A method for precipitating spessartine crystals on the surface of ZTA particles

Abstract

The present invention provides a method for precipitating spessartine crystals on the surface of ZTA particles, comprising the following steps: melting a crystallizing agent, rapidly cooling the mixture, and then ball milling the mixture to obtain a glass powder; coating the glass powder on the surface of the ZTA particles; heating the ZTA particles coated with the glass powder to 850-900° C. and maintaining the temperature to precipitate spessartine crystals on the surface of the ZTA particles; wherein the crystallizing agent comprises 60-65wt% boron glass powder, 10-15wt% ammonium dihydrogen phosphate, 10-15wt% sodium carbonate, 8-12wt% manganese dioxide, and 5-8wt% calcium fluoride.

Description

Technical Field

[0001] The present invention relates to a surface crystallization treatment method for zirconium oxide toughened alumina (ZTA) ceramic particles, in particular to a surface crystallization treatment method for ZTA particles used for preparing ceramic iron-based composite wear-resistant materials, belonging to the field of material surface treatment. Background Art

[0002] Currently, the core wear-resistant parts of crushing and grinding equipment in the thermal power generation, mining, and cement industries, such as crusher hammers, particle plates, ball mill liners, crusher cones, vertical mill plates, and grinding rollers, are mostly still made of single-performance metal wear-resistant materials such as high-chromium cast iron, medium-chromium steel, high-manganese steel, and ultra-high manganese steel. These wear-resistant parts are formed by direct casting. These materials all have excellent wear resistance compared to metal materials. However, because the mineral raw materials used in thermal power generation, mining, and cement production are harder than existing metal wear-resistant materials, wear-resistant parts are prone to premature wear and failure during service, making it difficult to meet the operating requirements of crushing and grinding equipment. Single-performance iron-based wear-resistant materials can no longer meet the demands of these operating conditions. Ceramic particle-reinforced metal-based composites, which combine the toughness of metal with the high hardness and wear resistance of ceramics, are gradually being used in the core wear-resistant parts of crushing and grinding equipment. Compared with pure Al2O3 ceramics, ZrO2 toughened Al2O3 (ZTA) ceramics greatly improve the fracture toughness of the ceramic phase through tetragonal ZrO2 stress-induced phase transformation toughening and microcrack toughening. It is a ceramic reinforcement phase of the commonly used iron-based composite wear-resistant materials.

[0003] The infiltration casting method is the most common method for producing large ZTA / Fe-based composite wear-resistant components. The specific process is as follows: ZTA ceramic particles are first mixed with a certain proportion of ceramic binder to form a porous ceramic preform. The porous preform is then fixed to a designated location in a sand mold. Molten Fe metal is then poured to produce the ZTA ceramic particle-reinforced Fe-based composite. This process offers the advantages of simplicity and the ability to produce large, complex ZTA / Fe-based composites. However, due to the poor wettability of ZTA ceramic particles with molten Fe water, the bonding strength between the ZTA particles and the Fe matrix after casting is low. During use, the composite wear-resistant material is prone to premature detachment of ZTA particles from the matrix surface, reducing the wear resistance of the composite and shortening the service life of the wear-resistant component. Summary of the Invention

[0004] The present invention provides a method for precipitating spessartine crystals on the surface of ZTA ceramic particles. This method can produce a large amount of spessartine Mn₃Al₂(SiO₄)₃ crystals on the surface of the ZTA ceramic particles. The ZTA / Fe-based composite material prepared using these ZTA ceramic particles exhibits significantly improved wear resistance.

[0005] The technical solutions provided by the present invention are as follows:

[0006] A method for precipitating spessartine crystals on the surface of ZTA particles comprises the following steps:

[0007] After melting the crystallization agent, rapidly cooling it and then ball milling it to obtain glass powder;

[0008] Coating the glass powder on the surface of ZTA particles;

[0009] Heating the ZTA particles coated with the glass powder to 850-900° C. and maintaining the temperature to precipitate spessartine crystals on the surface of the ZTA particles;

[0010] The crystallizing agent comprises 60-65 wt % of boron glass powder, 10-15 wt % of ammonium dihydrogen phosphate, 10-15 wt % of sodium carbonate, 8-12 wt % of manganese dioxide and 5-8 wt % of calcium fluoride.

[0011] The particle size of the ZTA particles is 12-16 mesh;

[0012] The melting temperature rise rate is 3-6°C / min;

[0013] The melting temperature is 1200-1250°C;

[0014] The holding time of the melting is 2-3 hours.

[0015] The rapid cooling includes air cooling;

[0016] The step of heating the ZTA particles coated with the glass powder to 850-900° C. and keeping the temperature therein comprises heating the ZTA particles coated with the glass powder to 850-900° C. at a heating rate of 3-6° C. / min and keeping the temperature therein for 3-6 hours.

[0017] The ball-to-material ratio of the ball mill is 1.2:1;

[0018] The ball milling medium includes ethanol;

[0019] The ratio of the ball mill medium to the grinding balls is 1:1.2;

[0020] The ball milling speed is 300-360 r / min;

[0021] The ball milling time is 4-6 hours.

[0022] The method comprises the steps of mixing ZTA particles and a coating agent under stirring, adding the glass and then solidifying the mixture to coat the surface of the ZTA particles with glass powder.

[0023] The coating agent includes phenolic resin;

[0024] The amount of the coating agent added is 4-6 wt% of the ZTA particles;

[0025] The stirring speed is 60-100 r / min;

[0026] The stirring time is 0.5-1h;

[0027] The curing time is 6-10h;

[0028] The curing temperature is 80-120°C.

[0029] The method for precipitating spessartine crystals on the surface of ZTA particles further includes a pre-cleaning step.

[0030] The pre-cleaning comprises the steps of soaking the ZTA ceramic particles in an organic solvent, cleaning them under ultrasonic conditions, rinsing the ZTA ceramic particles with water until they are neutral, and drying them;

[0031] The organic solvent includes ethanol;

[0032] The frequency of the ultrasound is 2000-4000 Hz;

[0033] The ultrasound time is 20-40 minutes;

[0034] The drying temperature is 60-80°C.

[0035] The method for precipitating spessartine crystals on the surface of ZTA particles further includes a post-cleaning step.

[0036] The post-cleaning step comprises soaking the ZTA particles with spessartine crystals precipitated on the surface in water at 80-90° C. for 12-24 hours, then soaking them in an alkaline solution with a pH value of 12-13, and then washing them with water until the solution is neutral and then ultrasonically cleaning them.

[0037] The mass of the ZTA particles is less than 20% of the mass of water at 80-90°C;

[0038] The soaking time is 1-2 hours;

[0039] The frequency of the ultrasonic cleaning is 2000-4000 Hz;

[0040] The ultrasonic cleaning time is 1-2 hours.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The method provided by the present invention can precipitate a large number of spessartine crystals on the surface of ZTA ceramic particles. The spessartine crystals on the surface of the ZTA ceramic particles can effectively increase the wettability of the ZTA particles by molten iron. Therefore, when the ZTA ceramic particles prepared by this method are composited with an iron matrix using a cast-infiltration method, the bonding between the Fe matrix and the ZTA particles in the composite material is improved, preventing the ZTA particles from prematurely falling out of the Fe matrix during service, thereby improving the wear resistance of the ZTA / Fe-based composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The XRD pattern of the ZTA particles prepared in Example 1 is shown. Figure 1 It can be seen that the spessartine phase [Mn3Al2(SiO4)3] exists in the ZTA particles after cleaning.

[0044] Figure 2 The low magnification surface morphology of the ZTA particles prepared in Example 1 is shown. Figure 2 It shows that there are a large number of fine grains on the surface of the ZTA particles prepared in Example 1.

[0045] Figure 3 The surface morphology of the ZTA particles prepared in Example 1 is shown at a high magnification. Figure 3 It can be seen that there are a large number of flaky grains on the surface of the ZTA particles prepared in Example 1.

[0046] Figure 4 The micro-area element analysis of the surface grains of the ZTA particles prepared in Example 1 at a high magnification is shown. The micro-area element analysis shows the presence of elements such as Al, Si, O, and Mn. Figure 1 、 Figure 3 and Figure 4 It can be determined that the plate-like crystals on the surface of ZTA particles are spessartine phase [Mn3Al2(SiO4)3].

[0047] Figure 5 The bonding interface between the ZTA particles and the Fe matrix in the ZTA / Fe-based composite material prepared using the ZTA particles prepared in Example 1 is shown. Figure 5 The results show that the interface between the ZTA particles and the Fe matrix after crystallization treatment has good wettability and dense interface bonding, without defects such as pores and inclusions.

[0048] Figure 6 The working surface of the vertical mill roller made of ZTA particles prepared in Example 1 and high chromium cast iron by a casting method is shown. Figure 6It shows that after the ZTA particles prepared by surface crystallization treatment have been working with the vertical mill roller prepared by high chromium cast iron by casting for a period of time, the network prepared by ZTA particles will protrude from the surface of the cast iron matrix due to its good wear resistance. The ZTA particles that constitute the network body are well bonded to the high chromium cast iron matrix, and no abnormal shedding phenomenon is observed. DETAILED DESCRIPTION

[0049] The present invention provides a surface crystallization treatment method for ZTA ceramic particles, which comprises the following steps:

[0050] (1) Surface pretreatment of ZTA ceramic particles

[0051] Immerse certain ZTA ceramic particles of 12-16 mesh in anhydrous ethanol and perform ultrasonic cleaning at a frequency of 2000-4000 Hz for 20-40 minutes. Remove the ZTA ceramic particles and rinse with water until neutral. After drying in an oven at 60-80°C, seal the bag and store it to complete the surface cleaning of the ZTA particles.

[0052] (2) Preparation of crystallization agent on the surface of ZTA ceramic particles

[0053] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0054]

[0055] Pour the weighed raw materials into a V-type mixer, mix at a speed of 80-150 r / min for 30-60 minutes, and then pass through a 40# sieve to obtain smelting raw materials.

[0056] Heat the quartz crucible furnace to 1200-1250°C at a rate of 3-6°C / min, plug the blocking rod, and pour in the mixed molten raw materials. When the volume of the raw materials reaches 3 / 4 of the volume of the quartz crucible, stop adding the materials. When the furnace temperature rises to 1200°C again, keep it warm for 2-3 hours. Place a refractory steel trough at the discharge port, lift the blocking rod, and let the molten glass material flow into the refractory steel trough for air cooling. Collect the air-cooled glass material fragments and pour them into a corundum ball mill with a diameter of 400mm. Zirconia grinding balls and anhydrous ethanol are added in a ratio of 1.2:1:1 to the mass ratio of balls, glass material, and anhydrous ethanol. The mass of the zirconia grinding balls with a diameter of 30mm accounts for 50%, and the mass of the grinding balls with a diameter of 10mm accounts for 50%. The rotation speed of the ball mill is 300-360r / min. After ball milling the raw materials for 4-6 hours, the ball-milled slurry is passed through a 100# sieve and dried at 60-70°C to obtain glass powder with a surface crystallization agent for use.

[0057] (3) Crystallization treatment of ZTA ceramic particles

[0058] Weigh a certain amount of ZTA particles treated in step (1), then add 4-6% of the weight of the ZTA particles to the liquid phenolic resin, and stir evenly with a spiral stirrer at a speed of 60-100 rpm for 0.5-1 hour. Coat the surface of the ZTA particles with the liquid phenolic resin, then add 6-8% of the weight of the ZTA particles to the surface of the glass powder obtained in step 2, and stir evenly with a spiral stirrer at a speed of 60-100 rpm for 0.5-1 hour. Spread the ZTA particles with the glass powder adhered to the surface on a graphite plate, keep it at 80-120 degrees for 6-10 hours, then spread the ZTA particles on a refractory material plate with BN powder on the surface, place it in a box furnace, and heat it to 850-900°C at a heating rate of 3-6°C / min. After keeping it at this temperature for 3-6 hours, cool it in the furnace, and remove the ZTA ceramic particles after surface crystallization treatment.

[0059] (4) Surface cleaning of ZTA ceramic particles after crystallization treatment

[0060] The surface-crystallized ZTA ceramic particles are immersed in hot water at 80-90°C, with the mass of the ZTA ceramic particles being less than 20% of the mass of the hot water. After soaking for 12-24 hours, the ZTA ceramic particles are removed and immersed in a NaOH solution with a pH of 12-13 for 1-2 hours. The ZTA particles are then rinsed with deionized water until neutral. The particles are then ultrasonically cleaned in deionized water at a frequency of 2000-4000 Hz for 1-2 hours at room temperature. The ZTA particles are removed and dried to obtain ZTA particles with a large amount of spessartine [Mn3Al2(SiO4)3] crystals precipitated on their surfaces.

[0061] The present invention will be further explained below:

[0062] (1) Surface cleaning of ZTA ceramic particles

[0063] ZTA ceramic particles of a certain size are immersed in anhydrous ethanol, and the surface of the ZTA particles is cleaned under ultrasonic conditions to prepare for coating the surface of the ZTA particles with a crystallization agent in the subsequent process.

[0064] (2) Preparation of crystallization agent on the surface of ZTA ceramic particles

[0065] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0066]

[0067] The main components of boron glass are SiO2, B2O3 and Na2O, which constitute the main network structure of the glass crystallizer. After the glass crystallizer is melted, ammonium dihydrogen phosphate enters the glass crystallizer in the form of P2O5. P2O5 enters the glass network structure in a layered structure, which can further reduce the bridging oxygen content of the glass crystallizer and reduce the chemical stability of the glass crystallizer. At the same time, P 5+ It has a large number of charges and has a strong polarizing effect on the surrounding anions. Under certain conditions, it can promote the crystallization of the glass crystallizer. The addition of sodium carbonate introduces more Na2O into the glass crystallizer. In the molten glass crystallizer, it can provide free oxygen to the aluminum oxide octahedron on the surface of ZTA, turning it into aluminum oxide tetrahedron and entering the molten glass crystallizer. Manganese dioxide exists in the glass crystallizer in the form of manganese oxide tetrahedron and manganese oxide octahedron, which provides a manganese source for the subsequent precipitation of Mn3Al2(SiO4)3 crystals. The addition of calcium fluoride will introduce F into the glass crystallizer. - and Ca 2+ . Among them F - The introduction of crystallization agent in molten glass will replace the O in the glass network structure in some areas. 2- , destroying the integrity of the glass network structure, reducing the surface tension of the molten glass crystallizer so that it can better wet the ZTA particles, and at the same time reducing the chemical stability of the glass crystallizer so that it can disintegrate and fall off from the surface of the ZTA particles in the subsequent hot water immersion process.

[0068] The raw materials of the glass crystallizer are mixed evenly in a V-type mixer, smelted in a crucible furnace at 1200°C, and air-cooled to obtain glass crystallizer fragments, which are then ball-milled, sieved, and dried to obtain glass crystallizer powder that meets the particle size requirements.

[0069] (3) Crystallization treatment of ZTA ceramic particles

[0070] Weigh a certain amount of surface-cleaned ZTA particles and add 4-6% liquid phenolic resin by weight of the ZTA particles. Mix thoroughly with a spiral stirrer to coat the ZTA particles with the liquid phenolic resin. Then, add 6-8% glass powder as a crystallizer by weight of the ZTA particles and continue mixing until the crystallizer adheres to the ZTA particles. The ZTA particles, with the glass powder attached to their surfaces, are spread evenly on a graphite plate. After being heated at 80-120°C for 6-10 hours, the phenolic resin solidifies, firmly bonding the crystallizer to the ZTA particles. The ZTA particles are then spread evenly on a refractory plate padded with BN powder to prevent the heat-treated ZTA particles from sticking to the plate. The ZTA particles are then placed in a box furnace and heated at a rate of 3-6°C / min to 850-900°C. When the temperature exceeds 700°C, the crystallizer on the ZTA particles becomes a viscous fluid and coats the surface. When kept at 850-900℃, the viscosity of the crystallizer glass viscous fluid is low and the chemical activity is high. There is a large amount of Na2O in the crystallizer, which provides free oxygen to the aluminum oxide octahedron on the surface of the ZTA particles, transforming it into aluminum oxide tetrahedron and melting it into the crystallizer. After a period of holding, the aluminum oxide on the surface of the ZTA particles continues to melt into the crystallizer. The aluminum oxide concentration in the crystallizer at the interface between the ZTA particles and the molten crystallizer continues to increase. There is a certain amount of P in the crystallizer. 5+ Because it carries a large number of positive charges, it has a strong aggregation effect on the surrounding anions, which will promote the crystallization of the crystallizer. Because the concentration of alumina is high at the interface between ZTA particles and the molten crystallizer, the surface of ZTA particles can provide non-uniform nucleation sites for the crystallization of the molten crystallizer, reducing the nucleation energy. Therefore, Mn3Al2(SiO4)3 crystals begin to precipitate on the surface of ZTA particles, and the crystals begin to grow as the holding time increases.

[0071] (4) Surface cleaning of ZTA ceramic particles

[0072] The ZTA ceramic particles after surface crystallization treatment are immersed in hot water at 80-90℃. The residual crystallization agent glass on the surface contains a large amount of Na2O and a certain amount of F - The network integrity of the crystallizer glass is poor, as is the layered P2O5 structure. The Na+ ions in the crystallizer glass are easily precipitated in hot water, causing the entire network structure to collapse. The residual crystallizer glass falls off the ZTA surface, while the Mn3Al2(SiO4)3 crystals, which have excellent water resistance, remain on the ZTA particle surface. The boiled ZTA particles are then immersed in a NaOH solution with a pH of 12-13 to further clean any remaining crystallizer glass from the surface. Finally, ZTA particles with a large amount of Mn3Al2(SiO4)3 crystals precipitated on the surface are obtained.

[0073] After treatment with the method provided by the present invention, a large amount of spessartine crystals precipitate from the originally smooth surface of ZTA particles. Because spessartine crystals contain a certain amount of the element Mn (the atomic radius of Mn is 117 pm, while the atomic radius of Fe is 124 pm), which is very close, they easily form a substitutional solid solution. Therefore, the spessartine crystals on the surface of the ZTA particles promote the formation of a good wetting interface between the iron matrix and the ZTA particles. When ZTA particles prepared using surface crystallization treatment are used in a vertical mill roller made by casting high-chromium cast iron (wherein the ZTA particles have a particle size of 12-16 mesh, a volume content of 33%, and a casting temperature of 1350°C), their service life when crushing cement clinker is increased by over 40% compared to a ZTA / Fe-based composite roller made using conventional ZTA particles under the same conditions.

[0074] The present invention will be further described below with reference to specific embodiments.

[0075] The boron glass used in the present invention is common borosilicate glass powder available on the market, and its composition (by mass percentage) is: SiO2 70%-80%, B2O3 10%-15%, Na2O 4%-10%, Al2O3 0-5%.

[0076] Example 1

[0077] This embodiment provides a ZTA ceramic particle surface crystallization treatment process with the following specific steps:

[0078] (1) Surface pretreatment of ZTA ceramic particles

[0079] Immerse certain 12-mesh ZTA ceramic particles in anhydrous ethanol and ultrasonically clean them at a frequency of 4000 Hz for 40 minutes. Remove the ZTA ceramic particles and rinse them with water until they are neutral. After drying them in an oven at 80°C, seal them in a bag and store them, thereby completing the surface cleaning of the ZTA particles.

[0080] (2) Preparation of crystallization agent on the surface of ZTA ceramic particles

[0081] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0082]

[0083]

[0084] Pour the weighed raw materials into a V-type mixer, mix them at a speed of 80 r / min for 60 minutes, and then pass them through a 40# sieve to obtain smelting raw materials.

[0085] The quartz crucible furnace was heated to 1250°C at a rate of 5°C / min. A blocking rod was installed, and the mixed molten raw materials were poured in. When the raw material volume reached 3 / 4 of the quartz crucible volume, the addition of raw materials was stopped. When the furnace temperature was raised to 1200°C again, it was held at this temperature for 3 hours. A refractory steel trough was placed at the discharge port. The blocking rod was raised to allow the molten glass material to flow into the refractory steel trough and air-cooled. The air-cooled glass frit fragments were collected and poured into a corundum ball mill with a diameter of 400 mm. Zirconia grinding balls and anhydrous ethanol were added in a mass ratio of 1.2:1:1 of balls, glass frit, and anhydrous ethanol. The zirconia grinding balls accounted for 50% by mass, with 30 mm diameter balls accounting for 50% by mass, and 10 mm diameter balls accounting for 50% by mass. The ball mill was rotated at 360 r / min. After ball milling for 6 hours, the milled slurry was passed through a 100# mesh and dried at 70°C to obtain a glass powder with a surface crystallization agent for later use.

[0086] (3) Surface crystallization treatment of ZTA ceramic particles

[0087] Weigh a certain amount of ZTA particles treated in step (1), then add 4% of the weight of the ZTA particles to the liquid phenolic resin, and stir evenly with a spiral stirrer at a speed of 60 rpm for 1 hour. Coat the surface of the ZTA particles with liquid phenolic resin, then add 6% of the weight of the ZTA particles to the surface of the glass powder obtained in step 2, and stir evenly with a spiral stirrer at a speed of 60 rpm for 1 hour. Spread the ZTA particles with the glass powder adhered to the surface on a graphite plate, keep it at 120°C for 6 hours, then spread the ZTA particles on a refractory material plate with BN powder on the surface, place it in a box furnace, and heat it to 900°C at a heating rate of 6°C / min. Keep it at this temperature for 5 hours, then cool it in the furnace, and remove the ZTA ceramic particles after surface crystallization treatment.

[0088] (4) Surface cleaning of ZTA ceramic particles after crystallization treatment

[0089] The surface-crystallized ZTA ceramic particles were immersed in 90°C hot water, with the mass of the ZTA ceramic particles being less than 20% of the mass of the hot water. After soaking for 24 hours, the ZTA ceramic particles were removed and immersed in a NaOH solution with a pH of 12 for one hour. The ZTA particles were then removed and rinsed with deionized water until neutral. The particles were then ultrasonically cleaned in deionized water at 4000 Hz for 0.5 hours at room temperature. The ZTA particles were removed and dried to obtain ZTA particles with a large amount of spessartine Mn3Al2(SiO4)3 crystals precipitated on their surfaces.

[0090] Example 2

[0091] This embodiment provides a ZTA ceramic particle surface crystallization treatment process with the following specific steps:

[0092] (1) Surface pretreatment of ZTA ceramic particles

[0093] Immerse certain 16-mesh ZTA ceramic particles in anhydrous ethanol and ultrasonically clean them at a frequency of 2000 Hz for 20 minutes. Remove the ZTA ceramic particles and rinse them with water until they are neutral. After drying them in an oven at 80°C, seal them in a bag and store them, thereby completing the surface cleaning of the ZTA particles.

[0094] (2) Preparation of crystallization agent on the surface of ZTA ceramic particles

[0095] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0096]

[0097]

[0098] Pour the weighed raw materials into a V-type mixer, mix at a speed of 150 r / min for 30 minutes, and then pass through a 40# sieve to obtain smelting raw materials.

[0099] The quartz crucible furnace was heated to 1250°C at a rate of 3°C / min. A blocking rod was installed, and the mixed molten raw materials were poured in. When the raw material volume reached 3 / 4 of the quartz crucible volume, the addition of raw materials was stopped. When the furnace temperature was raised to 1200°C again, it was held at this temperature for 2 hours. A refractory steel trough was placed at the discharge port. The blocking rod was raised to allow the molten glass material to flow into the refractory steel trough and air-cooled. The air-cooled glass frit fragments were collected and poured into a corundum ball mill with a diameter of 400 mm. Zirconia grinding balls and anhydrous ethanol were added in a mass ratio of 1.2:1:1 of balls, glass frit, and anhydrous ethanol. The zirconia grinding balls accounted for 50% by mass, with 30 mm diameter balls accounting for 50% by mass, and 10 mm diameter balls accounting for 50% by mass. The ball mill was rotated at 300 r / min. After ball milling the raw materials for 4 hours, the milled slurry was passed through a 100# mesh screen and dried at 70°C to obtain a glass powder with a surface crystallization agent for later use.

[0100] (3) Surface crystallization treatment of ZTA ceramic particles

[0101] Weigh a certain amount of ZTA particles treated in step (1), then add 6% of the weight of the ZTA particles to the liquid phenolic resin, and stir evenly with a spiral stirrer at a speed of 100 rpm for 1 hour. Coat the surface of the ZTA particles with liquid phenolic resin, then add 6% of the weight of the ZTA particles to the surface of the glass powder obtained in step 2, and stir evenly with a spiral stirrer at a speed of 60 rpm for 1 hour. Spread the ZTA particles with the glass powder adhered to the surface on a graphite plate, keep it at 80 degrees for 10 hours, then spread the ZTA particles on a refractory material plate with BN powder on the surface, place it in a box furnace, and heat it to 850°C at a heating rate of 6°C / min. Keep it at this temperature for 5 hours, then cool it in the furnace, and remove the ZTA ceramic particles after surface crystallization treatment.

[0102] (4) Surface cleaning of ZTA ceramic particles after crystallization treatment

[0103] The surface-crystallized ZTA ceramic particles were immersed in 90°C hot water, with the mass of the ZTA ceramic particles being less than 20% of the mass of the hot water. After soaking for 24 hours, the ZTA ceramic particles were removed and immersed in a NaOH solution with a pH of 13 for one hour. The ZTA particles were then removed and rinsed with deionized water until neutral. The particles were then ultrasonically cleaned in deionized water at room temperature at a frequency of 2000 Hz for one hour. The ZTA particles were removed and dried to obtain ZTA particles with a large amount of spessartine Mn3Al2(SiO4)3 crystals precipitated on their surfaces.

[0104] Example 3

[0105] The difference from Example 1 is

[0106] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0107]

[0108] Example 4

[0109] The difference from Example 1 is

[0110] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0111]

[0112]

[0113] Example 5

[0114] The difference from Example 1 is

[0115] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0116] Example 6

[0117] The difference from Example 1 is

[0118] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0119] Comparative Example 1

[0120] The difference from Example 1 is

[0121] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0122]

[0123] After the glass crystallizer is smelted, ammonium dihydrogen phosphate enters the glass crystallizer in the form of P2O5. P2O5 enters the glass network structure in a layered structure, which can further reduce the bridging oxygen content of the glass crystallizer and reduce the chemical stability of the glass crystallizer. At the same time, P 5+ It has a large number of charges and has a strong polarizing effect on the surrounding anions. Under certain conditions, it can promote the crystallization of glass crystallization agents. Without the addition of ammonium dihydrogen phosphate crystallization agent, spessartine crystals cannot be precipitated during the heat treatment process.

[0124] Comparative Example 2

[0125] The difference from Example 1 is

[0126] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0127]

[0128] The addition of sodium carbonate introduces more Na2O into the glass crystallizer. In the molten glass crystallizer, this free oxygen can be supplied to the aluminum oxide octahedra on the ZTA surface, converting them into aluminum oxide tetrahedra. This oxygen then enters the molten glass crystallizer, creating a high Al2O3 content at the interface between the ZTA surface and the molten glass crystallizer, thereby promoting the precipitation of spessartine crystals at this interface. Without the addition of sodium carbonate, spessartine crystals cannot be precipitated.

[0129] Comparative Example 3

[0130] The difference from Example 1 is

[0131] The raw material formula (mass percentage wt%) of the ZTA ceramic particle surface crystallization agent is:

[0132]

[0133] The addition of calcium fluoride will introduce F into the glass crystallization agent. - In some areas of the molten glass crystallizer, the O in the glass network structure will be replaced. 2- , destroying the integrity of the glass network structure and reducing the chemical stability of the glass crystallizer, so that the glass crystallizer can disintegrate and fall off from the surface of the ZTA particles in the subsequent hot water immersion process. Without adding calcium fluoride, the glass crystallizer cannot disintegrate and fall off from the surface of the ZTA particles in the subsequent hot water immersion process.

[0134] Application Examples

[0135] The ZTA particles prepared in Examples 1-5 were used, and water glass was used as a binder to prepare a porous ZTA particle preform (ZTA particle volume content was 33%) by mold dry pressing. The porous preform was fixed in the sand mold of the vertical mill grinding roller, and the sand mold was cast at 1350°C using Cr26 high chromium casting. After cooling, a ZTA / Fe-based composite grinding roller was obtained.

[0136] The method for evaluating the wear resistance of ZTA / Fe-based composite grinding roller is as follows:

[0137] The ZTA / Fe-based composite grinding roller was installed on an LM10 vertical mill to crush cement clinker. The feed particle size was less than 70 mm and the discharge particle size was 325 mesh. After six months of stable operation, the wear thickness of the working layer of the composite grinding roller was measured.

[0138] The wear thickness of the working layer of the ZTA / Fe-based composite grinding roller prepared with surface-crystallized ZTA particles was designated L1; the wear thickness of the working layer of the ZTA / Fe-based composite grinding roller prepared with conventional ZTA particles was designated L2. The table below shows the wear resistance data for ZTA / Fe-based composite grinding rollers prepared with the ZTA particles prepared in Examples 1-5.

[0139] L1 L2 L1 / L2 Example 1 7.8mm 15.4mm 0.51 Example 2 8.2mm 15.4mm 0.53 Example 3 8.1mm 15.4mm 0.53 Example 4 7.9mm 15.4mm 0.51 Example 5 8.1mm 15.4mm 0.53

[0140] As can be seen from the above table, the wear resistance of the ZTA / Fe-based composite grinding roller prepared by surface crystallization treated ZTA particles is improved by more than 40% compared with the ZTA / Fe-based composite grinding roller prepared by ordinary ZTA particles.

Claims

1. A method for precipitating spessartine crystals on the surface of ZTA particles, characterized in that: The steps include: After melting the crystallization agent, rapidly cooling it and then ball milling it to obtain glass powder; Coating the glass powder on the surface of ZTA particles; Heating the ZTA particles coated with the glass powder to 850-900° C. and maintaining the temperature to precipitate spessartine crystals on the surface of the ZTA particles; The crystallizing agent comprises 60-65 wt % of boron glass powder, 10-15 wt % of ammonium dihydrogen phosphate, 10-15 wt % of sodium carbonate, 8-12 wt % of manganese dioxide and 5-8 wt % of calcium fluoride.

2. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: The particle size of the ZTA particles is 12-16 mesh; The melting temperature rise rate is 3-6°C / min; The melting temperature is 1200-1250°C; The holding time of the melting is 2-3 hours.

3. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: The rapid cooling includes air cooling; The step of heating the ZTA particles coated with the glass powder to 850-900° C. and keeping the temperature therein comprises heating the ZTA particles coated with the glass powder to 850-900° C. at a heating rate of 3-6° C. / min and keeping the temperature therein for 3-6 hours.

4. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: The ball-to-material ratio of the ball mill is 1.2:1; The ball milling medium includes ethanol; The ratio of the ball mill medium to the grinding balls is 1:1.2; The ball milling speed is 300-360 r / min; The ball milling time is 4-6 hours.

5. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: The coating comprises the steps of mixing the ZTA particles and the coating agent under stirring, adding the glass powder and then solidifying the mixture to coat the surface of the ZTA particles with the glass powder.

6. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 5, wherein: The coating agent includes phenolic resin; The amount of the coating agent added is 4-6 wt% of the ZTA particles; The stirring speed is 60-100 r / min; The stirring time is 0.5-1h; The curing time is 6-10h; The curing temperature is 80-120°C.

7. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: A pre-cleaning step is also included.

8. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 7, wherein: The pre-cleaning comprises the steps of soaking the ZTA ceramic particles in an organic solvent, cleaning them under ultrasonic conditions, rinsing the ZTA ceramic particles with water until they are neutral, and drying them; The organic solvent includes ethanol; The frequency of the ultrasound is 2000-4000 Hz; The ultrasound time is 20-40 minutes; The drying temperature is 60-80°C.

9. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 1, wherein: A post-cleaning step is also included.

10. The method for precipitating spessartine crystals on the surface of ZTA particles according to claim 9, wherein: The post-cleaning step comprises soaking the ZTA particles with spessartine crystals precipitated on the surface in water at 80-90° C. for 12-24 hours, then soaking them in an alkaline solution with a pH value of 12-13, then rinsing them with water until neutral, and then ultrasonically cleaning them; The mass of the ZTA particles is less than 20% of the mass of water at 80-90°C; The soaking time is 1-2 hours; The frequency of the ultrasonic cleaning is 2000-4000 Hz; The ultrasonic cleaning time is 1-2 hours.

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