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, 2006
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF INVENTION
A method for improving the magnetic properties of fully processed non-oriented electrical steel
APPLICANTS
Name : CROMPTON GREAVES LIMITED
Nationality : Indian Company
Address : CG House, Dr Annie Besant Road, Worli, Mumbai 400030, Maharashtra, India
INVENTORS:
Singhai Mrigandra, and Dr Ingle Asha, both of Advanced Materials and Process Centre, Crompton Greaves Ltd, CG Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention :

FIELD OF THE INVENTION
This invention relates to a method for improving the magnetic properties of fully processed non-oriented electrical steel
This invention also relates to fully processed non-oriented electrical steel or electrical components made therefrom treated by the above method and having improved magnetic properties.
PRIOR ART AND BACKGROUND DESCRIPTION
Non-oriented electrical steel components are widely used in electrical machines like motors, generators or ballasts because of its excellent magnetic properties. Non-oriented electrical steel is generally fully processed or semi-processed. Fully processed non-oriented electrical steel components are usually directly used in electrical machines without any further treatment, whereas semi-processed non-oriented electrical components are generally given grain growth annealing at about 780-800°C at customers' end so as to improve the magnetic properties of the components prior to their use in the electrical machines. During making of electrical components like stator, rotor or ballast cores from non-oriented electrical steel, they are subjected to stresses and strains due to the various operations involved like shearing, punching, stamping, interlocking or welding resulting in the deterioration of magnetic properties of the components. It has been found out by us by extensive research and experimentation that the magnetic properties and grain size distribution of fully processed non-oriented electrical steel and electrical components made therefrom can be improved by subjecting the steel and the electrical components to an annealing treatment. It is believed that during the annealing treatment the residual stresses and strains in the steel especially those introduced in the

steel components during the various forming operations thereof are relieved so as to improve the magnetic properties of the steel and the steel components.
DETAILED DESCRIPTION
According to the invention there is provided a method for improving the magnetic
properties of fully processed non-oriented electrical steel, the method comprising
annealing the fully processed non-oriented electrical steel at a temperature between 650-
750°C followed by cooling the steel to the ambient temperature.
The non-oriented electrical steel is in the form of electrical components.
According to the invention there is also provided fully processed non-oriented electrical
steel or electrical components made there from treated by the above method and having
improved magnetic properties.
Fully processed non-oriented electrical steel samples were subjected to annealing
according to the method of the invention. The samples had silicon and aluminium
contents of 2% and 0.3%, respectively and core loss of 3.367 and permeability of 1687 at
1.5T (Tesla). The grain size distribution of the steel samples was as shown in Fig 1 of the
accompanying drawings. The magnetic properties of the samples after annealing were as
shown in the following Table:
Table

Annealing temperature and duration Core Loss at 1.5T Permeability at 1.5T
680°C for 90 mins 2.93 3454
700 °C for 90 mins 2.947 3558
720 °C for 90 mins 2.896 3532

The grain size distribution of the samples annealed at 680° C, 700° C and 720° C were as shown in Figs 2, 3 and 4 of the accompanying drawings.
The Table clearly shows that due to annealing the core losses of the samples reduced substantially and permeability of the samples improved considerably. Figs 2 to 4 also show that the grain size distribution of the samples substantially improved and was near uniform. Due to the improved magnetic properties of the fully processed non-oriented electrical steel obtained by the method of the invention, the energy transition and efficiency of the electrical machines using electrical components annealed by the method of the invention will be substantially improved. This will adequately compensate for the energy requirement and cost of the annealing treatment of the method of the invention.