4Hughes They They

1. STEEL MANUFACTURING PROCESSES
 Steel is processed by the following processes:
1. Bessemer Process
2. Open-hearth Process
3. L-D Process
4. B.O.F Process
5. Electric Arc Process
6. Induction Process

2. Fig.1 Bessemer
converter

3. BASSEMER PROCESS:
 The process is carried out in a pear shaped vessel
known as a converter.
 The converter can be rotated on the trunnions in the
horizontal position in order to pour out the product.
 Molten pig iron from the cupola furnace is poured in to
converter and a strong blast of air is blown through the
molten metal which helps in the combustion of the
charge, producing intense heat, necessary for oxidation.
 The duration of the conversion process is between 20-
25 min. which is too short to control the oxidation properly.

4.  Open Hearth Process
Fig.2 open-hearth furnace

5. • How Open Hearth Furnace works:
 Open hearth (Siemen’s) process is used for producing large
quantities of steel, up to 600 tons.
 The furnace is of rectangular shape with a saucer-like
hearth as shown in the fig.2 can either be stationary or of the
tilting type.
 The gases, along with the recalculating waste gases from
the chimney, are preheated in regenerators which are the
chambers placed on either side of the hearth.
 The regenerators are made up of checker-work brick with
spaces and are heated with the help of wood or some other
fuel.

6.  How working con/d
 The heated gases and air pass through the pig-iron and the
scrap is kept in the hearth.
 The regenerators on both the sides are alternately operated
with 20 minutes phase which help in retaining high
temperature to melt the steel,
 The two types of furnaces are the Basic Open Hearth
furnaces and the Acid Open Hearth furnace. The bed and
walls of basic type furnace are made of sintered dolomite or
magnetite, whereas the acid type furnace has a sand bed.
 The process of heating for conversion to steel, takes
between 6 to 14 hrs, depending upon the type of the fuel used
and the quantity of the product taken for heating. Steel scrap
up to 50% can be heated along with the pig-iron.

7.  Linz-Donawitz Processes
Fig.3 Linz-Donawitz Process

8.  Facts about LDP:
 The defects mentioned in the Bessemer process are
overcome in the Linz-Donawitz (LD) process.
 Pig-iron and steel scrap are poured into the basic lined
converter.
 A compressed jet of pure oxygen O2 is blown into the
converter through a lance .
 The tip of the water-cooled lance is kept from 1 to 3m
above the molten metal surface.

9. Facts con/d
 The heat generated producing a temperature of nearly
3000°C by blowing oxygen is far in excess of what is required.
 The steel scrap of the pig-iron, up to 50%, is poured to
utilize the excess heat.
 The oxygen oxidizes the impurities which are drawn-out as
slag.
 This process is suitable for pig-iron with low-phosphorus
content.

10.  Other Oxygen Process:
Some modifications in the L.D.process have led to better
results. A brief description of the various modified processes
is given below:
(a) Basic Oxygen Furnace Process (BOF process)
 The converter is lined with magnetite bricks and pasted with dolomite.
 It is then loaded with scrap pieces .followed by molten pig-iron.
 A jet of oxygen gas is blown through the lance on the surface.
 The converter is fed with lime and fluorspar the mount oxidation begins.
 The process is most suitable for pig-iron, containing phosphorus.

11. Other Oxygen Process con/d
(b) Kaldo process
 A basic lined converter which rotates, on roller bearing,
with a speed of approximately 30 r/m., is used for the
process.
 The converter can be tilted to a convenient position for
loading and unloading.
 A jet of oxygen is blown on the charge. The rotating
converter mixes up the charge and oxygen thoroughly to
produce better quality.

12. Other Oxygen Process con/d
(c) Rotor process
 The process uses a horizontal cylindrical type furnace
which rotates around its axis.
 There are two oxygen-carrying lances the nozzle of one
lance is immersed in the molten and pig iron along with the
scrap.
 The other lance nozzle is placed a little above the
surface of the molten metal. The system provides proper
oxidation for a better product.

13.  Electric Arc Process:
Fig.4 A typical Electric Arc furnace.. ...

14. • Working steps of E.A.F.
 It employs carbon or graphite electrodes for striking an
arc between their tips and the metal by passing usually an
a.c. current.
 In other type of furnaces, the arc is struck between
horizontally placed electrodes where the tips of the arc are
kept a little above the metal.
 In both the types, a device of feeding the electrodes must
be provided due to the constant consumption of electrodes.
 The furnace is capable of tilting on roller bearings for
pouring out the molten metal through the spout.

15.  Working steps con/d
 The furnace is provided with the basic lining.
 Lime is added to the pig-.iron to remove the sulphur
contents.
 The melting period is between 1 to 3 base hrs.
• The impurities are removed in two stages:
 First, some lime is added which removes impurities
like phosphorus and silicon through draining off the
slag.
 In the second stage lime, fluorspar and anthracite
is added to remove the sulphur contents effectively

16. Tab le, this chart compares the applications of the three
main steel-making processes

17. Fig.5 Induction furnace
 Induction Furnace (Crucible Furnace)

18.  Facts about Induction Furnace
 It is best suited for a steel which has a high melting
point.
 The crucible is surrounded with primary water-cooled
copper coils.
 A high frequency current is passed through the coil
which induces eddy currents through the charge,
producing heat

19.  Classification of Iron – Carbon Alloys
• The classification depends upon carbon
content. There are 3 groups:
1. Irons
2. Steels
3. Cast irons
1. Irons – are relatively pure form and carbon content is
very low.

20. • Depending up on the method of production
and purity, irons can be divided into three
groups:
1/ Pure-iron
2/ Commercial iron
3/ Wrought iron
 Pure iron, contain 99.99% iron. (Very expensive to
produce, iron and such kind of purity may necessary for
research).
 Commercial iron contains 99.9% iron It is relatively
expensive.

21.  Applications of pure iron:
 When superior ductility is necessary.
 For high Corrosion resistance
 Electrical conductivity etc.
• Wrought iron- is not strictly a pure form of iron, but
contains 3% of slag particles.
Application of wrought iron can be,- for oil, water,
and steam pipes, etc.

22. 2.Steels: Steel is the most widely used of all metals. Steel
is more ductile (able to deform without breakage) and
durable than cast iron and is generally forged, rolled, or
drawn into various shapes.
• Steels are iron carbon alloys containing up to 2.14% C.
• In addition to carbon, steels generally contain small amounts
of sulphur, phosphorus, silicon, and manganese.
 Steels are most extensively used in industries, construction,
and steels classified into:
 Low carbon steels (less than 0.3% C)
 Medium carbon steels (0.3 - 0.6% C)
 High carbon steels (more than 0.6% C)

23.  Applications:
 LCS used for - Nails, rivets, fencing, stamping,
channels, beams, angles, pipes, etc;
 MCS used for - crankshaft, bolts, connecting rods,
machine components, screw drivers, etc.
 HCS used for - lock washer, valve springs, rail rods,
wrenches, dies, knives, and anvils, chisels, Hammers
shear blades, milling cutter, taps, hacksaw blades, etc.