1. 1. Describes in simple terms the production of pig iron from iron ore
2. Describe the principles of the open-hearth, the Bessemer and more modern
processes used in the production of steel from pig iron
3. Explains the principal differences between sand casting, die casting, centrifugal
casting, forgings, cold working and hot-rolled plate, bars and other sections
4. States the normal range of carbon content in mild steel, tool steel, cast steel and
cast iron
5. Describe the principle difference between ferrous and non ferrous metals
6. Gives examples of applications of non-ferrous metals in marine engineering
7. States the purpose of the alloying elements nickel, chromium and molybdenum
in steels used in marine engineering
8. Identifies the metals used in non-ferrous alloys commonly employed in marine
engineering

2. Metallurgy is a domain of materials science that studies the physical
and chemical behavior of metallic elements, their intermetallic
compounds, and their compounds, which are called alloys.
It is also the technology of metals: the way in which science is
applied to their practical use.
Metallurgy is commonly used in the craft of metalworking.
The differences between the various types of iron and steel are
sometimes confusing because of the nomenclature used.
Steel in general is an alloy of iron and carbon, often with an admixture
of other elements.
Some alloys that are commercially called irons contain more carbon
than commercial steels.

3. Open-hearth iron and wrought iron contain only a few hundredths
of 1 percent of carbon.
Steels of various types contain from 0.04 percent to 2.25 percent of
carbon.
Cast iron, malleable cast iron, and pig iron contain amounts of
carbon varying from 2 to 4 percent.
A special form of malleable iron, containing virtually no carbon, is
known as white-heart malleable iron.
A special group of iron alloys, known as ferroalloys, is used in the
manufacture of iron and steel alloys; they contain from 20 to 80
percent of an alloying element, such as manganese, silicon, or
chromium.

4. The production of iron or steel is a process:
3. The first stage is to produce pig iron in a blast furnace.
5. The second is to make wrought iron or steel from pig iron by a
further process.
To make iron, you start with iron ore. Iron ore is simply rock that
happens to contain a high concentration of iron.
Common iron ores include:
Hematite - Fe2O3 - 70 percent iron
Magnetite - Fe3O4 - 72 percent iron
Limonite - Fe2O3 + H2O - 50 percent
to 66 percent iron
Siderite - FeCO3 - 48 percent iron

5. Creating Iron
As see in the previous section that all of the iron ores contain iron
combined with oxygen. To make iron from iron ore, we need to
eliminate the oxygen to create pure iron.
The most primitive facility used to refine iron from iron ore is called a
bloomery. In a bloomery, charcoal is burnt with iron ore and a good
supply of oxygen (provided by a bellows or blower).
Charcoal is essentially pure carbon. The carbon combines with oxygen
to create carbon dioxide and carbon monoxide (releasing lots of heat
in the process). Carbon and carbon monoxide combine with the
oxygen in the iron ore and carry it away, leaving iron metal.

6. In a bloomery, the fire does not get hot enough to melt the iron
completely, it left with a spongy mass containing iron and silicates
from the ore (the bloom).
By heating and hammering the bloom, the glassy silicates mix into
the iron metal to create wrought iron. Wrought iron is tough and easy
to work, making it perfect for creating tools in a blacksmith shop.
The more advanced way to smelt iron is in a blast furnace. A blast
furnace is charged with iron ore, charcoal or coke (coke is charcoal
made from coal) and limestone (CaCO3).
Huge quantities of air blast in at the bottom of the furnace. The
calcium in the limestone combines with the silicates to form slag. At
the bottom of the blast furnace, liquid iron collects along with a layer
of slag on top. Periodically, let the liquid iron flow out and cool.

7. The liquid iron typically flows into a channel and indentations in a
bed of sand. Once it cools, this metal is known as pig iron.
To create a ton of pig iron, start with 2 tons of ore, 1 ton of coke and
half-ton of limestone. The fire consumes 5 tons of air. The
temperature reaches almost 3000 degrees F (about 1600 degrees C) at
the core of the blast furnace.
Pig iron contains 4 percent to 5 percent carbon and is so hard and
brittle that it is almost useless. Thus melt the pig iron, mix it with
slag and hammer it to eliminate most of the carbon (down to 0.3
percent) and create wrought iron. Wrought iron is the stuff a
blacksmith works with to create tools, horseshoes and so on. When
heat the wrought iron, it is malleable, bendable, weldable and very
easy to work with.

8. Blast Furnace

9. Modern
Furnace

10. Description:
1. Hot blast from Cowper stoves
2. Melting zone
3. Reduction zone of ferrous oxide
4. Reduction zone of ferric oxide
5. Pre-heating zone
6. Feed of ore, limestone and coke
7. Exhaust gases
8. Column of ore, coke and limestone
9. Removal of slag
10. Tapping of molten pig iron
11. Collection of waste gases

11. Creating Steel
Steel is iron that has most of the impurities removed. Steel also has a
consistent concentration of carbon throughout (0.5 percent to 1.5
percent).
Impurities like silica, phosphorous and sulfur weaken steel
tremendously, so they must be eliminated. The advantage of steel over
iron is greatly improved strength.
The open hearth furnace is one way to create steel from pig iron. The
pig iron, limestone and iron ore go into an open hearth furnace. It is
heated to about 1600 F (871 C).
The limestone and ore forms a slag that floats on the surface.
Impurities, including carbon, are oxidized and float out of the iron into
the slag. When the carbon content is right, you have carbon steel.

12. Another way to create steel from pig iron is the Bessemer process.
Most modern steel plants use what's called a basic oxygen furnace
to create steel. The advantage is that it is a rapid process -- about 10
times faster than the open hearth furnace.
A variety of metals might be alloyed with the steel at this point to
create different properties. For example, the addition of 10 percent
to 30 percent chromium creates stainless steel, which is very
resistant to rust. The addition of chromium and molybdenum creates
chrome-moly steel, which is strong and light.
When you think about it, there are two accidents of nature that have
made it much easier for humans to move forward at a rapid pace.
One is the huge availability of something as useful as iron ore. The
second is the availability of vast quantities of oil and coal to power
the production of iron. This is a very lucky coincidence, because
without iron and energy, we would not have gotten nearly as far as
we have today

13. Question:
Describe the principles of the Bessemer and basic oxygen used
in the production of steel from pig iron.
Due date: 20th November 2008 (before 1700 hrs)
Assessment: 5%

14. Casting is the process whereby molten material is poured into a
mould of the required shape and then allowed to solidify.
Moulding is a similar process used to form plastic materials. The
mould should be shaped so that molten material flows to all parts of
the mould.
Advantages
This process is widely used as a primary forming process and
suitable for bulk shaping of a material.
Disadvantages
The shape of the finished casting may be different to the shape of the
mould because metals shrink as they cool.

15. Considerations when selecting a method of casting
2.The type of casting process most suitable for a particular
application is dictated by a number of factors. These include:
3.The number of castings
4.The cost per casting
5.The material being cast
6.The surface finish and tolerances of the finished casting
7.The size of the casting
Casting Methods
Typical casting processes include:
Sand casting
Die casting
Centrifugal casting

16. Sand Casting involves packing a moulding material (traditionally a
mixture of sand and clay) around a pattern of the casting. This is usually
made of a hardwood and will be larger than the requirements of the
finished casting to allow for shrinkage. The mould is then split so that
the pattern can be removed.
Advantages
This process can be used for a large range of sizes and for small or large
production runs. It is the cheapest casting process available for small
production runs and can sometimes be economical for large production
runs.
Disadvantages
The surface finish and tolerances of the finished casting are poor. This
form of casting can significantly alter the mechanical properties of the
material being cast. The time required to cast a components can be
excessive due to the need to allow the casting to cool before removing it
from the mould.

20. Die casting uses a metal mould into which molten metal is poured and
allowed to solidify.
There are two main methods of feeding the molten metal into the mould:
1. Gravity die casting uses the force of gravity to draw the molten metal
down into the mould.
2. Pressure die casting involves forcing the molten metal into the mould
under pressure. Using pressure die casting enables more complex shapes
to be cast ensuring the molten metal flows to all corners of the mould.
Advantages
Machining and finishing costs can significantly reduce or even
eliminated because of the relatively good dimensional tolerances and
surface finish achieved using this process
All casting alters the physical properties of the material, but using this
die casting this can be minimised.

21. Disadvantages
This process too expensive for small production runs because of the
high cost of producing the mould.
Its use is restricted to metals with lower melting points (E.g.
magnesium, aluminium) than the mould metal
Aluminum, Zinc and Copper alloys are the materials predominantly
used in die-casting.
On the other hand, pure Aluminum is rarely cast due to high shrinkage,
and susceptibility to hot cracking. It is alloyed with Silicon, which
increases melt fluidity, reduces machinability.
Copper is another alloying element, which increases hardness, reduces
ductility, and reduces corrosion resistance.

22. Aluminum is cast at a temperature of 650 ºC (1200 ºF).
It is alloyed with Silicon 9% and Copper about 3.5% to form the
Aluminum Association 380 alloy (UNS A03800).
Silicon increases the melt fluidity, reduces machinability.
Copper increases hardness and reduces the ductility.
By greatly reducing the amount of Copper (less than 0.6%) the
chemical resistance is improved; thus, AA 360 (UNS A03600) is
formulated for use in marine environments.
A high silicon alloy is used in automotive engines for cylinder
castings, AA 390 (UNS A03900) with 17% Silicon for high wear
resistance.

23. Zinc can be made to close tolerances and with thinner walls than
Aluminum, due to its high melt fluidity.
Zinc is alloyed with Aluminum (4%), which adds strength and
hardness.
The casting is done at a fairly low temperature of 425 ºC (800 ºF)
so the part does not have to cool much before it can be ejected from
the die.
This, in combination with the fact that Zinc can be run using a hot
chamber process allows for a fast fill, fast cooling (and ejection)
and a short cycle time.
Zinc alloys are used in making precision parts such as sprockets,
gears, and connector housings.

24. Copper alloys are used in plumbing, electrical and marine
applications where corrosion and wear resistance is important.
Minimum wall thicknesses and minimum draft angles for die
casting are:

25. Die-castings are typically limited from 20 kg (55 lb) max. for
Magnesium, to 35 kg (77 lb) max. for Zinc.
Large castings tend to have greater porosity problems, due to entrapped
air, and the melt solidifying before it gets to the furthest extremities of
the die-cast cavity. The porosity problem can be somewhat overcome
by vacuum die casting.
From a design point of view, it is best to design parts with uniform
wall thicknesses and cores of simple shapes.
Heavy sections cause cooling problems, trapped gases causing
porosity.
All corners should be radiused generously to avoid stress
concentration. Draft allowance should be provided to all for releasing
the parts-these are typically 0.25º to 0.75º per side depending on the

30. Object been
ejected

31. In centrifugal casting, a permanent mold is rotated about its axis at
high speeds (300 to 3000 rpm) as the molten metal is poured.
The molten metal is centrifugally thrown towards the inside mold
wall, where it solidifies after cooling.
Centrifugal force shapes the and feeds the molten metal into the
designed crevices and details of the mold. The centrifugal force
improves both homogeneity and accuracy of the casting.
The casting is usually a fine grain casting with a very fine-grained
outer diameter, which is resistant to atmospheric corrosion, a typical
situation with pipes.
The inside diameter has more impurities and inclusions, which can
be machined away.

32. Only cylindrical shapes can be produced with this process.
Size limits are upto 3 m (10 feet) diameter and 15 m (50 feet) length.
Wall thickness can be 2.5 mm to 125 mm (0.1 - 5.0 in). The
tolerances that can be held on the OD can be as good as 2.5 mm (0.1
in) and on the ID can be 3.8 mm (0.15 in). The surface finish ranges
from 2.5 mm to 12.5 mm (0.1 - 0.5 in).
Typical materials that can be cast with this process are iron, steel,
stainless steels, and alloys of aluminum, copper and nickel.
Two materials can be cast by introducing a second material during
the process.
Typical parts made by this process are pipes, boilers, pressure
vessels, flywheels, cylinder liners and other parts that are axi-
symmetric.

33. Advantages
2.The centrifugal force ensures the mould is fully filled out with
the molten material.
3.Rapid production rate.
4.Ability to produce extremely large cylindrical parts.
Disadvantages
Not suitable for casting complex shapes.

35. Forging is the process of shaping malleable metals by hammering
or pressing. The process refines the grain size and flow of the metal
and so improves its structure.
Forged metal is stronger and more ductile than cast metal and
exhibits greater resistance to fatigue and impact.
A forged metal can result in the following:
• Increase length, decrease cross-section, called drawing out the
metal.
• Decrease length, increase cross-section, called upsetting the
metal.
• Change length, change cross-section, by squeezing in closed
impression dies.
Forging changes the size and shape, but not the volume, of a part.

36. Types of Forging
1. Drop forging is a metal shaping process in which a heated
workpiece is formed by rapid closing of a punch and die forcing
the workpiece to conform to a die cavity.
A workpiece may be forged by a series of punch and die operations
(or by several cavities in the same die) to gradually change its
shape.
Drop forging is also called impression die or closed die forging, or
rot forging.

39. 2. Upset forging is a metal shaping process in which a heated workpiece
of uniform thickness is gripped between split female dies while a
heading die (punch) is forced against the workpiece, deforming and
enlarging the need of the workpiece.
A sequence of die cavities may be used to control the workpiece
geometry gradually until it achieves its final shape. This is a rapid
"cold forming" process.

41. 3. Cold heading is defined as a "metal forging process used for rapidly producing
enlarged (upset) sections on a piece of rod or wire held in a die."
The resulting shape of the upset portion conforms to the shape of the die cavity.
Workpieces are not heated prior to heading. Upsetting may be done in one or
more strokes.

43. Cold working refers to plastic deformation that occurs usually, but
not necessarily, at room temperature. Plastic deformation is a
deformation in which the material does not return to its original
shape; this is the opposite of an elastic deformation.
Effects of Cold Working:The behavior and workability of the
metals depend largely on whether deformation takes place below or
above the recrystallization temperature.
Deformation using cold working results in:
• Higher stiffness, and strength, but
• Reduced malleability and ductility of the metal.

44. Hot working is the deformation that is carried out above the
recrystallization temperature.
In these circumstances, annealing takes place while the metal is worked
rather than being a separate process.
The metal can therefore be worked without it becoming work hardened.
Hot working is usually carried out with the metal at a temperature of
about 0.6 of its melting point.

45. Effects of hot working
• At high temperature, scaling and oxidation exist. Scaling and
oxidation produce undesirable surface finish. Most ferrous metals
needs to be cold worked after hot working in order to improve the
surface finish.
• The amount of force needed to perform hot working is less than that
for cold work.
• The mechanical properties of the material remain unchanged during
hot working.
• The metal usually experiences a decrease in yield strength when hot
worked. Therefore, it is possible to hot work the metal without
causing any fracture.

46. Warm working: as the name implies, is carried out at intermediate
temperatures. It is a compromise between cold and hot working.
The effects of this type of working depend on how close is the warm
process to be a cold or hot process.
The type of process chosen depends on the physical and mechanical
properties needed for the product, meaning the product itself and its
uses.

47. Methods used for Cold, Hot working
1. Rolling
2. Forging
3. Extrusion
4. Drawing

48. Rolling is a fabricating process in which the metal, plastic, paper,
glass, etc. is passed through a pair/pairs of rolls.
There are two types of rolling process, flat and profile rolling.
Rolling is also classified according to the temperature of the metal
rolled. If the temperature of the metal is above its recrystallization
temperature then the process is termed as hot rolling.
If the temperature of metal is below its recrystallization temperature
the process is termed as cold rolling.

49. In flat rolling the final shape of the product is either classed as sheet
(typically thickness less than 3 mm, also called "strip") or plate
(typically thickness more than 3 mm).

50. In profile rolling, the final product may be a round rod or other
shaped bar such as a structural section (beam, channel, joist etc).

51. In the extrusion process, a billet (generally round) is forced
through a die in a manner similar to squeezing toothpaste from a
tube.
Almost any solid or hollow cross-section may be produced by
extrusion, which can create essentially semi-finished parts. Because
the die geometry remains the same throughout the operation,
extruded products have a constant cross-section. This can be done
with cold, warm or hot working.
Typical products made by extrusion are railings for sliding doors,
tubing having carious cross-sections, structural and architectural
shapes, and door and windows frames.

53. Drawing is an operation in which the cross-section of solid rod, wire
or tubing is reduced or changed in shape by pulling it through a die.
Drawn rods are used for shafts, spindles, and small pistons and as the
raw material for fasteners such as rivets, bolts, screws.
Drawing also improves strength and hardness when these properties
are to be developed by cold work and not by subsequent heat
treatment.