1. S. Y. B.Sc Introduction Properties Occurrence Uses Metallurgy
Metallurgy of Iron
S. Y. B.Sc
Introduction
Properties
Occurrence
Uses
Metallurgy
Dr. R. K. Jadhav
Dept. of Chemistry,
S. M. Joshi College, Hadapsar, Pune.

2. Early Iron Works

3. Introduction Iron or ferrum (latin word)
Elemental symbol: Fe
Atomic number:
Elemental group: Transition element
Metallic iron was known and used for ornamental purposes and weapons in prehistoric ages.
The earliest specimen still extant, a group of oxidized iron beads found in Egypt, dates from about 4000 BC.
The archaeological term Iron Age properly applies to the period when iron was used extensively for utilitarian purposes, as in tools, as well as for ornamentation.

4. Physical Properties Iron is soft, malleable, and ductile.
Iron is easily magnetized at ordinary temperatures; it is difficult to magnetize when heated, and at about 790° C (about 1450° F) the magnetic property disappears.
Pure iron melts at about 1535° C (about 2795° F), boils at 2750° C (4982° F), and has a specific gravity of 7.86.
The atomic weight of iron is

5. Chemical Properties
It combines with the halogens (fluorine, chlorine, bromine, iodine, and astatine), sulfur, phosphorus, carbon, and silicon.
It displaces hydrogen from most dilute acids.
It burns in oxygen to form ferrosoferric oxide, Fe3O4 (magnetite).

6. Chemical Properties
When exposed to moist air, iron becomes corroded, forming a reddish-brown, flaky, hydrated ferric oxide commonly known as rust.
When iron is dipped into concentrated nitric acid, it forms a layer of oxide that renders it passive—that is, it does not react chemically with acids or other substances. The protective oxide layer is easily broken through by striking or jarring the metal, which then becomes active again.

7. Occurrence of Fe

8. MAGNETITE:
HEMATITE:(RED)
HEMATITE:(BROWN)

9. DIFFERENT IRON ORES

10. Raw Materials for Production
Iron Ore
Limestone 
Coke

11. Occurrence
Metallic iron occurs in the free state in only a few localities, notably western Greenland. It is found in meteorites, usually alloyed with nickel.
In chemical compounds the metal is widely distributed and ranks fourth in abundance among all the elements in the earth's crust; next to aluminum it is the most abundant of all metals.

12. Occurrence
The principal ore of iron is hematite, which is mined in the United States in Minnesota, Michigan, and Wisconsin.
Other important ores are goethite, magnetite, siderite, and limonite (bog iron).

13. Occurrence
Pyrite, FeS, the sulfide ore of iron, is not processed as an iron ore because it is too difficult to remove the sulfur.
Small amounts of iron occur in combination in natural waters, in plants, and as a constituent of blood.

14. Uses of Iron
Iron is used in processed forms, such as wrought iron, cast iron, and steel.
Commercially pure iron is used for the production of galvanized sheet metal and of electromagnets.
Iron compounds are employed for medicinal purposes in the treatment of anemia.
Iron is also used in tonics.

15. Uses of Iron
The most important ferrous compound is ferrous sulfate (FeSO4), called green vitriol or copperas.
It usually occurs as pale-green crystals containing seven molecules of water of hydration.
It is obtained in large quantities as a by-product in pickling iron and is used as a mordant in dyeing, as a tonic medicine, and in the manufacture of ink and pigments.

16. Uses of Iron
Ferric oxide or hematite, an amorphous red powder, is obtained by treating ferric salts with a base or by oxidizing pyrite.
It is used both as a pigment, known as either iron red or Venetian red; as a polishing abrasive, known as rouge; and as the magnetizable medium on magnetic tapes and disks.
Ferric chloride, obtained as dark-green, lustrous crystals by heating iron in chlorine, is used in medicine as an alcoholic solution called tincture of iron.

17. Uses of Iron
Ferric ferrocyanide (Fe4[Fe(CN)6]3), a dark-blue, amorphous solid formed by the reaction of potassium ferrocyanide with a ferric salt, is called Prussian blue.
It is used as a pigment in paint and in laundry bluing to correct the yellowish tint left by the ferrous salts in water.
Potassium ferricyanide (K3Fe(CN)6), called red prussiate of potash, is obtained from ferrous ferricyanide (Fe3[Fe(CN)6] 2; also called Turnbull's blue), and is used in processing blueprint paper.

18. Metallurgy of Iron Reduction of iron oxide in the Blast furnace.
Materials:
Concentrated iron ore
Coke
Blast of hot air
Flux

19. Metallurgy of Iron (i) Ore – Haematite (Fe2O3)
(ii) Concentration of ore – by magnetic separation
(iii) Roasting – Moisture, sands are removed as oxide.
Smelting – Done in blast furnace. Roasted ore, limestone and coke are added in blast furnace for smelting.

20. Blast Furnace Same height as a 10 story building) Steelmaking Tuyeres

21. Blast Furnace Temperature Probe Sub Burden Probe Top Bins
Top Gas Mains
Top Bins
Throat Armour
Above Burden Probe
Temperature Probe
Refractory Lining
Sub Burden Probe
Burden probes: temperature and gas probes to control the distribution of the burden materials
Throat armour: high resistant metal plates to protect the refractories from dropping burden materials
Bustle main: ring pipe for hot blast
Tuyeres: water cooled nozzles for hot blast injection
Hearth refractories: temperature resistant materials (mainly carbon)
Bustle Main
Tuyeres
Hearth Refractories

22. DETAILS OF EXTRACTION
The process of the extraction of iron is carried out by the following steps:
Concentration of ore Calcinations or Roasting of ore Reduction of ore
Concentration of ore: In this metallurgical operation, the ore is concentrated by removing impurities like soil etc. The process involves the crushing and washing of ore.
Calcinations or Roasting of ore: The concentrated ore is now heated in the presence of air. The process of roasting is performed to remove moisture, CO2, impurities of sulphur, arsenic. Ferrous oxide is also oxidized to ferric oxide.
Reduction of ore
The process of reduction is carried out in a blast furnace.
Blast Furnace
The blast furnace is a cylindrical tower like structure about 25m to 35m high. It has an outer shell of steel. Inside of furnace is lined with fire bricks. The top of the furnace is closed by a cup-cone feeder.

23. At 1900 °C C+ O2 → CO2 FeO +C → Fe + CO
At 500 °C 3Fe2O3 +CO → 2Fe3O4 + CO2 Fe2O3 +CO → 2FeO + CO2
At 850 °C Fe3O4 +CO → 3FeO + CO2
At 1000 °C FeO +CO → Fe + CO2
At 1300 °C CO2 + C → 2CO
At 1900 °C
C+ O2 → CO2
FeO +C → Fe + CO

25. Removing Iron from Iron Ore
Iron is found in nature not as free iron (Fe), but as iron ore which consists of iron oxides (Fe2O3 being the most abundant) and impurities.
Smelting is the process of removing or extracting Fe from its ore; i.e. Separating Fe and O in Fe2O3 to isolate Fe for subsequent uses.

26. Chemistry of Iron Smelting
This is a multi-step process of sequential reductions of iron to elemental iron (Fe)
3Fe2O3(s) + CO(g)  2Fe3O4(s) + CO2(g)
2Fe3O4(s) + 2CO(g)  6FeO(s) + 2CO2(g)
6FeO(s) + 6CO(g)  6Fe(s) + 6CO2(g)
Resulting in 3Fe2O3(s)+9CO(g)6Fe(s)+9CO2(g)
Fe2O3(s) + 3CO(g)  2Fe(s) + 3CO2(g)

27. Reactions taking place in the Blast furnace
Combustion of Coke
C(s) + O2(g)  CO2(g) + heat
CO2(g) + C(s)  2CO(g)
Reduction of Fe2O3
2Fe2O3(s) + 3C(s)  4Fe(l) + 3CO2(g)
Fe2O3(s) + 3CO(g)  4Fe(l) + 3CO2(g)

28. Reactions taking place in the Blast furnace
Calcination
CaCO3(s) + heat  CaO(s) + CO2(g)
Slag formation
CaO(s) + SiO2(s)  CaSiO3(l) (slag)
CaO(s) + Al2O3(s)  Ca(AlO2)2(l)

29. 1. A blast furnace forces in extremely hot air through a mixture of ore, coke, and limestone, called the charge.
2. Carts called skips dump the charge into the top of the furnace, where it filters down through bell-shaped containers called hoppers.
Iron Blast furnace

30. 4. The waste metal, called slag, floats on top of the molten pig iron
4. The waste metal, called slag, floats on top of the molten pig iron. Both of these substances are drained, or tapped, periodically for further processing.
3. Once in the furnace, the charge is subjected to air blasts that may be as hot as 870° C (1600° F).
Iron Blast furnace

31. Products of the Blast furnace
Pig iron % Fe, 3-5% C, 1% Si, % P, <1% S
Waste gases – CO2 and CO
Slag – CaSiO3 and Ca(AlO2)2
Principal products of Iron
Cast iron
Wrought iron
Steel

32. CAST IRON WROUGHT IRON STEEL
This is pig iron melted with scrap Iron. It is the least pure of all forms of iron containing 93% Fe & 5% C.
WROUGHT IRON
The purest form of iron produced when impurities are removed. It contains 0.5% impurities.
STEEL
A form of iron which usually contains 0.1 to 2% carbon.

33. Steeling – Tempering
Steeling – iron is heated in charcoal causing carbon to be absorbed into surface
Tempering:
Step 1: quenching = sudden cooling of hot metal by plunging it into water
Step 2: re-heat to about 700° C to remove micro-cracks in the surface (removes brittleness and improve hardness)

34. Eastern Approach - Casting
Chinese learned to melt iron due to:
A. Horizontal, double action bellows
B. High carbon content fuel
This allowed them to cast the iron. The molten iron was poured into molds. It was reheated between 800 and 900° C to remove carbon from surface which reduces brittleness.

35. STEEL Carbon steels Carbon content Uses Low carbon steel < 0.3%
Rivets, wires, nails
Medium carbon steel
0.3% to 0.8%
Railroad rails, axles
High carbon steel
0.8% to 2%
Tools, springs, files

36. Steel Making
Bessemer Process
Open-Hearth Method
Basic Oxygen Process

37. TYPES OF STEEL MAKING FURNACES
Used to burn the carbon out of the steel
Open Hearth – Hot air blown over the top of the steel (ceased in the 1940’s)
Bessemer – hot air blown from the bottom of the crucible (used between )
Electric – requires a tremendous amount of power
Continuous arc between electrode and metal
Electrodes made of carbon
Produce 60 to 90 ton of very clean steel/day
Basic Oxygen Furnace (BOF)
Uses pure O2 at 180 psi
Refine 250 tons/hour
IT208 37

39. Bessemer process
The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855.

40. ] Bessemer converter
The process is carried out in a large ovoid steel container lined with clay or dolomite called the Bessemer converter. The capacity of a converter was from 8 to 30 tons of molten iron with a usual charge being around 15 tons. At the top of the converter is an opening, usually tilted to the side relative to the body of the vessel, through which the iron is introduced and the finished product removed. The bottom is perforated with a number of channels called tuyères through which air is forced into the converter. The converter is pivoted on trunnions so that it can be rotated to receive the charge, turned upright during conversion, and then rotated again for pouring out the molten steel at the end.

41. Bessemer first started working with an ordinary reverbatory furnace but during a test a couple of pig ingots got off to the side of ladle and were sitting above it in the hot air of the furnace. When Bessemer went to push them into the ladle he found that they were steel shells: the hot air alone had converted the outer parts of the ingots to steel. This crucial discovery led him to completely redesign his furnace so that it would force high-pressure air through the molten iron using special air pumps. Intuitively this would seem to be folly because it would cool the iron, but due to exothermic oxidation both the silicon and carbon react with the excess oxygen leaving the surrounding molten iron even hotter, facilitating the conversion to steel.

42. Bessemer Process

44. Basic Oxygen Furnace

45. The Basic Oxygen Steelmaking (BOS) Process
Accounting for 60% of the world's total output of crude steel, the Basic Oxygen Steelmaking (BOS) process is the dominant steelmaking technology.
There exist several variations on the BOS process: top blowing, bottom blowing, and a combination of the two. This study will focus only on the top blowing variation.

46. The scheme of the Basic Oxygen Furnace (BOF) (basic oxygen furnace, basic oxygen converter) is presented in the picture.
Typical basic oxygen converter has a vertical steel shell lined with refractory lining.
The furnace is capable to rotate about its horizontal axis on trunnions.
This rotation is necessary for charging raw materials and fluxes, sampling the melt and pouring the steel and the slag out of the furnace.
The Basic Oxygen is equipped with the water cooled oxygen lance for blowing oxygen into the melt.
The basic oxygen converter uses no additional fuel. The pig iron impurities (carbon, silicon, manganese and phosphorous) serve as fuel.
The steel making process in the oxygen converter consists of:

47. Charging steel scrap.
Pouring liquid pig iron into the furnace.
Charging fluxes.
Oxygen blowing.
Sampling and temperature measurement
Tapping the steel to a ladle.
De-slagging.
The iron impurities oxidize, evolving heat, necessary for the process.
The forming oxides and sulfur are absorbed by the slag.
The oxygen converter has a capacity up to 400 t and production cycle of about 40 min.

49. BASIC OPERATION
BOS process replaced open hearth steelmaking. The process predated continuous casting. As a consequence, ladle sizes remained unchanged in the renovated open hearth shops and ingot pouring aisles were built in the new shops. Six-story buildings are needed to house the Basic Oxygen Furnace (BOF) vessels to accommodate the long oxygen lances that are lowered and raised from the BOF vessel and the elevated alloy and flux bins. Since the BOS process increases productivity by almost an order of magnitude, generally only two BOFs were required to replace a dozen open hearth furnaces.

51. Some dimensions of a typical 250 ton BOF vessel in the U. S
Some dimensions of a typical 250 ton BOF vessel in the U.S. are: height 34 feet, outside diameter 26 feet, barrel lining thickness 3 feet, and working volume 8000 cubic feet. A control pulpit is usually located between the vessels. Unlike the open hearth, the BOF operation is conducted almost "in the dark" using mimics and screens to determine vessel inclination, additions, lance height, oxygen flow etc.
Once the hot metal temperature and chemical analaysis of the blast furnace hot metal are known, a computer charge models determine the optimum proportions of scrap and hot metal, flux additions, lance height and oxygen blowing time.

52. Basic oxygen furnace with L.S.

54. Open-Hearth Furnace
Uses a fuel to generate heat, and melt the metal.

55. Electric Furnace
Uses electric arc from electrode to metal to heat and melt it.
Can produce tons of steel per day.
Steel is higher quality than open-hearth and BOF

56. Electric-arc furnace
The steel making process in the electric-arc furnace consists of:
Charging scrap metal, pig iron, limestone
Lowering the electrodes and starting the power (melting)
Oxidizing stage
At this stage the heat, produced by the arcs, causes oxidizing phosphorous, silicon and manganese. The oxides are absorbed into the slag. By the end of the stage the slag is removed.
De-slagging
Reducing stage
New fluxes (lime and anthracite) are added at this stage for formation of basic reducing slag.
The function of this slag is refining of the steel from sulfur and absorption of oxides, formed as a result of deoxidation.
Tapping
Lining maintenance

57. Continuous Casting -Metal solidifies in the mold
-Molten metal skips ingot step, and goes directly the furnace to a “tundish”
-Metal solidifies in the mold
-The metal about 1”/sec
-The solidified metal then goes through
‘pinch rollers’ that determine the final
form.

58. Benefits of Continuous Casting
Costs less to produce final product
Metal has more uniform composition and properties than ingot processing.

59. Residual Elements
During the processing of steels some residual elements remain in the medal.
These residuals are trace elements that are unwanted due to their detrimental properties but cannot be extracted completely.
Some of these residual elements include: antimony, arsenic, hydrogen, nitrogen, oxygen, and tin.
Molten Steel

60. Carbon Steels
Carbon steels are group by their percentage of carbon content per weight. The higher the carbon content the greater the hardness, strength and wear resistance after heat treatment.
Low-carbon steel, also called mild steels, has less than 0.30% carbon. Used in everyday industrial products like bolts, nuts, sheet, plate and tubes.
High Carbon Steel Nails

61. Stainless Steels
Using stainless steels as reinforcing bars, has become a new trend, in concrete structures such as highways buildings and bridges.
It is more beneficial than carbon steels because it is resistant to corrosion from road salts and the concrete itself.
Rebar corrosion in concrete

62. Stainless steels are primarily know for their corrosion resistance, high strength, and ductility and chromium content.
The reason for the name stainless is due to the fact that in the presence of oxygen, the steel develops a thin, hard, adherent film of chromium.
Even if the surface is scratched, the protective film is rebuilt through passivation.
For passivation to occur there needs to be a minimum chromium content of 10% to 12% by weight.