FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A method of metal treatment by a squeezing process.
APPLICANT(S)
Crompton Greaves Limited, CG House, 6th Floor, Dr. Annie Besant Road,
Worli, Mumbai - 400030, Maharashtra, India, an Indian Company.
INVENTOR(S)
Mudragada Sathyanarayana, Shaikh Bashit, Sathe Mahesh and Nemade Janamejay of Crompton Greaves Ltd, Global R&D, Crompton Greaves, Kanjurmarg (East), Mumbai- 400042 Maharashtra, India; an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of thermal engineering and metal treatment processes.
Particularly, this invention relates to a method of metal treatment by a squeezing process.
BACKGROUND OF THE INVENTION:
Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.
Metal casting is one of the most common casting processes. Metal patterns are more expensive but are more dimensionally stable and durable. Metallic patterns are used where repetitive production of castings is required in large quantities.
High pressure die casting leaves porosity in the metal.
It has been observed that in rotors which are obtained after die casting, there is porosity in the aluminium which results in loss of electrical conductivity of aluminium and magnetic properties of steel laminations due to thermal stresses. Hence, there is a need to improve there, thereby providing an improved rotor.
OBJECTS OF THE INVENTION:
An object of the invention is to improve electrical conductivity of metal (typically, of aluminium) and mechanical properties of metal during the process of casting.

Another object of the invention is to improve electrical conductivity and mechanical properties of metal after the solidification process of casting.
Yet another object of the invention is to improve the electrical and thermal conductivity of aluminium pure aluminium and magnetic properties of cold rolled non orientated electrical steels
SUMMARY OF THE INVENTION:
According to this invention, there is provided a method of metal treatment by a squeezing process, said process comprises the steps of: i. at least a first step of casting wherein liquid metal is poured in a die in order
to cast it in a required shapes aid casting being done at a first pre-defined
temperature; ii. at least a second step of allowing said casted metal to cool up to a second
pre-defined second temperature in order to obtain die-casted metal; iii. at least a third step of further heating said die casted metal, in a furnace, up
to a third pre-defined temperature; iv. at least a fourth step of holding (or soaking) said die casted metal up to a
first pre-defined period of time at a fourth pre-defined temperature; v. at least a fifth step of removing said die-casted metal from furnace and
squeezing said die cast metal with an aligned body adapted to exert intended
pressure and allowing said die-casted metal to reach up to a fifth pre-defined
temperature; vi. at least a sixth step of heating said squeezed die casted metal up to a sixth
pre-defined temperature for a second pre-defined period of time; vii. at least a seventh step of furnace cooling said squeezed die casted metal up
to a seventh pre-defined temperature; and

viii. at least an eighth step of quenching said squeezed furnace cooled die casted metal up to an eighth pre-defined temperature.
Typically, said first pre-defined temperature is 700° Celsius.
Typically, said second pre-defined temperature is 200° Celsius.
Typically, said cooling occurs in a die.
Typically, said third pre-defined temperature is 600° Celsius.
Typically, heating rate is about 4°C / minute.
Typically, said first pre-defined period of time is 2 hours.
Typically, said fourth pre-defined temperature is 600° Celsius.
Typically, said pressure applied is 150 Mpa.
Typically, said fifth pre-defined temperature is 350° Celsius.
Typically, said sixth pre-defined temperature is 600° Celsius.
Typically, said second pre-defined period of time is 10 minutes.
Typically, said seventh pre-defined temperature is 400° Celsius.
Typically, said eighth pre-defined temperature is 30 - 25° Celsius.

Specifically, said metal in the aforesaid steps is Aluminium. Specifically, said method being used for making die cast rotor.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic flow diagram of the steps of the current invention;
Figure 2 illustrates 'as cast' microstructures in aluminium, when it is heat treated according to the prior art;
Figure 3 also illustrates 'as cast' microstructures in aluminium, when it is heat treated according to the prior art;
Figure 4 illustrates an introduction of a new and additional step in the regular casting process in order to improve electrical and magnetic properties;
Figure 5 illustrates the increase in electrical conductivity as the pressure rises from normal casting to 150 MPa;
Figures 6a and 6b illustrate intra-bar resistance in terms of graph (as cast versus squeezing processing of this invention at various pressures);
Figures 7a and 7b illustrate inter-bar resistance in terms of graph (as cast versus squeezing processing of this invention at various pressures);

Figure 8 illustrates magnetic properties in terms of graph (as cast versus squeezing processing of this invention at various pressures;
Figure 9a illustrates microstructure of electrical steel after die-casting; and
Figure 9b illustrates microstructure of electrical steel after heat treatment.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a method of metal treatment by a squeezing process. Specifically, this invention relates to a process of squeezing (applying high pressure) of pure aluminium (LM 0) used for die cast rotor (die cast rotor consists of electrical steel and pure aluminium).
Figure 1 illustrates a schematic flow diagram of the steps of the current invention.
Figure 2 illustrates 'as cast' microstructures in aluminium, when it is heat treated according to the prior art. It can be seen that the grain structure is such that it obstructs the flow of electrons. Figure 2a illustrates resolution at 50x. Figure 2b illustrates resolution at lOOx. Figure 2c illustrates resolution at 200x.
Figure 3 also illustrates 'as cast' microstructures of aluminium, when it is heat treated according to the prior art. It can be seen that the grain structure is elongated and equi-axised which makes it less conducive to electrical and magnetic properties. Also, porosity in end ring needs to be reduced.
In accordance with an embodiment of this invention, there is provided a first step (S1) of casting wherein liquid metal is poured in a die in order to cast it in a required shape. This is the existing step of casting. Typically, the cast metal is up

to 700° Celsius. For rotors, the metal used is Aluminum. In a least one embodiment, this step is used for heat treatment of metal used for electrical devices, typically rotating electrical devices, and specifically for rotors.
In accordance with another embodiment of this invention, there is provided a second step (S2) of allowing the metal to cool up to 200° Celsius. The cooling occurs in a die and the output is die casted metal. In at least one embodiment, this step is used for cooling of metal used for electrical devices, typically rotating electrical devices, and specifically for rotors. Typically, the cooling from cast state of 700° Celsius to relatively cooled state of 200° Celsius takes up to 1 minute.
In accordance with yet another embodiment of this invention, there is provided a third step (S3) of further heating die casted metal up to 600° Celsius for predetermined period of time is about 4°C / minute. Thermal treatment of die cast metal reduces mechanical stresses in the metal, thereby lowering magnetic losses. In at least one embodiment, this step is used for heating of die casted metal used for electrical devices, typically rotating electrical devices, and specifically for rotors.
In accordance with still another embodiment of this invention, there is provided a fourth step (S4) of holding (or soaking) the die casted metal up to 2 hours. The die casted metal is held at the heated temperature of up to 600° Celsius for a predetermined time period of up to 2 hours. In at least one embodiment, this step is used for holding (or soaking) of die casted metal, used for electrical devices, at a pre-heated temperature, typically rotating electrical devices, and specifically for rotors.

In accordance with an additional embodiment of this invention, there is provided a fifth step (S5) of removing motor from furnace and squeezing the die cast metal with an aligned body adapted to exert intended pressure. The step of squeezing involves the step of applying high pressure on to the die casted metal. In at least one embodiment, this step is used for squeezing of die casted metal, used for electrical devices, typically rotating electrical devices, and specifically for rotors. Squeezing operation reduces the porosity levels in die casted metal and also breaks the cast structure of the die casted metal. Reduction of porosity (densification) improves the electrical and thermal conductivity of the die casted metal. The pressure applied is 150 Mpa. During this process, the die casted metal reaches up to 350 ° Celsius. Figure 4 illustrates an introduction of a new and additional step in the regular casting process in order to improve electrical and magnetic properties.
In accordance with still an additional embodiment of this invention, there is provided a sixth step (S6) of heating the die casted metal up to 600° Celsius for about 10 minutes. After the process of squeezing, the die casted metal is again heated. In at least one embodiment, this step is used for heating of squeezed die casted metal, used for electrical devices, typically rotating electrical devices, and specifically for rotors.
In accordance with another additional embodiment of this invention, there is provided a seventh step (S7) of furnace cooling the die casted metal up to 400° Celsius. In at least one embodiment, this step is used for furnace cooling of squeezed die casted metal, used for electrical devices, typically rotating electrical devices, and specifically for rotors.
In accordance with yet another additional embodiment of this invention, there is provided an eighth step (S8) of quenching the die casted metal up to 30 or 25°

Celsius. In at least one embodiment, this step is used for quenching of squeezed die casted metal, used for electrical devices, typically rotating electrical devices, and specifically for rotors. Fast quenching also breaks metallurgical bonds between steel laminations and aluminium conductor bars due to large differential in thermal expansions. In cases wherein the metal is Aluminium, specifically, formation of aluminium oxide and iron oxide increases the inter-bar resistance, thereby lower current losses.
Typically, the metal in the aforesaid steps is Aluminium.
According to a non-limiting exemplary embodiment, these steps were carried out on Aluminium used in rotor manufacture. The following advantages were observed:
1. Improvements of electrical conductivity by 17% and thermal conductivity by 40 % against high pressure die cast rotor;
2. Improvement of magnetic properties by 40 % against high pressure die cast rotor; and
3. Inter bar resistance improved by 7-9 times against high pressure die cast rotor.
Improvement of above properties leads to reduction in rotor losses and that leads to improving the motor performance in terms of lower temperature rise, higher RPM, and higher efficiency.
An end ring was cast using the above process. The squeezing process was carried out at various pressures. Figure 5 illustrates the increase in electrical conductivity as the pressure rises from normal casting to 150 MPa (in accordance with this invention.

Figures 6a and 6b illustrate intra-bar resistance in terms of graph (as cast versus squeezing processing of this invention at various pressures). It can be observed from Figures 6a and 6b that intra-bar resistance (purple colour) drastically reduces as compared to prior art (red colour).
Figures 7a and 7b illustrate inter-bar resistance in terms of graph (as cast versus squeezing processing of this invention at various pressures). It can be observed from Figures 7a and 7b that inter-bar resistance (purple colour) drastically increases as compared to prior art (red colour).
Figure 8 illustrates magnetic properties of cold rolled non oriented electrical steel in terms of graph (as cast versus squeezing processing of this invention at various pressures. It can be observed from Figure 8 that magnetic property in accordance with the current invention drastically improves as compared to prior art (red colour).
Figure 9a illustrates microstructure of electrical steel after die-casting.
Figure 9b illustrates microstructure of electrical steel after heat treatment.
It can be observed that the grain structure is such that it does not obstruct the flow of electrons.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly

understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A method of metal treatment by a squeezing process, said process comprising the steps of: i. at least a first step of casting wherein liquid metal is poured in a die in
order to cast it in a required shapes aid casting being done at a first
pre-defined temperature; ii. at least a second step of allowing said casted metal to cool up to a
second pre-defined second temperature in order to obtain die-casted
metal; iii. at least a third step of further heating said die casted metal, in a
furnace, up to a third pre-defined temperature for predetermined
period of time; iv. at least a fourth step of holding (or soaking) said die casted metal up
to a first pre-defined period of time at a fourth pre-defined
temperature; v. at least a fifth step of removing said die-casted metal from furnace
and squeezing said die cast metal with an aligned body adapted to
exert intended pressure and allowing said die-casted metal to reach up
to a fifth pre-defined temperature; vi. at least a sixth step of heating said squeezed die casted metal up to a
sixth pre-defined temperature for a second pre-defined period of time; vii. at least a seventh step of furnace cooling said squeezed die casted
metal up to a seventh pre-defined temperature; and viii. at least an eighth step of quenching said squeezed furnace cooled die
casted metal up to an eighth pre-defined temperature.

2. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said first pre-defined temperature is 700° Celsius.
3. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said second pre-defined temperature is 200° Celsius.
4. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said cooling occurs in a die.
5. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said third pre-defined temperature is 600° Celsius and heating rate is about 4°C / minute.
6. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said first pre-defined period of time is 2 hours.
7. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said fourth pre-defined temperature is 600° Celsius.
8. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said pressure applied is 150 Mpa.
9. The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said fifth pre-defined temperature is 350° Celsius.
10.The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said sixth pre-defined temperature is 600° Celsius.

11 .The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said second pre-defined period of time is 10 minutes.
12.The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said seventh pre-defined temperature is 400° Celsius.
13.The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said eighth pre-defined temperature is 30 - 25° Celsius.
14.The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said metal in the aforesaid steps is Aluminium.
15.The method of metal treatment metal by a squeezing process as claimed in claim 1, wherein said method being used for making die cast rotor.