Metal-sand mold composite mold additive manufacturing multi-layer interface enhancing system and method thereof
Through metal surface pretreatment, sand precooling and interlayer fusion strengthening processes, the problem of weak interface bonding between metal molds and frozen sand molds was solved, achieving high-precision and efficient complex mold manufacturing, and improving casting performance and production efficiency.
Patent Information
- Application Number
- CN202510817777.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-09-12
AI Technical Summary
The existing metal mold and the frozen sand mold have weak interface bonding ability and poor interlayer bonding performance, making it difficult to achieve high-precision and efficient complex mold manufacturing.
A multi-level strategy including metal surface pretreatment, molding sand precooling, interlayer fusion strengthening and super cold treatment is adopted, including mechanical treatment, laser treatment, adhesive, water adhesive modification, low-temperature cold air and ultra-low-temperature liquid nitrogen treatment to improve the metal-sand interface bonding strength and interlayer bonding performance.
It achieves high-precision and efficient manufacturing of metal-sand composite molds, solves the problems of unstable mold quality and long cycle in traditional methods, and improves casting performance and production efficiency.
Smart Images
Figure CN120619286A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of composite mold additive manufacturing, and specifically relates to shape and property control technology for manufacturing metal-frozen sand composite molds, a multi-level interface enhancement system and method for additive manufacturing of metal-sand composite molds. Background Art
[0002] As a vital piece of basic process equipment in the equipment manufacturing industry, molds are an important indicator of a country's industrial development level. Traditional methods for processing complex cavity molds are mainly CNC milling and electrospark machining. This traditional method leads to unstable part processing quality, long processing cycles, and low production efficiency. Currently, exploring new methods for precise and efficient complex mold processing has become a hot topic in the mold manufacturing industry. In addition, the service performance reliability requirements of complex castings for high-end equipment are becoming increasingly stringent. Mold manufacturing has undergone a paradigm shift from the goal of precise control of shape accuracy to the coordinated regulation of shape and performance.
[0003] Among various casting methods, sand casting is the most widely used. It is suitable for the manufacture of castings of various alloys, structures, and sizes, with low cost and fast response. The combination of frozen sand molds and metal molds is a disruptive innovation in the mold manufacturing field. Frozen sand additive manufacturing technology is a rapid prototyping technology based on the principle of droplet injection. It uses water as a sand mold binder, freezes the sand mold in a low-temperature environment, and produces high-precision frozen sand molds through additive manufacturing. It has the advantages of low manufacturing cost, fast process design response, and environmental protection.
[0004] At present, the sand molds (cores) manufactured by frozen sand additive manufacturing technology on existing metal molds still have problems such as poor interlayer bonding ability, difficult to control sand mold performance, and insufficient flexible production level. In particular, the interface between the metal mold and the frozen sand mold, including the weak bonding ability of the frozen sand mold interlayer interface and the difficulty in maintaining shape performance are particularly prominent. It is urgent to innovate new theories, new methods and new processes to achieve high-precision, high-efficiency and high-performance manufacturing of metal-sand composite molds. Summary of the Invention
[0005] To solve the above problems, the present invention discloses a multi-level interface enhancement system and method for additive manufacturing of metal-sand composite molds, which can solve the problems of weak interlayer bonding ability and poor shape control ability in the metal-sand additive manufacturing process, obtain a combined complex cavity mold with excellent casting performance, quickly respond to the design and manufacture of multi-material composite molds, and promote the innovative development of high-end complex mold forming technology.
[0006] To achieve the aforementioned objectives, the present invention proposes a multi-level interface enhancement strategy for additive manufacturing of metal-sand composite molds. The system comprises a metal surface pretreatment module, a molding sand pre-cooling module, an interlayer fusion enhancement module, a super-cold treatment module, and a combined mold surface enhancement module. This system implements a multi-level strategy for enhancing the casting performance of metal-sand composite molds, from point (molding sand material) to surface (metal-sand mold interface) to volume (multi-module assembly). The metal-sand composite mold consists of a metal mold and a frozen sand mold. The metal mold is a mold base with a regularly shaped, complex cavity. The frozen sand mold is additively manufactured in situ on the metal mold, enabling rapid and precise forming of complex cavity molds.
[0007] As a further design of this solution, the metal surface pretreatment module refers to a metal-frozen sand mold interface strengthening method, which specifically includes mechanical treatment, laser treatment, surface grafting and adhesives, etc., aiming to improve the interface bonding strength between the metal and the frozen sand mold. The mechanical treatment refers to the use of sandpaper polishing, shot peening and anodizing to construct different degrees of rough structures on the surface of the metal mold, thereby increasing the area of contact between the frozen sand mold and it. The laser treatment is to use processes such as laser ablation to form a three-dimensional micro-nano structure on the metal surface, increase the bonding area between the metal mold and the frozen sand mold, and improve the bonding performance of the interface. The metal mold surface grafting is a method of fixing organic molecules on the metal to provide a functionalized metal mold surface. The adhesive forms chemical bonds between the atoms on the metal mold surface and the adhesive surface to achieve metal-sand mold interface load transfer.
[0008] As a further design of this solution, the molding sand pre-cooling module is to evenly spread the molding sand material on a flat plate and place it in a cold storage, thereby increasing the convection heat exchange area so that the molding sand can be quickly cooled to about -5 ~ -20 ℃; at the same time, the molding sand particles and solid dry ice powder particles can also be placed in a blender to fully mix them to lower the molding sand surface temperature and improve the surface bonding strength between the molding sand and the water adhesive.
[0009] The present invention is further improved in that the molding sand precooling method depends on the molding sand material (quartz sand, chromite sand, zircon sand and olivine sand), and the molding sand precooling temperature and precooling time are determined according to the additive manufacturing process requirements of the metal-frozen sand composite mold.
[0010] As a further design of this solution, the interlayer fusion strengthening module includes the use of water adhesive modification, sanding roller interlayer strong cooling and follow-up cold air strong cooling. The water adhesive modification is to use an aqueous solution of a mixed phase change cold storage material to change the freezing point of the water adhesive, and the grayscale printing process can also be used to control the inkjet volume and thus the interlayer bonding performance. The sanding roller interlayer strong cooling is to use a sanding roller with a surface temperature of -20 ~ -40 ℃ to compact and cool the printed surface to achieve fusion strengthening between the printed layers. The follow-up cold air strong cooling is to use low-temperature cold air to follow the printing nozzle for pneumatic strong cooling, print layer by layer, and freeze according to the shape to achieve an increase in the strength of the sand mold interlayer.
[0011] As a further design of this solution, the super-cold post-treatment process involves an ultra-low temperature (-196°C to -20°C) super-cooling treatment after the sand mold is low-temperature formed in the metal mold to ensure that the metal-frozen sand composite mold meets casting performance requirements. This super-cold post-treatment process includes, but is not limited to, the use of specific refrigeration methods such as low-temperature cold air (-5°C to -40°C), low-temperature CO2 (-20°C to -78°C), or ultra-low temperature liquid nitrogen (≥-196°C).
[0012] As a further development of this solution, the combined sand mold surface strengthening process utilizes three methods: ultra-rapid cryogenics, water mist freezing, and coating strengthening to enhance the overall strength and hardness of the metal-frozen sand composite mold after assembly. Ultra-rapid cryogenics involves rapidly cooling the sand mold using a large temperature gradient based on the measured surface temperature. For areas where the strength of the sand mold does not meet the required standards, a fine water mist spraying method is used for surface strengthening. Coating strengthening involves spraying a water-based coating onto the sand mold's interior to improve surface quality and casting performance.
[0013] The present invention also provides a specific method for a multi-level interface enhancement strategy for additive manufacturing of a metal-sand composite mold, the method comprising the following steps: Step 1: Design a rational gating, feeding, exhaust, and chilling system based on the casting CAD model. Apply the principles of segmentation to subdivide the complex casting model, minimizing the number of submodules to improve sand mold assembly accuracy. Design the material properties of the various metal-sand composite mold units.
[0014] Step 2: Based on the shape and size of the metal substrate of the composite mold, mechanical processing, laser processing, surface grafting and adhesives are used to enhance the interface bonding ability between the metal and the sand mold, providing a powder bed carrier for frozen sand additive manufacturing.
[0015] Step 3: Select the pre-cooling method (static or stirring) according to the material of the metal-sand composite mold sand. The pre-cooling temperature and pre-cooling time depend on the sand material, volume, sand grain size, etc. Pre-cool the sand material to -5 ~ -20 ℃ to improve the bonding ability of the water adhesive and the sand.
[0016] Step 4: Place the pre-cooled sand into the sand-laying device and drive the sand 3D printing equipment to produce a multi-material composite sand mold. Adjust process parameters such as the water-based adhesive printing grayscale, roller diameter and temperature, and the temperature of the follow-up cooling air device based on the properties of the frozen sand to improve the mechanical properties of the sand between printed layers.
[0017] Step 5: The printed metal-sand composite mold unit is subjected to a post-cold treatment process. Low-temperature cold air (-5℃~-40℃), low-temperature CO2 (-20℃~-78℃) or ultra-low-temperature liquid nitrogen (≥-196℃) is used to perform ultra-low temperature gradient cooling on the metal-sand composite mold unit to achieve temperature control of metal-sand composite molds of different materials, different modules and different volumes.
[0018] Step 6: Assemble, close, and surface-strengthen all printed metal-sand composite mold units to ensure the matching accuracy and strength between the composite mold units, so that adjacent units can be effectively combined into one, thereby obtaining a metal-sand composite mold with high dimensional accuracy and strength.
[0019] Beneficial effects of the present invention: 1. The present invention improves the roughness of the metal mold surface through metal-sand interface strengthening, sand pre-cooling and interlayer fusion strengthening processes, and simultaneously performs precise temperature control during sand laying and printing, thereby improving the shape and size accuracy of the metal-frozen sand composite mold.
[0020] 2. The cold treatment process and combined mold surface strengthening process are adopted to achieve the function of multi-material metal-frozen sand composite mold shape control, and at the same time solve the serious problem of floating sand on the surface of traditional sand mold.
[0021] 3. The multi-level interface enhancement strategy for additive manufacturing of metal-sand composite molds proposed in this invention provides an overall solution strategy for enhancing the performance of complex cavity metal-sand composite molds throughout the entire process from the perspective of "point-line-surface" trinity compared to previous frozen sand printing methods and processes.
[0022] 4. The metal and sand mold interfaces are effectively combined and the frozen sand mold interface is effectively connected; through high-precision matching of the metal base, rapid assembly of modular composite molds is achieved. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 , Schematic diagram of the metal-frozen sand composite mold interface strengthening method; Figure 2 , Schematic diagram of the frozen sand additive manufacturing process based on the interface strengthening strategy; Figure 3, Schematic diagram of the process flow of the multi-level interface enhancement method for metal-sand composite molds.
[0024] List of reference numerals: 1-Metal mold, 2-Frozen sand mold. DETAILED DESCRIPTION
[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inward" and "outward" refer to directions toward or away from the geometric center of a particular component, respectively.
[0026] This embodiment of the metal-sand composite mold additive manufacturing multi-level interface enhancement strategy includes a metal surface pretreatment module, a molding sand pre-cooling module, an interlayer fusion enhancement module, a super-cold treatment module, and a combined mold surface enhancement module. This system can achieve a multi-level metal-sand composite mold casting performance enhancement strategy from point (molding sand material) to surface (metal-sand mold interface) to volume (multi-module assembly). The metal-sand composite mold consists of a metal mold and a frozen sand mold. The metal mold is a regular, complex cavity mold base. The frozen sand mold is in-situ additively manufactured on the metal mold, enabling rapid and precise forming of complex cavity molds.
[0027] like Figure 1 As shown, the metal surface pretreatment module refers to a metal-frozen sand mold interface strengthening method, which specifically includes mechanical treatment, laser treatment, surface grafting and adhesives, etc., aiming to improve the interface bonding strength between the metal and the frozen sand mold. The mechanical treatment refers to the use of sandpaper polishing, shot blasting and anodizing to construct different degrees of rough structures on the surface of the metal mold, thereby increasing the area of contact between the frozen sand mold and it. The laser treatment is to use processes such as laser ablation to form a three-dimensional micro-nano structure on the metal surface, increase the bonding area between the metal mold and the frozen sand mold, and improve the bonding performance of the interface. The metal mold surface grafting is a method of fixing organic molecules on the metal to provide a functionalized metal mold surface. The adhesive forms chemical bonds between the atoms on the metal mold surface and the adhesive surface to achieve metal-sand mold interface load transfer.
[0028] like Figure 2The manufacturing process for turbine disks is shown in the figure. The molding sand pre-cooling module evenly spreads the molding sand material on a flat plate and places it in a cold storage, increasing the convective heat transfer area and rapidly cooling the sand to approximately -5 to -20°C. Alternatively, the molding sand particles can be mixed with solid dry ice powder in a blender to lower the surface temperature and improve the surface bonding strength between the sand and the water adhesive. The sand pre-cooling method depends on the sand material (quartz sand, chromite sand, zircon sand, or olivine sand). The pre-cooling temperature and duration are determined by the additive manufacturing process requirements for metal-frozen sand composite molds. The interlayer fusion enhancement module includes water adhesive modification, interlayer cooling with sand rollers, and follow-up cooling with cold air. Water adhesive modification involves changing the freezing point of the water adhesive using an aqueous solution of a mixed phase change cold storage material. Grayscale printing can also be used to control the inkjet volume and, therefore, the interlayer bonding performance. The interlayer forced cooling method uses sand rollers with a surface temperature of -20°C to -40°C to compact and cool the printed surface, achieving fusion and strengthening between printed layers. The follow-up cold air forced cooling method uses low-temperature cold air to follow the print nozzle for pneumatic forced cooling, printing layer by layer and freezing in sync with the shape, thereby improving the interlayer strength of the sand mold. The super-cold post-treatment process involves an ultra-low temperature (-196°C to -20°C) supercooling treatment after the sand mold is low-temperature formed on the metal mold to ensure that the metal-frozen sand composite mold meets casting performance requirements. This super-cold post-treatment process includes but is not limited to the use of specific cooling methods such as low-temperature cold air (-5°C to -40°C), low-temperature CO2 (-20°C to -78°C), or ultra-low temperature liquid nitrogen (≥-196°C). The combined sand mold surface strengthening process uses three methods: extreme low temperature, water mist freezing, and coating strengthening to improve the overall strength and hardness of the metal-frozen sand composite mold after assembly. Extreme low-temperature cooling involves rapidly cooling the sand mold using a large temperature gradient based on the measured surface temperature. For areas where sand mold strength is substandard, surface strengthening is achieved by spraying a fine water mist. Coating strengthening involves spraying a water-based coating onto the interior of the sand mold to improve surface quality and casting performance.
[0029] like Figure 3 As shown, this embodiment also provides a specific method for the multi-level interface enhancement strategy of additive manufacturing of metal-sand composite molds, which includes the following steps: Step 1: Design a rational gating, feeding, exhaust, and chilling system based on the casting CAD model. Apply the principles of segmentation to subdivide the complex casting model, minimizing the number of submodules to improve sand mold assembly accuracy. Design the material properties of the various metal-sand composite mold units.
[0030] Step 2: Based on the shape and size of the metal substrate of the composite mold, mechanical processing, laser processing, surface grafting and adhesives are used to enhance the interface bonding ability between the metal and the sand mold, providing a powder bed carrier for frozen sand additive manufacturing.
[0031] Step 3: Select the pre-cooling method (static or stirring) according to the material of the metal-sand composite mold sand. The pre-cooling temperature and pre-cooling time depend on the sand material, volume, sand grain size, etc. Pre-cool the sand material to -5 ~ -20 ℃ to improve the bonding ability of the water adhesive and the sand.
[0032] Step 4: Place the pre-cooled sand into the sand-laying device and drive the sand 3D printing equipment to produce a multi-material composite sand mold. Adjust process parameters such as the water-based adhesive printing grayscale, roller diameter and temperature, and the temperature of the follow-up cooling air device based on the properties of the frozen sand to improve the mechanical properties of the sand between printed layers.
[0033] Step 5: The printed metal-sand composite mold unit is subjected to a post-cold treatment process. Low-temperature cold air (-5℃~-40℃), low-temperature CO2 (-20℃~-78℃) or ultra-low-temperature liquid nitrogen (≥-196℃) is used to perform ultra-low temperature gradient cooling on the metal-sand composite mold unit to achieve temperature control of metal-sand composite molds of different materials, different modules and different volumes.
[0034] Step 6: Assemble, close, and surface-strengthen all printed metal-sand composite mold units to ensure the matching accuracy and strength between the composite mold units, so that adjacent units can be effectively combined into one, thereby obtaining a metal-sand composite mold with high dimensional accuracy and strength.
[0035] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.
Claims
1. A multi-level interface enhancement system for additive manufacturing of metal-sand composite molds, characterized by: It includes a metal surface pretreatment module, a molding sand pre-cooling module, an interlayer fusion strengthening module, an over-cold treatment module and a combined mold surface strengthening module. The molding sand material-metal sand mold interface-multi-module is assembled to obtain a multi-layer metal-sand composite mold; the metal-sand composite mold is composed of a metal mold and a frozen sand mold. The metal mold is a complex cavity mold base with a regular shape, and the frozen sand mold is manufactured by in-situ additive manufacturing on the metal mold.
2. A multi-level interface enhancement method for additive manufacturing of metal-sand composite molds, characterized in that :The method comprises the following steps: Step 1: Design a reasonable gating system, feeding system, exhaust system, and chilling system based on the casting CAD model; apply the subdivision principle to divide the complex casting model into smaller submodules to improve the assembly accuracy of the sand mold; and design the material properties of different metal-sand composite mold units; Step 2: Based on the shape and size of the composite mold metal substrate, mechanical processing, laser processing, metal surface grafting and adhesives are used to enhance the interface bonding ability between the metal and the sand mold to provide a powder bed carrier for frozen sand additive manufacturing; Step 3: Select the pre-cooling method according to the material of the metal-sand composite mold sand. The pre-cooling method includes static or stirring. The pre-cooling temperature and pre-cooling time depend on the sand material, volume, sand grain size, etc. Pre-cool the sand material to -5 ~ -20 ℃ to improve the bonding ability of the water adhesive and the sand; Step 4: Place the pre-cooled molding sand into the sand laying device, and drive the sand mold 3D printing equipment to manufacture a multi-material composite sand mold; use one or more combinations of water adhesive modification, strong cooling between sand laying roller layers, or follow-up cold air strong cooling; set the water adhesive printing grayscale, roller diameter and temperature, and follow-up cold air device temperature process parameters according to the performance of the frozen sand mold to improve the mechanical properties of the sand mold between printed layers; Step 5: The printed metal-sand composite mold unit is subjected to a post-cold treatment process. The metal-sand composite mold unit is subjected to ultra-low temperature gradient cooling using low-temperature cold air of -5℃ to -40℃, low-temperature CO2 of -20℃ to -78℃, or ultra-low temperature liquid nitrogen ≥-196℃ to achieve temperature control of metal-sand composite molds of different materials, different modules, and different volumes. Step 6: Assemble, close, and surface-strengthen all printed metal-sand composite mold units to ensure the matching accuracy and strength between the composite mold units, so that adjacent units can be effectively combined into one, thereby obtaining a metal-sand composite mold with high dimensional accuracy and strength.
3. A multi-level interface enhancement method for additive manufacturing of a metal-sand composite mold according to claim 2, characterized in that : The mechanical treatment in step 2 refers to the use of sandpaper polishing, shot peening and anodizing to construct different degrees of rough structures on the surface of the metal mold, thereby increasing the area of contact between the frozen sand mold and it; the laser treatment is to use laser ablation technology to form a three-dimensional micro-nano structure on the metal surface, increase the bonding area between the metal mold and the frozen sand mold, and improve the bonding performance of the interface; the metal mold surface grafting is a method of fixing organic molecules on the metal to provide a functionalized metal mold surface; the adhesive is to form chemical bonds through atoms on the metal mold surface and the adhesive surface to achieve metal-sand interface load transfer.
4. A multi-level interface enhancement method for additive manufacturing of a metal-sand composite mold according to claim 2, characterized in that : In step 3, the static cooling is to evenly spread the molding sand material on a flat plate and place it in a cold storage to increase the convection heat exchange area so that the molding sand is quickly cooled to -5 ~ -20 ° C; the stirring cooling is to place the molding sand particles and solid dry ice powder particles in a mixer to fully mix them to reduce the surface temperature of the molding sand and improve the surface bonding strength between the molding sand and the water adhesive.
5. The multi-level interface enhancement method for additive manufacturing of metal-sand composite molds according to claim 2, characterized in that: The water binder modification in step 4 is to change the freezing point of the water binder by using an aqueous solution of a mixed phase change cold storage material, or to control the inkjet amount and thus the interlayer bonding performance by using a grayscale printing process; the interlayer strong cooling of the sanding roller is to use a sanding roller with a surface temperature of -20 ~ -40 ° C to compact and cool the printed surface to achieve fusion and strengthening between the printed layers; the follow-up cold air strong cooling is to use low-temperature cold air to follow the printing nozzle for pneumatic strong cooling, print layer by layer, and freeze according to the shape to achieve an improvement in the interlayer strength of the sand mold.
6. The method for multi-level interface enhancement in additive manufacturing of metal-sand composite mold according to claim 1, characterized in that: The combined sand mold surface strengthening process in step 6 adopts three methods: extreme low temperature, water mist freezing and coating strengthening to improve the overall strength and hardness of the metal-frozen sand composite mold after assembly; extreme low temperature is to quickly cool the sand mold with a large temperature gradient according to the actual measured temperature of the sand mold surface; if the local strength of the sand mold does not meet the standard, the surface is strengthened by spraying fine water mist; the coating strengthening is to spray water-based coating on the inner cavity of the sand mold to improve the surface quality and casting performance of the sand mold.