FIELD OF THE INVENTION:
This invention relates to carbide filled former inserted grinding rolls and bull ring segments and a process for the preparation thereof.
This invention also relates to carbide hard facing of Ni-Hard grinding rolls and bull ring segments and a process for the preparation thereof.
This invention further relates to high strength and wear resistant grinding rolls and bull ring segments for bowl mill with enhanced performance and operational life.
BACKGROUND OF INVENTION:
The efficiency of Pulveriser is one of the major parameters in most of the coal fired thermal power plants, the performance and operational life of which dictates the total power plant efficiency. There are three vital parameters of Pulveriser operation that determine the efficiency of the grinding media which is used to crush coal lumps into the fines and then forwarded to the boiler section viz the desired size reduction of the coal, uniform flow rate and the higher classifier efficiency. Grinding rolls and bull ring segments are subjected to aggressive abrasion during the course of coal pulverization due to higher ash

and silica content in coal. This leads to faster wear of grinding rolls and soon reaches to a situation where it has to be replaced. This involves the plant shutdown and ultimately affects the plant efficiency. Ever since the advent of power plants, the aim has always been to achieve high wear life of grinding rolls and bull ring segments as it becomes one of the major contributor in determining the plant efficiency. However, in the present Indian scenario the increasing percentage of ash and silica content in coal has become a major concern as it has high deteriorating effect on the abrasive resistance of grinding media. Hence it became inevitable to look for innovative means of achieving better strength and abrasive resistance of grinding rolls and bull ring segments. A few researchers have reported the significant achievements in developing the high strength wear resistance grinding rolls which are as follows:
US Patent application US RE 39998E (Revised) to Hubert Francois of Magotteaux International S.A. discloses a composite wear component which has been produced by casting, which consists of metal matrix whose working surface or faces include very high resistance inserts made of ceramic pad. These ceramic pads are fabricated with a homogeneous solid solution of 20 to 80% of Al2O3 and 80 to 20% ZrO2 by weight percentages. Then this pad being impregnated with a liquid metal during the casting. The ceramic pad is produced from an aggregate of ceramic grains having particle range of 0.7mm to 5.5mm. These grains are made by electro fusion, by sintering, by flame spraying or by any other process allowing the two constituents to fuse. The adhesive used for

binding these grains can be made of silicate or in the form of epoxy resin and is preferably between 2 to 3% by weight.
US Patent application no. US 008147980 B2 (2012) to SudhirVamanBhide of AIA industries, Ahmedabad, India discloses a process of manufacturing metal matrix ceramic composite (MMCC) wear part. This MMCC becomes part of wear portion which is impregnated by metal (SG Iron), wherein the ceramic cake comprises of Al2O3, ZrO2, fine ceramic powder (Al2O3), any one of the carbide materials such as boron carbide, silicon carbide and tungsten carbide and the sodium silicate binder. All the above mentioned powders and binders were mixed in a flexible holder and the mixture was hardened to form a ceramic cake. In order to provide the adequate strength, cake is heated to a temperature between 80-220ºC. The ceramic cake was reinforced with the SG iron and finally shaped into the grinding roll of bowl mill. It was observed that the life of the grinding roll improved substantially (quantitative value of the operational life has not been mentioned in this patent.)
Gronvall et al. (EP 2512680 A1 (2012) ) developed the bimaterial elongated insert member for the grinding roll. The insert member comprised a core of a first material having a first hardness, and the body of second material having second hardness which enclosed the core. The first hardness was greater than the second hardness. The advantage is that the reinforced insert members will be less likely to dislodge from the grinding roll due to the elasticity created between

the insert member and the grinding roll. In a similar fashion, Mirchandani et al. (US 0011965 A1) (2011), developed the wear resistance metal matrix composite which comprises the inorganic particles dispersed in a matrix material. Melting temperature of the inorganic particle was being greater than the melting temperature of the matrix.
Poncin et al. (US 7513295 B2 (2009)) relates to the development of cast parts with enhanced wear, abrasion and impact resistance at a financially acceptable price and also discussed about the method of their production. The method comprised of placing two or more powdered raw materials in the mold and then after adding a molten casting metal to the casting mold. The molten casting metal generates the in-situ chemical reaction between the powders and finally provides the particulate porous conglomerate. The powder raw material selected from the group consisted of ferro-alloys, oxides, nickel, nickel alloy, iron alloy, titanium alloy etc.
Francois et al. (US 6399176 B1 (2002)) developed the composite wear component by centrifugal casting in which ceramic pad (in the form of a honeycomb structure) is reinforced in the molten metal. The wear component produced by centrifugal casting consists of a metal matrix whose wear surface comprises inserts (made of ceramic material, 20-80 wt. % Al2O3 and 80-20 wt. % ZrO2, Particle size range: 0.7-5.5 mm)) which is having good abrasion resistance properties. The idea of using Aluminium oxide and zirconium oxide having

relatively different properties was to adjust the hardness, toughness and thermal expansion coefficient of the composite ceramic. Zirconium dioxide has the advantage of having an expansion coefficient which is close to that of metal. In addition, it contributes to good toughness, which reduces the risk of breakage. In addition, ZrO2 particle present in the Al2O3 increases the resistance of the Al2O3 to cracking and hence increases the toughness greater than that of each component considered individually (namely ZrO2 or Al2O3). Various geometries were proposed in their invention in order to solve the infiltration of the liquid metal within the ceramic phase. For the efficient infiltration of the liquid metal and to reduce the risk of propagation of the crack, honeycomb type of pad was fabricated. Finally, Ceramic inserts (hardness: 1600 Hv, expansion coefficient:(~8 * 10-6/K) reinforced with the pig iron matrix (hardness: 750 Hv) and thus composite wear component was fabricated.
US 8540036 B2 (2013) to James L, Overstreet, relates to the development of ultra hard sintered carbide particles in hard facing for earth boring bit. The ultra hard particles consist of tungsten carbide grains, Cobalt and Vanadium. The ultra hard particles are dispersed within a matrix metal of iron, nickel or alloys thereof. The composition may also have sintered tungsten carbide particles of a larger size than the ultra hard particles. The ultra hard particles have a greater hardness than the sintered tungsten carbide particles.

Krizan et al., US 4,923,511 (1990), have disclosed a hard facing powder to be deposited by plasma transferred arc welding on a substrate. The hard facing powder includes a plurality of different types of tungsten carbide particularly W2C and WC-Co, within a matrix alloy of Carbon 0.017-0.52% by weight, Silicon 4.3-4.7 % by weight, Boron 2.7-3.3 % by weight, Iron 0.27-0.4% by weight and balance Nickel. The total content of WC is minimum of 50% by weight.
Grover et al., US 4,339,272 (1982), have developed tungsten carbide-based hard metal comprising of 75~97 weight % tungsten carbide and the balance is binder having a composition 14 weight % manganese, 2½% carbon, 5% nickel and balance iron instead of the conventional binder Cobalt.
Apart from the above, there are a few more patents EP 0234026 A2 (1987), EP 0192972 A1 (1986), US 4604781 (1986), US 4610401 (1986), US 4389767 (1983), US 3859057 (1975), US 3071489 (1963),US 6782958 B2,US 6,375,706 B2, US 7,666,244 B2 which discuss about the development of high wear resistance materials, are incorporated herein by references.
However, the need exists in the industry to provide grinding rolls and bull ring segments having very high strength and high wear resistance, which lead to enhanced performance and higher operational life so as to ultimately achieve enhanced efficiency of the power plant.

OBJECTS OF THE INVENTION:
It is therefore an object of this invention to propose process of manufacture of carbide filled former inserted grinding rolls and bull ring segments which has the following advantages:
• Easier & Cost effective.
• Higher yield
It is a further object of this invention to propose the process of carbide hard facing of Ni-Hard grinding rolls and bull ring segments which has the following advantages:
• Flux cored arc welding methodology with specialized process of
introducing shielding gas as well as the carbide grits in the steam.
Another object of this invention is to propose carbide filled former inserted grinding rolls and bull ring segments having enhanced performance and higher operational life, to achieve enhanced efficiency of the power plant.
Yet another object of this invention is to propose carbide filled former inserted grinding rolls and bull ring segments, which are cost effective.

These and other objects and advantages of the invention will be apparent to a reader on reading the ensuing description, in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
This invention relates to carbide filled former inserted grinding rolls and bull ring segments and also relates to tungsten carbide hard faced Ni-Hard rolls and bull ring segments with enhanced performance and operational life which will ultimately lead to higher plant efficiency. This can be achieved by fabricating the formers and brazing the carbide grits to former tubes and in turn placed in the centrifugal die where the initial layer of high chrome/ Ni-Hard will be poured followed by inner layer of softer grey iron.
In another embodiment, it can be achieved by making a centrifugally cast tri-metallic roll having hard faced WC embedded (Flux cored arc welding methodology with specialized process of introducing shielding gas as well as the carbide grits in the steam) Ni-Hard/ High Chrome outer layer and soft-core/ SG Iron inner layer. Similarly, Bull Ring Segments are to be cast by CO2 sand moulding followed by hard facing by carbides through flux core arc welding methodology preferably with sintered Tungsten Carbide. Then the inner layers of rolls need to be machined for blue matching test.

Moreover, the cost effectiveness is also calculated to strike a balance between the operating performance as well as efficiency and the final price. A suitable flux will be used to achieve proper bonding between the grit and MS sheet/ tube followed by sintering at requisite temperature.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure-1 [Carbide Filled Former Inserted Grinding Roll (Schematic View)] Figure-2 [Cross Sectional View of the Former Assembly for Grinding Roll] Figure-3 [Bull Ring Segment Assembly (Schematic View)]
Figure-4 [Schematic View of Brazed WC Grit Tubes Welded on MS Sheet] Figure-5 [Side View of the Bull Ring Segment Assembly (Schematic)]
DETAILED DESCRIPTION OF THE INVENTION
According to this invention is provided carbide filled former inserted grinding rolls and bull ring segments and a process for the preparation thereof.
This invention also relates to carbide hard facing of Ni-Hard grinding rolls and bull ring segments and a process for the preparation thereof.

In accordance with this invention is provided high strength and high wear resistant grinding rolls and bull ring segments with enhanced performance and higher operational life.
In accordance with this invention is further provided a process for the production of high strength and high wear resistant grinding rolls and bull ring segments.
The process according to the invention comprises the following steps:
• Selection of suitable composition and size of the tungsten carbide
grits/ tool bits having higher hardness, toughness, strength and wear
resistance. Also these materials should have comparable density, wet ability
and coefficient of thermal expansion with Ni-Hard, High Chrome and Cast
Iron/ SG Iron metal;
• Brazing of these carbide grits into MS tubes of fitting diameter and
length with suitable flux. Alternatively, small carbide bits of length 10-20mm
shall be fitted into the grooves created in the skeletal/ cage MS structure and
those will be projected inwards from the centrifugal die outer edge while
placing in it. As another alternative, small carbide tool tips (scrap tips) will be
stripped off the gold coloured Titanium Nitride CVD coating by leaching
followed by application of suitable flux and then Nickel Chrome Boron Silicon
brazing powder while heating with a torch which melts the powder and

ultimately brazes the WC (5mm size formed in U shape) to the steel plate that will be placed in the centrifugal die for further pouring of Ni-Hard and soft core grey iron where as in case of bull ring segment the tool bits (4mm size) will be arranged very close to each other on a steel plate followed by the same treatment as that of rolls and then will be placed in a mould. Subsequently Ni-Hard metal will be poured to bond with brazed material;
• These WC carbides along with the suitable flux are subjected to sintering at suitable temperature;
• Therefore, the initial steps of the process lead to the fabrication of desired former with MS sheet for insertion of the brazed tubes into the gap between the two concentric sheets by welding on either ends for grinding rolls. Similarly welding of brazed tubes to the properly bent MS sheet in case of BRS. This is followed by pouring of Ni-Hard/ High Chrome metal into the die containing the above mentioned fabricated former with carbide grits followed by pouring of soft core grey cast iron/ SG Iron as the case may be to obtain tri metallic layer with inserted carbide grits within the outer layer of the grinding rolls;
• Prior to pouring of initial Ni-Hard/ High Chrome iron into the die having the MS former with associated WC grits, it has to be preheated to a temperature of 300 to 3500 C, preferably 3500 C, for a period of 1 hour to 1 ½ hours, preferably 1 hour.

In accordance with an embodiment, the grinding roll is made by pouring Ni-Hard/ High Chrome Roll with softer cast iron material as the inner layer using centrifugal casting. Then the outer working surface of the roll is initially given a special coat of high chrome mixed flux (single layer of 2-3 mm, i.e. at the center of the working surface of roll / bull segment 3mm and gradually tapering down to 2mm on either ends height wise for roll and length wise for bull ring segments respectively) with suitable composition, followed by 2-3mm thickness of pre-sintered Tungsten carbide coating on it. Both the layers are formed using specialized process of flux cored arc welding methodology. Prior to hard facing both roll as well as bull ring segment is knurled on the working surface with depth up to 2-3 mm and width of 10-20mm. In case of first layer the core wire composition is as follows Carbon: 4-6%, Silicon: 0.8-1.2 % Manganese: 1.0-1.2% Chromium: 25-30%and balance Iron with an average hardness ranging from 56 to 65 HRC. While doing the flux cored wire welding with above composition the following shielding gas is used: the Argon / CO2 blend of 75% Argon and 25% CO2. Then the second layer is done with a core wire composition of Carbon: 5-7%, Silicon: 0.9-1.1 % Manganese: 0.2-0.3% Chromium: 20-24% Vanadium: 0.7-0.9%, Niobium: 6.0-7.0%, Tungsten: 1-2 %, Molybdenum: 5.5-6.5% and balance Iron. While doing the flux cored wire welding with above composition the following shielding gas is used: the Argon / CO2 blend of 80% Argon and 20% CO2. The injection of shielding gas is done at angle of 30-450 in both the layers, but in case of second layer sintered

tungsten carbide grits of size 1-1.5mm are introduced through a specially designed hopper. This will be Quadra-metallic layer component.
In case of Bull Ring Segments, the fabricated MS sheet along with Carbide grits need to be properly positioned in the mould cavity and preheated to a temperature of 2500C to 3500C, preferably 3500C, and then high chrome/ Ni-Hard metal poured into it to take the shape of BRS with the grits getting arranged on the working surface.
In accordance with an embodiment, the Bull Ring Segments are made using static method with High Moly Ni-Hard/ High Chrome metal followed by suitable stress relieving cycle. Then double layer coating with final layer of tungsten carbide is done as mentioned in case of rolls above with 2-3mm each thickness on the working surface. This will be a Tri-metallic layer component.
Grinding Rolls will be poured using centrifugal die casting and BRS will be poured using static CO2 moulding methodology.
The process involves the use of Tungsten Carbide drill bits or grits of desired composition which are chosen to form the hard facing layer of the grinding roll and bull ring segments.

The present invention has emerged from the idea of using scrap Tungsten Carbide drill bits as well as custom made Tungsten Carbide grits of varied compositions from the market to be used as a part of integrated embedded portion of the hard faced matrix (either high chrome/ Ni-Hard) in the outer layer of the grinding roll or bull ring segments while in case of rolls there will be additional inner layer of soft core cast iron/ SG iron.
The idea is to initially fabricate a mild steel former with two concentric sheets matching the exact size and shape of the desired outer hard layer of the grinding roll wherein the brazed WC embedded MS tubes will be welded on either side to the inner as well as outer layer of the concentric former sheets, thereby binding the two sheets in position. Also the volume of the gap filled by these brazed WC Tubes is approximately 50%. The inner portion of the grinding roll is filled by pouring either grey iron or SG iron as shown in the Figure-1. An example of a grinding roll includes a MS Former with two concentric sheets of 3-5mm thickness with 10 as inner layer and 11 as outer layer. These sheets are initially supported and positioned by perpendicularly welded sheets 14 of 1.5-3 mm thick. Subsequently, the brazed tungsten carbide embedded MS tubes 12 of thickness 0.5-1.5 mm are chosen for welding on either ends to the former inner as well as outer layers respectively.
In case of Bull Ring Segments, a MS sheet is bent to the exact shape of the working surface of the BRS and these WC brazed tubes are welded to the sheet

in honey comb form perpendicularly downwards as shown in the Figure-2. An MS sheet 22 of desired size and shape to match to the outer working surface of the BRS is chosen and the brazed WC embedded MS tubes 20 are welded perpendicularly downwards to the sheet.
In accordance with an embodiment, for the production of grinding roll, a liquid metal 15 selected from high chrome metal and Nickel-hard metal is poured into the gap between the two concentric sheets of the former which is already half filled by the brazed WC tubes welded on either end to the concentric layers of the former exactly positioned in the desired hard layer portion of the grinding roll the outer layer of which exactly matches to the inner portion of the centrifugal die. Prior to pouring, the total MS former assembly along with centrifugal die is preheated to a minimum temperature of 300 0C for a minimum period of 1 hour. Then the die is kept at minimum rotating speed and pouring of liquid metal selected from high chrome or Nickel-hard metal is initiated while gradually increasing the speed of rotation. Then after giving sufficient lag time, a metal selected from soft core/ grey iron metal or SG iron 13 is poured into the inner layer of the grinding roll while the die is still in rotating condition with gradual increase of speed till completion of pouring. The die rotation is continued till the metal starts solidifying. After allowing the roll to almost solidify in the die, the spinner is stopped and at halt position the roll is removed red hot from the die and allowed to cool slowly by putting it in sand pit for 6-7 days. The soft core ID machined to get the desired dimension.

The lag time, pouring temperature, the spinner speed of rotation etc. are adjusted according to the metal, i.e. high chrome or Ni-Hard metal.
Similarly, the lag time, pouring temperature, the spinner speed of rotation etc. are adjusted to suit to SG Iron metal.
In accordance with an embodiment of Bull Ring Segment, the MS sheet along with the downwardly welded WC brazed tubes is positioned in the mould cavity in such a way that after pouring of high chrome metal or Nickel-Hard metal, it forms the outer layer of BRS. CO2 Sand Moulding is adopted for making the mould and the MS sheet along with the Brazed tubes is carefully positioned by using suitable chaplets. The mould cavity is adequately painted with spirit based Zircon paint followed by preheating the mould to a temperature of 250 0C.
In a typical embodiment, a tungsten carbide drill bit composition chosen for hard facing, includes carbide phase from about 50% to 80% by weight of the hard facing composition of a combination of 80 to 200 mesh macro crystalline tungsten carbide and 80 to 200 mesh crushed cast carbide, the crushed carbide ranges between 5% to 50% of the total weight of the carbide phase. This is mixed with a binder alloy comprising about 20% to about 50% by

weight of hard facing composition. Sometimes cemented tungsten carbide is also used.
However, the Tungsten Carbide hard facing layer constitutes an admixture of
drill bits/ grits of all available compositions with all possible ratios.
The typical composition of the SG Iron metal is given below:
Carbon: 3.0-3.4%, Silicon: 2.3-2.5%, Manganese: 0.2% (max), Phosphorous:
0.03 %( Max) and Sulphur: 0.01 (max) and residual Magnesium: 0.05-0.08%
The expected mechanical properties of SG Iron cast component is as given
below:
Tensile Strength: 414 N/mm2, min, Yield: 276 N/mm2, min and % Elongation:
18 min (L=50mm).
The microstructure of SG Iron component is expected to be essentially ferritic
and contain no massive carbides and having 90% Type I and type II graphite as
per ASTM A 247 plate I.
The finally fabricated grinding roll along with bull ring segment assembly will
be as shown in Figure 5.
In accordance with an embodiment, the manufacture of grinding rolls is made using Quadra-metallic layer methodology. In this case initially bi-metallic layer of roll is made using centrifugal casting method where in the outer layer is made of Ni-Hard metal (Type II/ IV) or High Chrome metal and the inner layer is made of soft core, i.e grey cast iron. Subsequently the working surface of the

grinding roll is initially coated with single layer of high chrome mixed with suitable flux followed by second layer of coating with sintered tungsten carbide grits embedded into it while doing the flux cored wire welding where each layer will have a thickness of 2-3mm.
In accordance with a further embodiment, the manufacture of bull ring segments is made using Tri-Metallic layer methodology. In this case initially, Bull Ring Segments of desired dimensions will be poured using static method with CO2 moulding. Subsequently the working surface of the bull ring segment is initially coated (using flux cored arc welding) with single layer of high chrome mixed with suitable flux followed by second layer of coating with sintered tungsten carbide grits embedded into it while doing the flux cored wire welding where each layer will have a thickness of 2-3mm.

WE CLAIM:
1. A process for the manufacture of grinding rolls comprising the steps of fabricating a mild steel (MS) former with two concentric outer and inner layer of size and shape matching that of the outer layer of the grinding roll, welding brazed tungsten carbide (WC) to the inner side of the outer layer and outer side of the inner layer, thereby holding the layers in position, to form the former assembly, preheating the former assembly and pouring a liquid metal selected form high chrome metal and Nickel-hard metal into the gap between the outer layer and inner layer by centrifugal die casting, whereby the speed of rotation of the die is gradually increased, while pouring the liquid metal, followed by a lag period and pouring a metal selected from soft core/grey iron metal and SG iron into the inner layer of the former assembly, while the die is rotating and the speed of rotation is gradually increased, till the metal solidifies, removing the former assembly from the die and allowing the same to cool to obtain the grinding rolls.
2. A process for the manufacture of Bull Ring Segments (BRS), comprising the steps of bending a MS sheet to match the shape of the working surface of the BRS, welding brazed tungsten carbide (WC) to the sheet perpendicularly downwards therefrom, followed by positioning the MS sheets with the brazed WC embedded MS tubes in the mould cavity of a die, for static CO2 sand moulding, preheating the MS sheets and pouring a liquid metal selected from high chrome metal and Nickel-hard metal in such a way that it forms the outer layer of BRS.
3. A process for the manufacture of Quadra metallic layered Rolls, comprising the steps of initially making a bi-metallic layer of roll using centrifugal casting method where in the outer layer is made of Ni-Hard metal (Type II/ IV) or High Chrome metal and the inner layer is made of soft core, i.e

grey cast iron. Subsequently the working surface of the grinding roll is initially coated with single layer of high chrome mixed with suitable flux followed by second layer of coating with sintered tungsten carbide grits embedded into it while doing the flux cored wire welding where each layer will have a thickness of 2-3mm.
4. A process for the manufacture of tri metallic layered Bull Ring Segments, comprising the steps of initially making a Bull Ring Segment of desired dimensions poured using static method with CO2 moulding. Subsequently the working surface of the bull ring segment is initially coated (using flux cored arc welding) with single layer of high chrome mixed with suitable flux followed by second layer of coating with sintered tungsten carbide grits embedded into it while doing the flux cored wire welding where each layer will have a thickness of 2-3mm.
5. The process as claimed in claim 1, wherein said former assembly is preheated to a temperature of 300 to 350ºC, preferably 350ºC.
6. The process as claimed in claim 2, wherein said MS sheets with the WC brazed tubes are preheated to a temperature of 250 to 350 ºC, preferably 350ºC.
7. The process as claimed in the preceding claims wherein WC may be present as WC brazed into MS tubes, WC drill bits, WC grits, WC bits and WC tool tips, and mixtures thereof.
8. The process as claimed in claim 7, wherein WC bits of length 10-20 mm are brazed into MS tubes with a suitable flux, to obtain the WC brazed MS tubes.

9. The process as claimed in claim 8, wherein said drill bit comprises about 50 to 80% by weight of the composition, of a tungsten carbide phase and about 20 to 50% by weight of a binder alloy.
10. The process as claimed in claim 9, wherein said WC phase comprises 80 to 200 mesh macro crystalline tungsten carbide and 80 to 200 mesh crushed cast carbide, the crushed carbide being between 5% to 50% of the total weight of the carbide phase.
11. The process as claimed in claim 1 & 2, further comprising coating the outer surface of said grinding roll, or BRS with a single/double layer of high chrome mixed with suitable flux followed by coating with pre-sintered tungsten carbide.
12. The process as claimed in claim 11, wherein said chrome layer has a thickness of about 1 mm.
13. The process as claimed in claim 11, wherein said tungsten carbide layer has a thickness of about 2-3 mm.
14. The process as claimed in claim 3, wherein the first layer is built up by flux cored arc welding process where the core wire has a composition of Carbon: 4-6%, Silicon: 0.8-1.2 % Manganese: 1.0-1.2% Chromium: 25-30%and balance Iron.
15. The process as claimed in claim 14, wherein it uses a shielding gas of the Argon / CO2 blend of 75% Argon and 25% CO2 impinged at an angle of 30-450.
16. The process as claimed in claim 14, wherein the thickness of weld layer is between 2-3 mm, i.e. at the center of the working surface of roll it is 3mm and gradually tapering down to 2mm on either end height wise.

17. The process as claimed in claim 3, wherein the second layer is built up by flux cored arc welding process where the core wire has a composition of Carbon: 5-7%, Silicon: 0.9-1.1 % Manganese: 0.2-0.3% Chromium: 20-24% Vanadium: 0.7-0.9%, Niobium: 6.0-7.0%, Tungsten: 1-2 %, Molybdenum: 5.5-6.5% and balance Iron.
18. The process as claimed in claim 17, wherein it uses a shielding gas of the Argon / CO2 blend of 80% Argon and 20% CO2 impinged at an angle of 30-450
19. The process as claimed in claim 17, wherein the thickness of weld layer is between 2-3 mm, i.e. at the center of the working surface of roll it is 3mm and gradually tapering down to 2mm on either end height wise.
20. The process as claimed in claim 4, wherein the bull ring segment is made using CO2 sand moulding followed by suitable heat treatment/stress relieving cycle.
21. The process as claimed in claim 4, wherein the first layer is built up by
flux cored arc welding process where the core wire has a composition of
Carbon: 4-6%, Silicon: 0.8-1.2 % Manganese: 1.0-1.2% Chromium: 25-30%and
balance Iron.
22. The process as claimed in claim 21, wherein it uses a shielding gas of the Argon / CO2 blend of 75% Argon and 25% CO2 impinged at an angle of 30-450.
23. The process as claimed in claim 21, wherein the thickness of weld layer is between 2-3 mm, i.e. at the center of the working surface of bull ring segment it is 3mm and gradually tapering down to 2mm on either end length wise.

24. The process as claimed in claim 4, wherein the second layer is built up by flux cored arc welding process where the core wire has a composition of Carbon: 5-7%, Silicon: 0.9-1.1 % Manganese: 0.2-0.3% Chromium: 20-24% Vanadium: 0.7-0.9%, Niobium: 6.0-7.0%, Tungsten: 1-2 %, Molybdenum: 5.5-6.5% and balance Iron.
25. The process as claimed in claim 24, wherein it uses a shielding gas of the Argon / CO2 blend of 80% Argon and 20% CO2 impinged at an angle of 30-45°
26. The process as claimed in claim 24, wherein the thickness of weld layer is between 2-3 mm, i.e. at the center of the working surface of bull ring segment it is 3mm and gradually tapering down to 2mm on either end height wise