A mold core and a sagger mold based on the mold core.

Abstract

This invention discloses a mold core and a sagger mold based on the mold core. A wear-resistant layer with a certain elasticity is prepared on the top of the mold core to obtain a wear-resistant mold core. The wear-resistant layer is a resin wear-resistant layer. The mold core is then assembled with an outer mold, a cover mold, a metal frame, and an upper pressure plate to form a sagger mold. Because the resin wear-resistant layer naturally possesses a certain elasticity, the mold surface experiences uniform pressure, reducing pressure-induced damage to the mold caused by excessive accumulation of large-diameter materials in certain areas. Simultaneously, relying on the elasticity of the wear-resistant layer, the pressure during mold closing can be uniformly converted into lateral forces for powder material migration, reducing frictional damage to the mold from the powder material and wear-resistant layer detachment damage caused by deformation of the mold core during mold closing pressure. This reduces mold damage and extends mold life. This invention has a simple structure, is easy to use, and is highly practical, significantly improving the service life and stability of molds.

Description

Technical Field

[0001] This invention belongs to the field of molds and relates to a positive electrode material sagger mold, specifically to a mold core and a sagger mold based on the mold core. Background Technology

[0002] A sagger is a type of kiln furniture material used to hold and prevent contamination of lithium-ion battery cathode materials during the high-temperature calcination process.

[0003] Currently, the saggers used in cathode material production are mainly oxide-based, including fused silica, mullite, mullite-corundum, and mullite-cordierite saggers. These saggers can operate at temperatures up to 1300℃ under oxidizing atmospheres, meeting the firing requirements of various cathode materials. Common raw materials for preparing oxide-based saggers include mullite, cordierite, corundum, and magnesium aluminum spinel. The saggers are typically formed by pressing, and after drying, they are fired at high temperatures in a kiln to obtain the final product.

[0004] Due to limitations in raw materials and sagger structure design, the following problems exist during sagger pressing:

[0005] (1) Mold surface wear: Since the raw material is a powder with varying particle size and high hardness, the relative movement between the mold and the material will cause mold wear and reduce mold life. Among them, the bottom surface of the sagger and the top surface of the mold core are the opposite bearing surfaces. During pressing, the material moves from the top surface of the mold core to the four sides, and the wear of the top surface of the mold core is particularly severe. At present, the conventional mold life in the industry is only about 15,000 molds. The mold repair cycle is long and the cost is high. Frequent mold repair also causes the problem of unstable production in the industry. Therefore, there is an urgent need for a mold with good wear resistance.

[0006] (2) Difficult demolding: The pressure of the sagger blank is high, and the material is a powder with large polarity difference, which will absorb the release agent. After the blank is formed, it is difficult to demold, resulting in slow production pace and complicated maintenance.

[0007] Currently, the industry mainly uses surface coating technologies such as nitriding, PVD, CVD, and TD to improve the wear resistance of molds. However, since the inner bottom surface is the pressure-bearing surface during sagger pressing, the mold surface improved by the above methods is a rigid surface and does not have pressure-bearing capacity. During multiple pressing processes, the coating layer is easy to fall off, and the improvement on the wear resistance and life of the mold is not ideal. Therefore, it is necessary to develop a new wear-resistant layer to improve the service life and stability of the mold. Summary of the Invention

[0008] The purpose of this invention is to provide a sagger mold for lithium battery cathode materials coated with a polyester layer, so as to solve the problems mentioned in the background art.

[0009] The purpose of this invention is to provide a mold core for sagger molds, which greatly improves the mold life and stability by making a special wear-resistant layer on the surface of the mold core.

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A core for a positive electrode material crucible mold includes a core body. A micron-level textured structure is first processed on the pressure-bearing surface at the top of the core body, followed by the processing of a resin wear-resistant layer. Because the resin wear-resistant layer naturally possesses a certain degree of elasticity, the mold surface experiences uniform pressure, reducing pressure-type damage to the mold caused by excessive accumulation of large-diameter materials in localized areas. Simultaneously, relying on the elasticity of the wear-resistant layer, the pressure during mold closing can be uniformly converted into lateral forces for powder material migration, reducing frictional damage to the mold from the powder material, thereby reducing mold damage and extending mold life. Furthermore, compared to traditional coating methods, this invention also exhibits stronger resistance to positive pressure impact and is less prone to failure due to mold deformation.

[0012] As a preferred technical solution, the pressure-bearing surface at the top of the mold core body is provided with raised edges around it, the micron-level texture structure is located in the area enclosed by the edges, and the resin wear-resistant layer is height-matched with the edges.

[0013] The specific principle of the wear-resistant layer of this invention in resisting normal pressure impact is as follows:

[0014] Analysis of material migration direction during the pressing process (generally lateral migration) reveals that the material exerts a lateral force on the coating. During pressing, the pressure is immense, and the mold core's bearing surface is prone to slight deformation under high pressure. While traditional coating methods can achieve good interfacial bonding, the wear-resistant layers prepared using these methods are all hard coatings, making them unable to withstand high pressure. During mold closing, the wear-resistant layer is easily peeled off under the pressure perpendicular to the bearing surface transmitted through the sagger blank. Furthermore, as the pressing pressure increases, the deformation of the mold core increases, and the tearing force between the mold core and the wear-resistant layer increases sharply, leading to a drastic reduction in lifespan. This not only results in short mold life and poor production line stability during sagger production but also severely limits high-pressure pressing production, hindering the production of deep, complex sagger parts and impeding production speed. After researching this issue, the applicant of this invention sought a solution and, through multiple experiments, discovered that preparing a micron-level textured structure on the top of the mold core and coating it with a wear-resistant layer with a certain degree of elasticity can significantly improve the lifespan of the wear-resistant layer.

[0015] The micron-level texture structure consists of two levels of micron-level grooves of different depths, with the shallower second-level micron-level grooves being denser than the deeper first-level micron-level grooves. This invention uses the less dense and deeper first-level micron-level groove structure to create large-branch-shaped reinforcing connection points between the wear-resistant layer and the mold core, and the shallower but denser second-level micron-level groove structure to create capillary-type reinforcing connection points between the wear-resistant layer and the mold core. The large branch-shaped reinforcing connection points enhance the ability of the wear-resistant layer and the mold core to withstand large deformation impacts, while the capillary-shaped reinforcing connection points improve the ability of the wear-resistant layer and the mold core to withstand small deformation impacts and resist deformation under continuous high pressure holding. Reinforcing connection points generated through different levels of texture structure further enhance impact resistance and deformation resistance. This invention effectively addresses the impact of large lateral sliding displacement of the material relative to the mold core in the early stages of compaction, and also adapts to the impact of mold core deformation under small displacement but large pressure in the middle and later stages of compaction, as well as resisting deformation under continuous high pressure holding. Combined with the flexibility of the coating layer itself, the coating layer of this invention can deform along with the surface deformation of the mold core, resulting in a much better resistance to positive pressure impacts than existing hard coating layers. Through the above-mentioned technical means of this invention, the coating layer's resistance to frontal impacts is greatly improved, effectively preventing the wear-resistant layer from falling off during the compaction process, thus increasing the service life of the wear-resistant layer and consequently, the overall service life of the mold.

[0016] On the other hand, the present invention also protects a crucible mold for lithium battery cathode materials, including an outer mold, a cover mold and the aforementioned mold core, wherein the top of the mold core, the inner side of the outer mold and the bottom surface of the cover mold together form the crucible forming space.

[0017] On the other hand, the present invention also provides a core forming process.

[0018] First, design and process the mold core according to the dimensions of the sagger;

[0019] Clean the oil stains off the mold, and then remove the oil stains from the mold through deep sandblasting;

[0020] Then, a first-level micron-textured wax film is applied to the surface of the mold core;

[0021] The mold core is etched with an etching solution to obtain the desired groove array. After removing the surface residue (first-level micron-scale textured wax film), the mold core with the first-level micron-scale textured structure on the top is obtained.

[0022] The above-mentioned mold core is then subjected to a similar process, with a two-dimensional micron-scale textured wax film applied and etched to obtain a mold core with a complete texture.

[0023] The second-level micron-level groove texture can also be applied by direct laser processing.

[0024] Polyurethane is coated onto the micron-scale textured surface of the mold core, which is then flattened by roller pressing, and the edges and corners are corrected before high-temperature curing to obtain a mold core with a wear-resistant layer.

[0025] Due to the adoption of the above-mentioned technology, the beneficial effects of the present invention compared with the prior art are as follows:

[0026] 1. The polyester layer on the surface of the mold of the present invention has good wear resistance and a life of 25,000 cycles, which is more than 60% longer than that of ordinary metal molds.

[0027] 2. No processing or repair of the base steel model surface is required during mold repair; only the surface polyester layer needs to be replaced. Mold repair can be completed within one day, greatly reducing the mold maintenance cycle. The cost is also only 1 / 3 of the original mold repair cost.

[0028] 3. Relying on the self-rebound effect of polyester, it is easy to demold after pressing into a blank, and the production cycle of a single mold is reduced by 20%; at the same time, the use of release agent on the inner mold surface of the sagger bottom can be reduced to 1 / 4 of the original amount, and the maintenance difficulties caused by the accumulation of release agent are effectively improved. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the mold core of the present invention.

[0030] Figure 2 This is a schematic diagram showing the regular distribution of the micron-level texture structure on the top of the mold core of the present invention.

[0031] Figure 3 This is a schematic diagram of the irregular distribution of the micron-level texture structure on the top of the mold core of the present invention.

[0032] Figure 4 This is a schematic diagram showing that the first-level micron-level groove texture on the top of the mold core of the present invention is a lychee pattern.

[0033] Figure 5 This is a diagram showing the actual processed shape of the micron-level texture structure on the top of the mold core of the present invention.

[0034] Figure 6 This is a schematic diagram of a mold core sagger mold using the present invention.

[0035] 1-Upper mold pressure plate, 2-Upper mold pad, 3-Upper mold, 4-Moving frame, 5-Mold core, 501-First-level micron-level groove texture, 502-Second-level micron-level groove texture, 6-Machine tool moving beam, 7-Ejection frame, 8-Mold core base, 9-Mold core base pressure plate, 10-Ejection cylinder, 11-Resin wear-resistant layer, 12-Edge. Detailed Implementation

[0036] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0037] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] like Figure 1 and Figure 2 As shown, the present invention provides a mold core 5 for a sagger mold. A micron-level texture structure is first processed on the upper surface of the mold core 5, and then a wear-resistant layer with a certain elasticity is processed, which can be a resin wear-resistant layer 11 (referred to as a coating layer).

[0039] As a preferred embodiment, such as Figure 2As shown, the micron-level texture structure is a two-level micron-level trench texture with different depths, wherein the shallower second-level micron-level trench texture 502 is denser than the deeper first-level micron-level trench texture 501. During the pressing process, material migration exerts a significant lateral force on the wear-resistant layer, which can easily cause it to detach, leading to its failure. Furthermore, research on actual production has revealed that while certain techniques to improve the bond between the wear-resistant layer and the die core, such as chemical modification and vapor deposition, are effective for low-pressure pressing or slow production speeds, the wear-resistant layer often detaches completely when the pressing pressure increases or the production speed accelerates. Careful analysis shows that the detachment is caused by the die core undergoing positive pressure deformation under the pressing pressure. This deformation accelerates and intensifies under high-pressure pressing or fast production, generating a significant peeling force between the wear-resistant layer and the top of the die core. This peeling force increases dramatically with increasing pressure (reaching 160MPa-300MPa or higher), rendering the existing wear-resistant layer unsuitable for high-pressure pressing and rapid production. To address this issue, the present invention designs a flexible resin wear-resistant layer 11. Before preparing the resin wear-resistant layer 11, a micron-level texture structure is processed on the top of the mold core. A first-level micron-level groove texture structure with low density and relatively deep texture creates large branch-shaped reinforcing connection points between the wear-resistant layer and the mold core. A second-level micron-level groove texture structure with shallow depth but high density creates capillary-type reinforcing connection points between the wear-resistant layer and the mold core, thus forming two levels of reinforcing connection points. This allows the resin wear-resistant layer 11 of the present invention to follow the deformation of the mold core well under positive pressure, and has very good anti-peeling performance throughout the pressing process.

[0040] In a preferred embodiment, the density of the second-level micron-level groove texture 502 is 3-15 times that of the first-level micron-level groove texture 501, with 5-10 times having the best effect on improving the life of the mold core. The density can be understood as the ratio of the area of ​​the groove to the top surface of the entire mold core 5 under the same width.

[0041] The ratio of the groove depth of the second-level micron-level groove texture 502 to the groove depth of the first-level micron-level groove texture 501 can be the same or different, specifically selected within the range of 2:3 to 1:4.5.

[0042] In a preferred embodiment, the groove depth is the main parameter affecting the anti-hair loss performance; when it is 10-45μm, the anti-hair loss performance is relatively good.

[0043] It should be noted that the grooves are generally flat, and the groove width to depth ratio is preferably 3:1 to 1:1, which provides better anti-loosening performance.

[0044] It should be noted that, through numerous experimental studies, it has been found that for micron-level textured structures, the grooves of the first-level micron-level groove texture 501 are interconnected and intersecting, which greatly improves the peel resistance and significantly enhances the mold's service life. As a preferred embodiment, the grooves of the second-level micron-level groove texture 502 are discrete dot-like grooves, which can further improve the peel resistance of the resin wear-resistant layer 11.

[0045] See Figure 2 As shown, the first-level micron-level groove texture 501 has regular grooves, and the grooves are interconnected to form a regular hexagonal splicing pattern on the top of the mold core. There are no through straight grooves. The second-level micron-level groove texture structure 502 is a discrete dot array distribution, which has good impact and peel resistance.

[0046] See Figure 3 As shown, the first-level micron-scale groove texture 501 has irregular grooves. The intersecting and connected grooves divide the top of the model into several polygons of different sizes. The polygons are roughly at the same size level, with an equivalent diameter of approximately 200-1000 micrometers. The number of sides is mostly 3-7, and the number of sides and size can be randomly distributed. The second-level micron-scale groove texture structure 502 has a mesh-like groove with a mesh spacing of 60-120 micrometers, which has a larger size than... Figure 2 Superior impact and peel resistance.

[0047] See Figure 4 and Figure 5 As shown, with Figure 4 The leather texture shown is the first-level micron-level groove texture 501, and the second-level micron-level groove texture 502 is a mesh-like groove texture. The prepared micron-level texture structure is as follows: Figure 5 As shown, this represents the optimal impact resistance in actual use.

[0048] In a preferred embodiment, the top of the mold core 2 is machined with a groove for applying a wear-resistant layer. The groove has a raised edge around it, and the edge forms the micron-level texture structure on the bottom surface of the groove. After the resin wear-resistant layer 11 is prepared, the resin wear-resistant layer 11 is flush with the top edge of the mold core 2.

[0049] Further preferred, the depth of the groove is 0-2 mm, preferably about 1 mm. This can also be understood as machining an edge about 1 mm high around the top of the mold core 2. The thickness of the coated resin wear-resistant layer 11 is also about 1 mm, and the edge width is 1-3 mm. By setting the edge, the coated layer can be laterally limited around the perimeter, which can further effectively prevent the coated layer from falling off.

[0050] It should be noted that the specific material of the resin wear-resistant layer 11 is not limited, as long as it has wear resistance, can be tightly bonded to the metal layer and will not react with the crucible material, such as common wear-resistant materials such as polyurethane, styrene-butadiene rubber, ultra-high molecular weight polyethylene, tetraphenylethylene and polytetrafluoroethylene.

[0051] It should be noted that the micron-level texture structure on the top of the mold core 5 of the present invention can be prepared by chemical etching or laser etching.

[0052] The following example illustrates the fabrication process of the micron-level textured structure on the top of the mold core 5 of this invention:

[0053] First, design and process the mold core 5 according to the dimensions of the sagger;

[0054] Clean the oil stains off the mold, and then remove the oil stains from the mold through deep sandblasting;

[0055] Then, a first-level micron-scale textured wax film is applied to the surface of mold core 5;

[0056] The mold core 5 is etched with an etching solution to obtain the desired groove array. After removing the surface residue, the mold core 5 with the first-level micron-scale texture structure on the top is obtained.

[0057] The aforementioned mold core 5 is then subjected to a similar process, by applying a secondary micron-level textured wax film and etching it, to obtain a mold core 5 with a complete texture. The secondary micron-level groove texture 502 can also be applied by direct laser processing.

[0058] Preparation of polyurethane wear-resistant layer:

[0059] First, a glass reaction vessel was prepared, and a polymeric polyol was added. Vacuum dehydration was carried out at 100℃~120℃, followed by cooling to 50℃. Diisocyanate was added in batches, and the temperature was slowly raised to 80℃. After holding the reaction at this temperature, a PU prepolymer was obtained. A chain extender was added in batches to the PU prepolymer, and the mixture was rapidly stirred for 15 seconds. This mixture was then poured into a groove at the top of a mold core at a temperature of 100℃~120℃. A steel plate was then placed over the mold surface, pressed flat, and held under pressure. Heating was stopped after holding the mold at 120℃ for 5 minutes, and the mixture was allowed to cool naturally for 1.5 hours before the steel plate was removed. After cooling, a wear-resistant layer with a thickness of 0.8-1.5 mm was formed on the surface of the mold core 5. After edge and corner correction, the mold core 5 was assembled into a crucible mold. Testing in use revealed that the crucible mold had a lifespan of 25,000 cycles, which is more than 60% longer than that of ordinary metal molds.

[0060] The mold core 5 of this invention can be used to assemble any similar sagger mold in the prior art, and the specific type is not limited. For ease of illustration, this invention provides an assembled sagger mold such as... Figure 1As shown, the main components of the sagger mold include an upper mold pressure plate 1, an upper mold pad 2, an upper mold 3, a movable frame 4, a mold core 5, a machine tool movable beam 6, an ejector frame 7, a mold core base 8, a mold core base pressure plate 9, and an ejector cylinder 10. The mold core base 8 is mounted on the mold core base pressure plate 9, and the mold core 5 is mounted on the mold core base 8. The movable frame 4 is mounted around the mold core 5 and is supported by the machine tool movable frame, allowing it to move under the drive of the machine tool. The movable frame 4 has a certain gap with the mold core 5. The ejector frame 7... Installed within this gap, the ejector frame 7 surrounds the mold core 5 and is mounted on the ejector cylinder 10. Driven by the ejector cylinder 10, it moves up and down along the gap to achieve demolding after pressing. The upper mold 3 is located above the mold core 5 and is fixed to the upper mold pressure plate 1 by the upper mold pad 2. The upper mold pressure plate 1 is driven up and down by the press to press the blank. The gap between the top of the mold core 5 and the movable frame 4 is limited by the top of the ejector frame 7 to form the side wall cavity of the sagger. The space between the upper mold 3 and the mold core 5 is the bottom cavity of the sagger.

[0061] The production process of the sagger mold is as follows:

[0062] 1. Move the upper mold 3 back to its initial height;

[0063] 2. The ejector cylinder 10 drives the ejector frame to reset to the packing depth, which is calculated based on the product wall height and material compression ratio;

[0064] 3. The moving beam 6 of the machine tool drives the moving frame 4 to rise to the height of the mold core 5 filler. The filler height is calculated based on the product thickness and the material compression ratio.

[0065] 4. Fill in the powder and level it;

[0066] 5. The press pushes the upper die 3 down to the set value;

[0067] 6. The ejector cylinder pushes the ejector frame to the set value;

[0068] 7. Pressure holding: The powder material forms a product in the closed space of the upper mold 3, mold core 5, ejector frame 7, and movable frame 4.

[0069] 8. Depressurize, and the upper mold 3 returns to its initial height, detaching from the product;

[0070] 9. The moving beam of the machine moves the moving frame 4 downward to expose the product;

[0071] 10. The ejector cylinder 10 drives the ejector frame 7 to move downwards, detaching it from the product;

[0072] 11. Use the 5 valve core of the mold core to remove the negative pressure inside the product cavity and take out the product.

[0073] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the invention do not depart from the spirit and scope of the invention and should be covered within the scope of the claims of the invention.

Claims

1. A mold core for a positive electrode material crucible mold, comprising a mold core body, characterized in that, First, a micron-level textured structure is processed on the pressure-bearing surface at the top of the mold core body, and then a resin wear-resistant layer is processed. The micron-level texture structure consists of two levels of micron-level trench textures with different depths, wherein the shallower second-level micron-level trench texture is denser than the deeper first-level micron-level trench texture. The ratio of the groove depth of the second-level micron-scale groove texture to the groove depth of the first-level micron-scale groove texture is 2:3-1:4.5; The trench depth of the first-level micron-level trench texture is 30-45μm, and the trench depth of the second-level micron-level trench texture is 10-20μm. The first-level micron-scale trench texture consists of interconnected trenches that intersect each other, while the second-level micron-scale trench texture consists of discrete dot-like trenches.

2. The mold core according to claim 1, characterized in that, The resin wear-resistant layer is made of any one of polyurethane, ultra-high molecular weight polyethylene, tetraphenylethylene, and polytetrafluoroethylene.

3. The mold core according to claim 1, characterized in that, The resin wear-resistant layer is made of polyurethane, which is coated and cured at high temperature onto the surface of the micron-scale textured structure of the mold core.

4. The mold core according to any one of claims 1-3, characterized in that, The pressure-bearing surface at the top of the mold core body has raised edges around it, the micron-level texture structure is located in the area enclosed by the edges, and the resin wear-resistant layer is height-matched to the edges.

5. A sagger mold for lithium battery cathode materials, characterized in that: It includes an outer mold, a cover mold, and a mold core as described in any one of claims 1-4, wherein the top of the mold core, the inner side of the outer mold, and the bottom surface of the cover mold together form the sagger forming space.

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