MANUFACTURING PROCESS sand is packed tight, the pattern can be removed, and to the decrease in volume that accompanies the transformation metal components such as turbine engine fan blades, and it is used
the cast will remain. Alternatively, a two-piece, non- from liquid to solid. When a molten material solidifies, it contracts in toughened glass to allow for large, thin, crack- and scratch-
Module:1 destructible metal Mold can be created so that the because the solid phase typically has a higher density than the resistant glass displays on smartphones. However, unintended
Mold can be used repeatedly to cast identical parts for liquid phase. The amount of shrinkage depends on various factors residual stress in a designed structure may cause it
❖ Casting industrial applications. including the material type, its composition, cooling rate, and the to fail prematurely.
shape and size of the casting or mold. Managing shrinkage is
Casting involves pouring liquid metal or plastic into a mould and 4. Melting and Pouring Molten Metal – After metal is essential to avoid defects such as cracks, voids, or dimensional Residual stresses can result from a variety of mechanisms
allowing it to cool and solidify into the desired shape. The mould is melted, it is poured into the cavity of the Mold and left inaccuracies in the final product. including inelastic (plastic) deformations, temperature gradients
typically made from a refractory material such as sand or ceramic to solidify. Once solidified, the shakeout process (during thermal cycle) or structural changes (phase
and is designed to withstand the high temperature of the liquid begins: the Molds undergo vibration to remove sand ❖ Riser Design transformation). Heat from welding may cause localized
material. Once the material has cooled and solidified, the mould is from the casting. In industrial applications, expansion, which is taken up during welding by either the molten
removed to reveal the final product. equipment like our Two-Mass Shakeouts keeps metal or the placement of parts being welded. When the finished
production output high because of its efficient and A riser is a reservoir of molten metal that is connected to the weldment cools, some areas cool and contract more than others,
smooth performance. Removed sand is typically casting during the solidification process. Risers are used to leaving residual stresses.
There are several casting processes, including sand casting and die
casting. Sand casting, for example, is a relatively inexpensive collected, cooled, and reclaimed to be used once more compensate for shrinkage that occurs at the molten metal cools
in future castings. The VIBRA-DRUM® Sand Casting and solidifies. This helps to prevent shrinkage defects, such as
process well-suited to manufacturing large, complex parts. Die
Conditioner improves this process of sand separation porosity and voids, in the casting Riser design is a critical aspect in
casting, however, is a high-pressure process ideal for producing
small, precise parts with tight tolerances. Casting is used to from castings by removing and cooling sand and the casting process, aimed at ensuring quality and minimizing
castings and evaporating moisture, while alleviating defects in metal castings. A riser, also known as a feeder or a feed
produce large and complex parts and is ideal for low-volume
the casting damage that is common during this point head, is a reservoir of molten metal strategically placed in a mold
production.
of the process. The end results are a clean cast and to compensate for solidification shrinkage during casting.The
sand ready for the reclamation process. primary purpose of risers is to supply additional molten metal to
❖ moulding
the casting as it solidifies, thereby feeding the shrinkage that
5. Cleaning – In this final step, the cast metal object is occurs as the metal cools and solidifies. Without adequate risers,
Moulding is a manufacturing process that involves shaping a liquid shrinkage can lead to defects such as shrinkage cavities, porosity,
removed from the Mold and then fettled. During the
or malleable raw material by using a fixed frame; known as either and internal voids in the casting.
fettling, the object is cleaned of any moulding
a Mold or a matrix. The Mold is generally a hollow cavity
material, and rough edges are removed.
receptacle, commonly made of metal, where liquid plastic, metal,
ceramic, or glass material is poured. In most cases, the Mold is TYPES OF CASTING DEFECTS
derived from the initial pattern or template of the final object; its ❖ Heat transfer
main objective is to reproduce multiple uniform copies of the final
product. As the liquid cools and hardens inside the Mold, the final Heat transfer is the energy exchanged between materials
It is an unwanted irregularity that appear in the casting during
configuration is achieved. Its removal is facilitated by the use of a (solid/liquid/gas) as a result of a temperature difference.
metal casting process. There is various reason or sources which is
release agent or ejection pins. The thermodynamic free energy is the amount of work that a
responsible for the defects in the cast metal. Here in this blog, we
thermodynamic system can perform. Enthalpy is a thermodynamic
will discuss all the major types of casting defects. Some of the
❖ What is Metal Casting? potential, designated by the letter "H", that is the sum of
defects produced may be neglected or tolerated and some are not
the internal energy of the system (U) plus the product
acceptable, it must be eliminated for better functioning of the
of pressure (P) and volume (V). Joule is a unit to quantify energy,
Metal casting is a modern process with ancient roots. In the metal parts.
work, or the amount of heat.
casting process, metal shapes are formed by pouring molten metal
into a Mold cavity, where it is cooled and later extracted from the Types
Mold. Metal casting is arguably the earliest and most influential Heat transfer is a process function (or path function), as opposed
industrial process in history. It’s used to make many of the metal to functions of state; therefore, the amount of heat transferred in
a thermodynamic process that changes the state of 1. Gas Porosity: Blowholes, open holes, pinholes
objects used in our daily lives: automotive parts, train wheels, 2. Shrinkage defects: shrinkage cavity
lamp posts, school bus pedals, and much more. Plus, metal casting a system depends on how that process occurs, not only the net
difference between the initial and final states of the process. 3. Mold material defects: Cut and washes, swell, drops, metal
foundries rely on metal recycling as a cost-efficient source of raw penetration, rat tail
material, significantly reducing wasted scrap metal that might end 4. Pouring metal defects: Cold shut, misrun, slag inclusion
up in landfills. Thermodynamic and mechanical heat transfer is calculated with
5. Metallurgical defects: Hot tears, hot spot.
the heat transfer coefficient, the proportionality between the heat
The Metal Casting Process flux and the thermodynamic driving force for the flow of heat. Heat
flux is a quantitative, vectorial representation of heat-flow through
a surface.
1. Patternmaking – A pattern is a replica of the exterior
of the casting. Patterns are typically made of wood,
metal, plastic, or plaster. Patternmaking is incredibly ❖ Solidification
important for industrial part-making, where precise
calculations are needed to make pieces fit and work Solidification is the transformation of liquid to solid, such as the
together. formation of ice, the freezing of solder in electrical circuits, and the
casting of metals in industrial practice. Casting of metals is one of
2. Core making – If a casting is hollow, an additional most economic and important manufacture routes. Solidification
piece of sand or metal (called a core) shapes the refers to the transformation of a material from a liquid state to a
internal form to make it hollow. Cores are typically solid state. This process is fundamental in casting and
metalworking industries where molten metals are poured into
strong yet collapsible so they can be easily removed
molds to create various components and products. During
from the finished casting.
solidification, as the temperature of the molten metal decreases,
its atoms or molecules arrange themselves into a solid crystalline
3. Moulding – To visualize the metal casting process so
structure. This transition is crucial as it determines the final
far, imagine yourself walking on the beach toward the
properties of the material, such as its mechanical strength,
ocean. Look at a footprint you leave behind in the wet
hardness, and microstructure.
sand. Your foot would be the core, and the impression
left in the sand is a Mold of your foot. Moulding is a ❖ Residual stress
multistep process that will form a cast around the ❖ Shrinkage
pattern using moulding sand. In casting, a Mold is residual stresses are stresses that remain in a solid material after
contained in a frame called a flask. Green sand, or Shrinkage is part of the production process in any company and the original cause of the stresses has been removed. Residual
moulding sand, is packed into the flask around the refers to the amount of material or product that is lost or gained stress may be desirable or undesirable. For example, laser
pattern. This is known as metal sand casting. Once the during this process due to quality problems and waste or errors in peening imparts deep beneficial compressive residual stresses into
standards. Shrinkage occurs during the solidification process due
, Module: 2 ❖ yield criterion ❖ Rolling Key aspects of backward extrusion include:
❖ Bulk Metal Forming yield criterion states that yielding of a ductile material begins rolling is a metal forming process in which metal stock is passed - The metal material flows backward around the punch and into
when the second invariant of deviatoric stress reaches a critical through one or more pairs of rolls to reduce the thickness, to make the die cavity.
In bulk metal forming processes, including forging, the metal is value.[2] It is a part of plasticity theory that mostly applies to the thickness uniform, and/or to impart a desired mechanical
exposed to a significant amount of plastic deformation before ductile materials, such as some metals. Prior to yield, material property. The concept is similar to the rolling of dough. Rolling is - This process is suitable for creating parts with intricate shapes
obtaining the final geometry. In near-net-shape processes, the response can be assumed to be of a linear elastic, nonlinear elastic, classified according to the temperature of the metal rolled. If the and details.
material flow is even more complicated, which makes the or viscoelastic behaviour. yield criterion is also formulated in temperature of the metal is above
deformation analysis challenging. Such complexity is related to the terms of the von Mises stress or equivalent tensile stress, . This is a its recrystallization temperature, then the process is known as hot - It is often used in forming processes requiring high precision and
nonlinearity of the final geometry, material and boundary scalar value of stress that can be computed from the Cauchy stress rolling. If the temperature of the metal is below its minimal material waste.
conditions in the forming process. Thus, to analyse the material tensor. In this case, a material is said to start yielding when the von recrystallization temperature, the process is known as cold rolling.
behaviour during forming processes, the main objectives are: Mises stress reaches a value known as yield strength, . The von In terms of usage, hot rolling processes more tonnage than any Backward extrusion is commonly employed in industries such as
Mises stress is used to predict yielding of materials under complex other manufacturing process, and cold rolling processes the most automotive manufacturing for producing parts like gear blanks,
(1) To establish the kinematic relationships between the loading from the results of uniaxial tensile tests. The von Mises tonnage out of all cold working processes. Roll stands holding bushings, and other components that require intricate geometries
undeformed and deformed parts. Most prominently, to predict the stress satisfies the property where two stress states with pairs of rolls are grouped together into rolling mills that can and precise tolerances. The choice between forward and backward
metal flow during the forming process (Geometry). equal distortion energy have an equal von Mises stress. quickly process metal, typically steel, into products such extrusion depends on factors such as part complexity, material
as structural steel (I-beams, angle stock, channel stock), bar stock, properties, and production volume.
(2) To establish the forming limits, i.e., to determine the possibility ❖ Fundamentals of Hot and Cold Working Processes and rails. Most steel mills have rolling mill divisions that convert
of performing the forming operation without causing any surface the semi-finished casting products into finished products.
❖ Drawing
or internal cracks or folds (Material). “Hot working and cold working” are to be done for the process of
“metal formation”. Through the “mechanical deformation process” ❖ Extrusion
Drawing is a similar process, using the tensile strength of the
(3) To estimate the load that is required to carry out such a “metal formation” of objects and parts is to take place. “Hot material to pull it through the die. It limits the amount of change
forming operation, which provides necessary information for tool working” has to be carried out in general at the temperature above Extrusion is a process used to create objects of a fixed cross- that can be performed in one step, so it is limited to simpler
design and equipment selection (Boundary condition). “recrystallization temperature”. But carried out below the “Melting sectional profile by pushing material through a die of the desired shapes, and multiple stages are usually needed. Drawing is the
point” of metal. Whereas “cold working process” has to be carried cross-section. Its two main advantages over other manufacturing main way to produce wire. Metal bars and tubes are also often
out below the “recrystallization temperature”. processes are its ability to create very complex cross-sections; and
❖ Sheet metal drawn.
to work materials that are brittle, because the material encounters
“Cold working” only compressive and shear stresses. It also creates excellent
Sheet metal forming is quite common for making shaped ❖ Deep drawing
surface finish and gives considerable freedom of form in the design
components, from soda cans to automotive car bodies. It is
“Cold working” is a process executed for the “metal formation process.
customary to refer to a material below the thickness of 6.35 mm as Deep drawing is a sheet metal forming process used industrially to
a sheet and thicker materials as plate. Because this book is limited process”. According to its name, this metal formation has to be produce cup-shaped, box-shaped, and other complex-curved
to bend forming, which is the simplest of sheet metal forming executed below “recrystallization temperature”. At room **Forward Extrusion Process:**
hollow-shaped sheet parts. Micro-cups/micro-boxes may be
operations, the basic discussion is limited to bending. It is easy to temperature hot working is to be done. In this case, expected produced with similar process configurations for micro-housing
visualize the extension of friction stir processing for enhanced recovery of metal cannot be gained. This process contrasts with the applications, such as for the packaging of micro-sensors and
formability to three-dimensional forming involving various stress “hot working” process as it disfigures the gained structure and is micro-actuators. As for conventional deep drawing, the major
states. A key aspect that is going to be emphasized is the plate unable to provide satisfaction in decreasing size. Unlike “hot Forward extrusion is a metal forming process where a billet or parameters which influence the process and product quality
forming. As will become clear, higher the thickness of material, working”, in “cold working process”, much more pressure needs to workpiece is forced through a die to create a desired shape. The include the dimensions of the blank, the punch and die
lower the formability. be applied. If metal is more ductile or flexible, then the process has process begins with a cylindrical billet being placed in a container, dimensions, especially the punch corner radii, the clearance
to be done through a “cold working process”. “Cold working known as a "can," with a die at one end. A ram or punch applies between the punch and the die, as well as the blank-holder
❖ Plastic Deformation: processes” cause “strain hardening”, “grain deformation”, and force to the billet, pushing it through the die cavity. The metal flows geometry, the interfacial conditions, and the holding pressures.
“crystal structure”. “Cold working process” is to be done for around the punch and through the die, taking the shape of the die Deep drawing is a more complex process than shearing/cutting
reducing flexibility of metal. cavity as it emerges on the other side. and bending because it usually combines processes such as
Plastic deformation is defined as a process in which the object due
to applied force changes its size or shape in a way that is not bending, unbending, stretching, compression, and shearing,
reversible. Plastic deformation is seen in many objects, including: “Hot working” During forward extrusion: depending on the part geometry to be produced. These processes
become more complex when the micro-structure of the sheet metal
“Hot working” is performed above the temperature of - The metal undergoes plastic deformation due to compressive becomes a dominant factor as the scale decreases
• Plastics “recrystallization”. Yet this process is said to be accomplished stress applied by the punch.
above “melting point” for recovery and deformation both can be
achieved at the same time. After applying heat to the “metal-plastic
• Metals deformation “the structure of the metal changes at the end. During
- Friction between the billet and the die walls helps in controlling
metal flow and achieving the desired shape.
this development, no residual stress takes place. Due to increased
• Soils
deformation takes place in this process the temperature used; the
stress needed for deformation is less. In this case, very less force is
- The final part typically has a length greater than the original
billet due to the material displacement.
required to be applied to metal. Then the metal gets plastically
• Rocks deformed. Due to “hot working process: metal grains are refined
which results in properties of metal
Forward extrusion is used to produce parts with a variety of
shapes, such as shafts, cylinders, and cups. It is suitable for both
• Concrete ❖ Forging
hot and cold forming, depending on the material and desired
properties of the final product.
The mechanisms that cause plastic deformation differ widely. Forging is the manufacturing process of hammering, pressing or
❖ Shearing
Plasticity in metals is a consequence of dislocations while in brittle rolling metal into shape. This is either delivered from a hammer,
materials such as concrete, rock and bone, plasticity occurs due to press or die. It is essentially the art of heating and working hot
the slippage of microcracks. There are two prominent mechanisms ❖ **Backward Extrusion Process:** Shearing, also known as die cutting, is a process that cuts stock
metal to design or shape that is fit for a specific purpose or use. By
of plastic deformation in metals, and they are without the formation of chips or the use of burning or melting.
working the material, it increases many of its properties, including
Strictly speaking, if the cutting blades are straight the process is
structure, conductivity and longevity. Forging offers a very useful
called shearing; if the cutting blades are curved then they are
and diverse medium for many industries with the process being
• Slip economically sound and achieving specific mechanical properties. Backward extrusion, also known as backward impact extrusion, shearing-type operations. The most commonly sheared materials
Forging is often categorized according to the temperature at which reverses the flow direction compared to forward extrusion. In this are in the form of sheet metal or plates. However, rods can also be
sheared. Shearing-type operations include blanking, piercing, roll
• Twinning it is performed, cold, warm, or hot forging. process, the die is located at the end of the ram or punch, and the
punch moves towards the stationary billet or workpiece. As the slitting, and trimming. It is used for metal, fabric, paper and
punch contacts the billet, it forces the metal material radially plastics.
outward against the die walls.
the cast will remain. Alternatively, a two-piece, non- from liquid to solid. When a molten material solidifies, it contracts in toughened glass to allow for large, thin, crack- and scratch-
Module:1 destructible metal Mold can be created so that the because the solid phase typically has a higher density than the resistant glass displays on smartphones. However, unintended
Mold can be used repeatedly to cast identical parts for liquid phase. The amount of shrinkage depends on various factors residual stress in a designed structure may cause it
❖ Casting industrial applications. including the material type, its composition, cooling rate, and the to fail prematurely.
shape and size of the casting or mold. Managing shrinkage is
Casting involves pouring liquid metal or plastic into a mould and 4. Melting and Pouring Molten Metal – After metal is essential to avoid defects such as cracks, voids, or dimensional Residual stresses can result from a variety of mechanisms
allowing it to cool and solidify into the desired shape. The mould is melted, it is poured into the cavity of the Mold and left inaccuracies in the final product. including inelastic (plastic) deformations, temperature gradients
typically made from a refractory material such as sand or ceramic to solidify. Once solidified, the shakeout process (during thermal cycle) or structural changes (phase
and is designed to withstand the high temperature of the liquid begins: the Molds undergo vibration to remove sand ❖ Riser Design transformation). Heat from welding may cause localized
material. Once the material has cooled and solidified, the mould is from the casting. In industrial applications, expansion, which is taken up during welding by either the molten
removed to reveal the final product. equipment like our Two-Mass Shakeouts keeps metal or the placement of parts being welded. When the finished
production output high because of its efficient and A riser is a reservoir of molten metal that is connected to the weldment cools, some areas cool and contract more than others,
smooth performance. Removed sand is typically casting during the solidification process. Risers are used to leaving residual stresses.
There are several casting processes, including sand casting and die
casting. Sand casting, for example, is a relatively inexpensive collected, cooled, and reclaimed to be used once more compensate for shrinkage that occurs at the molten metal cools
in future castings. The VIBRA-DRUM® Sand Casting and solidifies. This helps to prevent shrinkage defects, such as
process well-suited to manufacturing large, complex parts. Die
Conditioner improves this process of sand separation porosity and voids, in the casting Riser design is a critical aspect in
casting, however, is a high-pressure process ideal for producing
small, precise parts with tight tolerances. Casting is used to from castings by removing and cooling sand and the casting process, aimed at ensuring quality and minimizing
castings and evaporating moisture, while alleviating defects in metal castings. A riser, also known as a feeder or a feed
produce large and complex parts and is ideal for low-volume
the casting damage that is common during this point head, is a reservoir of molten metal strategically placed in a mold
production.
of the process. The end results are a clean cast and to compensate for solidification shrinkage during casting.The
sand ready for the reclamation process. primary purpose of risers is to supply additional molten metal to
❖ moulding
the casting as it solidifies, thereby feeding the shrinkage that
5. Cleaning – In this final step, the cast metal object is occurs as the metal cools and solidifies. Without adequate risers,
Moulding is a manufacturing process that involves shaping a liquid shrinkage can lead to defects such as shrinkage cavities, porosity,
removed from the Mold and then fettled. During the
or malleable raw material by using a fixed frame; known as either and internal voids in the casting.
fettling, the object is cleaned of any moulding
a Mold or a matrix. The Mold is generally a hollow cavity
material, and rough edges are removed.
receptacle, commonly made of metal, where liquid plastic, metal,
ceramic, or glass material is poured. In most cases, the Mold is TYPES OF CASTING DEFECTS
derived from the initial pattern or template of the final object; its ❖ Heat transfer
main objective is to reproduce multiple uniform copies of the final
product. As the liquid cools and hardens inside the Mold, the final Heat transfer is the energy exchanged between materials
It is an unwanted irregularity that appear in the casting during
configuration is achieved. Its removal is facilitated by the use of a (solid/liquid/gas) as a result of a temperature difference.
metal casting process. There is various reason or sources which is
release agent or ejection pins. The thermodynamic free energy is the amount of work that a
responsible for the defects in the cast metal. Here in this blog, we
thermodynamic system can perform. Enthalpy is a thermodynamic
will discuss all the major types of casting defects. Some of the
❖ What is Metal Casting? potential, designated by the letter "H", that is the sum of
defects produced may be neglected or tolerated and some are not
the internal energy of the system (U) plus the product
acceptable, it must be eliminated for better functioning of the
of pressure (P) and volume (V). Joule is a unit to quantify energy,
Metal casting is a modern process with ancient roots. In the metal parts.
work, or the amount of heat.
casting process, metal shapes are formed by pouring molten metal
into a Mold cavity, where it is cooled and later extracted from the Types
Mold. Metal casting is arguably the earliest and most influential Heat transfer is a process function (or path function), as opposed
industrial process in history. It’s used to make many of the metal to functions of state; therefore, the amount of heat transferred in
a thermodynamic process that changes the state of 1. Gas Porosity: Blowholes, open holes, pinholes
objects used in our daily lives: automotive parts, train wheels, 2. Shrinkage defects: shrinkage cavity
lamp posts, school bus pedals, and much more. Plus, metal casting a system depends on how that process occurs, not only the net
difference between the initial and final states of the process. 3. Mold material defects: Cut and washes, swell, drops, metal
foundries rely on metal recycling as a cost-efficient source of raw penetration, rat tail
material, significantly reducing wasted scrap metal that might end 4. Pouring metal defects: Cold shut, misrun, slag inclusion
up in landfills. Thermodynamic and mechanical heat transfer is calculated with
5. Metallurgical defects: Hot tears, hot spot.
the heat transfer coefficient, the proportionality between the heat
The Metal Casting Process flux and the thermodynamic driving force for the flow of heat. Heat
flux is a quantitative, vectorial representation of heat-flow through
a surface.
1. Patternmaking – A pattern is a replica of the exterior
of the casting. Patterns are typically made of wood,
metal, plastic, or plaster. Patternmaking is incredibly ❖ Solidification
important for industrial part-making, where precise
calculations are needed to make pieces fit and work Solidification is the transformation of liquid to solid, such as the
together. formation of ice, the freezing of solder in electrical circuits, and the
casting of metals in industrial practice. Casting of metals is one of
2. Core making – If a casting is hollow, an additional most economic and important manufacture routes. Solidification
piece of sand or metal (called a core) shapes the refers to the transformation of a material from a liquid state to a
internal form to make it hollow. Cores are typically solid state. This process is fundamental in casting and
metalworking industries where molten metals are poured into
strong yet collapsible so they can be easily removed
molds to create various components and products. During
from the finished casting.
solidification, as the temperature of the molten metal decreases,
its atoms or molecules arrange themselves into a solid crystalline
3. Moulding – To visualize the metal casting process so
structure. This transition is crucial as it determines the final
far, imagine yourself walking on the beach toward the
properties of the material, such as its mechanical strength,
ocean. Look at a footprint you leave behind in the wet
hardness, and microstructure.
sand. Your foot would be the core, and the impression
left in the sand is a Mold of your foot. Moulding is a ❖ Residual stress
multistep process that will form a cast around the ❖ Shrinkage
pattern using moulding sand. In casting, a Mold is residual stresses are stresses that remain in a solid material after
contained in a frame called a flask. Green sand, or Shrinkage is part of the production process in any company and the original cause of the stresses has been removed. Residual
moulding sand, is packed into the flask around the refers to the amount of material or product that is lost or gained stress may be desirable or undesirable. For example, laser
pattern. This is known as metal sand casting. Once the during this process due to quality problems and waste or errors in peening imparts deep beneficial compressive residual stresses into
standards. Shrinkage occurs during the solidification process due
, Module: 2 ❖ yield criterion ❖ Rolling Key aspects of backward extrusion include:
❖ Bulk Metal Forming yield criterion states that yielding of a ductile material begins rolling is a metal forming process in which metal stock is passed - The metal material flows backward around the punch and into
when the second invariant of deviatoric stress reaches a critical through one or more pairs of rolls to reduce the thickness, to make the die cavity.
In bulk metal forming processes, including forging, the metal is value.[2] It is a part of plasticity theory that mostly applies to the thickness uniform, and/or to impart a desired mechanical
exposed to a significant amount of plastic deformation before ductile materials, such as some metals. Prior to yield, material property. The concept is similar to the rolling of dough. Rolling is - This process is suitable for creating parts with intricate shapes
obtaining the final geometry. In near-net-shape processes, the response can be assumed to be of a linear elastic, nonlinear elastic, classified according to the temperature of the metal rolled. If the and details.
material flow is even more complicated, which makes the or viscoelastic behaviour. yield criterion is also formulated in temperature of the metal is above
deformation analysis challenging. Such complexity is related to the terms of the von Mises stress or equivalent tensile stress, . This is a its recrystallization temperature, then the process is known as hot - It is often used in forming processes requiring high precision and
nonlinearity of the final geometry, material and boundary scalar value of stress that can be computed from the Cauchy stress rolling. If the temperature of the metal is below its minimal material waste.
conditions in the forming process. Thus, to analyse the material tensor. In this case, a material is said to start yielding when the von recrystallization temperature, the process is known as cold rolling.
behaviour during forming processes, the main objectives are: Mises stress reaches a value known as yield strength, . The von In terms of usage, hot rolling processes more tonnage than any Backward extrusion is commonly employed in industries such as
Mises stress is used to predict yielding of materials under complex other manufacturing process, and cold rolling processes the most automotive manufacturing for producing parts like gear blanks,
(1) To establish the kinematic relationships between the loading from the results of uniaxial tensile tests. The von Mises tonnage out of all cold working processes. Roll stands holding bushings, and other components that require intricate geometries
undeformed and deformed parts. Most prominently, to predict the stress satisfies the property where two stress states with pairs of rolls are grouped together into rolling mills that can and precise tolerances. The choice between forward and backward
metal flow during the forming process (Geometry). equal distortion energy have an equal von Mises stress. quickly process metal, typically steel, into products such extrusion depends on factors such as part complexity, material
as structural steel (I-beams, angle stock, channel stock), bar stock, properties, and production volume.
(2) To establish the forming limits, i.e., to determine the possibility ❖ Fundamentals of Hot and Cold Working Processes and rails. Most steel mills have rolling mill divisions that convert
of performing the forming operation without causing any surface the semi-finished casting products into finished products.
❖ Drawing
or internal cracks or folds (Material). “Hot working and cold working” are to be done for the process of
“metal formation”. Through the “mechanical deformation process” ❖ Extrusion
Drawing is a similar process, using the tensile strength of the
(3) To estimate the load that is required to carry out such a “metal formation” of objects and parts is to take place. “Hot material to pull it through the die. It limits the amount of change
forming operation, which provides necessary information for tool working” has to be carried out in general at the temperature above Extrusion is a process used to create objects of a fixed cross- that can be performed in one step, so it is limited to simpler
design and equipment selection (Boundary condition). “recrystallization temperature”. But carried out below the “Melting sectional profile by pushing material through a die of the desired shapes, and multiple stages are usually needed. Drawing is the
point” of metal. Whereas “cold working process” has to be carried cross-section. Its two main advantages over other manufacturing main way to produce wire. Metal bars and tubes are also often
out below the “recrystallization temperature”. processes are its ability to create very complex cross-sections; and
❖ Sheet metal drawn.
to work materials that are brittle, because the material encounters
“Cold working” only compressive and shear stresses. It also creates excellent
Sheet metal forming is quite common for making shaped ❖ Deep drawing
surface finish and gives considerable freedom of form in the design
components, from soda cans to automotive car bodies. It is
“Cold working” is a process executed for the “metal formation process.
customary to refer to a material below the thickness of 6.35 mm as Deep drawing is a sheet metal forming process used industrially to
a sheet and thicker materials as plate. Because this book is limited process”. According to its name, this metal formation has to be produce cup-shaped, box-shaped, and other complex-curved
to bend forming, which is the simplest of sheet metal forming executed below “recrystallization temperature”. At room **Forward Extrusion Process:**
hollow-shaped sheet parts. Micro-cups/micro-boxes may be
operations, the basic discussion is limited to bending. It is easy to temperature hot working is to be done. In this case, expected produced with similar process configurations for micro-housing
visualize the extension of friction stir processing for enhanced recovery of metal cannot be gained. This process contrasts with the applications, such as for the packaging of micro-sensors and
formability to three-dimensional forming involving various stress “hot working” process as it disfigures the gained structure and is micro-actuators. As for conventional deep drawing, the major
states. A key aspect that is going to be emphasized is the plate unable to provide satisfaction in decreasing size. Unlike “hot Forward extrusion is a metal forming process where a billet or parameters which influence the process and product quality
forming. As will become clear, higher the thickness of material, working”, in “cold working process”, much more pressure needs to workpiece is forced through a die to create a desired shape. The include the dimensions of the blank, the punch and die
lower the formability. be applied. If metal is more ductile or flexible, then the process has process begins with a cylindrical billet being placed in a container, dimensions, especially the punch corner radii, the clearance
to be done through a “cold working process”. “Cold working known as a "can," with a die at one end. A ram or punch applies between the punch and the die, as well as the blank-holder
❖ Plastic Deformation: processes” cause “strain hardening”, “grain deformation”, and force to the billet, pushing it through the die cavity. The metal flows geometry, the interfacial conditions, and the holding pressures.
“crystal structure”. “Cold working process” is to be done for around the punch and through the die, taking the shape of the die Deep drawing is a more complex process than shearing/cutting
reducing flexibility of metal. cavity as it emerges on the other side. and bending because it usually combines processes such as
Plastic deformation is defined as a process in which the object due
to applied force changes its size or shape in a way that is not bending, unbending, stretching, compression, and shearing,
reversible. Plastic deformation is seen in many objects, including: “Hot working” During forward extrusion: depending on the part geometry to be produced. These processes
become more complex when the micro-structure of the sheet metal
“Hot working” is performed above the temperature of - The metal undergoes plastic deformation due to compressive becomes a dominant factor as the scale decreases
• Plastics “recrystallization”. Yet this process is said to be accomplished stress applied by the punch.
above “melting point” for recovery and deformation both can be
achieved at the same time. After applying heat to the “metal-plastic
• Metals deformation “the structure of the metal changes at the end. During
- Friction between the billet and the die walls helps in controlling
metal flow and achieving the desired shape.
this development, no residual stress takes place. Due to increased
• Soils
deformation takes place in this process the temperature used; the
stress needed for deformation is less. In this case, very less force is
- The final part typically has a length greater than the original
billet due to the material displacement.
required to be applied to metal. Then the metal gets plastically
• Rocks deformed. Due to “hot working process: metal grains are refined
which results in properties of metal
Forward extrusion is used to produce parts with a variety of
shapes, such as shafts, cylinders, and cups. It is suitable for both
• Concrete ❖ Forging
hot and cold forming, depending on the material and desired
properties of the final product.
The mechanisms that cause plastic deformation differ widely. Forging is the manufacturing process of hammering, pressing or
❖ Shearing
Plasticity in metals is a consequence of dislocations while in brittle rolling metal into shape. This is either delivered from a hammer,
materials such as concrete, rock and bone, plasticity occurs due to press or die. It is essentially the art of heating and working hot
the slippage of microcracks. There are two prominent mechanisms ❖ **Backward Extrusion Process:** Shearing, also known as die cutting, is a process that cuts stock
metal to design or shape that is fit for a specific purpose or use. By
of plastic deformation in metals, and they are without the formation of chips or the use of burning or melting.
working the material, it increases many of its properties, including
Strictly speaking, if the cutting blades are straight the process is
structure, conductivity and longevity. Forging offers a very useful
called shearing; if the cutting blades are curved then they are
and diverse medium for many industries with the process being
• Slip economically sound and achieving specific mechanical properties. Backward extrusion, also known as backward impact extrusion, shearing-type operations. The most commonly sheared materials
Forging is often categorized according to the temperature at which reverses the flow direction compared to forward extrusion. In this are in the form of sheet metal or plates. However, rods can also be
sheared. Shearing-type operations include blanking, piercing, roll
• Twinning it is performed, cold, warm, or hot forging. process, the die is located at the end of the ram or punch, and the
punch moves towards the stationary billet or workpiece. As the slitting, and trimming. It is used for metal, fabric, paper and
punch contacts the billet, it forces the metal material radially plastics.
outward against the die walls.
