Claims:1. A mineral grinding article (100) comprising:
a support portion (110); and
a grinding portion (120) disposed on the support portion (110), wherein the grinding portion (120) comprises a cast alloy phase (140) disposed within an interconnected network (132) of a silicon carbide phase (130).
2. The mineral grinding article (100) as claimed in claim 1, wherein the interconnected network (132) of the silicon carbide phase (130) is a three-dimensional network.
3. The mineral grinding article (100) as claimed in claim 2, wherein the cast alloy phase (140) is in the form of an interconnected network structure (146).
4. The mineral grinding article (100) as claimed in claim 3, wherein the interconnected network of the cast alloy phase (140) is a three-dimensional network.
5. The mineral grinding article (100) as claimed in claim 1, wherein the grinding portion (120) comprises the silicon carbide phase (130) in an amount in a range from about 50 vol.% to about 90 vol.% of the grinding portion (120).
6. The mineral grinding article (100) as claimed in claim 1, wherein the cast alloy phase (140) comprises cast iron.
7. The mineral grinding article (100) as claimed in claim 6, wherein the cast iron comprises less than 25 wt.% of chromium.
8. The mineral grinding article (100) as claimed in claim 1, wherein the cast alloy phase (140) comprises a carbide phase in an amount less than 10 wt.% of the cast alloy phase (140).
9. The mineral grinding article (100) as claimed in claim 1, wherein the cast alloy phase (140) comprises silicon nitride particles in an amount in a range from 1 vol.% to 10 vol.% of the cast alloy phase (140).
10. The mineral grinding article (100) as claimed in claim 1, wherein the cast alloy phase (140) comprises a wetting agent in an amount in a range from 0.5 wt.% to 4 wt.% of the cast alloy phase (140), wherein the wetting agent comprises titanium, nickel, cobalt, or combinations thereof.
11. The mineral grinding article (100) as claimed in claim 1, wherein a median diameter of the cast alloy phase (140) is less than 1 millimeter.
12. The mineral grinding article (100) as claimed in claim 1, wherein the grinding portion (120) is in the form of a plurality of segmented wear strips (180).
13. The mineral grinding article (100) as claimed in claim 12, wherein the plurality of segmented wear strips (180) is mechanically attached to the support portion (110).
14. The mineral grinding article (100) as claimed in claim 1, wherein the mineral grinding article (100) is a coal grinding roller.
15. A mineral grinding article (100) comprising:
a support portion (110); and
a grinding portion (120) disposed on the support portion (110), wherein the grinding portion (120) comprises a plurality of segmented wear strips (180) comprising an interconnected network of a cast alloy phase (140) disposed within an interconnected network (132) of a silicon carbide phase (130).
16. The mineral grinding machine as claimed in claim 15, wherein both the silicon carbide phase (130) and the cast alloy phase (140) are in the form of three-dimensional interconnected network structures.
17. The mineral grinding article (100) as claimed in claim 15, wherein the cast alloy phase (140) comprises cast iron comprising a chromium content less than 25 wt.%.
18. The mineral grinding article (100) as claimed in claim 17, wherein the plurality of segmented wear strips (180) comprises the silicon carbide phase (130) in an amount from about 50 vol.% to about 90 vol.% of the plurality of segmented wear strips (180).
19. A coal grinding roller (100) comprising:
a support portion (110); and
a grinding portion (120) disposed on the support portion (110), wherein the grinding portion (120) comprises a plurality of segmented wear strips (180) comprising a three-dimensional interconnected network of a cast alloy phase (140) disposed within a three-dimensional interconnected network (132) of a silicon carbide phase (130).
20. The coal grinding roller as claimed in claim 19, wherein the plurality of segmented wear strips (180) comprises the silicon carbide phase (130) in an amount from about 50 vol.% to about 90 vol.% of the plurality of segmented wear strips (180).
, Description:
FIELD OF THE INVENTION
[0001] Embodiments of the present invention generally relate to mineral grinding articles having silicon carbide. More particularly, the embodiments are directed to mineral grinding articles having interconnected network of silicon carbide in a grinding portion.
BACKGROUND
[0002] Coal crusher apparatuses are used to crush coal which is fed to a boiler for producing steam, reducing the size of the coal units from about 20 millimeters to less than 75 microns size. In the coal crusher apparatuses, coal is fed to a small clearance between a bull ring and one or more coal crusher rollers, for crushing. On prolonged usage, the grinding surfaces of the coal crusher rollers get worn out due to the inherent abrasive nature of the coal that is being crushed. In general, coals that have elevated ash content are more abrasive than coals with lower ash content, and may cause faster erosion of the grinding surfaces of the coal crusher rollers. Coal crusher rollers may get eroded both by attrition and wear from the crushing loads applied on them. Therefore, roller materials generally undergo severe material loss due to interaction of coal particles between rollers and ring rubbing surface. Further, degradation of the coal crusher rollers may be caused by contaminants in the coal supply, such as iron and stone, which may cause sudden impacts when introduced into the coal crusher apparatuses. The degradation of coal crusher rollers is generally caused by lack of surface hardness and toughness of the coal crusher rollers.
[0003] Conventional coal crusher rollers are fabricated by zirconia toughened alumina (ZTA) in a high-chrome matrix, which is generally prepared by sinter cast process. In the coal crusher rollers, ZTA particles are highly coarse in nature and are randomly dispersed. Failure of rollers generally occur when coal rubs against these ZTA particles and removes ZTA particles from the matrix. Further, the rollers may exhibit a large area of ZTA-free matrix region. The matrix region has lower abrasion resistance compared to the abrasive resistance of ZTA particles and is more prone to wear compared to ZTA particles. Therefore, it is desirable to have a more robust design and materials for the coal crusher rollers.
BRIEF DESCRIPTION
[0004] In one aspect, a mineral grinding article is disclosed. The mineral grinding article includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a cast alloy phase disposed within an interconnected network of a silicon carbide phase.
[0005] In another aspect, a mineral grinding article is disclosed. The mineral grinding article includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a plurality of segmented wear strips having an interconnected network of a cast alloy phase disposed within an interconnected network of a silicon carbide phase.
[0006] In yet another aspect, a coal grinding roller is disclosed. The coal grinding roller includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a plurality of segmented wear strips. The plurality of segmented wear strips includes a three-dimensional interconnected network of a cast alloy phase disposed within a three-dimensional interconnected network of a silicon carbide phase.
DRAWINGS
[0007] These and other features and aspects of embodiments of the disclosed article will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings.
[0008] FIG. 1 is a schematic view of a mineral grinding article, showing a two-dimensional interconnected structure of an interconnected network structure of a silicon carbide phase, in accordance with some embodiments of the disclosure.
[0009] FIG. 2 is a schematic view of a mineral grinding article, showing a three-dimensional interconnected structure of an interconnected network structure of a silicon carbide phase, in accordance with some embodiments of the disclosure.
[0010] FIG. 3 is a photograph of a three-dimensional interconnected structure a silicon carbide phase, in accordance with some embodiments of the disclosure.
[0011] FIG. 4 is a perspective view of an apparatus having a mineral grinding article, in accordance with some embodiments of the disclosure.
[0012] FIG. 5 is a perspective view of a mineral grinding article having a plurality of segmented wear strips, in accordance with some embodiments of the disclosure.
[0013] FIG. 6 is a cross-sectional view along lines 6-6 of the mineral grinding article of FIG. 5, in accordance with some embodiments of the disclosure.
DETAILED DESCRIPTION
[0014] In the following specification and the claims, which follow, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. As used herein, the term “or” is not meant to be exclusive and refers to at least one of the referenced components being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise.
[0015] Provided are exemplary mineral grinding articles, and methods for forming the mineral grinding articles. The mineral grinding article described herein provides a hard and robust grinding portion having a cast alloy phase disposed within an interconnected network of silicon carbide phase. This composite of silicon carbide with cast alloy phase has a higher abrasion resistance than currently known grinding articles. Silicon carbide has a superior hardness and fracture toughness properties compared to ZTA particles. However, silicon carbide particles are known to have very limited wettability with any metal or alloy matrix. In this disclosure, a composite of silicon carbide phase and a cast alloy phase is presented that has circumvented the difficulty of limited wetting of SiC with cast alloy and can be effectively used for enabling a reliable and long service lifetime of a mineral grinding article.
[0016] In one aspect, a mineral grinding article is disclosed. The mineral grinding article includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a cast alloy phase disposed within an interconnected network of a silicon carbide phase. FIG. 1 illustrates some embodiments of a mineral grinding article 100. The mineral grinding article 100 includes a support portion 110 and a grinding portion 120. The grinding portion 120 is disposed on the support portion 110. The support portion 110 has an average support portion 110 hardness that may be same as, or less than an average hardness of the grinding portion 120. In some embodiments, a hardness of the support portion 110 is less than the hardness of the grinding portion 120.
[0017] The support portion 110 may include any suitable material, including, but not limited to, a chrome-iron alloy, cast iron, spheroidal graphite iron, white cast iron, cast iron including niobium, cast iron including chromium, cast iron including titanium, Hadfield steel, cast steel, locomotive wheel steel, or combinations thereof. In some embodiments, the support portion 110 may further include a second phase in the form of a plurality of particles. Suitable plurality of particles may include, but are not limited to, particles formed from a material including metal carbides, metal borides, metal oxides, boron nitrides, boron carbides, boron carbon nitrides, zirconia toughened aluminas, silicon carbides, silicon nitrides, silicon oxy-nitrides, silicon aluminum oxy-nitrides, sintered derivatives thereof, or combinations thereof. In some embodiments, the plurality of particles in the support portion 110 includes dispersed particles.
[0018] The support portion 110 may include any suitable structural composition. The support portion 110 may be a solid structure, or may have hollow portions. In some embodiments, the support portion 110 may include various layers having same or different hardness values. The support portion 110 may include any suitable material structure, including, but not limited to, a weld hard-faced structure, a weld overlaid structure, a cold sprayed structure, a laser cladded structure, a coated structure, a cast structure, a composite structure, or combinations thereof.
[0019] The grinding portion 120 may be disposed directly on the support portion 110 or may be disposed on an intermediate layer (not shown in FIG. 1). The grinding portion 120 includes a grinding surface 122. The grinding portion 120 includes a silicon carbide phase 130 in an interconnected network 132. The interconnected network 132 of the silicon carbide phase 130 may be a two-dimensional network or a three-dimensional network. FIG. 1 illustrates a two-dimensional interconnected network 132 of the silicon carbide phase 130 on the surface 122 of the grinding portion 120, and FIG. 2 illustrates a three-dimensional interconnected network 132 of the silicon carbide phase 130 in the grinding portion 120. A cast alloy phase 140 is disposed within the interconnected network 132 of the silicon carbide phase 130. In some embodiments, the cast alloy phase 140 may be in the form of an isolated phase 144 on the grinding surface 122, as illustrated in FIG. 1. In these embodiments, the cast alloy phase 140 may be connected in a three-dimensional structure form in the grinding portion 120, in the portions below the surface 122. In some embodiments, the grinding portion 120 may include a plurality of layers 124, similar to the surface 122, as a part of the grinding portion 120.
[0020] A cast alloy phase is a cast alloy material present in any form, including, but not limited to a continuous structure. A cast alloy is an alloy formed by a casting process. Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a cast. In some embodiments, a cast alloy may be designed for desired hardness, fracture toughness, creep and environmental durability. Cast alloys that may be used in the embodiments of the present disclosure include iron-based cast alloys, nickel-based cast alloys, or combinations thereof. In some embodiments, the cast alloy is a cast iron.
[0021] A cast iron is a group of iron-carbon alloys with a carbon content greater than 2 wt.%. The cast iron may further include various elements. The elements that may be present in the cast iron include, but not limited to, chromium, niobium, silicon, titanium, nickel, or combinations thereof. In some embodiments, the cast alloy includes, but not limited to, cast iron, spheroidal graphite iron, white cast iron, cast iron including niobium, cast iron including chromium, cast iron including titanium, Hadfield steel, cast steel, locomotive wheel steel, or combinations thereof. In some embodiments, a carbide phase that may be present in the cast alloy may be randomly scattered in the cast alloy.
[0022] In some embodiments, the cast alloy phase includes cast iron. In some embodiments, the cast iron includes less than 25 wt.% of chromium. In some embodiments, the cast iron includes chromium in a range from about 10 wt.% to about 23 wt.% of the cast iron. In some embodiments, the cast alloy phase 140 includes a carbide phase in an amount less than 10 wt.% of the cast alloy phase 140. In some embodiments, the cast alloy phase 140 includes a carbide phase in an amount in a range from about 2 wt.% to about 6 wt.% of the cast alloy phase 140. In some embodiments, the cast alloy phase 140 may further include a wetting agent for facilitating wetting of the silicon carbide phase 130. An effective wetting agent of the cast alloy phase 140 for the wetting of the silicon carbide phase 130 includes titanium, nickel, cobalt, or combinations thereof. In some embodiments, the cast alloy phase 140 includes a wetting agent in an amount in a range from about 0.5 wt.% to about 4 wt.% of the cast alloy phase 140. In some embodiments, the cast alloy phase 140 of the mineral grinding article 100 includes the wetting agent present in an amount in a range from about 1 wt.% to about 3 wt.%.
[0023] A silicon carbide phase is a silicon carbide material present in any form, including, but not limited to a particulate form, a fiber form, a continuous structure, or combinations thereof. An “interconnected network of a silicon carbide phase” as used herein refers to the silicon carbide phase that is in an interconnected form. For example, a “cast alloy phase disposed within an interconnected network of a silicon carbide phase” refers to the cast alloy phase located within the gaps of the interconnected network of the silicon carbide phase. The silicon carbide phase may be in the interconnected form by the joining of particulates of the silicon carbide, by joining fibers of the silicon carbide, or combinations thereof. In some embodiments, the interconnected silicon carbide phase includes fine particulates of the silicon carbide phase that are joined by sintering. In some embodiments, the interconnected silicon carbide phase is formed by starting from polymer precursors and fabricating the silicon carbide phase in a continuous form. In some embodiments, the interconnected network 132 of the silicon carbide phase has high fracture toughness and hardness such that the silicon carbide phase is able to withstand wear for more than 12000 hours when used in the grinding portion 120 of the mineral grinding article 100. In some embodiments, a major portion of the silicon carbide phase of the grinding portion 120 is in an interconnected form such that an isolated phase of the silicon carbide phase in the grinding portion 120 is less than 10 vol.% of the grinding portion. In some embodiments, the silicon carbide phase of the grinding portion 120 is essentially formed of the in an interconnected form such that an isolated phase of the silicon carbide phase present in the grinding portion 120 is less than 5 vol.% of the grinding portion 120.
[0024] In some embodiments, the grinding portion 120 includes a three-dimensional interconnected network 132 of the silicon carbide phase 130, as shown in FIG. 2. The silicon carbide phase 130 may be in a in three-dimensional cellular network form. In some embodiments, the interconnected silicon carbide phase has a honeycomb structure, as shown in FIG. 3. FIG. 3 illustrates a photograph of the interconnected network 132 of the silicon carbide phase 130, without showing the presence of the cast alloy phase, for clarity. In some embodiments, the cast alloy phase 140 of the grinding portion 120 is in the form of an interconnected network structure 146. In some embodiments, the interconnected network 146 of the cast alloy phase 140 is a three-dimensional interconnected network.
[0025] In some embodiments, both the silicon carbide phase 130 and the cast alloy phase 140 are in a three-dimensional, interpenetrated, interconnected network structure. As used herein, an “interpenetrated interconnected network” of silicon carbide phase 130 and the cast alloy phase 140 refers to a structure where both the silicon carbide phase 130 and the cast alloy phase 140 are in connected forms and are present within the network of each other. Thus, in some embodiments, at least 95 vol.% of the silicon carbide phase 130 in the grinding portion 120 is in a connected form with less than 5 vol.% of the silicon carbide phase 130 present in a discrete form, without connected to other portions of the silicon carbide phase 130. Further, in some embodiments, at least 95 vol.% of the cast alloy phase 140 in the grinding portion 120 is in a connected form with less than 5 vol.% of the cast alloy phase 140 present in discrete form, without connected to other portions of the cast alloy phase 140.
[0026] The silicon carbide phase 130 has high hardness and fracture toughness properties that facilitates long life time of the mineral grinding article 100. The hardness of the cast alloy phase 140 may be lesser than the hardness of the silicon carbide phase 130. In some embodiments, a hardness of the cast alloy phase may be increased to a certain extent by varying the constituents of the cast alloy phase. An effective material that can be included in the cast alloy phase 140 for increasing toughness, without sacrificing the wetting of the silicon carbide phase 130 with the cast alloy phase 140, is silicon nitride. In some embodiments, the cast alloy phase 140 includes silicon nitride particles in an amount in a range from 1 vol.% to 10 vol.% of the cast alloy phase 140. In some embodiments, the cast alloy phase 140 includes silicon nitride particles in an amount in a range from 5 vol.% to 7 vol.% of the cast alloy phase 140. A hard and tough cast alloy phase 140, existing either as islands or as a three-dimensional network, blunts any cracks that may be generated in the silicon carbide phase 130 during grinding. Thus, the grinding portion has a unique combination of presence of a hard and rigid skeleton of silicon carbide phase that is capable of grinding coal and the presence of the metallic skeleton or islands that ensures crack blunting. The large network of silicon carbide phase 130 gives the required rigidity to the grinding portion 120 and ensures that the composite of silicon carbide and the cast alloy phase is able to handle loading spikes that may result from any occasional entrainment of stones, granite pieces, or metallic objects along with the coal. Thus, the grinding portion 120 is able to grind the coal effectively while suffering minimal abrasion.
[0027] In some embodiments, it is desirable to maximize an amount of silicon carbide phase 130 in the grinding portion 120 in comparison with the cast alloy phase 140. In some embodiments, the grinding portion 120 includes the silicon carbide phase 130 in an amount from about 50 vol.% to about 90 vol.% of the grinding portion 120. In some embodiments, the grinding portion 120 includes the silicon carbide phase 130 in an amount from about 60 vol.% to about 80 vol.% of the grinding portion 120. In some embodiments, an amount of the silicon carbide phase 130 present in the grinding portion 120 may only be limited by a process of obtaining cast alloy phase 140 disposed within the interconnected network 132 of the silicon carbide phase 130.
[0028] As noted earlier, proper wetting of silicon carbide phase 130 with the cast alloy phase 140 is a challenge for the use of silicon carbide in a mineral grinding article. If the wetting of the silicon carbide phase 130 and the cast alloy phase 140 is not in a desirable range, there may be a risk of delinking the silicon carbide phase 130 and the cast alloy phase 140 in the grinding portion 120 leading to wear of grinding portion 120. Many methods of forming a composite of cast alloy phase and silicon carbide phase do not facilitate wetting of the silicon carbide phase and the cast alloy phase. Sand casting is one method that is employed to fabricate the structure of cast alloy phase 140 disposed within the interconnected silicon carbide phase 130 resulting in a structure that has excellent wetting between the two phases. Sand casting is a metal casting process characterized by using sand as the mold material. In a sand casting method of forming the grinding portion 120 of the mineral grinding article 100, a preform of the interconnected network of the silicon carbide phase 130 is first formed and then the cast alloy phase 140 is disposed using the sand casting process. The preform of the silicon carbide phase may be formed by various methods. One example method that is used for forming the interconnected silicon carbide phase is by gel-casting a polymer precursor of the silicon carbide and then sinter the gel-casted structure to form the interconnected network having strength enough to withstand the sand casting process.
[0029] During sand casting, material of the cast alloy phase is melted at high temperature and poured into the interconnected network of the silicon carbide preform placed in a sand mold such that the molten alloy penetrates the gaps within the interconnected network of the silicon carbide preform and solidifies on cooling. The molten alloy interaction with the surfaces of the silicon carbide preform especially increases the wetting behavior or the silicon carbide and cast alloy with each other. A highly interconnected silicon carbide network with small gaps (pores) in between the network results in a higher percentage of silicon carbide phase 130 in the grinding portion 120 of the grinding article 100. In some embodiments, a pore size of the silicon carbide preform may be less than 1 mm, resulting in a median diameter of the cast alloy phase 140 disposed within the interconnected network of the silicon carbide phase having a diameter of less than 1 millimeter. A diameter of the cast alloy phase 140 may be a maximum distance of the cast alloy phase disposed within the interconnected network of the silicon carbide phase in the grinding surface 122, or in a surface parallel to the grinding surface 122, of the mineral grinding article. In some embodiments, a pore size of the silicon carbide preform may be less than 0.5 mm. For the use in a mineral grinding article, a high-density grinding material is desirable to minimize wear of the grinding surface 122. In some embodiments, a porosity present in the grinding portion 120 is less than 10 vol.% of the grinding portion 120. In some embodiments, the porosity in the grinding portion 120 is less than 5 vol.% of the grinding portion 120.
[0030] A mineral grinding article may be an independent component or part of a mineral grinding apparatus. FIG. 4 illustrates a mineral grinding apparatus 200 that includes the mineral grinding article 100. The mineral grinding article 100 may be a ball and race mill, a drum and ball mill, a coal crusher, or combinations thereof. In some embodiments, the mineral grinding apparatus 200 is a coal grinding apparatus, and the mineral grinding article 100 is a coal grinding roller having a grinding surface 122.
[0031] In some embodiments, the grinding portion 120 includes a plurality of segmented wear strips, as illustrated for example, in FIG. 5. The plurality of segmented wear strips includes the interconnected network of the silicon carbide phase and the cast alloy phase disposed within the interconnected network of the silicon carbide phase. In some embodiments, the grinding portion 120 further includes a substrate (not shown in FIG. 5) for the plurality of segmented wear strips and the substrate is attached to the support portion 110. In some embodiments, the grinding portion is in the form of the plurality of segmented wear strips and is disposed directly on the support portion 110, as shown in FIG. 5. The plurality of segmented wear strips 180 may be secured to the support portion 110 by any suitable joining configuration, including, but not limited to, mechanical attachment, welding, brazing, or combinations thereof. In some embodiments, the plurality of segmented wear strips is removably attached to the support portion 110.
[0032] In some embodiments, the plurality of segmented wear strips 180 is mechanically attached to the support portion 110. Mechanical attachment may include, but is not limited to, fastening with a fastener 190 such as bolts or rivets, fitted joints, or combinations thereof. In some embodiments, the plurality of segmented wear strips is joined to the support portion 110 through bolts. In some embodiments, the fastener 190 such that the fastener 190 does not penetrate the entire thickness of the plurality of segmented wear strips 180. In some embodiments, the fastener 190 penetrates the entire thickness of the plurality of segmented wear strips 180. In some embodiments, the fastener 190 attaches the plurality of segmented wear strips 180 to the support portion 110 from an interior face 104 of the mineral grinding article 100, wherein the fastener 190 penetrates the entire thickness of the plurality of segmented wear strips 180, and a thickness of the support portion 110, as shown in FIG. 6. Fitted joints may include, but are not limited to, bridle joints, finger joints, dovetail joints, dado joints, groove joints, tongue and groove joints, mortise and tenon joints, splice joints, half lap spice joints, bevel lap splice joints, tabled splice joints, tapered finder splice joints, or combinations thereof.
[0033] In some embodiments, the plurality of segmented wear strips 180 is welded to the support portion 110. Welding may include any suitable welding technique, including, but not limited to, spot welding, resistance spot welding, resistance seam welding, projection welding, flash welding, upset welding, arc welding, shielded metal arc welding, gas tungsten arc welding, gas metal arc welding, submerged arc welding, plasma arc welding, flux cored arc welding, bare metal arc welding, electroslag welding, laser welding, electron beam welding, ultrasonic welding, friction welding, stir friction welding, gas welding, oxyacetylene welding, oxygen/propane welding, oxyhydrogen welding, pressure gas welding, resistance welding, hot isostatic pressure welding, induction welding, laser-hybrid welding, hybrid welding, tribrid welding, electrogas welding, or combinations thereof. In some embodiments, the plurality of segmented wear strips 180 is brazed to the support portion 110. Brazing may include any suitable brazing technique, including, but not limited to, brazing with braze filler, braze foil, braze tape, brazing with pre-sintered preforms, or combinations thereof.
[0034] The plurality of segmented wear strips 180 may span the grinding surface 122. Individual segmented wear strips 182 of the plurality of segmented wear strips 180 may be disposed adjacent to one another in the grinding portion 120 on the support portion 110. In some embodiments, the individual wear strips 182 of the plurality of strips are contacting one another as shown in FIG. 5. In some embodiments, the individual segmented wear strips 182 of the plurality of segmented wear strips are further joined to each other. The individual segmented wear strips 182 may be joined to each other by a deposition of a cast alloy phase in between the individual segmented wear strips 182 or through methods such as brazing or welding. In some embodiments, the grinding portion 120 may include spacing (not shown in FIG. 5) interspersed between the individual wear strips 182 of the plurality of segmented wear strips 180.
[0035] In some embodiments, the plurality of segmented wear strips 180 are permanently attached to the support portion 110. In some embodiments, the plurality of segmented wear strips 180 may be removably attached to the support portion 110. As used herein, “removably attached” indicates that the plurality of segmented wear strips 180 are removable without damaging the support portion 110.
[0036] Strip length, strip width, and strip thickness of the plurality of segmented wear strips 180 may vary depending on the size and shape of the mineral grinding article 100 and the grinding portion 120. In some embodiments, the plurality of segmented wear strips 180 have a length 184. In some embodiments, a strip length 184 of the plurality of segmented wear strip is at least about 80% of a width 126 of the grinding surface 122 of the grinding portion 120 of the mineral grinding article 100. In some embodiments, wherein the mineral grinding article 100 includes a round conformation of the grinding surface 122, the plurality of segmented wear strips 180 may have a strip width 186 of less than 25% of a lowest diameter 118 of the support portion 110 of the mineral grinding article 100. In some embodiments, the plurality of segmented wear strips 180 have a strip width 186 in a range from about 1% to about 10% of the lowest diameter 118 of the support portion 110.
[0037] FIG. 6 shows a cross section of the mineral grinding article 100 shown in FIG. 5, in a 6-6- direction. In FIG. 6, the plurality of segmented wear strips 180 is forming the grinding portion 120 on the support portion 110. The plurality of segmented wear strips180 may have a strip thickness188 of up to about 100 mm. In some embodiments, the strip thickness 188 of the plurality of segmented wear strips 180 is in a range from about 0.25 mm to about 100 mm. In some embodiments, the strip thickness 188 of the plurality of segmented wear strips 180 is in a range from about 10 mm to about 50 mm. The strip length, strip width, and strip thickness of the individual segmented wear strips 182 of the plurality of segmented wear strips 180 may be same for all the individual wear strips 182, or may vary. In one embodiment, all the individual segmented wear strips 182 have substantially same strip length, strip width, and strip thicknesses, with a variation in length, width, and thickness of individual segmented wear strips 182 is less than 5 % of the average length, width, and thickness of the plurality of segmented wear strips 180, respectively.
[0038] In some embodiments, a mineral grinding article is disclosed. The mineral grinding article includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a plurality of segmented wear strips having an interconnected network of a cast alloy phase disposed within an interconnected network of a silicon carbide phase. The mineral grinding machine of claim 17, wherein the plurality of segmented wear strips includes three-dimensional interconnected networks of both the silicon carbide phase and the cast alloy phase. In some embodiments, the cast alloy phase in the mineral grinding article includes cast iron. In some embodiments, the cast alloy in the mineral grinding article is a cast iron having less than 25 wt.% chromium. In some embodiments, the chromium content in the cast iron is in a range from about 10 wt.% to about 23 wt.% of the cast iron. In some embodiments, the plurality of segmented wear strips in the grinding portion includes the silicon carbide phase in an amount from about 50 vol.% to about 90 vol.% of the plurality of segmented wear strips.
[0039] In a specific embodiment, a coal grinding roller is disclosed. The coal grinding roller includes a support portion and a grinding portion disposed on the support portion. The grinding portion includes a plurality of segmented wear strips. In some embodiments, the grinding portion is fabricated in the form of the plurality of segmented wear strips. In some embodiments, the plurality of segmented wear strips is directly disposed on the support portion. In some embodiments, an intermediate layer may be present in between the support portion and the grinding portion. The plurality of segmented wear strips includes a three-dimensional interconnected network of a cast alloy phase disposed within a three-dimensional interconnected network of a silicon carbide phase. In some embodiments, the cast alloy phase includes cast iron having a chromium content less than 25 wt.%. In some embodiments, the plurality of segmented wear strips in the grinding portion of the coal grinder roller has the silicon carbide phase in an amount from about 50 vol.% to about 90 vol.% of the plurality of segmented wear strips and the cast alloy phase in an amount from about 10 vol.% to about 50 vol.% of the plurality of segmented wear strips.
EXAMPLE
[0040] The following example is presented to further illustrate non-limiting embodiments of the present disclosure.
[0041] A SiC preform of about 100 cm3 volume and having about 10 ppi (pores per inch) porous structure was obtained. The SiC preform was coated with a wetting agent of nickel, cobalt, or titanium, and placed inside a sand casting mold. A cast iron alloy having from about 11 wt.% to about 24 wt.% of chromium, from about 2 wt.% to about 4 wt.% of cobalt, about 1.5 wt.% Si, and balance iron was melted at about 1400 °C and poured into the SiC preform. The SiC preform along with the cast alloy was allowed to cool inside the mold and the cooled specimen was detached from the mold. The specimen obtained was observed through microscope and analyzed. There were no visible cracks present in the specimen when observed under microscope with about 100X magnification. The total amount of SiC in the specimen was estimated to be about 15 volume % of the specimen. Wear rate of the prepared specimen was compared with the wear rate of a pure cast iron having the same composition as the cast iron used for infiltrating the SiC preform. A 20% reduction in the wear rate for the prepared specimen was observed as compared to the wear rate of the pure cast iron. Reducing the pore size in the silicon preform and increasing volume percentage of SiC in the specimen is likely to further improve wear rate of the SiC-cast iron composite having interconnected structure.
[0042] While only certain features of embodiments have been illustrated, and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended embodiments are intended to cover all such modifications and changes as falling within the spirit of the disclosed technique.