast  Highest Highest Highest Low Gears, camsh afts,  crankshafts
  27. 27. 1. WHite Cast iron 27  These are iron-carbon alloys having more than 2.11% carbon.  All the carbon is present in the combined cementite form, which makes the fracture of these alloys to have dull and white colour, and that is the reason of their name as white irons. Microstructure of White Cast Iron Composition: C=2.5%,Mn=0.4%, Cr=17%,Si=1.3%, Ni+Cu=1.5%,P=0.15%, S=0.15%,Mo=0.5%
  28. 28. properties of WHite Cast iron 28 Hard and wear resistant The hardness and brittleness increases as the carbon content increases. Hardness Brinell 375 to 600. Tensile strength 20000 to 70000 psi. Compressive strength 200000 to 250000. limitations Because of extreme brittleness and lack of machinability, white irons find  limited engineering applications.
  29. 29. 2929 appliCations Used to Make Malleable Iron Malleabilize To Increase Ductility White Cast Iron  Malleable Cast Iron→ Liners For Cement Mixers, Ball Mills, Certain Types Of Drawing Dies Extrusion Nozzles (abrasion resistance) Liners For Cement Mixers Ball Mills Nozzles  In furnitures (Wear resistant) Toughness Decorated furnitures
  30. 30. 2. Grey Cast iron 30 Iron-carbon alloys containing flakes of graphite embedded in steel matrix, which show a gray-blackish coloured fracture due to graphite’—the free foam of carbon, are called gray cast irons. The strength of gray iron depends on the strength of steel matrix and the size and character of graphite flakes in it. Microstructure of Gray Cast Iron A typical feature of gray iron is that graphite is in the form of flakes in microstructure. COMPOSITION: Total carbon : 2.4—3.8% Silicon : 1.2—3.5% Manganese : 0.5—1.0% Sulphur : 0.06—0.12% Phosphorus : 0.1—0.9%
  31. 31. properties of Grey Cast iron 31 1. Low cost of production 2.Low melting point: (1150°—1250°C) of cast irons, several hundred degrees less than  steel. 3. Good Castability: Cast irons have excellent fluidity and take good mould-impressions  easily. Graphite having low density is voluminous. Its large volume compensates for the  shrinkage. Gray iron, thus, does not need shrinkage allowance at all to take almost exact  casting impressions. 4. Good machinability of gray cast iron  is  due  to  easy  and  discontinuous  chip  formation due to brittle graphite flakes.  Graphite serves as a solid lubricant decreasing coefficient of friction.  It  smears  the  cutting  tool  allowing  free  sliding  of  chips  increasing  thus,  tool  life  too.  (White cast irons, due to high hardness, are unmachinable).
  32. 32. 32 5. Good wear resistance of gray iron is due to graphite acting as solid lubricant layer,  avoiding thereby metal to metal direct contact. On other hand, white cast irons are wear  resistant due to’ their high hardness. 6. High damping capacity is due to the graphite flakes, which breaks the continuity of  the metallic matrix, and thus, vibrations are not allowed to transfer from one side of  flake  to  other,  i.e.,  graphitic  cracks  quickly  dampen  the  vibrations  and  resonance  oscillations. Gray iron suits thus the machine beds as compared to steels. 7. High compressive strength of gray iron- almost 3 to 5 times of its tensile strength  (110-350 N/mm2), and almost equal to that of steels makes it suitable for applications,  where components are subjected to compression such as machine beds, etc. 8. High thermal conductivity, and have ability to withstand thermal shocks. 9.Good resistance to atmospheric corrosion  due to  high  silicon  and  perhaps other  factors, than mild steels. 10. Notch-insensitive: Large number of flakes in gray iron acts as notches  in spite of  these notches, if gray iron has the required strength, then additional notch or notches  shall have minor, or no effect, i.e., gray iron is  notch-insensitive; whereas in steels. A  notch  has  quite  a  damaging  effect  as  it  acts  as  stress-raiser  to  make  the  steel  even  brittle.   
  33. 33. 33 appliCations Internal Combusion Engine Pump Housings Valve Bodies Electrical Boxes Decorative Castings Cast iron cookware Disc brake (High thermal conductivity and specific heat capacity) (Low Tensile Strength) Internal combustion engine Pump Housings disc brake on a carCast iron cookware (Good Castability) Decorative pattern
  34. 34. 3. Malleable cast iron 34 Malleable iron is cast as White iron, the structure being a metastable carbide in a pearlitic matrix. Microstructure of Malleable Iron Components Percentage Carbon 2.00-2.65 Silicon 0.90-1.40 Manganese 0.25-0.55 Phosphorus Less than 0.18 Sulphur 0.05 Composition of Malleable Iron Graphite in nodular form Produced by heat treatment of white cast iron Graphite nodules are irregular clusters Similar properties to ductile iron.
  35. 35. properties 35 Similar to ductile iron Good shock resistance Good ductility Good machineability
  36. 36. applications  Malleable iron is better for thinner castings  Vehicle components – Power trains, frames, suspensions and wheels – Steering components, transmission and differential parts, – connecting rods  Railway components  Pipe fittings (Good Tensile Strength) (High ductility) Rail tracks Pipe fittings (Good Machinability) Power trains wheels Steering components in car
  37. 37. 4. Ductile (noDule ) cast iron 37 In ductile irons, the graphite is in the formof spherical nodules rather than flakes (as in grey iron), thus inhibiting the creation of cracks and providing the enhanced ductility. Also known as spheroidal graphite (SG), and nodular graphite iron. COMPOSITION: A TYPICAL CHEMICAL ANALYSIS OF THIS MATERIAL IRON CARBON 3.3 TO 3.4% SILICON= 2.2 TO 2.8% MANGANESE 0.1 TO 0.5% MAGNESIUM 0.03 TO 0.05% PHOSPHORUS 0.005 TO 0.04% SULPHUR 0.005 TO 0.02% Microstructure of Ductile Iron
  38. 38. properties 38 Strength higher than grey cast iron Ductility up to 6% as cast or 20% annealed Low cost Simple manufacturing process makes complex shapes Machineability better than steel
  39. 39. 39 applications  Pipe and pipe fittings Major industrial applications include --highway diesel trucks, --agricultural tractors, --oil well pumps. – Crankshafts, – front wheel spindle supports, – steering knuckles, – disc brake callipers used for water and sewer lines. Pipes (High strength) Machinery products: Tracters spindle (Good Machinability) oil well pumpsCrankshafts in motor engine disc brake callipers
  40. 40. Market survey 40
  41. 41. 41 size ½” ¾” 1” 1 1/4” 1 ½” 2” 2 ½” 3” 4” 6” weight 15mm 20mm 25mm 32mm 40mm 50mm 65mm 80mm 100m m 150m m Ball valve 281 436 585 960 1497 2287 Multip urpose gas ball valve 556 796 1182 1670 2565 3809 b.V with inbuilt straine r 993 1329 1848 Spring loaded, uni directio nal 391 572 859 1221 1826 2470 Ball valve 14M 6397 9102 1538 4
  42. 42. 42 size ½” ¾” 1” 1 1/4” 1 ½” 2” 2 ½” 3” 4” 6” weight 15m m 20m m 25m m 32m m 40m m 50mm 65mm 80mm 100m m 150m m Butterfly handle 281 436 585 Gas ball valve 628 Mini ball valve 395 Non return valve 364 489 761 Ball valve (with flexible connection) 714 Right angle mini ball valve 453 (15 mm Male x 8mm Nozzle)
  43. 43. unik 43