Magnesium alloy melt ingot casting mold apparatus and method with switchable cooling mode

Abstract

The present application relates to the technical field of magnesium alloy casting, and provides a magnesium alloy melt ingot casting mold device and method with switchable cooling modes. The device comprises a mold main body with an ingot cavity inside, cooling pipelines arranged in line with the outer wall of the ingot cavity, and at least two cooling medium interfaces arranged on the side wall of the mold main body. The cooling medium interfaces are respectively in communication with both ends of the cooling pipelines to form flow-through channels, and are used to selectively connect to a cooling water circulation system or a compressed air system to switch between water cooling and air cooling modes. The present application realizes on-demand flexible switching of cooling conditions, takes into account both grain refinement of high-rare-earth magnesium alloys and prevention and control of hot cracking of commercial magnesium alloys, and improves the quality of ingots and the production versatility.

Description

Technical Field

[0001] This invention specifically relates to a magnesium alloy melt casting mold device and method with switchable cooling modes, belonging to the field of magnesium alloy casting technology. Background Technology

[0002] Magnesium alloys, with their low density and high specific strength, are widely used in the production of lightweight components in transportation, electronics, and communications. Ingot casting is the fundamental process in magnesium alloy billet preparation, and the solidification process directly determines the internal grain size and final mechanical properties of the magnesium alloy. Rapid cooling is a key technological means to achieve grain refinement and improve the overall performance of the ingot. Studies have shown that with continuous increases in cooling rate, magnesium alloy grains are significantly refined, and the second phase distribution becomes more dispersed and uniform. When using graphite molds, the cooling rate of the ingot can be increased by 1-2 orders of magnitude, resulting in a significant refinement of the as-cast grain structure, with the average grain size decreasing from 138 μm to 35 μm. However, magnesium alloys face the risk of hot cracking during rapid cooling. Magnesium alloys have a high susceptibility to hot cracking, which is one of the main types of scrap. When casting magnesium alloy ingots, the casting speed and cooling intensity should not be inappropriately increased simultaneously, otherwise, the susceptibility to hot cracking will increase. For large-sized magnesium alloy ingots, especially those with high rare earth content (greater than 10 wt.%), semi-continuous casting also struggles to address issues such as large internal and external temperature differences, severe segregation, and even cracking during solidification. Therefore, achieving a balance between grain refinement and crack control remains a long-standing technical challenge in magnesium alloy ingot production.

[0003] Currently, the cooling structures of ingot molds used in magnesium alloy ingot production are relatively simple, mainly falling into the following two categories: (1) Water-cooled ingot mold.

[0004] Existing water-cooled magnesium alloy ingot molds utilize circulating cooling water through internal or external cooling water channels for forced heat exchange, achieving rapid cooling of the molten magnesium alloy. Some technical solutions incorporate a water-cooling system within the mold, resulting in rapid ingot cooling and fast solidification. For example, existing technologies provide casting molds with water-cooling structures, using the relative motion generated by mold closing to displace the liquid within the channels, ensuring a continuous supply of cooling liquid. Furthermore, some methods for preparing large-size magnesium alloy ingots employ a rising water level cooling scheme, achieving layer-by-layer cooling by controlling the water level changes within the cooling chamber.

[0005] (2) Air-cooled / air-cooled ingot mold.

[0006] Conventional air-cooled or air-cooled ingot molds rely on natural air convection or forced ventilation to remove heat from the mold, resulting in a relatively low cooling rate. Some magnesium alloy production processes use methods such as pouring the molten metal into a mold and then directly cooling it with water or air to solidify the ingot. Other studies have compared and analyzed the effects of different casting cooling methods (water-cooled copper molds, air cooling, and air cooling) on ​​the alloy's microstructure and heat transfer properties.

[0007] (3) Crystallizer technology with adjustable cooling intensity.

[0008] In the field of magnesium alloy continuous casting, there are already crystallizer technologies with adjustable cooling intensity. Related technologies indicate that reducing the casting cooling rate before the magnesium alloy completely solidifies can effectively solve the cracking problem. Wagstaff's low-level heating (LHC) casting technology in the United States uses a graphite plate lined on the upper inner wall of a traditional crystallizer, utilizing the continuous permeation lubrication and hot-top effect of the graphite for casting.

[0009] In summary, during the production of magnesium alloy ingots, the cooling rate during solidification directly determines the internal grain size and mechanical properties of the ingot. While rapid cooling helps refine grains and improve alloy strength, the suitable cooling process window varies significantly for different grades of magnesium alloys. For example, high-rare-earth magnesium alloys typically require extremely rapid cooling to achieve grain refinement, while common commercial magnesium alloys (such as AZ and ZM series) are prone to hot cracking defects due to thermal stress concentration under quenching conditions. However, existing magnesium alloy ingot molds usually employ fixed water-cooling or air-cooling structures, with a single and non-adjustable cooling mode. This fixed cooling structure cannot adapt to the differentiated solidification requirements of different grades of magnesium alloys on the same mold. As a result, when producing multiple types of magnesium alloys, either insufficient cooling intensity leads to coarse grains in high-rare-earth alloys, or excessive cooling causes commercial alloys to crack and become unusable, making it difficult to ensure both the microstructure and properties of the ingot and the yield of the finished product. Summary of the Invention

[0010] To address the problem that existing magnesium alloy ingot molds have fixed cooling modes and cannot be switched as needed to balance grain refinement and thermal crack control, this invention provides a magnesium alloy melt ingot mold device with switchable cooling modes and a cooling mode switching control method. This enables flexible switching between water cooling and air cooling conditions to meet the forming and production needs of various types of magnesium alloy ingots, thereby overcoming the shortcomings of existing technologies.

[0011] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: The first aspect of this invention provides a magnesium alloy melt casting mold apparatus with switchable cooling modes, comprising: A mold body with an ingot cavity inside, the inner wall and / or outer wall of the mold body are provided with multiple reinforcing ribs, the multiple reinforcing ribs are arranged sequentially and spaced apart along the circumference of the mold body on the wall surface of the mold body, or the multiple reinforcing ribs are arranged in a grid pattern; The mold includes cooling pipes and at least two cooling medium interfaces. The cooling pipes are arranged to fit the outer wall of the ingot cavity, and the at least two cooling medium interfaces are located on the side wall of the mold body and are respectively connected to both ends of the cooling pipes to form a cooling medium flow channel for the cooling medium to flow. The cooling medium interfaces are used to selectively connect to an external cooling water circulation system or a compressed air system, so that cooling water or compressed air can flow selectively in the cooling pipes, thereby switching between water cooling mode and air cooling mode in the mold body.

[0012] The above solution constructs a unified heat exchange channel compatible with both liquid and gaseous media by setting a common cooling medium interface on the side wall of the mold body and a cooling pipe that fits the outer wall of the cavity. This allows the same mold to seamlessly switch between water cooling and air cooling depending on the external medium, thereby adapting to the solidification characteristics of different magnesium alloy grades.

[0013] In one embodiment, the cooling pipes extend along the bottom outer wall and / or side outer wall of the ingot cavity to form a single-sided cooling structure or a surrounding cooling structure.

[0014] In one embodiment, the cross-sectional shape of the cooling pipe is any one of a circle, a rectangle, or an ellipse.

[0015] In one implementation, the outer wall of the cooling pipe is fixed to the outer wall of the ingot cavity by welding, forming a low thermal resistance contact interface.

[0016] In one embodiment, at least two cooling medium interfaces are provided on the same side wall, adjacent side walls, or opposite side walls of the mold body.

[0017] In one implementation, at least two cooling medium interfaces are combined to form at least two cooling medium interface groups. Each cooling medium interface group includes two cooling medium interfaces. One of the at least two cooling medium interface groups serves as a working interface connected to a cooling water circulation system or a compressed air system, while the others serve as backup interfaces. Alternatively, all cooling medium interface groups are externally connected to a cooling water circulation system or a compressed air system, and all cooling medium interface groups are respectively connected to the cooling pipeline to form at least two cooling medium flow channels, with the at least two cooling medium flow channels corresponding to different areas of the ingot cavity.

[0018] As one implementation method, the reinforcing rib can be any one of the following: arc-shaped structure, I-shaped structure, or T-shaped structure.

[0019] As one embodiment, the magnesium alloy melt casting mold device with switchable cooling mode further includes: a reinforced outer support and a bottom base; The reinforcing outer brackets are disposed at both ends of the mold body, and the mold body is detachably and fixedly connected to the reinforcing outer brackets through locking connectors; The reinforcing external support is fixedly installed on the top surface of the bottom base, and together with the bottom base, they form a rigid load-bearing frame.

[0020] In one embodiment, the locking connector includes any one of the following: a high-strength bolt with a flange, a quick clamp, a clamp connector, or a hinge locking mechanism.

[0021] In one embodiment, the mold body has flange faces at both ends, the mating structure of the reinforcing outer bracket is adapted to the flange faces, and the locking connector presses the flange faces to lock and fix the mold body and the reinforcing outer bracket.

[0022] In one embodiment, the top of the mold body is provided with a melt pouring opening, and an end cap is detachably and sealingly fitted at the melt pouring opening.

[0023] In one embodiment, a high-temperature resistant sealing gasket is provided between the mating surfaces of the end cap and the top surface of the mold body.

[0024] In one embodiment, the high-temperature resistant sealing gasket is any one of graphite gasket, ceramic fiber gasket, high-temperature resistant silicone rubber sealing ring, and metal spiral wound gasket.

[0025] A second aspect of this invention provides a method for switching cooling modes of magnesium alloy ingots, employing the aforementioned magnesium alloy melt ingot mold device with switchable cooling modes, comprising the following steps: Operating condition selection: Select the cooling mode according to the grade of the magnesium alloy to be cast and the target performance requirements; if rapid cooling is required to refine the grains, select the water cooling mode; if slow cooling is required to prevent hot cracking, select the air cooling mode. Piping connection: According to the selected cooling mode, connect the cooling medium interface to the corresponding cooling water circulation system or compressed air system; Molten casting: Molten magnesium alloy is poured into the ingot cavity, and the top opening of the ingot cavity is sealed after casting is completed; Cooling and solidification: Start the supply of the corresponding cooling medium, so that the cooling medium flows in the cooling pipe to cool the magnesium alloy melt in the ingot cavity until the melt is completely solidified and formed.

[0026] In one embodiment, the magnesium alloy is a high rare earth magnesium alloy with a rare earth content greater than 10 wt.%, and the cooling medium interface is connected to the cooling water circulation system accordingly, and the magnesium alloy melt in the ingot cavity is cooled in water cooling mode.

[0027] In one implementation method, under the water-cooling mode, the cooling water temperature is 18℃~22℃, and the cooling rate of the magnesium alloy melt is not less than 7℃ / s.

[0028] In one implementation, the magnesium alloy is a commercially available AZ or ZM series magnesium alloy. The cooling medium interface is connected to the compressed air system, and the magnesium alloy melt in the ingot cavity is cooled in an air-cooling mode.

[0029] In one implementation, the compressed air pressure in the air-cooling mode is 0.4 MPa ~ 0.6 MPa.

[0030] Compared with the prior art, the advantages of the present invention include: This invention breaks through the limitations of traditional, rigid mold cooling modes by using a shared cooling pipeline and a dual-function media interface. Its principle lies in utilizing a single physical heat exchange channel that accommodates the flow characteristics of both liquid water and compressed gas. By rapidly switching external pipelines, the heat capacity and convective heat transfer coefficient of the heat exchange medium are altered, thereby achieving wide-range control from high-intensity water cooling to low-intensity gas cooling on the same equipment. This design allows the production line to adapt to both the fine-grain preparation of high-rare-earth magnesium alloys and the crack-resistant production of ordinary commercial magnesium alloys without changing the molds, significantly improving the equipment's versatility and production scheduling flexibility.

[0031] This invention resolves the conflict between efficient heat exchange and mold lifespan by fully welding the cooling pipes to the outer wall of the mold cavity and constructing a low thermal resistance interface, combined with structural reinforcement through reinforcing ribs and a rigid load-bearing frame. The welded connection eliminates the thermal resistance bottleneck caused by assembly gaps, ensuring efficient heat removal under rapid cooling conditions. Meanwhile, the rigid system composed of arrayed reinforcing ribs and an external support effectively constrains the elastic deformation and plastic creep of the mold under severe thermal shock, ensuring the long-term stability of ingot dimensional accuracy. The detachable structure also reduces maintenance difficulty.

[0032] The cooling mode switching control method provided by this invention establishes a precise mapping relationship between "alloy grade - cooling mode - process parameters". By setting a water cooling rate threshold of no less than 7℃ / s for high rare earth alloys and an air cooling pressure range of 0.4-0.6MPa for commercial alloys, the boundary conditions between grain refinement and crack prevention are quantified from the perspective of process control. This method, combined with the switching capability of the hardware device, ensures that different materials solidify under their respective optimal thermal field paths, fundamentally improving the overall yield and performance consistency of magnesium alloy ingots. Attached Figure Description

[0033] Figure 1 This is a three-dimensional structural schematic diagram of a magnesium alloy melt casting mold device with switchable cooling mode provided in a typical embodiment of the present invention. Figure 2 This is a vertical sectional front view of a magnesium alloy melt casting mold device with switchable cooling mode provided in a typical embodiment of the present invention; Figure 3 This is a physical image of a magnesium alloy melt casting mold device with switchable cooling modes, provided in a typical embodiment of the present invention. Detailed Implementation

[0034] In view of the shortcomings of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0036] The terminology involved in this invention is explained as follows: Magnesium alloy ingot: A metal billet with a certain shape and size obtained by pouring molten magnesium alloy into a mold cavity and cooling and solidifying it.

[0037] Grain refinement: The process by which the grain size in the solidification structure of magnesium alloys is significantly reduced through methods such as increasing the cooling rate. Studies have shown that with the continuous increase of the cooling rate, the grains of magnesium alloys are significantly refined, the distribution of the second phase is more dispersed and uniform, and the hardness, tensile strength and elongation of the alloy are also significantly improved.

[0038] Hot cracking: Magnesium alloys develop internal stress during solidification due to hindered shrinkage or uneven cooling. When this stress exceeds the material's strength limit at that temperature, cracks form. Magnesium alloys are highly prone to hot cracking and it is one of the main types of magnesium alloy scrap.

[0039] In a more typical implementation scheme, please refer to Figure 1 , Figure 2 and Figure 3As shown, a magnesium alloy melt ingot casting mold device with switchable cooling modes includes a mold body with an internal ingot cavity 7, cooling pipes 9, and at least two cooling medium interfaces. The mold body, as the core forming component, has a hollow internal region forming the ingot cavity 7, used to accommodate molten magnesium alloy and solidify it. The cooling pipes 9 are arranged against the outer wall of the ingot cavity 7. At least two cooling medium interfaces are located on the side walls of the mold body and connected to both ends of the cooling pipes 9, forming cooling medium flow channels. The cooling medium interfaces are used to selectively connect to either an external cooling water circulation system or a compressed air system, allowing selective flow of cooling water or compressed air within the cooling pipes 9, thus switching between water-cooled and air-cooled cooling modes within the mold body.

[0040] In this invention, "selecting one external connection" means that during the same production period, the first cooling medium interface 1 and the second cooling medium interface 4 are connected to only one medium supply system, either simultaneously connected to the water circuit for water cooling or simultaneously connected to the air circuit for air cooling, rather than mixing the two media at the same time, thereby avoiding pressure fluctuations and uneven heat exchange caused by water-vapor mixing.

[0041] Specifically, at least two cooling medium interfaces include a first cooling medium interface 1 and a second cooling medium interface 4, which serve as ports for medium inflow and outflow, respectively. The first cooling medium interface 1 and the second cooling medium interface 4 can be located on opposite side walls, on the same side wall, or on adjacent side walls of the mold body.

[0042] It should be noted that the cooling medium flow channel mentioned in this invention has media compatibility in its physical structure. That is, the same set of pipeline channels allows both liquid cooling water and gaseous compressed air to flow through. The mode switching is not achieved by changing the internal mechanical structure of the mold, but by connecting the pipelines of the external system.

[0043] In the specific construction of the heat exchange channel, the cooling pipes 9 extend along the bottom outer wall and / or side outer wall of the ingot cavity 7, forming a single-sided cooling structure or a surrounding cooling structure. For example... Figure 2 As shown, the cooling pipes 9 can be laid out laterally along the bottom outer wall of the ingot cavity 7 to form a single-sided bottom cooling structure. This layout is beneficial for the directional solidification of the ingot from bottom to top. It should be understood that in other embodiments, the cooling pipes 9 can also be arranged longitudinally along the side wall or simultaneously cover the bottom and side surfaces to form a surrounding structure, in order to meet the heat dissipation requirements of ingots of different sizes.

[0044] As a preferred option, the cross-sectional shape of the cooling pipe 9 can be any one of circular, rectangular, or elliptical. For example, circular cross-section pipes are easy to process and have good pressure resistance, making them suitable for high-pressure water cooling conditions; rectangular cross-section pipes have a larger contact area with the outer wall of the cavity, which is beneficial for improving the convective heat transfer efficiency in air-cooling mode; and elliptical cross-sections take into account both contact area and fluid dynamic characteristics.

[0045] Specifically, the outer wall of the cooling pipe 9 is welded to the outer wall of the ingot cavity 7, forming a low thermal resistance contact interface. In particular, a full welding process is used to tightly fit and fix the cooling pipe 9 to the outer wall of the ingot cavity 7, eliminating air gaps caused by fit tolerances in traditional mechanical assembly. Since air is a poor conductor of heat, eliminating gaps significantly reduces interfacial contact thermal resistance, ensuring that the heat absorbed by the cooling medium can be quickly conducted to the cavity interior. This is crucial for achieving the rapid cooling required for high rare-earth magnesium alloys.

[0046] It should be noted that the cooling pipe 9 is laid out in a horizontally extended manner, covering the main area of ​​the bottom surface of the ingot cavity 7. The outer wall of the cooling pipe 9 is fixedly connected to the outer wall of the ingot cavity 7 by full welding. The welding fit achieves low thermal resistance contact, effectively reducing the interface contact thermal resistance and improving the heat transfer efficiency.

[0047] To enhance the structural stability of the mold under high-temperature conditions, multiple reinforcing ribs 3 are provided on the inner and / or outer walls of the mold body. The multiple reinforcing ribs 3 are arranged sequentially and at intervals along the circumference of the mold body on the wall surface of the mold body, or the multiple reinforcing ribs 3 are arranged in a grid pattern.

[0048] As a preferred embodiment, the reinforcing ribs 3 are arranged circumferentially along the side wall of the mold body and integrally formed with the outer wall of the mold body. Multiple reinforcing ribs 3 form an array on the outer wall of the mold body. The reinforcing ribs 3 can offset the thermal deformation stress borne by the mold body during the filling and rapid cooling stages of the magnesium alloy melt, reduce the probability of mold body deformation and leakage, and improve the dimensional accuracy and stability of the mold during long-term use.

[0049] like Figure 1 As shown, as a preferred embodiment, the reinforcing rib 3 is a convex, arc-shaped solid structure, arranged in a circular array along the side wall of the mold body. This structural design effectively disperses the thermal deformation stress generated during the filling and rapid cooling of the magnesium alloy molten metal, preventing plastic deformation or cracking of the mold body. Preferably, the reinforcing rib 3 can also adopt any one of the following structures: arc-shaped, I-shaped, or T-shaped. For example, I-shaped or T-shaped reinforcing ribs have a higher moment of inertia for the same weight, making them suitable for the bending and torsional resistance design of large-size ingot molds; while arc-shaped reinforcing ribs have a lower stress concentration factor, making them more suitable for withstanding alternating thermal shock loads.

[0050] Regarding the interface configuration strategy, at least two cooling medium interfaces are located on the same side wall, adjacent side walls, or opposite side walls of the mold body. This invention typically employs an opposite side wall arrangement to facilitate uniform flow of the medium across the entire bottom of the cavity. In practical applications, the arrangement can be flexibly adjusted to be on the same side or adjacent, depending on the workshop piping layout.

[0051] Specifically, at least two cooling medium interface combinations form at least two cooling medium interface groups. Each cooling medium interface group contains two cooling medium interfaces. One of the at least two cooling medium interface groups serves as the working interface, connected to an external cooling water circulation system or compressed air system, while the others serve as backup interfaces. This redundancy design allows for rapid switching to backup interfaces to continue production when the main working interface becomes blocked or damaged, improving the operational reliability of the equipment. Alternatively, all cooling medium interface groups are connected to external cooling water circulation systems or compressed air systems, and all cooling medium interface groups are connected to cooling pipes 9, forming at least two cooling medium flow channels. These at least two cooling medium flow channels correspond to different areas of the ingot cavity 7. Through independent zone control, differentiated cooling can be implemented for areas with large differences in ingot wall thickness, further optimizing the uniformity of the solidification structure.

[0052] For details, please refer to the following document again. Figure 1 The device also includes a reinforcing outer support 6 and a bottom base 5. The reinforcing outer support 6 is located at both ends of the mold body. The mold body is detachably and fixedly connected to the reinforcing outer support 6 through locking connectors. The reinforcing outer support 6 is fixedly located on the top surface of the bottom base 5, and together with the bottom base 5, they form a rigid load-bearing frame.

[0053] like Figure 1 As shown, the reinforcing outer support 6 is welded to the bottom base 5 as a whole, providing a stable external support for the mold body. This rigid load-bearing frame can effectively constrain the elastic deformation and creep of the mold body during repeated rapid cooling and heating cycles, ensuring the long-term stability of the ingot's dimensional accuracy.

[0054] Typically, the bottom base 5 is a welded box-shaped steel structure located at the very bottom of the entire assembly. Preferably, the bottom base 5 has inclined support ribs welded into its inner cavity to enhance load-bearing rigidity. The bottom plate of the bottom base 5 has pre-drilled mounting holes for anchoring the entire mold assembly to the production floor using anchor bolts, preventing slippage or displacement of the mold during the casting process. The reinforcing outer support 6 is a rigid support frame structure, integrally welded and fixed to the top surface of the bottom base 5. The reinforcing outer support 6 is located at both ends of the mold body, and its structure matches the flange faces at the ends of the mold body. The reinforcing outer support 6 has pre-drilled bolt holes for engaging with fasteners 2 to lock the mold body in place.

[0055] Preferably, the locking connector includes any one of the following: high-strength bolts with flanges, quick clamps, clamp connectors, and hinge locking mechanisms. Typically, fastener 2 is a high-strength bolt with a flange, which is locked and fixed by pressing the flange faces at both ends of the mold body. This detachable connection method not only ensures the tightness of the connection but also facilitates subsequent disassembly of the mold body for maintenance operations such as descaling of cooling pipes and grinding of the inner wall of the cavity. Preferably, flange faces are provided at both ends of the mold body, and the mating structure of the reinforcing outer support 6 is adapted to the flange faces. The locking connector presses the flange faces to lock and fix the mold body and the reinforcing outer support 6.

[0056] In addition, a melt pouring opening is provided at the top of the mold body, and an end cap 8 is detachably and sealingly fitted at the melt pouring opening. The end cap 8 is used to seal the top of the cavity after pouring, preventing the melt from oxidizing and evaporating, and also preventing the cooling medium from accidentally seeping in. Preferably, a high-temperature resistant sealing gasket is provided between the contact surface of the end cap 8 and the top surface of the mold body. This sealing gasket needs to maintain good resilience and sealing performance in high-temperature environments. The gasket achieves sealing, on the one hand blocking the evaporation fumes of the melt and preventing environmental pollution, and on the other hand preventing the cooling medium from leaking from the top opening. Preferably, the high-temperature resistant sealing gasket is any one of graphite gaskets, ceramic fiber gaskets, high-temperature resistant silicone rubber sealing rings, and metal spiral wound gaskets. Specifically, graphite gaskets have good self-lubricating properties and are resistant to ultra-high temperatures, making them suitable for frequent opening and closing conditions; ceramic fiber gaskets have excellent thermal insulation properties, which can reduce heat loss from the end cap; high-temperature resistant silicone rubber sealing rings have good elasticity and are suitable for airtightness requirements in the medium and low temperature range; metal spiral wound gaskets have both high strength and heat resistance, making them suitable for reliable sealing in high-pressure water cooling mode. The availability of various materials ensures that the device maintains a stable sealing effect under different cooling modes and temperature ranges.

[0057] In a typical implementation, a cooling mode switching control method for magnesium alloy ingots is provided. This method employs the aforementioned magnesium alloy melt ingot mold device with switchable cooling modes. It should be noted that although the implementation of this method relies on the aforementioned hardware device, the focus of this invention is on achieving precise matching between the cooling process and material properties through specific control logic and timing arrangements. Specifically, the method includes the following steps: Step S100, Operating Condition Selection: Select the cooling mode according to the grade of the magnesium alloy to be cast and the target performance requirements; if rapid cooling is required to refine the grains, select the water cooling mode; if slow cooling is required to prevent hot cracking, select the air cooling mode.

[0058] Specifically, this step establishes a mapping relationship between material properties and process paths. For example, when producing high rare-earth magnesium alloys such as Mg-Gd-Y-Zr series, due to their high alloy element content and large undercooling requirements, extremely high cooling rates are necessary to suppress coarse second-phase precipitation and refine grains; therefore, water cooling is chosen. However, when producing commercial magnesium alloys such as AZ31B and ZM5, these alloys are highly sensitive to hot cracking, and excessively rapid cooling can lead to large temperature differences between the inside and outside of the ingot, generating significant thermal stress; therefore, air cooling is chosen to reduce the temperature gradient. This pre-decision-making based on the metallurgical characteristics of the material avoids the problems of coarse grains or cracking and scrapping caused by mismatched cooling modes in traditional production.

[0059] Step S200, Piping connection: According to the selected cooling mode, connect the cooling medium interface to the cooling water circulation system or compressed air system.

[0060] Specifically, this is a physical switching operation that must be completed before molten metal pouring. If water cooling mode is selected in step S100, the operator needs to connect the first cooling medium interface 1 to the circulating cooling water supply pipeline and the second cooling medium interface 4 to the return water pipeline, and check the status of the water circuit valves. If air cooling mode is selected, the first cooling medium interface 1 needs to be connected to a compressed air supply pipeline, the second cooling medium interface 4 needs to be connected to an exhaust pipeline, and the air circuit pressure regulating valve needs to be set within a safe range. Emphasizing the time priority of this step is crucial, because switching pipelines after the high-temperature molten metal is poured is not only difficult to operate, but also highly likely to cause the risk of water-vapor mixing explosion or ingot defects due to media interruption. Through standardized interface configuration, this physical switching process is fast and error-proof, ensuring production safety and process stability.

[0061] Step S300, Melt casting: Molten magnesium alloy is poured into the ingot cavity, and the top opening of the ingot cavity is sealed after casting is completed.

[0062] Specifically, after completing the pipeline connection and confirming that everything is correct, the end cap 8 is opened, and the magnesium alloy molten material at the predetermined temperature is injected into the ingot cavity 7. After pouring, the end cap 8 is immediately closed and locked with fasteners, pressing the high-temperature resistant sealing gasket tightly against the mating surface. This sealing operation has a dual function: on the one hand, it isolates air to prevent the magnesium alloy molten material from oxidizing and burning at high temperatures; on the other hand, it creates a closed heat exchange environment, preventing subsequent cooling media (especially high-pressure gas) from leaking from the top, ensuring that the cooling medium can flow stably in the cooling pipeline 9 according to the preset flow path, and maintaining constant heat exchange boundary conditions.

[0063] Step S400, Cooling and Solidification: Start the supply of the corresponding cooling medium, so that the cooling medium flows in the cooling pipe to cool the magnesium alloy melt in the ingot cavity until the melt is completely solidified and formed.

[0064] Specifically, according to the selection in step S100, either the circulating water pump or the air compressor is turned on. In water-cooling mode, liquid cooling water flows at high speed and turbulently within the cooling pipe 9, utilizing its high specific heat capacity and high convective heat transfer coefficient to rapidly remove the latent heat of solidification of the melt, achieving an extremely rapid cooling rate of no less than 7°C / s, driving a significant increase in grain nucleation rate. In air-cooling mode, compressed air flows within the pipe, utilizing the lower convective heat transfer coefficient of the gas to achieve gentle heat dissipation, allowing the melt to solidify slowly at a controlled low rate, thereby releasing thermal stress and preventing crack initiation. The entire cooling process continues until the temperature at the center of the ingot drops below the solidus line and it possesses sufficient demolding strength.

[0065] Step S500, Demolding and Maintenance: After the ingot has completely cooled, disassemble fastener 2, separate the mold body from the reinforcing outer support 6, and remove the formed ingot. Periodically loosen the fasteners to disassemble the mold body, and perform scale blowing and slag removal maintenance on the cooling pipes and the inner wall of the cavity.

[0066] Through the above closed-loop control, the present invention has successfully achieved differentiated solidification control for different magnesium alloy grades on the same set of molds, fundamentally solving the technical problem of the difficulty in simultaneously achieving fine grain preparation and hot crack prevention.

[0067] Example 1 This embodiment provides a specific application example of water cooling mode in the production of high rare earth magnesium alloy ingots. The magnesium alloy is a high rare earth magnesium alloy with a rare earth content greater than 10 wt.%. The cooling medium interface is connected to the cooling water circulation system, and the magnesium alloy melt in the ingot cavity is cooled in water cooling mode.

[0068] Specifically, high-rare-earth magnesium alloys (such as the Mg-Gd-Y-Zr system) are prone to forming coarse second phases and dendritic segregation under slow cooling conditions due to their high alloy element content and wide solidification temperature range. Therefore, extremely high cooling rates are necessary to achieve sufficient undercooling to drive a large number of heterogeneous nucleations, thereby refining the grains. Preferably, in water-cooling mode, the cooling water temperature is 18℃~22℃, and the cooling rate of the magnesium alloy melt is not less than 7℃ / s.

[0069] The following section uses the production of Mg-Gd-Y-Zr series high rare earth magnesium alloy ingots as an example to illustrate the complete operation process and technical effects of this embodiment.

[0070] First, prepare the equipment and switch operating conditions. Securely anchor the bottom base 5 to the production station floor using anchor bolts to prevent mold displacement or vibration during casting. Based on the selected operating conditions, connect the first cooling medium interface 1 to the circulating cooling water supply pipeline and precisely control the supply water temperature within the range of 20±2℃. Simultaneously, connect the second cooling medium interface 4 to the return water pipeline and start the circulating water pump to pre-circulate the cooling water in the pipeline, expel air from the pipe, and stabilize the flow field.

[0071] Subsequently, molten Mg-Gd-Y-Zr alloy molten metal at a temperature of 730-740℃ is poured steadily into the ingot cavity 7. After pouring, the end cap 8 is immediately closed and locked with fasteners 2 to create a sealed cooling environment.

[0072] Next, the water cooling circulation is started for cooling and solidification. The cooling water flows at high speed and turbulently in the cooling pipe 9, and efficiently removes the heat of the melt through the low thermal resistance interface formed by full welding. The measured cooling rate of the melt in the ingot cavity 7 can reach more than 7℃ / s.

[0073] After the ingot has completely solidified and cooled to a safe demolding temperature, disassemble fastener 2, separate the mold body from the reinforcing outer support 6, and remove the formed ingot.

[0074] Testing revealed that the Mg-Gd-Y-Zr magnesium alloy ingots produced using the water-cooling method of this embodiment exhibited significantly refined average grain size, dense and uniform microstructure, and a dispersed second phase. Their mechanical properties fully met the stringent requirements of high-rare-earth magnesium alloys for fine-grained microstructure.

[0075] It should be understood that although this embodiment uses Mg-Gd-Y-Zr alloy as an example, other high rare earth magnesium alloy systems with a rare earth content greater than 10 wt.% (such as Mg-Y-Nd-Zr, Mg-Gd-Dy-Zr, etc.) can be produced by referring to the water cooling process window of this embodiment, as long as their solidification characteristics are sensitive to the cooling rate and require rapid cooling to refine the grains. This is all within the protection scope of this invention.

[0076] Example 2 This embodiment provides a specific application example of an air-cooling mode for the production of AZ-series and ZM-series commercial magnesium alloy ingots. The magnesium alloy is an AZ-series or ZM-series commercial magnesium alloy. The cooling medium interface is connected to the compressed air system, and the magnesium alloy melt in the ingot cavity is cooled in an air-cooling mode.

[0077] Specifically, while AZ-based (such as AZ31B and AZ61) and ZM-based (such as ZM5 and ZM6) commercial magnesium alloys possess good casting process performance and mechanical properties, they have a wide solidification temperature range and high susceptibility to hot cracking. Unlike the high-rare-earth magnesium alloys in Example 1, which pursue extremely rapid cooling, these commercial alloys, if cooled too quickly during solidification, will form a huge temperature gradient between the ingot surface and the core. The resulting thermal stress can easily exceed the material's strength limit at high temperatures, leading to hot cracking defects. Therefore, for these alloys, the core of the process lies in "slow cooling and temperature control" rather than "extremely rapid quenching." Preferably, in the air-cooling mode, the compressed air pressure is 0.4 MPa to 0.6 MPa.

[0078] The following section uses the production of AZ31B commercial magnesium alloy ingots as an example to provide a detailed explanation of the complete operation process and technical effects of this embodiment.

[0079] First, prepare the equipment and switch the operating conditions, confirming that the mold device is securely installed on the bottom base 5. Based on the selected operating conditions, connect the first cooling medium interface 1 to the compressed air supply line and install a precision pressure regulating valve on the line to accurately adjust the air supply pressure to the range of 0.4-0.6MPa; at the same time, connect the second cooling medium interface 4 to the exhaust line to ensure smooth exhaust without back pressure accumulation, thereby switching the device to the air-cooled slow cooling mode.

[0080] Subsequently, molten AZ31B magnesium alloy at a temperature of 680-700℃ is poured steadily into the ingot cavity 7. This pouring temperature is slightly lower than that of the high rare earth alloy in Example 1 to accommodate the liquidus temperature of AZ31B and reduce the tendency for oxidation due to overheating. After pouring, the end cap 8 is immediately closed and locked with fasteners 2 to create a sealed air-cooled heat exchange environment.

[0081] Next, compressed air supply is activated for cooling and solidification. The compressed air flows at a stable velocity in cooling pipe 9, gently carrying away the heat from the melt by utilizing the gas's low convective heat transfer coefficient. During this process, the temperature field distribution within the ingot cavity 7 is relatively uniform, the solidification front advances slowly, and the measured cooling rate is controlled within a suitable low-speed range, allowing the thermal stress inside the ingot to be fully relaxed and released.

[0082] After the ingot has completely solidified and cooled to a safe demolding temperature, disassemble fastener 2, separate the mold body from the reinforcing outer support 6, and remove the formed ingot.

[0083] Testing revealed that the AZ31B magnesium alloy ingot produced using the air-cooling method in this embodiment has a high surface finish, intact edges and corners without defects, and no hot cracks were found during internal flaw detection. The yield of finished products has been greatly improved, fully meeting the processing and usage requirements of commercial magnesium alloy components.

[0084] It should be understood that although this embodiment uses AZ31B alloy as an example, other AZ-series (such as AZ61, AZ80) or ZM-series (such as ZM5, ZM6) commercial magnesium alloys can be produced by referring to the air-cooling process window of this embodiment, as long as they have similar hot cracking sensitivity and slow cooling requirements. This is all within the protection scope of this invention.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0086] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A magnesium alloy melt casting ingot mold device with switchable cooling modes, characterized in that, include: A mold body with an ingot cavity inside, the inner wall and / or outer wall of the mold body are provided with multiple reinforcing ribs, the multiple reinforcing ribs are arranged sequentially and spaced apart along the circumference of the mold body on the wall surface of the mold body, or the multiple reinforcing ribs are arranged in a grid pattern; The mold includes cooling pipes and at least two cooling medium interfaces. The cooling pipes are arranged to fit the outer wall of the ingot cavity, and the at least two cooling medium interfaces are located on the side wall of the mold body and are respectively connected to both ends of the cooling pipes to form a cooling medium flow channel for the cooling medium to flow. The cooling medium interfaces are used to selectively connect to an external cooling water circulation system or a compressed air system, so that cooling water or compressed air can flow selectively in the cooling pipes, thereby switching between water cooling mode and air cooling mode within the mold body.

2. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1, characterized in that: The cooling pipes extend along the bottom outer wall and / or side outer wall of the ingot cavity to form a single-sided cooling structure or a surrounding cooling structure. Preferably, the cross-sectional shape of the cooling pipe is any one of a circle, a rectangle, or an ellipse.

3. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1 or 2, characterized in that: The outer wall of the cooling pipe is fixed to the outer wall of the ingot cavity by welding, forming a low thermal resistance contact interface.

4. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1 or 2, characterized in that: At least two cooling medium interfaces are provided on the same side wall, adjacent two side walls, or opposite two side walls of the mold body; Preferably, at least two cooling medium interfaces are configured to form at least two cooling medium interface groups, each cooling medium interface group comprising two cooling medium interfaces, one of the at least two cooling medium interface groups serving as a working interface connected to a cooling water circulation system or a compressed air system, and the others serving as backup interfaces. Alternatively, all cooling medium interface groups are externally connected to a cooling water circulation system or a compressed air system, and all cooling medium interface groups are respectively connected to the cooling pipeline to form at least two cooling medium flow channels, with the at least two cooling medium flow channels corresponding to different areas of the ingot cavity.

5. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1, characterized in that: The reinforcing rib can be any one of the following: arc-shaped structure, I-shaped structure, or T-shaped structure.

6. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1, characterized in that, Also includes: Reinforce the external support frame and the bottom base; The reinforcing outer brackets are disposed at both ends of the mold body, and the mold body is detachably and fixedly connected to the reinforcing outer brackets through locking connectors; The reinforcing external support is fixedly installed on the top surface of the bottom base, and together with the bottom base, they form a rigid load-bearing frame; Preferably, the locking connector includes any one of the following: a high-strength bolt with a flange, a quick clamp, a clamp connector, or a hinge locking mechanism; Preferably, the mold body has flange faces at both ends, the mating structure of the reinforcing outer bracket is adapted to the flange faces, and the locking connector presses the flange faces to lock and fix the mold body and the reinforcing outer bracket.

7. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 1, characterized in that: The top of the mold body is provided with a melt pouring opening, and an end cap is detachably and sealingly fitted at the melt pouring opening. Preferably, a high-temperature resistant sealing gasket is provided between the mating surfaces of the end cap and the top surface of the mold body; Preferably, the high-temperature resistant sealing gasket is any one of graphite gasket, ceramic fiber gasket, high-temperature resistant silicone rubber sealing ring, and metal spiral wound gasket.

8. A method for controlling the switching of cooling modes of magnesium alloy ingots, characterized in that, The magnesium alloy melt casting mold apparatus with switchable cooling mode according to any one of claims 1-7 includes the following steps: Operating condition selection: Select the cooling mode according to the grade of the magnesium alloy to be cast and the target performance requirements; if rapid cooling is required to refine the grains, select the water cooling mode; if slow cooling is required to prevent hot cracking, select the air cooling mode. Piping connection: According to the selected cooling mode, connect the cooling medium interface to the corresponding cooling water circulation system or compressed air system; Molten casting: Molten magnesium alloy is poured into the ingot cavity, and the top opening of the ingot cavity is sealed after casting is completed; Cooling and solidification: Start the supply of the corresponding cooling medium, so that the cooling medium flows in the cooling pipe to cool the magnesium alloy melt in the ingot cavity until the melt is completely solidified and formed.

9. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 8, characterized in that: The magnesium alloy is a high rare earth magnesium alloy with a rare earth content greater than 10 wt.%. The cooling medium interface is connected to the cooling water circulation system, and the magnesium alloy melt in the ingot cavity is cooled in water cooling mode. Preferably, in the water-cooling mode, the cooling water temperature is 18℃~22℃, and the cooling rate of the magnesium alloy melt is not less than 7℃ / s.

10. The magnesium alloy melt casting mold device with switchable cooling mode according to claim 8, characterized in that: The magnesium alloy is a commercial magnesium alloy of the AZ series and ZM series. The cooling medium interface is connected to the compressed air system and the magnesium alloy melt in the ingot cavity is cooled in the air cooling mode. Preferably, in the air-cooling mode, the compressed air pressure is 0.4 MPa ~ 0.6 MPa.

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