Iron making

1. Introduction
 Earth crust contain 5% iron as iron oxide (mostly Fe2O3 and
Fe3O4)
 Iron oxide + coke, coal or charcoal = metallic Fe
 Economic extraction of iron = iron ore ( Fe% = 55-60%)
 Iron ore contain other elements Al, Si, Mn, P
 Iron products wrought iron, cast iron and steel

2. Early History of Iron
 In the early days, wrought iron, cast iron and steel are known as
iron
 Iron samples – in the British Museum dates back to about 3500-
4000 BC
 The first definite evidence of ironmaking – by reduction of oxide
dates back to about 1500 BC
The primitive ironmaking
Furnaces: -Bowl shape (1-1.5 m high and 0.4 to 0.8 m dia)
-Dried clay lining
-Charcoal as reducing agent
-Oxygen in the mouth by blowing air
Combustion of carbon with oxygen produces CO and heat
Fe-oxide(s) + CO(g) = Fe(s) + CO2(g)

3.  Maximum temp attained 11000C
 Metallic iron could not absorb much carbon
 Melting did not take place
 Hot iron as solid state mixed with low melting FeO enriched slag
 Repeated heating followed by forging using a hammer, most of
the slag got squeezed out
 Solid pure iron of low C containing small slags known as
wrought iron is obtained

4. Cast Iron
 Later stage historically liquid iron came after wrought iron
 Liquid iron was first produced in China (dating back to about 1000
AD)
 Iron casting in ancient China can be attributed as the following:
-More efficient furnaces
-Introduction of high carbon absorption in iron
-High P content decrease the melting point

5. Evolution of Iron Making in Europe
 Ancient iron making process developed around the
Mediterranean sea, then spread northwards to Europe
 Next significant development took place in the Spanish province
where water wheels were employed to blow air (100 kg/12
hours)
 Stukofen in Germany produced 100-150 tonnes per annum
 Next step in ironmaking furnace design was the Flussofen in the
Rhine valley in Germany (14th century) – to cast cannons
 The charcoal blast furnaces developed in the European continent
then spread to great Britain where the next evolution of
ironmaking technology occurred

6. The major developments that took place till about 1880 are summarised below
Replacement of charcoal by coke
-coke was first used in a blast furnace by Dudley in 1709
Use of steam engines for air blowing
-invented in 1760
Pre-heating of the air blast
-Neilson in 1829 introduced the concept of pre-heating the sir blast
-coal consumption is 8 tonnes for 1 ton iron,
-preheating of air to 1500C reduced the coal consumption to 3 tonnes
-latter the the pre-heating was developed to 6000C
Utilisation of blast furnace gas as fuel
-High CO content blast furnace flue gas was burnt to preheat the air
blast
-in 1845, Bunsen and Playfair suggested that this flue gas can be
utilized in ironmaking
-in 1850, cup-and-bell system was introduced

7. Iron and Steel Heritage of India
 Iron objects were used in 1500 BC
 Delhi iron pillars – 7 tonnes wt; 8 m in height; bottom and top
diameters of 0.42 and 0.31 m respectively; made about 1500-
1550 years ago; wrought iron; composite structure comprising
alternate bands of metal and slag
 Wootz steel- famous swords were fabricated

8. Evolution of Iron making Technology since 1880
1. The developing of Blast furnace
the period from 1880 to 1950
• most development were in the field of furnace design and
engineering
• no significant changes in process technology, due to the
-lack of knowledge of physicochemical and metallurgical aspects of
blast furnace reactions
-the internal state of BF was not known
The developments upto 1950 led to the following changes:
-more powerful blowing engine
-higher blast temperature
-bigger furnaces
-better charging equipment
-improved raw materials storage

9. Considerable improvements have been made interim period:
-raw materials charging system
-the blast furnace gas cleaning system
-the lining life
-molten iron tapping system

10. Development after 1950
The important developments may be summed up as follows:
-use of prepared burdens: sinter and pillets
-proper size and better quality coke
-injection of pulverized coke through the tuyeers
-larger furnace volume and high blast temperature
-oxygen enrichment of the air blast
-high top pressure operation
-computer-aided process control
The progress made in BF ironmaking, summerized in Table 1.2

11. 2. Alternative ironmaking process
8% of total global iron produced by alternative ironmaking process
(AIP)
Two types of AIP are
-iron as solid by solid-state reaction: sponge iron
-liquid iron by a combination of solid and liquid-state reaction

12. At the end of this course, students should be able to:
1. understand the fundamental principles.
2. identify and quantify microstructure, chemistry and atomic structure of materials.
3. assess which characterization methods are appropriate for different materials problem
evaluate the quality of the materials in practical applications.
Course Learning Outcome (CO)
Course Objectives (CO)
The objectives are to
Know the evolution of ironmaking
Fundamental understanding on theories of ironmaking
Understand the modern processes of iron making