Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A MEDIUM CARBON-MANGANESE-SILICON STEEL COMPOSITION AND A PROCESS TO PRODUCE ADVANCED HIGH STRENGTH STEEL THEREFROM THROUGH QUENCH DEFORMATION AND PARTITIONING.



2 APPLICANT (S)

Name : JSW STEEL LIMITED.

Nationality : An Indian Company incorporated under the Companies Act, 1956.

Address : JSW CENTRE,
BANDRA KURLA COMPLEX,
BANDRA(EAST),
MUMBAI-400051,
MAHARASHTRA,INDIA.




3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION

The present invention relates to a medium carbon-manganese-silicon steel composition comprising (0.2 to 0.4 %C), manganese (1.5 to 3 %),silicon (1 to 2 %)with Ti (0.01 to 0.04) and Nb (0.02 to 0.06) to have advanced high strength low alloy cold rolled steel and a process for their manufacturing. More particularly, the present invention is directed to a range of high strength category comparable with dual phase steel in cold rolled steel, adapted to ensure improved high strength range with ultra-high strength and good ductility favouring application for light weight automotive structures.
Importantly, the high strength in the steel is achieved by a novel quenching followed by cold deformation and partitioning route.

BACKGROUND OF THE INVENTION
Commercial Dual-phase (DP) steels and Transformation Induced Plasticity (TRIP) steels has high strength properties, suitable for automobile application but have advance high strength devoid of alloying elements and process change (strength>1500MPa).Modern automotive and engineering structural applications demand, steels with advance high strength with very good ductility. The high strength steels are in general designed based on different strengthening mechanisms namely, solid solution strengthening precipitation hardening, grain size strengthening, muti-phase strengthening etc. In order to achieve the desired strengthening in the existing known art, other than carbon, various alloy elements such as chromium, nickel, titanium, manganese, vanadium, niobium, titanium, molybdenum etc, or a combination of the elements thereof are added to the steels to achieve the desired level of strengthening. Usually, with increasing strength level, the ductility and formability decreases.
In the present invention a range of steels alloyed with major Mn as alloying element and Al as additional minor alloying element and without any other alloying element and with carbon content has been developed advance high strength range. Compared to other alloying elements in the equivalent high strength steels, the steels invented have cheaper alloying elements. Previous studies have explored evolution of metallurgical theories on solid solution hardening and mechanical behaviour. The present patent explores the capability of the steels for their suitability as a 3rd generation advance high strength steel and the process of manufacture adopted scale in laboratory investigation in most studies. The present patent covers the steel composition that has relatively low carbon and has also low alloying with aluminium content.

B. B. He et al.used a medium Mn steel (10% Mn, 0.47% C, 2% Al and 0.7% V (wt.%)) for the D&P process. The Mn and C atoms are effective austenite stabilizers. The addition of 2% Al content suppresses cementite precipitation during tempering process. The addition of 0.7% V is to form intensive nanometer-sized V carbides which provided enhanced resistance to delayed fracture induced by hydrogen embrittlement. Deformed and partitioning (D&P)that produced by multiple deformation and annealing steps possesses a heterogeneous lamella dual-phase microstructure in which metastable austenite are embedded in a martensite matrix. The as-developed D&P steel possessed an ultra-high yield strength of 2.21 GPa and 2.05 GPa. The patented process has a partition treatment on the martensite formed during deformation while the present invented process has martensite iniiatlly followed by small degree of deformation of the microstructure which introduces dislocations in the plastic phases before partitioning.
[B. B. He, B. Hu, H. W. Yen, G. J. Cheng, Z. K. Wang, H. W. Luo, M. X. Huang, High dislocation density–induced large ductility in deformed and partitioned steels, Science, 10.1126/science.aan0177 (2017).]

Li Liu et al. has developed a process–microstructure relation in D&P process.The as-received ingot is firstly homogenized at 1150 °C for 2.5 h, followed by hot rolling (HR)down to a thickness of 4 mm. The hot rolled sheet is further warm rolled (WR) at 750 °C with a total thickness reduction of 50% and is then intercritical annealed (IA) at 620 °C for 5 h. Afterwards, the sheet is further subjected to cold rolling (CR) with a thickness reduction of 30%, giving the final thickness of about 1.4 mm. Finally, deformed samples are tempered at various temperatures for carbon partitioning from martensite to austenite to optimize austenite stability. Specimens tempered at 200 °C, 300 °C, and 400 °C. Unlike the patented process, where a deformation step (30% reduction) before partitioning tend to introduces strain induced martensite where partition takes place, the deformation degree in the invented process is very low ( <8%), which introduces defects and dislocation in the steel without the formation of strain induced martensite. Hence, the invented process is different from this patented process. The martensite is introduced in the deformation stage in the patented process while the invented process has martensite introduced even before deformation.
[Li Liu ,Binbin He , and Mingxin Huang, Processing–Microstructure Relation of Deformed and
Partitioned (D&P) Steels, Metals 2019, 9, 695; doi:10.3390/met9060695]

Jiang Haitao et al. invention relates to a low-alloyed and high-strength Quench and partitionprocess in which a low alloy Al rich TRIP steel composition was melted hot rolled and cold rolled. This is followed by austenitizing above A3 held for 100 to 200 s , rapidly quenched to 250 oC held for 20 to 40s and reheated for partition at either of 300 or 400 oC held for 120 to 3600 s, to achieve the desired properties. This process does not involve any cold deformation in the heat treatment. However, the invented process has a cold deformation stage introduced after quenching.
[Jiang Haitao, Tang Di, MiZhenli, Chen Yulai, Cheng Zhisong, Dong Chen, Tian Zhiqiang, Zhao Cai, Low-alloy high-strength C-Mn-Al Q & P steel and method of manufacturing the same. Beijing University of Technology of Science and Technology Beijing USTB, 2010-08-11 Publication of CN101487096B.]

Patent No CN105154763A describes a steel plate of composition 0.25-0.32% of C, 1.2-1.8% of Si, 2.5-3.2% of Mn, P which is less than or equal to 0.02%, and S which is less than or equal to 0.005% is initially quench partitioned completely and after the partition stage, the steel is finally cold rolled to develop 1500 MPa by cold rolling. The present invention talks about the first stage where there is quenching and before partition stage a minor cold deformation of 5% is given before partitioning treatment is given where 1470 MPa with 13.5% elongation was developed. [Hu Zhiping ; Liu Rendong ; Lin Li ; Xu Xin ; Hao Zhiqiang ; Zhang Nan ; Jiang Ruiting, Low-carbon silicon-manganese bainite high-strength steel and production method thereof Patent No CN105154763A]
In a patent CN107326160B involving a cold rolled sheet subjected to initial holding in the intercritical temperature of 820 C for 5 to 10 min followed by enhancing the temperature above Ac3 temperature to 920 C for 3 min. This is followed by another intercritical treatment at 860 to 880 C for 3 to 7 min. This is followed by single stage quenching to 240 to 260 oC for 10 to 30 s and quenching after partitioning at the quench temperature. Whereas the patent has no deformation in its entire quench partitioning cycle, the present invention has a mild cold deformation after quenching and the partition takes place after the deformation, Hence the process in the present invention is significantly different.
[Jing Cainian ; Xing Zhaohe ; TuYingming ; LV Minghua, Comprehensive distribution heat treatment method of low-carbon C-Mn-Si series steel C, Mn with TRIP effect, CN107326160B]
The process involves cold rolled steel subject to inter critical slow cooling followed by quenching below Ms temperature followed by tempering at a lower temperature followed by temperature increase to galvanizing bath temperature followed by slow cooling. There is no deformation in the entire heat treatment cycle in the patent while the present invention involves quenching followed by deformation followed by partitioning.
[Hu Zhiping, Liu Rendong, Lin Li, Xu Xin, HaoZhiqiang, Zhang Nan, Jiang Ruiting, 980-MPa-grade cold-rolled alloyed galvanized quenched partition steel and preparation method thereof, CN113061812A]

The patent CN109694992A starts with a cold rolled plate where the steel is subjected to quench and partitioning. The steel is cold rolled after complete partitioning where 1500 MPa was realized. The present invention has a different concept that a mild cold deformation is imparted in a stage before partitioning where Ultra high strength is achieved.
[JinXiaolong, Wang Xu, Liu Rendong, Wang Keqiang, GuoJinyu, Xu Rongjie, MengJingzhu, Lin Li, HaoZhiqiang, Quenching and partitioning steel with tensile strength being greater than 1,500 MPa, and production method thereof CN109694992A]

Compared to the existing prior art, the present invention is explores influence of much lower degree of deformation than in earlier studies, where deformation induced martensite was formed. In spite of the lower degree of deformation, a very good enhancement of mechanical properties is seen. The various aspects of processing, microstructure and mechanical properties are brought out.

OBJECT OF THE INVENTION
The primary object of the present invention is to provide medium carbon Mn-Si cold rolled steel and method thereof to make it through quench partitioning with deformation to have advanced high strength and good ductility.

A further object of the present invention is directed to develop medium carbon Mn-Si cold rolled steel through quench partitioning with deformation having a fine tempered martensite microstructure with very good strength with ductility.

A still further object of the present invention is directed to develop medium carbon Mn-Si cold rolled steel through quench partitioning with deformation that shows high yield strength, high ultimate tensile strength, high YS/UTS ratio and high strain hardening exponent (n) required for automotive application and other sectors.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to provide high strength steel comprising steel composition having carbon content 0.2 to 0.4%. preferably about (0.22%), silicon content 1 to 2 %. preferably (1.5%), manganese content 1.5 to 3% preferably (2.3%), Ti 0.01-0.04 and preferably 0.035%, Nb 0.02 to 0.06% preferably 0.05 % and optionally residual elements S<0.005% preferably 0.003%, P<0.025%, and rest base metal Fe which is quench cold deformed and partitioned,

having strength comprising yield strength (YS) in the range of 1281 to 1295 MPa,and product of strength and ductility in the order of 18 to 22GPa% as observed about 19.1GPa%.

A further aspect of the present invention is directed to said high strength steel comprising ultimate tensile strength (UTS) in the range of 1472 to 1475 MPa, YS/UTS ratio in the range of 0.87 to 0.88 and strain hardening exponent (n) of 0.63 and fine tempered martensite microstructure.
A still further aspect of the present invention is directed to a process to manufacturing said high strength steel comprising subjecting said steel composition to manufacture including in a Basic oxygen furnace followed by RH degassing and ladle metallurgy followed by continuous casting to a 200 mm thick slab. The slab is then reheated and deformed at 1190 + 50oC with a roughing mill finish temperature of 1190 + 50 oC .This is followed by finishing mill deformation to a hot rolled coil with a finishing mill temperature of 860 oC+ 25 oC and coiled to a hot band at 580+20 oC to a sheet thickness of 2.6 to 2.8 mm thickness. The hot band is pickled and cold rolled with a 80 to 85% reduction to achieve a cold rolled sheet thickness of 1.6 mm. This steel so made was finally subjected to thermal cycle heat treatment including initial quenching followed by a 3 to 8% cold deformed followed by steps of partitioning and further quenching to a yield strength (YS) in the range of 1281 to 1295 MPa, ultimate tensile strength (UTS) in the range of 1472 to 1475 MPa, YS/UTS ratio in the range of 0.87 to 0.88.

A still further aspect of the present invention is directed to said process wherein said quench partitioning with deformation, involve the Gleeble cycle comprising of heating the sample at the rate of 10°C/s to a temperature of 830°C. , holding the steel was held at 830°C temperature for 300 second; thereafter subjecting the specimen to straining by 10% at a strain rate of 0.008 /sec at high temperature; said straining is followed by cooling the sample at the rate of 20°C/sec to an intercritical temperature of 770°C and holding at this temperature for 180 sec. , the sample is next water quenched to room temperature. ;the water quenched samples were deformed to a 5% strain in a tensile machine at a strain rate of 0.008/sec. , after this strain, the steel was subjected to a salt bath heat treatment at 400°C and held for 180 sec., said salt bath holding was followed by water quenching to room temperature.

A still further aspect of the present invention is directed to said high process wherein no deformation is induced in martensite while for deformation partitioning, introduction of mild cold deformation post quenching provided for said improved steel ductility and strength significantly.

The quench partitioning with deformation, wherein the Gleeble cycle followed involves heating the sample at the rate of 10°C/s to a temperature of 830°C. The steel was held at 830°C temperature for 300 second. Thereafter the specimen was strained by 10% at a strain rate of 0.008 /sec at high temperature. The straining is followed by cooling the sample at the rate of 20°C/sec to an intercritical temperature of 770°C and held at this temperature for 180 sec. The sample is then water quenched to room temperature. The above cycle was carried out using the Gleeble simulator model 3800 facility at JSW Steel Ltd. The water quenched samples were deformed to a 5% strain in a tensile machine at a strain rate of 0.008/sec. After this strain, the steel was subjected to a salt bath heat treatment at 400°C and held for 180 sec. The salt bath holding was followed by water quenching to room temperature.

The properties of invented steel involving deformation during thermal processing gave ultra-high strength of the order of 1470 MPa and excellent ductility of the order of 13.5 % elongation. The product of strength and ductility is of the order of 19.1 GPa%. This invention shows even small deformation levels before partitioning can improve the properties significantly. Thus, this invention shows that even though there is no deformation induced martensite for deformation partitioning, introduction of mild deformation during deformation can improve the steel ductility and strength significantly.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1. Illustrates the heat treatment cycle schematic diagram according to the present invention;

FIG. 2. Illustrates the influence of deformation & partitioning in cold rolled steel sheet on optical microstructure;

FIG. 3. Illustrates the influence of deformation &partitioning in cold rolled steel sheet on mechanical properties (yield strength, ultimate tensile strength, percentage elongation);

FIG. 4.Illustrates the influence of deformation & partitioning in cold rolled steel sheet on XRD phase analysis.

Skilled artisans would appreciate that elements in the figures are illustrated for simplicity and clarity of the invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The accompanying figure together with the detailed description below forms a part of the specification and serves to further illustrate various embodiments and to explain the various principles and advantages all in accordance with the present invention.

Before describing in detail embodiments that are in accordance with the invention, it should be observed that herein a medium carbon Mn-Si cold rolled steel strip is produced through quench partitioning with deformation.

The present invention thus relates to a quench partitioning with deformation based cold rolled steel having high strength and ductility suitable for automobile structural components.

The quench partitioning with cold deformation processed steels, is effective in providing fine tempered martensite microstructure, in the high strength range. Cold deformation to as low as 5% deformation may not introduce strain induced martensite, but the slip steps are created in ferrite. As martensite and retained austenite are harder phases, the tensile deformation may strain inter critical ferrite. This ferritic deformation with subsequent partition at 400°C imparts high strength properties.

The SEM microstructure in intercritical austenitized quench partitioned steel, the ferrite content was 64% and the ferrite has fine carbide precipitation in the matrix. The steel austenitized at 830°C and quench partitioned show a dense distribution of tempered martensite along with regions of blocky ferrite which was about 12%. The processing with warm deformation – quenching and cold deformation and partitioned condition show fine ferrite laths with fine martensite and the ferrite content was 35%.The highest strength was achieved where the hard phases were more but the ductility was limited. Even a small degree of deformation in the deformation quench partitioned steel has refined the microstructure with enhanced the ferrite content, which could be the reason for enhanced ductility along with strength.

The quench partitioning with deformation steels, in the cold rolled condition mechanical properties are gave ultra-high strength of the order of 1470 MPa and excellent ductility of the order of 13.5 % elongation. The n value is significantly high (0.63) and the yield ratio (0.88) is the highest. The product of strength and ductility is of the order of 19.1 GPa%,

The quench partitioning with cold deformation processed steel subject to XRD phase analysis shows that the steel does not have significant amount of retained austenite. This implies that deformation partitioning does not generate larger fraction of austenite that remains stable to room temperature.

Experiments that were actually performed are now described by way of following examples.

Evaluation 1. Heat treatment cycle of the quench partitioning with deformation in a medium carbon Mn-Si coldrolled steel according to the present invention.

Firstly, providing the starting composition of the steels as shown in Table1,the chemistry of the steel was determined using spectromax optical emission spectrometer. A set of samples were subjected to the conventional cut samples as per dimension 120x30 mm2 were subjected to thermomechanical-simulator based deformation induced partitioning. The Gleeble cycle followed involves heating the sample at the rate of 10°C/sec to a temperature of 830°C. The steel was held at 830°C temperature for 300 sec. Thereafter the specimen was strained by 10% at a strain rate of 0.008 /s at high temperature. The straining is followed by cooling the sample at the rate of 20°C/s to an intercritical temperature of 770°C and held at this temperature for 180 second. The sample is then water quenched to room temperature. The above cycle was carried out using the Gleeble simulator model 3800 facilities at JSW Steel Ltd. The water quenched samples were deformed to a 5% strain in a tensile machine at a strain rate of 0.008/sec. After this strain, the steel was subjected to a salt bath heat treatment at 400°C and held for 180 sec. The salt bath holding was followed by water quenching to room temperature as shown in schematic diagram Figure 1.

Table 1 Composition of the steel (in wt. %)
wt.% C Mn Si S Al P Ti Nb Cr
Range 0.2 to 0.4 1.5 to 3.0 1.0 to 2.0 < 0.005 <0.05 < 0.025 0.01 to 0.04 0.02 to 0.06 <0.03
Steel A 0.22 2.3 1.5 0.003 0.350 0.027 0.035 0.050 0.020

Evaluation 2: Microstructure of the quench partitioning with deformation in a medium carbon Mn-Si cold rolled steel

The microstructure of the steel so produced as in the manufacturing in Exam 1 was characterized for their microstructure. The cold rolled steel with quench partitioning with deformation was sampled in accordance with ASTM E3 - 11(2017).The microstructure of the steel after deformation and partitioning is shown in Figure 2. The optical microstructure etched with Nital clearly shows large island of martensite with irregular shape being distributed in a matrix of bainitic ferrite. The steel was examined using Lepera reagent with light etching and dark etching. The light etched samples gave extremely fine granular structure. The bluish brown coloured phase is normally attributed to bainite phase.At 830°C, there is the austenite phase the warm deformation to a tune of 10% introduces dislocations in the matrix. Lowering the temperature to 770°C generates finer ferrite uniformly from the boundaries and sub grain boundaries created during warm deformation. The austenite boundaries are fine and hence the martensite during subsequent quenching refines the retained austenite distribution. Cold rolling to 5% deformation, introduces deformation. As martensite and retained austenite are harder phases, the tensile deformation may strain the intercritical ferrite. This small deformation may not introduce strain induced martensite, but the slip steps are created in ferrite. Subsequent partition takes place at 400°C. Figure 2 shows typical microstructure of deformation and partitioned steel sheet (a) Nital etched (b) Lepera etched [ white = martensite, a’; bluish brown = bainite, aB; dark brown = ferrite, a ].

Evaluation 3: Mechanical properties of the quench partitioning with deformation in a medium carbon Mn-Si cold rolled steel

Few distinct deformation and partitioning range of strength claimed in the patent have been evaluated for the mechanical properties at room temperature of a chosen thickness of 1.6 mm. The tensile properties were tested in accordance with ISO 6892.The properties of the steel involving deformation during thermal processing gave ultra-high strength of the order of 1470 MPa and excellent ductility of the order of 13.5 % elongation as shown in Figure 3 and the property data is compiled in Table 2. The n value is significantly high and the yield ratio is the highest. The product of strength and ductility is of the order of 19.1 GPa%. This study shows even small deformation levels can improve the properties significantly.

Table 2 Mechanical properties of the steel heat treated by deformation quench and partitioning route
Grades Hardness Hv YS (MPa) UTS (MPa) n K
(MPa) (YS/
UTS) %E (0.5”) UTS.%E
GPa.%
Deformation & Partitioning 493±0.5 1288+7 1470+45 0.63+.2 164 0.88 13.5±0.4 19.1

Thus, the steels in the present invention, is a light weight, advance high strength steel with excellent range of mechanical properties and ductility characteristics.

Evaluation 4: XRD phase analysisof the quench partitioning with deformation in a medium carbon Mn-Si cold rolled steel
XRD phase analysis was performed in the deformed quench and partitioned steel which shows that the steel does not have significant amount of retained austenite as shown in Figure 4. This implies that deformation partitioning does not generate larger fraction of austenite that remains stable to room temperature.Figure 4 shows XRD phase analysis on the deformation and partitioned steel showing predominantly ferrite and absence of austenite peaks.

, Claims:We Claim:

1. High strength steel comprising steel composition having carbon content 0.2 to .0.4 % preferably about (0.22%), silicon content 1.0 to 2.0 % preferably (1.5%), manganese content 1.5. to 3.0 % preferably (2.3%), Ti 0.01-0.04 and preferably 0.035%, Nb 0.02 to 0.06% preferably 0.05 % and optionally residual elements S<0.005%, P<0.025%, and rest base metal Fe which is quench partitioned with cold deformation having strength comprising yield strength (YS) in the range of 1281 to 1295 MPa, and product of strength and ductility in the order of 18 to 22 GPa% preferably about 19.1 GPa%.

2. The high strength steel as claimed in claim 1 having ultimate tensile strength (UTS) in the range of 1472 to 1475 MPa, YS/UTS ratio in the range of 0.87 to 0.88 and strain hardening exponent (n) of 0.63 and fine tempered martensite microstructure.

3. A process for manufacture of the high strength steel as claimed in anyone of claims 1 or 2 comprising
subjecting the said steel composition to manufacture including in a basic oxygen furnace followed by RH degassing and ladle metallurgy followed by continuous casting into slab, the slab is thereafter reheated and deformed at 1190 + 50oC with a roughing mill finish temperature of 1190 + 50 oC followed by finishing ill deformation to a hot rolled coil with a finishing mill temperature of 860 oC+ 25 oC and coiled to a hot band at 580+20 oC to a sheet thickness of 2.6 to 2.8 mm thickness and finally subjected to thermal cycle heat treatment including initial quenching followed by a 3 to 8% cold deformed followed by steps of partitioning and further quenching to a yield strength (YS) in the range of 1281 to 1295 MPa, ultimate tensile strength (UTS) in the range of 1472 to 1475 MPa, YS/UTS ratio in the range of 0.87 to 0.88.
4. The process as claimed in claim 3 comprising subjecting to a processing involving making a continuously cast slab from a slab made from primary steel making process of BOF followed by secondary steel making using RH degassing and ladle metallurgy to achieve the required composition and cast into a continuously cast slab of 200 mm thickness.

5. The process as claimed in anyone of claims 3 or 4 comprising involving said composition and casting followed by initially hot rolling in a roughing mill after reheating in a furnace and ensuring the roughing deformation temperature of 1190 + 50oC and a roughing mill finishing at 860 oC ±25 °C and a finishing mill deformation to 2.6 to 2.8 mm with a finishing mill temperature of 860 oC+ 25 oC and a hot band coiling temperature of 580+20oC, picking the hot band and cold rolling with a 80 to 85% reduction in a PLTCM to achieve a 1.6 mm thick cold rolled coil for further heat treatment.

6. The process as claimed in anyone of claims 3 to 5 comprising said melting and casting followed by hot and cold rolling and thereafter subjecting to a thermal cycle through a Gleeble including heating the steel at the rate of 10°C/s to a hot rolling temperature of 830 oC, hold for 300 seconds and give a 10% initial deformation to the steel at a strain rate of 0.008 /sec, after deformation at 830 oC, the steel is cooled at the rate of 20°C/sec to intercritical temperature of 770 oC and held for 180 seconds leading to the formation of ferrite and austenite and enrichment of the carbon by the ferrite that form at this temperature of 770 oC; and from 770 oC with thus obtained carbon enriched austenite the steel is next quenched to room temperature which produces carbon rich martensite and retained austenite, the steel at room temperature is given a 8% cold reduction at a strain rate of 0.008/sec. to strain the ductile phases which is followed by partitioning of the steel subjected to a salt bath heat treatment at 400 oC for 180 s followed by water quenching to room temperature.

7. The process as claimed in anyone of claims 3 to 6 carried out as per said chemistry , melting and casting, hot and cold rolled strip forming and thermal processing to have an yield strength (YS) in the range of 1281 to 1295 MPa, ultimate tensile strength (UTS) in the range of 1472 to 1475 MPa, YS/UTS ratio in the range of 0.87 to 0.88 and strain hardening exponent (n) of 0.63.

Dated this the 1st day of July, 2022
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199