Metals-Ferrous and Non Ferrous

2. Metals-Ferrous and Non Ferrous By Engr. Prof. Dr. Attaullah Shah

3. Ferrous Metals. • Ferrous is an adjective used to indicate the presence of iron. • The word is derived from the Latin word ferrum "iron"). • Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel). • The term non-ferrous is used to indicate metals other than iron and alloys that do not contain an appreciable amount of iron • All forms of iron and steel / manufactured to meet wide variety of specification • Chemical composition & internal structure is highly controlled during manufacturing. • Good strength and hard. Fabricated in shops to desired size & shape • Good quality control during manufacturing

4. Brief History: Iron age (12th century BC) (mostly wrought iron) – weapons made with inefficient smelting methods. The best weapons? When iron combined with carbon! Became more common after more efficient production methods were devised in the 17th century. With invention of the Bessemer process in the mid-19th century, steel became a relatively inexpensive mass-produced good

5. IRON • Basic constituent of steel. • Most abundant metallic in the earth’s crust after aluminum • Found in the form of ores as oxides, carbonates, silicates & sulfides • Produced in blast furnaces. • It can be produced into 3 commercial forms that is: a) wrought iron b) steel c) cast iron • Increase in the amount of carbon decreases the melting point of the metal. • Carbon exerts the most significant effects on the microstructure and properties of iron products.

6. Iron Ores • Iron ores are rocks and minerals from which metallic iron can be economically extracted. • The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. • The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3). • Hematite is also known as "natural ore", a name which refers to the early years of mining, when certain hematite ores containing up to 66% iron could be fed directly into iron-making blast furnaces. • Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. • 98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil.

7. Pig Iron • Pig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel. • Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications. • The Chinese were making pig iron by the later Zhou Dynasty (1122–256 BC). • An ingot is a material, usually metal, that is cast into a shape suitable for further processing.

8. WROUGHT IRON • Manufactured by melting & refining iron to a high degree of purity. • Then, molten metal is poured into a ladle and mixed with hot slag. • The fluxing action of the slag causes a spongy mass to form which is processed by rolling & pressing. • It is only iron-bearing material containing slag.

9. It’s a low carbon steel (less than 0.1% carbon by weight) containing a small amount of slag, usually less than 3%. • It contains small amount of manganese (less than 0.1%) and silicon (0.2%). • It’s ductility is lower than steel. • It’s tensile strength is lower. • It can be molded easily and has good resistance to corrosion. • It is used to make pipes, corrugated sheets, grills, bars, chains and other products.

10. It can be cold worked, forged and welded like steel. • Forging is working a metal to predetermined shape by one or more processes such as hammering, pressing and rolling at a temperature above the re-crystallization temperature. • Cold working is the process of working at a temperature that doesn’t alter the structural changes caused by the work or that is below the re-crystallization temperature. • Wrought iron is used extensively where corrosion resistance is needed.

11. Wrought Iron Gate & Wrought Iron Fence

12. Wrought Iron Rack

13. CAST IRON • Manufactured by reheating pig iron (in a cupola) and blending it with other material of known composition. • Alternate layers of pig iron (with or without scrap steel) and coke are charged into furnace. • Limestone is added to flux the ash from the coke. • Heat necessary for the smelting is supplied by the combustion of coke and air supplied by the blast. • Cupola function to purify iron and produce a more uniform product. • When sufficient metal is accumulated at the bottom of the furnace, it is tapped.

14. Composed primarily of iron, carbon and silicon • Shaped by being cast in a mold • It has the greatest amount of carbon • Basically, the amount and form of carbon could affect the strength, hardness, brittleness and stiffness of cast iron. • Adding carbon to iron increases its hardness and strength but lowers the ductility. • Cast iron has high compressive strength but its tensile strength is low. There are 2 types of cast iron that is: a) Gray Cast Iron b) White Cast Iron

15. Cast Iron Teapot Cast Iron Pots

16. Cast Iron Bench

17. GRAY CAST IRON • “Gray Cast Iron” also known as ordinary ast iron owing to the color of fracture. • It contains free carbon (graphite flakes) that makes the metal weak and soft. • Contains high carbon content and large numbers of graphite flakes. • The flakes gives a gray appearance to a fractured surface • most widely used cast iron • Have poor ductility

18. Advantages of cast iron are as follows:a) Cheap b) Low melting pointc) Fluid – easy to cast, especially advantageous into large complex shapes. d) Excellent bearing propertiese) Excellent damping properties (ability to absorb noise and vibration) g) Can be heat threatenedh) Can be alloyed

19. White Cast Iron • “White Cast Iron” is called in such name due to the fracture surface that has a silvery white metallic color. • Carbon is combined chemically with iron in the form of cementite that makes this metal strong, hard and brittle. • harder and more resistant to wear from abrasion compared to gray iron. • Excellent wear resistance • High compressive stress

20. White Cast Iron Daybed

21. Steel Products Steel – alloy consisting mostly of iron with a little carbon (0.2% - 2.04% by weight) Cast iron = carbon content between 2.1% - 4.0% Iron = iron-carbon alloy with less than 0.005% carbon. Wrought iron – contains 1 – 3% by weight of slag in the form of particles elongated in one direction – more rust resistant than steel and welds better

22. Steel • Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. • Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron. • Steel is an alloy of iron and carbon. Pure iron’s strength remarkably increases when alloyed with carbon. The tensile strength increases with increasing carbon content but the ductility reduces. Steel having its properties because of the presence of carbon alone is called “Plain carbon steel”

23. Types of Plain Carbon steel • Low carbon steel or mild steel: • The carbon content does not increases 0.25% • Soft and ductile • mostly used for construction purpose • Uses ► Sheets, rods, wires, pipes, hammers, chains, shafts et • Medium-carbon steel : • The carbon content is 0.25 to 0.5 % • Stronger than the mild steel slightly less ductile • Uses ► Shafts, connecting rods and rails etc • High- carbon steel : • Carbon content is above 0.5% • Harder and stronger than mild steel and medium carbon steel • Uses ► Keys, knifes, drills etc

24. The “abc’s” of Steel Making: Raw Material: Carbon in the form of coke Iron ore (Fe2O3) Limestone (CaCO3) Air (lots of it!!)

25. The “abc’s” of Steel Making: Coke Solid residue product from the destructive distillation of coal. About 80 to 95% C. Made by heating black coal in small ovens at 300 C for 24 hours in a coke plant.

26. The “abc’s” of Steel Making: The iron ore Consists of oxides in nature of iron and oxygen Primarily magnetite (Fe3O4) or hematite (Fe2O3) The blast furnace basically separates the iron from the oxygen in a reduction process Mined primarily in Australia, Brazil and Canada.

27. The “abc’s” of Steel Making: The limestone Acts as a flux – converts impurities in the ore into a fuse able slag

28. The “abc’s” of Steel Making: Air Preheated by fuel gas from the coke ovens to about 1000 C. Delivered to the blast furnace at 6,000 m3/min Passes through furnace and burns the coke to produce heat required and also generates the carbon monoxide.

29. The “abc’s” of Steel Making: Typical blast furnace: 1.6 tons of iron ore 0.18 tons of limestone 0.6 tons of coke 2 -3 tons of preheated air

30. The “abc’s” of Steel Making: Step 1 – The Blast Furnace: Stands 300 feet tall Designed to run continuously for 4 -5 years before being relined. Heat generated by burning coke in the preheated air. Coke acts as reducing agent and changes to carbon monoxide (the reducing agent) which removes the oxygen from the iron oxide.

31. The “abc’s” of Steel Making: Step 1 – The Blast Furnace: Four primary zones – the bottom zone (zone 4) reaches temperature of 1800 C – this is where iron is tapped off. The top zone (zone 1) – where coke is burned and moisture driven off. Zone 2 – slag coagulates and is removed.

32. The “abc’s” of Steel Making: Step 1 – The Blast Furnace: Two important chemical reactions: Oxidation of the carbon from coke: • Reduction of iron ore:

33. The “abc’s” of Steel Making: Step 1 – The Blast Furnace: Products from the blast furnace: Iron stored in steel shelled ladles Pig iron (brittle w/ 4% carbon)

34. Step 2: Manufacturing of Steel from Iron Two common methods: Bessemer Furnace = Ingots = molten steel poured into molds to create ingots which then go through forging press and roughing mill to create billet, bloom or slab, OR: Continuous cast – continuous process to again create a billet, bloom, slab or “as cast semis”

35. Step 2 – The Bessemer converter: Used for REFINEMENT: Takes pig iron with high C content and removes C. Removes impurities such as Si and Mn (via oxides) Much smaller furnace (vs. Blast furnace) Lowered cost of steel making Poured into molds to form ingots Replaced by basic oxygen process and electric arc furnace.

37. Steel Ingots

38. Heat treatment of Steel: • To develop steel of particular structure or conditions best suited for particular work. • Basis of heat treatment: • At certain temperature called critical temperature, all alloys undergo reversible constituent change or inversions. • At heating the critical point differs from that in the cooling. • Holding of material at elevated temperature may help it to establish equilibrium of constituents. • Slow cooling from an elevated temperature above critical point permits natural constitutional change. • Rapid cooling or quenching completely inhibits the natural change and so tends to retain the particular structure.

39. Heat Treatment process of steel. • Hardening process: • The degree of hardness of steel depends on proportions of these three forms: • For steel containing less than 0.85% carbon, the hardening temperature must be above 885C0 to ensure that ferrite is dissolved. • In case of steel having more than 0.85% of Carbon, comentite itself is very hard and needs temperature slightly above 730C0 • For steel with very low carbon, to harden the steel. • Quenching: • Rapid Cooling: • Tampering: • When a piece of steel is hardened by heating above the critical range and then quenched, it is too hard for practical purpose. • Drawing: • At comparatively higher temperature and below critical temp, the steel is drawn and cooled softens steel. • Annealing: • Heating above the critical Temp, and then very slowly cooling it making it more ductile and tough. • Normalizing: • Steel is heated above the critical Temp but cooled rapidly, which refines the grains of the steel.

40. Steel Products: • Steel is marketed in a wide variety of sizes and shapes, such as rods, pipes, railroad rails, tees, channels, and I-beams. • These shapes are produced at steel mills by rolling and otherwise forming heated ingots to the required shape. The working of steel also improves the quality of the steel by refining its crystalline structure and making the metal tougher. • The basic process of working steel is known as hot rolling. In hot rolling the cast ingot is first heated to bright-red heat in a furnace called a soaking pit and is then passed between a series of pairs of metal rollers that squeeze it to the desired size and shape. The distance between the rollers diminishes for each successive pair as the steel is elongated and reduced in thickness.

41. The first pair of rollers through which the ingot passes is commonly called the blooming mill, and the square billets of steel that the ingot produces are known as blooms. From the blooming mill, the steel is passed on to roughing mills and finally to finishing mills that reduce it to the correct cross section. The rollers of mills used to produce railroad rails and such structural shapes as I-beams, H-beams, and angles are grooved to give the required shape. • Modern manufacturing requires a large amount of thin sheet steel. Continuous mills roll steel strips and sheets in widths of up to 2.4 m (8 ft). Such mills process thin sheet steel so rapidly, before it cools and becomes unworkable. A slab of hot steel over 11 cm (about 4.5 in) thick is fed through a series of rollers which reduce it progressively in thickness to 0.127 cm (0.05 inc) and increase its length from 4 m (13 ft) to 370 m (1210 ft).

42. Continuous mills are equipped with a number of accessory devices including edging rollers, de-scaling devices, and devices for coiling the sheet automatically when it reaches the end of the mill. The edging rollers are sets of vertical rolls set opposite each other at either side of the sheet to ensure that the width of the sheet is maintained. De-scaling apparatus removes the scale that forms on the surface of the sheet by knocking it off mechanically, loosening it by means of an air blast, or bending the sheet sharply at some point in its travel. The completed coils of sheet are dropped on a conveyor and carried away to be annealed and cut into individual sheets.

43. A more efficient way to produce thin sheet steel is to feed thinner slabs through the rollers. Using conventional casting methods, ingots must still be passed through a blooming mill in order to produce slabs thin enough to enter a continuous mill. By devising a continuous casting system that produces an endless steel slab less than 5 cm (2 in) thick, German engineers have eliminated any need for blooming and roughing mills. In 1989, a steel mill in Indiana became the first outside Europe to adopt this new system.

44. Pipe Cheaper grades of pipe are shaped by bending a flat strip, or skelp, of hot steel into cylindrical form and welding the edges to complete the pipe. For the smaller sizes of pipe, the edges of the skelp are usually overlapped and passed between a pair of rollers curved to correspond with the outside diameter of the pipe. The pressure on the rollers is great enough to weld the edges together. Seamless pipe or tubing is made from solid rods by passing them between a pair of inclined rollers that have a pointed metal bar, or mandrel, set between them in such a way that it pierces the rods and forms the inside diameter of the pipe at the same time that the rollers are forming the outside diameter.

45. Tin Plate By far the most important coated product of the steel mill is tin plate for the manufacture of containers. The “tin” can is actually more than 99 percent steel. In some mills steel sheets that have been hot-rolled and then cold-rolled are coated by passing them through a bath of molten tin. The most common method of coating is by the electrolytic process. Sheet steel is slowly unrolled from its coil and passed through a chemical solution. Meanwhile, a current of electricity is passing through a piece of pure tin into the same solution, causing the tin to dissolve slowly and to be deposited on the steel. In electrolytic processing, less than half a kilogram of tin will coat more than 18.6 sq m (more than 200 sq ft) of steel.

46. For the product known as thin tin, sheet and strip are given a second cold rolling before being coated with tin, a treatment that makes the steel plate extra tough as well as extra thin. Cans made of thin tin are about as strong as ordinary tin cans, yet they contain less steel, with a resultant saving in weight and cost. Lightweight packaging containers are also being made of tin-plated steel foil that has been laminated to paper or cardboard. Other processes of steel fabrication include forging, founding, and drawing the steel through dies.

48. Figure 9-12: processing of refined steel into products.

49. F 9-13 – The whole spectrum of steel products!

50. Classifications of Steel Steels are grouped into five main classifications. Carbon Steels More than 90 percent of all steels are carbon steels. They contain varying amounts of carbon and not more than 1.65 percent manganese, 0.60 percent silicon, and 0.60 percent copper. Machines, automobile bodies, most structural steel for buildings, ship hulls, bedsprings, and bobby pins are among the products made of carbon steels.