Claims:We claim:
1. A cold rolled electrical steel comprising:
a batch annealed, skin pass rolled composition in weight % with no decarburization annealing having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities.

2. The cold rolled electrical steel as claimed in claim 1, wherein said electrical steel is stamped or punched to form silicon killed low carbon cold rolled electrical lamination sheets or strips.

3. The cold rolled electrical steel as claimed in claims 1 or 2, wherein said electrical steel has a yield strength of 180-250 MPa, tensile strength of 280-380 MPa, total elongation of 25%– 35%, and core loss of 10-15 W/kg.

4. The cold rolled electrical steel as claimed in any one of the preceding claims 1-3, wherein said electrical steel is batch annealed at 600 - 700°C in a hydrogen atmosphere with an annealing time 22-32 hrs and skin passing rolled at a room temperature with 1 to 2% deformation.

5. The cold rolled electrical steel as claimed in any one of the preceding claims 1-4, wherein said electrical steel has ferrite grains with uniform sizes of the order ASTM number 9-10 and ASTM 6-7.

6. The cold rolled electrical steel as claimed in any one of the preceding claims 1-5, wherein said grains have equiaxed and polygonal shape for said annealing time of 26 hours.

7. The cold rolled electrical steel as claimed in any one of the preceding claims 1-6, wherein said grains are pancaked for said annealing time of 32 hours.

8. A method of manufacturing a cold rolled electrical steel, the method comprising the steps of:
processing heat from an oxygen furnace, ladle refining without vacuum degassing and continuously casting an electrical steel having a liquid steel composition in weight % having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities to form slabs of thickness 34 mm;
charging and reheating said slabs in a reheating furnace steel composition at a temperature in the range of 1200°C to 1250°C;
rough hot rolling of said reheated slab in a roughing mill at a delivery temperature of 1080°C - 1100°C to form a hot rolled slab of thickness 2.7 mm;
finish rolling said rough hot rolled slabs in a finish mill at an exit temperature of 800 °C - 900°C;
coiling said finish rolled steel at a coiling temperature less than 600°C-700°C;
acid pickling and cold rolling said hot rolled steel coils to a thickness of 0.5 mm with cold reduction of 75-85%;
batch annealing of said cold rolled steel coils in a 95% hydrogen atmosphere at a temperature of 600°C-700°C with an annealing time of 22-32 hours; and
passing said cold rolled steel coils at room temperature for skin pass rolling having 1 to 2% deformation, thereby forming silicon killed low carbon cold rolled electrical steel directly for stamping applications with no decarburization annealing.
Dated this 29th day of March, 2022
For STEEL AUTHORITY OF INDIA LIMITED
By their Agent

(ANSHUL SUNILKUMAR SAURASTRI) (IN/PA 3086)
KRISHNA & SAURASTRI ASSOCIATES LLP
, Description:
FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[SEE SECTION 10, RULE 13]

COLD ROLLED ELECTRICAL STEEL;

STEEL AUTHORITY OF INDIA LIMITED, A GOVERNMENT OF INDIA ENTERPRISE, HAVING ITS ADDRESS AT RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA, RANCHI-834002, STATE OF JHARKHAND, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
TECHNICAL FIELD
[001] The present invention relates to cold rolled electrical steels and a method of manufacturing the same for electrical stamping applications.

BACKGROUND
[002] Generally, steel used for electrical applications require to have good magnetic properties. The steel must be easy to magnetize and demagnetize. When a steel core is magnetized and then magnetized two types of losses namely eddy current loss and hysteresis loss occur. Electrical steels used in manufacturing of iron cores that have applications in motors, transformers and generators. The iron cores aid in concentrating a magnetic field and making an electromagnet stronger. Electrical steels are commonly used in such electrical application are designed to reduce said eddy current hysteresis losses as such electrical steel have high permeability i.e., electrical current required to produce magnetism is low. Electrical steels are commonly of two types i.e., grain oriented and non-oriented electrical steels. The grain oriented electrical steels have a symmetrical structure in which cubic crystals are all arranged in the direction in which the steel plate has been rolled and is commonly called as GOSS orientation. Such grain-oriented steels have good power and permeability properties in the direction of rolling when compared to the properties it has at 90 ° to said direction. The non-oriented electrical steels have similar magnetic properties in all directions as the cubic crystals that make up grain structure are randomly oriented. Grain oriented steels have applications in transformers, transducers, and magnetic amplifier cores. Non-oriented steels have applications in rotating machines such as motors, generators and alternators.
[003] Although, such electrical steels have said good permeability properties, they suffer from inherent limitation of high cost, inhibiting their application in small and medium sized rotors, stators, motors and small power transformers steel strips and sheets. Such electrical steel also if used in said small applications at such high cost suffers from the limitations of decarburization annealing requirement after processing of the electrical steel with high cost, low punching/stamping properties.
[004] Therefore, there is a need for a solution for an electrical steel to address and overcome one or more problems of the prior art.

SUMMARY
[005] This summary is provided to introduce concepts related to cold rolled electrical steel and a method of manufacturing the same. This summary is neither intended to identify essential features of the present invention nor is it intended for use in determining or limiting the scope of the present invention.
[006] Accordingly, an aspect of the present invention discloses a cold rolled electrical steel comprising: a batch annealed, skin pass rolled composition in weight % with no decarburisation annealing having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities.
[007] According to another aspect, the present invention discloses a method of manufacturing a cold rolled electrical steel, the method comprising the steps of: processing heat from an oxygen furnace, ladle refining without vacuum degassing and continuously casting an electrical steel having a liquid steel composition in weight % having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities to form slabs of thickness 34 mm;charging and reheating said slabs in a reheating furnace having said liquid steel composition at a temperature in the range of 1200°C to 1250°C; rough hot rolling of said reheated slab in a roughing mill at a delivery temperature of 1080°C - 1100°C to form a hot rolled slab of thickness 2.7 mm;finish rolling said rough hot rolled slabs in a finish mill at an exit temperature of 800 °C - 900°C;coiling said finish rolled steel at a coiling temperature less than 600°C-700°C;acid pickling and cold rolling said hot rolled steel coils to a thickness of 0.5 mm with cold reduction of 75-85%;batch annealing of said cold rolled steel coils in a 95% hydrogen atmosphere at a temperature of 600°C-700°C with an annealing time of 22-32 hours; andskin passing with no decarburization annealing, said cold rolled steel coils at room temperature with temper rolling having 1 to 2% deformation, thereby forming silicon killed low carbon cold rolled electrical steel.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[008] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
[009] Figure 1illustrates an optical micrograph of Silicon killed low carbon forming quality cold rolled electrical steel grade.
[0010] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
[0011] In the following description, for the purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present inventionmay be practiced without these specific details. In other instances, well-known structures are shown in diagram form to facilitate describing the invention. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into several applications.
[0012] In general, the present invention claims a cold rolled electrical steel comprising a batch annealed, skin pass rolled composition in weight % with no decarburization annealing having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities.
[0013] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiment illustrated.Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
[0014] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein may be made without departing from the scope of the invention.
[0015] Referring figure 1, according toan aspect of the present invention discloses a cold rolled electrical steel comprising:a batch annealed, skin pass rolled composition in weight % with no decarburization annealing having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities.
[0016] According to an embodiment, said electrical steel is stamped or punched to form silicon killed low carbon cold rolled electrical lamination sheets or strips.
[0017] According to the embodiment, said electrical steel has a yield strength of 180-250 MPa, tensile strength of 280-380 MPa, total elongation of 25%– 35%, and core loss of 10-15 W/kg.
[0018] According to the embodiment, said electrical steel is batch annealed at 600 - 700°C in a hydrogen atmosphere with an annealing time 22-32 hrs and skin passing rolled at a room temperature with 1 to 2% deformation.
[0019] According to the embodiment, said electrical steel has ferrite grains with uniform sizes of the order ASTM number 9-10 and ASTM 6-7.
[0020] According to the embodiment, said grains have equiaxed and polygonal shape for said annealing time of 26 hours.
[0021] According to the embodiment, said grains are pancaked for said annealing time of 32 hours.
[0022] According to another aspect, the present invention discloses a method of manufacturing a cold rolled electrical steel, the method comprising the steps of: processing heat from an oxygen furnace, ladle refining without vacuum degassing and continuously casting an electrical steel having a liquid steel composition in weight % having carbon in a content of 0.02- 0.10 %, manganese in a content of 0.20-0.30%, silicon in a content of 0.15-0.30%, aluminium in a content of 0.005-0.01%, phosphorous in a content of at most 0.020 %, Sulphur in content of at most 0.02 % or less, remaining weight % containing Fe and unavoidable impurities to form slabs of thickness 34 mm;charging and reheating said slabs in a reheating furnace having said liquid steel composition at a temperature in the range of 1200°C to 1250°C; rough hot rolling of said reheated slab in a roughing mill at a delivery temperature of 1080°C - 1100°C to form a hot rolled slab of thickness 2.7 mm;finish rolling said rough hot rolled slabs in a finish mill at an exit temperature of 800 °C - 900°C;coiling said finish rolled steel at a coiling temperature less than 600°C-700°C;acid pickling and cold rolling said hot rolled steel coils to a thickness of 0.5 mm with cold reduction of 75-85%;batch annealing of said cold rolled steel coils in a 95% hydrogen atmosphere at a temperature of 600°C-700°C with an annealing time of 22-32 hours; and skin passing with no decarburization annealing, said cold rolled steel coils at room temperature with temper rolling having 1 to 2% deformation, thereby forming silicon killed low carbon cold rolled electrical steel.
[0023] Referring figure 1, illustrates the optical micrograph of Silicon killed low carbon forming quality cold rolled electrical steel grade. According to an embodiment, referring figure 1, illustrates microstructure (100) of the silicon killed low carbon forming quality cold rolled steel coils after cold-rolling, batch-annealing and skin passing after annealing time of 26 and 32 hrs. The steel predominantly comprises ferrite grains with uniform sizes of the order ASTM number 9-10 and ASTM 6-7 for annealing time of 26 and 32 hrs with annealing temperature range 600 – 700 0C. The grains were equiaxed and polygonal shape (110) for Silicon killed low carbon forming quality cold rolled steel for 26 hrs and pancaked grains (120) were clearly for annealing time of 32 hrs. The control of process parameters during the entire process contributes to an optimum microstructure, resulting into an excellent combination of mechanical properties.
[0024] According to the present invention, it is aimed to develop steel for smaller and medium sized motors with moderate core loss and good punching/stamping properties without decarburisation annealing by selecting a suitable chemistry and process parameters. Domestic appliances are dominated by low-cost universal and induction motors, with efficiencies of 60–70%. Silicon killed low carbon forming quality cold rolled steel can be used effectively to make such lamination cores of fractional horsepower motors for economic reasons.
[0025] According to an embodiment, a method of manufacturing cold rolled electrical steels having the step of wherein steel is continuously cast and a transfer bar having a thickness of 34 mm is charged in reheating furnace and hot rolled to 2.7 mm. The finishing temperatures varies in the range of 8000C-9000C while the coiling temperatures varies between 6000C and 7000C. The coils are then cold rolled to 0.5 mm thickness with 65%-85% reduction. After cold rolling, the steel sheets are batch annealed at 600 - 700°C followed by appropriate amount of temper rolling (1-2%). The mechanical and magnetic properties of low-Si electrical steels are shown in the following Table 1.
Table 1: Mechanical and magnetic properties of silicon killed low carbon forming quality cold rolled steel coils steel:

Grade YS in MPa UTS in Mpa % EL Core loss value (W/Kg)
Cold rolled 180 -210 280-380 25%– 35% 10-12

[0026] According to the present invention, the core loss of value of electrical steel grade of the present invention is superior to semi- processed electrical steels and also the processing cost of decarburization annealing is reduced as cold rolled low-Si electrical steels need no further processing after skin pass rolling.
[0027] There have been described and illustrated herein several embodiments of exemplary indicative implementation of cold rolled electrical steels. It will be also apparent to a skilled person that the embodiments described above are specific examples of a single broader invention, which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the description without departing from the scope of the invention. Thus, while particular structure specific type of arrangement of elements, type of configurations, numbers, have been disclosed, it will be appreciated that the embodiments may be manufactured with other design parameters and configurations as well. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” is used as the plain-English equivalent of the respective term “comprising” respectively.