TECHNICAL FIELD
[0001] The present invention provides a method for fabrication of grinding rolls with
enhanced grinding ability and higher operational life or more particularly the method of fabrication
of grinding rolls by composite granules causing excellent wear resistance with very high
toughness.
BACKGROUND
[0002] Wear is one of the most commonly encountered industrial problem in coal fired
power stations, where coal is crushed to fine powder by grinding rolls. The major concern of the
grinding rolls (i.e. Ni-hard /High-Chrome rolls) during the course of coal pulverization is, its harsh
abrasive action with silica (Quartz) present in the coal. Silica has the Vickers hardness of > 1100
Hv, due to this, surface of the grinding rolls (which has hardness of around 600-700 Hv) gets worn
out faster and it needs to be replaced frequently.
[0003] The life of grinding rolls can be enhanced by reinforcement of hard and tough
particles at the wear surface. Once the hardness and toughness of particles is higher than the quartz,
wear of surface will reduce and life of grinding roll will be enhanced compared to Ni-hard/High-
Chrome rolls. Ceramic composites have high hardness (i.e. Wear resistance) and toughness (i.e.,
fracture resistance) and can be reinforced at the surface of grinding roll to improve the wear rate.
[0004] The wear rate of ceramics surfaces is dominated by the mechanism of microcutting
and microcracking and follows the Evans-Wilshaw wear relationship, WR ~ Klc 3/4·Hv 1/2 (WR is
the wear rate, Klc is fracture toughness and Hv is the hardness of material). In view of this, intensity
of microcutting and microcracking decreases with increase in hardness and fracture toughness of
the worn surface i.e. the hardness and the fracture toughness emerge as the main material
parameters for abrasion control.
[0005] In view of above, to fabricate the grinding rolls with enhanced life, the reinforced
grains should exhibit, a high abrasion resistance (hardness greater than silica) and some ductility,
to withstand against the impacts. Also the reinforced grains should be properly embedded in metal
matrix, as poor filtration (or bonding) of metal may lead to easy cleavage of reinforced grains
during the grinding process. In addition, reinforced grains should follow the actual wear pattern
over the surface for enhanced operational life.

[0006] As discussed above, reinforced grains should exhibit, high abrasion resistance and
some ductility. Traditional ceramic rarely resistant to both impact and abrasion. In this regard,
document (U.S.Pat. No RE39, 998 E issued Jan.2008) discloses a method where a combination of
Al2O3 and ZrO2 is proposed by a judicious choice to achieve the desired hardness and toughness
of ceramic composite.
[0007] Document (US. Pat. No. 3,181,939 issued May 1965) also discloses a method for
manufacturing of fused Al2O3 and ZrO2 abrasives, which combine good wear resistance
characteristics of Al2O3 and the toughness of ZrO2 and can improve the life of wear resistant
segment.
[0008] The document U.S. Pat. No 2013/0126649 A1 issued in May, 2013 also discloses
a method where working face of the segment is reinforced by granules of Al2O3 and ZrO2. To
reinforce the granules at wear surface, pre-shaped structure of Al2O3 and ZrO2 composite is kept
in a pool and impregnated by the liquid cast metal at 1500°C to get the metal-granule composite.
[0009] Document U.S. Pat. No 8147980B2 (2012) also discloses a method for fabrication
of metal matrix ceramic composite (MMCC) wear part. In MMCC wear part, the wear portion is
made of ceramic cake comprising of Al2O3, ZrO2, and any one of the carbide materials such as
SiC and WC. The ceramic cake is impregnated by the liquid cast metal and finally arranged on
wear surface of grinding roll of bowl mill.
[0010] After getting the desired hardness /toughness, the developed granules should be
properly embedded in metal matrix, to avoid easy cleavage. The problem of poor infiltration of
metal around the reinforced grains, is addressed in document (U.S. Pat. No RE39, 998 E issued
Jan.2008) where granules are pre-shaped in spongy structure to promotes the arrival of the liquid
metal around the granules for complete embedment inside the metal-matrix. In addition, when
thickness of the wear surface is larger than 25 mm, two or more pads are superimposed, separated
by a minimum gap of the order of 10 mm for the infiltration of the liquid metal around the granules.
[0011] Even though aforesaid methods are available to fabricate the wear resistant part
with proper infiltration of metal around the granules are available. Still there is a need of a process,
where much higher hardness and toughness granules can embed over the surface to enhance the
life. In addition, superimposing of two pads can be avoided to get the filtration above 25 mm

thickness and design of wear resistant segment should be such that, working surface should follow
the actual wear pattern to enhanced operational life.
[0012] However as discussed above, a single material is very rarely resistant to both impact
and abrasion. Judicious combination of two different materials can meet the requirement of desired
hardness and toughness upto some extent, as hardness increases toughness decreases and vice-
versa.
[0013] The present invention meets the long felt need by overcoming all the difficulties.
OBJECTS OF THE DISCLOSURE
[0014] Some of the objects of the present disclosure, which at least one embodiment herein
satisfy, are listed hereinbelow.
It is therefore an object of the present invention to provide a method to fabricate
the high wear resistance grinding rolls, where wear surface is reinforced by composite granules in
plough shape structure having excellent wear resistance along with very high toughness.
[0015] Another object of the present invention is to fabricate the wear resistant segment
with very high hard and tough granules.
[0016] Yet another object of the invention is to fabricate the wear resistance segment,
which can avoid the superimposing of two pads to achieve the metal filtration up to 50-60 mm.
[0017] Further object of the invention is to fabricate the wear resistant segment, where
cleavage of reinforced grains during the grinding process can be avoided.
[0018] Another object of the invention is to design a wear resistant segment, where
reinforced grains can follow the actual wear pattern during the grinding process for enhanced
operational life.
[0019] Yet another object of the present invention is to propose a process to fabricate the
high strength wear resistant grinding rolls with enhanced coal grinding ability and higher
operational life.

SUMMARY
[0020] This summary is provided to introduce concepts related to a process to utilize
non-coking coal for producing a metallurgical coke. 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.
[0021] The present method for fabrication of high wear resistance grinding rolls with
enhanced grinding ability and higher operational life comprises the steps of :
i. conversion of composite granules to a defined shape and cast with high chrome;
ii. arranging of cast compounds on the outer periphery of the casting die and poured
with SG iron/grey iron during centrifugal casting of grinding roll;
iii. arrangement of granules over the surface of grinding roll in three dimensional
spongy structure with open pores to promote the arrival of the liquid metal
characterized in that the embedded granules have sufficient gap which promotes
smooth infiltration of metal and helps maintaining the volume percentage of metal from 65% to
70% of total volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are incorporated in and constitute a part of this
disclosure, illustrate exemplary embodiments and, together with the description, serve to explain
the disclosed principles. In the figures, the left-most digit(s) of 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 and/or methods
in accordance with embodiments of the present subject matter are now described, by way of
example only, and with reference to the accompanying figures, in which: Figure 1. Schematic of
grinding roll having high wear resistant segment on wear surface.
[0023] Figure 2. Schematic side view of plough shape structure of composite granules
over the working surface of wear resistant segment.
[0024] Figure 3. Schematic of the composite granules showing hard and tough particles
inside metal-matrix.

[0025] Figure 4. Showing the arrangement to get the equal spacing of wear resistant
segment over the grinding surface.
[0026] Fig. 4 (a) illustrates the wear resistant segment having male extrusion 17.
Fig. 4 (b) shows the female slots 18, on other side of wear resistant segment 6.
Fig. 4 (c) illustrates the male extrusion and female slots leads to equal spacing
between the consecutive segments, as shown in
[0027] Figure 5. Showing the top view of saw tooth structure on the top of wear resistant
segment for better grip of segment. This structure helps the wear resistant segment to withstand
against the mechanical stresses developed during grinding process.
[0028] Figure 6. Shows the developed grinding rolls, where wear surface is reinforced by
composite granules having excellent wear resistance along with very high toughness.
DETAILED DESCRIPTION
[0029] In the present document, the word "exemplary" is used herein to mean "serving
as an example, instance, or illustration." Any embodiment or implementation of the present subject
matter described herein as "exemplary" is not necessarily to be construed as preferred or
advantageous over other embodiments.
[0030] While the disclosure is susceptible to various modifications and alternative
forms, specific embodiment thereof has been shown by way of example in the drawings and will
be described in detail below. It should be understood, however that it is not intended to limit the
disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications,
equivalents, and alternatives falling within the scope of the disclosure.
[0031] The terms “comprises”, “comprising”, “includes” or any other variations
thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that
includes a list of components or steps does not include only those components or steps but may
include other components or steps not expressly listed or inherent to such setup or device or
method. In other words, one or more elements in a system or apparatus proceeded by “comprises…
a” does not, without more constraints, preclude the existence of other elements or additional
elements in the system or method.

[0032] In the following detailed description of the embodiments of the disclosure,
reference is made to the accompanying drawings that form a part hereof, and in which are shown
by way of illustration specific embodiments in which the disclosure may be practiced. These
embodiments are described in sufficient detail to enable those skilled in the art to practice the
disclosure, and it is to be understood that other embodiments may be utilized and that changes may
be made without departing from the scope of the present disclosure. The following description is,
therefore, not to be taken in a limiting sense.
[0033] The present disclosure provides a method for fabrication of high wear resistance
grinding rolls with enhanced grinding ability and higher operation life. The wear surface is
reinforced by composite granules having excellent wear resistance alongwith very high toughness.
[0034] The composite granules are reinforced in plough shape structure.
[0035] The composite granules are embedded over the wear surface in the form of plough
shape structure, which exactly match the actual wear pattern during grinding and maximize the
operational life. In addition, plough shape structure avoids superimposing of two pads to achieve
the improved infiltration around the granules.
[0036] The composite granules exhibit hardness of 1670-1850 Hv and toughness of around
5-10 MPam1/2. The composite granules are made of very high hardness / tough particles and
contains Al2O3, ZrO2, TiB2 and Y2O3 to improve the wear rate.
[0037] The said method comprises the steps of:
i. conversion of composite granules to a defined shape and cast with high chrome;
ii. arranging of cast compounds on the outer periphery of the casting die and poured
with SG iron/grey iron during centrifugal casting of grinding roll;
iii. arrangement of granules over the surface of grinding roll in three dimensional
spongy structure with open pores to promote the arrival of the liquid metal
characterized in that the embedded granules have sufficient gap which promotes
smooth infiltration of metal and helps maintaining the volume percentage of metal from 65% to
70% of total volume.
[0038] The schematic diagramme of developed grinding roll is illustrated in Figure 1.

[0039] The composite granules 2, has much higher hardness than metal 3 and 4. The
composite granules 2, are at least three time harder than the metal 3 and 4. The granules 2, are also
tougher and can withstand against the mechanical stresses during grinding process. The granules
2, over the surface of grinding roll 1, are arranged in three dimensional spongy structure having
open pores 5, all of which communicate with one another.
[0040] The spongy structure promotes the arrival of the liquid metal 3, and solves the
problem of the poor infiltration of the liquid metal around the granules 2. The diameter of open
pore ranges from 10 to 25 mm, preferably from 15 to 20 mm, and more preferably from 12 to 15
mm. The size of granules 2, varies from 1 to 10 mm, preferably from 1 to 8 mm, and more
preferably from 5 to 6 mm.
[0041] The hard granules are embedded over the wear surface in the form of plough shape
structure, which exactly match the actual wear pattern during grinding and maximize the
operational life. The side view of plough shape structure is depicted in Figure. 2. Plough shape
structure have variation in thickness from top to bottom. The point 9 of component 6, which is
around 20-25 mm below from the point 7, have the maximum wear of 50-55 mm during the
grinding process. The wear at point 10, which is 100-105 mm below from the point 9, have
maximum of around 55-60 mm, which is the maximum wear, which occurs at grinding surface.
The point 11, which is above 20-25 mm from point 8, have the lesser wear compared to point 9
and 10. The wear at point 11, range from 40-45 mm.
[0042] The composite granules are comprised of Al2O3, ZrO2 and TiB2.
[0043] The weight percentages of all the ingredients are as follows:
Al2O3- 60-90% of total weight
ZrO2 – 10-40% of total weight
TiB2- 1-10% of total weight
Particles, of composite granules, are very hard particles and made of Al2O3, ZrO2, and TiB2. The
ZrO2 percentage is limited to 10-40% inside Al2O3 matrix of particle, to achieve high hardness.
Further increase in ZrO2 percentage reduced hardness of particle. After judicious choice of Al2O3
and ZrO2, the addition of small amount of TiB2 in the mixture, leads to drastic improvement in the

wear resistance of component, due to inherent high hardness (~ 34 GPa) of TiB2. The amount of
TiB2 is preferably between about 1 to about 10 % of the total loading, more preferably between
about 5 to about 10%. The particle size of TiB2 in the matrix of Al2O3 and ZrO2 of composite
granules or particle, ranges from 5-10 microns.
Though the particles of composite granules having adequate hardness, but it also includes yttria
(Y2O3). ZrO2 doped with Y2O3 by 3 mol % leads to phase transformation and put the crack into
compression, retarding its growth, and enhancing the fracture toughness. The toughness of
particles 14, is around 10 MPam1/2, which improve the wear resistant of composite granules, of
segments 6, of roller 1. The Y2O3 uses upto 10 MPam1/2.
In accordance to another embodiment of the present invention, there provided homogenous wear
pattern at the surface of the roller and it should withstand against the high mechanical stresses
developed during grinding process. To have the homogenous wear pattern over the surface, an
arrangement is made in wear resistant segment 6, which provides equal spacing between the
consecutive segments.
[0044] The arrangement to get the equal spacing among the segments is shown in Figure.
4. The wear resistant segments 6, have male extrusion and female slots on the surface,
perpendicular to working surface. As shown in Figure. 4 (a), the male extrusions 17, have a
thickness of around 8-10 mm and height of around 15 mm. The gap between male extrusions
ranges from 350-380 mm, more preferably 350-355 mm. The female slots 18, on other side of
wear resistant segment 6, [Figure. 4 (b)], have a depth of 5 mm and can accommodate the male
extrusion 17, of previous segment, which leads to equal spacing between the consecutive
segments, as shown in Figure. 4 (c). The other advantage of male / female slots is that the segments
do not move from their fixed positions during casting.
[0045] As discussed above, the wear resistant segment 6, should withstand against the high
mechanical stresses developed during grinding process. To provide better grip of wear resistant
segment 6, inside the SG iron matrix 19, a gripping arrangement 20, is made on top and bottom
portion of wear resistant segment. The gripping arrangement 20, on the top of wear resistant
segment has the saw tooth structure, top view is shown in Figure. 5. The gripping segments have
thickness of around 50-60 mm and length of around 80-85 mm. The height of tooth ranges from

5-8 mm from the baseline 21, and two consecutive teeth 22, 23 have an angle of 60° for better
infiltration and grip. During the centrifugal casting, SG iron infiltrates in the space available
between the saw tooth structures and provides the grip after solidification. The developed grinding
roll is shown in Figure 6.
[0046] The non-limiting advantages of the present invention are as follows:
1. The method of fabrication of grinding rolls, where surface of wear resistant segment 6, of
grinding roll 1, is reinforced by composite granules having excellent wear resistance and
toughness.
2. The composite granules is made up of very hard and tough particles.
3. The composite granules has coating of Co-WC around them, which improves metal
infiltration around granules and avoids superimposing of two pads.
4. To further improve infiltration around the composite granules, these are embedded over
the surface in the form of plough shape structure.
5. The plough shape structure of composite granules, these are exactly matches with the actual
wear pattern over the surface.
6. The plough shape structure 12, of composite granules helps in maintaining the volume
percentage of metal and composite granules and leads to improved infiltration.
7. The plough shape structure of composite granules has the variation in wear pattern from
top to bottom.
8. The plough shape structure of composite granules has maximum wear of around 55-60 mm
during grinding process.
9. The plough shape structure of composite granules has the gap of around 9-10 mm from the
working surface to promote the infiltration of metal.
10. The plough shape structure of composite granules also has sufficient gap from top and
bottom of wear resistant component for arrival of the metal.
11. To have the homogenous wear pattern over the surface of grinding roll, the wear resistant
segments 6, have male extrusion 17, and female slots 18, on the surface, which provide
equal spacing between the consecutive segments.
12. To provide the better grip of wear resistant segment 6, inside the SG iron matrix, top and
bottom portion of wear resistant segment has the saw tooth structure.
13. The saw tooth structure has an angle of 60° between two consecutive teeth for better metal
infiltration and grip.

14. The fabricated grinding rolls, have excellent wear resistance and toughness, which improve
the operational life and grinding ability.
Equivalents:
[0047] The illustrated steps are set out to explain the exemplary embodiments shown,
and it should be anticipated that ongoing technological development will change the manner in
which particular functions are performed. These examples are presented herein for purposes of
illustration, and not limitation. Further, the boundaries of the functional building blocks have been
arbitrarily defined herein for the convenience of the description. Alternative boundaries can be
defined so long as the specified functions and relationships thereof are appropriately performed.
Alternatives (including equivalents, extensions, variations, deviations, etc., of those described
herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained
herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the
words "comprising," "having," "containing," and "including," and other similar forms are intended
to be equivalent in meaning and be open-ended in that an item or items following any one of these
words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only
the listed item or items. It must also be noted that as used herein and in the appended claims, the
singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates
otherwise.
[0048] Finally, the language used in the specification has been principally selected for
readability and instructional purposes, and it may not have been selected to delineate or
circumscribe the inventive subject matter. It is therefore intended that the scope of the invention
be limited not by this detailed description, but rather by any claims that issue on an application
based here on. Accordingly, the embodiments of the present invention are intended to be
illustrative, but not limiting, of the scope of the invention, which is set forth in the following
claims.

We claim:
1. A method for fabrication of high wear resistance grinding rolls with enhanced grinding
ability and higher operational life comprises the steps of :
i. conversion of composite granules to a defined shape and cast with high chrome;
ii. arranging of cast compounds on the outer periphery of the casting die and poured
with SG iron/grey iron during centrifugal casting of grinding roll;
iii. arrangement of granules over the surface of grinding roll in three dimensional
spongy structure with open pores to promote the arrival of the liquid metal
characterized in that the embedded granules have sufficient gap which promotes
smooth infiltration of metal and helps maintaining the volume percentage of metal from 65% to
70% of total volume.
2. The method as claimed in claim 1, wherein the granules are arranged over the surface
of grinding roll in three dimensional spongy structure.
3. The method, the diameter of open pore having a range from 10 to 5 mm, preferably
from 15 to 20 mm and more preferably from 12 to 15 mm.
4. A composite granules for process of fabrication of high wear resistance grinding rolls,
said granules comprises of Al2O3, ZrO2 , TiB2 and optinallyY2O3 , which exhibit hardness of
1670-1850 Hv and toughness of around 5-10 MPam1/2.
5. The composite granules as claimed in claim 4, wherein the weight percentages of the
ingredients are given below:
i. Al2O3- 60-90% of total weight
ii. ZrO2 – 10-40% of total weight
iii. TiB2- 1-10% of total weight
iv. Y2O3- upto toughness10 MPam1/2
or 5-10 MPam1/2.

6. The composite granules as claimed in claim 4, wherein the size is upto 1 to 10 mm,
preferably from 1 to 8 mm and more preferably from 5 to 6 mm.