DESC:PRIORITY STATEMENT
The present application hereby claims priority from Indian patent application with the application number 202341024828, filed on 31 March 2023, the entire contents of which are incorporated herein by reference.

FIELD OF INVENTION
The present invention belongs to the technical field of metal materials. More particularly, the present invention relates to method for development of ultra-high strength 12X18H10T wires having excellent cold workability and high critical strength.

BACKGROUND OF INVENTION
The austenitic stainless steel spring wire has very strict requirements on its processing method, material properties, dimensional accuracy, surface quality and non-destructive testing.
At present, the austenitic stainless steel wire material generally adopts a preparation process combining a hot working process such as forging and hot rolling with a fixed die drawing cold working process.
Cold drawing is a metal working process used to shape metal alloys into thinner or smaller sections. In the case of 12X18H10T, cold drawing is used to produce wires of different sizes and diameters. During the cold drawing process, the steel wire is pulled through a die, reducing its diameter and increasing its length. The process also improves the mechanical properties of the wire, such as its tensile strength and toughness.
It is important to note that cold drawing can affect the microstructure of the steel, which can in turn affect its mechanical properties. Therefore, it is essential to carefully control the cold drawing process to ensure that the final product meets the desired specifications.
The cold working austenitic stainless-steel wire has a low elongation rate, the winding spring process damages the mold greatly, the finished spring has poor straightness, and even the stainless-steel wire breakage occurs, so on the basis of ensuring the strength of the austenitic stainless steel wire. It is necessary to further increase its elongation.

Various attempts were made by the applicant, wherein the 12X18H10T grade austenitic stainless-steel wire with an outer diameter of 7.5 mm was reduced to 5 mm i.e. 55% cold reduction; and wire with an outer diameter of 4.5 mm was reduced to 2.25 mm i.e. 75% cold reduction. In both the attempts, the tensile strength achieved was 1243 and 1407 MPa respectively which is very less as compared to desired tensile strength of 1620 – 2010 MPa. The wire was broken when further reduction was given.

Cold Drawn Size (mm) Cold Reduction (%) Strength Achieved (MPa) Remarks
Cold Drawn from Ø 7.5 to Ø 5 55.55 1243 Material was broken when further reduction was given
Cold Drawn from Ø 4.5 to Ø 2.25 75 1407 Material was broken when further reduction was given

Further, several journals in literature described the improvement of mechanical properties by cryo drawing/rolling to obtain deformed martensite.
Accordingly, attempts were made for cryo drawing by dry ice. However, the mechanical properties were not satisfactory due to temperature loss during wire drawing operation.
The present invention overcomes the drawback posed by prior arts and discloses an improved process for development of ultra-high strength 12X18H10T cold drawn wires.

OBJECT OF THE INVENTION
The principal object of the present invention is to provide a novel processing route for cold drawing of 12X18H10T wire.
Another object of the invention is to improve the the mechanical properties of 12X18H10T wire.

Another object of the invention is to disclose a novel process with high temperature annealing thereby improving cold drawing and tensile strength of 12X18H10T wire.

SUMMARY OF THE INVENTION
The present invention discloses a method of manufacturing high strength cold drawn 12X18H10T wire comprising the steps of adopting process to obtain 9 mm wire of composition in weight percent Cr - 18%, Ni - 10%, Ti - 0.6%, C - 0.12% and balance Fe along with inevitable impurity; subjecting the said wire to high temperature annealing at 1150°C for 120 minutes to promote formation of coarse grains; optimizing cold reduction to achieve a reduction percentage between 80% to 92%; and drawing the wire to a final diameter ranging from 4 mm to 2.5 mm with increased tensile strength.

Further, the present invention discloses a high strength cold drawn 12X18H10T wire of diameter ranging from 4 mm to 2.5 mm characterized by having undergone high temperature annealing at 1150°C for 120 minutes; exhibiting excellent cold workability with a tensile strength ranging from 1720 to 2010 MPa; demonstrating a drawing range of 80% to 92%.

BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure may be understood when read in conjunction with the following drawings and or illustrations:
Fig. 1 and 2 illustrates the microstructure for diameter 9 mm as received and Post Annealing in accordance with an embodiment of the present invention.
Fig. 3 illustrates a graph of Tensile Strength Vs % Cold Reduction in 12X18H10T wire.

DESCRIPTION OF THE INVENTION
The present invention relates to cold drawing of the 12X18H10T wire. 21X18H10T is a grade of austenitic stainless steel having composition in weight percent 18% chromium, 10% nickel, 0.6% of titanium, 0.12% Carbon and balance Fe along with inevitable impurity. It is also referred to as AISI 321 internationally.

In accordance with an embodiment, the present invention discloses High-strength 12X18H10T wire with excellent cold workability, characterized by being subjected to high temperature annealing at 1150o C for 2 hrs.

Further, the cold workability is excellent, characterized in that it has mechanical properties such that the tensile strength is in the range of more than 1720 to 2010 MPa and the drawing is in the range of 65 to 92%.

In another aspect, the present invention provides a modified process route for development of ultra-high strength 12X18H10T cold drawn wires. The method for cold drawing of wire is as follows:

First, the wire to be used for manufacturing ultra-high strength 12X18H10T wire is manufactured by processing route i.e. EAF + VAR + Forging + Hot Rolling + Bar and Wire Drawing

In the next stage, after receiving the wire of approx. 9 mm in diameter from Hot Roll Milling through Bar and Wire Drawing, the wire undergoes high temperature annealing at 1140 o C - 1160o C for 115-135 minutes for formation of coarse grains that increases cold reduction as compared to fine grains.

Finally, cold reduction is optimized i.e. 80-92% of cold reduction is achieved through which 4 – 2.5 mm diameter wire is drawn from 9 mm dia wire. The present invention discloses improved cold workability and increased tensile strength.

ADVANTAGES AND APPLICATION
12X18H10T cold drawn wires are commonly used in a variety of applications, including the production of springs, fasteners, and welding electrodes. The high corrosion resistance and excellent mechanical properties of this grade of stainless steel make it suitable for use in harsh environments and high-temperature applications.
,CLAIMS:Claims:
We Claim
1. A method of manufacturing high strength cold drawn 12X18H10T wire comprising the steps of:
a. Adopting process to obtain 9 mm wire of composition in weight percent Cr - 18%, Ni - 10%, Ti - 0.6%, C - 0.12% and balance Fe along with inevitable impurity;
b. Subjecting the said wire to high temperature annealing at 1150°C for 120 minutes to promote formation of coarse grains;
c. Optimizing cold reduction to achieve a reduction percentage between 80% to 92%; and
d. Drawing the wire to a final diameter ranging from 4 mm to 2.5 mm with increased tensile strength.
2. A method of manufacturing high strength cold drawn 12X18H10T wire, as claimed in claim 1, wherein the process route comprising Electric Arc Furnace (EAF), Vacuum Arc Remelting (VAR), Forging, Hot Rolling, and Bar and Wire Drawing.
3. A method of manufacturing high strength cold drawn 12X18H10T wire, as claimed in claim 1, wherein the coarse grains formed during high-temperature annealing improves the cold reduction properties.
4. A method of manufacturing high strength cold drawn 12X18H10T wire, as claimed in claim 1, wherein the wire drawn showcases a tensile strength of approximately 1720 to 2010 MPa and a drawing percentage ranging from 80% to 92%.
5. A high strength cold drawn 12X18H10T wire of diameter ranging from 4 mm to 2.5 mm characterized by:
a. Having undergone high temperature annealing at 1150°C for 120 minutes;
b. Exhibiting excellent cold workability with a tensile strength ranging from 1720 to 2010 MPa;
c. demonstrating a drawing range of 80% to 92%.
6. A high strength cold drawn 12X18H10T wire as claimed in claim 6, wherein the improved cold workability enables the wire to be used in critical applications with minimal risk of deformation or fracture.