Mould and method for preparing porous ceramic preform

Abstract

The mold comprises an upper mold body, a middle mold body and a lower mold body which are sequentially connected in a matched mode from top to bottom, the lower mold body comprises a bottom plate, a plurality of honeycomb hole cores and fine hole cores are connected to the bottom plate, and honeycomb hole grooves and fine hole grooves are formed in the bottom of the upper mold body; and the honeycomb hole cores and the slim hole cores penetrate through the middle mold and are inserted into the honeycomb hole grooves and the slim hole grooves in a one-to-one correspondence manner. The preparation method comprises the following steps: uniformly mixing the ceramic particles, the binder, the metal powder and the organic pore-forming agent to form a mixture; filling a mold with the prepared mixture, putting the mold into an oven for baking, and taking out a preliminary ceramic preform from the mold after baking is completed; and finally, carrying out vacuum sintering on the primary ceramic preform on a shape-following graphite mold, and cooling to obtain the porous ceramic preform. The problems of ceramic loosening and deformation in the ceramic preform preparation process are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of wear-resistant composite materials, and specifically relates to a mold for preparing a porous ceramic preform, and also relates to a method for preparing a porous ceramic preform. Background Art

[0002] The ceramic particle-reinforced metal matrix wear-resistant composite material has the characteristics of toughness, high strength, and wear resistance. At present, the common method is to prepare this kind of wear-resistant composite material by gravity casting infiltration. It is necessary to first make the ceramic particles into a preform with a certain strength and a certain porosity, then place the preform in a sand mold and fix it at the worn part. After melting the metal matrix alloy, it is poured into the sand mold and infiltrated into the pores of the preform by gravity to wrap the preform, and finally a wear-resistant composite material is obtained.

[0003] When preparing the wear-resistant composite material by this method, first of all, a ceramic preform needs to be prepared. If the strength of the ceramic preform is not high, it will break during the installation and fixation process, and the ceramic preform will be washed away by the molten metal during pouring. In order to facilitate the infiltration of the molten metal into the preform, many uniform and fine pores need to be formed between the ceramic particles, and the overall preform needs to have a honeycomb hole structure with a larger diameter. The more pores there are between the ceramics, the lower the strength of the ceramic preform. The formation of honeycomb holes with a larger diameter is guaranteed by the mold. The contradiction between porosity and strength increases the difficulty of preparing the preform.

[0004] Existing patents describe more about the preparation methods of ceramic-reinforced composite materials, but there is little involvement in the preparation of ceramic preforms. The prior art with the publication number CN109053215B discloses a honeycomb ZTA ceramic preform coated with Fe-Cr-Ni-Ti fine powder and its preparation and application. The patent mentions that the mixed material is filled into a mold, and the preform is shaped and compacted by fastening the mold, and CO 2 gas is continuously introduced for curing, and then dried and demolded to obtain the target product, the honeycomb ZTA ceramic preform coated with Fe-Cr-Ni-Ti fine powder. However, the ceramic preform prepared by this technology is relatively simple, with a small size and relatively few holes, so the strength and deformation problems of the ceramic preform are not considered.

[0005] In order to solve the very key problem of preparing the ceramic preform in the process of preparing the wear-resistant composite material, the present invention solves the problems of ceramic looseness and deformation in the process of preparing the ceramic preform by means of adding a pore-forming agent, designing the mold, and adjusting the sintering process and parameters, and prepares a ceramic preform with high strength. Summary of the Invention

[0006] The purpose of the present invention is to provide a mold for preparing a porous ceramic preform, which solves the problems of ceramic looseness and deformation in the process of preparing the ceramic preform.

[0007] Another object of the present invention is to provide a method for preparing a porous ceramic preform.

[0008] The first technical solution adopted by the present invention is a porous ceramic preform preparation mold, which includes an upper mold, a middle mold and a lower mold that are sequentially and cooperatively connected from top to bottom. The lower mold includes a bottom plate, and a plurality of honeycomb hole cores and fine hole cores are connected to the bottom plate. A honeycomb hole groove and a fine hole groove are provided at the bottom of the upper mold, and the honeycomb hole cores and the fine hole cores pass through the middle mold and are inserted into the honeycomb hole groove and the fine hole groove in one-to-one correspondence.

[0009] The feature of the first technical solution of the present invention is further that, The opposite sides of the top of the middle mold are set to be arc-shaped, and the opposite sides of the bottom of the upper mold are set to be concave arc grooves. The radian of the two side arc grooves is the same as the arc radian of the top of the middle mold.

[0010] The second technical solution adopted by the present invention is a method for preparing a porous ceramic preform, which specifically includes the following steps: Step 1, mixing ceramic particles, a binder, metal powder and an organic pore former evenly to form a mixture; Step 2, filling the mixture prepared in Step 1 into the mold, compacting the mixture in the mold by using the upper mold, and then extracting the lower mold from the bottom of the mold; Step 3, putting the mold after extracting the lower mold into an oven for baking, and taking out the preliminary ceramic preform from the mold after baking is completed; Step 4, performing vacuum sintering on the preliminary ceramic preform on a graphite mold with the same shape, and obtaining a porous ceramic preform after cooling.

[0011] The feature of the second technical solution of the present invention is further that, In Step 1, the ratio of ceramic particles, binder, and metal powder is 90 - 110:4 - 6:2 - 3; The binder is water glass or modified water glass, and the metal powder is any one or more of Ti, Mo, and Al.

[0012] In Step 1, the diameter of the organic pore former is 190 μm - 210 μm, and the addition amount accounts for 0.5% - 1% of the total amount of the mixture; The organic pore former adopts any one of polymethyl methacrylate, polyvinyl alcohol, and polyvinyl butyral.

[0013] In Step 2, the thickness of the mixture after being compacted by the upper mold is 12 mm - 16 mm.

[0014] In Step 3, the baking temperature is 80°C - 100°C, and the baking time is 3 h - 5 h.

[0015] In step 4, the temperature of vacuum sintering is 1,100°C to 1,200°C, and the heat preservation time is 30 min to 60 min.

[0016] The beneficial effects of the present invention are as follows: (1) The preparation mold for the porous ceramic preform of the present invention designs a conforming porous structure preform according to the shape of the wear-resistant part of the product. The mold is divided into three parts: the upper mold, the middle mold, and the lower mold. After the ceramic particles are filled, the upper mold can compact the particles to improve the strength. The lower mold can be completely withdrawn from the bottom, thus forming pores while avoiding the problem of loosening the surface particles when core-pulling from the top, which overall improves the strength of the preform. At the same time, the conforming mold can ensure that the ceramic preform does not deform during the sintering process, and a conforming ceramic preform suitable for ceramic-metal wear-resistant composites can be successfully prepared.

[0017] (2) The preparation method of the porous ceramic preform of the present invention is not only applicable to the preparation of ceramic preforms with larger sizes, but also suitable for conforming ceramic preforms with more complex shapes. The ceramic preform is composed of many ceramic particles connected together. The more pores there are between the particles, the weaker the connection between the particles will be, resulting in a decrease in the strength between the particles and thus affecting the overall strength of the ceramic preform. By compacting with the mold, the compactness between the particles is improved, so that larger connecting parts are formed between the particles, thereby increasing the connection strength between the particles. It solves the most critical problem of the contradiction between the porosity and strength of the ceramic preform in the preparation process of ceramic-reinforced metal matrix composites.

[0018] In addition, the high-temperature sintering during preparation is conducive to the full reaction of the additives and metal powder, forming sintering necks between the ceramic particles, improving the overall strength of the preform. At the same time, the high-temperature sintering ensures that the organic pore-forming agent is fully decomposed to form uniform and fine pores. After the organic matter decomposes, carbon elements will be left on the ceramic surface, which is beneficial to the interfacial bonding between the molten metal and the ceramic. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of the preparation mold for the porous ceramic preform of the present invention; Figure 2 is a side view exploded view of the preparation mold for the porous ceramic preform of the present invention; Figure 3 is the ceramic preform prepared by the preparation method of the porous ceramic preform of the present invention.

[0020] In the figure, 1. upper mold, 2. middle mold, 3. lower mold, 4. bottom plate, 5. honeycomb hole core, 6. fine hole core, 7. honeycomb hole groove, 8. fine hole groove. Detailed Embodiments

[0021] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0022] Embodiment 1 The porous ceramic preform preparation mold of the present invention, as Figure 1 shown, includes an upper mold 1, a middle mold 2, and a lower mold 3 that are sequentially and cooperatively connected from top to bottom. The lower mold 3 includes a bottom plate 4, and a plurality of honeycomb pore cores 5 and fine pore cores 6 are connected to the bottom plate 4. A honeycomb pore groove 7 and a fine pore groove 8 are provided at the bottom of the upper mold 1. The honeycomb pore cores 5 and the fine pore cores 6 pass through the middle mold 2 and are inserted into the honeycomb pore groove 7 and the fine pore groove 8 in one-to-one correspondence.

[0023] Furthermore, as Figure 2 shown, the opposite sides of the top of the middle mold 2 are set to be arc-shaped, and the opposite sides of the bottom of the upper mold 1 are set to be concave arc grooves. The radian of the two side arc grooves is the same as the arc radian of the top of the middle mold 2.

[0024] Embodiment 2 The preparation method of the porous ceramic preform of the present invention uses the above-mentioned porous ceramic preform preparation mold, and specifically includes the following steps: Step 1, mixing ceramic particles, a binder, metal powder, and an organic pore former evenly to form a mixture; Step 2, filling the mixture prepared in Step 1 into the mold, using the upper mold 1 to compact the mixture in the mold. The thickness of the compacted mixture is 12 mm to 16 mm, and then the lower mold 3 is extracted from the bottom of the mold; Step 3, putting the mold after extracting the lower mold 3 into an oven for baking. The baking temperature is 80 °C to 100 °C, and the baking time is 3 h to 5 h. After baking is completed, the preliminary ceramic preform is taken out from the mold; Step 4, performing vacuum sintering on the preliminary ceramic preform on a conforming graphite mold. The vacuum sintering temperature is 1100 °C to 1200 °C, and the holding time is 30 min to 60 min. After cooling, a porous ceramic preform is obtained.

[0025] Embodiment 3 The preparation method of the porous ceramic preform of the present invention specifically includes the following steps: Step 1, mixing ceramic particles, a binder, metal powder, and an organic pore former evenly to form a mixture; In Step 1, the ratio of ceramic particles, binder, and metal powder is 90 - 110:4 - 6:2 - 3; The binder is water glass or modified water glass; The metal powder is any one or more of Ti, Mo, and Al. When multiple elements are selected, the powders of each element are proportioned in any ratio.

[0026] The diameter of the organic pore former is 190 μm to 210 μm, and the addition amount accounts for 0.5% to 1% of the total amount of the mixture; The organic pore former is any one of polymethyl methacrylate, polyvinyl alcohol, and polyvinyl butyral.

[0027] Step 2: Fill the mixture prepared in Step 1 into a mold, and use the upper mold 1 to compact the mixture in the mold. After compaction, the thickness of the mixture is 12 mm to 16 mm, and then draw out the lower mold 3 from the bottom of the mold; Step 3: Put the mold after drawing out the lower mold 3 into an oven for baking. The baking temperature is 80°C to 100°C, and the baking time is 3 h to 5 h. After baking is completed, take out the preliminary ceramic preform from the mold; Step 4: Perform vacuum sintering on the preliminary ceramic preform on a graphite mold with the same shape. The temperature of the vacuum sintering is 1100°C to 1200°C, and the holding time is 30 min to 60 min. After cooling, a porous ceramic preform is obtained.

[0028] Example 4 In this example, a wooden mold is designed first according to the shape of the ceramic preform.

[0029] Step 1: Mix ceramic particles, binder, metal powder, and organic pore former (PVB). The ratio of ceramic particles, binder, and metal powder is 100:5:2.5. The diameter of the pore former is 200 microns, and the addition amount is 0.5%. Fill it into a graphite mold and sinter it to prepare a ceramic preform with a preform thickness of 12 mm.

[0030] Step 2: After the ceramic particles are filled into the preform mold, use the upper mold 1 with the same shape to compact the ceramic particles in the mold, and then draw out the lower mold 3 that forms the holes from below.

[0031] Step 3: Put the mold filled with ceramic particles into an oven for baking. The temperature is set at 80°C and the time is 3 hours. After completion, take out the ceramic preform from the mold. At this time, the ceramic preform has a certain strength.

[0032] Step 4: Put the taken-out ceramic preform on a graphite mold with the same shape and sinter it under vacuum. The sintering temperature is 1100°C and the holding time is 30 minutes. As Figure 3 shown, a high-strength ceramic preform is obtained after cooling.

[0033] Example 5 In this example, a wooden mold is designed first according to the shape of the ceramic preform.

[0034] Step 1: Mix ceramic particles, binder, metal powder, and organic pore former (PVA). The ratio of ceramic particles, binder, and metal powder is 110:6:3. The diameter of the pore former is 200 microns, and the addition amount is 1%. Fill it into a graphite mold and sinter to prepare a ceramic preform with a thickness of 16 mm for the preform.

[0035] Step 2: After filling the ceramic particles into the preform mold, compact the ceramic particles in the mold with the conforming upper mold 1, and then remove the lower mold 3 that forms the hole from below.

[0036] Step 3: Place the mold filled with ceramic particles as a whole in an oven, set the temperature to 100 °C, and the time to 5 hours. After completion, take out the ceramic preform from the mold. At this time, the ceramic preform has a certain strength.

[0037] Step 4: Place the taken-out ceramic preform on a conforming graphite mold and sinter it under vacuum. The sintering temperature is 1200 °C, and keep it warm for 60 minutes. After cooling, a high-strength ceramic preform is obtained.

[0038] Example 6 In this example, a wooden mold is designed first according to the shape of the ceramic preform.

[0039] Step 1: Mix ceramic particles, binder, metal powder, and organic pore former (PMMA). The ratio of ceramic particles, binder, and metal powder is 90:4:2. The diameter of the pore former is 200 microns, and the addition amount is 0.75%. Fill it into a graphite mold and sinter to prepare a ceramic preform with a thickness of 14 mm for the preform.

[0040] Step 2: After filling the ceramic particles into the preform mold, compact the ceramic particles in the mold with the conforming upper mold 1, and then remove the lower mold 3 that forms the hole from below.

[0041] Step 3: Place the mold filled with ceramic particles as a whole in an oven, set the temperature to 90 °C, and the time to 4 hours. After completion, take out the ceramic preform from the mold. At this time, the ceramic preform has a certain strength.

[0042] Step 4: Place the taken-out ceramic preform on a conforming graphite mold and sinter it under vacuum. The sintering temperature is 1150 °C, and keep it warm for 45 minutes. After cooling, a high-strength ceramic preform is obtained. After testing, the compressive strength of the ceramic preform has increased from 6 MPa to 10 Mpa.

[0043] Example 7 In this example, a wooden mold is designed first according to the shape of the ceramic preform.

[0044] Step 1: Mix ceramic particles, binder, metal powder, and organic pore former (PMMA). The ratio of ceramic particles, binder, and metal powder is 95:5.5:2.7. The diameter of the pore former is 205 microns and the addition amount is 0.9%. Fill it into a graphite mold and sinter to prepare a ceramic preform with a preform thickness of 15 mm.

[0045] Step 2: After filling the ceramic particles into the preform mold, compact the ceramic particles in the mold with the conforming upper mold 1, and then remove the lower mold 3 that forms the holes from below.

[0046] Step 3: Place the mold filled with ceramic particles as a whole in an oven, set the temperature to 95 °C, and the time to 4.5 hours. After completion, take out the ceramic preform from the mold. At this time, the ceramic preform has a certain strength.

[0047] Step 4: Place the taken-out ceramic preform on a conforming graphite mold and sinter it under vacuum. The sintering temperature is 1100 °C, keep it warm for 50 minutes, and obtain a high-strength ceramic preform after cooling.

[0048] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0049] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A mold for preparing a porous ceramic preform, characterized in that: The invention comprises an upper die (1), a middle die (2) and a lower die (3) which are connected in sequence from top to bottom, the lower die (3) comprising a bottom plate (4), a plurality of honeycomb hole cores (5) and fine hole cores (6) being connected to the bottom plate (4), a honeycomb hole groove (7) and a fine hole groove (8) being arranged at the bottom of the upper die (1), the honeycomb hole cores (5) and the fine hole cores (6) passing through the middle die (2) and being plugged into the honeycomb hole groove (7) and the fine hole groove (8) in a one-to-one correspondence.

2. The porous ceramic preform preparation mold according to claim 1, characterized in that: The top of the middle die (2) is arranged at two opposite sides in an arc shape, and the bottom of the upper die (1) is arranged at two opposite sides in an inwardly concave arc groove, and the arcs of the arc grooves on both sides are the same as the arc of the top of the middle die (2).

3. A method for preparing a porous ceramic preform, characterized in that: The method of preparing a mold using the porous ceramic preform as claimed in claim 1 or 2 specifically comprises the following steps: Step 1, mixing ceramic particles, a binder, metal powder and an organic pore-forming agent to form a mixture; Step 2, filling the mixture prepared in step 1 into a mold, using an upper mold (1) to compact the mixture in the mold, and then removing a lower mold (3) from the bottom of the mold; Step 3, after the lower mold (3) is removed, the mold is placed in an oven for baking, and after baking, the preliminary ceramic preform is taken out from the mold; Step 4: vacuum sintering the preliminary ceramic preform on a graphite mold to obtain a porous ceramic preform after cooling.

4. The method for preparing a porous ceramic preform according to claim 3, characterized in that: In step 1, the ratio of ceramic particles, binder, and metal powder is 90-110:4-6:2-3; The binder is water glass or modified water glass, and the metal powder is any one or more of Ti, Mo, and Al.

5. The method for preparing a porous ceramic preform according to claim 3, characterized in that: The diameter of the organic pore-forming agent in step 1 is 190 μm to 210 μm, and the amount added accounts for 0.5% to 1% of the total amount of the mixture; The organic pore-forming agent is any one of polymethyl methacrylate, polyvinyl alcohol and polyvinyl butyral.

6. The method for preparing a porous ceramic preform according to claim 3, characterized in that: In the step 2, the thickness of the mixture after compaction by the upper mold (1) is 12 mm to 16 mm.

7. The method for preparing a porous ceramic preform according to claim 3, characterized in that: In step 3, the baking temperature is 80° C. to 100° C., and the baking time is 3 h to 5 h.

8. The method for preparing a porous ceramic preform according to claim 3, characterized in that: The vacuum sintering temperature in step 4 is 1100° C. to 1200° C., and the insulation time is 30 min to 60 min.

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