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, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A manufacturing process of stampings using semi-processed electrical
steel grade.
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Dumbre Jayshri and Ingle Asha, all of Crompton Greaves Limited, CG Global R&D Centre, Kanjur Marg (E), Mumbai, Maharashtra, India; all Indian Nationals
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 metal treatment.
Particularly, this invention relates to steel treatment.
More particularly, this invention relates to a manufacturing process of stampings using semi-processed electrical steel grade.
Background of the Invention:
Motors are machines that convert electrical energy to mechanical energy. The main components of a motor are stator and rotor. The Rotor is a rotating part of the motor while the stator is the stationary part of the motor
Stampings are used in the manufacture of stator as well as rotor of motor or other electrical or rotary machine equipment. Stampings are typically made of electrical steel.
Electrical steel which is also known as lamination steel, silicon steel or transformer steel is a sub-group of magnetic material family which is being used in the electric products like transformers, motors, generators, pumps etc. as a core material.
The good magnetic properties like lower core loss, higher saturation flux density, lower coercivity and high permeability of electrical steel grade makes it a suitable candidate for the use as core material in transformers or motors. The core loss of

the electrical steel being the most important parameter for its suitability as a core material needs to be controlled precisely.
The core loss is of three basic types:
(1) Hysteresis loss;
(2) Eddy current loss; and
(3) Anomalous losses.
The hysteresis loss contributes to approximately 70% of the total core loss and the remaining 30% is the Eddy current loss and anomalous loss. The hysteresis loss generally depends upon chemical composition, microstructure, stress level in material, inclusion content and bulk texture. Eddy current loss depends upon the lamination thickness, insulation resistance of the coating and grain size of the material.
The two basic types of electrical steel are: (1) Cold Rolled Grain Oriented (CRGO); and (2) Cold Rolled Non Oriented (CRNO) steel depending up on the orientation texture associated with them. Generally, CRGO type of steel is used where a linear magnetic flux is needed (e.g. transformers) and CRNO type of material is used where a rotating type of magnetic flux is needed (e.g. motors).
CRNO electrical steel has two basic types depending on their supply condition of heat treatment: (1) fully processed; and (2) semi processed electrical steels. Fully processed steels are those for which decarburizing annealing is done at supplier's end. Fully processed steels are further coated with organic or inorganic coating and hence, there is no need of any further heat treatment at stamping manufacturers'

end. Semi-processed steels are those for which the last operation carried out is normally a skin pass rolling and farther heat treatment is carried out at stamping manufacturer's end. The semi-processed steels are also known as cold rolled motor lamination (CRML) steel.
Semi processed electrical steel grades are vastly being used for motor applications. Various annealing treatments are being performed on the semi processed electrical steel grades in order to reduce the core loss of the laminations. In order to maintain the lower core loss, the lamination thickness needs to be as low as possible without hampering the punchability of the sheets. However, lower sheet thickness always comes with higher raw material cost due to extra rolling operations of the sheets which are critical to perform.
Commercially abundant available steel sheet thicknesses are 0.5mm and 0.65mm. Typically used steel sheet thickness by stamping manufacturer is 0.5mm which costs more than that of 0.65mm semi processed grade of electrical steel due to the reason mentioned above. An attempt to increase steel sheet thickness generally results in increased core loss laminations and thereby stator packs. The increased core loss of the stator/rotor pack due to increased lamination thickness results in lower efficiencies of motors and higher motor temperature while in application.
Prior Art:
US2011016701 relates to Production method for insulation stator. JP10066283 discloses a Manufacture of laminated stator in synchronous motor. GB1477005 relates to Manufacture of laminated stator in synchronous motor.

There is no prior art disclosure for semi-processed steel grade laminations of 0.65mm thickness.
Objects of the Invention:
An object of the invention is to provide a heat treatment method for metal treatment.
Another object of the invention is to provide a heat treatment method for semi-processed electrical steel grade.
Yet another object of the invention is to provide a heat treatment method for semi-processed electrical steel grade with 0.65 mm thickness.
Still another object of the invention is to provide a low cost stator/rotor manufacturing process (using CRML steel grade) without compromising on magnetic properties of the stator pack.
An additional object of the invention is to provide a steel sheet with thickness of 0.65mm for stamping operation in order to manufacture stator/rotor pack.
Yet an additional object of the invention is to develop a new type of heat treatment for 0.65mm thick electrical steel motor laminations so as to match the magnetic properties with that of 0.5mm thick steel.

Still an additional object of the invention is to obtain a matching efficiency and temperature rise of the electric motor when in application by using an increased thickness motor lamination and a new method of heat treatment at stamping manufacturer end.
Another additional object of the invention is to reduce raw material cost for manufacturing electrical or rotary machines.
Yet another additional object of the invention is to reduce processing time for manufacturing electrical or rotary machines.
Summary of the Invention:
According to this invention, there is provided a heat treatment method for metal laminations, said method comprises the steps of:
a. first step of heating said metal laminations up to temperatures ranging from
550°C to 700°C;
b. second step of soaking said heated metal lamination at the temperatures
ranging from 550°C to 700°C for durations ranging from 90 minutes to 120
minutes;
c. third step of cooling said heated and soaked metal lamination up to
temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled metal lamination for a duration
ranging from 10 minutes to 30 minutes time duration; and
e. fifth step of further cooling said steam blown metal lamination to room
temperature or less than 300°C.

According to this invention, there is provided a manufacturing process of stampings of semi-processed electrical steel grade of 0.65 mm thickness, said process comprising the step of heat treating said stampings of semi-processed electrical steel grade of 0.65 mm thickness, said process comprises the steps of:
a. first step of heating 0.65mm semi-processed steel lamination up to
temperatures ranging from 550°C to 700°C;
b. second step of soaking said heated semi-processed steel lamination at the
temperatures ranging from 550°C to 700°C for durations ranging from 90
minutes to 120 minutes;
c. third step of cooling the soaked and heated semi-processed steel lamination
up to temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled semi-processed steel
lamination for a duration ranging from 10 minutes to 30 minutes time
duration; and
e. fifth step of further cooling the steam blown semi-processed steel lamination
to room temperature or less than 300°C.
Typically, each of said steps is a step performed in a furnace.
According to this invention, there is provided a 0.65mm stamping of semi-processed electrical steel grade manufactured with an improved heat treatment process, said process comprises the steps of: a. first step of heating 0.65mm semi-processed steel lamination up to temperatures ranging from 550°C to 700°C;

b. second step of soaking said heated semi-processed steel lamination at the
temperatures ranging from 550°C to 700°C for durations ranging from 90
minutes to 120 minutes;
c. third step of cooling the soaked and heated semi-processed steel lamination up
to temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled semi-processed steel lamination
for a duration ranging from 10 minutes to 30 minutes time duration; and
e. fifth step of further cooling the steam blown semi-processed steel lamination
to room temperature or less than 300°C.
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 process of the invention.
Detailed Description of the Accompanying Drawings:
According to this invention, there is provided a manufacturing process of stampings using semi-processed electrical steel grade of 0.65mm thickness and there is provided a 0.65mm thickness semi-processed electrical steel grade stamping manufactured with an improved heat treatment process.
The stamping manufacturing process, according to this invention, is typically directed towards steel sheet laminations of relatively higher thickness (0.65mm)

for stamping operation. The heat treatment process is applied in order to reduce core loss of the selected steel laminations.
Heat treatment of 0.65mm thick laminations involves relatively higher temperatures than that of 0.5mm thick laminations.
In accordance with an embodiment of this invention, there process involves a first step of heating 0.65mm semi-processed steel lamination up to temperatures ranging from about 550°C to 700°C.
In accordance with another embodiment of this invention, the process involves a second step of soaking said heated semi-processed steel lamination at the
temperatures ranging from about 550°C to 700°C for durations ranging from about
90 minutes to 120 minutes.
In accordance with another embodiment of this invention, the process involves a third step of cooling the soaked and heated semi-processed steel lamination up to temperatures ranging from about 400°C to 550°C.
In accordance with another embodiment of this invention, the process involves a fourth step of blowing steam over the cooled semi-processed steel lamination for a duration ranging from about 10 minutes to 30 minutes time duration.
In accordance with another embodiment of this invention, the process involves a fifth step of further cooling the steam blown semi-brocessed steel lamination to room temperature or less than 300°C.

All the above steps are carried out, typically, in a furnace. There is no need of controlled furnace atmosphere up to 600°C, but holding above 600°C temperatures requires inert or reducing atmosphere control.
This process is suitable for manufacturing of motor laminations which can be used for various applications like motors, fans, pumps and the like electrical and rotary machines.
The use of 0.65mm laminations (as opposed to 0.5mm laminations) results in lower raw material cost, lower stamping manufacturing time, higher productivity and better mechanical stability of the motor laminations without compromising on the magnetic properties of the laminations and motor performance. For a given height, lesser number of 0.65mm laminations shall be used as compared to 0.5mm laminations; hence the reduction in raw material cost.
Further, 0.5mm thick laminations when replaced by 0.65mm thick laminations will result in decreased number of stampings for the same core length, which will lead to decreased number of stamping strokes resulting in lowering of process time by 30% for the stator/rotor pack; therefore an increase in productivity by almost 30%.
Improvement in sheet mechanical properties due to higher sheet thickness will result in better stability of motor laminations.
The process maintains magnetic properties of motor laminations in stator/rotor form in spite of using higher sheet thickness of 0.65mm for motor laminations

against conventional sheet thickness of 0.5mm. The process maintains the motor performance. The process maintains mechanical stability of stator/rotor packs.
According to an exemplary embodiment of the process of this invention, defined parameters of a motor (no load) with 0.5 mm steel sheet stampings were tested vis-a-vis defined parameters of a motor (no load) with 0.65 mm steel sheet stampings incorporating the heat treatment process of this invention. Further, defined parameters of a motor (full load) with 0.5 mm steel sheet stampings were tested vis-a-vis defined parameters of a motor (full load) with 0.65 mm steel sheet stampings incorporating the heat treatment process of this invention. The test parameters were as follows: i. Test Voltage = 220V ii. Test Frequency = 50 Hz iii. Torque = 51 N-m
Table 1 illustrates motor performance results comparison between motor manufactured by conventional process and motors manufactured by the process of this invention.

Motor No Lamination thickness = 0.5 conventional process mm, by Lamination thickness = 0.65 manufacturing process mm, by invented

1 2 3 4 1 2 3 4 5
Current-A 2.52 2.8 2.72 2.32 2.24 2.2 2.2 2.48 2.32
Power-W 268 276 264 280 256 256 256 260 256
Voltage-
V 323 334 325 323 325 326 333 326 329
R?M 1496 1498 1496 1496 1496 1495 1496 1495 1496

Current-A
4.6 5 4.8 4.8 4.6 4.6 4.4 4.6 4.4
Power-W 1040 1060 1040 1060 1020 1020 1000 1020 1000
Voltage-V 293 297 300 292 293 294 297 297 295
RPM 1445 1442 1441 1438 1440 1442 1442 1444 1445
Output
power
(W) 756.11 754.54 754.02 752.45 753.49 754.54 754.54 755.59 756.11
Efficiency (%) 72.70 71.78 72.50 70.99 73.87 73.97 75.45 74.08 75.61
It can be seen from the table 1 of motor performance testing results that, the motor efficiencies with the newly developed low cost manufacturing process are similar with that of the motor using manufacturing process of the prior art.
According to another exemplary embodiment of the process of this invention, defined parameters of a motor manufactured using laminations of 0.5mm were tested vis-a-vis defined parameters of a motor manufactured using laminations of 0.65 mm at various levels of voltage (190 V, 225 V 240V) to record and compare temperature rise. This is seen in Table 2.

Voltage (V) 190 225 240
Lamination Thickness (mm) 0.65 (new) 0.5 (Conventional) 0.65 (new) 0.5
(Conventional) 0.65 (new) 0.5 (Conventional)
Temp Rise MW 82.04 95.97 77.03 92.9 83.61 97.27

Temp Rise AW 77.38 89.15 75.09 87.93 77.38 94.95
Max. Body Temp. 80.5 92 81.5 97 85 100.5
It was seen that the winding temperatures and motor body temperatures were well within the limits for the stampings manufactured by low cost process of this invention which used 0.65mm thick sheets of semiprocessed grade of electrical steel with modified heat treatment cycle.
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 heat treatment method for metal lamination treatment, said method comprising the steps of:
a. first step of heating said metal lamination up to temperatures ranging from
550°Cto700°C;
b. second step of soaking said heated metal lamination at the temperatures
ranging from 550°C to 700°C for durations ranging from 90 minutes to 120
minutes;.
c. third step of cooling said soaked and heated metal lamination up to
temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled metal lamination for a duration
ranging from 10 minutes to 30 minutes time duration; and
e. fifth step of further cooling said steam blown metal lamination to room
temperature or less than 300°C.
2, A process as claimed in claim 1 wherein, each of said steps is a step performed
in a furnace.
3. A manufacturing process of stampings of semi-processed electrical steel grade
of 0.65 mm thickness, said process comprising the step of heat treating said
stampings of semi-processed electrical steel grade of 0.65 mm thickness, said
process comprising the steps of:
a. first step of heating 0.65mm semi-processed steel lamination up to temperatures ranging from 550°C to 700°C;

b. second step of soaking said heated semi-processed steel lamination at the
temperatures ranging from 550°C to 700°C for durations ranging from 90
minutes to 120 minutes;
c. third step of cooling the soaked and heated semi-processed steel lamination
up to temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled semi-processed steel
lamination for a duration ranging from 10 minutes to 30 minutes time
duration; and
e. fifth step of further cooling the steam blown semi-processed steel lamination
to room temperature or less than 300°C.
4. A process as claimed in claim 1 wherein, each of said steps is a step performed in a furnace.
5. A 0.65mm stamping of semi-processed electrical steel grade manufactured with an improved heat treatment process, said process comprising the steps of:
a. first step of heating 0.65mm semi-processed steel lamination up to
temperatures ranging from 550°C to 700°C;
b. second step of soaking said heated semi-processed steel lamination at the
temperatures ranging from 550°C to 700°C for durations ranging from 90
minutes to 120 minutes;
c. third step of cooling the soaked and heated semi-processed steel lamination
up to temperatures ranging from 400°C to 550°C;
d. fourth step of blowing steam over the cooled semi-processed steel
lamination for a duration ranging from 10 minutes to 30 minutes time
duration; and

e. fifth step of further cooling the steam blown semi-processed steel lamination to room temperature or less than 300°C.