A graphite mold casting equipment and process for titanium alloy castings

Abstract

This invention relates to a graphite mold casting equipment and process for titanium alloy castings, specifically in the field of negative pressure suction casting. The graphite mold casting equipment for titanium alloy castings includes a melting chamber, a suction casting chamber, a mold, a suction casting pump, a protective gas injection device, a liquid flow monitoring system, an ultrasonic vibration system, and a water-cooled copper crucible fixed within the melting chamber. The lower end of the melting chamber is connected to the upper end of the upper cavity via the liquid flow monitoring system. The ultrasonic vibration system is fixedly installed in the lower cavity and detachably connected to the mold. In this design, the liquid flow monitoring system is triggered the instant the molten titanium alloy flows down, activating the suction casting pump and suction casting valve. The combination of negative pressure suction casting and liquid flow monitoring triggering achieves precise control of the melt filling, reduces human intervention errors, and improves process stability and controllability. After the melt is injected into the graphite mold, ultrasonic vibration is applied to the mold to assist in the dissipation of air bubbles within the melt and improve shrinkage cavities and porosity defects.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy casting, and specifically to a graphite mold casting equipment and process for titanium alloy castings. Background Technology

[0002] Small high-entropy alloy castings are mostly military-grade castings in actual production. They have extremely high quality requirements and require ultrasonic flaw detection throughout the casting. The alloy material has a high melting point and a narrow solidification range. It is very easy to react with the mold material and the atmosphere at high temperatures. Therefore, most castings are melted and poured in a vacuum environment or an inert gas environment.

[0003] Furthermore, traditional vacuum arc remelting (VAR) and casting furnaces have limited superheat of titanium melt, and the contact between the melt and the crucible refractory material poses a risk of contamination, which is not conducive to obtaining high-purity titanium alloy melt and makes it difficult to meet the metallurgical quality requirements of high-performance thin-walled castings. Although parts obtained by machining have better material mechanical properties, the process yield is extremely low, the processing time is long, and the cost is high. Therefore, for this product, optimizing the casting process, eliminating gas shrinkage cavities, and improving the process yield are particularly critical. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to improve the yield of titanium alloy castings.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A graphite mold casting equipment for titanium alloy castings includes a melting chamber, a suction casting chamber, a mold, a suction casting pump, a protective gas injection device, and a water-cooled copper crucible fixed in the melting chamber. The suction casting chamber is divided into an independent upper cavity and a lower cavity by a partition. The mold is detachably installed on the partition. The mold has a forming cavity. The upper and lower ends of the forming cavity are respectively connected to the upper cavity and the lower cavity. The outlet of the water-cooled copper crucible is located directly above the forming cavity. The suction casting pump is connected to the lower cavity. The protective gas injection device is connected to the melting chamber. The equipment also includes a liquid flow monitoring system and an ultrasonic vibration system. The lower end of the melting chamber is connected to the upper end of the upper cavity through the liquid flow monitoring system. The ultrasonic vibration system is fixedly installed in the lower cavity and detachably connected to the mold.

[0006] The beneficial effects of this invention are as follows: In this solution, a vacuum cold crucible suspension melting furnace is used as the casting equipment. The titanium alloy raw material is suspended and melted in a water-cooled copper crucible environment by a high-frequency electromagnetic field, so that the melt is kept away from the water-cooled copper crucible as much as possible, and a clean high-temperature alloy melt is obtained. The temperature of the titanium alloy melt obtained in this way is significantly higher than that of the titanium alloy melt obtained by vacuum self-consumable melting.

[0007] The lower chamber of the casting equipment is connected to a suction casting pump, which has a bottom-out negative pressure suction casting function. The suction casting pump draws the forming cavity of the mold to realize the rapid injection of molten metal into the graphite mold under negative pressure.

[0008] By installing a liquid flow monitoring system at the lower end of the melting chamber, the liquid flow monitoring system can be triggered the instant the titanium alloy melt flows down, thereby opening the suction casting pump and the suction casting valve on the connecting pipe between the lower chamber and the suction casting pump. The combination of negative pressure suction casting and liquid flow monitoring triggering realizes precise control of melt filling, reduces human intervention error, and improves process stability and controllability.

[0009] After the molten metal is injected into the graphite mold, an ultrasonic vibration system is activated to vibrate the mold at a frequency of 110-140 kHz. This helps to dissipate air bubbles inside the melt and improves shrinkage cavities and porosity defects. Building upon the effective filling achieved by negative pressure suction casting, ultrasonic vibration effectively breaks up dendrites, promotes melt flow and venting, thereby optimizing the solidification process immediately after filling. This results in a final casting free of porosity and shrinkage cavities, with a uniform microstructure.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the graphite mold casting equipment for titanium alloy castings also includes a vertically extending guide pipe. The upper end of the guide pipe is inserted into the outlet of the water-cooled copper crucible. A ceramic heat insulation tube is sleeved on the outside of the guide pipe, and a secondary coil is wound around the outside of the ceramic heat insulation tube. A plugging plate for sealing the guide pipe is placed at the upper end of the guide pipe, and the material of the plugging plate is the same as the casting material.

[0012] The beneficial effect of adopting the above-mentioned further scheme is that the guide tube guides the melt, allowing it to flow accurately into the mold below. Before melting is completed, a plug is used to seal the guide tube; after melting is completed, the secondary coil heats the plug, causing it to release the seal on the guide tube.

[0013] Furthermore, the liquid flow monitoring system includes a monitoring box and a monitoring device. The upper and lower ends of the monitoring box are respectively sealed and connected to the lower end of the melting chamber and the upper end of the upper cavity. The monitoring device is fixed to the side wall of the monitoring box and is used to acquire liquid flow information inside the monitoring box.

[0014] The beneficial effect of adopting the above-mentioned further solution is that a monitoring box is set between the melting chamber and the upper cavity. When the liquid flow of the melt passes through the monitoring box, the monitoring equipment detects the liquid flow information, and thus controls the opening of the negative pressure suction casting according to the liquid flow information.

[0015] Furthermore, the graphite mold casting equipment for titanium alloy castings also includes a sealing cylinder, which is a cylindrical shape that runs vertically through the interior and exterior. The upper and lower ends of the sealing cylinder are respectively sealed and connected to the lower end of the liquid flow monitoring system and the upper end of the forming cavity.

[0016] The beneficial effects of adopting the above-mentioned further solution are as follows: by using a sealing cylinder to seal the area between the bottom of the plug and the top of the forming cavity, a smaller space is formed inside the sealing cylinder compared to the original upper cavity, making it easier to be vacuumed. This indirectly increases the pressure difference between the upper and lower parts of the melt. The high-temperature melt after melting flows into the mold under the combined action of gas pressure and gravity, which increases the temperature of the titanium alloy entering the mold. At the same time, the negative pressure environment enhances the feeding ability of the high-temperature titanium alloy melt, significantly reducing the risk of defects in the titanium alloy casting.

[0017] Furthermore, a mold heating device is fixed on the partition plate, and the mold is detachably installed inside the mold heating device.

[0018] The beneficial effects of adopting the above-mentioned further solution are: an in-situ mold heating device is integrated into the casting equipment, allowing the vacuum high-temperature baking degassing and preheating processes of the mold to be completed directly at the pouring station. This design completely solves the problem in traditional processes where the mold, after being treated in an external degassing furnace, re-absorbs moisture and oxygen from the air during the transfer to the melting furnace. This ensures that the cavity in contact with the high-temperature molten titanium is always in a high-temperature, clean, and low-gas state, reducing the risk of surface and subcutaneous porosity and inclusion defects in the casting from the source.

[0019] Furthermore, the ultrasonic vibration system includes a vibration control system, a transducer, and a vibration ring connected in sequence. The vibration control system transmits high-frequency electrical signals to cause the transducer to convert electrical energy into high-frequency mechanical vibration, thereby driving the vibration ring to vibrate. The lower end of the mold is detachably inserted into the vibration ring.

[0020] The beneficial effects of adopting the above-mentioned further solution are: the vibration control system can dynamically adjust the ultrasonic vibration frequency; the high-frequency electrical signal generated by the vibration control system is transmitted to the transducer through a dedicated cable; the transducer converts electrical energy into high-frequency mechanical vibration and transmits it to the vibrating ring closely connected to it; the vibrating ring transmits this high-frequency, small-amplitude vibration to the entire mold. The vibration time is adjusted according to the specific solidification time of different materials, ensuring that the melt undergoes ultrasonic vibration throughout the entire filling and solidification process.

[0021] Furthermore, the bottom of the molding cavity is provided with multiple suction casting holes, and the molding cavity is connected to the lower cavity through the suction casting holes. The mold is also provided with an exhaust channel, and the side wall of the exhaust channel is connected with multiple branch channels from top to bottom. The branch channels are connected to the side wall of the molding cavity, and the end of the branch channel away from the exhaust channel is inclined downward. The lower end of the exhaust channel is connected to the lower cavity.

[0022] The beneficial effects of adopting the above-mentioned further solution are as follows: Multiple branch channels are set from top to bottom on the sidewall of the molding cavity and connected to the lower cavity. During the process of the melt flowing into the molding cavity, the suction hole and branch channels can continuously draw negative pressure into the molding cavity. Furthermore, this design avoids the blockage of the lower branch channels after the leading edge of the melt flow blocks the mold, and avoids the risk of horizontal or inclined branch channels being blocked by the leading edge of the melt in the early stages of filling. This ensures that the gas in the molding cavity can be continuously and effectively discharged throughout the entire filling process, greatly reducing the risk of porosity defects.

[0023] This invention also provides a graphite mold casting process for titanium alloy castings, comprising the following steps:

[0024] Step 1: Place the titanium alloy raw material into a water-cooled copper crucible; place the mold into the suction casting chamber and degas the mold.

[0025] Step 2: Heat the mold to the preset mold temperature, and at the same time evacuate the melting chamber to the preset vacuum level. Inject protective gas into the melting chamber through the protective gas injection device, and use the water-cooled copper crucible to perform induction melting of the titanium alloy raw material until the titanium alloy raw material is melted to the preset casting temperature.

[0026] Step 3: The melt flows out from the outlet of the water-cooled copper crucible and passes through the liquid flow monitoring system; based on the liquid flow information of the melt obtained by the liquid flow monitoring system, the suction casting pump is turned on, and the pressure in the lower cavity is drawn down to a level lower than that in the upper cavity. The ultrasonic vibration system is then turned on; the melt flows into the forming cavity of the mold under the action of the pressure difference, completing the filling of the titanium alloy casting. After cooling, the titanium alloy casting is obtained.

[0027] The beneficial effects are: the mold undergoes in-situ degassing within the suction casting chamber, preventing the re-absorption of moisture and oxygen from the air during mold transfer. Simultaneously, the mold degassing and differential pressure control significantly reduce the risk of gas entrapment, making the casting process more stable and suitable for mass production of thin-walled, complex castings. Furthermore, melting and pouring in a protective gas environment prevents reactions with air, ensuring casting quality. The combination of negative pressure suction casting and ultrasonic vibration effectively breaks down dendrites, promotes melt flow and venting, thereby optimizing the solidification process immediately after mold filling, resulting in a final casting free of porosity and shrinkage cavities with a uniform microstructure.

[0028] Furthermore, in step 1, the degassing process specifically includes: using a suction casting pump to evacuate the vacuum degree in the suction casting chamber to less than or equal to 5 Pa, and vacuum-firing the mold at a temperature of 900-1000°C for 4-6 hours.

[0029] The beneficial effect of adopting the above-mentioned further solution is that, through negative pressure suction and vacuum baking, impurities on the surface and inside of the mold can be eliminated as much as possible.

[0030] Furthermore, in step 2, the preset mold temperature is 400℃; the preset vacuum degree is less than 5×10⁻⁶. - 3 Pa; the protective gas is argon, and the pressure of the argon gas is 0.03-0.07 MPa;

[0031] In step 3, the pressure in the lower cavity is drawn down to a level lower than that in the upper cavity using a suction casting pump. Specifically, the pressure in the lower cavity is drawn down to a vacuum level of less than 10 Pa using a suction casting pump.

[0032] The beneficial effects of adopting the above-mentioned further scheme are: by using appropriate temperature and pressure parameters, while achieving good mold filling, defects such as shrinkage cavities and porosity are controlled, thereby obtaining a blank casting without shrinkage cavities. Subsequent heat treatment yields a casting with uniform microstructure, satisfactory performance, and no obvious casting defects. This method is particularly suitable for the high-density forming of thin-walled conical castings. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a graphite mold casting equipment for titanium alloy castings according to the present invention;

[0034] Figure 2 for Figure 1 A partial enlarged view of point A in a graphite mold casting equipment for titanium alloy castings;

[0035] Figure 3 This is a front view of the mold of the present invention;

[0036] Figure 4 This is a left view of the mold of the present invention;

[0037] Figure 5 This is a bottom view of the mold of the present invention;

[0038] Figure 6 for Figure 5 The BB-direction sectional view of the mold shown;

[0039] Figure 7 for Figure 5 The CC-direction sectional view of the mold shown.

[0040] The attached diagram lists the components represented by each number as follows:

[0041] 1. Melting chamber; 2. Water-cooled copper crucible; 3. Casting chamber; 31. Upper cavity; 32. Lower cavity; 4. Mold; 41. Molding cavity; 42. Casting hole; 43. Exhaust channel; 44. First mold block; 45. Second mold block; 46. Third mold block; 5. Casting pump; 6. Liquid flow monitoring system; 61. Monitoring box; 62. Monitoring equipment; 7. Ultrasonic vibration system; 71. Transducer; 72. Vibration ring; 8. Guide pipe; 9. Ceramic heat insulation pipe; 10. Secondary coil; 11. Sealing cylinder; 12. Mold heating device; 13. Plug; 14. Primary coil. Detailed Implementation

[0042] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0043] Example 1

[0044] like Figures 1-7 As shown, this embodiment provides a graphite mold casting equipment for titanium alloy castings, including a melting chamber 1, a suction casting chamber 3, a mold 4, a suction casting pump 5, a protective gas injection device, and a water-cooled copper crucible 2 fixed in the melting chamber 1. The suction casting chamber 3 is divided into an independent upper cavity 31 and a lower cavity 32 by a partition. The mold 4 is detachably installed on the partition and has a forming cavity 41. The upper and lower ends of the forming cavity 41 are respectively connected to the upper cavity 31 and the lower cavity 32. The outlet of the water-cooled copper crucible 2 is located directly above the forming cavity 41. The suction casting pump 5 is connected to the lower cavity 32. The protective gas injection device is connected to the melting chamber 1. The equipment also includes a liquid flow monitoring system 6 and an ultrasonic vibration system 7. The lower end of the melting chamber 1 is connected to the upper end of the upper cavity 31 through the liquid flow monitoring system 6. The ultrasonic vibration system 7 is fixedly installed in the lower cavity 32 and detachably connected to the mold 4.

[0045] The beneficial effects are as follows: In this scheme, a vacuum cold crucible suspension melting furnace is used as the casting equipment. The titanium alloy raw material is suspended and melted in a water-cooled copper crucible environment by a high-frequency electromagnetic field, so that the melt is kept away from the water-cooled copper crucible as much as possible, and a clean high-temperature alloy melt is obtained. The temperature of the titanium alloy melt obtained in this way is significantly higher than that of the titanium alloy melt obtained by vacuum self-consumable melting.

[0046] The lower cavity 32 of the casting equipment is connected to the suction casting pump 5, which has a bottom-out negative pressure suction casting function. The suction casting pump draws the forming cavity 41 of the mold 4 to realize the rapid injection of molten metal into the graphite mold under negative pressure.

[0047] By setting a liquid flow monitoring system 6 at the lower end of the melting chamber 1, the liquid flow monitoring system 6 can be triggered the instant the titanium alloy melt flows down, thereby opening the suction casting pump 5 and the suction casting valve on the connecting pipe between the lower chamber 32 and the suction casting pump 5. The combination of negative pressure suction casting and liquid flow monitoring triggering realizes precise control of melt filling, reduces human intervention error, and improves process stability and controllability.

[0048] After the melt is injected into the graphite mold, the ultrasonic vibration system 7 is activated to vibrate the mold 4 at a frequency of 110-140 kHz. This helps to dissipate air bubbles inside the melt and improves shrinkage cavities and porosity defects. Based on the good filling achieved by negative pressure suction casting, the introduction of ultrasonic vibration effectively breaks up dendrites, promotes melt flow and venting, thereby optimizing the solidification process immediately after filling. This results in a final casting free of porosity and shrinkage cavities with a uniform microstructure.

[0049] The protective gas injection device is a gas cylinder, and the outlet of the gas cylinder is connected to the melting chamber 1 via a valve. The protective gas contained in the gas cylinder is argon or other inert gas.

[0050] Both the melting chamber 1 and the suction casting chamber 3 are sealed box structures, connected by a connecting pipe equipped with a connecting valve. Before melting begins, the connecting valve can be opened to connect the melting chamber 1 and the suction casting chamber 3, allowing the suction casting pump 5 to simultaneously evacuate both chambers, eliminating the influence of air on the melting and casting process. After melting begins, the connecting valve is closed, and the melting chamber 1 and the suction casting chamber 3 are separated by a plug 13, ceasing all communication.

[0051] Among them, the structure of the water-cooled copper crucible 2 is the existing technology. A primary coil 14 is wound around its outer side. The water-cooled segmented copper crucible with slits is combined with a high-frequency alternating magnetic field. The molten metal is kept in a non-contact suspension state with the crucible wall by electromagnetic repulsion for melting.

[0052] Based on the above scheme, the graphite mold casting equipment for titanium alloy castings also includes a vertically penetrating guide pipe 8. The upper end of the guide pipe 8 is inserted into the outlet of the water-cooled copper crucible 2. A ceramic heat insulation pipe 9 is sleeved on the outside of the guide pipe 8. A secondary coil 10 is wound around the outside of the ceramic heat insulation pipe 9. A plug 13 for sealing the guide pipe 8 is placed at the upper end of the guide pipe 8. The material of the plug 13 is the same as the casting material.

[0053] The guide tube 8 guides the melt to flow accurately into the mold 4 below. Before melting is complete, the plug 13 is used to seal the guide tube 8. After melting is complete, the secondary coil 10 heats the plug 13 to release it from the seal of the guide tube 8.

[0054] Based on the above scheme, the liquid flow monitoring system 6 includes a monitoring box 61 and a monitoring device 62. The upper and lower ends of the monitoring box 61 are respectively sealed and connected to the lower end of the melting chamber 1 and the upper end of the upper cavity 31. The monitoring device 62 is fixed to the side wall of the monitoring box 61 and is used to acquire liquid flow information in the monitoring box 61.

[0055] A monitoring box 61 is installed between the melting chamber 1 and the upper cavity 31. When the liquid flow of the melt passes through the monitoring box 61, the monitoring equipment 62 detects the liquid flow information and can control the opening of the negative pressure suction casting based on the liquid flow information.

[0056] Among them, monitoring device 62 is a camera or other sensor that can detect liquid flow.

[0057] Based on the above scheme, the graphite mold casting equipment for titanium alloy castings also includes a sealing cylinder 11. The sealing cylinder 11 is a cylindrical shape that runs vertically through the top and bottom. The upper and lower ends of the sealing cylinder 11 are respectively sealed and connected to the lower end of the liquid flow monitoring system 6 and the upper end of the forming cavity 41.

[0058] The sealing cylinder 11 seals the area between the bottom of the plug 13 and the top of the forming cavity 41. Compared with the original upper cavity 31, the sealing cylinder 11 forms a smaller space area, which is easier to be vacuumed. This indirectly increases the pressure difference between the top and bottom of the melt. The high-temperature melt after melting flows into the mold 4 under the combined action of gas pressure and gravity, which increases the temperature of the titanium alloy entering the mold 4. At the same time, the negative pressure environment enhances the feeding ability of the high-temperature titanium alloy melt, which significantly reduces the risk of defects in the titanium alloy casting.

[0059] Based on the above scheme, a mold heating device 12 is also fixed on the partition plate, and the mold 4 can be detachably installed in the mold heating device 12.

[0060] An in-situ mold heating device 12 is integrated into the casting equipment, allowing the vacuum high-temperature baking degassing and preheating processes of the mold to be completed directly at the pouring station. This design completely solves the problem in traditional processes where the mold, after being treated in an external degassing furnace, re-absorbs moisture and oxygen from the air during the transfer to the melting furnace. This ensures that the cavity in contact with the high-temperature molten titanium is always in a high-temperature, clean, and low-gas state, reducing the risk of surface and subcutaneous porosity and inclusion defects in the casting from the source.

[0061] Based on the above scheme, the ultrasonic vibration system 7 includes a vibration control system, a transducer 71 and a vibration ring 72 connected in sequence. The vibration control system transmits high-frequency electrical signals to make the transducer 71 convert electrical energy into high-frequency mechanical vibration, thereby driving the vibration ring 72 to vibrate. The lower end of the mold 4 is detachably inserted into the vibration ring 72.

[0062] The vibration control system can dynamically adjust the ultrasonic vibration frequency. The high-frequency electrical signal generated by the vibration control system is transmitted to the transducer 71 through a dedicated cable. The transducer 71 converts the electrical energy into high-frequency mechanical vibration and transmits it to the vibration ring 72, which is closely connected to it. The vibration ring 72 transmits this high-frequency, small-amplitude vibration to the entire mold. The vibration time is adjusted according to the specific solidification time of different materials so that the melt can undergo ultrasonic vibration throughout the entire filling and solidification process.

[0063] Specifically, the lower end of the mold 4 has a cylindrical extension, and the vibration ring 72 is sleeved on the outside of the extension.

[0064] Based on the above scheme, the bottom of the molding cavity 41 is provided with a plurality of suction casting holes 42. The molding cavity 41 is connected to the lower cavity 32 through the suction casting holes 42. The mold 4 is also provided with an exhaust channel 43. The side wall of the exhaust channel 43 is connected to a plurality of branch channels from top to bottom. The branch channels are connected to the side wall of the molding cavity 41, and the end of the branch channel away from the exhaust channel 43 is inclined downward. The lower end of the exhaust channel 43 is connected to the lower cavity 32.

[0065] Multiple branch channels are arranged from top to bottom on the side wall of the molding cavity 41 and are connected to the lower cavity 32. During the process of the melt flowing into the molding cavity 41, the suction casting hole 42 and the multiple branch channels can continuously draw negative pressure into the molding cavity 41. Furthermore, this design avoids the blockage of the lower branch channels after the leading liquid flow fills the mold, and avoids the risk of horizontal or inclined branch channels being blocked by the leading edge of the melt in the early stage of filling. This ensures that the gas in the molding cavity 41 can be continuously and effectively discharged throughout the filling process, greatly reducing the risk of porosity defects.

[0066] For details on the structure of mold 4, please refer to [link / reference]. Figures 3-7 The mold 4 includes a semi-cylindrical first mold block 44, a semi-cylindrical second mold block 45, and a cylindrical third mold block 46. The first mold block 44 and the second mold block 45 are spliced ​​together to form a cylindrical main structure. The opposing sides of the first mold block 44 and the second mold block 45 are connected by two first positioning pins. The third mold block 46 is installed below the cylindrical main structure. The joint position of the first mold block 44, the second mold block 45, and the third mold block 46 is positioned by a second positioning pin. That is, the second positioning pin is located inside the first mold block 44, the second mold block 45, and the third mold block 46 simultaneously. The mold 4 is designed as three splicable movable blocks, which facilitates the multiple uses of the mold.

[0067] The cylindrical main structure forms a forming cavity 41. The top surface of the third mold block 46 constitutes the bottom wall of the forming cavity 41. The upper part of the forming cavity 41 has a riser structure with a diameter that gradually decreases from top to bottom. The lower part of the forming cavity 41 is a thin-walled cone that matches the shape of the titanium alloy casting to be poured. Specifically, the casting is poured using a top-pouring method, with risers set at the top to feed the top of the casting. The riser slope is set to 7-15 degrees. According to the casting structure, the gradient is reasonably set, and the overall flow channel design width varies from large to small, from 28mm to 9mm, to facilitate melt feeding and the formation of a sequential solidification sequence, preventing the formation of shrinkage defects.

[0068] Venting channels 43 are formed on the joint surface where the first mold block 44 and the second mold block 45 are joined, facilitating mold separation. Two sets of venting channels 43 are provided, located on opposite sides of the forming cavity 41. Casting holes 42 are formed on the third mold block 46, and the venting channels 43 communicate with the lower cavity 32 through through holes in the third mold block 46. In one specific example, 6-10 casting holes 42 are evenly distributed around the circumference of the forming cavity 41, with a hole diameter of 3-7 mm. The draft angle of the forming cavity 41 is set to 1-3 degrees to facilitate casting removal. Through these processes, after the overall casting process is completed, the casting can be easily removed from the mold, increasing the number of times the mold can be reused. This graphite mold can be reused 3-5 times.

[0069] It should be noted that the branch channel, which connects to the thin-walled conical sidewall of the forming cavity 41, slopes downwards at the end furthest from the venting channel 43 (the end connected to the forming cavity 41). This slows down the rate at which the casting material passes through the branch channel and blocks the venting channel 43, ensuring the venting channel 43 remains unobstructed until casting is complete. Specifically, the uppermost branch channel connects to the riser structure sidewall of the forming cavity 41. During actual casting, only the lower thin-walled conical portion of the forming cavity 41 needs to be filled, with a small amount of melt filling the riser structure (typically 60-80% of the volume of the forming cavity 41). The melt does not cover the uppermost branch channel. During this suction casting process, the resulting gas pressure may introduce some porosity defects to the top of the casting. The upwardly sloping branch channel at the upper end allows gas to escape more easily, reducing the risk of introducing porosity.

[0070] In one specific example, such as Figure 6 and 7 As shown, the lower part of the titanium alloy casting to be poured is a thin-walled conical structure, that is, the lower part of the casting is truncated cone-shaped, and its interior has a coaxial conical inner hole. The upper part of the titanium alloy casting to be poured is an inverted truncated cone-shaped (formed by the riser structure of the forming cavity 41). The inverted truncated cone shape of the upper part can be removed by subsequent machining.

[0071] Before casting, the graphite is machined into the shape of a pre-set mold 4 using a machining graphite mold process. After assembling the three mold blocks, the outermost part is bound with iron wire to enhance the stability of the mold and prevent the mold part from shifting and changing the shape and size of the casting during casting.

[0072] Example 2

[0073] This embodiment also provides a graphite mold casting process for titanium alloy castings, which is implemented using the graphite mold casting equipment for titanium alloy castings described in Embodiment 1, and includes the following steps:

[0074] Step 1: Place the titanium alloy raw material into the water-cooled copper crucible 2; place the mold 4 into the suction casting chamber 3 and degas the mold 4.

[0075] Step 1 specifically includes placing a plug, putting the titanium alloy raw material into the water-cooled copper crucible 2, placing the mold 4 into the suction casting chamber 3, closing the doors of the melting chamber 1 and the suction casting chamber 3, opening the connecting valve between the melting chamber 1 and the suction casting chamber 3, and degassing the mold 4. The degassing process specifically includes: using the suction casting pump 5 to evacuate the vacuum degree in the suction casting chamber 3 to less than or equal to 5 Pa, and using the mold heating device 12 (mainly composed of resistance wire and ceramic materials, capable of heating the mold below 1000℃, where 1000℃ is the limit temperature for resistance wire heating) to vacuum bake the mold 4 at a temperature of 900-1000℃ for 4-6 hours. Through negative pressure suction and vacuum baking, impurities on the surface and inside the mold are eliminated as much as possible.

[0076] In existing technologies, conventional degassing requires a vacuum degassing furnace followed by transferring the mold to a melting furnace for casting. During this transfer, the graphite mold still absorbs some gas upon contact with air. However, the in-situ heating device (mold heating device 12) in this solution integrates degassing, mold heating, and casting within a suspended melting furnace (casting equipment), avoiding the risk of gas adsorption during graphite mold transfer and thus improving product quality.

[0077] Step 2: Heat the mold 4 to the preset mold temperature, and at the same time evacuate the melting chamber 1 to the preset vacuum level. Inject protective gas into the melting chamber 1 through the protective gas injection device, and use the water-cooled copper crucible 2 to perform induction melting of the titanium alloy raw material until the titanium alloy raw material is melted to the preset casting temperature.

[0078] Step 2 specifically involves: using the mold heating device 12 to heat the mold 4 to a preset mold temperature (i.e., 400°C); simultaneously, opening the casting pump and casting valve to evacuate the melting chamber 1 to a preset vacuum level (i.e., a vacuum level less than 5 × 10⁻⁶). -30.03-0.07 MPa of protective gas (argon) is injected into the melting chamber 1 through a protective gas injection device. The connecting valve between the melting chamber 1 and the suction casting chamber 3 is closed. The titanium alloy raw material is induction melted using the water-cooled copper crucible 2 until the titanium alloy raw material is melted to the preset casting temperature.

[0079] Step 3: The melt flows out from the outlet of the water-cooled copper crucible 2 and passes through the liquid flow monitoring system 6. Based on the liquid flow information of the melt obtained by the liquid flow monitoring system 6, the pressure in the lower cavity 32 is drawn down to a level lower than that in the upper cavity 31 by the suction casting pump 5, and the ultrasonic vibration system 7 is turned on. Under the action of the pressure difference, the melt flows into the forming cavity 41 of the mold 4 to complete the filling of the titanium alloy casting. After cooling, the titanium alloy casting is obtained.

[0080] Step 3 specifically involves the secondary coil 10 melting the plug, causing the molten material to flow out of the outlet of the water-cooled copper crucible 2 and pass through the liquid flow monitoring system 6; based on the liquid flow information of the molten material obtained by the liquid flow monitoring system 6, the suction casting pump 5 and the suction casting valve are turned on, and the pressure in the lower cavity 32 is drawn down to a level lower than that in the upper cavity 31 by the suction casting pump 5 (specifically, the pressure in the lower cavity 32 is drawn down to a vacuum level below 10 Pa by the suction casting pump 5), and the ultrasonic vibration system 7 is turned on; under the action of the pressure difference, the molten material flows into the forming cavity 41 of the mold 4, completing the filling of the titanium alloy casting, and obtaining the titanium alloy casting after cooling.

[0081] The beneficial effects are as follows: Mold 4 undergoes in-situ degassing within the suction casting chamber 3, preventing the re-absorption of moisture and oxygen from the air during mold transfer. Simultaneously, mold degassing and differential pressure control significantly reduce the risk of gas entrapment, making the casting process more stable and suitable for mass production of thin-walled complex castings. Furthermore, melting and pouring in a protective gas environment prevents reactions with air, ensuring casting quality. The combination of negative pressure suction casting and ultrasonic vibration effectively breaks down dendrites, promotes melt flow and venting, thereby optimizing the solidification process immediately after filling, resulting in a final casting free of porosity and shrinkage cavities with a uniform microstructure. By employing appropriate temperature and pressure parameters, defects such as shrinkage cavities and porosity are controlled while achieving good filling, resulting in a blank casting free of shrinkage cavities. Subsequent heat treatment yields a casting with a uniform microstructure, meeting performance standards, and free of significant casting defects. This method is particularly suitable for the high-density forming of thin-walled conical castings.

[0082] In one specific example, the above process includes the following steps:

[0083] Place the titanium alloy raw material into the water-cooled copper crucible 2; put the mold 4 into the suction casting chamber 3, align the bottom boss of the mold with the lower cavity to reserve suction casting space, and perform degassing treatment on the mold 4.

[0084] The furnace body is evacuated, and the mold is heated using mold heating device 12 to reach the preset mold temperature of 400℃, while maintaining a vacuum level of less than 5×10⁻⁶. -3 Argon gas at 0.05 MPa is injected into the melting chamber 1 under Pa conditions, followed by induction melting and casting. When the melt reaches the preset casting temperature, the plug in the guide tube is heated and melted. The liquid flow monitoring system 6 is triggered the instant the titanium alloy melt flows down, thereby opening the suction casting valve and evacuating the lower cavity of the equipment to a vacuum degree below 10 Pa in advance, so as to create a pressure difference between the upper and lower cavities and reduce the gas inside the mold, thereby greatly reducing the risk of gas entrapment. At this time, the melt flows into the mold 4 under a certain gas pressure, completing the filling of the casting and obtaining the titanium alloy casting.

[0085] The following methods can be used to inspect the quality of titanium alloy castings:

[0086] After the casting cooled to room temperature, air was introduced into the furnace, the furnace door was opened, and the titanium alloy casting was removed. After hot isostatic pressing, samples were taken from three different locations on the titanium alloy casting to obtain its tensile strength, yield strength, and elongation. Then, wire cutting was performed on the parts of the casting most prone to defects and hot spots to observe the shrinkage cavities and porosity of the casting. No obvious macroscopic defects were found on the surface of the casting. X-ray flaw detection was performed to check for shrinkage cavities and porosity defects inside the casting. There were no gas pores or shrinkage cavities inside the casting, which met the quality requirements.

[0087] The hot isostatic pressing (HIP) process involves different parameters for different materials. For this material, the HIP process is carried out at a temperature of 900-1000℃ and a pressure of 100-120 MPa for 10-12 hours.

[0088] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0089] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0090] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0091] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0092] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A graphite mold casting equipment for titanium alloy castings, comprising a melting chamber (1), a suction casting chamber (3), a mold (4), a suction casting pump (5), a protective gas injection device, a sealing cylinder (11), and a water-cooled copper crucible (2) fixed in the melting chamber (1), wherein the suction casting chamber (3) is divided into an independent upper cavity (31) and a lower cavity (32) by a partition, the mold (4) is detachably installed on the partition, the mold (4) has a forming cavity (41), the upper and lower ends of the forming cavity (41) are respectively connected to the upper cavity (31) and the lower cavity (32), the outlet of the water-cooled copper crucible (2) is located directly above the forming cavity (41), the suction casting pump (5) is connected to the lower cavity (32), and the protective gas injection device is connected to the melting chamber (1), characterized in that, It also includes a liquid flow monitoring system (6) and an ultrasonic vibration system (7). The lower end of the melting chamber (1) is connected to the upper end of the upper cavity (31) through the liquid flow monitoring system (6). The ultrasonic vibration system (7) is fixedly installed in the lower cavity (32) and is detachably connected to the mold (4). The bottom of the forming cavity (41) is provided with multiple suction casting holes (42). The forming cavity (41) is connected to the lower cavity (32) through the suction casting holes (42). The mold (4) is also provided with an exhaust channel (43). The sidewall of the molding cavity (41) has multiple branch channels connected from top to bottom. The branch channels are connected to the sidewall of the molding cavity (41). The upper part of the molding cavity (41) has a riser structure. The uppermost branch channel is connected to the sidewall of the riser structure of the molding cavity (41) and the uppermost branch channel is inclined upward. The lower part of the molding cavity (41) is a cavity that matches the shape of the titanium alloy casting to be poured. The branch channel connected to the lower sidewall of the molding cavity (41) is inclined downward at the end away from the exhaust channel (43). The lower end of the exhaust channel (43) is connected to the lower cavity (32). The sealing cylinder (11) is a cylindrical shape that runs vertically through the mold cavity (41). The upper and lower ends of the sealing cylinder (11) are respectively sealed and connected to the lower end of the liquid flow monitoring system (6) and the upper end of the molding cavity (41). The ultrasonic vibration system (7) includes a vibration control system, a transducer (71) and a vibration ring (72) connected in sequence. The vibration control system transmits high-frequency electrical signals to make the transducer (71) convert electrical energy into high-frequency mechanical vibration, thereby driving the vibration ring (72) to vibrate. The lower end of the mold (4) is detachably inserted into the vibration ring (72). The mold (4) includes a semi-cylindrical first mold block (44), a semi-cylindrical second mold block (45), and a cylindrical third mold block (46). The first mold block (44) and the second mold block (45) are spliced ​​together to form a cylindrical main structure. The first mold block (44) and the second mold block (45) are connected on opposite sides by two first positioning pins. The third mold block (46) is installed below the cylindrical main structure. The joint position of the first mold block (44), the second mold block (45), and the third mold block (46) is positioned by setting a second positioning pin.

2. The graphite mold casting equipment for titanium alloy castings according to claim 1, characterized in that, It also includes a flow guide tube (8) that runs through the top and bottom. The upper end of the flow guide tube (8) is inserted into the outlet of the water-cooled copper crucible (2). A ceramic heat insulation tube (9) is sleeved on the outside of the flow guide tube (8). A secondary coil (10) is wound around the outside of the ceramic heat insulation tube (9). A plug (13) for sealing the flow guide tube (8) is placed on the upper end of the flow guide tube (8). The material of the plug (13) is the same as the casting material.

3. The graphite mold casting equipment for titanium alloy castings according to claim 1, characterized in that, The liquid flow monitoring system (6) includes a monitoring box (61) and a monitoring device (62). The upper and lower ends of the monitoring box (61) are respectively sealed and connected to the lower end of the melting chamber (1) and the upper end of the upper cavity (31). The monitoring device (62) is fixed to the side wall of the monitoring box (61) and is used to obtain liquid flow information in the monitoring box (61).

4. The graphite mold casting equipment for titanium alloy castings according to claim 1, characterized in that, A mold heating device (12) is also fixed on the partition plate, and the mold (4) can be detachably installed in the mold heating device (12).

5. A graphite mold casting process for titanium alloy castings, characterized in that, The process is achieved using a graphite mold casting equipment for titanium alloy castings as described in any one of claims 1-4, comprising the following steps: Step 1: Place the titanium alloy raw material into a water-cooled copper crucible (2); place the mold (4) into the suction casting chamber (3) and degas the mold (4); Step 2: Heat the mold (4) to the preset mold temperature, and at the same time draw the melting chamber (1) to the preset vacuum level. Inject protective gas into the melting chamber (1) through the protective gas injection device, and use the water-cooled copper crucible (2) to perform induction melting of the titanium alloy raw material until the titanium alloy raw material is melted to reach the preset casting temperature. Step 3: The melt flows out from the outlet of the water-cooled copper crucible (2) and passes through the liquid flow monitoring system (6); according to the liquid flow information of the melt obtained by the liquid flow monitoring system (6), the suction casting pump (5) is turned on, and the pressure in the lower cavity (32) is drawn down to a level lower than the pressure in the upper cavity (31) by the suction casting pump (5), and the ultrasonic vibration system (7) is turned on; the melt flows into the forming cavity (41) of the mold (4) under the action of the pressure difference, and the titanium alloy casting is completed. After cooling, the titanium alloy casting is obtained.

6. The graphite mold casting process for titanium alloy castings according to claim 5, characterized in that, In step 1, the degassing process specifically includes: using a suction casting pump (5) to evacuate the vacuum degree in the suction casting chamber (3) to less than or equal to 5 Pa, and vacuum baking the mold (4) at a temperature of 900 to 1000°C for 4 to 6 hours.

7. The graphite mold casting process for titanium alloy castings according to claim 5, characterized in that, In step 2, the preset mold temperature is 400℃; the preset vacuum degree is less than 5×10⁻⁶. -3 Pa; the protective gas is argon, and the pressure of the argon gas is 0.03-0.07 MPa; In step 3, the pressure in the lower cavity (32) is drawn down to a level lower than that in the upper cavity (31) by the suction casting pump (5). Specifically, the pressure in the lower cavity (32) is drawn down to a vacuum level of less than 10 Pa by the suction casting pump (5).

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