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

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 by micro-holes inside the multi-passes of frozen sand molds. [Background technology]

[0002] The traditional casting industry consumes a lot of resources and needs to make casting molds by copying sand molds with wooden / metal molds. Sand casting faces problems such as long production cycle, many production processes, high work intensity, high development costs of finished products, and poor operating environment. The traditional casting industry urgently needs to break through and transform its processes to green, and promote the energy reduction, emission reduction, and green and sustainable development of the manufacturing industry. By adopting green casting processes and equipment, we can reduce the waste of materials and energy in the casting process, reduce waste emissions, reduce the defective rate of castings, improve the quality rate of castings, and realize efficient, high-quality, accurate molding of castings, and realize green casting production. Summary of the Invention [Problem to be solved by the invention]

[0003] The green casting molding technology of digitalized frozen sand mold uses water as an adhesive, realizes the adhesion of casting sand and digitalized cutting / printing molding of sand mold under low temperature conditions, and can produce high-quality castings. Its principle is to use the direct molding of the printing nozzle / milling cutter to manufacture the material increase / decrease of the frozen sand mold (core) by driving by the three-dimensional CAD model of the sand mold, and obtain the sand mold to be cast after surface treatment and assembly. Before the cutting of the frozen sand mold, it is important whether the strength and hardness of the manufactured frozen sand blank meets the efficient cutting of digitalization. The strength and hardness of the frozen sand blank depend on the water content, freezing temperature, mesh number of sand grains, etc. Under the conditions of the existing equipment, the large-sized frozen sand blank faces problems such as long freezing time, high cost, and difficult demolding, and it is urgently necessary to develop new methods and new equipment to realize the rapid freezing of the frozen sand mold, and facilitate demolding and low-cost molding. [Means for solving the problem]

[0004] In order to solve the above problems, the present invention discloses a highly efficient cooling method and apparatus using micropores inside the multi-pass of a frozen sand mold, which mainly solves the problems of low freezing efficiency, low density, and difficult demolding of pre-mixed wet foundry sand during the blank manufacturing process.

[0005] A highly efficient cooling device with 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, the frozen sand mold molding chamber is located in the frozen sand mold cooling device box and its bottom is installed on 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 low-temperature cooling system includes a U-shaped condenser tube, a liquid nitrogen tank, a nitrogen gas tank, a flowmeter, a check valve and a low-temperature gas mixing cavity, the U-shaped condenser tube is located in the cooling device box of the frozen sand mold, the liquid nitrogen tank is connected to the low-temperature gas mixing cavity through a first pipeline, the first pipeline is provided with a check valve, the nitrogen gas tank is connected to the low-temperature gas mixing cavity through a second pipeline, the second pipeline is provided with a flowmeter and a check valve in turn, and the low-temperature gas mixing cavity is connected to the U-shaped condenser tube. The external low-temperature gas is connected to the U-shaped condenser tube through a low-temperature-resistant pipeline to realize the rapid cooling of the frozen sand mold molding chamber 1.

[0008] The Teflon porous liner and the removable porous aluminum plate are provided with through holes of the same size and position, and after assembly, it can ensure that the cold air can enter the frozen sand mold through the through holes. The Teflon porous liner is made of four Teflon molds joined together, and the joints of the Teflon molds are designed in a square shape. When the core of the frozen sand mold reaches a preset temperature, the lifting platform can be started to facilitate the 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 by 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). The specific implementation steps are as follows: S1, selecting appropriate molding sand according to the characteristics of the casting, weighing out 3% to 8% water by mass, putting it into a sand mixer and uniformly mixing 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 in 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 compact it, insert the iron wire along the through hole of the Teflon porous liner, form the exhaust hole with a certain regular arrangement in the frozen sand blank, start the electric lifting platform again, the frozen sand mold molding chamber is in the lower limit position; S3, start the low-temperature cooling system, the low-temperature gas and the nitrogen gas form a low-temperature mixed gas through the check valve, the low-temperature mixed gas is conveyed to the condensation pipe circuit through the pressure control valve for circulation cooling, and passes through the Teflon porous liner and the through-hole of the removable porous aluminum plate and rapidly enters the core part of the sand mold to freeze the frozen sand blank; S4: when the temperature inside the frozen sand mold reaches a preset temperature, open the sealing cover plate, select to start the electric lifting platform, and remove the frozen sand mold; or place the entire molding device of the frozen sand mold on the digital molding machine platform to perform digital cutting molding, and ensure that the strength and hardness of the frozen sand mold meets efficient cutting molding; when the core part of the frozen sand mold reaches the preset temperature, start the lifting platform to facilitate the demolding of the frozen sand mold; after the frozen sand mold is removed, milling can be performed in the digital molding machine.

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

[0011] In addition, a sealing cover plate used for thermal 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 sealing cover plate, and the film is made of one of EVA plastic film, LDPE (low density polyethylene film) or polyesteramine fiber, which are used for keeping moisture in the frozen sand mold.

[0012] In addition, the ultrasonic generator is set with two modes, namely, low frequency and high frequency. In the high frequency mode, the ultrasonic piezoelectric sheet transmits vibration for dense solidification in the frozen sand mold molding process, and prevents the frozen sand mold from having defects inside. 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 operated, first, the liquid nitrogen tank is opened to exhaust the air inside the pipeline, and after a certain period of time, the temperature of the space inside the pipeline is reduced, and liquid nitrogen is transported into the pipeline in liquid form; 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 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, 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.

[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 coefficients all have high refrigeration efficiency. Effect of the Invention

[0015] The beneficial effects of the present invention are as follows: (1) This technical solution uses the built-in ventilation holes in the frozen sand mold and the external low-temperature cooling system 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 in the molding process to make it densely solidified, and can use ultrasonic assist in cutting in the digital molding process, effectively reducing the cutting temperature, improving the processing quality, and extending the use time of the cutting head to reduce some costs. [Brief description 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. [Diagram 2] FIG. 2 is a schematic diagram showing the structure of the Teflon liner of the present invention. [Diagram 3] 3A and 3B are schematic diagrams showing the structure of the ventilation hole of the present invention, in which FIG. 3A shows a square shape, FIG. 3B shows a hexagonal lattice shape, FIG. 3C shows an R-shape, and FIG. 3D shows a circular shape. [Figure 4] FIG. 1 is a structural schematic diagram of a low-temperature cooling system of the present invention. [Diagram 5] FIG. 3 is an enlarged view of a portion A in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 are for the purpose of explaining the present invention and do not limit the scope of the present invention. Note that the terms "front", "back", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "inside" and "outside" refer to directions toward or away from the geometric center of a particular component, respectively.

[0019] As shown in FIG. 1, this is a highly efficient cooling device using micropores inside the multi-pass of frozen sand mold, 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 installed on the electric lifting platform 2. The frozen sand mold making chamber 1 is composed of the Teflon porous liner 3 and the removable porous aluminum plate 4. The ultrasonic piezoelectric sheet 7 is located between the Teflon porous liner 3 and the removable porous aluminum plate 4 and is 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 conductor 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 condensation tube 8, a liquid nitrogen tank 11, a nitrogen gas tank 12, a flowmeter 13, a check valve 14, and a low-temperature gas mixing cavity 15. The U-shaped condensation tube 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 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, and the second pipeline is provided with a flowmeter 13 and a check valve 14 in turn. The low-temperature gas mixing cavity 15 is connected to the U-shaped condensation tube 8 through a priority 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, so that after assembly, it is possible to ensure that cold air enters the inside of the frozen sand mold through the through holes.

[0023] As shown in Figs. 2 and 5, the Teflon porous liner 3 is made by connecting four Teflon molds, and the joints of the Teflon molds are designed in a square shape.

[0024] A highly efficient cooling method for multi-pass internal micro-holes of frozen sand mould, which is applied to the assistance of quick freezing and cutting process of frozen sand mould, the specific implementation steps are as follows: S1, selecting appropriate molding sand according to the characteristics of the casting, weighing out 3% to 8% water by mass, putting it into a sand mixer and uniformly mixing 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 in the upper limit position, the wet casting sand particles produced are spread in the frozen sand mold molding chamber, start the ultrasonic generator and select the low frequency range to vibrate the sand mold to make it dense and solidify, the ultrasonic generator has two modes of low frequency and high frequency, in the high frequency mode, the ultrasonic piezoelectric sheet transmits vibration for the dense solidification of the frozen sand mold molding process, and prevents the frozen sand mold from having defects inside, in the low frequency mode, the whole frozen sand mold molding die 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 the exhaust holes in the frozen sand blank with a certain regular arrangement, and then start the electric lifting platform again, so that the frozen sand mold making chamber is at the lower limit position; S3, start the low-temperature cooling system, the low-temperature gas and the nitrogen gas form a low-temperature mixed gas through the check valve, the low-temperature mixed gas is conveyed to the condensation pipe circuit through the pressure control valve for circulation cooling, and passes through the Teflon porous liner and the through-hole of the removable porous aluminum plate and rapidly enters the core part of the sand mold to freeze the frozen sand blank; When the low-temperature cooling system is in operation, first, the liquid nitrogen tank is opened to exhaust the air inside the pipeline. After a certain period of time, the temperature of the space inside the pipeline is reduced, 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 the nitrogen gas to enter the gas-liquid mixing cavity at a certain flow rate to mix with the liquid nitrogen. Taking advantage of the low-temperature properties of liquid nitrogen, the nitrogen gas is heat exchanged with the liquid nitrogen, and finally a constant-temperature low-temperature nitrogen gas is formed. Finally, it is transported to the condensation tube inside the device through the heat-insulating pipeline 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 coefficients all have high refrigeration efficiency.

[0026] S4: when the temperature inside the frozen sand mold reaches a preset temperature, open the sealing cover plate, select to start the electric lifting platform, and remove the frozen sand mold; or place the entire frozen sand mold making device on the digital molding machine platform to perform digital cutting molding, and ensure that the strength and hardness of the frozen sand mold meets efficient cutting molding; when the core part of the frozen sand mold reaches a preset temperature, start the lifting platform to facilitate the demolding of the frozen sand mold; 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 into regular arrangements of "square", "hexagonal lattice", "rice shape" and "circle" based on the fluent flow field and simulation, to accelerate the convection heat exchange of the low-temperature gas and improve the cooling efficiency of the sand mold.

[0028] A sealing cover plate 6 used for heat insulation is provided above the cooling device box of the frozen sand mold and the molding chamber of the frozen sand mold. A film is attached to the inner wall of the sealing cover plate. The film is made of one of EVA plastic film, LDPE (low density polyethylene film) or polyesteramine fiber, which are used for keeping 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 constituted by any combination of the above technical features. [Explanation of symbols]

[0030] 1...Frozen sand molding room 2. Electric lift platform 3. Teflon liner 4. Removable porous aluminum plate 5. Refrigeration sand mold cooling device box 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 using micro-pores inside the multi-pass frozen sand mold, The present invention includes a frozen sand mold molding room (1), an electric lifting platform (2), a cooling device box (5) for the frozen sand mold, 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 installed on the electric lifting platform (2), the frozen sand mold making chamber (1) is composed of a Teflon porous liner (3) and the removable porous aluminum plate (4), and an 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).

2. The highly efficient cooling device with micropores inside the multi-pass of frozen sand mold as described in claim 1, characterized in that the removable porous aluminum plate (4) is located outside the Teflon porous liner (3), and the ultrasonic piezoelectric sheet (7) is connected by a conductor to an ultrasonic generator (9) located outside the cooling device box (5) of the frozen sand mold.

3. 2. The highly efficient cooling device using micropores inside the multi-pass of frozen sand mold according to claim 1, wherein the low-temperature cooling system (10) comprises a U-shaped condensing tube (8), a liquid nitrogen tank (11), a nitrogen gas tank (12), a flowmeter (13), a check valve (14) and a low-temperature gas mixing cavity (15), the U-shaped condensing tube (8) is located in the cooling device box (5) of the frozen sand mold, the liquid nitrogen tank (11) is connected to the low-temperature gas mixing cavity (15) through a first pipeline, the first pipeline is 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 is provided with a flowmeter (13) and a check valve (14), and the low-temperature gas mixing cavity (15) is connected to the U-shaped condensing tube (8) through a pressure regulating valve and a low-temperature pipeline.

4. The Teflon 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 frozen sand mold through the through holes. The Teflon porous liner (3) is made of four Teflon molds joined together. The highly efficient cooling device using micro-holes inside the multi-pass frozen sand mold as claimed in claim 1, characterized in that the joint of the Teflon mold is designed in a square shape.

5. A highly efficient cooling method using micropores inside the multi-pass frozen sand mold, The method is applied to the quick freezing and auxiliary cutting process of frozen sand molds by the apparatus as described in claim 1, 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% water by mass, putting the water into a sand mixer and uniformly mixing 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 in 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 compact it, insert the iron wire along the through hole of the Teflon porous liner, form the exhaust hole with a certain regular arrangement in the frozen sand blank, start the electric lifting platform again, the frozen sand mold molding chamber is in the lower limit position; S3, start the low-temperature cooling system, the low-temperature gas forms a low-temperature mixed gas with the nitrogen gas through the check valve, the low-temperature mixed gas is conveyed to the condensation pipe circuit through the pressure control valve for circulation cooling, and passes through the Teflon porous liner and the through-hole of the removable porous aluminum plate to rapidly enter the core part of the sand mold, and freezes 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 selected to be activated, and the frozen sand mold is taken out; or the entire molding device for the frozen sand mold is placed on the digital molding machine platform to carry out digital cutting molding, and 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, and the frozen sand mold is easily demolded; after the frozen sand mold is taken out, it can be placed on the digital molding machine for milling.

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

7. The highly efficient cooling method for frozen sand molds using micropores inside the multi-passes of the frozen sand molds, as described in claim 5, characterized in that a sealing cover plate (6) used for thermal insulation is provided above the cooling device box (5) of the frozen sand molds and the molding chamber of the frozen sand molds, 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 used for moisturizing the frozen sand molds.

8. The highly efficient cooling method for frozen sand mold by multi-pass internal microholes as claimed in claim 5, characterized in that: the ultrasonic generator is set with two modes, namely, low frequency and high frequency; in the high frequency mode, the ultrasonic piezoelectric sheet transmits vibration for dense solidification in the frozen sand mold molding process, and prevents defects inside the frozen sand mold; in the low frequency mode, the entire frozen sand mold molding die is placed on the digital molding machine to realize the ultrasonic milling function of the frozen sand mold.

9. The highly efficient cooling method for the frozen sand mold using micropores inside the multi-pass as claimed in claim 5, characterized in that when the low-temperature cooling system is operated, first, the liquid nitrogen tank is opened to discharge the air inside the pipeline, and after a certain period of time, the temperature of the space inside the pipeline is reduced, and the liquid nitrogen is transported into the pipeline in liquid form; 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 to mix with the liquid nitrogen, and by utilizing the low-temperature characteristics of the liquid nitrogen, the nitrogen gas is heat exchanged with the liquid nitrogen, and finally, low-temperature nitrogen gas is formed, which is finally transported to the condensation tube inside the device through the heat-insulating pipeline to lower the temperature of the frozen sand mold.

10. The liquid nitrogen tank is filled with compressed cryogenic air or cryogenic CO ２ The highly efficient cooling method of the multi-pass internal micropores of the frozen sand mold according to claim 9, characterized in that the different low-temperature gases have different temperature ranges, so that the molding sands with different thermal conductivity coefficients all have high refrigeration efficiency.

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