Roll ForgingRoll Forging..

Roll Forging.Roll Forging.

Roll Forging is a deformation Roll Forging is a deformation process used to reduce the cross process used to reduce the cross section of a cylindrical or section of a cylindrical or rectangular work piece by passing it rectangular work piece by passing it through a set of opposing rolls that through a set of opposing rolls that have grooves matching the desired have grooves matching the desired shape of the final part. shape of the final part.

Roll Forging.Roll Forging.

Roll Forging is classified as Forging Roll Forging is classified as Forging process even though it utilizes rolls.process even though it utilizes rolls.

Rolls do not turn continuously in roll Rolls do not turn continuously in roll forging but rotate through only a forging but rotate through only a portion of one revolution portion of one revolution corresponding to the desired corresponding to the desired deformation to be accomplished on deformation to be accomplished on the part.the part.

Roll Forging.Roll Forging.

Roll Forging.Roll Forging.

Roll Forged parts are generally Roll Forged parts are generally stronger and possess favorable grain stronger and possess favorable grain structure compared to competing structure compared to competing processes such as machining that processes such as machining that might be used to produce the same might be used to produce the same part geometry.part geometry.

Roll Forging products.Roll Forging products.

In roll forging round or flat bar stock In roll forging round or flat bar stock is reduced in thickness and is reduced in thickness and increased in length to produce such increased in length to produce such products as axles, tapered levers products as axles, tapered levers and leaf springs.and leaf springs.

Swaging.Swaging.

Swaging is a process used to reduce Swaging is a process used to reduce the diameter of a tube or solid rod.the diameter of a tube or solid rod.

Swaging is often performed on the Swaging is often performed on the end of a work piece to create a end of a work piece to create a tapered section.tapered section.

Examples of Parts made by Examples of Parts made by Swaging.Swaging.

Swaging.Swaging.

Swaging Swaging process as process as shown in figure shown in figure is accomplished is accomplished by means of by means of rotating dies rotating dies that hammer a that hammer a work piece work piece radially inward radially inward to taper it as to taper it as the piece is fed the piece is fed in to the dies.in to the dies.

Swaging.Swaging. In swaging die the In swaging die the

die itself acts as die itself acts as hammer. Repeated hammer. Repeated blows are blows are delivered from delivered from various angles , various angles , causing the metal causing the metal to flow inward and to flow inward and assume the assume the contour of the die.contour of the die.

Most of the Most of the swaging is usually swaging is usually performed cold.performed cold.

Swaging.Swaging.

Some swaging Some swaging processes are processes are performed hot . performed hot . For example hot For example hot swaging is used swaging is used to reduce and to reduce and form the end of form the end of a pressurized a pressurized gas cylinder.gas cylinder.

Net shape and near net shape Net shape and near net shape Forging.1Forging.1

To minimize both the expense and To minimize both the expense and waste considerable effort has been waste considerable effort has been made to develop processes that can made to develop processes that can form parts close enough to final form parts close enough to final dimensions that little or no final dimensions that little or no final machining is required.machining is required.

These are referred to as net shape These are referred to as net shape or near net shape processes and may or near net shape processes and may also be referred to as precision also be referred to as precision forging.forging.

Net shape and near net shape Net shape and near net shape Forging.2Forging.2

Cost savings usually result from the Cost savings usually result from the elimination of reduction or elimination of reduction or elimination of secondary machining , elimination of secondary machining , the companion reduction in scrap the companion reduction in scrap and an over all decrease in the and an over all decrease in the amount of energy required to amount of energy required to produce the product.produce the product.

Net shape and near net shape Net shape and near net shape Forging.3Forging.3

Design and implementation of net Design and implementation of net shape processing can be rather shape processing can be rather expensive ,application is usually expensive ,application is usually reserved for parts where a reserved for parts where a significant cost reduction can be significant cost reduction can be achieved.achieved.

Extrusion.Extrusion.

In the extrusion process metal is In the extrusion process metal is compressed and forced to flow through a compressed and forced to flow through a suitably shaped die to form a product suitably shaped die to form a product with reduced but constant cross section.with reduced but constant cross section.

Extrusion may be performed either hot Extrusion may be performed either hot or cold , hot extrusion is commonly or cold , hot extrusion is commonly employed for many metals to reduce the employed for many metals to reduce the forces required.forces required.

Extrusion.2Extrusion.2 Extrusion process is like Extrusion process is like

squeezing tooth paste squeezing tooth paste out of a tube.out of a tube.

In the case of metals a In the case of metals a common arrangement is common arrangement is to have a heated billet to have a heated billet placed inside of confining placed inside of confining chamber.chamber.

A ram advances from one A ram advances from one end ,causing the billet to end ,causing the billet to first upset and conform first upset and conform to the confining to the confining chamber.chamber.

Extrusion.3Extrusion.3

As the ram As the ram continues to continues to advance the advance the pressure builds pressure builds until the until the material flows material flows plastically plastically through the die through the die and extrudesand extrudes..

Extrusion.( Materials)Extrusion.( Materials)

Aluminum ,Magnesium ,copper , Lead , and Aluminum ,Magnesium ,copper , Lead , and alloys of these metals are commonly alloys of these metals are commonly extruded , taking advantage of the relatively extruded , taking advantage of the relatively low yield strength and low hot working low yield strength and low hot working temperature.temperature.

Steel , stainless steel ,Nickel based alloys and Steel , stainless steel ,Nickel based alloys and titanium based alloys are far more difficult to titanium based alloys are far more difficult to extrude. Their yield strength and the metals extrude. Their yield strength and the metals have the tendencyhave the tendency to weld to the walls of to weld to the walls of the die and confining chamber under the die and confining chamber under the required conditions of temperature the required conditions of temperature and pressure. and pressure.

Extrusion.( Materials)2Extrusion.( Materials)2

With the development and use of With the development and use of phosphate based and molten glass phosphate based and molten glass lubricants ,hot extrusion can be routinely lubricants ,hot extrusion can be routinely produced from these high strength , high produced from these high strength , high temperature metals.temperature metals.

These lubricants are able to with stand These lubricants are able to with stand the required temperatures and adhere to the required temperatures and adhere to the billet, flowing and thinning in a way the billet, flowing and thinning in a way that prevents metal to metal contact that prevents metal to metal contact through out the process.through out the process.

Extrusion.Extrusion. Almost any cross sectional Almost any cross sectional

shape can be extruded shape can be extruded from the non ferrous from the non ferrous metals.metals.

Size limitations are few Size limitations are few because presses are now because presses are now available that can extrude available that can extrude any shape that can be any shape that can be enclosed with in 75 cm enclosed with in 75 cm diameter circle.diameter circle.

In the case of steels and In the case of steels and other high strength metals other high strength metals the shapes and sizes are a the shapes and sizes are a bit more limitedbit more limited

Extrusion Products.Extrusion Products.

Extrusion.Extrusion.

Extrusion has a number of attractive Extrusion has a number of attractive features .many shapes can be produced as features .many shapes can be produced as extrusions that are not possible by rolling extrusions that are not possible by rolling such as longitudinal holes.such as longitudinal holes.

No draft is required.No draft is required. Billet to product cross sectional area ratios Billet to product cross sectional area ratios

can be 100 to 1 for the weaker metals.can be 100 to 1 for the weaker metals. The major limitation of the process is the The major limitation of the process is the

requirement that the cross section be requirement that the cross section be uniform for the entire length of the product.uniform for the entire length of the product.

Extrusion.Extrusion. Extrusion products have good surface Extrusion products have good surface

finish and dimensional precision.finish and dimensional precision. For most shapes tolerances of For most shapes tolerances of ±0.003 ±0.003

cm/cm easily attainable.cm/cm easily attainable. Grain structure is typical of other hot Grain structure is typical of other hot

worked metals but strong directional worked metals but strong directional properties ( longitudinal versus properties ( longitudinal versus transverse ) are usually observed.transverse ) are usually observed.

Standard product lengths are about 6 Standard product lengths are about 6 to 7 m but lengths in excess of 12 m to 7 m but lengths in excess of 12 m have been produced.have been produced.

Extrusion methods.Extrusion methods.

Extrusions can be produced by Extrusions can be produced by various techniques and equipment various techniques and equipment configurations.configurations.

Hot extrusion is usually done by Hot extrusion is usually done by two methods:two methods:

1.1. DirectDirect

2.2. In Direct In Direct

Direct Extrusion.Direct Extrusion. In direct extrusion a In direct extrusion a

solid ram drives the solid ram drives the entire billet to and entire billet to and through a stationary through a stationary die and must die and must provide additional provide additional power to over come power to over come the frictional the frictional resistance between resistance between the surface of the the surface of the moving billet and moving billet and the confining the confining chamber.chamber.

Direct Extrusion.Direct Extrusion.

One of the problems in direct extrusions One of the problems in direct extrusions is the significant friction that exist is the significant friction that exist between the work surface and the walls between the work surface and the walls of the container as the work piece is of the container as the work piece is forced to slide toward the die opening.forced to slide toward the die opening.

This friction causes a substantial This friction causes a substantial increase in the ram force required in increase in the ram force required in direct extrusion.direct extrusion.

In Direct ExtrusionIn Direct Extrusion

In Indirect extrusion In Indirect extrusion the die is mounted to the die is mounted to the ram rather than the ram rather than at the opposite end of at the opposite end of the container. As the the container. As the ram penetrates in to ram penetrates in to the work , the metal the work , the metal is forced to flow is forced to flow through the clearance through the clearance in a direction opposite in a direction opposite to the direction of to the direction of motion of the ram.motion of the ram.

In Direct ExtrusionIn Direct Extrusion

Since the work is not forced to Since the work is not forced to move relative to the container , move relative to the container , there is no friction at the container there is no friction at the container walls and the ram force is walls and the ram force is therefore lower than the direct therefore lower than the direct extrusion. extrusion.

Direct and In direct Direct and In direct extrusion.extrusion.

In Direct In Direct Extrusion( Limitations)Extrusion( Limitations)

Added complexity of the in direct process Added complexity of the in direct process serves to increase the purchase price serves to increase the purchase price and maintenance cost of the required and maintenance cost of the required equipment.equipment.

In direct extrusions are imposed by the In direct extrusions are imposed by the lower rigidity of the hollow ram . lower rigidity of the hollow ram .

Extrusion speeds.Extrusion speeds.

Speeds of the hot extrusion process are fast so Speeds of the hot extrusion process are fast so as to minimize the cooling of the billet with in as to minimize the cooling of the billet with in the chamber.the chamber.

Extruded products can emerge at rates up to Extruded products can emerge at rates up to 300 m/min.300 m/min.

Extrusion speeds may be restricted by the Extrusion speeds may be restricted by the large amounts of heat that are generated by large amounts of heat that are generated by the massive deformation and the associated the massive deformation and the associated rise in temperature.rise in temperature.

Extrusion speeds 2Extrusion speeds 2

Sensors are often used to monitor the Sensors are often used to monitor the temperature of the emerging product temperature of the emerging product and feed this information back to a and feed this information back to a control system.control system.

For materials whose properties are For materials whose properties are not sensitive to strain rate , ram speed not sensitive to strain rate , ram speed may be maintained at the highest level may be maintained at the highest level that will keep the product temperature that will keep the product temperature below some predetermined value. below some predetermined value.

Extrusion speedsExtrusion speeds

Lubrication is another important Lubrication is another important area of concern. area of concern.

If the reduction ratio is 100 the If the reduction ratio is 100 the product will be 100 times longer product will be 100 times longer than the starting billet and if the than the starting billet and if the product has a complex cross section product has a complex cross section its perimeter will be considerably its perimeter will be considerably larger than the starting material.larger than the starting material.

Extrusion lubricantExtrusion lubricant

Surface area of the product is the length Surface area of the product is the length times the perimeter as the length and times the perimeter as the length and perimeter both increased the surface perimeter both increased the surface area of the final product will be greater area of the final product will be greater than the surface area of the starting than the surface area of the starting work piece.work piece.

A lubricant that is applied to the starting A lubricant that is applied to the starting piece must thin considerably as the piece must thin considerably as the material passes through the die and is material passes through the die and is converted to the product.converted to the product.

Extrusion lubricant 2Extrusion lubricant 2

An acceptable lubricant is expected An acceptable lubricant is expected to reduce friction and act as a to reduce friction and act as a barrier to heat transfer at all stages barrier to heat transfer at all stages of the process.of the process.

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