UNIT 2 Bulkforming process mechanical.ppt
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About This Presentation
bulkforming
Slide Content
COURSE: MANUFACTURING PROCESSS
CODE: A40310
IV Semester
Regulation: R-23
G. Pullaiah College of Engineering and Technology
(Autonomous)
Pasupula, Kurnool- 518002
Dr G Praveen Kumar
Assistant Professor
Mechanical Engineering
Prepared by
CODE: A40310
IV Semester
Regulation: R-23
G. Pullaiah College of Engineering and Technology
(Autonomous)
Pasupula, Kurnool- 518002
Dr G Praveen Kumar
Assistant Professor
Mechanical Engineering
Prepared by
2
COURSE STRUCTURE
A40310 – MANUFACTURING PROCESSES
1. Course Description
Course Overview
• Know the working principle of different metal casting processes and gating system.
• Classify the welding processes, working of different types of welding processes and welding
defects.
• Know the nature of plastic deformation, cold and hot working process, working of a rolling mill
and types, extrusion processes.
• Understand the principles of forging, tools and dies, working of forging processes.
• Know about the Additive manufacturing.
Course Pre/corequisites
Engineering Workshop
COURSE STRUCTURE
A40310 – MANUFACTURING PROCESSES
1. Course Description
Course Overview
• Know the working principle of different metal casting processes and gating system.
• Classify the welding processes, working of different types of welding processes and welding
defects.
• Know the nature of plastic deformation, cold and hot working process, working of a rolling mill
and types, extrusion processes.
• Understand the principles of forging, tools and dies, working of forging processes.
• Know about the Additive manufacturing.
Course Pre/corequisites
Engineering Workshop
3
1. Course Outcomes (COs)
After the completion of the course, the student will be able to:
A40310.1 Design the patterns and core boxes for metal casting processes
A40310.2 Demonstrate the different types of bulk forming processes
A40310.3 Understand sheet metal forming processes
A40310.4 Understand the different welding processes
A40310.5 Learn about the different types of additive manufacturing processes
1. Course Outcomes (COs)
After the completion of the course, the student will be able to:
A40310.1 Design the patterns and core boxes for metal casting processes
A40310.2 Demonstrate the different types of bulk forming processes
A40310.3 Understand sheet metal forming processes
A40310.4 Understand the different welding processes
A40310.5 Learn about the different types of additive manufacturing processes
4
Course Syllabus
Casting: Steps involved in making a casting – Advantage of casting and its applications. Patterns and Pattern making – Types of
patterns – Materials used for patterns, pattern allowances and their construction, Molding, different types of cores , Principles of Gating,
Risers, casting design considerations. Methods of melting and types of furnaces, Solidification of castings and casting defects- causes
and remedies. Basic principles and applications of special casting processes - Centrifugal casting, Die casting, Investment casting and
shell molding.
UNIT I I
UNIT II I
Bulk Forming: Plastic deformation in metals and alloys-recovery, recrystallization and grain growth.
Hot working and Cold working-Strain hardening and Annealing. Bulk forming processes: Forging-Types of Forging, forging defects and
remedies; Rolling – fundamentals, types of rolling mills and products, Forces in rolling and power requirements. Extrusion and its
characteristics. Types of extrusion, Impact extrusion, Hydrostatic extrusion; Wire drawing and Tube drawing.
UNIT III I
Sheet metal forming-Blanking and piercing, Forces and power requirement in these operations, Deep drawing, Stretch forming, Bending,
Spring back and its remedies, Coining, Spinning, Types of presses and press tools.
High energy rate forming processes: Principles of explosive forming, electromagnetic forming, Electro hydraulic forming, rubber pad forming,
advantages and limitations.
UNIT IV I
Welding: Classification of welding processes, types of welded joints and their characteristics, Gas welding, Different types of flames and
uses, Oxy – Acetylene Gas cutting. Basic principles of Arc welding, power characteristics, Manual metal arc welding, submerged arc
welding, TIG& MIG welding. Electro–slag welding.
Resistance welding, Friction welding, Friction stir welding, Forge welding, Explosive welding; Thermit welding, Plasma Arc welding, Laser
welding, electron beam welding, Soldering &Brazing.
Heat affected zones in welding; pre & post heating, welding defects –causes and remedies.
UNIT V I
Additive manufacturing - Steps in Additive Manufacturing (AM), Classification of AM processes, Advantages of AM, and types of
materials for AM, VAT photopolymerization AM Processes, Extrusion - Based AM Processes, Powder Bed Fusion AM Processes, Direct
Energy Deposition AM Processes, Post Processing of AM Parts, Applications
Course Syllabus
Casting: Steps involved in making a casting – Advantage of casting and its applications. Patterns and Pattern making – Types of
patterns – Materials used for patterns, pattern allowances and their construction, Molding, different types of cores , Principles of Gating,
Risers, casting design considerations. Methods of melting and types of furnaces, Solidification of castings and casting defects- causes
and remedies. Basic principles and applications of special casting processes - Centrifugal casting, Die casting, Investment casting and
shell molding.
UNIT I I
UNIT II I
Bulk Forming: Plastic deformation in metals and alloys-recovery, recrystallization and grain growth.
Hot working and Cold working-Strain hardening and Annealing. Bulk forming processes: Forging-Types of Forging, forging defects and
remedies; Rolling – fundamentals, types of rolling mills and products, Forces in rolling and power requirements. Extrusion and its
characteristics. Types of extrusion, Impact extrusion, Hydrostatic extrusion; Wire drawing and Tube drawing.
UNIT III I
Sheet metal forming-Blanking and piercing, Forces and power requirement in these operations, Deep drawing, Stretch forming, Bending,
Spring back and its remedies, Coining, Spinning, Types of presses and press tools.
High energy rate forming processes: Principles of explosive forming, electromagnetic forming, Electro hydraulic forming, rubber pad forming,
advantages and limitations.
UNIT IV I
Welding: Classification of welding processes, types of welded joints and their characteristics, Gas welding, Different types of flames and
uses, Oxy – Acetylene Gas cutting. Basic principles of Arc welding, power characteristics, Manual metal arc welding, submerged arc
welding, TIG& MIG welding. Electro–slag welding.
Resistance welding, Friction welding, Friction stir welding, Forge welding, Explosive welding; Thermit welding, Plasma Arc welding, Laser
welding, electron beam welding, Soldering &Brazing.
Heat affected zones in welding; pre & post heating, welding defects –causes and remedies.
UNIT V I
Additive manufacturing - Steps in Additive Manufacturing (AM), Classification of AM processes, Advantages of AM, and types of
materials for AM, VAT photopolymerization AM Processes, Extrusion - Based AM Processes, Powder Bed Fusion AM Processes, Direct
Energy Deposition AM Processes, Post Processing of AM Parts, Applications
5
Various manufacturing operations on materials
In our daily life we use innumerable formed products e.g. cooking
vessels, tooth paste containers, bicycle body, chains, tube fitting,
fan blades etc.
Forming is the process of obtaining the required shape and size
on the raw material by subjecting the material to plastic
deformation through the application of tensile force,
compressive force, bending or shear force or combinations of
these forces.
Various manufacturing operations on materials
In our daily life we use innumerable formed products e.g. cooking
vessels, tooth paste containers, bicycle body, chains, tube fitting,
fan blades etc.
Forming is the process of obtaining the required shape and size
on the raw material by subjecting the material to plastic
deformation through the application of tensile force,
compressive force, bending or shear force or combinations of
these forces.
Metal Forming
Metal forming includes a large number of manufacturing
processes in which plastic deformation property is used to
change the shape and size of metal work pieces.
During the process, for deformation purpose, a tool
is used which is called as die. It applies stresses to the
material to exceed the yield strength of the metal.
Due to this the metal deforms into the shape ofthe die.
Generally, the stresses applied to deform the metal
plastically are compressive.
Metal forming includes a large number of manufacturing
processes in which plastic deformation property is used to
change the shape and size of metal work pieces.
During the process, for deformation purpose, a tool
is used which is called as die. It applies stresses to the
material to exceed the yield strength of the metal.
Due to this the metal deforms into the shape ofthe die.
Generally, the stresses applied to deform the metal
plastically are compressive.
Metal forming processes
stretching
General classification of metal forming processes
stretching
General classification of metal forming processes
BULK DEFORMATION PROCESSES:
Metal forming operations which cause significant shape
change by deformation in metal parts whose initial form
is bulk rather than sheet.
These processes work by stressing metal sufficiently to
cause plastic flow into desired shape.
Performed as cold, warm, and hot working operations.
In hot working, significant shape change can be
accomplished.
In cold working, strength can be increased during shape
change.
Little or no waste - some operations are near net shape
or net shape processes
8
Metal forming operations which cause significant shape
change by deformation in metal parts whose initial form
is bulk rather than sheet.
These processes work by stressing metal sufficiently to
cause plastic flow into desired shape.
Performed as cold, warm, and hot working operations.
In hot working, significant shape change can be
accomplished.
In cold working, strength can be increased during shape
change.
Little or no waste - some operations are near net shape
or net shape processes
8
Rolling:
Compressive deformation process in which the thickness of
a plate is reduced by squeezing it through two rotating
cylindrical rolls
Forging:
The work piece is compressed between two opposing dies so
that the die shapes are imparted to the work.
Extrusion:
The work material is forced to flow through a die opening
taking its shape.
Wire and Bar Drawing:
The diameter ofa wire or bar is reduced by pulling it
through a die opening (bar drawing) or a series ofdie
openings (wire drawing).
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Compressive deformation process in which the thickness of
a plate is reduced by squeezing it through two rotating
cylindrical rolls
Forging:
The work piece is compressed between two opposing dies so
that the die shapes are imparted to the work.
Extrusion:
The work material is forced to flow through a die opening
taking its shape.
Wire and Bar Drawing:
The diameter ofa wire or bar is reduced by pulling it
through a die opening (bar drawing) or a series ofdie
openings (wire drawing).
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Classification of basic bulk forming
processes
Rolling
Forging
Extrusion
Wire drawing
processes
Rolling
Forging
Extrusion
Wire drawing
Introduction Mechanical working ofa metal
Mechanical working of a metal is a simply plastic
deformation performed to change the dimensions,
properties and surface conditions with the help of
mechanical pressure.
Depending upon the temperature and strain rate,
mechanical working may be either hot working or cold
working, such that recovery process takes place
simultaneously with the deformation.
The plastic deformation of metal takes place due to
two factors i.e. deformation by slip and deformation by
twin formation.
Mechanical working of a metal is a simply plastic
deformation performed to change the dimensions,
properties and surface conditions with the help of
mechanical pressure.
Depending upon the temperature and strain rate,
mechanical working may be either hot working or cold
working, such that recovery process takes place
simultaneously with the deformation.
The plastic deformation of metal takes place due to
two factors i.e. deformation by slip and deformation by
twin formation.
Introduction Mechanical working ofa metal
During deformation the metal is said to flow, which is
called as plastic flow of the metal and grain shapes are
changed.
If the deformation is carried out at higher temperatures,
then the new grains start growing at the locations of
internal stresses.
When the temperature is sufficiently high, the grain
growth is accelerated and continue still the metal
comprises fully of new grains only.
During deformation the metal is said to flow, which is
called as plastic flow of the metal and grain shapes are
changed.
If the deformation is carried out at higher temperatures,
then the new grains start growing at the locations of
internal stresses.
When the temperature is sufficiently high, the grain
growth is accelerated and continue still the metal
comprises fully of new grains only.
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Introduction Mechanical working ofa metal
This process of formation of new grains is called as
recrystallisation and the corresponding temperature is the
recrystallisation temperature of the metal.
Recrystallisation temperature is the point which
differentiates hot working and cold working.
Mechanical working of metals above the
recrystallisation temperature, but below the melting or
burning point is known as hot working whereas; below
the recrystallisation temperature, is known as cold
working.
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Introduction Mechanical working ofa metal
This process of formation of new grains is called as
recrystallisation and the corresponding temperature is the
recrystallisation temperature of the metal.
Recrystallisation temperature is the point which
differentiates hot working and cold working.
Mechanical working of metals above the
recrystallisation temperature, but below the melting or
burning point is known as hot working whereas; below
the recrystallisation temperature, is known as cold
working.
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Plastic Deformation
− Any external or internal forces cause stresses in the
material resulting into deformation.
− Deformation is of two basic types :
o Elastic Deformation : Stress is below the elastic
limit,
o Plastic Deformation: Stress is above the elastic
limit.
− When the body regains its original shape on the
removal ofexternally applied force the deformation
is called as elastic deformation.
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Plastic Deformation
− Any external or internal forces cause stresses in the
material resulting into deformation.
− Deformation is of two basic types :
o Elastic Deformation : Stress is below the elastic
limit,
o Plastic Deformation: Stress is above the elastic
limit.
− When the body regains its original shape on the
removal ofexternally applied force the deformation
is called as elastic deformation.
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Plastic Deformation
Elastic deformation occurs up to the maximum
value of stress up to which the deformations are elastic or
temporary.
Stress required during elastic deformation is lower
than plastic deformation.
The plastic deformation is an important property of
metals and non-metals, due to which materials can be
deformed permanently and shaped as per the requirement.
Plastic deformation can be done through forming,
rolling, drawing, forging, etc.
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Plastic Deformation
Elastic deformation occurs up to the maximum
value of stress up to which the deformations are elastic or
temporary.
Stress required during elastic deformation is lower
than plastic deformation.
The plastic deformation is an important property of
metals and non-metals, due to which materials can be
deformed permanently and shaped as per the requirement.
Plastic deformation can be done through forming,
rolling, drawing, forging, etc.
Plastic Deformation
Plastic deformation may occur by :
Slip or
Twinning or
Both acting simultaneously
Plastic deformation is permanent and takes place when
the applied stress level exceeds a certain limit known
as yield stress[value of stress at a yield point or at the
yield strength .
Plastic deformation may occur by :
Slip or
Twinning or
Both acting simultaneously
Plastic deformation is permanent and takes place when
the applied stress level exceeds a certain limit known
as yield stress[value of stress at a yield point or at the
yield strength .
15
• Simple tension test:
(at lower temperatures, T < Tmelt/3)
tensile stress,
engineering strain,
Elastic
initially
Elastic+Plastic
at larger stress
permanent (plastic)
after load is removed
p
plastic strain
II. PLASTIC (PERMANENT) DEFORMATION
• Simple tension test:
(at lower temperatures, T < Tmelt/3)
tensile stress,
engineering strain,
Elastic
initially
Elastic+Plastic
at larger stress
permanent (plastic)
after load is removed
p
plastic strain
II. PLASTIC (PERMANENT) DEFORMATION
3
1. Initial2. Small load 3. Unload
Plastic means permanent!
F
linear
elastic
linear
elastic
plastic
planes
still
sheared
F
elastic + plastic
bonds
stretch
& planes
shear
plastic
II. PLASTIC DEFORMATION (METALS)
1. Initial2. Small load 3. Unload
Plastic means permanent!
F
linear
elastic
linear
elastic
plastic
planes
still
sheared
F
elastic + plastic
bonds
stretch
& planes
shear
plastic
II. PLASTIC DEFORMATION (METALS)
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Work Hardening
It is the phenomenon by which metals become harder and
stronger during mechanical working or straining i.e. during
plastic deformation of the metal.
After initial work hardening or straining, more and more
stress is required to further deform the material.
E.g. During the operation of hammering a nail, quite often
the nail bends. This bending of nail induces stress
development inside the nail.
The nail gets plastically deformed and work hardened or
strained.
Now if we try to straighten the nail, it requires more force
than that required to bend it.
Work hardening or Straining occurs below the re-
crystallization temperature
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Work Hardening
It is the phenomenon by which metals become harder and
stronger during mechanical working or straining i.e. during
plastic deformation of the metal.
After initial work hardening or straining, more and more
stress is required to further deform the material.
E.g. During the operation of hammering a nail, quite often
the nail bends. This bending of nail induces stress
development inside the nail.
The nail gets plastically deformed and work hardened or
strained.
Now if we try to straighten the nail, it requires more force
than that required to bend it.
Work hardening or Straining occurs below the re-
crystallization temperature
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HOT WORKING OF METALS:
oMechanical working of a metal above the
recrystallization temperature but below the melting point
is known as hot working.
oNormally, the recrystallization temperature of metal will
be about 30 to 40 % of its melting temperature.
RECRYSTALLIZATION TEMPERATURE:
oIt is defined by American Society of Metals: “ the
approximate minimum temperature at which
complete recrystallization of a cold worked metal
occurs within a specified time “.
oNormally, the recrystallization temperature will range
from 0.4 Tm to o.5 Tm.
oWhere, Tm = Melting point of the metal in absolute
scale.
21
oMechanical working of a metal above the
recrystallization temperature but below the melting point
is known as hot working.
oNormally, the recrystallization temperature of metal will
be about 30 to 40 % of its melting temperature.
RECRYSTALLIZATION TEMPERATURE:
oIt is defined by American Society of Metals: “ the
approximate minimum temperature at which
complete recrystallization of a cold worked metal
occurs within a specified time “.
oNormally, the recrystallization temperature will range
from 0.4 Tm to o.5 Tm.
oWhere, Tm = Melting point of the metal in absolute
scale.
21
22
Hot Working
During the hot working, the grains become loosened in their
structure, and they realign in a proper manner. Only small
pressure is required to shape the metal.
Hot Working
During the hot working, the grains become loosened in their
structure, and they realign in a proper manner. Only small
pressure is required to shape the metal.
Advantages of Hot Working:
oForce requirement is less when compared to cold working
process for making the required shape.
oIt is quick and economical process.
oPorosity is eliminated and density of the metal is
increased.
oThis process is very suitable for all metals.
oAs grain structure is refined, toughness, ductility, and
resistance can be improved.
Disadvantages of Hot Working:
oTooling and handling cost are high.
oSurface finish may be poor due to oxidation and scaling.
oSheets and wires cannot be produced.
23
oForce requirement is less when compared to cold working
process for making the required shape.
oIt is quick and economical process.
oPorosity is eliminated and density of the metal is
increased.
oThis process is very suitable for all metals.
oAs grain structure is refined, toughness, ductility, and
resistance can be improved.
Disadvantages of Hot Working:
oTooling and handling cost are high.
oSurface finish may be poor due to oxidation and scaling.
oSheets and wires cannot be produced.
23
TYPES OF HOT WORKING PROCESSES:
Hot Forging
a) Hammer Forging
b) Drop Forging
c) Upset Forging
d) Press Forging
e) Roll Forging
Hot Rolling
Hot Extrusion
Drawing
Swaging
Hot Spinning
24
Hot Forging
a) Hammer Forging
b) Drop Forging
c) Upset Forging
d) Press Forging
e) Roll Forging
Hot Rolling
Hot Extrusion
Drawing
Swaging
Hot Spinning
24
COLD WORKING OF METALS:
oMechanical working of a metal below the
recrystallization temperature is known as cold working.
oThe recrystallization temperature is about one half of the
absolute melting temperature but generally cold working
is carried out only at room temperature.
Materials Used for Cold Working:
Low and Medium Carbon Steel
Copper and Light Alloys
Materials like Al, Mg, Titanium
25
oMechanical working of a metal below the
recrystallization temperature is known as cold working.
oThe recrystallization temperature is about one half of the
absolute melting temperature but generally cold working
is carried out only at room temperature.
Materials Used for Cold Working:
Low and Medium Carbon Steel
Copper and Light Alloys
Materials like Al, Mg, Titanium
25
Advantages of Cold Working:
oBetter surface finish is being obtained.
oThis process provides higher dimensional accuracy
oWidely applied as a forming process for steel.
oThin material can be obtained.
oMore suitable for mass production.
Disadvantages of Cold Working:
oClose tolerances cannot be achieved.
oBrittle materials cannot be cold worked.
oStress formation in the metal during cold working is
higher.
oHeavy force is required to accomplish deformation of the
material.
26
oBetter surface finish is being obtained.
oThis process provides higher dimensional accuracy
oWidely applied as a forming process for steel.
oThin material can be obtained.
oMore suitable for mass production.
Disadvantages of Cold Working:
oClose tolerances cannot be achieved.
oBrittle materials cannot be cold worked.
oStress formation in the metal during cold working is
higher.
oHeavy force is required to accomplish deformation of the
material.
26
27
Cold Working
Cold Working
28
Cold Working
Cold Working
TYPES OF COLD WORKING PROCESSES:
Drawing
a) Blank Drawingb) Wire Drawing
c) Tube Drawingd) Metal Spinning
e) Embossing
Squeezing
a) Coiningb) Sizingc) Swaging
d) Knurlinge) Extrusion
Bending
a) Plate Bending
b) Angle Bending
c) Roll Forming
d) Seaming
29
Drawing
a) Blank Drawingb) Wire Drawing
c) Tube Drawingd) Metal Spinning
e) Embossing
Squeezing
a) Coiningb) Sizingc) Swaging
d) Knurlinge) Extrusion
Bending
a) Plate Bending
b) Angle Bending
c) Roll Forming
d) Seaming
29
30
HOT AND COLD WORKING:
31
31
32
Strain Hardening
Strain hardening (also called work-hardening or cold-
working) is the process of making a metal harder and
stronger through plastic deformation.
When a metal is plastically deformed, dislocations move
and additional dislocations are generated.
The more dislocations within a material, the more they
will interact and become pinned or tangled.
This will result in a decrease in the mobility of the
dislocations and a strengthening of the material.
This type of strengthening is commonly called cold-
working.
Strain Hardening
Strain hardening (also called work-hardening or cold-
working) is the process of making a metal harder and
stronger through plastic deformation.
When a metal is plastically deformed, dislocations move
and additional dislocations are generated.
The more dislocations within a material, the more they
will interact and become pinned or tangled.
This will result in a decrease in the mobility of the
dislocations and a strengthening of the material.
This type of strengthening is commonly called cold-
working.
6strain hardening
34
Strain Hardening
It is called cold-working because the plastic deformation must
occurs at a temperature low enough that atoms cannot rearrange
themselves.
When a metal is worked at higher temperatures (hot-working) the
dislocations can rearrange and little strengthening is achieved.
Strain hardening can be easily demonstrated with piece of wire or a
paper clip. Bend a straight section back and forth several times.
Notice that it is more difficult to bend the metal at the same place.
In the strain hardened area dislocations have formed and become
tangled, increasing the strength of the material.
Strain Hardening
It is called cold-working because the plastic deformation must
occurs at a temperature low enough that atoms cannot rearrange
themselves.
When a metal is worked at higher temperatures (hot-working) the
dislocations can rearrange and little strengthening is achieved.
Strain hardening can be easily demonstrated with piece of wire or a
paper clip. Bend a straight section back and forth several times.
Notice that it is more difficult to bend the metal at the same place.
In the strain hardened area dislocations have formed and become
tangled, increasing the strength of the material.
35
Strain Hardening
Strain Hardening
36
Strain Hardening
Effects of Elevated Temperature on Strain Hardened Materials
When strain hardened materials are exposed to elevated
temperatures, the strengthening that resulted from the plastic
deformation can be lost. This can be a bad thing if the
strengthening is needed to support a load. However,
strengthening due to strain hardening is not always desirable,
especially if the material is being heavily formed since ductility
will be lowered.
Strain Hardening
Effects of Elevated Temperature on Strain Hardened Materials
When strain hardened materials are exposed to elevated
temperatures, the strengthening that resulted from the plastic
deformation can be lost. This can be a bad thing if the
strengthening is needed to support a load. However,
strengthening due to strain hardening is not always desirable,
especially if the material is being heavily formed since ductility
will be lowered.
37
Strain Hardening
Effects of Elevated Temperature on Strain Hardened Materials
Heat treatment can be used to remove the effects of strain
hardening. Three things can occur during heat treatment:
1.Recovery
2.Recrystallization
3.Grain growth
Strain Hardening
Effects of Elevated Temperature on Strain Hardened Materials
Heat treatment can be used to remove the effects of strain
hardening. Three things can occur during heat treatment:
1.Recovery
2.Recrystallization
3.Grain growth
38
Strain Hardening
When a strain hardened material is held at an elevated
temperature an increase in atomic diffusion occurs that relieves
some of the internal strain energy. Remember that atoms are not
fixed in position but can move around when they have enough
energy to break their bonds. Diffusion increases rapidly with
rising temperature and this allows atoms in severely strained
regions to move to unstrained positions.
1. Recovery
Strain Hardening
When a strain hardened material is held at an elevated
temperature an increase in atomic diffusion occurs that relieves
some of the internal strain energy. Remember that atoms are not
fixed in position but can move around when they have enough
energy to break their bonds. Diffusion increases rapidly with
rising temperature and this allows atoms in severely strained
regions to move to unstrained positions.
1. Recovery
39
Strain Hardening
In other words, atoms are free to move around and recover a
normal position in the lattice structure. This is known as the
recovery phase and it results in an adjustment of strain on a
microscopic scale. Internal residual stresses are lowered due to a
reduction in the dislocation density and a movement of
dislocation to lower-energy positions.
Recovery
Strain Hardening
In other words, atoms are free to move around and recover a
normal position in the lattice structure. This is known as the
recovery phase and it results in an adjustment of strain on a
microscopic scale. Internal residual stresses are lowered due to a
reduction in the dislocation density and a movement of
dislocation to lower-energy positions.
Recovery
40
Strain Hardening
The tangles of dislocations condense into sharp two-dimensional
boundaries and the dislocation density within these areas
decrease. These areas are called subgrains. There is no
appreciable reduction in the strength and hardness of the
material but corrosion resistance often improves.
Recovery
Strain Hardening
The tangles of dislocations condense into sharp two-dimensional
boundaries and the dislocation density within these areas
decrease. These areas are called subgrains. There is no
appreciable reduction in the strength and hardness of the
material but corrosion resistance often improves.
Recovery
41
Strain Hardening
At a higher temperature, new, strain-free grains nucleate and
grow inside the old distorted grains and at the grain boundaries.
These new grains grow to replace the deformed grains produced
by the strain hardening. With recrystallization, the mechanical
properties return to their original weaker and more ductile
states. Recrystallization depends on the temperature, the
amount of time at this temperature and also the amount of
strain hardening that the material experienced.
2. Recrystallization
Strain Hardening
At a higher temperature, new, strain-free grains nucleate and
grow inside the old distorted grains and at the grain boundaries.
These new grains grow to replace the deformed grains produced
by the strain hardening. With recrystallization, the mechanical
properties return to their original weaker and more ductile
states. Recrystallization depends on the temperature, the
amount of time at this temperature and also the amount of
strain hardening that the material experienced.
2. Recrystallization
42
Strain Hardening
The more strain hardening, the lower the temperature will be at
which recrystallization occurs. Also, a minimum amount (typically
2-20%) of cold work is necessary for any amount of
recrystallization to occur. The size the new grains is also partially
dependant on the amount of strain hardening. The greater the
stain hardening, the more nuclei for the new grains, and the
resulting grain size will be smaller (at least initially).
2. Recrystallization
Strain Hardening
The more strain hardening, the lower the temperature will be at
which recrystallization occurs. Also, a minimum amount (typically
2-20%) of cold work is necessary for any amount of
recrystallization to occur. The size the new grains is also partially
dependant on the amount of strain hardening. The greater the
stain hardening, the more nuclei for the new grains, and the
resulting grain size will be smaller (at least initially).
2. Recrystallization
43
Strain Hardening
If a specimen is left at the high temperature beyond the time
needed for complete recrystallization, the grains begin to grow in
size. This occurs because diffusion occurs across the grain
boundaries and larger grains have less grain boundary surface
area per unit of volume. Therefore, the larger grains lose fewer
atoms and grow at the expense of the smaller grains. Larger
grains will reduce the strength and toughness of the material.
3. Grain Growth
Strain Hardening
If a specimen is left at the high temperature beyond the time
needed for complete recrystallization, the grains begin to grow in
size. This occurs because diffusion occurs across the grain
boundaries and larger grains have less grain boundary surface
area per unit of volume. Therefore, the larger grains lose fewer
atoms and grow at the expense of the smaller grains. Larger
grains will reduce the strength and toughness of the material.
3. Grain Growth
44
Strain Hardening
Strain Hardening
ANNEALING
Annealing is done when strain
hardened materials are exposed to
heat above recrystallization
temperature for definite time and
then it is cooled at room
temperature.
•It has 3 basic stages :
•RECOVERY
•RECRYSTALLIZATION
•GRAIN GROWTH
1
5
Annealing is done when strain
hardened materials are exposed to
heat above recrystallization
temperature for definite time and
then it is cooled at room
temperature.
•It has 3 basic stages :
•RECOVERY
•RECRYSTALLIZATION
•GRAIN GROWTH
1
5
Recovery
•The relief of some of the internal strain energy of a previously cold-
worked material.
•Relieves the stresses from cold working
•Recovery involves annihilation of point defects.
•Driving force for recovery is decrease in stored energy from cold work.
•During recovery, physical properties of the cold worked material are
restored without any observable change in microstructure.
•Recovery is first stage of annealing which takes place at low
temperatures of annealing.
•There is some reduction, though not substantial, in dislocation density
as well apart from formation of dislocation configurations with low
strain energies.
•The relief of some of the internal strain energy of a previously cold-
worked material.
•Relieves the stresses from cold working
•Recovery involves annihilation of point defects.
•Driving force for recovery is decrease in stored energy from cold work.
•During recovery, physical properties of the cold worked material are
restored without any observable change in microstructure.
•Recovery is first stage of annealing which takes place at low
temperatures of annealing.
•There is some reduction, though not substantial, in dislocation density
as well apart from formation of dislocation configurations with low
strain energies.
Recovery
•Let us now examine the changes that occur when a
sample is heated from room temperature.
•At first, recovery occurs in which there is a change in the
stored energy without any obvious change in the
optical microstructure.
•Excess vacancies and interstitials anneal out giving a
drop in the electrical resistivity.
•Dislocations become mobile at a higher temperature,
eliminate and rearrange to give polygonization.
•Modest effects on mechanical behaviour
•Let us now examine the changes that occur when a
sample is heated from room temperature.
•At first, recovery occurs in which there is a change in the
stored energy without any obvious change in the
optical microstructure.
•Excess vacancies and interstitials anneal out giving a
drop in the electrical resistivity.
•Dislocations become mobile at a higher temperature,
eliminate and rearrange to give polygonization.
•Modest effects on mechanical behaviour
Recrystallization
This follows recovery during annealing of cold worked
material. Driving force is stored energy during cold work.
It involves replacement of cold-worked structure by a new
set of strain-free, approximately equi-axed grains to replace
all the deformed crystals.
This process ocurs above recrystallisation temperature which
is defined as the temperature at which 50% of material
recrystallises in one hour time.
The recrystallization temperature is strongly dependent on
the purity of a material.
Pure materials may recrystallize around 0.3Tm, while impure
materials may recrystallise around 0.4Tm, where Tm is
absolute melting temperature of the material.
This follows recovery during annealing of cold worked
material. Driving force is stored energy during cold work.
It involves replacement of cold-worked structure by a new
set of strain-free, approximately equi-axed grains to replace
all the deformed crystals.
This process ocurs above recrystallisation temperature which
is defined as the temperature at which 50% of material
recrystallises in one hour time.
The recrystallization temperature is strongly dependent on
the purity of a material.
Pure materials may recrystallize around 0.3Tm, while impure
materials may recrystallise around 0.4Tm, where Tm is
absolute melting temperature of the material.
Recrystallization
•The nucleation of new grains happens in regions
of high dislocation density.
•Nucleation begins in a jumble of dislocations. The
recrystallised grain will essentially be free from
dislocations.
•A greater nucleation rate leads to a finer ultimate
grain size.
•There is a critical level of deformation below
which there will be no recrystallisation at all.
•A critical strain anneal can lead to a single crystal
recrystallisation.
•The nucleation of new grains happens in regions
of high dislocation density.
•Nucleation begins in a jumble of dislocations. The
recrystallised grain will essentially be free from
dislocations.
•A greater nucleation rate leads to a finer ultimate
grain size.
•There is a critical level of deformation below
which there will be no recrystallisation at all.
•A critical strain anneal can lead to a single crystal
recrystallisation.
Grain growth
Grain growth follows complete crystallization if the material
is left at elevated temperatures.
Grain growth does not need to be preceded by recovery and
recrystallization; it may occur in all polycrystalline materials.
In contrary to recovery and recrystallization, driving force for
this process is reduction in grain boundary energy.
Tendency for larger grains to grow at the expense of smaller
grains is based on physics.
In practical applications, grain growth is not desirable.
Incorporation of impurity atoms and insoluble second phase
particles are effective in retarding grain growth.
Grain growth is very strongly dependent on temperature
Grain growth follows complete crystallization if the material
is left at elevated temperatures.
Grain growth does not need to be preceded by recovery and
recrystallization; it may occur in all polycrystalline materials.
In contrary to recovery and recrystallization, driving force for
this process is reduction in grain boundary energy.
Tendency for larger grains to grow at the expense of smaller
grains is based on physics.
In practical applications, grain growth is not desirable.
Incorporation of impurity atoms and insoluble second phase
particles are effective in retarding grain growth.
Grain growth is very strongly dependent on temperature
METAL FORGING
PROCESS
PROCESS
INTRODUCTION
Forging is a manufacturing process
involving the shaping of metal using
localized compressive forces. Forging is
often classified according to the
temperature at which it is performed:
"cold", "warm", or "hot" forging. Forged
parts can range in weight from less than
a kilogram to 580 metric tons.Forged
parts usually require further processing
to achieve a finished part.
Forging is a manufacturing process
involving the shaping of metal using
localized compressive forces. Forging is
often classified according to the
temperature at which it is performed:
"cold", "warm", or "hot" forging. Forged
parts can range in weight from less than
a kilogram to 580 metric tons.Forged
parts usually require further processing
to achieve a finished part.
Forging
Forging Operations
Upsetting Bending Drawing down Cutting
Flattening
Fullering
Forge
Welding
Swaging
Upsetting Bending Drawing down Cutting
Flattening
Fullering
Forge
Welding
Swaging
FORGING:
In this process, the desired shape is obtained by the
application of a compressive force.
In hot forging, the metal is heated above the
recrystallization temperature.
Then it is compressed and squeezed to the required shape
by using hammer or press tool.
TYPES OF FORGING:
Smith or Open Die Forging
a) Hand Forgingb) Power Forging
Impression or Closed Die Forging
a) Drop Forging b) Press Forging c) Upset Forging
Roll Forging
56
In this process, the desired shape is obtained by the
application of a compressive force.
In hot forging, the metal is heated above the
recrystallization temperature.
Then it is compressed and squeezed to the required shape
by using hammer or press tool.
TYPES OF FORGING:
Smith or Open Die Forging
a) Hand Forgingb) Power Forging
Impression or Closed Die Forging
a) Drop Forging b) Press Forging c) Upset Forging
Roll Forging
56
SMITH OR OPEN DIE FORGING:
oIn this process, the forging is done in a heated work at
the proper temperature by placing on flat surface of
anvil through hammering the metal piece.
•Deformation operation reduces height and increases
diameter of work.
57
oIn this process, the forging is done in a heated work at
the proper temperature by placing on flat surface of
anvil through hammering the metal piece.
•Deformation operation reduces height and increases
diameter of work.
57
oHeavy forgings weighing up to 25,000kg are
produced.
oThis forging is very simple and flexible.
oMuch useful for producing simple shapes like U bolts,
Chisels, Rectangular, Circular, Hexagonal shapes.
a) HAND FORGING:
oThe metal is heated and placed over the anvil by using
tongs.
oOne side of the former is held on the parts to be forged
while the other side is struck with a sledge by a helper.
oRepeated blows are given by a sledge hammer to
obtain the metal into required shape.
58
produced.
oThis forging is very simple and flexible.
oMuch useful for producing simple shapes like U bolts,
Chisels, Rectangular, Circular, Hexagonal shapes.
a) HAND FORGING:
oThe metal is heated and placed over the anvil by using
tongs.
oOne side of the former is held on the parts to be forged
while the other side is struck with a sledge by a helper.
oRepeated blows are given by a sledge hammer to
obtain the metal into required shape.
58
COMMON HAND FORGING TOOLS
Tong Flatter Swage Fuller Punch
Rivet
header
Hot
chisel
Hammer
s
Anvil Swage
block
Drift Brass
scale
Brush
Heading
tool
Tong Flatter Swage Fuller Punch
Rivet
header
Hot
chisel
Hammer
s
Anvil Swage
block
Drift Brass
scale
Brush
Heading
tool
b) POWER FORGING:
oIn forging, power hammer or power presses are used.
oPower hammer provides greater capacity, in which the
ram is accelerated on the down stroke by steam or air
pressure in addition to gravity.
oIn power hammer, a suddenly falling weight which
strikes on the metal makes into required shape.
oIn power press, the compressive force is used to shape
the metal.
60
oIn forging, power hammer or power presses are used.
oPower hammer provides greater capacity, in which the
ram is accelerated on the down stroke by steam or air
pressure in addition to gravity.
oIn power hammer, a suddenly falling weight which
strikes on the metal makes into required shape.
oIn power press, the compressive force is used to shape
the metal.
60
ADVANDAGES & DISADVANTAGES SMITH OR
OPEN DIE FORGING :
Advantages
•Simple, inexpensive dies;
•Wide range of sizes;
•Good strength
Limitations
•Simple shapes only;
•Difficult to hold close tolerances;
•Machining necessary;
•Low production rate;
•Poor utilization of material;
•High skill required
61
OPEN DIE FORGING :
Advantages
•Simple, inexpensive dies;
•Wide range of sizes;
•Good strength
Limitations
•Simple shapes only;
•Difficult to hold close tolerances;
•Machining necessary;
•Low production rate;
•Poor utilization of material;
•High skill required
61
IMPRESSION OR CLOSED DIE FORGING:
oIn this process, the forging is done by squeezing the
work piece between two shaped and closed dies.
62
oIn this process, the forging is done by squeezing the
work piece between two shaped and closed dies.
62
a) DROP FORGING:
oIn this, impression dies called closed dies are used.
oThe upper die is fitted on the ram and the lower
die is fitted on the anvil.
oBoth the dies have impressions.
oTwo rollers are fixed on the board when the rolls
rotate opposite to each other.
oIt drives the board upward and lifting the ram.
oWhen the rolls are released, the ram will falls
down and producing a working stroke.
oA single blow of press makes small and simple
parts and large complicate shapes are made by no.
of steps.
oApplications: Spanner, Automobile & Machine
parts.
63
oIn this, impression dies called closed dies are used.
oThe upper die is fitted on the ram and the lower
die is fitted on the anvil.
oBoth the dies have impressions.
oTwo rollers are fixed on the board when the rolls
rotate opposite to each other.
oIt drives the board upward and lifting the ram.
oWhen the rolls are released, the ram will falls
down and producing a working stroke.
oA single blow of press makes small and simple
parts and large complicate shapes are made by no.
of steps.
oApplications: Spanner, Automobile & Machine
parts.
63
b) PRESS FORGING:
oIt is done by a press. The press may be operated either
mechanically or hydraulically.
oThe action is relatively slow squeezing rather than
delivering heavy blows.
oThere is anvil to fix the lower die and the upper die is
fitted fix in the ram.
oThe ram is allowed to move down slowly and presses
the metal slowly with high pressure.
oThe finished component may be automatically
removed by providing ejectors in the die set.
oThe capacity range from 50 x 10³ to 80 x 10^5 kg and
speeds vary from 34 to 40 strokes per minute.
oApplications: Spanner, Connecting Rod, Machine
Components
64
oIt is done by a press. The press may be operated either
mechanically or hydraulically.
oThe action is relatively slow squeezing rather than
delivering heavy blows.
oThere is anvil to fix the lower die and the upper die is
fitted fix in the ram.
oThe ram is allowed to move down slowly and presses
the metal slowly with high pressure.
oThe finished component may be automatically
removed by providing ejectors in the die set.
oThe capacity range from 50 x 10³ to 80 x 10^5 kg and
speeds vary from 34 to 40 strokes per minute.
oApplications: Spanner, Connecting Rod, Machine
Components
64
c) UPSET FORGING:
•Upset forging increases the diameter of the work
piece by compressing its length.
oIt is process of increasing the cross sectional area
of the bar at the expense of its height.
oIt is used to form head of bolt and rivet or pins.
oThe head may be square, hexagonal or
hemispherical.
oThe machine is having a die set.
oThe die set consists of a fixed die and movable
punch.
oThe heated metal bar is held inside the solid die
and the force is given to the punch.
oSo, the punch will squeeze the heated metal to the
shape of the die cavity.
65
•Upset forging increases the diameter of the work
piece by compressing its length.
oIt is process of increasing the cross sectional area
of the bar at the expense of its height.
oIt is used to form head of bolt and rivet or pins.
oThe head may be square, hexagonal or
hemispherical.
oThe machine is having a die set.
oThe die set consists of a fixed die and movable
punch.
oThe heated metal bar is held inside the solid die
and the force is given to the punch.
oSo, the punch will squeeze the heated metal to the
shape of the die cavity.
65
ADVANDAGES & DISADVANTAGES
IMPRESSION OR CLOSED DIE FORGING :
Advantages
•Good utilization of material;
•Better properties than open die forging;
•Good dimensional accuracy;
•High production rate;
•Good reproducibility
Limitations
•High die cost for small quantities;
•Machining often necessary
66
IMPRESSION OR CLOSED DIE FORGING :
Advantages
•Good utilization of material;
•Better properties than open die forging;
•Good dimensional accuracy;
•High production rate;
•Good reproducibility
Limitations
•High die cost for small quantities;
•Machining often necessary
66
ROLL FORGING:
oRoll forging is a process where round or flat bar stock is
reduced in thickness and increased in length.
oIn this process, heated metal bar is passed between the
two rolls. Roll forging is performed by an impression die
forging operation.
oA piece of heated stock is passed between the two rolls.
As the rolls rotate, the heated metal is squeezed.
67
oRoll forging is a process where round or flat bar stock is
reduced in thickness and increased in length.
oIn this process, heated metal bar is passed between the
two rolls. Roll forging is performed by an impression die
forging operation.
oA piece of heated stock is passed between the two rolls.
As the rolls rotate, the heated metal is squeezed.
67
•SWAGING
Process that reduces/increases the diameter, tapers, rods
or points round bars or tubes by external hammering.
•Mandrel sometimes required to control shape and size of
internal diameter of tubular parts
68
Process that reduces/increases the diameter, tapers, rods
or points round bars or tubes by external hammering.
•Mandrel sometimes required to control shape and size of
internal diameter of tubular parts
68
•COLD FORGING
Process in which slugs of material are squeezed into
shaped die cavities to produce finished parts of precise
shape and size.
69
Process in which slugs of material are squeezed into
shaped die cavities to produce finished parts of precise
shape and size.
69
FORGING HAMMERS:
•Apply an impact load against work part - two types:
–GRAVITY DROP HAMMERS - impact energy
from falling weight of a heavy ram
–POWER DROP HAMMERS - accelerate the ram
by pressurized air or steam
•Disadvantage:
•Impact energy
transmitted through anvil
into floor of building
•Most commonly used
for impression-die forging
70
•Apply an impact load against work part - two types:
–GRAVITY DROP HAMMERS - impact energy
from falling weight of a heavy ram
–POWER DROP HAMMERS - accelerate the ram
by pressurized air or steam
•Disadvantage:
•Impact energy
transmitted through anvil
into floor of building
•Most commonly used
for impression-die forging
70
FORGING HAMMERS:
71
71
FORGING PRESSES:
•Apply gradual pressure to accomplish compression
operation - types:
–MECHANICAL PRESSES - converts rotation of
drive motor into linear motion of ram
–HYDRAULIC PRESSES - hydraulic piston actuates
ram. (See next slide)
–SCREW PRESSES - screw mechanism drives ram
72
•Apply gradual pressure to accomplish compression
operation - types:
–MECHANICAL PRESSES - converts rotation of
drive motor into linear motion of ram
–HYDRAULIC PRESSES - hydraulic piston actuates
ram. (See next slide)
–SCREW PRESSES - screw mechanism drives ram
72
73
FORGING PRESSES:
74
74
ADVANTAGES OF FORGING
1. Forged parts possess high ductility and offers great resistance to impact
and fatigue loads.
2. Forging refines the structure of the metal.
3. It results in considerable saving in time, labor and material as compared
to the production of similar item by cutting from a solid stock and then
shaping it.
4. Forging distorts the previously created unidirectional fiber as created by
rolling and increases the strength by setting the direction of grains.
5. Because of intense working, flaws are rarely found, so have good
reliability.
6. The reasonable degree of accuracy may be obtained in forging
operation.
7. The forged parts can be easily welded.
1. Forged parts possess high ductility and offers great resistance to impact
and fatigue loads.
2. Forging refines the structure of the metal.
3. It results in considerable saving in time, labor and material as compared
to the production of similar item by cutting from a solid stock and then
shaping it.
4. Forging distorts the previously created unidirectional fiber as created by
rolling and increases the strength by setting the direction of grains.
5. Because of intense working, flaws are rarely found, so have good
reliability.
6. The reasonable degree of accuracy may be obtained in forging
operation.
7. The forged parts can be easily welded.
Disadvantages of Forging
1. Rapid oxidation in forging of metal surface at high temperature results
in scaling which wears the dies.
2. The close tolerances in forging operations are difficult to maintain.
3. Forging is limited to simple shapes and has limitation for parts having
undercuts etc.
4. Some materials are not readily worked by forging.
5. The initial cost of forging dies and the cost of their maintenance is
high.
6. The metals gets cracked or distorted if worked below a specified
temperature limit.
7. The maintenance cost of forging dies is also very high.
1. Rapid oxidation in forging of metal surface at high temperature results
in scaling which wears the dies.
2. The close tolerances in forging operations are difficult to maintain.
3. Forging is limited to simple shapes and has limitation for parts having
undercuts etc.
4. Some materials are not readily worked by forging.
5. The initial cost of forging dies and the cost of their maintenance is
high.
6. The metals gets cracked or distorted if worked below a specified
temperature limit.
7. The maintenance cost of forging dies is also very high.
DEFECTS IN FORGED PARTS
1. Cold shut: This appears as a small crack at the corners of the forging.
Reasons
Due to improper design of die.
2.Unfilled sections : In this, some sections of the die cavity are not
completely filled by the following metal.
Reasons
Improper design of forging die or using faulty design techniques.
3. Scale pits: This is seen as irregular depressions on the surface of forging.
Reason
These are formed by squeezing of scale into the metal surface during forging.
4. Die shift: This is caused by the misalignment of the die halves, making the
two halves of the forging to be improper shape.
5. Oversize components
Reasons
Due to worn out dies, incorrect dies, misalignment of die halves.
1. Cold shut: This appears as a small crack at the corners of the forging.
Reasons
Due to improper design of die.
2.Unfilled sections : In this, some sections of the die cavity are not
completely filled by the following metal.
Reasons
Improper design of forging die or using faulty design techniques.
3. Scale pits: This is seen as irregular depressions on the surface of forging.
Reason
These are formed by squeezing of scale into the metal surface during forging.
4. Die shift: This is caused by the misalignment of the die halves, making the
two halves of the forging to be improper shape.
5. Oversize components
Reasons
Due to worn out dies, incorrect dies, misalignment of die halves.
78
Closed and open die forging processes
ROLLING FUNDAMENTALS
80
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80
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ROLLING FUNDAMENTALS
81
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81
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ROLLING FUNDAMENTALS
82
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82
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ROLLING FUNDAMENTALS
83
Fundamental concept of metal rolling
1)The arc of contact between the rolls and the metal is a part of a circle.
2)The coefficient of friction, µ, is constant in theory, but in reality µ varies along the
arc of contact.
3)The metal is considered to deform plastically during rolling.
4)The volume of metal is constant before and after rolling. In practical the volume
might decrease a little bit due to close-up of pores.
5)The velocity of the rolls is assumed to be constant.
6)The metal only extends in the rolling direction and no extension in the width of
the material.
7)The cross sectional area normal to the rolling direction is not distorted.
10/19/25 83
83
Fundamental concept of metal rolling
1)The arc of contact between the rolls and the metal is a part of a circle.
2)The coefficient of friction, µ, is constant in theory, but in reality µ varies along the
arc of contact.
3)The metal is considered to deform plastically during rolling.
4)The volume of metal is constant before and after rolling. In practical the volume
might decrease a little bit due to close-up of pores.
5)The velocity of the rolls is assumed to be constant.
6)The metal only extends in the rolling direction and no extension in the width of
the material.
7)The cross sectional area normal to the rolling direction is not distorted.
10/19/25 83
FORCES AND GEOMETRICAL
RELATIONSHIPS IN ROLLING
A metal sheet with a thickness ho enters the rolls at the entrance plane xx with a
velocity vo. It passes through the roll gap and leaves the exit plane yy with a
reduced thickness hf and at a velocity vf. Given that there is no increase in width,
the vertical compression of the metal is translated into an elongation in the rolling
direction.
Where b is the width of the sheet v is the velocity at any thickness h intermediate
between ho and hf .
84
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RELATIONSHIPS IN ROLLING
A metal sheet with a thickness ho enters the rolls at the entrance plane xx with a
velocity vo. It passes through the roll gap and leaves the exit plane yy with a
reduced thickness hf and at a velocity vf. Given that there is no increase in width,
the vertical compression of the metal is translated into an elongation in the rolling
direction.
Where b is the width of the sheet v is the velocity at any thickness h intermediate
between ho and hf .
84
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FLAT ROLLING AND ITS ANALYSIS:
85
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85
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86
Process of Rolling
Rolling process has three steps to complete the product
Process of Rolling
Rolling process has three steps to complete the product
87
Process of Rolling
Sequence of operations involved in manufacturing rolled products
1.Primary Rolling:
Primary rolling is used to convert metal ingot to simple stock
members like blooms and slabs. This process refines the
structure of casted ingot, improves its mechanical properties,
and eliminates the hidden internal defects.
Process of Rolling
Sequence of operations involved in manufacturing rolled products
1.Primary Rolling:
Primary rolling is used to convert metal ingot to simple stock
members like blooms and slabs. This process refines the
structure of casted ingot, improves its mechanical properties,
and eliminates the hidden internal defects.
88
Process of Rolling
Sequence of operations involved in manufacturing rolled products
2. Hot Rolling:
Blooms and slabs obtained from primary rolling, again
converted into plates, sheets, rods and structural shapes, by hot
rolling process.
Process of Rolling
Sequence of operations involved in manufacturing rolled products
2. Hot Rolling:
Blooms and slabs obtained from primary rolling, again
converted into plates, sheets, rods and structural shapes, by hot
rolling process.
89
Process of Rolling
Sequence of operations involved in manufacturing rolled products
3. Cold Rolling:
Cold rolling is usually a finishing process in which products
made by hot rolling are given a final shape. These processes
provide good surface finish, closer dimensional tolerances and
enhance mechanical strength of the material.
The steel which we get from re-melting shop or from steel
manufacturing plants is mostly in the form of ingots. Ingots
have a roughly square cross section of 1.5m x 1.5m, and
weighing in tonnes.
Process of Rolling
Sequence of operations involved in manufacturing rolled products
3. Cold Rolling:
Cold rolling is usually a finishing process in which products
made by hot rolling are given a final shape. These processes
provide good surface finish, closer dimensional tolerances and
enhance mechanical strength of the material.
The steel which we get from re-melting shop or from steel
manufacturing plants is mostly in the form of ingots. Ingots
have a roughly square cross section of 1.5m x 1.5m, and
weighing in tonnes.
90
Process of Rolling
These ingots are first heated to about 1200°C in soaking pits and
then passed through rollers to produce intermedials shapes
such as blooms. The blooms are rolled to billets and the billets
to the desired sections like flat, square, hexagonal, angle, I,U,
etc. The above mentioned member has following sizes
approximately.
Casted Ingots — 1.5 m x 1.5 m (Rectangular cross-section)
Blooms — 150 mm to 400 mm square.
Slabs— Width: 500 to 1800 mm (Rectangular cross-section)
thickness: 50 to 300 mm
Process of Rolling
These ingots are first heated to about 1200°C in soaking pits and
then passed through rollers to produce intermedials shapes
such as blooms. The blooms are rolled to billets and the billets
to the desired sections like flat, square, hexagonal, angle, I,U,
etc. The above mentioned member has following sizes
approximately.
Casted Ingots — 1.5 m x 1.5 m (Rectangular cross-section)
Blooms — 150 mm to 400 mm square.
Slabs— Width: 500 to 1800 mm (Rectangular cross-section)
thickness: 50 to 300 mm
91
Process of Rolling
Billets — 30 mm to 150 mm square. (Smaller than blooms)
Plates — 6 mm or over thickness, 1200-1400 mm width, 6000 mm
long.
Sheets— 0.5 mm to 5.0 mm thickness
Strip— Width: 750 mm or less. (Narrow plate or sheet).
Process of Rolling
Billets — 30 mm to 150 mm square. (Smaller than blooms)
Plates — 6 mm or over thickness, 1200-1400 mm width, 6000 mm
long.
Sheets— 0.5 mm to 5.0 mm thickness
Strip— Width: 750 mm or less. (Narrow plate or sheet).
92
Principles of Rolling
The maximum permissible value of angle of contact (α) depends
upon other factors like:
(i)Material of the rollers.
(ii) Material of work being rolled.
(iii) Temperature of rolling.
(iv) Speed of rollers, etc.
Principles of Rolling
The maximum permissible value of angle of contact (α) depends
upon other factors like:
(i)Material of the rollers.
(ii) Material of work being rolled.
(iii) Temperature of rolling.
(iv) Speed of rollers, etc.
93
Principles of Rolling
Table indicates the recommended maximum angle of bite (α) for
different rolling processes:
Principles of Rolling
Table indicates the recommended maximum angle of bite (α) for
different rolling processes:
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The Flat-rolling Process
•Flat-rolling process is shown
•Friction forces act on strip surfaces
•Roll force, F, and torque, T, acts on the rolls
Copyright © 2010 Pearson Education South Asia Pte Ltd
•Flat-rolling process is shown
•Friction forces act on strip surfaces
•Roll force, F, and torque, T, acts on the rolls
Copyright © 2010 Pearson Education South Asia Pte Ltd
The Flat-rolling Process
•As the surface speed of the rigid roll is constant, there
is relative sliding between the roll and the strip along
the arc of contact in the roll gap, L
•At neutral point or no-slip point, the velocity of the
strip is the same as that of the roll
•The maximum possible draft is defined as the
difference between the initial and final strip thicknesses
•From the relationship, higher the friction and the larger
the roll radius, the greater the maximum possible draft
becomes
Copyright © 2010 Pearson Education South Asia Pte Ltd
Rhh
fo
2
•As the surface speed of the rigid roll is constant, there
is relative sliding between the roll and the strip along
the arc of contact in the roll gap, L
•At neutral point or no-slip point, the velocity of the
strip is the same as that of the roll
•The maximum possible draft is defined as the
difference between the initial and final strip thicknesses
•From the relationship, higher the friction and the larger
the roll radius, the greater the maximum possible draft
becomes
Copyright © 2010 Pearson Education South Asia Pte Ltd
Rhh
fo
2
The Flat-rolling Process:
Roll Force, Torque, and Power Requirements
•Rolls apply pressure on the flat strip to reduce its
thickness, resulting in a roll force, F
•Roll force in flat rolling can be estimated from
•Total power (for two rolls) is
Copyright © 2010 Pearson Education South Asia Pte Ltd
avg
LwYF
L = roll-strip contact length
w = width of the strip
Y
avg = average true stress of the strip
000,33
2
hp)(in Power
000,60
2
kW)(in Power
FLN
FLN
Roll Force, Torque, and Power Requirements
•Rolls apply pressure on the flat strip to reduce its
thickness, resulting in a roll force, F
•Roll force in flat rolling can be estimated from
•Total power (for two rolls) is
Copyright © 2010 Pearson Education South Asia Pte Ltd
avg
LwYF
L = roll-strip contact length
w = width of the strip
Y
avg = average true stress of the strip
000,33
2
hp)(in Power
000,60
2
kW)(in Power
FLN
FLN
The Flat-rolling Process:
Roll Force, Torque, and Power Requirements
Reducing Roll Force
•Roll forces can cause deflection and flattening of the
rolls
•The columns of the roll stand may deflect under high
roll forces
•Roll forces can be reduced by:
1.Reducing friction at the roll–workpiece interface
2.Using smaller diameter rolls
3.Reduce the contact area
4.Rolling at elevated temperatures
5.Applying front and/or back tensions to the strip
Copyright © 2010 Pearson Education South Asia Pte Ltd
Roll Force, Torque, and Power Requirements
Reducing Roll Force
•Roll forces can cause deflection and flattening of the
rolls
•The columns of the roll stand may deflect under high
roll forces
•Roll forces can be reduced by:
1.Reducing friction at the roll–workpiece interface
2.Using smaller diameter rolls
3.Reduce the contact area
4.Rolling at elevated temperatures
5.Applying front and/or back tensions to the strip
Copyright © 2010 Pearson Education South Asia Pte Ltd
102
Defects in Rolling Process
Defects in Rolled Products:
Defects in rolling may be either surface or structural defects:
Some of the common defects in rolled products are given below:
(i)
Edge Cracking:
Edge cracking generally occurs in rolled ingots, slabs, or plates. This is
due to, either limited ductility of the work metal or uneven
deformation, especially at the edges.
(ii)
Zipper cracks:
•Small cracks that may appear in the middle of a work piece
•Caused by the bending of the sheet metal under high rolling pressure
Defects in Rolling Process
Defects in Rolled Products:
Defects in rolling may be either surface or structural defects:
Some of the common defects in rolled products are given below:
(i)
Edge Cracking:
Edge cracking generally occurs in rolled ingots, slabs, or plates. This is
due to, either limited ductility of the work metal or uneven
deformation, especially at the edges.
(ii)
Zipper cracks:
•Small cracks that may appear in the middle of a work piece
•Caused by the bending of the sheet metal under high rolling pressure
103
(iii)
Alligatoring:
Alligatoring is the defect, usually occurs in the rolling of slabs
(particularly aluminum and alloys). In this defect, the work piece splits
along a horizontal plane on exit, with the top and bottom. This defect
always occurs when the ratio of slab thickness to the length of contact
fall within the range of 1.4 to 1.65. Below Fig. shows the defect of
Alligatoring.
Defects in Rolling Process
(iii)
Alligatoring:
Alligatoring is the defect, usually occurs in the rolling of slabs
(particularly aluminum and alloys). In this defect, the work piece splits
along a horizontal plane on exit, with the top and bottom. This defect
always occurs when the ratio of slab thickness to the length of contact
fall within the range of 1.4 to 1.65. Below Fig. shows the defect of
Alligatoring.
Defects in Rolling Process
104
(iv)
Scale Formation:
When the metal is hot rolled, its surface is not smooth and it has
scale (oxide) formed over it.
Defects in Rolling Process
(iv)
Scale Formation:
When the metal is hot rolled, its surface is not smooth and it has
scale (oxide) formed over it.
Defects in Rolling Process
105
Extrusion of Metals
Extrusion of Metals
Extrusion is defined as the process of pushing the
heated billet or slug of metal through an orifice provided
into a die, thus forming an elongated part of uniform
cross-section corresponding to the shape of die orifice.
Extrusion of Metals
Extrusion of Metals
Extrusion is defined as the process of pushing the
heated billet or slug of metal through an orifice provided
into a die, thus forming an elongated part of uniform
cross-section corresponding to the shape of die orifice.
106
The extrusion process starts with the heating of the
billet. The billet are usually heated upto a temperature
such that the material becomes easily malleable and
ductile.
The billet is then loaded onto the container. When the
ram forces the metal to exit through the die opening ,
the metal is subjected to plastic deformation and it
undergoes reduction and elongation during extrusion.
The section of the product will depend upon the shape
of the die opening. This process could be considered an
adaptation of closed die forging, the difference being
that in a forging, the main body of the metal is the
product and the flash is cut away and discarded; in
extrusion, the flash ( metal flowing out of the die) is the
product and the slug remaining in the die is not used.
Extrusion process
The extrusion process starts with the heating of the
billet. The billet are usually heated upto a temperature
such that the material becomes easily malleable and
ductile.
The billet is then loaded onto the container. When the
ram forces the metal to exit through the die opening ,
the metal is subjected to plastic deformation and it
undergoes reduction and elongation during extrusion.
The section of the product will depend upon the shape
of the die opening. This process could be considered an
adaptation of closed die forging, the difference being
that in a forging, the main body of the metal is the
product and the flash is cut away and discarded; in
extrusion, the flash ( metal flowing out of the die) is the
product and the slug remaining in the die is not used.
Extrusion process
107
Extrusion of Metals
The pressure is applied either hydraulically or
mechanically.
Aluminium, nickel and their alloys are the metals
used for extrusion directly at the elevated
temperatures.
Aluminium and its alloys are greatly used for this
process. The extrusion of steel and its alloys is
also possible.
Extrusion of Metals
The pressure is applied either hydraulically or
mechanically.
Aluminium, nickel and their alloys are the metals
used for extrusion directly at the elevated
temperatures.
Aluminium and its alloys are greatly used for this
process. The extrusion of steel and its alloys is
also possible.
108
Extrusion of Metals
The extrusion dies made either from heat
resistant die steel or tungsten carbide, the latter
having much longer die life.
Rods, tubes, moulding trims, structural shapes,
cable sheathing, hose, casing, brass cartridge,
aircraft parts, gear profiles and hardware items
are the typical products of metal extrusion.
Intricate shapes in long lengths can be produced
by hot extrusions.
Extrusion of Metals
The extrusion dies made either from heat
resistant die steel or tungsten carbide, the latter
having much longer die life.
Rods, tubes, moulding trims, structural shapes,
cable sheathing, hose, casing, brass cartridge,
aircraft parts, gear profiles and hardware items
are the typical products of metal extrusion.
Intricate shapes in long lengths can be produced
by hot extrusions.
109
A complex extruded cross-section for a heat sink (photo courtesy
of Aluminum Company of America)
A complex extruded cross-section for a heat sink (photo courtesy
of Aluminum Company of America)
110
Extrusion of Metals
Below figure shows some of the typical shapes produced by hot
extrusion, which might be economically impracticable by any other
method.
The extrusion of such shapes requires dies of intricate design so that the
flow of metal is properly proportioned and fills out any deep recesses in
the profiles and does not flow preferentially through the larger cross-
sectioned openings.
Extrusion of Metals
Below figure shows some of the typical shapes produced by hot
extrusion, which might be economically impracticable by any other
method.
The extrusion of such shapes requires dies of intricate design so that the
flow of metal is properly proportioned and fills out any deep recesses in
the profiles and does not flow preferentially through the larger cross-
sectioned openings.
111
Extrusion of Metals
Types of Extrusion Process
Metal extrusion can be subdivided and grouped
into the following categories depending on the
direction of extrusion flow, the medium used to
apply force, working temperature, etc.
Extrusion of Metals
Types of Extrusion Process
Metal extrusion can be subdivided and grouped
into the following categories depending on the
direction of extrusion flow, the medium used to
apply force, working temperature, etc.
112
Extrusion of Metals
1.Direct Extrusion
2.Indirect Extrusion
3.Hydrostatic Extrusion
4. Hot extrusion
5. Cold Extrusion
6. Impact Extrusion
Extrusion of Metals
1.Direct Extrusion
2.Indirect Extrusion
3.Hydrostatic Extrusion
4. Hot extrusion
5. Cold Extrusion
6. Impact Extrusion
113
Extrusion of Metals
Direct Extrusion
Direct Extrusion,
sometimes called Forward Extrusion is the most
common type of extrusion. The process as shown in figure, begins by
loading a heated billet into a press cavity container where a dummy
block is placed behind it.
Then the mechanical or hydraulic ram presses on the material to
push it out through the die. Then, while still hot, the part is stretched
to straighten.
Extrusion of Metals
Direct Extrusion
Direct Extrusion,
sometimes called Forward Extrusion is the most
common type of extrusion. The process as shown in figure, begins by
loading a heated billet into a press cavity container where a dummy
block is placed behind it.
Then the mechanical or hydraulic ram presses on the material to
push it out through the die. Then, while still hot, the part is stretched
to straighten.
114
Extrusion of Metals
Direct Extrusion
Extrusion of Metals
Direct Extrusion
115
Extrusion of Metals
Under direct extrusion, the high friction caused by
steels at higher temperatures is reduced using molten
glass as a lubricant while oils with graphite powder are
used for lubrication for low temperatures.
The dummy block is used to protect the tip of the
pressing stem (punch or ram) in hot extrusion. When
the punch reaches the end of its stroke, a small portion
of the billet called “butt end” cannot be pushed through
the die opening.
Extrusion of Metals
Under direct extrusion, the high friction caused by
steels at higher temperatures is reduced using molten
glass as a lubricant while oils with graphite powder are
used for lubrication for low temperatures.
The dummy block is used to protect the tip of the
pressing stem (punch or ram) in hot extrusion. When
the punch reaches the end of its stroke, a small portion
of the billet called “butt end” cannot be pushed through
the die opening.
116
Extrusion of Metals
Advantages of Direct metal extrusion
1.No billet modification required
2.Can be used for both hot and cold extrusion
3.Simple tooling compared to other extrusion processes
Disadvantages of Direct metal extrusion
1.High force requirement due to friction
2.Butt end left inside the cavity
3.The force required to push the ram changes as the punch
moves.
Extrusion of Metals
Advantages of Direct metal extrusion
1.No billet modification required
2.Can be used for both hot and cold extrusion
3.Simple tooling compared to other extrusion processes
Disadvantages of Direct metal extrusion
1.High force requirement due to friction
2.Butt end left inside the cavity
3.The force required to push the ram changes as the punch
moves.
117
Extrusion of Metals
Indirect Extrusion
In
Indirect Extrusion,
the die is located at the end of the hydraulic
ram and moves towards the billet inside the cavity to push the
material through the die. This is illustrated in figure below.
This process consumes less power due to the static billet container
causing less friction on the billet. However, supporting the extruded
part is difficult when the
extrudate
exits the die
Extrusion of Metals
Indirect Extrusion
In
Indirect Extrusion,
the die is located at the end of the hydraulic
ram and moves towards the billet inside the cavity to push the
material through the die. This is illustrated in figure below.
This process consumes less power due to the static billet container
causing less friction on the billet. However, supporting the extruded
part is difficult when the
extrudate
exits the die
118
Indirect Extrusion
Indirect Extrusion
119
Indirect Extrusion
Advantages of In-direct metal extrusion
1.Less friction and less power used
2.Can be used for both hot and cold extrusion
3.Simple tooling compared to other extrusion
processes
Disadvantages of In-direct metal extrusion
1.Difficult to support the extruded part
2.The hollow ram limits the load applied
Indirect Extrusion
Advantages of In-direct metal extrusion
1.Less friction and less power used
2.Can be used for both hot and cold extrusion
3.Simple tooling compared to other extrusion
processes
Disadvantages of In-direct metal extrusion
1.Difficult to support the extruded part
2.The hollow ram limits the load applied
120
Hydrostatic Extrusion
Hydrostatic extrusion
In
hydrostatic extrusion,
the chamber/ cavity is made smaller
than the billet and filled with hydraulic fluid which transfers
the force from the ram to the billet as shown in figure.
Although tri-axial forces are applied by the fluid, the pressure
improves billet formability on the billet. Sealing the fluid must
be considered at the early stages to avoid any leaking and
reduced pressure issues.
Hydrostatic Extrusion
Hydrostatic extrusion
In
hydrostatic extrusion,
the chamber/ cavity is made smaller
than the billet and filled with hydraulic fluid which transfers
the force from the ram to the billet as shown in figure.
Although tri-axial forces are applied by the fluid, the pressure
improves billet formability on the billet. Sealing the fluid must
be considered at the early stages to avoid any leaking and
reduced pressure issues.
121
Hydrostatic Extrusion
Hydrostatic Extrusion
122
Hydrostatic Extrusion
Although the hydraulic fluid eliminates the friction
between the wall and the billet by isolating them, due
to the specialized equipment requirement, the high
set up time and low production rate limit its usage in
the industry in comparison to other extrusion
processes.
Hydrostatic Extrusion
Although the hydraulic fluid eliminates the friction
between the wall and the billet by isolating them, due
to the specialized equipment requirement, the high
set up time and low production rate limit its usage in
the industry in comparison to other extrusion
processes.
123
Hydrostatic Extrusion
Advantages of Hydrostatic metal extrusion
1.Low power/force requirement due to no friction
2.Fast production rates & high reduction ratios
3.Lower billet temperature
4.Even flow of material due to the balanced force
distribution
5.Large billets and large cross-sections can be extruded
6.No billet residue is left in the container
Disadvantages of Hydrostatic metal extrusion
1.Billets need preparing by tapering one end to match
the die entry angle
2.Only cold extrusion is possible
3.Difficult to contain the high-pressure fluid
Hydrostatic Extrusion
Advantages of Hydrostatic metal extrusion
1.Low power/force requirement due to no friction
2.Fast production rates & high reduction ratios
3.Lower billet temperature
4.Even flow of material due to the balanced force
distribution
5.Large billets and large cross-sections can be extruded
6.No billet residue is left in the container
Disadvantages of Hydrostatic metal extrusion
1.Billets need preparing by tapering one end to match
the die entry angle
2.Only cold extrusion is possible
3.Difficult to contain the high-pressure fluid
124
Hot Extrusion
It is done at fairly high temperatures, approximately 50 to
75% of the melting point of the metal.
Die life and components are effected due to the high
temperatures and pressures, which makes lubrication
necessary.
Pressures Ranges: 35-700 Mpa.
Hot Extrusion
It is done at fairly high temperatures, approximately 50 to
75% of the melting point of the metal.
Die life and components are effected due to the high
temperatures and pressures, which makes lubrication
necessary.
Pressures Ranges: 35-700 Mpa.
125
Hot Extrusion
ADVANTAGES OF HOT
EXTRUSIONComplex solid or hollow shapes can be produced.
Small quantities can be economically produced.
Delivery times are often far shorter than alternative
processes.
Hot Extrusion
ADVANTAGES OF HOT
EXTRUSIONComplex solid or hollow shapes can be produced.
Small quantities can be economically produced.
Delivery times are often far shorter than alternative
processes.
126
Hot Extrusion
LIMITATIONS OF HOT
EXTRUSIONHigh equipment set up and maintenance cost.
Extrusion process for metals is at very high temperatures.
Die is preheated to increase its life, so there are chances of
oxidation of hot billet.
Process Wastage is higher as compared to rolling.
Non-homogeneous.
Hot Extrusion
LIMITATIONS OF HOT
EXTRUSIONHigh equipment set up and maintenance cost.
Extrusion process for metals is at very high temperatures.
Die is preheated to increase its life, so there are chances of
oxidation of hot billet.
Process Wastage is higher as compared to rolling.
Non-homogeneous.
127
Cold Extrusion
Coldextrusionistheprocessdoneatroomtemperature
or slightly elevated temperatures.
This process can be used for materials that can withstand the
stresses created by extrusion.
Cold Extrusion
Coldextrusionistheprocessdoneatroomtemperature
or slightly elevated temperatures.
This process can be used for materials that can withstand the
stresses created by extrusion.
128
Cold Extrusion
DISADVANTAGES OF COLD
EXTRUSION
⚫Toolingcostishigh,thereforelargeproductionlotsizeis
required
⚫Special coating is required to reduce friction and to maintain
a lubricant film throughout.
⚫Limited deformation can be obtained.
Cold Extrusion
DISADVANTAGES OF COLD
EXTRUSION
⚫Toolingcostishigh,thereforelargeproductionlotsizeis
required
⚫Special coating is required to reduce friction and to maintain
a lubricant film throughout.
⚫Limited deformation can be obtained.
129
Cold Extrusion
APPLICATIONS OF COLD
EXTRUSION
⚫Cu, Pb, Sn, Al Alloys, Ti, Mo, V, Steel, Zr parts can be extruded.
⚫Tubes, Gear Blanks, Aluminum Cans, Cylinders, Fire
Extinguisher Cases, Shock Absorber Cylinders, and Automotive
Pistons are manufactured.
Cold Extrusion
APPLICATIONS OF COLD
EXTRUSION
⚫Cu, Pb, Sn, Al Alloys, Ti, Mo, V, Steel, Zr parts can be extruded.
⚫Tubes, Gear Blanks, Aluminum Cans, Cylinders, Fire
Extinguisher Cases, Shock Absorber Cylinders, and Automotive
Pistons are manufactured.
130
Impact Extrusion
Impact Extrusion
Impact extrusion is part of cold extrusion category very
similar to In-direct extrusion and limited to softer metal
such as Lead, Aluminium and copper. As the schematic
illustrates, the punch pushed down at high speed and
extreme force on the slug to extrudes backwards.
The thickness of the Extrude is a function of the
clearance between the punch and the die cavity.
The
Extrudates
are slide off the punch by the use of
stripper plate.
Impact Extrusion
Impact Extrusion
Impact extrusion is part of cold extrusion category very
similar to In-direct extrusion and limited to softer metal
such as Lead, Aluminium and copper. As the schematic
illustrates, the punch pushed down at high speed and
extreme force on the slug to extrudes backwards.
The thickness of the Extrude is a function of the
clearance between the punch and the die cavity.
The
Extrudates
are slide off the punch by the use of
stripper plate.
131
Impact Extrusion
Impact Extrusion
132
Impact Extrusion
For impact extrusions, a mechanical press is often
used and the part is formed at a high speed and over
a relatively short stroke.
Since the forces acting on the punch and die are
extremely high, tooling must have sufficient impact
resistance, fatigue resistance and strength, for
extruding metal by the impact. Impact extrusion can
be divided into the following three types by the flow
of the material.
1.Forward
2.Reverse
3.Combination
Impact Extrusion
For impact extrusions, a mechanical press is often
used and the part is formed at a high speed and over
a relatively short stroke.
Since the forces acting on the punch and die are
extremely high, tooling must have sufficient impact
resistance, fatigue resistance and strength, for
extruding metal by the impact. Impact extrusion can
be divided into the following three types by the flow
of the material.
1.Forward
2.Reverse
3.Combination
133
Impact Extrusion
In
forward impact extrusion, the metal flows in the same direction
that the force is delivered while it flows in the opposite direction
in
reverse
impact extrusion
. As the image shows above,
in
combination, the metal flows in both directions.
Impact Extrusion
In
forward impact extrusion, the metal flows in the same direction
that the force is delivered while it flows in the opposite direction
in
reverse
impact extrusion
. As the image shows above,
in
combination, the metal flows in both directions.
134
Impact Extrusion
Advantages of impact metal extrusion
1.Raw material savings of up to 90%
2.Reduced machining times up to 75%
3.Elimination of secondary machining operations
4.Reduction in multi-part assemblies
5.Improved mechanical properties for material strength
and machining due to cold working of the material
6.Significantly reduced total part costs up to 50%
7.Hollow thin walled tubes, closed on one end, are often
produced in manufacturing industry by backward impact
extrusion.
Impact Extrusion
Advantages of impact metal extrusion
1.Raw material savings of up to 90%
2.Reduced machining times up to 75%
3.Elimination of secondary machining operations
4.Reduction in multi-part assemblies
5.Improved mechanical properties for material strength
and machining due to cold working of the material
6.Significantly reduced total part costs up to 50%
7.Hollow thin walled tubes, closed on one end, are often
produced in manufacturing industry by backward impact
extrusion.
135
Impact Extrusion
Disadvantages of impact metal extrusion
1.Produced as long as the part is symmetrical over the
axis by which it is formed
2.Many of the parts formed by impacting, in industry, will
require further manufacturing processes, such as metal
forging, ironing or machining, before completion
Impact Extrusion
Disadvantages of impact metal extrusion
1.Produced as long as the part is symmetrical over the
axis by which it is formed
2.Many of the parts formed by impacting, in industry, will
require further manufacturing processes, such as metal
forging, ironing or machining, before completion
136
Impact Extrusion
Extrusion Defects
Depending on material condition and process
variables, extruders can develop many types of
defects that could affect the quality of the end
product.
These defects can be grouped under the
following three defects.
1.Surface cracking
2.Piping
3.Internal cracking
Impact Extrusion
Extrusion Defects
Depending on material condition and process
variables, extruders can develop many types of
defects that could affect the quality of the end
product.
These defects can be grouped under the
following three defects.
1.Surface cracking
2.Piping
3.Internal cracking
Defects during
extrusion
Centerburst:
-This is an internal crack that develops as a result of
tensile stresses along the center axis of the workpiece
during extrusion. A large material motion at the outer
regions pulls the material along the center of the work.
Beyond a critical limit, bursting occurs.
-.
Piping: It is the formation of a sink hole in the end of
the billet..
Centerburst
Piping
Surface cracking: This defect results from high workpiece temperatures that
cause cracks to develop at the surface. They also occur at higher extrusion
speeds, leading to high strain rates and heat generation. Higher friction at
the surface and surface chilling of high temperature billets in hot extrusion
also cause this defect.
Surface cracking
extrusion
Centerburst:
-This is an internal crack that develops as a result of
tensile stresses along the center axis of the workpiece
during extrusion. A large material motion at the outer
regions pulls the material along the center of the work.
Beyond a critical limit, bursting occurs.
-.
Piping: It is the formation of a sink hole in the end of
the billet..
Centerburst
Piping
Surface cracking: This defect results from high workpiece temperatures that
cause cracks to develop at the surface. They also occur at higher extrusion
speeds, leading to high strain rates and heat generation. Higher friction at
the surface and surface chilling of high temperature billets in hot extrusion
also cause this defect.
Surface cracking
Extrusion
Typical use: ductile metals (Cu, Steel, Al, Mg),
Plastics, Rubbers
Common products:
Al frames of white-boards, doors, windows, …
Extrusion
Typical use: ductile metals (Cu, Steel, Al, Mg),
Plastics, Rubbers
Common products:
Al frames of white-boards, doors, windows, …
Extrusion
Wire Drawing
Drawing is an operation in which the cross-section ofa
bar, rod or wire is reduced by pulling it through a die
opening.
The general features of the drawing process are similar to
extrusion. But the difference is that, in drawing the work
piece is pulled through the die whereas in extrusion work
piece is pushed through the die.
During the process, tensile as well as compressive
stresses are produced in the material.
The main difference between the bar drawing and wire
drawing is the stock size(work piece size). Bar drawing is
used for large diameter (bar and rod) stock whereas wire
drawing is used for small diameter stock
Drawing is an operation in which the cross-section ofa
bar, rod or wire is reduced by pulling it through a die
opening.
The general features of the drawing process are similar to
extrusion. But the difference is that, in drawing the work
piece is pulled through the die whereas in extrusion work
piece is pushed through the die.
During the process, tensile as well as compressive
stresses are produced in the material.
The main difference between the bar drawing and wire
drawing is the stock size(work piece size). Bar drawing is
used for large diameter (bar and rod) stock whereas wire
drawing is used for small diameter stock
Wire sizes upto 0.03 mm can be drawn by wire drawing
process.
The process consists ofpulling the hot drawn bar or rod
through a die of which the bore size is similar to the finished
product size. Depending upon the material to be drawn and
the amount ofreduction required, total drawing can be
accomplished in a single die or in a series ofsuccessive dies.
process.
The process consists ofpulling the hot drawn bar or rod
through a die of which the bore size is similar to the finished
product size. Depending upon the material to be drawn and
the amount ofreduction required, total drawing can be
accomplished in a single die or in a series ofsuccessive dies.
WIRE DRAWING:
By successive drawing operation through dies of
reducing diameter the wire can be reduced to a very
small diameter.
Tungsten Carbide dies are used to for drawing hard
wires, and diamond dies is the choice for fine wires.
142
By successive drawing operation through dies of
reducing diameter the wire can be reduced to a very
small diameter.
Tungsten Carbide dies are used to for drawing hard
wires, and diamond dies is the choice for fine wires.
142
DRAWING PRODUCTS:
•Electrical wire
•Cable
•Springs
•Welding Electrodes
•Metal bars
•Paper Clips
•Rods for shafts
ADVANTAGES:
-Close dimensional control
-Good surface finish
-Improved strength and hardness
-Adaptability to mass production
143
•Electrical wire
•Cable
•Springs
•Welding Electrodes
•Metal bars
•Paper Clips
•Rods for shafts
ADVANTAGES:
-Close dimensional control
-Good surface finish
-Improved strength and hardness
-Adaptability to mass production
143
Tube
drawingThis operation is used to reduce the diameter or wall thickness of the seamless
tubes and pipes. Tube drawing can be done either with or without mandrel.
The simplest method uses no mandrel and is used for diameter reduction
called as tube sinking. But inside diameter and wall thickness cannot be
controlled. So mandrel is required.
Die
Die
Mandre
l
Rod
Tube
Di
e
Tub
e
Pull
force
Di
e
Tub
e
Pull
force
Floating
mandrel
(a) Rod
drawing
(c) Tube drawing with fixed
mandrel
(b) Tube drawing without
mandrel
(TUBE SINKING)
(d) Tube drawing with floating
mandrel
drawingThis operation is used to reduce the diameter or wall thickness of the seamless
tubes and pipes. Tube drawing can be done either with or without mandrel.
The simplest method uses no mandrel and is used for diameter reduction
called as tube sinking. But inside diameter and wall thickness cannot be
controlled. So mandrel is required.
Die
Die
Mandre
l
Rod
Tube
Di
e
Tub
e
Pull
force
Di
e
Tub
e
Pull
force
Floating
mandrel
(a) Rod
drawing
(c) Tube drawing with fixed
mandrel
(b) Tube drawing without
mandrel
(TUBE SINKING)
(d) Tube drawing with floating
mandrel
Using a fixed mandrel: In this case, a mandrel is attached to a long
support
bar to control the inside diameter and wall thickness during the
operation. The length of the support bar restricts the length of the
tube that can be drawn.
Using a floating plug: As the name suggests the mandrel floats inside
the tube and its shape is designed so that it finds a suitable position
in the reduction zone of the die. There is no length restriction in this
as seen with the fixed mandrel.
support
bar to control the inside diameter and wall thickness during the
operation. The length of the support bar restricts the length of the
tube that can be drawn.
Using a floating plug: As the name suggests the mandrel floats inside
the tube and its shape is designed so that it finds a suitable position
in the reduction zone of the die. There is no length restriction in this
as seen with the fixed mandrel.
Tube drawing
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