Highly efficient cooling method and device using micro-holes inside multi-pass frozen sand molds

Abstract

The present invention discloses a highly efficient cooling method and device for multi-pass internal micropores of frozen sand mold, which comprises a frozen sand mold molding chamber, an electric lifting platform, a Teflon porous liner, a removable porous aluminum plate, a cooling device box for frozen sand mold, a sealed cover plate, an ultrasonic piezoelectric sheet, a U-shaped condenser tube, an ultrasonic generator and a low-temperature cooling system. The Teflon liner and the removable porous aluminum plate are provided with through-hole structures of the same size and shape, which are used for rapid cooling from the surface to the core of the molding sand. The lifting platform is started, and the bumpy-type Teflon liner rises to the highest point, making it easy to demold. The high and low frequency double modes of the ultrasonic piezoelectric sheet can not only vibrate the frozen sand mold to solidify it densely, but also assist in cutting molding. The adoption of this device can realize rapid freezing of the frozen sand mold, and facilitate demolding and low-cost digital molding.

Description

[Technical Field]

[0001] The present invention relates to the field of green casting of frozen sand molds, and more particularly to a highly efficient cooling method and device for multi-pass internal micro-holes of frozen sand molds. [Background technology]

[0002] The traditional foundry industry consumes a lot of resources and requires sand molds to be replicated using wooden or metal molds to produce casting molds. Sand casting faces issues such as a long production cycle, multiple production steps, high labor intensity, high development costs for finished products, and poor operating environments. The traditional foundry industry urgently needs to break through and transform its processes to greener, promoting energy savings, emissions reduction, and green, sustainable development in the manufacturing industry. The adoption of green casting processes and equipment can reduce material and energy waste during the casting process, reduce waste emissions, lower the reject rate, improve the yield rate, and achieve efficient, high-quality, and accurate casting, thereby realizing green casting production. Summary of the Invention [Problem to be solved by the invention]

[0003] The digitalized frozen sand mold green casting technology uses water as an adhesive, allowing for the adhesion of foundry sand at low temperatures and the digital cutting / printing of sand molds, resulting in high-quality castings. The principle is to use a 3D CAD model of the sand mold to directly fabricate the frozen sand mold (core) using a printing nozzle / milling cutter. After surface treatment and assembly, the resulting sand mold is ready for casting. Before the frozen sand mold is cut, it is important to ensure that the strength and hardness of the resulting frozen sand blank meets the requirements for efficient digital cutting. The strength and hardness of a frozen sand blank depend on the water content, freezing temperature, and sand grain mesh size. With existing equipment, large frozen sand blanks face long freezing times, high costs, and difficult demolding issues. Therefore, new methods and equipment are urgently needed to rapidly freeze frozen sand molds, facilitating demolding and cost-effective molding. [Means for solving the problem]

[0004] To solve the above problems, the present invention discloses a highly efficient cooling method and device for a multi-pass frozen sand mold using internal micropores. This device mainly solves the problems of pre-mixed wet foundry sand having low freezing efficiency, low density, and difficulty in demolding during the blank manufacturing process.

[0005] A highly efficient cooling device using multi-pass internal micropores for frozen sand molds, comprising a frozen sand mold molding chamber, an electric lifting platform, a frozen sand mold cooling device box, an ultrasonic generator and a low-temperature cooling system, wherein the frozen sand mold molding chamber is located in the frozen sand mold cooling device box and its bottom is attached to the electric lifting platform, the frozen sand mold molding chamber is composed of the Teflon porous liner and the removable porous aluminum plate, and the ultrasonic piezoelectric sheet is located between the removable porous aluminum plate and the Teflon porous liner.

[0006] The removable porous aluminum plate is located outside the Teflon porous liner, and the ultrasonic piezoelectric sheet is connected by wires to an ultrasonic generator located outside the cooling device box of the frozen sand mold.

[0007] The cryogenic cooling system includes a U-shaped condenser pipe, a liquid nitrogen tank, a nitrogen gas tank, a flow meter, a check valve, and a cryogenic gas mixing cavity. The U-shaped condenser pipe is located in the frozen sand mold cooling device box. The liquid nitrogen tank is connected to the cryogenic gas mixing cavity through a first pipeline, which is equipped with a check valve. The nitrogen gas tank is connected to the cryogenic gas mixing cavity through a second pipeline, which is equipped with a flow meter and a check valve. The cryogenic gas mixing cavity is connected to the U-shaped condenser pipe. External cryogenic gas is connected to the U-shaped condenser pipe through a cryogenic-resistant pipeline to rapidly cool the frozen sand mold molding chamber 1.

[0008] The Teflon porous liner and removable porous aluminum plate have through-holes of the same size and position, which can ensure that cold air can enter the frozen sand mold after assembly. The Teflon porous liner is made up of four Teflon molds joined together, and the joints of the Teflon molds are designed in a "box" shape. When the core of the frozen sand mold reaches a preset temperature, the lifting platform can be activated to facilitate demolding of the frozen sand mold. After the frozen sand mold is removed, it can be placed in a digital molding machine for milling.

[0009] A highly efficient cooling method for frozen sand molds using multi-pass internal micropores, which is used to assist the rapid freezing and cutting process of frozen sand molds made of various materials (such as quartz sand, zircon sand, and chromite sand), and the specific implementation steps are as follows: S1, selecting appropriate molding sand according to the characteristics of the casting, weighing out 3% to 8% by mass of water, putting it into a sand mixer, and uniformly stirring for 2 to 10 minutes to produce wet molding sand containing water; S2, the electric lifting platform is started, the frozen sand mold molding chamber is at its upper limit position, the produced wet foundry sand particles are spread into the frozen sand mold molding chamber, the ultrasonic generator is started and the low frequency range is selected to vibrate the sand mold to make it dense and compact, the iron wire is inserted along the through holes of the Teflon porous liner, and the frozen sand blank has a regular arrangement of exhaust holes, and the electric lifting platform is started again, the frozen sand mold molding chamber is at its lower limit position; S3: start the low-temperature cooling system, the low-temperature gas and nitrogen gas form a low-temperature mixed gas through the check valve, the low-temperature mixed gas is transported to the condenser pipe circuit through the pressure control valve and circulated and cooled, and then passes through the Teflon porous liner and the through-holes of the removable porous aluminum plate and quickly enters the core of the sand mold to freeze the frozen sand blank; In S4, when the temperature inside the frozen sand mold reaches a preset temperature, the sealing cover plate is opened, and the electric lifting platform is activated to remove the frozen sand mold; alternatively, the entire frozen sand mold making device is placed on the digital molding machine platform to perform digital cutting molding, ensuring that the strength and hardness of the frozen sand mold meets efficient cutting molding requirements; when the core of the frozen sand mold reaches a preset temperature, the lifting platform is activated to facilitate demolding of the frozen sand mold; after the frozen sand mold is removed, milling can be performed on the digital molding machine.

[0010] Furthermore, the through-holes in the Teflon porous liner and the removable porous aluminum plate are designed in regular arrangements of "square," "hexagonal lattice," "rice-shaped," and "circular" based on fluent flow field simulation, which accelerates the convective heat exchange of the low-temperature gas and improves the cooling efficiency of the sand mold.

[0011] Furthermore, a sealed cover plate for heat insulation is provided above the cooling device box of the frozen sand mold and the molding chamber of the frozen sand mold, and a film is attached to the inner wall of the sealed cover plate. The film is made of one of EVA plastic film, LDPE (low-density polyethylene film), or polyesteramine fiber, which are used to keep the moisture in the frozen sand mold.

[0012] Furthermore, the ultrasonic generator can be set to two modes: low frequency and high frequency. In the high frequency mode, the ultrasonic piezoelectric sheet transmits vibrations to ensure dense solidification in the frozen sand mold molding process, preventing defects from occurring inside the frozen sand mold. In the low frequency mode, the entire frozen sand mold molding die is placed in the digital molding machine to realize the function of ultrasonic milling of the frozen sand mold.

[0013] Furthermore, when the low-temperature cooling system is put into operation, the liquid nitrogen tank is first opened to discharge the air inside the pipeline. After a certain period of time, the temperature in the space inside the pipeline drops, and liquid nitrogen is transported into the pipeline in liquid form. Next, the nitrogen gas tank is opened, and the nitrogen gas flow meter is adjusted to allow nitrogen gas to enter the gas-liquid mixing cavity at a certain flow rate to mix with the liquid nitrogen. Utilizing the low-temperature properties of liquid nitrogen, the nitrogen gas exchanges heat with the liquid nitrogen, finally forming low-temperature nitrogen gas, which is finally transported through the heat-insulating pipeline to the condenser tube inside the device to cool the frozen sand mold.

[0014] The liquid nitrogen tank is replaced with compressed low-temperature air or low-temperature CO2 gas, and different low-temperature gases have different temperature ranges, so that molding sands with different thermal conductivity all have high refrigeration efficiency. [Effects of the Invention]

[0015] The beneficial effects of the present invention are as follows: (1) This technical solution uses built-in ventilation holes and an external low-temperature cooling system in the frozen sand mold to freeze the pre-mixed wet foundry sand at a low temperature, thereby achieving the purpose of rapid cooling of the frozen sand mold, saving energy consumption and improving economic benefits.

[0016] (2) The ultrasonic piezoelectric sheet can vibrate the sand mold during the molding process to solidify it densely. It also uses ultrasonic waves to assist cutting during the digital molding process, effectively reducing the cutting temperature and improving the processing quality, while extending the usage time of the cutting head and reducing some costs. [Brief explanation of the drawings]

[0017] [Figure 1] This is a principle diagram of a highly efficient cooling device using micropores inside the multi-pass of a frozen sand mold. [Figure 2] 1 is a structural schematic diagram of a Teflon liner of the present invention. [Figure 3] 3A and 3B are schematic diagrams of the structure of the ventilation hole of the present invention, in which FIG. 3A is a square, FIG. 3B is a hexagonal lattice, FIG. 3C is a cross-section, and FIG. 3D is a circle. [Figure 4] 1 is a structural schematic diagram of a low-temperature cooling system of the present invention; [Figure 5] FIG. 3 is an enlarged view of a portion A in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be further described below with reference to the drawings and specific embodiments, but it should be understood that the specific embodiments below are for the purpose of explaining the present invention and do not limit the scope of the present invention. Note that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0019] As shown in Figure 1, this is a highly efficient cooling device for frozen sand molds using multi-pass internal micropores, and includes a frozen sand mold molding chamber 1, an electric lifting platform 2, a frozen sand mold cooling device box 5, an ultrasonic generator 9, and a low-temperature cooling system 10. The frozen sand mold molding chamber 1 is located in the frozen sand mold cooling device box 5, and its bottom is attached to the electric lifting platform 2. The frozen sand mold molding chamber 1 is composed of the Teflon porous liner 3 and the removable porous aluminum plate 4, and the ultrasonic piezoelectric sheet 7 is located between the Teflon porous liner 3 and the removable porous aluminum plate 4 and fixed to the bottom of the Teflon porous liner 3.

[0020] The removable porous aluminum plate 4 is located outside the Teflon porous liner 3, and the ultrasonic piezoelectric sheet 7 is connected by a wire to an ultrasonic generator 9 located outside the cooling device box 5 of the frozen sand mold.

[0021] The low-temperature cooling system 10 includes a U-shaped condenser pipe 8, a liquid nitrogen tank 11, a nitrogen gas tank 12, a flow meter 13, a check valve 14, and a low-temperature gas mixing cavity 15. The U-shaped condenser pipe 8 is located in the frozen sand mold cooling device box 5. The liquid nitrogen tank 11 is connected to the low-temperature gas mixing cavity 15 through a first pipeline, and the first pipeline is equipped with a check valve 14. The nitrogen gas tank 12 is connected to the low-temperature gas mixing cavity 15 through a second pipeline, and the second pipeline is equipped with a flow meter 13 and a check valve 14 in order. The low-temperature gas mixing cavity 15 is connected to the U-shaped condenser pipe 8 through a pressure regulating valve and a low-temperature pipeline.

[0022] The Teflon porous liner 3 and the removable porous aluminum plate 4 are provided with through-holes of the same size and position, which can ensure that cold air can enter the inside of the freezing sand mold through the through-holes after assembly.

[0023] As shown in FIGS. 2 and 5, the Teflon porous liner 3 is made by joining four Teflon molds, and the joints of the Teflon molds are designed in a "box" shape.

[0024] A highly efficient cooling method for multi-pass internal micro-holes of frozen sand molds, which is applied to assist the rapid freezing and cutting process of frozen sand molds, and the specific implementation steps are as follows: S1, selecting appropriate molding sand according to the characteristics of the casting, weighing out 3% to 8% by mass of water, putting it into a sand mixer, and uniformly stirring for 2 to 10 minutes to produce wet molding sand containing water; S2, start the electric lifting platform, the frozen sand mold molding chamber is at the upper limit position, the produced wet casting sand particles are spread into the frozen sand mold molding chamber, start the ultrasonic generator and select the low frequency range to vibrate the sand mold to make it compact, the ultrasonic generator has two modes: low frequency and high frequency, in the high frequency mode, the ultrasonic piezoelectric sheet transmits vibration to make the frozen sand mold compact and prevent defects inside the frozen sand mold, in the low frequency mode, the whole frozen sand mold is placed on the digital molding machine to realize the ultrasonic milling function of the frozen sand mold, Insert the iron wire along the through holes of the Teflon porous liner to form a regular arrangement of exhaust holes in the frozen sand blank. Then start the electric lifting platform again, and the frozen sand molding chamber will be at the lowest position. S3: start the low-temperature cooling system, the low-temperature gas and nitrogen gas form a low-temperature mixed gas through the check valve, the low-temperature mixed gas is transported to the condenser pipe circuit through the pressure control valve and circulated and cooled, and then passes through the Teflon porous liner and the through-holes of the removable porous aluminum plate and quickly enters the core of the sand mold to freeze the frozen sand blank; When the low-temperature cooling system is put into operation, the liquid nitrogen tank is first opened to discharge the air inside the pipeline. After a certain period of time, the temperature in the pipeline decreases, and liquid nitrogen is transported into the pipeline in liquid form. Next, the nitrogen gas tank is opened, and the nitrogen gas flow meter is adjusted to allow nitrogen gas to enter the gas-liquid mixing cavity at a certain flow rate to mix with the liquid nitrogen. Utilizing the low-temperature properties of liquid nitrogen, the nitrogen gas exchanges heat with the liquid nitrogen, finally forming low-temperature nitrogen gas at a certain temperature. This gas is then transported through the heat-insulating pipeline to the condenser tube inside the device to cool the frozen sand mold.

[0025] The liquid nitrogen tank is replaced with compressed low-temperature air or low-temperature CO2 gas, and different low-temperature gases have different temperature ranges, so that molding sands with different thermal conductivity all have high refrigeration efficiency.

[0026] In S4, when the temperature inside the frozen sand mold reaches a preset temperature, the sealing cover plate is opened, and the electric lifting platform is activated to remove the frozen sand mold; alternatively, the entire frozen sand mold making device is placed on the digital molding machine platform to perform digital cutting and molding, ensuring that the strength and hardness of the frozen sand mold meets efficient cutting and molding requirements; when the core of the frozen sand mold reaches a preset temperature, the lifting platform is activated to facilitate demolding of the frozen sand mold; and after the frozen sand mold is removed, it can be placed on the digital molding machine for milling.

[0027] As shown in Figure 3, the through-holes in the Teflon porous liner and the removable porous aluminum plate are designed in regular arrangements of "square," "hexagonal lattice," "rice-shaped," and "circular" based on fluent flow field simulation, which accelerates the convective heat exchange of the low-temperature gas and improves the cooling efficiency of the sand mold.

[0028] A sealing cover plate 6 is provided above the cooling device box for the frozen sand mold and the molding chamber for the frozen sand mold to provide heat insulation. A film is attached to the inner wall of the sealing cover plate, and the film is made of one of EVA plastic film, LDPE (low-density polyethylene film), or polyesteramine fiber, which is used to keep the moisture in the frozen sand mold.

[0029] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions configured by any combination of the above technical features. [Explanation of symbols]

[0030] 1...Frozen sand molding room 2. Electric lifting platform 3. Teflon liner 4. Removable porous aluminum plate 5. Refrigeration box for frozen sand molds 6...Sealing lid plate 7. Ultrasonic piezoelectric sheet 8. U-shaped condenser tube 9. Ultrasonic generator 10. Low-temperature cooling system 11. Liquid nitrogen tank 12. Nitrogen gas tank 13...flow meter 14. Check valve 15. Low-temperature gas mixing cavity

Claims

1. A highly efficient cooling device having a structure in which cooling gas is circulated through a plurality of fine cooling through-holes formed inside a freezing sand mold, The system includes a frozen sand mold molding chamber (1), an electric lifting platform (2), a frozen sand mold cooling device box (5), an ultrasonic generator (9) and a low-temperature cooling system (10), The frozen sand mold molding chamber (1) is located in a frozen sand mold cooling device box (5), and its bottom is attached to the electric lifting platform (2). The frozen sand mold molding chamber (1) is composed of a polytetrafluoroethylene (PTFE) porous liner (3) and a removable porous aluminum plate (4). An ultrasonic piezoelectric sheet (7) is located between the PTFE porous liner (3) and the removable porous aluminum plate (4) and is fixed to the bottom of the PTFE porous liner (3).

2. 2. The high-efficiency cooling device according to claim 1, wherein the removable porous aluminum plate (4) is located outside the PTFE porous liner (3), and the ultrasonic piezoelectric sheet (7) is connected by a lead wire to an ultrasonic generator (9) located outside the cooling device box (5).

3. 2. The high-efficiency cooling device of claim 1, wherein the low-temperature cooling system (10) comprises a U-shaped condenser pipe (8), a liquid nitrogen tank (11), a nitrogen gas tank (12), a flow meter (13), a check valve (14), and a low-temperature gas mixing cavity (15), the U-shaped condenser pipe (8) is located in the frozen sand mold cooling device box (5), the liquid nitrogen tank (11) is connected to the low-temperature gas mixing cavity (15) through a first pipeline, the first pipeline being provided with a check valve (14), the nitrogen gas tank (12) is connected to the low-temperature gas mixing cavity (15) through a second pipeline, the second pipeline being provided with a flow meter (13) and a check valve (14), and the low-temperature gas mixing cavity (15) is connected to the U-shaped condenser pipe (8) through a pressure regulating valve and a low-temperature pipeline.

4. The PTFE porous liner (3) and the removable porous aluminum plate (4) are provided with through-holes of the same size and position, and after assembly, it is possible to ensure that cold air enters the inside of the freezing sand mold through the through-holes. The PTFE porous liner (3) is made by connecting four PTFE molds.

2. The high-efficiency cooling device according to claim 1, wherein the joint of the PTFE mold is designed in a "box" shape.

5. A highly efficient cooling method, comprising: The high-efficiency cooling device as claimed in claim 1 is used for manufacturing, and the method is applied to the rapid freezing and auxiliary cutting process of frozen sand molds, and its specific implementation steps are as follows: S1: Selecting appropriate molding sand according to the characteristics of a casting, weighing out 3% to 8% by mass of water, putting the water into a sand mixer, and uniformly stirring for 2 to 10 minutes to produce wet molding sand containing water; S2, the electric lifting platform is started, the frozen sand mold molding chamber is at its upper limit position, the produced wet foundry sand particles are spread into the frozen sand mold molding chamber, the ultrasonic generator is started and a low frequency range is selected to vibrate the sand mold to compact it, iron wires are inserted along the through holes of the PTFE porous liner, and the frozen sand blank has a regular arrangement of exhaust holes, and the electric lifting platform is started again, the frozen sand mold molding chamber is at its lower limit position; S3: starting the low-temperature cooling system, the low-temperature gas and nitrogen gas form a low-temperature mixed gas through a check valve, the low-temperature mixed gas is transported to the condenser pipe circuit through a pressure control valve and circulated and cooled, and then passes through the PTFE porous liner and the through-holes of the removable porous aluminum plate and quickly enters the core of the sand mold to freeze the frozen sand blank; S4: When the temperature inside the frozen sand mold reaches a preset temperature, the sealing cover plate is opened, and the electric lifting platform is activated to remove the frozen sand mold; alternatively, the entire frozen sand mold making device is placed on the digital molding machine platform to perform digital cutting molding, ensuring that the strength and hardness of the frozen sand mold meets the efficient cutting molding; when the core part of the frozen sand mold reaches a preset temperature, the lifting platform is activated to facilitate demolding of the frozen sand mold; and after the frozen sand mold is removed, it can be placed on the digital molding machine for milling.

6. The highly efficient cooling method of claim 5, wherein the through-holes in the PTFE porous liner and the removable porous aluminum plate are designed in a regular arrangement of "square", "hexagonal lattice", "Rectangular" and "circular" through simulation based on fluent flow field, to accelerate the convective heat exchange of the low-temperature gas and improve the cooling efficiency of the sand mold.

7. 6. The highly efficient cooling method according to claim 5, wherein a sealing cover plate (6) for heat insulation is provided above the cooling device box (5) of the frozen sand mold and the molding chamber of the frozen sand mold, and a film is attached to the inner wall of the sealing cover plate, and the film is made of one of EVA plastic film, LDPE (low-density polyethylene film), and polyesteramine fiber, which are used to keep the moisture in the frozen sand mold.

8. The high-efficiency cooling method according to claim 5, characterized in that the ultrasonic generator has two modes, namely, low frequency and high frequency, and in the high frequency mode, the ultrasonic piezoelectric sheet transmits vibrations to ensure dense solidification in the frozen sand mold forming process and prevent defects from occurring inside the frozen sand mold; and in the low frequency mode, the entire frozen sand mold is placed in the digital molding machine to realize the ultrasonic milling function of the frozen sand mold.

9. 10. The highly efficient cooling method of claim 5, wherein when the low-temperature cooling system is operated, the liquid nitrogen tank is first opened to exhaust the air inside the pipeline, and the temperature in the space inside the pipeline is reduced for a certain period of time, and liquid nitrogen is transported into the pipeline in liquid form, and then the nitrogen gas tank is opened and the nitrogen gas flow meter is adjusted to allow the nitrogen gas to enter the gas-liquid mixing cavity and mix with the liquid nitrogen, and by utilizing the low-temperature properties of the liquid nitrogen, the nitrogen gas exchanges heat with the liquid nitrogen, and finally forms low-temperature nitrogen gas, which is finally transported to the condenser tube inside the device through the heat-insulating pipeline to cool the frozen sand mold.

10. The liquid nitrogen tank is filled with compressed cryogenic air or cryogenic CO ２ 10. The highly efficient cooling method according to claim 9, wherein different low-temperature gases have different temperature ranges, so that molding sands with different thermal conductivity coefficients all have high refrigeration efficiency.

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