Title of Invention	BATCH PROCESS FOR PRODUCING NON-ORIENTED ELECTRICAL STEEL SHEET IN TWO STAGE COOLING
Abstract	A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820ºC in a nitrogen and hydrogen gas atmosphere. The sheet is decarburised by holding the temperature at 750-820ºC and then cooled to a temperature of 650-720ºC in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooled to a temperature of 300-400ºC in the absence of carbon monoxide.

Title of Invention

BATCH PROCESS FOR PRODUCING NON-ORIENTED ELECTRICAL STEEL SHEET IN TWO STAGE COOLING

Abstract

A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820ºC in a nitrogen and hydrogen gas atmosphere. The sheet is decarburised by holding the temperature at 750-820ºC and then cooled to a temperature of 650-720ºC in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooled to a temperature of 300-400ºC in the absence of carbon monoxide.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) As amended by the Patents (Amendment) Act, 2005 & The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2005 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION Batch process for producing non-oriented electrical steel sheet INVENTORS Names: Ingle Asha, Singal Vivek and Joshi Sachin Nationality: all Indian Nationals Address: Crompton Greaves Limited, Materials and Process Center, Kanjur Marg (E), Mumbai 400042, Maharashtra, India APPLICANTS Name : CROMPTON GREAVES LIMITED Nationality: Indian Company Address : CG House, Dr Annie Besant Road, Prabhadevi, Mumbai 400025, Maharashtra, India 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 INVENTION This invention relates to a batch process for producing non-oriented electrical steel sheet. This invention also relates to non-oriented electrical steel sheet produced by the batch process. BACKGROUND OF INVENTION Non-oriented electrical steel sheets i.e. steel sheets in which magnetic properties are uniform in any plane, are generally used in electrical applications like electric motors or magnetic circuits. Non-oriented electrical steel sheets are produced by the batch process comprising the steps of casting molten steel comprising carbon, silicon, aluminum, phosphorous, manganese, iron and other unavoidable impurities such as sulphur into slabs; hot rolling the slabs into sheets; cold rolling the sheets to even thickness; subjecting the sheets to recrystallisation annealing to allow new bonds to be formed between the grains thereof; skin pass rolling the recrystallised steel sheets for orienting the grains thereof followed by grain growth annealing of the rolled steel sheets to remove or decarburize the remaining carbon in the 2 sheets and to develop magnetic properties/Prior to grain growth annealing, the steel sheets may be, if required, cut or punched out into laminations. Grain growth annealing of the steel sheets is carried out in a batch type slow cooling furnace in a nitrogen and hydrogen gas atmosphere by heating them to temperatures of 750-820°C. The sheets are allowed to decarburise by holding the temperature at 750-820°C and then cooled to 300-400°C. One way to obtain electrical steel sheets having low core loss is to have phosphorus content in the steel higher than 0.035%. Due to slow cooling during annealing, the phosphorous tends to segregate at the grain boundaries thereby imparting brittleness to the sheets. To avoid brittleness and improve ductility of the sheets it is known to cool the steel sheets in the furnace at a faster rate to prevent segregation of phosphorous at the grain boundaries. This, however, requires modifications in the configuration of the batch type furnace in the form of additional cooling arrangements which increase the cost of the furnace. During fast cooling there are chances of magnetic properties being not properly developed in the steel sheets thereby resulting in steel sheets with low magnetic properties. 3 OBJECTS OF INVENTION An object of the invention is to provide a batch process for producing non-oriented electrical steel sheet, which process produces steel sheet having improved ductility and good magnetic properties like low core loss and good permeability. Another object of the invention is to provide a batch process for producing non-oriented electrical steel, which process does not require any change in the configuration of the batch type furnace for grain growth annealing of the rolled steel sheet in the form of additional cooling arrangements thereby reducing cost. Another object of the invention is to provide a batch process for producing non-oriented electrical steel sheet, which process does not require fast cooling of the steel sheet during grain growth annealing thereby allowing magnetic properties to be properly developed in the steel sheet. Another object of the invention is to provide non-oriented electrical steel sheet having improved ductility and good magnetic properties like low core loss and good permeability: 4 DETAILED DESCRIPTION OF INVENTION According to the invention there is provided a batch process for producing non-oriented electrical steel comprising the, step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere, decarburizing the sheet by holding the temperature at 750-820°C, cooling the steel sheet to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooling the steel sheet to a temperature of 300-400°C in the absence of carbon monoxide. Preferably, the steel sheet is heated to and decarburized at 780°C, cooled to 700°C in the presence of carbon monoxide gas and further cooled to 370°C in the absence of carbon monoxide gas., Preferably the carbon monoxide gas is generated by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 1000°C. 5 According to the invention there is also provided non-oriented electrical steel sheet manufactured by the batch process described above. According to the invention during grain growth annealing of the rolled steel sheets in the batch type slow type furnace, cooling of the sheets is carried out in two stages. Firstly, to 650 - 720°C in the presence of carbon monoxide gas and then to 300 - 400°C in the absence of carbon monoxide gas. It is observed that sheets of reduced brittleness and increased ductility are obtained by the process of the invention. It is believed that during cooling in the presence of carbon monoxide gas the carbon atoms occupy the grain boundary sites and prevent the segregation of phosphorous at the grain boundaries thereby reducing brittleness and improving ductility of the sheets. Due to elimination of fast cooling of the sheets, magnetic properties are properly developed in the sheets. Besides, the batch furnace does not require any change in its configuration in the form of additional cooling arrangements thereby reducing cost. Carbon monoxide gas is preferably generated on site by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 950°C. This works out to be cheaper as compared to transporting carbon monoxide gas in cylinders to the site thereby rendering the process further economical. It is, however, understood 6 that carbon monoxide gas in cylinders also can be used in the process of the invention. The following experimental example is illustrative of the invention but not limitative of the scope thereof: EXAMPLE 1 A rolled steel sheet produced from molten steel comprising 0.009% by weight of carbon, 1.2% by weight of silicon, 0.25% by weight of aluminum, 0.07% by weight of phosphorous, 0.22 % by weight of manganese and iron and other unavoidable impurities such as sulphur was grain growth annealed in a batch type slow burning furnace of 1 ton capacity by heating the sheet to a temperature of 780°C in a nitrogen and hydrogen gas atmosphere. The sheet was decarburised by holding the temperature at 780°C for 2.5hrs. The sheet was cooled to a temperature of 700°C in the presence of nitrogen and hydrogen and carbon monoxide gas in 1 hr. The carbon monoxide gas was generated by passing carbon dioxide gas through another furnace on site containing a charcoal bed at 920°C. The steel sheet was further cooled down to 370°C in 2.5 hrs in the absence of carbon monoxide gas. The mechanical 7 and magnetic properties of the sheet were measured and were found to be as under: Brittleness as measured by bend test at 180° - 45 bends Core loss as per Epstein Square test and measured by core loss tester - 4 W/kg Permeability as per Epstein Square test and measured by core loss tester -3400 Phosphorous content as measured by spectrometer - 0.07% The experimental results show that the non-oriented electrical steel sheet had reduced brittleness and improved ductility. Magnetic properties such as core loss and permeability of the steel sheet were also properly developed and the phosphorous content remained high. 8 We claim: 1. A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere, decarburizing the sheet by holding the temperature at 750-820°C, cooling the steel sheet to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooling the steel sheet to a temperature of 300-400°C in the absence of carbon monoxide. 2. A process as claimed in claim 1, wherein the steel sheet is heated to and decarburized at 780°C, cooled to 700°C in the presence of carbon monoxide gas and further cooled to 370°C in the absence of carbon monoxide gas. 3. A process as claimed in claim 1 or 2, wherein the carbon monoxide gas is generated by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 1000°C. 9 4. Non-oriented electrical steel sheet manufactured by the process as claimed in anyone of claims 1 to 3. 10 ABSTRACT A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere. The sheet is decarburised by holding the temperature at 750-820°C and then cooled to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further copied to a temperature of 300-400°C in the absence of carbon monoxide.

Full Text

FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
Batch process for producing non-oriented electrical steel sheet
INVENTORS
Names: Ingle Asha, Singal Vivek and Joshi Sachin Nationality: all Indian Nationals
Address: Crompton Greaves Limited, Materials and Process Center, Kanjur Marg (E), Mumbai 400042, Maharashtra, India
APPLICANTS
Name : CROMPTON GREAVES LIMITED
Nationality: Indian Company
Address : CG House, Dr Annie Besant Road, Prabhadevi, Mumbai 400025, Maharashtra, India
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 INVENTION
This invention relates to a batch process for producing non-oriented electrical steel sheet.
This invention also relates to non-oriented electrical steel sheet produced by the batch process.
BACKGROUND OF INVENTION
Non-oriented electrical steel sheets i.e. steel sheets in which magnetic properties are uniform in any plane, are generally used in electrical applications like electric motors or magnetic circuits. Non-oriented electrical steel sheets are produced by the batch process comprising the steps of casting molten steel comprising carbon, silicon, aluminum, phosphorous, manganese, iron and other unavoidable impurities such as sulphur into slabs; hot rolling the slabs into sheets; cold rolling the sheets to even thickness; subjecting the sheets to recrystallisation annealing to allow new bonds to be formed between the grains thereof; skin pass rolling the recrystallised steel sheets for orienting the grains thereof followed by grain growth annealing of the rolled steel sheets to remove or decarburize the remaining carbon in the
2

sheets and to develop magnetic properties/Prior to grain growth annealing, the steel sheets may be, if required, cut or punched out into laminations. Grain growth annealing of the steel sheets is carried out in a batch type slow cooling furnace in a nitrogen and hydrogen gas atmosphere by heating them to temperatures of 750-820°C. The sheets are allowed to decarburise by holding the temperature at 750-820°C and then cooled to 300-400°C. One way to obtain electrical steel sheets having low core loss is to have phosphorus content in the steel higher than 0.035%. Due to slow cooling during annealing, the phosphorous tends to segregate at the grain boundaries thereby imparting brittleness to the sheets. To avoid brittleness and improve ductility of the sheets it is known to cool the steel sheets in the furnace at a faster rate to prevent segregation of phosphorous at the grain boundaries. This, however, requires modifications in the configuration of the batch type furnace in the form of additional cooling arrangements which increase the cost of the furnace. During fast cooling there are chances of magnetic properties being not properly developed in the steel sheets thereby resulting in steel sheets with low magnetic properties.
3

OBJECTS OF INVENTION
An object of the invention is to provide a batch process for producing non-oriented electrical steel sheet, which process produces steel sheet having improved ductility and good magnetic properties like low core loss and good permeability.
Another object of the invention is to provide a batch process for producing non-oriented electrical steel, which process does not require any change in the configuration of the batch type furnace for grain growth annealing of the rolled steel sheet in the form of additional cooling arrangements thereby reducing cost.
Another object of the invention is to provide a batch process for producing non-oriented electrical steel sheet, which process does not require fast cooling of the steel sheet during grain growth annealing thereby allowing magnetic properties to be properly developed in the steel sheet.
Another object of the invention is to provide non-oriented electrical steel sheet having improved ductility and good magnetic properties like low core loss and good permeability:
4

DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a batch process for producing non-oriented electrical steel comprising the, step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere, decarburizing the sheet by holding the temperature at 750-820°C, cooling the steel sheet to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooling the steel sheet to a temperature of 300-400°C in the absence of carbon monoxide.
Preferably, the steel sheet is heated to and decarburized at 780°C, cooled to 700°C in the presence of carbon monoxide gas and further cooled to 370°C in the absence of carbon monoxide gas.,
Preferably the carbon monoxide gas is generated by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 1000°C.
5

According to the invention there is also provided non-oriented electrical steel sheet manufactured by the batch process described above.
According to the invention during grain growth annealing of the rolled steel sheets in the batch type slow type furnace, cooling of the sheets is carried out in two stages. Firstly, to 650 - 720°C in the presence of carbon monoxide gas and then to 300 - 400°C in the absence of carbon monoxide gas. It is observed that sheets of reduced brittleness and increased ductility are obtained by the process of the invention. It is believed that during cooling in the presence of carbon monoxide gas the carbon atoms occupy the grain boundary sites and prevent the segregation of phosphorous at the grain boundaries thereby reducing brittleness and improving ductility of the sheets. Due to elimination of fast cooling of the sheets, magnetic properties are properly developed in the sheets. Besides, the batch furnace does not require any change in its configuration in the form of additional cooling arrangements thereby reducing cost. Carbon monoxide gas is preferably generated on site by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 950°C. This works out to be cheaper as compared to transporting carbon monoxide gas in cylinders to the site thereby rendering the process further economical. It is, however, understood
6

that carbon monoxide gas in cylinders also can be used in the process of the invention.
The following experimental example is illustrative of the invention but not limitative of the scope thereof:
EXAMPLE 1
A rolled steel sheet produced from molten steel comprising 0.009% by weight of carbon, 1.2% by weight of silicon, 0.25% by weight of aluminum, 0.07% by weight of phosphorous, 0.22 % by weight of manganese and iron and other unavoidable impurities such as sulphur was grain growth annealed in a batch type slow burning furnace of 1 ton capacity by heating the sheet to a temperature of 780°C in a nitrogen and hydrogen gas atmosphere. The sheet was decarburised by holding the temperature at 780°C for 2.5hrs. The sheet was cooled to a temperature of 700°C in the presence of nitrogen and hydrogen and carbon monoxide gas in 1 hr. The carbon monoxide gas was generated by passing carbon dioxide gas through another furnace on site containing a charcoal bed at 920°C. The steel sheet was further cooled down to 370°C in 2.5 hrs in the absence of carbon monoxide gas. The mechanical
7

and magnetic properties of the sheet were measured and were found to be as under:
Brittleness as measured by bend test at 180° - 45 bends
Core loss as per Epstein Square test and measured by core loss tester - 4 W/kg
Permeability as per Epstein Square test and measured by core loss tester -3400
Phosphorous content as measured by spectrometer - 0.07%
The experimental results show that the non-oriented electrical steel sheet had reduced brittleness and improved ductility. Magnetic properties such as core loss and permeability of the steel sheet were also properly developed and the phosphorous content remained high.
8

We claim:
1. A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere, decarburizing the sheet by holding the temperature at 750-820°C, cooling the steel sheet to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further cooling the steel sheet to a temperature of 300-400°C in the absence of carbon monoxide.
2. A process as claimed in claim 1, wherein the steel sheet is heated to and decarburized at 780°C, cooled to 700°C in the presence of carbon monoxide gas and further cooled to 370°C in the absence of carbon monoxide gas.
3. A process as claimed in claim 1 or 2, wherein the carbon monoxide gas is generated by passing carbon dioxide gas through another furnace containing a charcoal bed at 900 to 1000°C.
9
4. Non-oriented electrical steel sheet manufactured by the process as claimed in anyone of claims 1 to 3.
10

ABSTRACT
A batch process for producing non-oriented electrical steel comprising the step of grain growth annealing the rolled steel sheet in a batch type slow cooling furnace by heating the steel sheet to a temperature of 750-820°C in a nitrogen and hydrogen gas atmosphere. The sheet is decarburised by holding the temperature at 750-820°C and then cooled to a temperature of 650-720°C in the presence of nitrogen and hydrogen and carbon monoxide gas and further copied to a temperature of 300-400°C in the absence of carbon monoxide.

Documents:

691-MUM-2005-ABSTRACT(13-3-2014).pdf

691-MUM-2005-ABSTRACT(21-6-2011).pdf

691-mum-2005-abstract.doc

691-mum-2005-abstract.pdf

691-MUM-2005-CLAIMS(AMENDED)-(13-3-2014).pdf

691-MUM-2005-CLAIMS(AMENDED)-(21-6-2011).pdf

691-mum-2005-claims.doc

691-mum-2005-claims.pdf

691-mum-2005-correspondence others.pdf

691-mum-2005-correspondence received ver-01072005.pdf

691-MUM-2005-CORRESPONDENCE(04-06-2012).pdf

691-MUM-2005-CORRESPONDENCE(1-11-2013).pdf

691-MUM-2005-CORRESPONDENCE(12-10-2012).pdf

691-MUM-2005-CORRESPONDENCE(15-2-2013).pdf

691-MUM-2005-CORRESPONDENCE(21-6-2011).pdf

691-mum-2005-correspondence(23-4-2008).pdf

691-MUM-2005-CORRESPONDENCE(28-2-2014).pdf

691-MUM-2005-CORRESPONDENCE(3-10-2008).pdf

691-MUM-2005-CORRESPONDENCE(3-2-2012).pdf

691-MUM-2005-CORRESPONDENCE(4-10-2011).pdf

691-MUM-2005-CORRESPONDENCE(6-3-2009).pdf

691-MUM-2005-CORRESPONDENCE(9-10-2009).pdf

691-mum-2005-correspondence-received ver-08062005.pdf

691-mum-2005-description (complete).pdf

691-mum-2005-form 1(1-7-2005).pdf

691-MUM-2005-FORM 1(13-3-2014).pdf

691-MUM-2005-FORM 1(21-6-2011).pdf

691-MUM-2005-FORM 13(13-3-2014).pdf

691-mum-2005-form 13(21-6-2011).pdf

691-mum-2005-form 18(7-12-2007).pdf

691-MUM-2005-FORM 2(TITLE PAGE)-(13-3-2014).pdf

691-MUM-2005-FORM 2(TITLE PAGE)-(21-6-2011).pdf

691-mum-2005-form 2(title page)-(9-6-2005).pdf

691-MUM-2005-FORM 26(13-3-2014).pdf

691-MUM-2005-FORM 26(21-6-2011).pdf

691-mum-2005-form-1.pdf

691-mum-2005-form-2.doc

691-mum-2005-form-2.pdf

691-mum-2005-form-26.pdf

691-mum-2005-form-3.pdf

691-MUM-2005-MARKED COPY(13-3-2014).pdf

691-MUM-2005-MARKED COPY(21-6-2011).pdf

691-MUM-2005-PUBLICATION REPORT(3-10-2008).pdf

691-MUM-2005-REPLY TO EXAMINATION REPORT(21-06-2011).pdf

691-MUM-2005-REPLY TO HEARING(13-3-2014).pdf

691-MUM-2005-SPECIFICATION(AMENDED)-(13-3-2014).pdf

691-MUM-2005-SPECIFICATION(AMENDED)-(21-6-2011).pdf

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Patent Number

259738

Indian Patent Application Number

691/MUM/2005

PG Journal Number

13/2014

Publication Date

28-Mar-2014

Grant Date

26-Mar-2014

Date of Filing

09-Jun-2005

Name of Patentee

CROMPTON GREAVES LTD

Applicant Address

CG HOUSE DR.ANNIE BESANT ROAD, PRABHDEVI, MUMBAI 400025

Inventors:

#	Inventor's Name	Inventor's Address
1	INGLE ASHA	CROMPTON GREAVES LTD MATERIALS AND PROCESS CENTER, KANJUR MARG (E), MUMBAI-400042
2	SINGAL VIVEK	CROMPTON GREAVES LTD MATERIALS AND PROCESS CENTER, KANJUR MARG (E), MUMBAI-400042
3	JOSHI SACHIN	CROMPTON GREAVES LTD MATERIALS AND PROCESS CENTER, KANJUR MARG (E), MUMBAI-400042

PCT International Classification Number

C22C38/00,B21B3/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA