DESC:PRIORITY STATEMENT
The present application hereby claims priority from Indian patent application with the application number 202341024811, filed on 31 March 2023, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD OF INVENTION
The present invention in general is related to the field of titanium metallurgy. More specifically, the invention relates to thermal processing of TITAN31 ELI heavy section slab forging having uniform mechanical properties and soundness in all three directions.

BACKGROUND OF INVENTION
Titan 31, commonly referred to as Ti6Al4V Titanium alloy, stands as an essential material in various industrial sectors, notably in aerospace and specialized sectors requiring resilience in extreme conditions. Known as a two-phase alpha-beta type alloy, it is known for its strength-to-weight ratio, corrosion resistance and hardness.

The conventional grade of Titan 31 contains oxygen levels up to 2000 ppm and is adept for applications within temperature thresholds of 300°C. The second one which is Extra low interstitial (ELI) grade with oxygen upto 1300 ppm which is known for exhibiting the property of toughness can be used in applications as low as -196°C.

The forging process is more complicated because the continuation is directly related to the subsequent heat treatment process. Not only the research and development of the forging process, but also the heat treatment process after forging.
Further, manufacturing of large size (200 thick X 1600 width X 2500 L) TITAN31 ELI slab with limiting section thickness beyond the international specifications to fulfilling the stringent requirements like mechanical properties and ultrasonic classes on product is challenging. Hot working of large size component is normally realized through forging route.

Till date, there is no prior art available on beta solution annealing in between hot working and no data on establishment of mechanical properties on heavy section titanium slab forgings.

Accordingly, the present invention discloses a newly designed forging method for forging heavy section titanium slab by optimizing the thermal processing parameters such as temperature, forging ratio, beta annealing temperatures and heat treatment cycle, and ensuring uniform mechanical properties.

OBJECT OF THE INVENTION
The primary object of the present invention is to disclose a novel forging method for the production of large section (200 thick X 1600 width X 2500 L) Titan31 ELI slab forging with uniform mechanical properties in three directions viz. longitudinal, Long Transverse and short transverse along with stringent Ultrasonic testing requirement.
Another object of the invention is to forge a large section (200 thick X 1600 width X 2500 L) Titan31 ELI slab with uniform mechanical properties.
Another object of the invention is to disclose a solutionizing treatment designed as double beta solutioning treatment above beta transverse temperature and one beta solutionizing treatment in below beta transverse temperature to improve the soundness and uniform properties in three directions.
Another object of the invention is to establish a duplex annealing cycle to obtain alpha plus beta microstructure having good fracture toughness.

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.
To overcome the problems mentioned above, a novel forging method for manufacturing heavy section titanium slab of dimensions 200 mm X 1600 mm X 2500 mm L forging, comprising: blending titanium sponge with master alloys and other alloying elements to form an electrode for producing Titan31 ELI ingots; multiple melting the electrodes in a vacuum arc remelting furnace to achieve homogeneity in the resulting final ingot; thermal processing of the ingot including: heating the ingot to 1100-1180°C and forging it to a block of dimensions 650 mm X 1250 mm X L; further heating the forged block to 900-960°C and forging it to a block of dimensions 600 mm X 1350 mm X L; beta solution annealing the block at 1020°C followed by water quenching; reheating the beta solution annealed block to 930°C and forging it to a block of dimensions 500 mm X 1450 mm X L; second beta solution annealing the block at 1000-1080°C followed by water quenching; reheating the beta annealed block to 930°C and forging it to a block of dimensions 450 mm X 1600 mm X L; subjecting the forged slab to duplex annealing, solutionizing at 910-950°C for 4 hours followed by water quenching and annealing at 700-780°C for 8 hours followed by air cooling; forging the said process annealed block to a slab of dimensions 200 mm X 1600 mm X 2500 mm L followed by air cooling.

Further, the present invention discloses a heavy section titanium slab of dimensions 200 mm X 1600 mm X 2500 mm L with uniform mechanical properties in all directions longitudinal, long transverse and short transverse.

BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure may be understood when read in conjunction with the following drawings and or illustrations:
Fig. 1 illustrates a Conventional thermal processing cycle for hot working of titanium alloys.
Fig. 2 illustrates modified thermal processing cycle Two times beta solutionizing in above beta and one time in below beta.
Fig. 1 illustrates the microstructure of the heavy section titanium slab in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses a novel method for manufacturing heavy section titanium slab forging.
In accordance with an embodiment of the present invention, production of Titan31 ELI ingots starts with blending of titanium sponge with master alloys and other alloying elements to form an electrode. The electrodes are multiple melted in a vacuum arc remelting furnace to ensure an acceptable degree of homogeneity in the resulting final ingot.
The composition of Titan 31 ELI in weight percent is as follows: Titanium - 88.09 – 91, Aluminium (Al) - 5.5-6.5, Vanadium (V) - 3.5-4.5, Iron (Fe) - 0.25, Oxygen (O) - 0.13, Carbon (C) - 0.08, Nitrogen - 0.03, Hydrogen - 0.0125 and balance other elements.

In accordance with an embodiment of the present invention, the thermal processing of heavy section titanium slab forging includes the steps as follows:

The Ingot of diameter Ø 850 mm X 1700 mm L is heated at 1100 -1180 oC using gas fired reheating furnace and forged to 650 mm X 1250 X L square block. The forged block is further heated at 900-960 oC and forged to 600 X 1350 X L block. The block is then beta annealed at 1020 oC followed by water quenching. This beta annealed forged block is reheated at 930 oC and forged to 500 X 1450 X L.

The block further undergoes second beta solution annealing at 1000-1080oC followed by water quenching. The beta annealed forged block is reheated at 930 oC and forged to 450X1600X L block. The forged block is process annealed at 920-970 oC followed by water quenching.

In accordance with an embodiment of the present invention, the process annealed block is further forged to 200 X 1600 X 2500 L followed by air cool. The forged block subjected for duplex annealing, solutionizing at 935 oC for 4 hours followed water quenched and annealed at 700-780 oC for 8 hours followed air cool.
In accordance with an embodiment of the present invention, the combination of beta annealing and process annealing improved the material flow during hot working and well distributed fine elongated alpha in beta matrix through the slab.
The resultant Ti slab when subjected for testing found uniform mechanical properties in all three directions longitudinal, Long Transverse and short transverse along with stringent Ultrasonic Testing qualification.
In accordance with an embodiment, the present invention aims at establishing forging sequence in beta and alpha plus beta with intermediate beta solutionizing treatments. The solutionizing treatment designed as double beta solutioinizing treatment above beta transverse temperature and one beta solutionizing treatment in below beta transverse temperature to improve the soundness and uniform properties in three directions. Subsequently established the duplex annealing cycle to obtain alpha plus beta microstructure to retain a good fracture toughness.

As per AMS4931 (International standard)

Achieved Mechanical properties:
Spec.
AMS 758 827 8 20
Direction YS UTS %E %RA
Longitudinal 867 940 16 46
912 991 18 51
878 949 18 42

Transverse 903 974 17 46
931 1008 17 52
899 972 16 52

Short transverse 850 968 16 27
849 965 15 26
849 965 14 28

ADVANTAGES AND APPLICATION
The present invention offers several advantages including improved strength and durability. The enhanced microstructure having more uniform and homogenous material offer better resistance to cracking and other forms of metal failure. Further, heavy section forged slab allows for the production of custom shapes and sizes, enabling manufacturers to produce components that are optimized for specific applications, resulting in improved efficiency and reduced waste. Overall, forging heavy section titanium slabs can result in a stronger, more durable, and higher quality product that is better suited for high-stress applications, making it a popular manufacturing method for components used in industries such as aerospace, automotive, and medical.
,CLAIMS:CLAIMS
We claim:
1. A method for manufacturing heavy section titanium slab of dimensions 200 mm X 1600 mm X 2500 mm L forging, comprising:
a. Blending titanium sponge with master alloys and other alloying elements to form an electrode for producing Titan31 ELI ingots;
b. Multiple melting the electrodes in a vacuum arc remelting furnace to achieve homogeneity in the resulting final ingot;
c. Thermal processing of the ingot including:
i. Heating the ingot to 1100-1180°C and forging it to a block of dimensions 650 mm X 1250 mm X L
ii. Further heating the forged block to 900-960°C and forging it to a block of dimensions 600 mm X 1350 mm X L;
iii. Beta solution annealing the block at 1020°C followed by water quenching;
iv. Reheating the beta solution annealed block to 930°C and forging it to a block of dimensions 500 mm X 1450 mm X L;
v. Second beta solution annealing the block at 1000-1080°C followed by water quenching;
vi. Reheating the beta annealed block to 930°C and forging it to a block of dimensions 450 mm X 1600 mm X L;
vii. Subjecting the forged slab to duplex annealing, solutionizing at 910-950°C for 4 hours followed by water quenching and annealing at 700-780°C for 8 hours followed by air cooling;
d. Forging the said process annealed block to a slab of dimensions 200 mm X 1600 mm X 2500 mm L followed by air cooling.

2. The method of manufacturing heavy section titanium slab as claimed in claim 1, wherein the composition of Titan 31 ELI ingots comprises in weight percent: Titanium (Ti) - 88.09-91, Aluminium (Al) - 5.5-6.5, Vanadium (V) - 3.5-4.5, Iron (Fe) - 0.25, Oxygen (O) - 0.13, Carbon (C) - 0.08, Nitrogen - 0.03, Hydrogen - 0.0125, and balance other elements.
3. The method of manufacturing heavy section titanium slab as claimed in claim 1, wherein the beta annealing temperature is maintained at 1020°C for a duration suitable for achieving desired mechanical properties.
4. The method of manufacturing heavy section titanium slab as claimed in claim 1, wherein the second beta solution annealing temperature is maintained at 1020°C for achieving uniform mechanical properties in all three directions.
5. The method of manufacturing heavy section titanium slab as claimed in claim 1, wherein the duplex annealing is carried out to establish an alpha plus beta microstructure, thereby retaining good fracture toughness in the resultant heavy section titanium slab.
6. A heavy section titanium slab of dimensions 200 mm X 1600 mm X 2500 mm L with uniform mechanical properties in all directions longitudinal, long transverse and short transverse.
7. A heavy section titanium slab as claimed in claim 6 qualifies under stringent ultrasonic testing thereby ensuring the quality of the forged titanium slab.