Preparation method of centrifugally cast bimetallic ceramic composite grinding roller and centrifugal casting device

Abstract

The invention discloses a preparation method and a centrifugal casting device for a centrifugal casting bimetallic ceramic composite grinding roller. The ceramic particles, ceramic powder and a binder are uniformly mixed to obtain a ceramic particle mixture, and the mixture is filled into a prefabricated lost foam to obtain a honeycomb ceramic particle preform; a layer of resin molding sand is molded on the inner wall of a metal mold to form a centrifugal casting device; the ceramic particle preform is assembled on the inner wall of the molding sand of the metal mold; the metal mold is fixed on a centrifuge and the centrifuge is turned on, and a working layer of highly wear-resistant metal liquid and a matrix metal liquid are successively poured to form a bimetallic ceramic composite grinding roller blank; the prepared blank is taken out and cleaned, cooled to room temperature after quenching treatment, cooled to room temperature again after tempering treatment, and finally machined to obtain a finished bimetallic ceramic composite grinding roller. The invention solves the problems of easy shedding, short life, and easy cracking during heat treatment and use of ceramic particles in traditional composite processes.

Description

Technical Field

[0001] The invention relates to the technical field of composite material grinding roller preparation, in particular to a preparation method of a centrifugally cast bimetallic ceramic composite grinding roller and a centrifugal casting device. Background Art

[0002] Ceramic particle reinforced metal matrix composite grinding rollers are widely used in thermal power, cement, steel, mining and other fields. Their service life is more than twice that of traditional grinding rollers. In the later period of use, the grinding efficiency can also be maintained at a high level. Ceramic particle reinforced metal matrix composite materials are composite materials made of ceramic particles reinforced with high chromium cast iron or high manganese steel matrix. They have the advantages of high hardness and high wear resistance of ceramic particles and toughness of metal matrix.

[0003] The preparation methods of ceramic particle reinforced metal matrix composite grinding rollers mainly include traditional gravity casting, negative pressure casting and other methods. In the composite grinding rollers prepared by this casting method, the ceramic particles are not firmly bonded to the metal matrix, and the ceramic particles are easy to fall off during the grinding process of the grinding roller, which greatly reduces the service life. After analysis, the main reason is that the high-temperature metal liquid infiltration power is insufficient, resulting in the local metal liquid of the composite material unable to fill the gap between the metal ceramic particles, reducing the bonding strength between the metal and ceramic particles, and affecting the overall wear resistance of the ceramic particle reinforced metal matrix composite grinding roller. In addition, the production of ceramic particle reinforced metal matrix composite grinding rollers mainly adopts an integral casting process, that is, the composite grinding roller matrix is ​​prepared by pouring a high wear-resistant metal liquid into a ceramic particle preform. The high wear-resistant metal liquid is generally made of high-chromium cast iron or high-manganese steel material, and the hardness reaches more than 60HRC after heat treatment. It is easy to break during heat treatment and use. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a method for preparing a centrifugally cast bimetallic ceramic composite grinding roller and a centrifugal casting device to solve the problems of easy shedding of ceramic particles, short life, and easy cracking during heat treatment and use in traditional composite processes.

[0005] Technical solution: To achieve the above purpose, a preparation method and centrifugal casting device of a centrifugal casting bimetallic ceramic composite grinding roller of the present invention comprises the following steps:

[0006] S1, uniformly mixing ceramic particles, ceramic powder and a binder in a certain mass ratio to obtain a ceramic particle mixture;

[0007] S2, filling the ceramic particle mixture into a prefabricated lost foam, and placing it in a drying room for drying, to obtain a honeycomb-shaped ceramic particle preform;

[0008] S3, forming a layer of resin sand on the inner wall of the metal mold, brushing a layer of high temperature resistant paint on the inner wall of the resin sand and the surface of the end cover, and then heating the sand with a dryer for a period of time to form a centrifugal casting device;

[0009] S4, assembling and fixing the ceramic particle preforms in S2 in sequence on the inner wall of the molding sand of the metal mold in S3;

[0010] S5, fix the metal mold in S4 on the centrifuge, dry the molding sand again with a dryer for a period of time, then start the centrifuge, first pour the working layer high wear-resistant metal liquid, continue centrifugation for 30-60s after pouring, then pour the base metal liquid, continue centrifugation until the poured bimetallic solution is completely solidified, and make a bimetallic ceramic composite grinding roller blank;

[0011] S6, taking out and cleaning the bimetallic ceramic composite grinding roller blank, cooling it to room temperature after quenching treatment, cooling it to room temperature again after tempering treatment, and finally machining it to obtain a finished bimetallic ceramic composite grinding roller.

[0012] Furthermore, in step S1, the ceramic particles are a mixture of one or more of Al2O3, ZrO2, TiC, WC, and Si3N4; the ceramic powder is one or more of boron carbide, titanium oxide, and sodium borate, and the added mass of the ceramic powder is 0.5%-2% of the ceramic particles; the binder is an inorganic binder, and the added mass of the binder is 4%-8% of the ceramic particles.

[0013] Furthermore, the resin molding sand is alkaline phenolic resin sand; in steps S3-S4, the molding sand is heated for 0.5-1h before and after assembling the ceramic particle preform to the inner wall surface of the molding sand, and the temperature of the drying machine is set to 200-300°C.

[0014] Furthermore, the honeycomb holes of the ceramic particle preform are conical through holes, and in step S4, the small hole ends thereof are placed against the molding sand for assembly.

[0015] Furthermore, in step S5, the high wear-resistant molten metal is one of BTMCr20, BTMCr26, and ZGMn13, and its pouring amount is 1 / 2-2 / 3 of the mass of the grinding roller; the matrix molten metal is ductile iron or low carbon steel, and its pouring amount is 1 / 3-1 / 2 of the mass of the grinding roller.

[0016] Furthermore, in step S6, the bimetallic ceramic composite grinding roller blank is first subjected to quenching treatment at 960-1020°C for 4-8 hours, with a heating rate not exceeding 30-60°C / h. After being taken out of the furnace, it is air-cooled to room temperature, and then placed in 150-200°C for tempering treatment at 4-8 hours, and then air-cooled to room temperature.

[0017] Furthermore, it includes the metal mold, which is a cylindrical structure, and the upper and lower ports of the metal mold are respectively provided with end covers, the center of the upper end cover is provided with a pouring port, and the center of the lower end cover is connected to the rotating shaft of the centrifuge, the inner wall of the metal mold is provided with a molding sand layer, the inner wall of the molding sand layer is assembled with the ceramic particle preform, the inner wall of the ceramic particle preform is formed with a high wear-resistant metal layer, and the inner wall of the high wear-resistant metal layer is formed with a base metal layer; a plurality of air outlet holes are provided on the molding sand layer and the ring wall of the metal mold from the inside to the outside.

[0018] Beneficial effects: The preparation method of a centrifugally cast bimetallic ceramic composite grinding roller and the centrifugal casting device of the present invention have at least the following advantages:

[0019] (1) Centrifugal casting is adopted. Under the action of centrifugal force, the penetration power of molten metal into the gap between ceramic particles is greater, which improves the bonding strength between metal and ceramic particles. The ceramic particles are not easy to fall off during the operation of the ceramic composite grinding roller, thus extending its service life.

[0020] (2) The use of a honeycomb-shaped ceramic particle preform in combination with a centrifugal device is more conducive to the bonding of metal and ceramic, allowing the metal to fully react with the ceramic powder and ceramic particles to form a reaction interface bond, thereby improving the bonding strength between the metal matrix and the ceramic particle preform.

[0021] (3) Layer-by-layer casting and the use of metal with good plasticity and toughness as the grinding roller base layer can effectively prevent the cracking problem caused by thermal stress during heat treatment and use of high-wear-resistant metal materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 A schematic structural diagram of a centrifugal casting device according to an embodiment of the present invention;

[0023] Attached Figure 2 This is a schematic structural diagram of a ceramic particle preform according to an embodiment of the present invention;

[0024] Attached Figure 3 A schematic diagram of a radial cross-sectional structure of a honeycomb hole of a ceramic particle preform according to an embodiment of the present invention;

[0025] Attached Figure 4 This is a schematic structural diagram of a bimetallic ceramic composite grinding roller according to an embodiment of the present invention;

[0026] Attached Figure 5 This is a schematic diagram of the splicing structure of two adjacent ceramic particle preforms according to an embodiment of the present invention;

[0027] Attached Figure 6 For attachment Figure 5 Schematic diagram of the structural cross-section at point A in the middle. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] As attached Figure 1-6 The preparation method of a centrifugally cast bimetallic ceramic composite grinding roller and the centrifugal casting device include the following steps:

[0030] S1. After uniformly mixing 6-12 mesh ceramic particles, ceramic powder and a binder in a certain mass ratio, a ceramic particle mixture is obtained; wherein the ceramic particles are a mixture of one or more of Al2O3, ZrO2, TiC, WC, Si3N4; the ceramic powder is one or more of boron carbide, titanium oxide, and sodium borate, and the added mass of the ceramic powder is 0.5%-2% of the ceramic particles; the binder is an inorganic binder such as water glass, silica sol, aluminum sol, etc., and the added mass of the binder is 4%-8% of the ceramic particles.

[0031] S2. Fill the prefabricated honeycomb lost mold with the ceramic particle mixture, wherein the lost mold is made of polystyrene; insert a screw into the middle of the ceramic particle mixture to reserve a certain number of mounting holes, and then place the entire mold in a drying oven at 60-100° C. for 48-72 hours to obtain a honeycomb ceramic particle preform 1; wherein the number of mounting holes is 4-8, and the hole diameter is set to 2-4 mm.

[0032] S3, forming a layer of resin sand on the inner wall of the metal mold 2, brushing a layer of high temperature resistant coating on the inner wall of the resin sand and the surface of the end cover, and then using a dryer to heat the sand for 0.5-1h to form a centrifugal casting device, the temperature of the dryer is set to 200-300°C; wherein, the molding thickness of the resin sand is 15-30mm, the resin sand is alkaline phenolic resin sand; the high temperature resistant coating is zircon powder coating; the metal mold is a half mold.

[0033] S4, assemble and fix the ceramic particle preforms 1 in S2 on the inner wall of the molding sand of the metal mold 2 in S3 in sequence, and fix them in the resin molding sand with screws, and the screws cooperate with the reserved mounting holes; the honeycomb holes 11 of the ceramic particle preforms 1 are conical through holes. When assembling, the small hole end is close to the molding sand for assembly, and the large hole end faces inward. The highly wear-resistant metal liquid is more conducive to infiltrating into the ceramic particle preform under the action of centrifugal force, so that the metal reacts fully with the ceramic powder and ceramic particles to form a reaction interface, thereby improving the bonding strength between the metal matrix and the ceramic particle preform. The service life of the composite grinding roller is 2-4 times that of the traditional high chromium cast iron or surfacing grinding roller material; the layout gap between adjacent ceramic particle preforms 1 is 3-5mm.

[0034] S5, fix the metal mold 2 in S4 on the centrifuge, dry the molding sand again with a dryer for 0.5-1h, then turn on the centrifuge, the speed of the centrifuge is 400-1000r / min; first pour the working layer of high wear-resistant metal liquid, continue centrifugation for 30-60s after pouring, then pour the matrix metal liquid, continue centrifugation until the poured bimetallic solution is completely solidified, and make a bimetallic ceramic composite grinding roller blank; wherein the high wear-resistant metal liquid is one of BTMCr20, BTMCr26, and ZGMn13, and its pouring amount is 1 / 2-2 / 3 of the mass of the grinding roller; the matrix metal liquid is ductile iron or low carbon steel, and the pouring amount is 1 / 3-1 / 2 of the mass of the grinding roller. Due to the good plasticity of ductile iron and low carbon steel, the cracking problem caused by thermal stress during heat treatment and use of high wear-resistant metal materials can be effectively prevented.

[0035] S6. Take out and clean the bimetallic ceramic composite grinding roller blank, first carry out quenching treatment at 960-1020℃ for 4-8h, the heating rate shall not exceed 30-60℃ / h, after being taken out of the furnace, air-cool it to room temperature, then put it in 150-200℃ for 4-8h for tempering treatment, and then air-cool it to room temperature; finally, after machining treatment, a bimetallic ceramic composite grinding roller with a working layer hardness of 60-63HRC is obtained. Among them, the air cooling after quenching adopts a rotating air cooling device platform, and the speed of the air cooling device platform is set to 100-200r / min, which can make the cooling more uniform, which is conducive to eliminating thermal stress, and the metallographic structure is more uniform, which is conducive to reducing the cracking tendency.

[0036] As attached Figure 1 As shown in the figure, the centrifugal casting device includes the metal mold 2, which is a cylindrical structure. The upper and lower ports of the metal mold 2 are respectively provided with end covers 3, the center of the upper end cover 3 is provided with a pouring port 4, and the center of the lower end cover 3 is connected to the rotating shaft 5 of the centrifuge. The inner wall of the metal mold 2 is provided with a molding sand layer 6, which is convenient for positioning the honeycomb grid preform and convenient for sand removal, so that the bimetallic ceramic composite grinding roller is easy to demold.

[0037] The inner wall of the molding sand layer 6 is assembled with the ceramic particle preform 1, the inner wall of the ceramic particle preform 1 is formed with a high wear-resistant metal layer 7, and the inner wall of the high wear-resistant metal layer 7 is formed with a base metal layer 8; the molding sand layer 6 and the annular wall of the metal mold 2 are provided with a plurality of vent holes 9 from inside to outside; the size of the vent holes is 3-5mm, which is convenient for the discharge of gas during the casting process of the molding sand.

[0038] As attached Figure 3As shown in , the small-diameter port 12 of the honeycomb hole 11 is expanded, and the small-diameter ports of adjacent honeycomb holes are connected through the guide groove 13. On the basis of the ceramic particle preform formed in step S2, the small-diameter port of each honeycomb hole can be chamfered and grooved on the outer arc surface. In centrifugal casting, the centrifugal force causes the molten metal to fill the honeycomb hole and the guide groove, so that the high-wear-resistant metal layer forms an embedded mesh metal structure on the outer arc surface of the ceramic particle preform, so that the combination between the high-wear-resistant metal layer and the ceramic layer is not only the reaction interface combination between the bonding surfaces, but also forms a constraint on the macroscopic three-dimensional structure, so that the ceramic and the metal are firmly connected and not easy to fall off; as shown in the attached Figure 5 As shown in the figure, the joint surfaces of two adjacent ceramic particle preforms are provided with interlaced interlocking structures, and the interlocking structures of the two adjacent ceramic particle preforms are adapted and buckled; and under the centrifugal effect, the metal liquid entering the matching gap forms a continuous winding metal edge, which effectively restricts the relative slippage of the ceramic structure layer relative to the metal layer; as shown in the figure Figure 6 As shown in the figure, a V-shaped structural groove is provided on the inner side of the joint seam of two adjacent ceramic particle preforms, which is used to make the root of the formed metal edge a support structure with a conical cross-section, and is used to guide the external force to be applied to the internal metal matrix layer, thereby reducing the interaction force between adjacent ceramic preforms and avoiding the phenomenon of stress extrusion causing cracking of the working layer; and the outer metal mesh structure cooperates with the inner metal edge structure to constrain the ceramic particle preform; further ensuring the structural stability of the bimetallic ceramic composite grinding roller to obtain a longer service life.

[0039] The overall solution adopts the centrifugal casting preparation method. Compared with the traditional gravity casting, the centrifugal force makes the metal liquid penetrate into the gaps between the ceramic particles with greater infiltration power, which is conducive to the metal liquid filling the gaps between the ceramic particles, improving the bonding strength between the metal and the ceramic particles. The ceramic particles are not easy to fall off during the operation of the ceramic composite grinding roller, thus extending its service life. The bimetallic ceramic composite preparation method is adopted, and the working layer material is a highly wear-resistant metal to ensure its wear resistance. The core base metal is made of ductile iron or low-carbon steel to ensure the plastic toughness of the base. At the same time, it is also easy to machine, reducing the cost of high-wear-resistant metal materials and processing costs.

[0040] As a preferred embodiment, the method comprises the following steps: mixing 6-mesh ceramic particles, ceramic powder and a binder in a certain mass ratio to obtain a ceramic particle mixture; filling the prefabricated honeycomb lost foam mold pit with the ceramic particle mixture, inserting screws in the middle of the particles, reserving a certain number of mounting holes, and then placing the entire mold in a 60°C drying room for 48 hours; then molding a 15 mm thick layer of resin sand on the inner wall of the centrifugal casting metal mold, brushing a layer of high temperature resistant coating on the inner wall of the resin sand and the surface of the end cover, and then heating the sand with a dryer for 0.5 hours; then taking out the dried honeycomb ceramic particle preforms, assembling them in sequence on the inner wall of the centrifugal casting metal model sand, with a gap of 3 mm between adjacent honeycomb ceramic particle preforms, and fixing them in the resin sand with screws; fixing the metal mold in the centrifuge The dryer air duct is again extended into the centrifuge for drying for 0.5 hours, the centrifuge is turned on, the working layer high wear-resistant metal liquid is poured first, and the centrifuge continues to centrifuge for 30 seconds after the pouring is completed, and then the matrix metal liquid is poured, and the centrifugation is continued until the poured bimetallic solution is completely solidified to form a centrifugally cast bimetallic ceramic composite grinding roller; the centrifugally cast metal mold is disassembled, and the centrifugally cast bimetallic ceramic composite grinding roller blank is taken out from the metal mold for cleaning, and firstly subjected to quenching treatment at 960°C for 4 hours, with a heating rate not exceeding 30°C / h, and after being taken out of the furnace, the grinding roller is placed on the platform of the air cooling device for air cooling to room temperature, and then placed at 150°C for 4 hours for tempering treatment, and then air-cooled to room temperature; finally, the tempered composite grinding roller is machine-processed to obtain a centrifugally cast bimetallic ceramic composite grinding roller with a working layer hardness of 60HRC.

[0041] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the above principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a centrifugally cast bimetallic ceramic composite grinding roller, characterized in that: The following steps are involved: S1, uniformly mixing ceramic particles, ceramic powder and a binder in a certain mass ratio to obtain a ceramic particle mixture; S2, filling the ceramic particle mixture into a prefabricated lost foam, and placing it in a drying oven for drying, to obtain a honeycomb-shaped ceramic particle preform (1); S3, forming a layer of resin sand on the inner wall of the metal mold (2), brushing a layer of high temperature resistant coating on the inner wall of the resin sand and the surface of the end cover, and then heating the sand in a dryer for a period of time to form a centrifugal casting device; S4, assembling and fixing the ceramic particle preforms (1) in S2 on the inner wall of the molding sand of the metal mold (2) in S3 in sequence, the molding sand layer (6) and the ring wall of the metal mold (2) are provided with a plurality of air outlet holes (9) from the inside to the outside; the honeycomb holes (11) of the ceramic particle preforms (1) are conical through holes, and the small hole ends thereof are attached to the molding sand for assembly; the small diameter ports (12) of adjacent honeycomb holes (11) are connected through guide grooves (13); the joint surfaces of two adjacent ceramic particle preforms (1) are provided with interlaced concave and convex interlocking structures, and the interlocking structures of the two adjacent ceramic particle preforms are adapted to fit and buckle; S5, fixing the metal mold (2) in S4 on the centrifuge, drying the molding sand again with a dryer for a period of time, then starting the centrifuge, first pouring the working layer of high-wear-resistant molten metal, continuing centrifugation for 30-60 seconds after pouring, and then pouring the base molten metal, continuing centrifugation until the poured bimetallic solution is completely solidified, and forming a bimetallic ceramic composite grinding roller blank; the centrifugal force causes the high-wear-resistant molten metal to fill the honeycomb holes and the guide grooves, and the high-wear-resistant molten metal forms an embedded mesh metal structure on the outer arc surface of the ceramic particle preform; the high-wear-resistant molten metal filling the matching gap between two adjacent ceramic particle preforms forms a continuous winding metal edge; S6, taking out and cleaning the bimetallic ceramic composite grinding roller blank, cooling it to room temperature after quenching treatment, cooling it to room temperature again after tempering treatment, and finally machining it to obtain a finished bimetallic ceramic composite grinding roller.

2. The method for preparing a centrifugally cast bimetallic ceramic composite grinding roller according to claim 1, characterized in that: In step S1, the ceramic particles are a mixture of one or more of Al2O3, ZrO2, TiC, WC, and Si3N4; the ceramic powder is one or more of boron carbide, titanium oxide, and sodium borate, and the added mass of the ceramic powder is 0.5%-2% of the ceramic particles; the binder is an inorganic binder, and the added mass of the binder is 4%-8% of the ceramic particles.

3. The method for preparing a centrifugally cast bimetallic ceramic composite grinding roller according to claim 2, characterized in that: The resin molding sand is alkaline phenolic resin sand; in steps S3-S4, the molding sand is heated for 0.5-1h before and after the ceramic particle preform is assembled to the inner wall surface of the molding sand, and the temperature of the drying machine is set to 200-300°C.

4. The method for preparing a centrifugally cast bimetallic ceramic composite grinding roller according to claim 3, characterized in that: In step S5, the high wear-resistant molten metal is one of BTMCr20, BTMCr26, and ZGMn13, and its pouring amount is 1 / 2-2 / 3 of the mass of the grinding roller; the matrix molten metal is ductile iron or low carbon steel, and its pouring amount is 1 / 3-1 / 2 of the mass of the grinding roller.

5. The method for preparing a centrifugally cast bimetallic ceramic composite grinding roller according to claim 4, characterized in that: In step S6, the bimetallic ceramic composite grinding roller blank is first subjected to quenching treatment at 960-1020°C for 4-8 hours, with a heating rate not exceeding 30-60°C / h. After being taken out of the furnace, it is air-cooled to room temperature, and then placed in 150-200°C for tempering treatment at 4-8 hours, and then air-cooled to room temperature.

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