Air pressure vibration anti-gravity casting method and device

Abstract

The invention provides an air pressure vibration anti-gravity casting method and device.The method comprises the steps that a high-temperature alloy raw material is put into a crucible, and the crucible is placed at the designated position of a smelting furnace; vacuumizing an upper chamber and a lower chamber of the smelting furnace, and melting the high-temperature alloy raw material into a high-temperature alloy melt at a target temperature according to a preset smelting process; a shell is installed in the upper cavity, a riser tube is installed in the lower cavity, the lower end of the riser tube is immersed in the high-temperature alloy melt, and the upper end of the riser tube extends into the upper cavity and is connected with the shell; in the mold filling process, the gas pressure of the upper and lower cavities is adjusted to form a pressure difference, and the alloy melt is pushed to enter the mold cavity; in the solidification process, the gas pressure of the upper cavity and the gas pressure of the lower cavity are adjusted, and the vibration pressure difference is formed between the upper cavity and the lower cavity; and after the casting is solidified completely, the upper cavity and the lower cavity are decompressed, and the target casting is obtained. According to the method, the melt is solidified under the vibration pressure difference, the feeding capacity of the melt is improved, the structure is refined, and therefore the service performance of a casting is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of counter-gravity casting, and in particular to a pneumatic vibration counter-gravity casting method and device. Background Art

[0002] Large, complex castings suffer from slow cooling rates, wide mushy zones at the liquid-solid interface, and difficulty feeding the melt. This results in coarse grains and numerous porosity defects, leading to insufficient mechanical properties and service life. Applying an external field to the melt during the filling and solidification process to promote the breakup of initially formed grains can effectively increase the nucleation base in the melt, thereby refining the grains and improving the mechanical properties of the casting. This, in turn, promotes melt feeding and reduces porosity defects. This method has been widely used in conventional gravity casting, for example by rotating the mold shell or applying mechanical or ultrasonic vibration to the shell.

[0003] Counter-gravity casting is a casting process in which the alloy liquid is injected upward into the mold along a riser tube using external pressure as the filling power. This method can reduce air entrapment and slag inclusions, and improve the quality of the casting. The counter-gravity casting filling process has high power and controllable melt flow, so it has good molding capabilities for complex thin-walled castings. In counter-gravity precision casting, the ceramic mold shell is placed in the upper chamber, and the lower end is tightly connected to the riser tube as a whole. The lower end of the riser tube is immersed in the melt in the crucible; to ensure airtightness, the riser tube is tightly connected to the middle partition where the upper and lower chambers meet to achieve sealing. Therefore, the relative positions of the ceramic mold shell and the riser tube are fixed, making it difficult to place the mold shell on a mechanical vibration table to apply vibration or rotate the mold shell as in traditional gravity casting. Therefore, traditional mechanical vibration and rotation are difficult to apply in the counter-gravity precision casting process.

[0004] Patent publication number CN119035505A discloses a high-pressure counter-gravity casting apparatus and a method for ultra-high-pressure counter-gravity casting of high-density magnesium alloys. The apparatus comprises an upper tank, a lower tank, a melt crucible, a riser, a casting mold, a pressurized air intake system for the upper tank, a pressurized air intake system for the lower tank, an exhaust system for the upper tank, an exhaust system for the lower tank, and a baffle for locking and ventilating the upper and lower tanks. In this prior art, the pressure in the lower tank is 4-6 MPa higher than that in the upper tank, increasing the pressure differential to improve casting performance. In this method, the holding pressure is maintained at a constant value, and the melt solidifies and crystallizes at this constant pressure.

[0005] The patent publication number CN109513900A discloses a low-pressure casting process for ingots using an electromagnetic pump and a low-pressure casting process for parts using an electromagnetic pump. The steps are: determining the filling pressure and the holding pressure, and performing low-pressure casting with the electromagnetic pump. When the filling stage is completed, the electromagnetic pump repeatedly outputs two different pressure values ​​at a certain frequency until the upper part of the casting solidifies, and then continues to pressurize under the holding pressure until the casting is completely solidified. This existing technology uses the pressure provided by the electromagnetic pump as the alloy filling power, which is suitable for low-pressure casting of small alloy castings. It is not suitable for high-density, large alloy castings, as well as differential pressure casting and pressure regulation casting of anti-gravity casting.

[0006] Patent publication number CN105344974A discloses a method for applying fluctuating pressure during low-pressure casting. During low-pressure casting of alloy castings, after the alloy castings complete the liquid raising, mold filling, and pressurization stages, fluctuating pressure is applied for the holding stage. After the castings are fully solidified, the fluctuating pressure is removed, completing the low-pressure casting. The holding stage lasts for a period of t, which is the duration from the start of the holding stage until the castings are fully solidified. This prior art describes a design method for pressure fluctuations but does not address how to achieve such fluctuations. Summary of the Invention

[0007] In view of the defects in the prior art, the purpose of the present invention is to provide a pneumatic vibration counter-gravity casting method and device to improve the mechanical properties of counter-gravity castings.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] According to one aspect of the present invention, there is provided a pneumatic vibration counter-gravity casting method, comprising:

[0010] Putting high-temperature alloy raw materials into a crucible, and placing the crucible at a designated position in a melting furnace;

[0011] The upper chamber and the lower chamber of the smelting furnace are both evacuated, and then the high-temperature alloy raw material is melted into a high-temperature alloy melt at a target temperature according to a preset smelting process;

[0012] A mold shell is installed in the upper chamber, and a riser pipe is installed in the lower chamber, wherein the lower end of the riser pipe is immersed in the high-temperature alloy melt, and the upper end extends into the upper chamber and is connected to the mold shell;

[0013] During the filling process, the gas pressures in the upper chamber and the lower chamber are adjusted to form a pressure difference, thereby pushing the alloy melt into the mold cavity;

[0014] During the solidification process, regulating the gas pressures in the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber;

[0015] After the casting is completely solidified, the pressure in the upper chamber and the lower chamber is released to obtain the target casting.

[0016] Optionally, adjusting the gas pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber includes: forming an oscillating pressure difference between the upper chamber and the lower chamber by separately adjusting the pressure of the lower chamber.

[0017] Optionally, adjusting the gas pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber includes: forming an oscillating pressure difference between the upper chamber and the lower chamber by adjusting the pressure of the upper chamber alone.

[0018] Optionally, the adjusting the gas pressures of the upper chamber and the lower chamber to form a vibrating pressure difference between the upper chamber and the lower chamber includes: forming a vibrating pressure difference between the upper chamber and the lower chamber by simultaneously adjusting the pressures of the upper chamber and the lower chamber.

[0019] Optionally, the gas pressures of the upper chamber and the lower chamber are adjusted to form a vibrating pressure difference between the upper chamber and the lower chamber, wherein the frequency and amplitude of the vibrating pressure difference are adjusted according to process requirements.

[0020] According to another aspect of the present invention, there is provided a pneumatic vibration counter-gravity casting device for implementing the above-mentioned pneumatic vibration counter-gravity casting method, the device comprising:

[0021] a lower chamber, wherein a crucible is placed in the lower chamber, and the crucible is used for melting high-temperature alloy raw materials;

[0022] an upper chamber in which the mold shell is placed;

[0023] a partition plate, disposed between the upper chamber and the lower chamber;

[0024] a riser pipe, the riser pipe passing through the partition plate, one end of the riser pipe being immersed in the crucible and the other end being connected to the gate of the mold shell;

[0025] The air pressure control device is connected to the upper chamber and the lower chamber respectively. During the solidification process, the air pressure wave control device fills or releases gas into or out of the upper chamber and the lower chamber respectively as required, thereby forming a vibrating pressure difference between the upper chamber and the lower chamber.

[0026] Optionally, the air pressure control device includes an air pressure regulating control mechanism and an upper chamber air inlet channel, an upper chamber exhaust channel, a lower chamber air inlet channel and a lower chamber exhaust channel respectively connected to the air pressure regulating control mechanism.

[0027] Optionally, the gas pressure regulating control mechanism regulates the gas flow and / or pressure of each channel according to a preset pressure regulation curve.

[0028] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0029] 1. The present invention forms a vibrating pressure difference between the upper and lower chambers by adjusting the pressure. The vibrating pressure difference forces the melt to vibrate, flushing dendrites, refining grains, and improving the melt shrinkage feeding capacity, thereby improving the service performance of the casting.

[0030] 2. The present invention applies gas pressure difference vibration during the entire solidification process, which has a longer duration and wider range of shrinkage feeding and grain refinement effects on the entire casting, thereby effectively improving the grain refinement effect.

[0031] 3. The present invention is applicable to most counter-gravity casting methods (including low-pressure casting, differential pressure casting and pressure-regulated casting). In addition, the present invention can be used not only for low-density, small alloy castings, but also for high-density, large alloy castings, and has a wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0033] Figure 1 A schematic diagram showing a regular oscillation of the pressure difference between the upper and lower chambers in an embodiment of the present invention;

[0034] Figure 2 Schematic diagram of the structure of a pneumatic vibration anti-gravity casting device in one embodiment of the present invention;

[0035] In the figure, the corresponding reference numerals are: 1 is a crucible, 2 is a lower chamber, 3 is a mold shell, 4 is an upper chamber, 5 is a riser, 6 is a partition, 7 is an air pressure regulating control mechanism, 8 is an exhaust channel for the lower chamber, 9 is an air inlet channel for the lower chamber, 10 is an air inlet channel for the upper chamber, and 11 is an exhaust channel for the upper chamber. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0037] Existing mechanical vibration or rotation methods are not suitable for counter-gravity casting. The embodiment of the present invention proposes a pneumatic vibration casting method suitable for counter-gravity casting to achieve the purpose of refining the grain size.

[0038] An embodiment of the present invention provides a pneumatic vibration counter-gravity casting method, comprising the following steps:

[0039] Step S1: placing a high-temperature alloy raw material in a crucible, and placing the crucible at a designated position in a smelting furnace;

[0040] Step S2: evacuating both the upper chamber and the lower chamber of the smelting furnace to a vacuum state, and then melting the high-temperature alloy raw material into a high-temperature alloy melt at a target temperature according to a preset smelting process;

[0041] Step S3, installing a mold shell in the upper chamber and installing a riser tube in the lower chamber, wherein the lower end of the riser tube is immersed in the high-temperature alloy melt, and the upper end extends into the upper chamber and is connected to the mold shell;

[0042] Step S4: adjusting the gas pressures in the upper chamber and the lower chamber to form a pressure difference, thereby pushing the alloy liquid into the mold cavity to complete the filling process;

[0043] Step S5: During the entire solidification process, the gas pressures in the upper chamber and the lower chamber are adjusted to form an oscillating pressure difference between the upper chamber and the lower chamber;

[0044] Step S6: After the casting is completely solidified, the upper chamber and the lower chamber are depressurized, and the casting is taken out to obtain the target casting.

[0045] In an embodiment of the present invention, the pressure in the lower cavity is higher than that in the upper cavity, and the pressure difference between the upper and lower cavities is used to push the alloy into the mold. By changing the pressure of the upper and lower chambers, a vibrating pressure difference is formed between the upper and lower chambers, and the vibrating pressure is transmitted to various parts of the mold through the melt, thereby achieving the purpose of breaking dendrites and refining grains.

[0046] In the above-described embodiments of the present invention, during the filling process, the pressure differential gradually increases to force the melt into the mold shell. During the solidification phase after filling, the melt no longer flows significantly, dissipating heat and cooling under the oscillating pressure differential. The oscillating pressure differential in this embodiment of the present invention is designed to oscillate within a certain range, while ensuring that the pressure differential is sufficient to fully fill the mold cavity. The frequency and amplitude of the pressure differential oscillation are determined based on factors such as the target alloy type, casting process parameters, and casting structure.

[0047] The vibration in the embodiment of the present invention is generated by air pressure. By controlling the frequency and amplitude of the vibration, the pressure difference of the vibration is precisely controlled, which has the advantages of low cost and low technical difficulty. Existing vibration methods are mainly ultrasonic vibration and mechanical vibration. In terms of the vibration transmission path, in ultrasonic vibration and mechanical vibration, the vibration source is transmitted to the interior of the casting through the mold shell, and the energy acting on the melt / solid phase interface is attenuated. The above-mentioned embodiment of the present application uses air pressure vibration. The energy transmission path is transmitted through the melt, which can reach almost all the melt / solid phase interfaces of the casting, and the energy attenuation is less.

[0048] Compared with the patent with publication number CN119035505A, the embodiment of the present invention applies vibratory pressure to ensure that the melt is completely filled in the mold shell while also having pressure fluctuations. The fluctuating pressure can push the melt to flush the dendrites, thereby refining the grains and improving the melt shrinkage compensation effect, thereby further improving the service performance of the casting.

[0049] In some optional embodiments, an oscillating pressure difference is formed between the upper chamber and the lower chamber by separately adjusting the pressure of the lower chamber.

[0050] In some optional embodiments, an oscillating pressure difference is formed between the upper chamber and the lower chamber by adjusting the pressure of the upper chamber alone.

[0051] The above-mentioned method of adjusting the pressure of the upper and lower chambers can be specifically achieved by filling or releasing gas into the corresponding chambers.

[0052] In some optional embodiments, by simultaneously adjusting the pressures in the upper and lower chambers, an oscillating pressure differential is formed between the upper and lower chambers. This adjustment method can increase the vibration frequency limit of the pressure differential and the pressure build-up speed.

[0053] In some embodiments, a 75-100 kPa oscillatory pressure differential is established between the upper and lower chambers for 8-20 minutes. By applying gas pressure oscillation throughout the solidification process, the overall shrinkage feeding and grain refinement effects on the casting are prolonged and extended, effectively enhancing grain refinement.

[0054] In order to form the above-mentioned 75-100 kPa vibration pressure difference, for example, the upper chamber pressure is maintained at 50 kPa and the lower chamber pressure vibrates between 150-125 kPa, which can generate a vibration pressure difference and thus produce the desired vibration effect.

[0055] It should be noted that the amplitude of the fluctuation is designed according to the casting process requirements. An appropriately large amplitude will improve the melt flushing and shrinkage compensation effects, but an excessively large amplitude will produce greater pressure on the mold shell and casting, resulting in mold shell breakage or casting deformation.

[0056] In the above embodiment of the present invention, by adjusting the air pressure amplitude, frequency and holding time of the upper and lower chambers, the desired vibration effect can be achieved to improve the mechanical properties of the casting.

[0057] The above-mentioned embodiment of the present invention introduces air pressure differential vibration during counter-gravity casting to promote grain refinement, improve mechanical properties, reduce porosity and shrinkage, and reduce defects. Thus, the performance of counter-gravity castings can be effectively optimized.

[0058] In one embodiment, in order to improve the mechanical properties of the anti-gravity casting high-temperature alloy casting, the following method is formulated: Figure 1 The pressure control scheme shown is used, and anti-gravity vibration casting is performed based on the pressure control scheme. The specific steps are as follows:

[0059] (1) Place sufficient high-temperature alloy raw materials in a crucible and place the crucible in a designated position in the melting furnace;

[0060] (2) Using a pressure control mechanism to control the airflow, the upper and lower chambers are evacuated to 5 Pa, and then the raw materials in the crucible are melted to the target temperature according to the high-temperature alloy melting process;

[0061] (3) placing the mold shell and riser tube in a predetermined position so that the lower end of the riser tube is immersed in the high-temperature alloy melt and the upper end is tightly connected to the mold shell;

[0062] (4) The pressure in the upper and lower chambers is adjusted by the air pressure control mechanism so that the pressure in the upper and lower chambers is adjusted according to the pressure control scheme ( Figure 2 )implement;

[0063] (5) During the pressure holding stage, the upper chamber pressure was maintained at 50 kPa, and the lower chamber pressure was vibrated between 150 and 125 kPa, with a frequency of 0.2 Hz, and the pressure difference between the upper and lower chambers was vibrated between 100 and 75 kPa, and the vibration time was 8 minutes;

[0064] (6) After maintaining pressure for 8 minutes, the casting is completely solidified, the air pressure vibration is stopped, the upper and lower chambers are depressurized, and the casting is taken out.

[0065] Another embodiment of the present invention provides a gas pressure vibration anti-gravity casting device for implementing the above-mentioned gas pressure vibration anti-gravity casting method, referring to Figure 2As shown, the device includes an upper chamber 4, a lower chamber 2, a partition 6, a mold shell 3, a riser pipe 5, a crucible 1, an air pressure control device, etc., wherein: the crucible 1 is placed in the lower chamber 2, and the crucible 1 is used to melt high-temperature alloy raw materials; the mold shell 3 is placed in the upper chamber 4; the partition 6 is arranged between the upper chamber 4 and the lower chamber 2; the hollow riser pipe 5 passes through the partition 6, one end of the riser pipe 5 is immersed in the crucible 1, and the other end is tightly connected with the gate of the mold shell 3; the air pressure control device is respectively connected to the upper chamber 4 and the lower chamber 2. During the solidification process, the air pressure control device fills or releases gas into or out of the upper chamber 4 and the lower chamber 2 as needed, forming a vibrating pressure difference between the upper chamber 4 and the lower chamber 2.

[0066] In some embodiments, the air pressure control device includes an air pressure regulating and controlling mechanism 7, and an upper chamber air inlet channel 10, an upper chamber exhaust channel 11, a lower chamber air inlet channel 9, and a lower chamber exhaust channel 8, respectively connected to the air pressure regulating and controlling mechanism 7. During the filling process, the air pressure regulating and controlling mechanism 7 fills the upper and lower chambers with air as required through the respective air channels, causing the air pressure in the lower chamber to be greater than that in the upper chamber. This creates a pressure differential according to a predetermined program, forcing the high-temperature melt to flow upward through the riser tube 5 into the mold shell 3, completing the filling process. The air pressure in the lower chamber is then further increased and maintained for solidification. After the casting has solidified, the pressure is released and the casting is removed.

[0067] The above embodiment of the present invention can realize air pressure vibration by adjusting the pressure of the lower tank alone, adjusting the pressure of the upper tank alone, and adjusting the pressure of the upper and lower tanks simultaneously. The adjustment method is relatively flexible. The air pressure fluctuation control can be achieved by using existing high-precision air pressure control methods.

[0068] In some embodiments, the gas pressure regulating control mechanism 7 regulates the gas flow and / or pressure of each channel according to a preset pressure control curve.

[0069] In the above-mentioned embodiment of the present invention, during the pressure-maintaining solidification process, the air pressure in the upper and lower chambers is changed by the air pressure control device, and periodic air pressure changes are applied, so that the pressure difference between the upper and lower chambers exhibits regular vibrations, thereby achieving the effect of applying vibration pressure to the melt, forcing the melt to vibrate under the action of the vibration pressure, achieving the purpose of refining the grains and reducing porosity, thereby improving the performance of the casting.

[0070] The above-mentioned embodiment of the present invention applies vibration during the solidification process. Through the combination of counter-gravity casting and vibration, the quality of the casting can be significantly improved. It is applicable to most counter-gravity casting (including low-pressure casting, differential pressure casting and pressure-regulated casting) methods. In addition, the above-mentioned embodiment of the present invention can be used not only for low-density, small alloy castings, but also for high-density, large alloy castings. It has a wide applicability and can be applied to aerospace, automobile manufacturing, electronics industry and other fields with high performance requirements.

[0071] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various modifications or variations within the scope of the claims without affecting the essence of the present invention. The above preferred features may be used in any combination as long as they do not conflict with each other.

Claims

1. A pneumatic vibration anti-gravity casting method, characterized in that: include: Putting high-temperature alloy raw materials into a crucible, and placing the crucible at a designated position in a melting furnace; The upper chamber and the lower chamber of the smelting furnace are both evacuated, and then the high-temperature alloy raw material is melted into a high-temperature alloy melt at a target temperature according to a preset smelting process; A mold shell is installed in the upper chamber, and a riser pipe is installed in the lower chamber, wherein the lower end of the riser pipe is immersed in the high-temperature alloy melt, and the upper end extends into the upper chamber and is connected to the mold shell; During the mold filling process, the gas pressures in the upper chamber and the lower chamber are adjusted to form a pressure difference, thereby pushing the alloy melt into the mold cavity; During the solidification process, regulating the gas pressures in the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber; After the casting is completely solidified, the pressure in the upper chamber and the lower chamber is released to obtain the target casting.

2. The pneumatic vibration counter-gravity casting method according to claim 1, characterized in that: The regulating the gas pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber includes: forming an oscillating pressure difference between the upper chamber and the lower chamber by separately regulating the pressure of the lower chamber.

3. The pneumatic vibration counter-gravity casting method according to claim 1, characterized in that: The regulating the gas pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber includes: forming an oscillating pressure difference between the upper chamber and the lower chamber by regulating the pressure of the upper chamber alone.

4. The pneumatic vibration counter-gravity casting method according to claim 1, characterized in that: The regulating the gas pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber includes: simultaneously regulating the pressures of the upper chamber and the lower chamber to form an oscillating pressure difference between the upper chamber and the lower chamber.

5. The pneumatic vibration counter-gravity casting method according to claim 1, characterized in that: The gas pressures of the upper chamber and the lower chamber are adjusted to form a vibrating pressure difference between the upper chamber and the lower chamber, wherein the frequency and amplitude of the vibrating pressure difference are adjusted according to process requirements.

6. A pneumatic vibration counter-gravity casting device for implementing the pneumatic vibration counter-gravity casting method according to any one of claims 1 to 5, characterized in that: The device comprises: a lower chamber, wherein a crucible is placed in the lower chamber, and the crucible is used for melting high-temperature alloy raw materials; an upper chamber in which the mold shell is placed; a partition plate, disposed between the upper chamber and the lower chamber; a riser pipe, the riser pipe passing through the partition plate, one end of the riser pipe being immersed in the crucible and the other end being connected to the gate of the mold shell; The air pressure control device is connected to the upper chamber and the lower chamber respectively. During the solidification process, the air pressure control device fills or releases gas into or out of the upper chamber and the lower chamber respectively as required, thereby forming an oscillating pressure difference between the upper chamber and the lower chamber.

7. The pneumatic vibration anti-gravity casting device according to claim 6, characterized in that: The air pressure control device includes an air pressure regulating control mechanism and an upper chamber air inlet channel, an upper chamber exhaust channel, a lower chamber air inlet channel and a lower chamber exhaust channel respectively connected to the air pressure regulating control mechanism.

8. The pneumatic vibration anti-gravity casting device according to claim 7, characterized in that: The gas pressure regulating control mechanism regulates the gas flow and / or pressure of each channel according to a preset pressure control curve.

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