FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
A Method Of Manufacturing Of 6XXX Series Aluminium Alloy Components
Bharat Forge Limited
An Indian company registered under the Indian Companies Act, 1956.
Mundhwa, Pune Cantonment, Pune - 411036, Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of invention
The present invention relates to the method of manufacturing of automobile
components using Aluminium alloys.
Particularly the present invention relates to manufacturing of aluminium alloy components using warm forging method.
More particularly the present invention is related to warm forging of 6XXX series aluminium alloys.
Introduction
Aluminium is used in many applications such as automotive, aerospace, packaging, construction etc. It is used because it is light weight, has good formability and corrosion resistance. One of the most important properties of Aluminium is its low density (2.7 g/cm3) which is approximately one third that of the steel (7.83 g/cm3). Aluminium and its alloys may be cast or processed in wrought form by many manufacturing processes such as forging, rolling, extrusion, stamping, powder metallurgy into various forms such as formed rod, bar, sheet, plate, foil, wire, tube, pipe, structural forms and composites. Its strength and ductility gives a good combination of forming flexibility. In addition, the heat treatable aluminium alloys can be formed with high strength to weight ratio.

Aluminium alloys can be divided into two major categories: cast and wrought. Wrought alloys can be further classified as heat treatable and non-heat treatable. For wrought alloys a four digit series is used to identify different composition families. The present invention relates to a 6XXX series aluminium alloy. This series has medium strength, good formability, machinability, weld ability, and corrosion resistance. Alloys of 6XXX series contain magnesium and silicon (magnesium and silicon additions of around 1%).
The 6XXX series aluminium alloys are traditionally hot or cold forged. Hot forging is performed above recrystallization temperature which is roughly about 60% of the melting temperature of material. In contrast, the cold forging is performed at room temperature or near to it. The hot forging and cold forging process for Aluminium alloy of 6XXX series are shown in Figure 1, and Figure 2 respectively.
There are certain drawbacks associated with the conventional method of forging of 6XXX series aluminium alloys. These drawbacks are given below: 1. Hot forging:
a. In hot forging, maintaining precise dimensional tolerance is difficult due to the shape formation at high temperature which is then cooled to achieve final part. Thus, net shape or near net shape parts cannot be produced from 6XXX series aluminium alloys using conventional hot forging process. Hence, parts have to be provided with machining allowances.

b. High temperature in hot deformation causes the formation of large
precipitates that produces low strength in the forgings. Magnesium (Mg)
and Silicon (Si) present in the alloys produce precipitates in the 6XXX
series alloys. Typically, the precipitates have a composition of Mg2Si. The
hot forged part does not have the mechanical or metallurgical properties as
required in the final component. Hence, to achieve the properties, heat
treatment is essential part of the manufacturing process for components
made from 6XXX series aluminium alloys.
c. The heat treatment is a time and energy consuming process step leading to
increase in production cost and cycle time.
d. Further, during the heat treatment process, distortion of the part may take
place needing subsequent process steps for correction.
2. Cold Forging:
a. In cold forging, in comparison with hot forging, comparatively higher
forging pressures/forces/loads are required which leads to considerably
lower die life.
b. Furthermore, the low workability of metals at room temperature restricts
the shape complexity of the parts which can be cold-forged.
c. The material forge ability at room temperature can be improved by
including an annealing treatment before cold forging. For complex
geometries and large deformations, one or more intermediate annealing
treatments may also be necessary to neutralize the work hardening effect.

This increases the cycle time of production and thus, reduces the productivity.
d. Soft annealing treatment before cold deformation causes the formation of
large precipitates that produces low strength in the forgings. The cold
forged part does not have the mechanical or metallurgical properties as
required in the final component. Hence, to achieve the properties, heat
treatment is essential component of the manufacturing process.
e. The heat treatment is a time and energy consuming process step leading to
increase in production cost and cycle time.
Thus, there exists a room for advancement over the existing technology in that an innovative method of manufacturing a 6XXX series aluminium alloy part has to be designed to overcome the drawbacks of the hot and cold forging methods.
Objects of invention
Some of the objects of the present disclosure which at least one embodiment herein satisfies are as follows:
It is an object of the present invention to provide a forging process for 6XXX series Aluminum alloy parts.
It is another object of the present invention to provide a forging process for 6XXX series Aluminum alloy parts which eliminates the post forging heat treatment.

It is yet another object of the present invention to provide a forging process for 6XXX series Aluminum alloy parts which reduces the overall cycle time of production.
It is further object of the present invention to provide a forging process for 6XXX series Aluminum alloy parts which allows production of near net shaped parts.
Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.
Brief description of accompanying drawings
Figure 1 shows a conventional method of forging a 6XXX series Aluminum alloy
using hot forging process.
Figure 2 shows a conventional method of forging a 6XXX series Aluminum alloy using cold forging process.
Figure 3 shows an invented method of forging a 6XXX series Aluminum alloy using warm forging process in accordance with one implementation of present invention.

Summary of invention
The present invention is directed to a method of manufacturing a 6XXX series Aluminum alloys. The invention is directed to overcome the various stated drawbacks of the prior art methods of hot forging and cold forging methods.
The invention provides a warm forging process for the manufacturing of a 6XXX series Aluminum alloy which eliminates (see Figures 1 and 2) the requirement of heat treatment process post the forging process step. This avoids any distortion in the forged part which may occur during the post forging heat treatment process.
The invented method starts with an extruded billet which is first solution annealed to dissolve all the precipitates in the solid solution of the alloy. The solution annealed billet is next warm-forged in a temperature range of 100 to 300 °C. The warm forged part is further cooled to room temperature in controlled conditions. The control-cooled part is further treated with post forging processes like shot blasting, crack detection etc. This is followed by machining process whose output is a final part ready to put in service.
Description of the invention
The present invention relates to a manufacturing method for a 6XXX series Aluminum alloy. This method consist of warm forging process step which helps in eliminating the post forging heat treatment cycle in the conventional manufacturing route.

The difference between hot forging, cold forging and warm forging lies in the forging temperature. The hot forging is done in a temperature range where recrystallization of the material takes place during the deformation. Cold forging is done at room temperature and hence, no recrystallization takes place during cold forging. Warm forging is performed above the room temperature but, below the recrystallization temperature. Thus, the forging temperature during warm forging lies between the forging temperature of cold and hot forging. This allows the warm forging method to combine the benefits of the hot forging and cold forging.
An Aluminium 6XXX series alloy is a precipitation hardened alloy. Magnesium (Mg) and Silicon (Si) are the major alloying elements present in the 6XXX series alloys which produce precipitates in them. Typically, the precipitates have a composition of Mg2Si. The extruded billet normally has multiple precipitates in it. The presence of precipitates increases the strength of the alloy and hence, makes deformation of the material difficult. If precipitates are present in the extruded billets during warm forging process, the force or load requirement for forging will be very high. Further the deformability of material will also be low which may lead to cracks during high deformation. Thus, this extruded billet is first solution annealed to dissolve all the precipitates in the solid solution of the alloy throughout the material and not just at the surface. This reduces the strength of the alloy significantly and increases its deformability. The solution treatment also

helps the metallurgical processes happening during the warm deformation of the alloy which helps in achieving the final properties in the part post forging.
The heat treatment processes (i.e. solution annealing and artificial ageing as shown in Figures 1 and 2) required in conventional manufacturing processes are eliminated in the warm forging method disclosed here due to a special metallurgical characteristic which is seen during the warm deformation of 6XXX series Aluminium alloys. If the 6XXX series alloy is deformed or forged at an optimum temperature and then cooled in a controlled environment two competing metallurgical processes are observed. As the forging is being done below recrystallization temperature, the material is not able to recrystallize and hence, its dislocation density increases. Further, a special phenomenon called dynamic precipitation also takes place during this deformation. The increased dislocation density in combination with dynamically precipitated precipitates strengthens the warm-forged material. Further, the controlled cooling of forged part after warm forging helps in increasing and consolidating the precipitates. Thus, the combination of warm forging and controlled cooling produces a part which has the required properties and hence, any subsequent heat treatment is not required.
In one aspect of present invention, there is provided a manufacturing process for manufacturing a 6XXX Aluminium Alloy components. The sequential process steps present in the manufacturing method of a 6XXX Aluminium Alloy component is disclosed with the help of Figure 3 as follows:

1. Inspecting and providing 6XXX series alloy extruded billet (1): The invented process starts with an extruded billet of a 6XXX series alloy. In one embodiment the billet is made of Al6082 aluminium alloy. The extruded billet is checked dimensionally for its shape and size. The billet is also checked for presence of any other defects like cracks etc.
2. Solution annealing (2): The extruded billet is next subjected to solution annealing process (2). The solution annealing process (2) of extruded billet can be performed in any type of furnace like gas fired, oil fired or electric furnace. The solution annealing process (2) is carried out in the temperature range of 450 to 550 °C. The soaking given to the extruded billet is in the range of 2 to 5 hours. After completion of the soaking time the soaked extruded billet is quenched to room temperature using water. The output of this process is solution annealed billet.
3. Billet heating (3): Next the solution annealed billet is heated (3) to a warm forging temperature. The solution annealed billet is heated (3) in a furnace to the warm forging temperature. The warm forging temperature lies in the range of 100 to 300 °C. For this purpose any type of furnace like oil fired, gas fired, electric or induction furnace can be used. Preferably an induction heater/ furnace is used for the solution annealed billet heating (3). In one embodiment the heating temperature is kept to be 200 ºC. The output of this process step is a heated billet.
4. Warm forging (4): The heated billet is next subjected to warm forging (4) operation. In one embodiment, the warm forging (4) temperature lies

between 100 to 300 °C. In another embodiment the forging temperature is preferably 200 ºC. The warm forging (4) can be carried out in any type of forging equipment like hammer, mechanical press, screw press or hydraulic press. In one embodiment, a higher strain rate producing press like a mechanical press is used for warm forging (4). The output of this process step is a warm forged part.
5. Controlled cooling (5): The warm forged part is next cooled in a controlled fashion in a control cooling conveyor. The cooling rate during this process is controlled during this step to achieve the final properties of the part. In one embodiment, the control cooling conveyor is enclosed from four sides (top, bottom, left side and right side) to reduce the cooling rate of the forged parts. In another embodiment the left side and right side walls of the control cooling conveyors have windows which can be kept closed, open or partially open in order to control the cooling rate of the parts. In still another embodiment, the parts may be kept covered in glass wool which acts as an insulator so as to achieve the slowest cooling rate during the cooling of the forged parts. The output of this process is a control cooled part.
6. Post forging treatment (6): The control cooled part is next subjected to post forging treatments (6) like shot blasting crack detection etc. The output of this process step is a treated part.
7. Machining (7): Next the treated part is subjected to machining operations (7) to get a final product which is ready to be put in service.

It is evident from the foregoing discussion that the invention has a number of embodiments.
In the preferred embodiment of the present invention, the invention discloses a method of manufacturing of aluminium alloy components, said method comprising the steps of:
a. providing an extruded billet of a 6XXX series alloy (1) and
dimensionally checking it for shape, size and ensuring that said billet is
devoid of defects such as cracks to produce a checked billet;
b. subjecting said checked billet to solution annealing process (2) to
produce a solution annealed billet;
c. heating (3) said solution annealed billet to raise the temperature of said
solution annealed billet to warm forging temperature to produce a
heated billet;
d. warm forging (4) said heated billet to produce a warm forged
component;
e. control-cooling (5) said warm forged component to cool it down to a
predetermined temperature to produce a control-cooled component;
f. subjecting said control-cooled component to post-forging treatment (6)
to produce a treated component;
g. subjecting said treated part to machining (7) to produce the final
component.

In an embodiment of the method of manufacturing aluminium alloy components of the present invention, said alloy is a 6XXX series alloy, preferably Al6082.
In a further embodiment of the method of the present invention, said step b is performed in an annealing furnace which is fired by gas or oil or electricity.
In another embodiment of the method of the present invention, said step b comprises the sub-steps of soaking said checked billet to produce a soaked billet followed by quenching said soaked billet to produce said solution annealed billet, and wherein the temperature of soaking step is in the range of 450 to 550 ºC and the soaking period is in the range between 2 to 5 hours.
In yet another embodiment of the method of the present invention, the quenching fluid is water.
In a still further embodiment of the method of the present invention, said heating of solution annealed billet of step c is carried out in a heating furnace at a temperature between 100 ºC to 300 ºC, and wherein said heating furnace is a gas fired, oil fired, electric or induction heating furnace.
In another embodiment of the method of the present invention, the temperature in said heating furnace of step c is maintained at 200 ºC.

In a further embodiment of the method of the present invention, temperature of step d is maintained between 100 ºC to 300 ºC, and the step d itself is carried out using a forging equipment selected from a group comprising a hammer, mechanical press, screw press and a hydraulic press. In another embodiment of the present invention, the forging equipment is preferably a mechanical press. In yet another embodiment of the present invention, the forging temperature is preferably 200 ºC.
In a still further embodiment of the method of the present invention, in step e, said control cooling is carried out using a control cooling conveyor that is enclosed from four sides. Furthermore, at least one wall of the control cooling conveyors may have at least one window which can be kept closed, open or partially open in order to control the cooling rate of the parts. As another embodiment, during the control cooling step, the parts are covered in glass wool insulator.
The invention is now explained using some illustrations.
EXAMPLE 1:
Test pieces of size φ 10 by 15 mm length and made from Al6082 alloy were used for performing compression tests to compare the properties achieved by cold, warm and hot deformation. The test pieces were deformed by 50% at different

temperatures (room temperature, 200 ºC, 250 ºC, 300 ºC, 400 ºC and 450 ºC) and velocities (0.15, 1.5, 15 mm/s).
For cold deformation (i.e. Room Temperature) the test piece was given soft annealing treatment prior to deformation. For warm deformation (200 ºC, 250 ºC, 300 ºC) the test pieces were given solution treatment prior to deformation. For hot deformation (400 ºC and 450 ºC), the as received raw material was used as it is.
After deformation, hardness of the test pieces were checked to understand its properties. The results showed that hot and cold deformed test pieces were not able to achieve the target hardness of 105 HV. To achieve the target hardness, heat treatment of the test pieces had to be done.
Among the warm deformed test pieces best hardness (120 HV) was achieved for sample deformed at 200 ºC with the highest deformation velocity of 15 mm/s. The test piece achieved the target hardness without requirement of any post deformation heat treatment.
This experiment showed that solution annealing treatment (2) followed by warm deformation (4) gives the best hardness without the requirement of any post deformation heat treatment (solution treatment + Aging) which is not possible through either the cold deformation or the hot deformation. Thus, solution treatment followed by warm deformation specifically at 200 ºC completely

eliminates the requirement of aging treatment from the production process which is compulsorily required during hot or cold forging. Further, this experiment also showed that as the deformation velocity increases from 0.15 mm/s to 15 mm/s the properties improved. Hence, it could be concluded that higher press velocity or strain rate is beneficial in case of warm forging.
EXAMPLE 2:
Plant level trial was taken on samples of size φ 80 by 120 mm length. The samples were warm forged at 150º, 200º and 250º C. Further some samples were hot forged at 420 ºC. Forging was performed on a mechanical press of 1000T capacity. Among the various forging equipment’s, the mechanical press is one having highest deformation velocity. The samples were solution treated at 530 ºC for 4 hr prior to warm forging step.
After forging, the warm forged samples were not given any heat treatment while the hot forged samples were given solution treatment followed by aging cycle. Solution treatment was given at 530 ºC for 4 hrs. Aging treatment was done at 175 ºC for 10 hrs.
After this the properties of hot forged & heat treated samples and warm forged samples was tested. Results showed that warm forged samples achieved both the target tensile properties as well as hardness properties. Hot forged samples could

not achieve the properties in absence of heat treatment. When the hot forged samples were heat treated then only it achieved the required properties.
Among the warm forged samples, the samples forged at 200 ºC showed the highest values of tensile strength (UTS: 346 MPa; YS: 317 MPa) and hardness (141 HV).
When the complete process of hot forging and warm forging is compared for Example 2, it can be seen that aging cycle is completely eliminated in the warm forging process. The solution treatment cycle has to be done in warm forging before forging and in hot forging it is done after the forging process. Thus, in the overall production process of warm forging, 10 hrs of cycle time for aging is eliminated. Thus, warm forging process leads to improvement in productivity.
The invented warm forging method for Al6XXX series alloys has following advantages:
1. It is an extremely important and economical process, especially for producing round or nearly round parts in large quantities.
2. Warm forging allows production of net shape or near net shape parts.
3. It eliminates the requirement of post forging heat treatment. Heat treatment is one of the major reasons which causes distortion in forged parts. Elimination of heat treatment helps in avoiding this type of distortion.

4. Near net shape helps in reducing the machining and finishing operations required after forging.
5. Cost of production is also reduced as the aging cycle required after the cold and hot forging process is completely eliminated.
While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. A method of manufacturing of 6XXX series aluminium alloy components,
said method comprising the steps of:
a. supplying an extruded billet of a 6XXX series alloy (1) and checking it
dimensionally for shape, size and ensuring that said billet is devoid of
defects such as cracks to produce a checked billet;
b. subjecting said checked billet to solution annealing (2) to produce a
solution annealed billet;
c. heating (3) said solution annealed billet to raise the temperature of said
solution annealed billet to warm forging temperature to produce a
heated billet;
d. warm forging (4) said heated billet to produce a warm forged
component;
e. control-cooling (5) said warm forged component to cool it down to a
predetermined temperature to produce a control-cooled component;
f. subjecting said control-cooled component to post-forging treatment (6)
to produce a treated component;
g. subjecting said treated part to machining (7) to produce the final
component.
2. The method as claimed in claims 1, wherein said step b is performed in an
annealing furnace wherein said annealing furnace is a gas fired or oil fired
or electric furnace.

3. The method as claimed in claims 1 to 2, wherein said step b comprises the sub-steps of soaking said checked extruded billet to produce a soaked billet followed by quenching said soaked billet to produce said solution annealed billet.
4. The method as claimed in claim 3, wherein the temperature of soaking step is in the range of 450 to 550 ºC, the soaking period is in the range between 2 to 5 hours and the quenching fluid is water.
5. The method as claimed in claims 1 to 4, wherein said step c is carried out in a heating furnace at a temperature between 100 ºC to 300 ºC, wherein said heating furnace is gas fired, oil fired, electric or induction heating furnace.
6. .The method as claimed in claims 5 wherein the temperature in said heating furnace is maintained at 200 ºC.
7. The method as claimed in claim 1 to 6, wherein temperature of step d is maintained between 100 ºC to 300 ºC.
8. The method as claimed in claims 1 to 7 wherein step d is carried out using a forging equipment selected from a group comprising a hammer, mechanical press, screw press and a hydraulic press.
9. The method as claimed in claim 8 wherein step d is carried out using a mechanical press.
10. The method as claimed in claims 1 to 9, wherein said aluminium alloy is Al6082.

11. The method as claimed in claims 1 to 10, wherein in step e, said control cooling is carried out using a control cooling conveyor that is enclosed from four sides and wherein at least one wall of the control cooling conveyors has at least one window which can be kept closed, open or partially open in order to control the cooling rate of the parts.
12. The method as claimed in claim 11, wherein during the control cooling step, the parts are covered in glass wool insulator.