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The invention relates to a process of producing ultra thin light
weight steel sheet with high intensity Y fibre for complicated and sophisticated packing application and the steel sheet produced by the said process.
Y fibre is a metallurgical terminology, which is used world wide to express the orientation of aggregate of crystals in a three-dimensional orientation box. Presence of high intensity of this Y fibre is known to increase the formability of a sheet metal. In case of body center cubic (BCC) metals such as steel when crystals or grains are oriented in such a way that their normal direction is parallel to <111> direction (ND//<111" then those types of grains are called Y grain. When all of these Y type of grains are aligned like a tube in the three dimensional orientation box, they are said to be a fibre. So the Y fibre can be shortly explained by the fact the <111 > typen of orientations arranged in such a way that they form a tube or skeleton line. Hence there type of grains are called Y fibre.

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1. Objective:
The main objective of this work was to produce ultra thin sheet steel with improved Y fibre, which will help to produce light weight steel for packaging purposes, with intricate shapes.
2. Field of Application
The invention provides a method of production of ultra thin (below 180 µm) interstitial free (IF) sheet steel by double cold rolling and double annealing technique. The process parameters within the specified composition range have been optimized to introduce highly improved Y fibre texture. The Y fibre texture is known to improve the formability, which is very much important for deep drawing operation. The current invention is expected to be used to produce light weight and complicated shapes to be used in sophisticated packaging applications.

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3. Background of the invention:
The plate industry consumes large percentage of low carbon steels for packaging purpose. Tin plate is the material used more widely in cans for foods and for other sophisticated applications. The term Tin plate refers to low carbon mild steel sheet with a thin layer of tin coating on each surface of the material,
3.1. Description of invention: 3.1.1 Processing of the steel:
The chemical composition of the steel is: 0.001 ~0.008%C / 0.12 -0.50% Mn / 0.002-0.01%S /0.002-0.028% P /0.001 - 0.007% Si 70.010-0.182% AI /0.0020-0.0120% N/0.001-0.050% Nb/0.002-0-08% Ti (all values in wt %). The steel was controlled hot rolled and a total of 40-85% deformation was given during hot rolling in several passes. The Finish Rolling Temperature (FRT) was kept within 920-1000°C. The hot band was then subjected to first cold rolling (FCR) at room temperature by 60 to 96% followed by first

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batch annealing (FBA) for 6-40 hours at 680-820°C in H2 atmosphere. The first batch-annealed steel was again second cold rolled (SCR) at room temperature to 40-85%, The second cold rolled steel was further second batch annealed (SBA) at 550-8000C for 10-100 minutes in the H2 atmosphere and air-cooling. The sample for electron back scattered diffraction (EBSD) was prepared by manual electropolishing technique. EBSD is a characterization tool which has been used to find out the orientation of the grains or crystals using back scattered diffraction. Crystallographic textures were determined from the mid thickness regions of the sheets using a FEI-Quanta 200 SEM, which is a Scanning Electron Microscope and is used to characterized the microstructure of materials, coupled with an EBSD facility. ODFs (Orientation Distribution Functions) were measured using an in house TSL-OIM software and Q2 = 45° sections (Bunge notation) were determined therefrom.
Texture of a polycrystalline single - phase material is defined by

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the orientation distribution function (ODF) of the crystallities of which the material consists. The position of a crystal in orientation box is defined by three Ruler angle (1,(,(2 were each of them having value 0 to 90°. That mean they are ranging from 0 to 90° in each direction. If we make slice of this 0 to 90° with 50 interval along(2 then we will get 19 such slice. Each of them can be called constant (2 section. This (2 = 45° section is one of the constant sections in the (2 =0 to 90° range. This particular section has been used because it gives strong evidence of the above said Y fibre in BCC rolled steel sheet
3.1.2 Experimental Results'
It is well known that the formability of BCC 'Body center cubic' steel sheets is greatly enhanced by the presence of strong and homogenous Y fibre texture (ND// position while minimum at {lllXllOX Very little difference is observed in the ODF [Fig 2 (c)] after SCR treatment. The nature of the ODF does not change significantly after second cold rolling. The Y fibre texture becomes sharper and uniform after SA Second Annealing treatment [Fig. 2 (d)]. The intensity of the ODF after SA treatment has also been found to increase to 19.5 random, which indicate how strong the texture is. Formation of more uniform ferrite grains in the microstructure after second batch annealing [Fig 1 (b)] as compared to first batch annealing [Fig 1 (a)] probably plays an important role in the development of improved Y fibre texture [Fig 2 (d)] after second annealing. Fig 3

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shows the complete flow chart of the processing route to achieve the present invention,
4. Summary of the Invention:
The present invention claims that a heavy amount (40-85%) of second cold rolling and a second annealing treatment can be applied to an initially cold rolled and annealed Ti + Nb-IF steel sheet to produce improved Y fibre texture in a ultra thin IF sheet steel. This is expected to reduce the weight and increase the formability of the material.
5. Application Areas:
Major steel industries who are interested to produce light weight thin steel sheets for packaging purpose like beverage cans, food cans, toys, sophisticated cans, shielding sheet for cathode ray tube in colored picture tube in Television should be interested-

9 6. benefits:
The present invention will help to produce ultra thim IF sheet steel, which Is expected to reduce the weight as well as Improved the formability to produce lightweight complicated shaped packaging items.

10 We claim:
1) A process of producing ultra thin light weight steel sheet with high intensity Y fibre for complicated and sophisticated packaging application form the composition of
C: 0.001 to 0.008
Mn: 0.12 to 0.50
S: 0-002 to 0.01
P: 0.002 to 0.028
Si: 0.001 to 0.007
Ai: 0.010 to 0.182
N: 0.0020 to 0.0120
Nb: 0-001 to 0.050
Ti: 0.002 to 0.08
And the balance is Fe and all materials are percentage by weight
consisting the steps of subjecting the hot band received from the
hot rolling in several Passes, to the first cold rolling and first
annealing there after to second cold rolling and second annealing
steps.

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2) A process as claimed in claim - 1 wherein the hot rolling is
carried out in the temperature range 920 to 1000°C and the
amount of deformation of hot rolling applied is 40 to 85%.
3) A process as claimed in claim - 1 wherein the amount of
deformation applied to the product in the first cold rolling is 40
to 85%.
4) A process as claimed in claim - 1 wherein the first annealing
temperature and time involved are 680 to 820° C and 5 to 40
hours respectively, in Hydrogen atmosphere.
5) A process as claimed in claim - 1 wherein the amount of
deformation applied to the product during second cold rolling
step is 40 to 85%,
6) A process as claimed in claim -1 wherein the second annealing
temperature and time involved are 550 to 800°C and 10 to 100
minutes respectively in Hydrogen atmosphere.
7) A process as claimed in claims 1 to 6, wherein the thickness of
the steel sheet produced is below 180 µm.
2)
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8) A process as claimed in claims 1 to 7, wherein the final grain
size of the steel sheet lies in the range 8 to 15 µm.
9) An ultra thin light weight steel sheet with high intensity Y fibre
for complicated and sophisticated packing application having
the composition of
C: 0.001 to 0.008
Mn: 0.12 to 0.50
S: 0.002 to 0.01
P: 0.002 to 0.02
Si: 0.001 to 0.007
Al: 0.010 to 0.182
N: 0.0020 to 0.0120
Nb: 0.001 to 0.050
Ti: 0.002 to 0.08%
And the balance of the composition is Fe and all the materials of
the composition are percentage by weight wherein the steel sheet
is produced by the process as claimed in claims 1 to 8.
10) Steel sheet as claimed in claim 9 having uniform and high

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intensity Y fibre, wherein thickness of the sheet is below 180 µm and the grain size of the sheet lies in the range 8 to 15 µm
11) A process of producing ultra thin light weight steel sheet
with high intensity Y fibre for complicated and sophisticated
packing application as substantially described in the body of the
specification and illustrated by the accompanying drawings.
12) An ultra thin light weight steel sheet with high intensity Y
fibre for complicated and sophisticated packing application
as substantially described in the specification and illustrated
by the accompanying drawings.