DESC: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, 2016

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
TITLE
“Method for Chemistry Adjustment of Ni Ti Alloy during Secondary Melting in Vacuum Arc Remelting Furnace”
APPLICANT
(a) Name : Mishra Dhatu Nigam Limited
(b) Nationality : Indian
(c) Address : PO Kanchanbagh, Hyderabad, Telangana – 500058, India

The following specification particularly describes the application and the manner in which it is to be performed.
PRIORITY STATEMENT
The present application hereby claims priority from Indian patent application with the application number 202341024928, filed on 31 March 2023, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD OF INVENTION
The present invention describe herein, relates NiTi alloy. More particularly, the present invention relates to a method for adjusting melt composition chemistry during secondary melting using Plasma Arc Welding for making NiTi Alloy.

BACKGROUND OF INVENTION
Ni-Ti (Nickel-Titanium) alloys, also known as Nitinol, are a group of shape memory alloys that are composed of roughly equal amounts of nickel and titanium. These alloys are unique in that they exhibit two distinct properties: shape memory and superelasticity.
Shape memory refers to the ability of a material to "remember" its original shape and return to it after being deformed. Superelasticity, on the other hand, refers to the ability of a material to undergo large deformations and still return to its original shape when the load is removed.
After either heating or cooling (as a function of the specific nitinol alloy under consideration) recover their original shape after the thermal process is reversed, i.e. heated metal is cooled or cooled metal is heated.
While producing Ni Ti Alloy it is very critical to maintain the chemical composition. At present, NiTi Electrode which are used during secondary melting are produced in Vacuum Induction Furnace (VIM) furnace. Herein, the alloy constituents are melted in a Vacuum Induction Furnace (VIM) using high density graphite crucibles. This VIM melting in graphite crucibles allows for the formation of many carbide inclusions in the alloy.
Then this primary VIM ingot is re-melted at least one time in a VAR to form a larger ingot. Very often, during inspection of primary melting electrode it has been found that Ni composition is not up to desired level. It is very critical to compensate Ni as well as ensure that Ni is uniformly distributed in the Ni Ti Alloy.
With this background the present invention proposes a novel method to ensure that Ni is compensated economically thereby avoiding loss of primary VIM melted electrode while manufacturing NiTi Alloy.

OBJECT OF THE INVENTION
The primary object of the invention is to provide a method for adjusting melt composition chemistry during secondary melting using Plasma Arc Welding for making NiTi Alloy.
Another object of the invention is to compensate the Ni in the primary melting electrode during secondary melting .
Another object of the present invention to the use of Plasma Arc Welding Post Primary melting to make Ni Ti Alloy.
Another object of the present invention to provide a method that is cost effective as well as avoid loss of primary melt while making Ni Ti Alloy.

SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the disclosure nor is it intended for determining the scope of the disclosure.
The present invention discloses a method for adjusting the composition of a NiTi alloy electrode obtained from a Vacuum Induction Melting (VIM) furnace, the method comprising calculating the required amount of Nickel (Ni) to compensate for the Ni constituent in the primary melt obtained from the VIM furnace; uniformly placing Ni sheets onto the primary melt electrode based on the said calculation; welding the Ni sheets onto the electrode using plasma arc welding to ensure uniform adhesion and distribution of Ni on the electrode; and vertically melting the primary melt electrode with welded Ni in a Vacuum Arc Remelting (VAR) furnace; thereby adjusting the chemistry of the NiTi alloy during secondary melting.

DESCRIPTION OF THE INVENTION
The present invention relates to a method for adjusting chemistry of primary melt while producing NiTi Alloy using Plasma Arc Welding technique. Ni-Ti alloys typically have a composition of around 50% nickel and 50% titanium, although the exact composition can vary depending on the specific application and desired properties.
In accordance with an embodiment of the present invention, the nickel constituent in Ni-Ti alloys is 55%, while the titanium constituent is 45%.
The exact composition and processing of Ni-Ti alloys can have a significant impact on their mechanical and physical properties, including their shape memory and superelastic behavior. As a result, careful control of the composition and processing parameters is essential to produce Ni-Ti alloys with specific desired properties for a given application.
There are several factors that can contribute to variations in the alloy's composition, including:
Raw materials: The composition of the raw materials used to make the alloy can vary from batch to batch, which can affect the final composition of the NiTi alloy.
Processing parameters: The processing parameters used to melt and cast the alloy can also affect the composition of NiTi Alloy.
Contamination: Contamination during processing, such as from graphite crucibles or molds, can also introduce impurities into the alloy and affect the composition.
Further, the two elements have different atomic weights, and as a result, they have different densities. The density difference between nickel (8.908 g/cm³) and titanium (4.506 g/cm³) also affect the composition of Ni-Ti alloys during production. Therefore, when the two metals are mixed, the resulting alloy's density will depend on the relative amounts of nickel and titanium.
During the production of Ni-Ti alloys, the alloy constituents, nickel and titanium are typically melted together in graphite crucibles to form a homogenous mixture. However, due to the difference in density, the two metals do not mix evenly, and separation of the alloy occur. This leads to variations in the composition of the alloy and affect its properties.
The present method utilizes plasma arc welding technique to adjust melt composition during secondary melting in Vacuum Arc Remelting Furnace.
In accordance with an embodiment of the present invention, the primary melt obtained from the VIM Furnace has Ni constituent out in its composition. In order to compensate the Nickel i.e. adjust the chemistry of Ni Ti Alloy before secondary melt in VAR, calculation is done to understand the amount of Ni to be added.
Once the amount of Ni to be compensated is calculated, Ni which is available in form small sheets are uniformly placed on the primary melt electrode.
In accordance with an embodiment of the present invention, plasma arc welding at a particular temperature and pre defined time is used to weld the Ni on the electrode. The heat generated due to concentrated plasma melts the nickel and make it stuck on the electrode. This ensures that the Ni is stuck on the primary melt electrode.
In accordance with an embodiment of the present invention, the primary melt electrode with welded Ni is melted vertically in VAR Furnace thereby ensuring chemistry adjustment during secondary melting.
Ni-Ti alloys are used in a variety of applications, including biomedical devices such as stents, orthodontic wires, and surgical instruments, as well as in aerospace and automotive industries. They are also used in eyeglass frames, dental braces, and many other consumer products.
The unique properties of Ni-Ti alloys make them ideal for these applications because they can withstand significant stress and deformation without losing their original shape. They also have excellent corrosion resistance and are biocompatible, making them safe for use in the human body.

ADVANTAGES AND APPLICATION
The present invention ensures that the primary melt is not wasted even through if the composition of Ni constituent is out after the primary melt. The production of NiTi Alloys requires very tight chemistry or melt composition to get desired properties in NiTi Alloys. The proposed method is very cost effective and economic for adjusting chemistry while producing NiTi Alloy. It saves all the cost involved in primary melting for producing NiTi Alloy.
,CLAIMS:CLAIMS
We claim:
1. A method for adjusting the composition of a NiTi alloy electrode obtained from a Vacuum Induction Melting (VIM) furnace, the method comprising
a. calculating the required amount of Nickel (Ni) to compensate for the Ni constituent in the primary melt obtained from the VIM furnace;
b. uniformly placing Ni sheets onto the primary melt electrode based on the said calculation;
c. welding the Ni sheets onto the electrode using plasma arc welding to ensure uniform adhesion and distribution of Ni on the electrode; and
d. vertically melting the primary melt electrode with welded Ni in a Vacuum Arc Remelting (VAR) furnace
thereby adjusting the chemistry of the NiTi alloy during secondary melting.
2. The method as claimed in Claim 1, wherein the calculation of the required amount of Ni is based on predetermined chemistry adjustment parameters for the NiTi alloy.
3. The method as claimed in Claim 1, wherein the Ni sheets are uniformly placed on the primary melt electrode to ensure consistent chemistry adjustment during secondary melting.
4. The method as claimed in Claim 1, wherein the plasma arc welding is performed to enable melting and adherence of the Ni sheets onto the electrode.
5. The method as claimed in Claim 1, wherein the primary melt electrode with welded Ni is vertically melted in the VAR furnace to achieve precise chemistry adjustment and homogenization of the NiTi alloy.
6. The method as claimed in Claim 1, wherein the NiTi alloy is intended for use in biomedical devices, aerospace, automotive industries, or consumer products due to its unique properties, including stress resistance, shape memory, corrosion resistance and biocompatibility.