FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
FORGING, ROLLING, DRAWING, EXTRUSION AND CASTING
In forging and rolling processes the compressive forces are applied directly on the work surface
and as a result metal flows in a direction perpendicular to the applied forces.
FORGING
Definition:- It is the working of the metal in hot condition under the compressive forces to
obtain the desired shape.
It is of 2 types
1. Impact or hammer or hand forging:- Rapid forces are imparted on the work surface.
As and as the energy is absorbed, it leads to the development of pressure on the surface of
the workpiece ultimately leading to the deformation of the metal
2. Press forging:- the metal is subjected to slow compressive forces. In this the hammer
forces are blown on the workpiece, pressure increases there by the deformation take
place.
Forging materials that can be used are metals and alloys like mild steel, plain carbon steels,
wrought aluminium alloys, copper alloys, magnesium alloys etc.
Forging temperatures
The forging temperatures for the metal should always be above the recrystallization
temperature (A process by which dead grains are replaced by new set of grains that starts
growing until entire dead grains are consumed) and below melting temperature of the
material which results in deformation easily. Some of them are…
Material
Starting Temperature
Finishing Temperature
Low carbon steel
1300 deg
850 deg
High carbon steel
1150 deg
850 deg
Copper alloy
600 deg
550 deg
Wrought iron
1275
900 deg and so on
Similarly there are many metals and alloys
However heating above recrystallization temperature leads to oxidation of metals and
development of cracks. Hence the temperature should be optimum.
Forging processes:1. Smith forging
2. Drop forging
3. Press forging
4. Machine forging
Smith forging is a manual type of forging which is commonly seen in the streets.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Smith or hammer or hand or open die forging:-
It is termed as smith or hand forging as it is done by blacksmiths by hand operation. This
uses flat and open dies for forging operations and the final shape and accuracy depends on
the skill of the smith. The anvil is the basic requirement in this operation which is used to
forge the workpiece to the required shape. The heated part to be forged is hammered on the
anvil and on the horn by holding the tong. Tongs are used to hold and manipulate the parts.
However there are many operations done using hand forging, they are fullering, flattening
and swaging etc.
Fullering:- Reducing the cross section and increasing the length of the workpiece.
Flattening:- Flattening the worpiece using flattening tool.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Swaging:-
Used to reduce the workpiece to round shape or hexagonal shape.
Merits :1. Finished product can be obtained.
2. Grain flow occurs in forged part due to heating.
3. Metals can be easily forged.
Demerits :1. Initial cost is high.
2. Forged part cost is high.
3. The size and shape is limited as compared to casting.
Applications :1.
2.
3.
4.
In aerospace industry for aircraft engines.
In automotive industries for manufacturing connecting rods, piston rods, bearings.
To manufacture pumps and compressors.
Manufacturing plumbing fixtures, valves and fittings.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
ROLLING
Definition:- It is the process where the metal is compressed between the 2 rotating rolls for
reducing the cross sectional area. It is the most widely accepted process due to low cost
leading to higher productivity. The common most process that is being used in the industries
is the Two-high rolling mill.
Different types of rolling stand arrangement:1. 2- High rolling mill 2. 3- High rolling mill
4. 4- High rolling mill 5. Cluster rolling mill
3. 3- High rolling mill
6. Planetary rolling mill
2-high non-reversing and reversing rolling mills Procedure:-
This consists of 2 rolls i.e upper roll and lower roll with the smaller rolls for supporting. It is
of 2 types. They are reversing and non reversing mills.
In non reversing mills, rolls of equal size are rotated in a single rotation thereby the desired
shape is obtained.
In reversing rolling mill, the rolled product can be passed to and fro through the rolls by
reversing the direction of rotation. The diameter of the rolling mill is 600-1500 dia.
Merits:1. In a single pass large reductions are achieved.
2. The billet gets reduced to a strip.
3. Scaling problems are minimal.
4. There is no need of reheating as the ductility is not lost.
Demerits:1. Surface oxidation results in formation of scale.
2. The process is more is expensive as the temperature requirement is high.
3. More care is essential in handling heated part.
4. Skilled operator is required.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Applications:1. Hot rolling is used mainly to produce sheet metal or simple cross sections, such as rail
tracks.
2. Ring rolling is used to produce rings shapes for many such applications in
rockets, turbines, airplanes, pipes, and pressure vessels.
DRAWING
Definition:- It is the metal working operation where the metal deforms by the application of
tensile forces. There are 3 types of drawing operations they are:1. Wire drawing
2. Tube drawing
3. Tube sinking
Only ductile materials can be drawn. Drawing is generally used to manufacture of wires, but it is
also useful for bar and tube manufacture. The speed of the rollers are 6 mt/min and the pulling
force is 0.5-1.2 MN.
Wire drawing procedure:-
Initially we clean it by immersing it to the dilute hot solution of HCL which is termed as hot
pickling which is used to remove moisture, oil, grease etc. then it is washed in water and dipped
in the mixture of lime and water where the lime absorbs any amount of grease left. The wire to
be drawn is held in a loose coil and to start with the end of the rod is tagged, inserted through the
die and then finally locked in the gripper jaws of the bull block. When the bull block rotates at
high speeds it pulls the wire through the die, thereby reducing its section and winds up the drawn
wire.
Merits:1. Operation is simple.
2. Fine surface finish.
3. No problem of surface defects.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Demerits:1. Initial cost is high due to the usage of dies in production process.
2. Scaling problem exists due to oxidation of metals.
3. Skilled operator is required to handle the parts.
Applications: - Electrical wiring, spoke wheels of automotive components, musical instruments,
cables etc.
EXTRUSION
Definition:- It is the process of confing the metal in the closed cavity and then allowing it to
move in one opening so that the metal takes the shape of the desired size.
The materials that can be used are metals and alloys made up of aluminium, copper, lead and
magnesium (preferably which are of low working temperatures only should be used)
Types of extrusion:1. Direct extrusion
2. Indirect extrusion 3. Lateral extrusion
extrusion
5. Impact extrusion
4.
Hydrostatic
Procedure for direct extrusion:-
The hot billet is placed in the container and then compressive forces are applied on the metal
billet by a hydraulically driven ram. Due to these forces the billet gets squeezed and advances
into the container and then through the die opening. In this process the metal flow through
the die takes place in same direction as that of the ram movement and hence the term direct
extrusion.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Procedure for indirect extrusion:-
The die is carried by a hollow ram and it is forced against the hot metal billet. Under the
compressive loads the metal flows out of the die opening in a direction opposite to that of ram
movement. In this process the metal flow through the die takes place in a direction opposite to
that of the ram movement and hence the term indirect extrusion.
Merits:1. Process is simple and economical.
2. Good surface finish.
3. Low cost.
4. More productivity.
Demerits:1. Limited to lead, tin, magnesium, aluminum only.
2. Difficult to lubricate.
Applications: - Used in disposable tubes such as shaving cream, tooth paste, medical
tubes(ointment), milk containers. All these are made up of lead, tin, and aluminum. Some of the
materials that can be extruded are window frames, railing, door handles, gears, levers etc.
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
CASTING
Definition:- It is the process of producing the metal or alloy components parts of desired shapes
by pouring the molten metal into the mould and then allowing the metal/alloy to cool and
solidify. The solidified material is called as casting.
Terminology:-
1.
2.
3.
4.
5.
6.
7.
8.
Flask:- It is the external casing of both upper half(cope) and lower half(drag).
Pattern:- It is the replica of the object to be casted.
Parting line:- It shows that cope and drag are aligned properly.
Moulding sand:- It is the mixture of silica, clay and moisture.
Core:- To make the hollow cavities in the casting.
Sprue:- A passage way in which the molten metal reaches the mould cavity.
Runner:- A passage way which regulate the liquid metal to reach the mould cavity.
Riser:- It is the reservoir of molten metal so that the hot metal flows back to the mould
cavity once there is reduction of volume of metal.
Types of casting:1. Sand casting 2. Shell moulding casting
3. Centrifugal casting
4. Gravity die
casting
5. Precision investment casting
6. Permanent mould casting
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
Sand casting (Sand mould making procedure):-
1.
2.
3.
4.
5.
Place the lower flask(drag) on the floor having the clean flat surface.
Place the pattern on the centre of the flask.
Pour the dusting sand to avoid the sticking of moulding sand to pattern
Pour the moulding sand on to the lower flask until it is completely filled.
Start ramming it using the rammer and if found in excess strike off using striking bar
until the level of flask is reached.
6. Reverse the drag so that pattern is facing the top side.
7. Place the remaining half of pattern on the lower half of pattern and align it using the
dowel pins.
8. Introduce the sprue and riser until the lower half of pattern and place the upper
flask(cope) on top of it and pour the remaining moulding sand on to it and ram it until
level of flask is reached.
9. Using vent wire pierce the holes on cope to allow the escape of gases
10. Now withdraw the sprue and riser from cope and remove the cope
11. Remove the upper half of pattern from drag and lower half from the cope
12. Now align the drag with cope using dowel pins
13. Start pouring the molten metal into the mould cavity and allow it to cool and solidify.
14. The solidified part is the casting.
Advantages :1. Most versatile manufacturing process
2. Can produce machinable parts
3. Difficult shapes can be easily casted
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001
FORGING, ROLLING, DRAWING, EXTRUSION & CASTING
4. Iron can be casted easily which are found difficult in other processes
Disadvantages :1. Though casting is cheapest for MASS Production, it becomes non economical in case
of JOB production.
2. Sand casting leaves rough surface which needs machining in most of cases. It adds up the
cost in production.
3. Again in sand casting, poor dimensional accuracy is achieved.
Applications :1. Power generator casing
2. Turbine vanes
3. Foundation base of machine tools
4. Valves
5. Jet engine blades
6. Sanitary fittings
Prepared by Bhanupratap.R, Assistant Professor, Dept of Mech Engg, UVCE, Bengaluru-560001