PROCESS FOR MANUFACTURING TYRE BEAD WIRE

FIELD OF INVENTION:
[001] The present subject matter described herein, relates to a high carbon wire rod that is further drawn to wires for tyre bead application, in particular to, a process for manufacturing 5.3-5.6 mm diameter hot rolled wire and further directly drawing 0.8-1.6 mm diameter wire from the manufactured hot rolled 5.3-5.6 mm diameter wire without intermediate patenting process for tyre bead application.
BACKGROUND AND PRIOR ART AND PROBLEM IN PRIOR ART:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Tyre bead wires are required to be tough and high in durability. In general, high carbon wire rods are extensively used for tyre bead application. Normally 5.5mm diameter hot rolled wire rods being subjected to wire drawing till 3.1mm diameter followed by intermediate patenting in lead bath. Further, drawing of 3.1mm diameter to sections ranging from the diameter of 0.8mm to 1.6mm for various sizes of tyres for automotive applications.
[004] However, the intermediate lead bath patenting consumes a lot of energy as well as environmentally harmful. Therefore, there is an increasing demand to eliminate the intermediate patenting process and develop the 1.6mm diameter wires through direct drawing from 5.5mm diameter wires.
[005] In the prior art, US patent number 4,584,032 A discloses a method of manufacturing high strength steel wire for tyre bead and cord applications. The compositions specified to produce such wires includes: 0.4?C?1.4; 0.1?Mn?1; 0.1?Si?0.4; less than 0.015% by weight sulfur, less than 0.005% by weight aluminum, not more than 3% by weight of any element selected from the group consisting of nickel, chromium, cobalt, molybdenum and copper; and the remainder being iron and incidental impurities; the steel is drawn from a diameter in a range of > 5.5 mm to < 0.5 mm with intermediate patenting operation.
[006] Another prior art, US patent application number 20120064357A1, relates to a process for producing a tyre bead where a carbon steel wire rod containing carbon in a range of 0.61% or more to 0.65% or less in weight percent and having a diameter in a range of 5.5 mm to 6.5 mm is wiredrawn through a single wiredrawing process to a predetermined final wire drawing diameter having a true strain in a range of 2.0 to 4.0 and is turned to a pearlite structure in which ferrite and cementite are drawn in parallel with a narrow interval there between.
[007] The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the invention. However, none of the prior arts process deals with the processing conditions for hot rolling of 5.5 mm diameter wire suitable for directly drawing to 1.6 mm diameter wires without intermediate patenting process.
OBJECTS OF THE INVENTION:
[008] It is therefore the object of the invention to overcome the aforementioned and other drawbacks in prior art processes.
[009] The principal objective of the present invention is to provide a new process for manufacturing a wire rod suitable for direct drawing to tyre bead wire (1.6 mm diameter wires) without intermediate patenting for tyre bead application.
[0010] Another object of the present invention is to optimize the hot rolling parameters including rolling speed, temperature, stelmor conveyor settings to produce 5.5 mm diameter wire rod with desired microstructure that can be easily drawn directly without patenting and breakage.
[0011] Yet another object of the present invention is to develop tyre bead wire (1.6 mm diameter wire) having following properties: break load >= 430 kgs, torsion >= 30 turns to failure.
[0012] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION:
[0013] This summary is provided to introduce concepts related to a process for drawing tyre bead wire (1.6mm diameter wire) directly from 5.5mm diameter hot rolled wire rod. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0014] The present subject matter relates to a process for manufacturing a direct drawn tyre bead wire from 5.5mm hot rolled wire rod without intermediate patenting process. The process comprising steps of: casting steel of thickness approximately 130mm × 130mm billet with following compositions: carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (Si) in a range of 0.2-0.4 wt%, sulphur < 0.015 wt%, phosphorus < 0.015 wt%, nitrogen < 50 ppm, remainder being iron and incidental ingredients. In the next step, the casted steel is soaked at 1200-1220 ° C for 1.5-2.5 hours, and further the soaked steel is hot rolled with speed of 60-90 meters per second (mps) achieving a diameter in a range of 5.3-5.6 mm. The hot rolled 5.3-5.6 mm wire rod is layed in coil form at laying head temperature (LHT) 820-870o C in stelmor conveyor. The coiled 5.3-5.6 mm wire rod is continuously cooled in stelmor conveyor by controlling speed of conveyor and controlling operating setting of a plurality of blowers that are provided underneath the length of the stelmor conveyor; and drawing the steel wire from the diameter 5.5mm to 1.6 mm with reduction of 80-95%.
[0015] In an aspect, diameter of tyre bead wire is in range 0.8 to 2.0mm, preferably 1.6mm.
[0016] In an aspect, steel for hot rolled wire rod for direct drawing of tyre bead wire. The steel comprising carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (S) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron and incidental ingredients.
[0017] In an aspect, the hot rolled wire rod consists of pearlite microstructure that comprising ferrite and cementite. The pearlite microstructure has interlamellar spacing in range of 140-160 microns.
[0018] In an aspect, break load of the 1.6mm diameter wire is in range 430-450 kgs.
[0019] In an aspect, torsion of the 1.6mm diameter wire is in range 30-45 no of turns.
[0020] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0022] Fig. 1 illustrates a flow diagram of a process for manufacturing a direct drawn tyre bead without patenting process, in accordance with an embodiment of the present subject matter;
[0023] Fig. 2 illustrates a scanning diagram of electron microstructure of 5.5 mm diameter wire rod, in accordance with an embodiment of the present subject matter; and
[0024] Fig. 3 illustrates a graphical representation of pearlite spacing and a number of torsion twists to failure, in accordance with an embodiment of the present subject matter.
[0025] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0026] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[0027] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
[0028] The present subject matter relates to a process for manufacturing a 1.6mm wire from 5.5mm hot rolled wire rod without intermediate patenting for tyre bead application. The composition of 5.5mm hot rolled wire rod consist: carbon in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (Si) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron (Fe) and incidental ingredients. In the present process, first 5.5mm hot rolled wire rod is prepared and temperature of the prepared or casted 5.5mm hot rolled wire rod is optimized to direct drawing of 1.6mm wire. In the first step, casting steel of thickness >130mm × 130mm with following composition carbon in a range of 0.71-0.85 wt%, manganese in a range of 0.5-0.7 wt%, chromium in a range of 0.12-0.25 wt%, silicon in a range of 0.2-0.4 wt%, sulphur < 0.015 wt%, phosphorus < 0.015 wt%, nitrogen < 50 ppm, rest iron and incidental ingredients; soaking the casted steel at 1200-1220 ° C for 1.5-2.5 hours; hot rolling the steel rod with speed of 60-90 meters per second (mps) achieving a diameter in a range of 5.3-5.6 mm and laying the coil form of 5.3-5.6 mm hot rolled wire rod at laying head temperature at 820o-870o C in stelmor conveyor. Further, cooling continuously the coiled form 5.3-5.6mm hot rolled wire rod by controlling parameters of the stelmor conveyor. The conveyor speed is in range 35-35 meter per minute (mpm) and blower opening as blower 1>70%, blower 2, 3, and 4 >80%, blower 5 and 6> 50%; and drawing the steel wire from the diameter 5.5mm to 1.6 mm with reduction of 80-95%. At the end providing stress relieving and Cu coating on the obtained 1.6mm diameter wire.
[0029] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0030] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0031] Fig. 1 illustrates a flow diagram of a process 100 for manufacturing a direct drawn tyre bead wire without patenting process. The process 100 comprises various steps: at step 104, casting a steel of thickness >130mm × 130mm with following composition: carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (S) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron and incidental ingredients.
[0032] The steel is refined in BOF (Basic Oxygen Furnace) converter and casted in continuous casting strands. In some embodiment, the steel can be manufactured in other furnaces as per requirement.
[0033] At step 108, the steel is soaked at temperature in range 1200-1220 ° C for 1.5-2.5 hours. At step 112, the soaked steel is hot rolled at 1000-1100 ° C with reduced thickness achieved as the diameter in a range of 5.3 mm-5.6 mm. The speed is maintained at 60-90 meters per second (mps). The hot rolling of the steel is done by 25-28 stands. The number of the stands can be varied as per the requirement keeping the reduction of steel up to the diameter in a range of 5.3 mm-5.6 mm.
[0034] At step 116, the hot rolled steel rod is laid at a stelmor conveyor in coil form at laying head temperature (LHT) in range 820-870 ° C. At step 120, the coil formed hot rolled wires are cooled continuously with a plurality of blowers underneath over the length of the stelmor conveyor. The speed of stelmor conveyor ranges between 35-45 meter per minute (mpm) and blower openings in the stelmor conveyor is as blower 1> 70% open, blowers 2, 3 and 4 > 80% open, blowers 5 and 6 > 50% open.
[0035] At step 124, the diameter in a range of 5.3 mm-5.6 mm hot rolled wire is suitable for wire directly drawing in a single step without intermediate patenting to 0.8-2.0mm, preferably 1.6 mm diameter thick tyre bead wire (alternatively it may be referred as 1.6mm diameter wire). The tyre bead wire with 1.6 mm diameter are produced to meet the required strength and torsional ductility requirement for tyre bead application.
[0036] At the end stress relieving and copper (Cu) coating is applied on the directly drawn tyre bead wire.
[0037] In another embodiment of the present subject matter, steel for hot rolled wire rod for direct drawing of tyre bead wire comprising: carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (S) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron and incidental ingredients.
[0038] The preferred composition of the steel hot rolled wire rod can be shown in Table 1.

C Mn S P Si N Cr Fe + incidental
0.76-0.78 0.54-0.60 0.010-0.015 0.015-0.020 0.25- 0.30 0.004-0.006 0.17-0.20 Rest

Table 1 (all in wt.%)
[0039] The final property, namely break load and torsional ductility, of 1.6 mm diameter wire depends on both the composition as well as microstructure of hot rolled wire. The composition in Table 1 is preferred as it gives the right combination of strength and microstructure.
[0040] The strength of the steel is dependent on the composition as well as the strain accumulation during cold drawing operation. In addition, to this the final property, the break load and torsion, of the 1.6 mm diameter wire also depends on the microstructure evolution during the wire drawing operation, which is again governed by the wire microstructure.
[0041] The hot rolled wire consists of fully pearlite microstructure. Pearlite is a phase in steel that contains alternate lamellae of ferrite and cementite (Fe3C) phases. The length between two cementite or ferrite phase is known as the interlamellar spacing. The interlamellar spacing depends on the cooling rate in the stelmor conveyer. In the present subject matter optimized cooling rate is provided to control the interlamellar spacing. The faster the cooling rate, finer is the interlamellar spacing obtained. The alignment and the interlamellar spacing of pearlite in the hot rolled wire plays an important role in microstructural evolution during subsequent wire drawing operation. During drawing operation, deformation of pearlite occurs by realignment in the direction of drawing and subsequently by deformation of cementite and ferrite in the microstructure.
[0042] If pearlite lamellae are aligned parallel to the drawing axis, the deformation becomes difficult. If the pearlite is aligned perpendicular to the drawing axis, the deformation process is easier. There is lot of strain accumulation, which in turn affects the final ductility of wires. It is difficult to control the alignment of pearlite in an industrial process.
[0043] It is easier to obtain a finer or coarser interlamellar spacing by modifying the stelmor cooling process. However, an optimum interlamellar spacing is required to ensure final ductility in 1.6 mm diameter directly drawn wires. A too smaller spacing lead is provided to cementite dissolution by breakage of cementite plate and generation of huge stresses in the ferrite matrix, thereby reducing the ductility of wire, especially torsion. A coarser pearlite does deform easily during drawing, leading to wire breakages and loss of ductility, as shown in Figure 3.
[0044] In accordance with an embodiment of the present subject matter, the interlamellar spacing in the hot rolled wire rod should be within a band of 140-160 microns for better drawability and final properties of 1.6mm directly drawn wire.
[0045] The obtained mechanical properties of the directly drawn wires of 1.6 mm diameter or tyre bead wire obtained by means of the process (100) are shown in Table 2.
Break Load (Kgs) Torsion (No. of turns to failure)
430-450 30-45

Table 2
[0046] For example, the above-mentioned process 100 for making hot rolled wire suitable for direct drawing to 1.6 mm diameter wire and its properties can be validated by the following examples. The following examples should not be construed to limit the scope of invention.
[0047] Steel with the optimum chemical composition mentioned in (Table 1) was produced and processed. The steel was made in BOF converter without any vacuum treatment and cast into billets of >130 mm x 130 mm thickness. The material was then soaked at 1200 ° C for about 2 hours in reheating furnace and hot-rolled into 5.5 mm diameter wires. The speed maintained was 74 mps. The rolling temperature was maintained at 1020 ° C and laying head temperature was 850 ° C. The stelmor conveyor speed was 40 mpm and blower settings were as follows: blower 1 – 74% open, blower 2 and 3 – 85% open, blower 4 – 80% open and blower 5 and 6 – 50% open. The hot-rolled material was subsequently drawn directly to 1.6 mm diameter wires without any intermediate patenting treatment followed by stress relieving and copper (Cu) coating.
[0048] Samples were tested for mechanical properties and assessed for microstructural details.
[0049] FIGS. 2 shows the microstructure of the 5.5 mm diameter hot rolled wire, the following mechanical properties have been obtained for samples following above mentioned process as shown in Table 3
Samples Average Interlamellar Spacing in 5.5 mm wire (microns) Break Load of 1.6 mm Wire (kgs) Torsion of 1.6 mm Wire (no. of turns to failure)
Specimen 1 145 432 38
Specimen 2 153 429 40
Specimen 3 148 433 41
Specimen 4 153 431 39
Specimen 5 151 435 40
Specimen 6 149 432 38

[0050] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0051] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0052] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

We claim:

1. A process (100) for manufacturing tyre bead wire, the process (100) comprising steps of:
casting (104) steel;
soaking (108) the casted steel at 1200-1220 ° C for 1.5-2.5 hours;
hot rolling (112) the soaked steel at 1000-1100 ° C to achieve a wire rod with diameter in a range of 5.3-5.6 mm;
laying (116) the hot rolled wire rod at a stelmor conveyor in coil form at laying head temperature (LHT) range of 820-870 ° C;
cooling (120) the coil of the hot rolled wire rod continuously in the stelmor conveyor; and
drawing (124) directly the tyre bead wire from the 5.3-5.6mm diameter hot rolled wire rod.

2. The process (100) as claimed in claim 1, wherein the process further comprising:
applying stress relieving and copper (Cu) coating on the drawn tyre bead wire.
3. The process (100) as claimed in claim 1, wherein the steel composition: carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (S) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron and incidental ingredients.
4. The process (100) as claimed in claim 1, wherein speed of the hot rolling of the soaked steel is in range 60-90 meter per second (mps) and the hot rolling of the steel is done by 25-28 stands.
5. The process (100) as claimed in claim 1, wherein the cooling (120) the hot rolled wire rod in the stelmor conveyor further comprising:
controlling speed of the stelmor conveyor in range between 35-45 meter per minute (mpm); and
opening blower 1 > 70%, blower 2, 3, and 4 > 80%, blower 5 and 6 > 50% of the stelmor conveyor.
6. The process (100) as claimed in claim 1, wherein the hot rolled wire rod consists of pearlite microstructure having interlamellar spacing in range 140-160 microns.

7. The process (100) as claimed in claim 1, wherein diameter of the tyre bead wire is in range 0.8 to 2.0mm, preferably 1.6mm.

8. The process (100) as claimed in claim 1, wherein the tyre bead wire has break load in range of 430-450 kgs.

9. The process (100) as claimed in claim 1, wherein torsion failure value of the tyre bead wire is in range 30-45 turns.

10. A steel for hot rolled wire rod for direct drawing of tyre bead wire, the steel comprising:
carbon (C) in a range of 0.71-0.85 wt%, manganese (Mn) in a range of 0.5-0.7 wt%, chromium (Cr) in a range of 0.12-0.25 wt%, silicon (S) in a range of 0.2-0.4 wt%, sulphur (S) < 0.015 wt%, phosphorus (P) < 0.015 wt%, nitrogen (N) < 50 ppm, remainder being iron and incidental ingredients.
11. The steel as claimed in claim 1, wherein the hot rolled wire rod consists of pearlite microstructure that comprising ferrite and cementite, the pearlite microstructure has interlamellar spacing in range of 140-160 microns.
12. The steel as claimed in claim 1, wherein diameter of the tyre bead wire is in range 0.8-2.0mm, preferably 1.6mm.
13. The steel as claimed in claim 1, wherein break load of the tyre bead wire is in range 430-450 kgs.
14. The steel as claimed in claim 1, wherein torsion value of the tyre bead diameter wire is in range 30-45 turns.