Metal Matrix Composite Grinding Ball

Abstract

The present invention is a composite material grinding ball having a core-shell structure, wherein the shell of the core-shell structure contains a ceramic reinforcing material, and the ceramic reinforcing material is a three-dimensional interconnected network of periodically alternating ceramic-metal composite material particles and gaps, the ceramic-metal composite material particles and the gaps having an average diameter within the millimeter range, and the network includes; the ceramic-metal composite material particles contain at least 40% by volume, preferably at least 60% by volume, most preferably at least 70% by volume of ceramic particles fixed in a binder metal matrix, the ceramic particles having an average diameter within the micrometer range; the three-dimensional interconnected network of ceramic-metal composite material particles and gaps is embedded in a ferrous alloy cast metal matrix, the ferrous alloy cast metal matrix filling the gaps between the interconnected ceramic-metal composite material particles of the three-dimensional interconnected network; the ceramic-metal composite material particles embedded in the ferrous alloy cast metal matrix have a volume fraction of porosity of less than 5% by volume, preferably less than 3% by volume, most preferably less than 1% by volume, the porosity measurement being based on Annex A of ISO 13383-2:2012; the shell contains a volume content of at least 35% by volume, preferably at least 45% by volume of ceramic-metal composite material particles; the ceramic reinforcing material of the shell covers at least 85%, preferably 90%, most preferably 95% of the entire surface of the grinding ball, and discloses a composite material grinding ball.

Description

Technical Field

[0001] The present invention relates to composite material grinding balls obtained by conventional casting techniques and having improved resistance to combined wear and impact stress, particularly core-shell composite material grinding balls. The grinding balls of the present disclosure include an assembled shell, particularly a reinforcing shell of a precast ceramic body consisting of two half shells, and have at least one inlet hole for casting metal. The shell includes a three-dimensional interconnected network of aggregated ceramic-metal composite material particles and gaps, both in the millimeter diameter range, with the ceramic micrometer particles fixed in a binder metal matrix and the millimeter gaps infiltrated and filled by a casting metal matrix.

Background Art

[0002] The present invention relates to wear-resistant composite material grinding balls typically used in tumbling mills in the grinding industry for clinker grinding in cement plants or ore grinding in mines. The grinding balls are subject to high impact stress and often high wear due to abrasion or corrosion. Therefore, it is desirable for the grinding balls to exhibit high wear resistance, corrosion-resistant wear, and a certain degree of ductility so that they can withstand mechanical stresses such as ball-to-ball impact or ball-to-liner impact.

[0003] Considering that it is difficult for these two properties to coincide with the same material composition, metal-ceramic composite material grinding balls have been proposed.

[0004] Chinese Patent Application Publication No. 106914620 (2017) discloses a method for preparing a ceramic / metal composite material grinding ball having a precast body honeycomb structure arranged in a cavity before casting, using selective laser cladding combined with three-dimensional digital modeling technology.

[0005] Chinese Patent Application Publication No. 103357854 (2013) and Chinese Patent Application Publication No. 113564511 (2021) disclose a ceramic-reinforced grinding ball in which a reinforcing layer includes the embedding of nanometer-grade ceramic particles on and below the surface of the grinding ball. The mold has an inner wall coated with nanometer ceramic particles.

[0006] Chinese Patent Application Publication No. 104707972 (2015) discloses a composite material grinding ball having a core-shell structure with ceramic reinforcements embedded in an iron alloy cast metal matrix. This document also does not disclose specific volume % of ceramics fixed in a binder metal matrix, specific ceramic-metal composite material particles, nor a three-dimensional interconnected network of periodically alternating ceramic-metal composite material particles and gaps in the millimeter range.

[0007] Chinese Patent Application Publication No. 109128098 (2019) discloses a method for manufacturing a ceramic-metal composite material using an Al2O3-ZrO2 powder that is converted into a plurality of ceramic core pieces in a mold, where the grinding ball is later cast with manganese steel. This document also does not disclose ceramic particles fixed in a binder metal matrix nor an interconnected network of periodically alternating ceramic-metal composite material particles of these fixed particles.

[0008] European Patent No. 3885061 (Magotteaux 2021) discloses a layered composite material wear part including a reinforcing material of periodically alternating millimeter ceramic-metal composite material particles and a three-dimensional interconnected network of millimeter gaps, where the millimeter ceramic-metal composite material particles have a low porosity.

[0009] The grinding ball market is price-sensitive and therefore optimal wear performance and price must be respected, and manufacturing must be adapted accordingly. The realization of ceramic precast shell bodies / hollow balls of agglomerated ceramic metal particles in an economical way, their robustness during casting operations, and the ability to be infiltrated by the casting metal without damage are very important.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non-Patent Documents

[0011]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention aims to provide a ceramic-reinforced core-shell grinding ball manufactured by integrating a conventional casting containing a metal matrix of cast iron or steel, and a high-concentration of micrometer ceramic particles with a low-porosity ceramic-metal particle-reinforced shell structure fixed in a metal binder matrix.

Means for Solving the Problems

[0013] The present invention is a composite material grinding ball having a core-shell structure, wherein the shell of the core-shell structure contains a ceramic reinforcing material, and the ceramic reinforcing material is a three-dimensional interconnected network of periodically alternating ceramic-metal composite particles and gaps, and the ceramic-metal composite particles and gaps have an average diameter within the millimeter range. including; The ceramic-metal composite particles contain at least 40% by volume, preferably at least 60% by volume, and most preferably at least 70% by volume of ceramic particles fixed in a binder metal matrix, and the ceramic particles have an average diameter within the micrometer range; The three-dimensional interconnected network of ceramic-metal composite particles and gaps is embedded in an iron alloy casting metal matrix, and the iron alloy casting metal matrix fills the gaps between the interconnected ceramic-metal composite particles of the three-dimensional interconnected network; The ceramic-metal composite particles embedded in the iron alloy casting metal matrix have a volume fraction of porosity of less than 5% by volume, preferably less than 3% by volume, and most preferably less than 1% by volume, and the porosity measurement is based on Annex A of ISO 13383-2:2012; The shell contains a volume content of at least 35% by volume, preferably at least 45% by volume of ceramic-metal composite particles; The ceramic reinforcing material of the shell covers at least 85%, preferably 90%, and most preferably 95% of the entire surface of the grinding ball. A composite material grinding ball is disclosed.

[0014] The present invention further discloses at least one or a suitable combination of the following structural features: - The ceramic particles are selected from the group consisting of carbides, nitrides, carbonitrides, and borides, or mixtures thereof; - The ceramic particles are selected from the group consisting of titanium carbide, titanium carbonitride, tungsten carbide, niobium carbide, vanadium carbide, zirconium carbide, tantalum carbide, hafnium carbide, and molybdenum carbide; - The thickness of the ceramic reinforcing shell ranges from 2 to 15 mm, preferably from 2 to 10 mm, and most preferably from 3 to 8 mm; - The embedded ceramic-metal composite material particles have a particle size distribution of 0.3 to 10 mm and an average particle size D of 1 to 4 mm, preferably 1 to 3 mm 50 and the average particle size D 50 can be measured by performing a micrograph view such that at least 250 ceramic-metal composite material particles are present over the field of view of one or more polished cross-sections of one or more samples using a computer program and an optical microscope, and appropriate thresholds enable segmentation of the particles into a grayscale image and the background; - The fixed ceramic particles in the binder metal matrix have a particle size of 0.1 to 50 μm, preferably 0.1 to 30 μm, and an average particle size D of 0.5 to 20 μm, preferably 1 to 10 μm 50 ; - The binder metal matrix is selected from the group consisting of ferromanganese-based alloys, ferrochrome-based alloys, and nickel-based alloys; - The ferroalloy cast metal matrix includes high-chromium white iron containing at least 11% by mass of chromium, or steel.

[0015] The present invention further provides a method for manufacturing the composite material grinding ball of the present invention, a) Preparing or manufacturing ceramic-metal composite material particles containing at least 40% by volume of micrometer ceramic particles fixed in a binder metal matrix, wherein the ceramic-metal composite material particles have a porosity of less than 5% by volume, preferably less than 3% by volume, particularly less than 1% by volume; b) Manufacturing a ceramic precast body shell in the form of a preferably half-shell of a three-dimensional interconnected network of millimeter ceramic-metal composite material particles obtained in step a) and millimeter gaps that are periodically alternating; c) Assembling the shell obtained in step b) into a hollow sphere containing one or two inlet openings and placing the hollow sphere in the cavity of a mold of a grinding ball to be cast; d) Injecting the grinding ball and simultaneously infiltrating the millimeter gaps of the three-dimensional interconnected network of the shell, arranged according to step c), with a ferroalloy casting metal matrix; e) Releasing the composite material grinding ball Discloses a method for manufacturing a composite material grinding ball including the above steps.

[0016] The present invention further includes the following: - The method for manufacturing the ceramic-metal composite material particles in step a) includes - Grinding a powder composition containing ceramic particles and a binder metal matrix in the presence of a solvent; - Mixing 1 to 10%, preferably 1 to 6% wax into the powder composition; - Removing the solvent by drying to obtain an agglomerated powder; - Compressing the agglomerated powder into a strip, sheet, or rod; - Crushing the strip, sheet, or rod into particles in the millimeter diameter range; - Sintering the ceramic-metal particles in a vacuum or inert atmosphere furnace at a temperature of 1200 to 1600 °C until a porosity of less than 5% by volume, preferably less than 3% by volume, and further preferably less than 1% by volume is reached including; - The step of grinding a powder composition containing ceramic particles and the binder metal matrix in the presence of a solvent is carried out until an average particle size D of 1 to 20 μm, preferably 1 to 10 μm, is obtained. 50 The particle size of the powder is measured by laser diffraction using the Mie theory according to the guidelines given in ISO 13320:2020, where the refractive index and absorption rate are adapted to the ceramic particles, the obscuration is in the range of 10 to 15%, and the weighted residual is less than 1%. - The sintered granules crushed from strips, sheets, or rods have a particle size of 0.3 to 10 mm, preferably 0.4 to 6 mm, and the average particle size D 50 is selected from 1 to 6 mm, preferably 1 to 3 mm, and the particle size is measured by dynamic image analysis according to ISO 13322-2:2006 or sieving according to ISO 4497:2020. - Step b) - Mixing the ceramic metal composite material particles obtained according to the said process with an adhesive, preferably an organic adhesive, of about 0.5 to 7% by weight, preferably 1 to 4% by weight; - Injecting and compressing the mixture into a shell shape; - Drying the mixture at a temperature and for a time suitable for removing the solvent of the adhesive or enabling curing by gazing or a catalyst; - Demolding the dried mixture and assembling it into a hollow precast body arranged in a composite material grinding ball type to obtain a three-dimensional interconnected network shell of periodically alternating millimeter ceramic metal composite material particles and millimeter gaps. comprises at least one or a related combination of the features of the method is disclosed.

Brief Description of the Drawings

[0017]

Figure 1

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Figure 10

Figure 11

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Figure 15

Mode for Carrying Out the Invention

[0018] The present invention relates to a metal matrix composite grinding ball, and particularly to a ceramic-reinforced grinding ball manufactured by conventional casting. This consists of a metal core surrounded by a reinforcing shell structure including a network of high-density irregular-shaped ceramic-metal composite material granules having a millimeter average gap of 0.5 to 4 mm, preferably 1 to 3 mm, an air void ratio of less than 5% by volume, preferably less than 3% by volume or less than 2% by volume, more preferably less than 1% by volume, and a particle size distribution of about 0.3 to 10 mm, preferably 0.8 to 6 mm, and an average particle size of 1 to 4 mm, preferably 1 to 3 mm.

[0019] The ceramic-metal composite material granules are composed of ceramic particles fixed in a metal binder matrix, particularly boride, nitride, or carbide particles such as TiC, TiCN, NbC, TaC, WC, preferably titanium carbide, titanium nitride, or titanium carbonitride.

[0020] For wear applications, the ceramic particles provide high wear resistance and the metal improves toughness, among other properties. Depending on those specific applications (required impact resistance, wear resistance, or corrosion resistance), the ceramic-metal composite material particles of the disclosed reinforced grinding balls can be, for example, various proportions of micrometer ceramic particles (having a diameter of about 0.1 - 50 μm, preferably 0.5 - 20 μm, more preferably 1 - 10 μm) fixed in a metal binder phase which can be Fe-based, Ni-based, or Mo-based, and contain 40 - 95 vol%, preferably 60 - 90 vol%, more preferably 70 - 90 vol% of the particles.

[0021] The hollow precast ceramic-metal shell structure / hollow ball is placed in the mold cavity before an iron alloy, preferably chromium cast iron, or steel is poured into the grinding ball mold (cluster type) and infiltrates the gap of the outer ceramic-metal shell structure surrounding the core of the grinding ball. Then, millimeter ceramic-metal granules are completely embedded in the cast metal matrix (see FIGS. 10 and 11). The thickness of the precast shell body is variable and can be selected to be about 2 - 15 mm, preferably 2 - 10 mm, and most preferably 3 - 8 mm.

[0022] The following table shows the theoretically possible reinforcement ratios considering the grinding ball diameter and the thickness of the reinforcing shell. Grinding balls with diameters of 10 - 125 mm are commercialized for various applications, and the most common diameters are shown below. For a grinding ball with a nominal diameter of 80 mm and a reinforcing shell with a thickness of only 5 mm, the proportion of the reinforcing volume already surprisingly represents 33 vol% of the ball volume.

[0023]

Table 1

[0024] In the present invention, expressions such as TiC, TiCN, TiN, WC, WB... should not be understood in a strict stoichiometric chemical sense, but rather as carbides, nitrides, borides... in their crystallographic structures. Titanium carbide, for example, has a wide composition range in which the C / Ti stoichiometry varies from 0.47 to 1, a C / Ti stoichiometry exceeding 0.8 is preferred, and a C / Ti stoichiometry exceeding 0.9 is even better. For example, titanium carbonitride may also be expressed as TiCN or Ti2CN or even Ti(C,N)....

[0025] The volume content of the ceramic-metal composite material particles in the ceramic structure for constructing the outer reinforcing shell of the grinding ball (excluding cases where there are hollow parts such as inflow holes or recesses) is typically 35 to 70% by volume, preferably 40 to 65% by volume, most preferably 45 to 60% by volume, according to their specific applications, and results in an average ceramic particle concentration in the reinforcing volume of 14 to 67% by volume, preferably 24 to 59% by volume, more preferably 30 to 54% by volume.

[0026] The following table shows the volume percentage of ceramic particle content considering the ceramic mass and volume% in the millimeter particles, as well as the packing density of the particles.

[0027]

Table 2

[0028] The reinforced outer portion of the grinding ball is produced from the agglomeration of irregular-shaped millimeter ceramic-metal composite material particles having a particle size distribution of approximately 0.3 to 10 mm, preferably 0.5 to 6 mm, more preferably 0.8 to 4 mm. The average particle size is preferably selected from 1 to 6 mm, more preferably 1 to 3 mm, for example 2 mm, depending on the desired thickness of the shell. Refer to Figure 4. The particle distribution substantially does not contain particles less than 0.3 mm, the proportion of particles less than 0.5 mm is less than 5%, maintaining sufficient gaps that can be infiltrated and filled by the casting metal. The appropriate particle size distribution can be obtained by sieving the particles and adjusted according to the desired packing density represented in the above table.

[0029] The ceramic-metal composite material particles are usually agglomerated into two half-shells (although other assembly configurations are possible) using an adhesive (an inorganic adhesive such as well-known sodium silicate or potassium silicate glass adhesives, or an organic adhesive such as a two-component adhesive that results in polyurethane or phenolic resin). These shells form an open structure of a three-dimensional interconnected network of agglomerated / aggregated ceramic-metal composite material particles bonded by a binder, where the packing of the particles leaves open gaps between the particles and the gaps can be filled by the liquid casting metal (see Figure 3). Combine two half-shells in a 2×2 manner to form a hollow sphere (see Figure 5), place it in the mold before injecting the iron alloy (see Figure 7), and form a ceramic-reinforced grinding ball. The assembly of the shells can be a dovetail assembly or any other suitable assembly that allows for good behavior during the injection of the casting metal. Since the connection between the shell parts is usually a weak point of the precast body, it is preferable to arrange these parts perpendicular to the parting line of the mold, or at least not parallel, in order to avoid additional defects (the parting line of the mold is already a weak point of the conventional grinding ball).

[0030] Next, the liquid metal is injected into the grinding ball mold, and the liquid metal fills the open gaps between the ceramic metal particles. The millimeter intervals should be understood as gaps with an average diameter of 0.5 to 4 mm, preferably 1 to 3 mm, depending on the compression of the ceramic reinforcement structure and the diameter of the particles. The diameter of the ceramic metal composite material particles is selected in relation to the thickness of the reinforcement shell for reasons of mechanical resistance and infiltration. A shell thickness of 3 mm can be achieved with ceramic metal particles having an average diameter of about 1 to 2 mm, while a shell thickness of 10 mm would be achievable with ceramic metal particles having an average diameter of 3 to 6 mm.

[0031] The ceramic metal composite material particles are typically manufactured by powder metallurgy by forming a blend of ceramic powder and metal powder with an appropriate particle size distribution and subsequently liquid phase sintering.

[0032] Typically, the powder has a diameter of 0.1 to 50 μm and includes ceramic particles as the main component and a metal binder that can be 5 to 60 percent of the individual constituent powders or already alloyed powders. The powder is first mixed and / or ground (depending on the initial powder diameter) by dry or wet grinding in a ball mill (e.g., using an alcohol such as isopropyl alcohol to avoid oxidation of the metal powder). Some organic aids may be added for dispersion or shaping purposes. In the case of wet grinding, a drying step may be required. This can be done by any suitable technique, such as vacuum drying or spray drying. Shaping is typically carried out by cold uniaxial isostatic pressing roller compactor, or injection molding, or any other shaping method to form strips, rods, blocks, or sheets.

[0033] For example, the strip or sheet can be easily crushed into granules and optionally sieved. It can be advantageous to achieve an irregular granule shape that does not include granules with an easy extraction direction (granules that are very well mechanically retained in the cast metal) nor rounded-shaped granules (granules that are very well metallurgically retained in the cast metal). The compressed, extruded, or crushed granules are then sintered at an appropriate temperature, preferably under vacuum, an inert gas, or a combination thereof. During liquid phase sintering, particle rearrangement driven by capillary forces that reduce porosity occurs. Crushing after the sintering process is also possible.

[0034] The cast iron alloy that embeds ceramic metal composite material granules and fills the gap in the outer shell of the grinding ball is preferably an iron alloy (chrome white iron, steel, manganese steel...).

[0035] Advantages The present invention enables, by means of conventional casting, obtaining a concentration of ceramic particles that can be extremely high (up to 95% by volume) within the ceramic metal composite material granules, with a low risk of defects (gas holes, cracks, non-uniformities...) in the cast structure.

[0036] In the present invention, through the low porosity of the ceramic metal composite material granules, a good average concentration of ceramic can be achieved within the reinforced outer shell volume of the grinding ball. Depending on the compression / piling and ratio of micrometer ceramic particles in the ceramic metal composite material granules in the outer shell of the grinding ball, a value of up to approximately 67% by volume of ceramic can be reached.

[0037] The grinding ball of the present invention is substantially free of porosity and cracks, resulting in better mechanical and wear characteristics.

[0038] The diameters of the ceramic particles and ceramic-metal composite material particles (ceramic particles + metal binder) of the present invention can be widely controlled during the manufacturing process (selection of raw materials, grinding, sieving, forming process, and firing conditions). By using sintered millimeter ceramic-metal composite material particles produced by powder metallurgy, control of the particle size and porosity, use of metal alloys of various compositions as the binder metal matrix, high concentration of ceramics, easy forming of inserts that do not require a large amount of work, and good internal normality of the particles after injection even under high thermal shock conditions are made possible.

[0039] Manufacture of ceramic-metal composite material particles: Grinding and / or mixing of ceramic powder (40 - 95% by volume, preferably 60 - 90% by volume, more preferably 70 - 90% by volume) and metal powder (5 - 60% by volume, preferably 10 - 40% by volume, more preferably 10 - 30% by volume) as the binder metal matrix is carried out as described above in a ball mill containing a liquid which can be, for example, water or alcohol, depending on the sensitivity of the metal binder to oxidation. Various additives (antioxidants, dispersants, binders, plasticizers, lubricants, waxes for compression) can also be added for various purposes before and after drying.

[0040] When the desired average particle size D 50 is reached (usually less than 20 μm, preferably less than 10 μm, more preferably less than 5 μm), the slurry is dried (e.g., by vacuum drying or spray drying) to achieve agglomerates of the powder containing the above-mentioned organic additives.

[0041] The agglomerated powder is introduced into a roller compactor granulator through a hopper. This machine has two rolls through which the powder passes and is compressed under pressure. At the outlet, a continuous strip (sheet) of the compressed material is obtained, which is then crushed to obtain ceramic-metal composite material particles. These particles are then sieved to the desired diameter. Fractions of unwanted particle sizes are freely reused. The resulting particles usually have a relative density of 40 - 70% (depending on the compression level, powder characteristics, and blend composition).

[0042] Adjust the particle size distribution and shape the particles into cubes or flat shapes according to the grinding method (impact grinding results in more cubic particles, and compression grinding results in more flat particles), or, for example, it is also possible to adjust the particles into rounded shapes by rolling the particles in a drum or on a belt for a sufficient time, or by extending the sieving time or process. Rounded particles are particularly interesting for reducing stress concentration inside the shell (compared to angular particles). The resulting particles generally have a diameter that provides particles of about 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably 1 to 4 mm, and even more preferably 1 to 3 mm after sintering. The particles can also be obtained directly as granules or in a much larger portion that is further ground into particles by classical uniaxial compression or granulation of the powder blend before and after firing.

[0043] Finally, liquid phase sintering is carried out in a furnace at a temperature of 1200 - 1600 °C for several minutes or hours under vacuum, N2, Ar, H2, or a mixture thereof, depending on the metal phase (type and amount of binder) and the type of ceramic particles (carbides, nitrides, carbonitrides, borides...), until the desired porosity is reached, preferably less than 5% by volume, more preferably less than 3% by volume, most preferably less than 2% by volume, and even less than 1% by volume.

[0044] Examples of realizing the ceramic precast body shell structure As described above, the ceramic - metal composite material particles are agglomerated by an adhesive, or by confining them in a mold, or by any other means. The proportion of the adhesive does not exceed 10% by mass based on the total mass of the particles, preferably 0.5 - 7% by mass. This adhesive can be inorganic or organic. An adhesive based on sodium silicate or potassium silicate, or a two - component adhesive that gives a polyurethane or phenolic resin can be used.

[0045] Mix the ceramic-metal composite material particles with a low porosity with an adhesive, place them in a mold, and form, for example, two half-shells (see Fig. 2). After the adhesive has cured (for example, obtained at 100 °C after the water drying of the inorganic silicate adhesive, the adhesive curing can also be obtained, for example, for polyurethane-based adhesives by gasifying with CO2 or amine-based gases, or by adding a catalyst to the adhesive mixture to enable curing over time), the two half-shells are cured and demolded (see Fig. 3), and then can be assembled into a hollow ball-shaped structure having at least one inlet hole (see Fig. 4). Depending on the particle shape, diameter distribution, adhesive content, particle positioning, or vibration during the tapping of the particle bed while making the shell, the interconnected network structure of the ceramic-metal particles is 35 - 70% by volume, most preferably 55% by volume of high-density ceramic-metal particles and 65 - 30% by volume, most preferably 45% by volume of voids (millimeter gaps) in the 3D interconnected network.

[0046] Casting of Grinding Balls in Cluster Type Grinding balls are usually cast in a plurality of mold structures, also commonly called "cluster type". In such molds, usually, up to 40 grinding balls of 40 mm and up to 16 grinding balls of 100 mm can be cast in one casting operation. See Fig. 9. Grinding balls of different diameters can also be cast together in the same cluster type mold.

[0047] The assembled half-shell of the ceramic-metal particle structure forms a hollow sphere (hollow ball-shaped precast structure) and includes one or two openings (inlet holes) for introducing liquid casting metal, and is placed in the cavity of a conventional sand mold or metal shell mold. Then, a high-temperature liquid ferroalloy, preferably chrome white iron or steel, is poured into the grinding ball cluster mold.

[0048] Therefore, the high-temperature liquid ferroalloy penetrates into the millimeter gaps between the ceramic metal particles of the reinforcing shell structure and fills them. When using an organic adhesive, surface partial melting of the metal binder matrix on the particle surface by the casting alloy, or the mutual diffusion of elements between the two alloys, induces a very strong bond between the particles and the cast ferroalloy matrix.

[0049] Next, the sand mold is removed, and the grinding balls are cleaned from the remaining sand and can follow the normal finishing casting process steps known to those skilled in the art (additional heat treatments such as knockout, shot blasting, grinding, annealing, quenching, tempering... etc.).

[0050] Measurement method For porosity, particle size or grain size measurement, a sample without grinding marks and polishing marks is prepared for metallographic examination. Care must be taken to avoid tearing of particles that may lead to an evaluation that causes misunderstanding of the porosity. Guidelines for specimen preparation can be found in ISO 4499-1:2020 as well as ISO 4499-3:2016, 8.1 and 8.2.

[0051] Porosity determination: The volume fraction of the porosity of the free particles can be calculated from the measured density and the theoretical density of the free particles before casting.

[0052] The measurement of the volume fraction of the porosity of the particles embedded in the metal matrix is based on Annex 2 of ISO 13383-2:2012. This standard is particularly applicable to fine ceramics, but the described method for measuring the volume fraction of porosity can also be applied to other materials. Since the samples here are not pure fine ceramics but hard metal composites, sample preparation should be carried out in accordance with ISO 4499-1:2020 as well as ISO 4499-3:2016, 8.1 and 8.2. Etching is not necessary for porosity measurement but can be carried out as it does not change the measurement results.

[0053] Average ceramic particle size D 50 : The average particle size of the fixed ceramic particles is calculated by the linear-intercept method in accordance with ISO 4499-3:2016. Five images from the microstructure of five different grains are taken with an optical microscope or an electron microscope at a known magnification so that there are 10 to 20 ceramic particles across the field of view. Four line cutting lines are drawn across each calibrated image so that the lines do not cross any individual particle more than twice.

[0054] When a line cuts through a ceramic particle, the length (l i ) of that line is measured using a calibrated scale (for the first, second, third,..., nth grains, i = 1, 2, 3... n). Incomplete particles touching the edge of the image must be ignored. At least 200 particles must be counted.

[0055] The average line intercept particle size is defined as follows:

[0056]

Equation

[0057] Average particle size D of ceramic-metal particles 50 Measurement One or more micrographs of the polished cross-section of the sample are produced using a computer program and an optical microscope (e.g., a typical field-of-view image obtained by Alicona Infinite Focus). All the micrographs contain at least 250 different ceramic-metal particles. Appropriate thresholding makes it possible to segment the grayscale image into features of interest (particles) and the background (see Figure 11). If the thresholding is not consistent due to poor image quality, a manual stage involving manually drawing the particles, scale bars (if present), and the image border on tracing paper and then scanning the tracing paper is used.

[0058] The Feret diameter, which is the distance between two tangents arranged perpendicular to the measurement direction, is measured in all directions for each particle by image analysis software (e.g., ImageJ). An example is shown in Fig. 15.

[0059] Determine the minimum Feret diameter of each particle in the image. The minimum Feret diameter is the shortest Feret diameter among the set of measured Feret diameters. At least 250 different particles must be measured. Particles touching the edge of the image must be ignored. Let the value of the minimum Feret diameter of each particle be the equivalent diameter x. Then, calculate the volume diameter distribution q3(x) of the particles based on a sphere of diameter x. The D of the particles 50 is to be understood as the volume-weighted mean diameter x according to ISO 9276-2:2014 - 1,3 should be.

[0060] Average particle size D of ceramic-metal composite particles during particle manufacturing 50 Measurement: The particle size can be measured by dynamic image analysis according to ISO 13322-2:2006 using a Camsizer manufactured by Retsch or an equivalent device. The particle diameter used for the diameter distribution is the shortest code measured in the set of the maximum codes of the particle projection, which is X Cmin in the case of results close to screening / sieving.

[0061] Particle size D 50 is the volume-weighted mean diameter of the volume distribution based on X Cmin The average particle size and distribution of the particles can also be measured by sieving according to ISO 4497:2020.

[0062] Measurement of the particle size of the powder during grinding: The particle size of the powder during grinding is measured by laser diffraction using the MIE theory according to the guidelines given in ISO 13320:2020 by a Mastersizer 2000 manufactured by Malvern. The refractive index and absorption rate should be set according to the measured material. For example, the refractive index of TiC is set to 3 and the absorption rate is set to 1. The obscuration should be in the range of 10 - 15%, and the weighted residual should be less than 1%.

Example

[0063] Grinding balls are usually exposed to various stresses and are segmented in application fields where either corrosion resistance, wear resistance, or impact resistance is privileged. Therefore, grinding balls are supplied according to specific uses where one or more of the above wear mechanisms are present. Nevertheless, grinding balls are not only made to fit the material being ground but also to fit specific grinding machines where diameter, liner, and volume filling play important roles. Therefore, the performance comparison between the grinding balls of the present invention and those of the prior art must be made in specific situations of the expected results from the perspective of corrosion resistance, wear resistance, or impact resistance within a specific grinding environment.

[0064] Examples of grinding balls implemented for actual life tests on industrial grinding machines This example is illustrative for the present disclosure but should not be considered limiting.

[0065] Preparation of ceramic - metal composite material particles The following raw material powders were used for four different types of ceramic - metal composite material particles 1 - 4, and all powders had a particle size of less than 44 μm. ·TiC, TiC 0.5 ,N 0.5 , WC, NbC, Mo2C, iron, manganese, chromium, nickel.

[0066]

Table 3

[0067] The composition of the ceramic-metal composite material particles 1 has a low content of ceramic particles fixed in a tough manganese steel binder matrix (45% by mass of TiC), and is particularly suitable for impact resistance.

[0068] The compositions of the ceramic-metal composite material particles 2 and 3 have a high content of ceramic particles fixed in a hard high-chromium white iron wear-resistant binder matrix (85% by mass of TiC), and are particularly suitable for wear resistance.

[0069] The composition of the ceramic-metal composite material particles 4 has a high content of a composite mixture of ceramic particles finely adjusted to be fixed in a corrosion-resistant nickel binder (TiC 0.5 N 0.5 +WC+NbC+Mo2C = 85% by mass in total), and is particularly suitable for corrosion resistance and wear. Other ceramic particles can be added to create composite material solid solution particles and control or finely adjust the particle size, morphology, and / or core-shell structure of the hard ceramic particles.

[0070] Powders with the compositions in table 1 (Table 1) were mixed and ground in a ball mill containing isopropyl alcohol and metal grinding balls for 24 hours to make the average particle size D 50 about 3 μm.

[0071] Add 2% by mass of an organic wax binder in powder form and mix it with the resulting powder. Remove alcohol using a vacuum dryer with a rotating blade (the alcohol is condensed and reused). Next, sieve the resulting agglomerated powder through a 500 μm sieve. Produce strips at 60% of the theoretical density of the ceramic / metal powder mixture by compression between the rotating rolls of a roller compactor granulator. Then, crush the strips into irregularly shaped granules by forcing them through a sieve of an appropriate mesh size. After crushing, sieve the granules to obtain the required particle size distribution. Next, sinter these irregularly shaped porous granules in a high vacuum furnace at a high temperature (a typical temperature-time pair is, for example, 1430 °C for 2 hours) at a low partial pressure of argon until a minimum porosity (less than 5% by volume), preferably less than 3% by volume, and more preferably less than 1% by volume is reached.

[0072] Next, sintered granules with a low porosity of less than 5% by volume are mixed with approximately 1% by mass of a two-component polyurethane-based adhesive (composed of, for example, a mixture of 50% by mass of AVECURE 335 F PART 1 - aromatic hydrocarbon, phenol, 2-butoxyethyl acetate and 50% by mass of AVECURE 635 F PART 2 - diphenylmethane diisocyanate, manufactured by ASK chemicals) and injected into a silicone or plastic mold of the desired shape (vibration or pressure can be applied to facilitate filling and packing of the mold and ensure that all granules are correctly packed) (refer to the half-shell mold in Figure 2). Then, ethyl dimethylamine gas (for example, AVECURE 3D manufactured by ASK Chemicals) is used as a catalyst to cure the polyurethane, and once the shell is hard enough, it can be demolded. Such operations can be easily automated with a core shooting machine widely used in casting operations.

[0073] These shells contain approximately 55% by volume of high-density ceramic-metal composite material particles (with approximately 45% by volume void / mm gaps between the particles), as shown in Figures 5 and 6. Each precast hollow ball ceramic-metal particle structure is placed in a grinding ball cluster type cavity (see Figure 7). Then, high-temperature liquid high-chromium white iron (alloy 1, alloy 2, or alloy 3) with an appropriate composition is poured into the mold according to the test conditions. The high-temperature liquid high-chromium white iron fills the millimeter gaps between the particles of the reinforcing shell of the grinding balls.

[0074] Casting alloys used for injecting the grinding balls of Examples 1 to 4

[0075] [Table 4]

[0076] (Example 1) (Alloy 1 + Particle Composition 1) Alloy 1 contains 2.2% by mass of C and 16.5% by mass of Cr and is particularly suitable for impact conditions with appropriate heat treatment to improve impact resistance. Shells are made using the particles of Composition 1. The composite material grinding balls and the reference metal grinding balls are compared together in the same ball mill for the same period while processing the same platinum ore under significant impact conditions.

[0077] (Examples 2 and 3) (Alloy 2 + Particle Compositions 2 and 3) Alloy 2 contains 2.85% by mass of C and 14.5% by mass of Cr and is particularly suitable for wear conditions with appropriate heat treatment to improve wear resistance. Shells are made using the particles of Compositions 2 and 3. The composite material balls and the reference metal balls are compared in the same ball mill containing copper ore under significant wear conditions.

[0078] (Example 4) (Alloy 3 + Particle Composition 4) Alloy 3 contains 2.3% by mass of C and 29% by mass of Cr and is particularly suitable for high corrosion conditions. A shell is made using the granules of Composition 4. The composite material balls and the reference metal balls are compared in the same ball mill containing magnetite under significant corrosion conditions.

[0079] It should be understood that due to other elements, Alloys 1, 2, and 3 also contain less than 2% by mass of other normal alloying elements (Si, Mn, Mo, Ni,...) known to those skilled in the art depending on specific properties and heat treatments for specific purposes.

[0080] After injection, 47 - 58% by volume of the shell is ceramic - metal granules containing a high concentration of about 57 - 89% by volume of micrometer - sized ceramic particles (titanium carbide, titanium carbonitride, niobium carbide, tungsten carbide... and / or mixtures / combinations, etc.) fixed in the binder - metal matrix. The overall volume content of ceramic particles in the reinforced shell after injection of the grinding balls varies from about 27 - 52% by volume in Examples 1 - 4, but can reach even higher values.

[0081] In the following table, all variables necessary for the calculation of all relevant parameters are shown. The word "granules" in the table represents ceramic - metal composite material granules. The density and porosity of these granules are interdependent.

[0082] Summary of the specificities of the grinding balls for each example in the test.

[0083]

Table 5

[0084] Performance index calculated compared to conventional grinding balls The paper "Overview of grinding media consumption in comminution" (Slabbert, Paton, Moema and Zimba) World Gold Conference shows an overview of the tests of grinding media.

[0085] The actual life test of the grinding balls of an industrial grinding machine is particularly difficult to manage because the proportion of test grinding balls is low compared to the loading amount of conventional grinding balls. Since the grinding machine contains grinding balls that are worn at various stages with a large diameter size distribution (e.g., diameter 10 - 70 mm), the test sample generally represents less than 0.1% (400 balls out of 400,000 - 800,000 balls). The main difficulty here is to find at least a significant number of composite material balls and reference balls among thousands of conventional grinding balls after grinding for several days or weeks, so as to be able to measure the representative average mass loss rate of the composite material test balls compared with the reference metal grinding balls.

[0086] The secret to solving this problem here is to use a grinding ball diameter that is slightly larger (about 10 mm larger) than what is regularly added and what already exists in the conventional grinding machine. For example, if the diameter of the fresh conventional grinding balls regularly added to an industrial grinding machine is 60 mm, a diameter of 70 mm is selected for the test grinding balls (composite material grinding balls and reference grinding balls) to make it easier to recover the marked balls. Since these balls are larger, they are not only easier to find visually but also have a natural tendency to "float" on the surface of the conventional grinding load.

[0087] The evaluation of the wear performance of the grinding balls of the present disclosure was carried out in the actual life situation of grinding copper ore, magnetite, and platinum ore in three industrial mills A; B; C (having the following characteristics and conditions):

[0088] Grinding of copper ore in the presence of the grinding balls of Example 2, followed by testing with the grinding balls of Example 3 (both with a diameter of 90 mm) - Mill A with a diameter of 7.31 m and a length of 10.97 m - Containing 660 tons of conventional grinding balls (filling rate 33% by volume) - Regularly adding several tons of conventional grinding balls with a diameter of 76 mm per day to offset wear - Rotation speed 11.9 rpm - Extract 10500 kW of power - Process 950 T / h of copper ore - Use wear conditions - Test duration: 8 days

[0089] Grinding of magnetite in the presence of the grinding ball (70 mm) of Example 4 - Mill B with a diameter of 4.6 m and a length of 6.7 m - Filling with 165 tons of conventional grinding balls (filling rate 35% by volume) - Periodically add several tons of conventional grinding balls with a diameter of 60 mm per day to offset wear - Rotate at a speed of 15.1 rpm - Extract 2300 kW of power - Process 420 T / h of magnetite - Use corrosion conditions - Test duration: 20 days

[0090] Grinding of platinum ore in the presence of the grinding ball (80 mm) of Example 1 - Mill C with a diameter of 7.925 m and a length of 11.735 m - Filling with 800 tons of conventional grinding balls (filling rate 32% by volume) - Periodically add several tons of conventional grinding balls with a diameter of 70 mm per day to offset wear - Rotate at a speed of 10.5 - 11.5 rpm - Extract 15000 kW of power - Process 1000 T / h of platinum ore - Use impact conditions - Test duration: 10 days

[0091] Preparation of test samples For the performance tests of the composite material grinding balls of Examples 1 to 4 and the metal reference ball types, 200 grinding balls of all the examples are manufactured, and each grinding ball of the same alloy and reinforcement is marked with the same identification means (for example, one or two drill holes of defined diameter and position in all the grinding balls of Example 1; two holes of different diameters and positions in all the grinding balls of Example 2, etc.). All the grinding balls of the same composition are further machined or ground to have the same mass (±2 kg for a grinding ball with a diameter of 80 mm) with a tolerance of ±5 grams, preferably ±2 grams. The composite material grinding balls and the reference metal grinding balls of the present disclosure are manufactured from the same ferroalloy and are subjected to the same heat treatment so as to be able to evaluate the influence of the reinforcement as the only variable.

[0092] In the next step, 200 composite material test grinding balls and 200 reference metal grinding balls are loaded together into an industrial mill (the composite material balls of Example 1 are in Mill C, the composite material balls of Examples 2 and 3 are in Mill A, and the composite material balls of Example 4 are in Mill B). The composite material balls of Examples 2 and 3 are separately (sequentially) tested in Mill A using 200 reference metal grinding balls each time.

[0093] The above-mentioned industrial mill already contains conventional grinding balls with a normal loading amount at a filling rate of about 35% by volume. This represents 600 tons of conventional grinding balls for Mill A, 165 tons for Mill B, and 800 tons for Mill C. However, the amount of the composite material grinding balls and the reference grinding balls (200 composite material grinding balls and 200 reference balls for each mill) only represents about 600 - 900 kg. Therefore, the influence on the grinding capacity can be ignored. Thus, the addition of the test grinding balls (composite material grinding balls and reference grinding balls) does not significantly affect the overall mill filling rate.

[0094] Thereafter, the mill needs to be operated for a period sufficient to observe wear that is measurable. The required period is generally about several days or weeks under the condition of 24 hours per day.

[0095] Depending on the type of ore to be ground, the wear of conventional grinding balls in magnetite is known to be about 0.5 mm / 100 h in diameter (about 2.4 mm after 20 days), but in the case of copper ore, it has been observed to be about 1.5 mm / 100 h in diameter (about 3 mm after 8 days). In the case of platinum ore, the wear is expected to be about 1.3 mm / 100 hours (about 3 mm after 10 days). This index regarding the wear rate of conventional grinding balls was considered to select the test duration to ensure that the wear remains in the reinforcing shell thickness in order to appropriately interpret the effect of the reinforcing shell itself.

[0096] Finally, the mill was stopped, and the discovered and identified test grinding balls (usually less than 10% of the starting amount) were weighted to evaluate the average mass loss and calculate the performance index shown in the following result table.

[0097] Performance Index Calculation For each example of the grinding ball, the average mass loss was measured before and after the test duration, and the average mass loss rate was calculated. Mass loss rate = (Initial mass - Final mass) / Initial mass The performance index is defined as follows, and the reference mass loss is the average mass loss of the reference metal grinding ball. PI = Average mass loss of reference metal grinding ball / Average mass loss of test composite material grinding ball

[0098] A performance index greater than 1 means that the test composite material grinding ball according to the present invention wears less than the reference, and less than 1 means that the test composite material grinding ball wears more than the reference. The reference grinding ball is a conventional grinding ball made of the same cast alloy but without ceramic reinforcement.

[0099] As shown in the following table, the grinding balls of the present invention generally show better performance due to the reinforcing shell.

[0100]

Table 6

[0101] As described above, when comparing the performance of the composite material grinding ball of the present disclosure with that of the conventional grinding ball while the reinforcing shell has not completely worn out and while it has completely disappeared, the thickness of the reinforcing shell naturally affects the overall performance of the grinding ball. A grinding ball having a composite reinforcing shell with a thickness of 10 mm has better long-term performance than that equivalent to a reinforcing shell with a thickness of 5 mm.

[0102] Effect of performance index on overall grinding performance The following table compares the wear of Examples 1-4 (composite material grinding balls) with their respective reference grinding balls in terms of the average mass loss rate. The extension of the lifespan is calculated considering the performance index and its influence on the lifespan of the grinding ball.

[0103] The lifespan of the grinding ball is usually evaluated as the time required for the ball to wear from its initial diameter to 20 mm. When the diameter of the grinding ball reaches 20 mm, the ball is considered small enough to exit the mill with the grinding material through the outlet trunnion.

[0104] The measured mass loss is converted to a decrease in diameter per unit time to enable the calculation of the extended lifespan.

[0105] A significant increase in lifespan due to the reinforcing shell structure is observed, which enables the grinding ball to maintain a diameter close to its original value for a longer period.

[0106]

Table 7

[0107] Examples 1-4 show significantly superior performance of the composite core-shell grinding balls using various compositions and properties of the granules, casting alloys, and test conditions. Example 3 shows the best performance of the composite shell in the case of granules without significant porosity. The performance index of Example 2 shows the influence of higher porosity in the granules.

[0108] Advantages of the present invention The present invention has the following advantages compared to conventional grinding balls: - Good wear performance efficiency (reinforcement is unnecessary even if there is reinforcement throughout the ball) due to the good wear performance of the shell layer that occupies most of the wear volume. - By adjusting the properties, diameter, and volume content of ceramic particles and combining them with a suitable metal binder matrix for ceramic-metal composite particles, such as a high manganese steel with high mechanical properties combined with a suitable iron casting alloy such as high chromium white iron for wear parts (the binder metal matrix is probably different from and complementary to the cast ferroalloy metal matrix), excellent wear performance and / or mechanical properties of the composite grinding ball. - Excellent wear performance and / or mechanical properties of the grinding ball due to the controlled porosity and / or crack defects of the particles before injection. - Easy / simple process.

[0109] Clause The present disclosure of the metal-ceramic composite grinding ball can also be described as follows:

[0110] A metal matrix composite grinding ball having a ceramic-reinforced shell structure of millimeter ceramic-metal particles with a porosity of less than 5%, preferably less than 3% by volume, and most preferably less than 1% by volume. The millimeter particles contain ceramic particles fixed in a binder metal matrix at a concentration of more than 40%, and the reinforcing outer shell has a thickness of 2 to 20 mm, preferably 3 to 15 mm, more preferably 4 to 12 mm, and the reinforcing volume represents more than 10% by volume, preferably more than 15% of the total volume of the grinding ball.

[0111] A metal matrix composite grinding ball having a core-shell structure, wherein the shell contains a ceramic reinforcing material, the ceramic reinforcing material includes a ceramic-metal composite particle and an interconnected network of gaps, and one or two substantially spherical surfaces that do not contain the ceramic reinforcing material, and the spherical surface represents less than 10% of the entire surface of the shell, and the ceramic-metal composite particles have an average diameter D of 2 to 5 mm, preferably 2 to 3 mm 50 and exhibit an average diameter D of the gap of 0.5 to 3 mm50 exhibits; The ceramic-metal composite material particles contain at least 40% by volume, preferably at least 65% by volume, and most preferably at least 85% by volume of ceramic particles fixed in a binder metal matrix. The ceramic particles have an average diameter D of 2 to 5 μm 50 has; The ceramic-metal composite material particles have a volume fraction of porosity of less than 5% by volume, preferably less than 3% by volume, and most preferably less than 1% by volume, measured in accordance with ISO 13383-2:2012; The network of composite material particles and gaps is embedded in an iron alloy cast metal matrix, and the iron alloy cast metal matrix infiltrates and fills the gaps between the interconnected composite material particles of the three-dimensional network; The shell contains a ceramic reinforcing material including a volume content of at least 40% by volume, preferably at least 45% by volume of ceramic-metal composite material particles, The ceramic reinforcing material of the shell covers the largest part of the outer surface of the grinding ball, excluding a small surface by one or two inlet holes, Metal matrix composite grinding ball.

Claims

1. A composite material grinding ball having a core-shell structure, wherein the shell of the core-shell structure contains a ceramic reinforcing material, and the ceramic reinforcing material is a three-dimensional interconnected network of periodically alternating ceramic-metal composite material particles and gaps, and the ceramic-metal composite material particles and gaps have an average diameter within the millimeter range, the network including; the ceramic-metal composite material particles contain at least 40% by volume, preferably at least 60% by volume, and most preferably at least 70% by volume of ceramic particles fixed in a binder metal matrix, and the ceramic particles have an average diameter within the micrometer range; the three-dimensional interconnected network of ceramic-metal composite material particles and gaps is embedded in an iron alloy cast metal matrix, and the iron alloy cast metal matrix fills the gaps between the interconnected ceramic-metal composite material particles of the three-dimensional interconnected network; the ceramic-metal composite material particles embedded in the iron alloy cast metal matrix have a volume fraction of porosity of less than 5% by volume, preferably less than 3% by volume, and most preferably less than 1% by volume, and the porosity measurement is based on Annex A of ISO 13383-2:2012; the shell includes a volume content of at least 35% by volume, preferably at least 45% by volume of ceramic-metal composite material particles; the ceramic reinforcing material of the shell covers at least 85%, preferably 90%, and most preferably 95% of the entire surface of the grinding ball. Composite material grinding ball.

2. The composite material grinding ball according to claim 1, wherein the ceramic particles are selected from the group consisting of carbides, nitrides, carbonitrides, and borides, or mixtures thereof.

3. The composite material grinding ball according to claim 1 or 2, wherein the ceramic particles are selected from the group consisting of titanium carbide, titanium carbonitride, tungsten carbide, niobium carbide, tantalum carbide, vanadium carbide, zirconium carbide, hafnium carbide, and molybdenum carbide.

4. The composite material grinding ball according to any one of claims 1 to 3, wherein the thickness of the ceramic reinforcing shell ranges from 2 to 15 mm, preferably 2 to 10 mm, and most preferably 3 to 8 mm.

5. The embedded ceramic metal composite material particles have a particle size volume distribution of 0.3 to 10 mm and an average particle size D of 1 to 4 mm, preferably 1 to 3 mm ５０ and the average particle size D ５０ can be measured by performing a micrograph view such that at least 250 ceramic metal composite material particles are present over the field of view of one or more polished cross-sections of one or more samples, using a computer program and an optical microscope, and appropriate thresholds enable segmentation of the particles into a grayscale image and a background. The composite material grinding ball according to any one of claims 1 to 4

6. The fixed ceramic particles in the binder metal matrix have a particle size of 0.1 to 50 μm, preferably 0.1 to 30 μm, and an average particle size D of 0.5 to 20 μm, preferably 1 to 10 μm. ５０ The composite material grinding ball according to any one of claims 1 to 5, having the above characteristics.

7. The composite material grinding ball according to any one of claims 1 to 6, wherein the binder metal matrix is selected from the group consisting of ferromanganese-based alloys, ferrochrome-based alloys, and nickel-based alloys.

8. The composite material grinding ball according to any one of claims 1 to 7, wherein the ferroalloy cast metal matrix contains high-chromium white iron containing at least 11% by mass of chromium or steel.

9. A method for manufacturing the composite material grinding ball according to any one of claims 1 to 8, comprising: a) preparing or manufacturing ceramic-metal composite material particles containing at least 40% by volume of micrometer ceramic particles fixed in a binder metal matrix, wherein the ceramic-metal composite material particles have a porosity of less than 5% by volume, preferably less than 3% by volume, particularly less than 1% by volume; b) manufacturing a ceramic precast body shell in the form of a preferably half-shell of a three-dimensional interconnected network of millimeter ceramic-metal composite material particles and millimeter gaps obtained in step a), which are periodically alternating; c) assembling the shell obtained in step b) into a hollow sphere including one or two inflow openings, and placing the hollow sphere in a cavity of a mold of the grinding ball to be cast; d) injecting the grinding ball, and simultaneously infiltrating the millimeter gaps of the three-dimensional interconnected network of the shell arranged according to step c) with a ferroalloy cast metal matrix; e) demolding the composite material grinding ball A method for manufacturing a composite material grinding ball.

10. The method for manufacturing the ceramic-metal composite material particles in step a) is: - grinding a powder composition containing the ceramic particles and the binder metal matrix in the presence of a solvent; - mixing 1 to 10%, preferably 1 to 6% of wax into the powder composition; - removing the solvent by drying to obtain an agglomerated powder; - compressing the agglomerated powder into a strip, sheet, or rod; - pulverizing the strip, sheet, or rod into particles in the millimeter diameter range; - sintering the ceramic-metal particles at a temperature of 1200 to 1600 °C in a vacuum or inert atmosphere furnace until a porosity of less than 5% by volume, preferably less than 3% by volume, and further preferably less than 1% by volume is reached A method for manufacturing a composite material grinding ball according to claim 9, comprising

11. The step of grinding the powder composition comprising the ceramic particles and the binder metal matrix in the presence of a solvent is carried out until an average particle size D of 1 to 20 μm, preferably 1 to 10 μm is obtained. ５０ The method according to claim 10, wherein the particle size of the powder is measured by laser diffraction using the Mie theory according to the guidelines given in ISO 13320:2020, where the refractive index and absorption rate are adapted to the ceramic particles, the obscuration is in the range of 10 to 15%, and the weighted residual is less than 1%.

12. The sintered granules crushed from the strip, sheet, or rod have a particle size of 0.3 to 10 mm, preferably 0.4 to 6 mm, and the average particle size D ５０ is selected from 1 to 6 mm, preferably 1 to 3 mm, and the particle size is measured by dynamic image analysis according to ISO 13322-2:2006 or sieving according to ISO 4497:2020, the method according to claim 10 or 11.

13. where step b) is - a step of mixing ceramic metal composite material particles obtained according to claim 8 with an adhesive of about 0.5 to 7% by mass, preferably 1 to 4% by mass, preferably an organic adhesive; - a step of injecting and compressing the mixture into a shell type; - a step of drying the mixture at a temperature and for a time suitable for removing the solvent of the adhesive or enabling curing by gauging or a catalyst; - a step of demolding the dried mixture and obtaining a shell of the three-dimensional interconnected network of periodically alternating millimeter ceramic metal composite material particles and millimeter gaps, and assembling it into a hollow precast body placed in a composite material grinding ball mold A method for manufacturing a composite material grinding ball according to claim 10, comprising

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