A method and equipment for bottomless casting in a vacuum furnace

Abstract

This invention discloses a method and equipment for dropless casting in a vacuum furnace, belonging to the field of high-purity aluminum vacuum smelting technology. The equipment includes a vacuum medium-frequency melting furnace, a graphite crucible, an aluminum tapping chute, a rotary chute, and a fixed chute. The graphite crucible is placed inside the cylindrical furnace body of the vacuum medium-frequency melting furnace. The upper end of the graphite crucible has an upper edge, on which a vertically penetrating notch is formed to create a flow channel. This flow channel sequentially connects to the aluminum tapping chute, a vacuum baffle valve, the rotary chute, and the fixed chute. During aluminum molten casting, the vacuum medium-frequency melting furnace body tilts, and the aluminum molten material in the graphite crucible flows out through the flow channel, then through the casting components to the crystallizer to complete dropless casting. This invention, through the structural design of the vacuum furnace with a dropless aluminum tapping chute and specific processes, can control the stability of the melt during melting and casting, avoiding gas and slag entrainment caused by melt drop and disturbance, ultimately achieving the preparation of high-quality, high-purity aluminum products with low gas and low slag.

Description

Technical Field

[0001] This invention relates to the field of high-purity aluminum vacuum smelting technology, specifically to a method and equipment for vacuum furnace casting with zero drop and dark flow. Background Technology

[0002] Vacuum smelting of high-purity aluminum refers to a smelting method that refines high-purity aluminum under air-isolated conditions (below atmospheric pressure) to improve product purity. This method is widely used in the smelting industry, and various forms of vacuum metallurgical equipment and technologies exist on the market. Common vacuum smelting methods involve direct casting within a vacuum chamber, known in the industry as a VIM furnace (Vacuum Induction Melting Furnace). However, the internal microstructure and dimensions of the metal ingots cast in a VIM furnace are limited, resulting in certain limitations. It cannot be used with complex crystallizer designs.

[0003] A VIDP (Vacuum Induction Degassing and Pouring Furnace) is a compact vacuum melting furnace. In a VIDP furnace, only the melting furnace to the aluminum tapping chute is under vacuum; the section from the chute to the final forming crystallizer is not. The VIDP furnace volume is only 5%-10% of a VIM furnace volume, significantly reducing the investment in vacuum control equipment and facilitating the subsequent integration of complex product forming devices, leading to its widespread application.

[0004] After aluminum exits the VIDP furnace chute, the high-temperature molten aluminum immediately comes into contact with air. Therefore, the aluminum exiting the chute from the smelting furnace must achieve zero drop, meaning zero drop from the smelting furnace to the chute. When molten aluminum is poured into the chute with a drop, the oxide scale on the surface of the aluminum is destroyed. Upon contact with air, the surface of the melt rapidly oxidizes, forming an oxide scale. Furthermore, the turbulent and agitated process of the molten aluminum falling like a waterfall carries oxide slag into the interior of the molten aluminum, increasing the gas and slag content inside the melt and significantly reducing product quality. Smoothly releasing the molten metal from the smelting furnace to the chute and finally to the forming crystallizer is key to controlling the gas and slag content inside the ingot.

[0005] Patent CN201821883483.4 (A Vacuum Induction Melting Furnace Equipment for Zero-Drop Vertical Casting) discloses a zero-drop casting device for a vacuum melting furnace. The vacuum induction melting furnace structure includes a tilting support, a vacuum cylinder, an induction furnace installed inside the vacuum cylinder, and supporting vacuum, hydraulic, and electrical control systems. The vacuum cylinder is a vertical cylinder structure; the vacuum-sealed furnace cover is equipped with a vacuum bell device and observation holes; the inner lining of the furnace cover is lined with high-temperature resistant insulation material; a coreless induction furnace of various frequencies operates in a vacuum environment; a chute liquid level detection device is connected to the electrical control system; the vacuum unit consists of a slide valve pump and a Roots pump; the hydraulic system includes a hydraulic station and hydraulic cylinders, which are located on both sides of the furnace body, and a proportional valve is also installed on the hydraulic system. The design concept of this scheme is zero-drop casting. However, the outer edge of the chute is tangent to the outer edge of the furnace body, meaning the height of the melt from the chute inside the furnace is the crucible wall thickness + the furnace body insulation material thickness + 1 / 2 the chute radius. The drop of the molten metal from the furnace body to the flow channel can exceed 500mm, and in actual application, it will still cause aluminum liquid to be poured overturned and disturbed.

[0006] Patent CN201210283473.8 (A Multi-Purpose Semi-Continuous Vacuum Induction Casting Furnace) discloses a multi-purpose semi-continuous vacuum induction casting furnace, including a melting chamber. The melting chamber is characterized by a continuous feeding device and an alloy feeding port at its upper part. An induction heating crucible device is located within the melting chamber, with a liquid outlet. A chute is located on the side of the liquid outlet of the induction heating crucible device. A casting chamber is located below the chute, and an ingot mold is located within the casting chamber. An ingot mold carriage is located below the ingot mold. The two chutes at both ends can correspond to different casting molds, achieving multi-purpose use. This technical solution does not explicitly describe the structural design of the aluminum flow channel and the furnace body, and lacks a technical solution for casting without drop height.

[0007] Patent CN201921157721.8 (Vacuum Induction Melting Furnace) discloses a side-entry short chute system for a vacuum induction furnace. The short chute system is a vacuum chamber; observation windows are provided at the top of the vacuum chamber and the chute; a water-cooled vacuum isolation valve has an inspection port at the top; the chute chamber is a double-layer carbon steel structure; and the push rod is coaxially arranged with the chute chamber. In this design, the contact design between the short chute and the furnace body indicates that the drop height during aluminum pouring equals the crucible wall thickness + furnace insulation material thickness + chute diameter. However, in practical applications, this drop height will still cause disturbance and slagging of the aluminum liquid. Summary of the Invention

[0008] To address the aforementioned shortcomings in the existing technology, the present invention aims to provide a method and equipment for vacuum furnace casting without drop height. By controlling the stable state of the melt during the smelting and casting process through the structural design of the vacuum furnace with a drop-height aluminum discharge chute, the selection of materials for the aluminum discharge chute, the addition of alloys, and the inert gas protection during casting, the method avoids the entrapment of gas and slag caused by melt drop height and disturbance, and ultimately achieves the preparation of high-quality, high-purity aluminum products with low gas and low slag.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A device for bottomless casting in a vacuum furnace includes a vacuum intermediate frequency melting furnace, a graphite crucible, and a casting assembly. The casting assembly includes an aluminum discharge chute, a rotating chute, and a fixed chute. The graphite crucible is placed inside the cylindrical furnace body of the vacuum intermediate frequency melting furnace. The upper end of the graphite crucible has an upper edge, on which a vertical through-hole forms a flow channel, which is connected to the aluminum discharge chute. The end of the aluminum discharge chute is then connected in sequence to a vacuum baffle valve, a rotating chute, and a fixed chute. During aluminum molten casting, the vacuum intermediate frequency melting furnace body tilts, and the aluminum molten material in the graphite crucible flows out through the flow channel, then through the casting assembly until it reaches the crystallizer to complete bottomless casting.

[0011] The vacuum intermediate frequency melting furnace has a matching induction coil between the furnace body and the graphite crucible. The outside of the graphite crucible is covered with heat-insulating material to separate it from the induction coil. The bottom of the graphite crucible is filled with crucible bottom filler between the bottom of the graphite crucible and the bottom of the furnace body. The top of the furnace body is covered with a furnace body cover, which has an air inlet and an air outlet.

[0012] A rotating shaft is fixedly connected to the upper side of the furnace body, and the rotating shaft causes the furnace body to tilt when it rotates.

[0013] The graphite crucible has a liquid flow channel on its upper edge, the inner side of which is connected to the inner side of the graphite crucible, and the center of the liquid flow channel is located on the axis of the aluminum discharge chute; the axes of the aluminum discharge chute, the rotating chute, and the fixed chute coincide.

[0014] The graphite crucible is made of high-purity graphite, the bottom filler of the crucible is refractory powder, and the upper edge of the crucible is made of refractory material.

[0015] The aluminum discharge chute passes through a rotating shaft and is connected to a rotating chute via a vacuum baffle valve. During aluminum smelting, the vacuum baffle valve is closed to maintain a vacuum environment. During aluminum molten metal casting, the vacuum baffle valve is opened to allow the aluminum molten metal to flow into the rotating chute and the fixed chute.

[0016] The rotary chute is a hollow tube that can rotate relative to the fixed chute after being connected. When the aluminum molten metal is poured, the rotating shaft on the furnace body drives the furnace body to tilt, which in turn drives the aluminum discharge chute and the rotary chute to rotate, while the fixed chute remains stationary. Both the rotary chute and the fixed chute are equipped with sealing covers at the top.

[0017] The upper part of the liquid flow channel is equipped with a flow channel cover, which is an integral structure with the liquid flow channel. The function of the flow channel cover is to ensure that the molten aluminum flows smoothly out of the liquid flow channel when the graphite crucible tilts along the rotating axis, without splashing or spilling out from the position of the flow channel cover, thus preventing safety risks and preventing molten aluminum from overflowing during the casting process. The axis of the aluminum discharge chute is tangent to the outer circle of the graphite crucible, which can ensure that the melt is completely poured out and avoid molten aluminum residue inside the crucible.

[0018] The lining material of the aluminum discharge chute, rotary chute and fixed chute is a refractory material, wherein the content of Al2O3 in the refractory material is >90wt.%, the content of SiO2 is <2wt.%, and the content of P2O5 is <2wt.%.

[0019] The method for vacuum furnace casting without drop in depth using the aforementioned equipment includes the following steps:

[0020] (1) Vacuum melting of aluminum: Add high-purity aluminum ingot raw material to graphite crucible, preheat the rotary chute and fixed flow channel, the preheating temperature is ≥750℃, and the preheating time is ≥6h; the vacuum melting furnace is sealed and heated at the same time, and vacuum is drawn until the vacuum degree of the furnace body is <10Pa; adjust the power of the medium frequency furnace to completely melt the aluminum ingot.

[0021] (2) Addition of alloying elements: Adjust the medium frequency power to raise the temperature of the aluminum liquid to 760-800℃, and add the required alloying element raw materials to the graphite crucible in batches or multiple times through the alloying addition device installed on the furnace cover; the required alloying element raw materials are added in the form of elemental particles or intermediate alloys, and the rotor is turned on to stir at the same time to make the melt composition uniform; when the alloying elements are added in the form of particles, the particle size is <10mm; when the alloying elements are added in the form of intermediate alloys, the size of the intermediate alloy block sample is less than 50mm; the added alloying elements are metals such as copper, silicon, and iron;

[0022] (3) Inert gas protection: After the alloying elements are added, adjust the medium frequency power to cool the aluminum liquid to 710-730℃; introduce high-purity argon gas through the gas inlet of the vacuum furnace cover. The O2 content in the high-purity argon gas is ≤0.2ppm, and the dew point of the purified water of argon gas is ≤-80℃. Open the gas outlet at the top of the vacuum furnace cover.

[0023] (4) Furnace refining and degassing: Turn on the rotor stirring to refine the aluminum liquid. After refining, raise the stirring rotor and check that the aluminum liquid temperature is 720-730℃. Prepare for aluminum liquid casting.

[0024] (5) Aluminum liquid casting: After the vacuum baffle valve connected to the aluminum flow channel of the vacuum furnace is opened, the rotating chute and the fixed chute are connected, the rotating shaft of the vacuum furnace is tilted, and the aluminum liquid begins to be cast through the flow channel; the aluminum liquid level is stable during the casting process, the oxide scale on the upper part of the aluminum liquid in the furnace is intact, and the aluminum liquid is cast in the dark.

[0025] The advantages and beneficial effects of this invention are as follows:

[0026] 1. The induction furnace tilting rotation axis and the center line of the rotating casting outlet device of the present invention are located on the same axis, and the aluminum outlet channel on the same side is tangent to the outer circle of the graphite crucible, realizing the method of horizontal dark flow casting without drop. The tilting of the induction furnace can smoothly rotate the melt out of the furnace and realize stable liquid level control, that is, realize the discharge without drop and stable control of the casting liquid level.

[0027] 2. The rotary casting outlet device of the present invention is equipped with a specially designed dual-purpose vacuum baffle valve, which is mainly used to maintain the vacuum level in the induction furnace. During the melting stage, the specially designed dual-purpose vacuum baffle valve is used to disconnect the casting outlet to maintain the vacuum requirement. During casting, the aluminum liquid flow channel of the rotary casting outlet device can be quickly opened to achieve the requirements of venting casting.

[0028] 3. The composition ratio design of the lining materials of the side aluminum discharge chute, rotating chute and fixed flow channel of the equipment of the present invention can meet the requirements of high-purity aluminum smelting and casting, and avoid the contamination of silicon and phosphorus elements in the high-purity aluminum smelting and casting process.

[0029] 4. The process design of high-purity aluminum vacuum melting + inert gas protection in this invention can reduce the contact area between molten aluminum and air during the melting and casting process, thereby reducing the gas content in the molten aluminum. Furthermore, the compact melting furnace design facilitates the customized design of the end-forming crystallizer, enabling the melting and forming of high-purity, high-quality aluminum ingots. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the longitudinal section of the graphite crucible and the aluminum discharge chute in the vacuum furnace aluminum discharge device with no drop and dark flow according to the present invention.

[0031] Figure 2 This is a schematic diagram of the longitudinal section of the graphite crucible and the aluminum discharge chute in the vacuum furnace aluminum discharge device with no drop and dark flow according to the present invention.

[0032] Figure 3 This is a top view of the graphite crucible and aluminum outlet chute in the vacuum furnace aluminum outlet equipment with no drop and dark flow according to the present invention.

[0033] Figure 4 This is a schematic diagram of the three-dimensional structure of the graphite crucible and aluminum discharge chute in the vacuum furnace aluminum discharge device with no drop and dark flow according to the present invention.

[0034] Figure 5This is a schematic diagram of the overall structure of the vacuum furnace aluminum discharge device with no drop and dark flow according to the present invention.

[0035] In the figure: 1. Crucible bottom filler; 2. Crucible upper edge; 3. Graphite crucible; 4. Furnace body; 5. Aluminum tapping chute; 6. Liquid flow channel; 7. Flow channel cover; 8. Fixed chute; 9. Rotary chute; 10. Vacuum baffle valve; 11. Rotary shaft. Detailed Implementation

[0036] To further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0037] This invention, based on the VIDP melting furnace structure, provides a method and apparatus for the seamless, bottomless flow of aluminum in a vacuum furnace. For example... Figure 1-5 As shown, the vacuum furnace casting equipment for seamless casting provided by this invention includes a vacuum intermediate frequency melting furnace, a graphite crucible 3, and a casting assembly. The casting assembly includes an aluminum discharge chute 5, a rotating chute 9, and a fixed chute 8. The graphite crucible 3 is placed inside the cylindrical furnace body 4 of the vacuum intermediate frequency melting furnace. The upper end of the graphite crucible has a crucible upper edge 2 made of refractory material. A vertical through-hole is formed on the crucible upper edge 2 to create a liquid flow channel 6, which is connected to the aluminum discharge chute 5. The end of the aluminum discharge chute 5 is then connected in sequence to a vacuum baffle valve 10, the rotating chute 9, and the fixed chute 8. During aluminum molten casting, the vacuum intermediate frequency melting furnace body 4 tilts, and the aluminum molten material in the graphite crucible flows out through the liquid flow channel 6, then through the casting assembly until it reaches the crystallizer to complete seamless casting.

[0038] The furnace body 12 of the vacuum intermediate frequency melting furnace is provided with a matching induction coil between the furnace body and the graphite crucible. The outside of the graphite crucible is provided with heat-insulating material to separate it from the induction coil. The bottom of the graphite crucible and the bottom of the furnace body are filled with crucible bottom filler 1, which is refractory powder. The top of the furnace body is provided with a furnace body cover, which is provided with conventional air inlet, air outlet and alloy adding device.

[0039] A rotating shaft 11 is fixedly connected to the upper side of the furnace body. When the rotating shaft 11 rotates, it causes the furnace body to tilt. A liquid flow channel 6 is opened on the upper edge of the graphite crucible. The inner side of the liquid flow channel 6 is connected to the inner side of the graphite crucible. The center of the liquid flow channel 6 is located on the axis of the aluminum discharge chute 5. The axes of the aluminum discharge chute 5, the rotating chute 9, and the fixed chute 8 coincide.

[0040] The aluminum discharge chute 5 is installed on the rotating shaft 11 and connected to the rotating chute 9 through the vacuum baffle valve 10. When aluminum is smelted, the vacuum baffle valve 10 is closed to maintain a vacuum environment. When aluminum melt is poured, the vacuum baffle valve 10 is opened to allow the aluminum melt to flow into the rotating chute 9 and the fixed chute 8.

[0041] The rotating chute 9 is a hollow tube. After the rotating chute 9 is connected to the fixed chute 8, it can rotate relative to each other. When the aluminum melt is poured, the rotating shaft on the furnace body drives the furnace body to tilt, which simultaneously drives the aluminum discharge chute 5 and the rotating chute 9 to rotate, while the fixed chute 8 remains stationary. Both the rotating chute and the fixed chute have sealing covers on their upper parts.

[0042] The upper part of the liquid flow channel 6 is equipped with a flow channel cover 7, which is an integral structure with the liquid flow channel 6. The function of the flow channel cover 7 is to ensure that the molten aluminum flows smoothly out of the liquid flow channel 6 when the graphite crucible 3 is tilted along the rotating shaft 11, without splashing or spilling out from the position of the flow channel cover 7, thus preventing safety risks and preventing molten aluminum from overflowing during the casting process. The axis of the aluminum discharge chute is tangent to the outer circle of the graphite crucible, so that there is no liquid level difference between the melting furnace and the aluminum discharge chute, and the aluminum flows out horizontally without any liquid level difference. This avoids the molten metal from turning over and being disturbed when falling, which would cause the molten metal to overheat and the slag content to increase, affecting product quality. At the same time, it can ensure that the molten metal is completely poured out, avoiding the residue of molten aluminum inside the crucible.

[0043] To adapt to the use of high-purity aluminum smelting and avoid contamination of the aluminum composition by materials in contact with the molten aluminum during the process, the crucible is made of high-purity graphite. The lining material of the aluminum discharge chute, rotary chute, and fixed chute is made of refractory material. The refractory material contains Al2O3 content >90wt.%, SiO2 content <2wt.%, and P2O5 content <2wt.%. High SiO2 and P2O5 content will cause the Si and P content in the melt during the high-purity aluminum casting process to increase, resulting in a decrease in the purity of the high-purity aluminum.

[0044] Example 1:

[0045] This embodiment demonstrates the use of the aforementioned equipment for dropless, undercurrent casting, as detailed below:

[0046] 1. Vacuum Aluminization: Add 900 kg of high-purity aluminum ingot raw material to a graphite crucible. Preheat the rotary chute and fixed flow channel to 760℃ for 8 hours. Simultaneously, begin vacuuming the vacuum furnace while simultaneously heating it until the furnace vacuum reaches 2 Pa. Adjust the medium-frequency power to begin melting the raw material. Observe through the observation hole that the aluminum ingot has completely melted, and measure the temperature of the molten aluminum to be 702℃.

[0047] 2. Alloy Addition: Adjust the medium-frequency power to raise the temperature of the molten aluminum to 780℃, and add copper particles using an alloy adding device. The particles are 9mm in diameter and 15mm in length. Lower the stirring rotor into the molten aluminum, turn on the stirring rotor, and add the copper particles simultaneously. All 4.6kg of copper particles were added in three stages. The pre-mixed alloy ratio was 0.508wt%, and the actual measured alloy composition was 0.51wt%, meeting the control standard. After the alloy addition was completed, the temperature of the molten aluminum was measured to be 752℃.

[0048] 3. Inert gas protection: Adjust the medium-frequency power to cool the molten aluminum to 720℃. Introduce 99.9999% pure high-purity argon gas through the inlet of the vacuum furnace cover. The O2 content in the high-purity argon gas is 0.05ppm, and the dew point of the purified water is -83.0℃. Open the outlet at the top of the vacuum furnace cover.

[0049] 4. In-furnace refining and degassing: High-purity argon gas is introduced through the upper air inlet of the stirring rotor, while the rotor is simultaneously activated to refine the molten aluminum. After refining, the stirring rotor is raised. The temperature of the molten aluminum is checked and found to be 725℃, ready for casting.

[0050] 5. Aluminum Molten Casting: After the vacuum seal of the aluminum flow channel from the vacuum furnace is opened and the rotating chute and fixed chute are connected, the vacuum furnace tilts along the rotation axis of the graphite crucible's outer edge center line, and the aluminum molten metal begins casting through flow channel 6. During the casting process, the aluminum molten metal level remains stable, the oxide scale on the upper part of the aluminum molten metal in the furnace remains intact, and the aluminum molten metal is poured using a dark flow method.

[0051] 6. Hydrogen content detection: The hydrogen content in the molten aluminum was detected online at a fixed chute and found to be 0.08 ml / 100gAl.

[0052] Comparative Example 1:

[0053] Steps 1-2 are the same as in Example 1.

[0054] 3. The argon gas used for sealing and refining has a purity of 99.99% and an O2 content of 20 ppm.

[0055] Steps 4-5 are the same as in Example 1.

[0056] 6. Hydrogen content detection: The hydrogen content in the molten aluminum was detected online at a fixed chute and found to be 0.15 ml / 100 g Al.

[0057] Comparative Example 2:

[0058] Step 1 is the same as in Example 1.

[0059] 2. Adjust the medium-frequency power to raise the temperature of the molten aluminum to 778℃, and add copper particles using the alloy adding device. The particles are 9mm in diameter and 15mm in length. Lower the stirring rotor into the molten aluminum, turn on the stirring rotor, and add the copper particles simultaneously. All 4.6kg of copper particles were added at once. The pre-mixed alloy ratio was 0.508wt%, and the actual measured alloy composition was 0.432wt%. The alloy composition did not meet the control standard, indicating that the added copper alloy was not completely melted. Adjust the medium-frequency power to raise the temperature of the molten aluminum to 820℃, and simultaneously turn on the stirring rotor for 30 minutes. After stirring, take a sample and test the alloy composition, which was 0.498wt%, meeting the composition control standard.

[0060] Steps 3-5 are the same as in Example 1.

[0061] In this example, without the use of a multi-stage addition process, the alloy melting time is prolonged, increasing the risk of alloy component contamination.

Claims

1. A device for vacuum furnace-based non-drop underflow casting, characterized in that: The equipment includes a vacuum intermediate frequency melting furnace, a graphite crucible, and a casting assembly. The casting assembly includes an aluminum discharge chute, a rotary chute, and a fixed chute. The graphite crucible is placed inside the cylindrical furnace body of the vacuum intermediate frequency melting furnace. The upper end of the graphite crucible has an upper edge, and a vertically penetrating notch is formed on the upper edge to create a liquid flow channel, which is connected to the aluminum discharge chute. The end of the aluminum discharge chute is then connected in sequence to a vacuum baffle valve, a rotary chute, and a fixed chute. During aluminum molten casting, the vacuum intermediate frequency melting furnace body tilts, and the aluminum molten material in the graphite crucible flows out through the liquid flow channel, then through the casting assembly until it reaches the crystallizer to complete the dropless casting process. A rotating shaft is fixedly connected to the upper side of the furnace body, and the rotating shaft causes the furnace body to tilt when it rotates. A liquid flow channel is provided on the upper edge of the graphite crucible, and the inner side of the liquid flow channel is connected to the inner side of the graphite crucible. The center of the liquid flow channel is located on the axis of the aluminum discharge chute. The axes of the aluminum discharge chute, the rotating chute and the fixed chute coincide. The aluminum discharge chute passes through the rotating shaft and is connected to the rotating chute via a vacuum baffle valve. During aluminum smelting, the vacuum baffle valve is closed to maintain a vacuum environment. During aluminum molten casting, the vacuum baffle valve is opened to allow the aluminum molten material to flow into the rotating chute and the fixed chute. The rotary chute is a hollow tube that can rotate relative to the fixed chute after being connected. When the aluminum molten metal is poured, the rotating shaft on the furnace body drives the furnace body to tilt, and simultaneously drives the aluminum discharge chute and the rotary chute to rotate, while the fixed chute remains stationary. Both the rotary chute and the fixed chute are equipped with sealing covers at the top. The upper part of the liquid flow channel is provided with a flow channel cover to prevent aluminum liquid from overflowing during the casting process; the axis of the aluminum discharge chute is tangent to the outer edge of the graphite crucible.

2. The equipment for vacuum furnace casting without drop height as described in claim 1, characterized in that: The vacuum intermediate frequency melting furnace is equipped with a matching induction coil between the furnace body and the graphite crucible. The graphite crucible is provided with heat-insulating material on the outside to separate it from the induction coil. The bottom of the graphite crucible is filled with crucible bottom filler between the bottom of the graphite crucible and the bottom of the furnace body. The top of the furnace body is equipped with a furnace body cover, which has an air inlet and an air outlet.

3. The equipment for vacuum furnace casting without drop height as described in claim 2, characterized in that: The graphite crucible is made of high-purity graphite, the bottom filler of the crucible is refractory powder, and the upper edge of the crucible is made of refractory material.

4. The equipment for vacuum furnace casting without drop height as described in claim 1, characterized in that: The lining material of the aluminum discharge chute, rotary chute and fixed chute is a refractory material, wherein the content of Al2O3 in the refractory material is >90wt.%, the content of SiO2 is <2wt.%, and the content of P2O5 is <2wt.%.

5. A method for vacuum furnace casting without drop in depth using the equipment described in any one of claims 1-4, characterized in that: The method includes the following steps: (1) Vacuum melting of aluminum: Add high-purity aluminum ingot raw material to graphite crucible, preheat the rotary chute and fixed flow channel, the preheating temperature is ≥750℃, and the preheating time is ≥6h; the vacuum melting furnace is sealed and heated at the same time, and vacuum is drawn until the vacuum degree of the furnace body is <10Pa; adjust the power of the medium frequency furnace to completely melt the aluminum ingot. (2) Addition of alloying elements: Adjust the medium frequency power to raise the temperature of the aluminum liquid to 760-800℃, and add the required alloying element raw materials to the graphite crucible in batches or multiple times through the alloying addition device installed on the furnace cover; the required alloying element raw materials are added in the form of single particles or intermediate alloys, and the rotor is turned on to stir at the same time to make the melt composition uniform; when the alloying element is added in the form of particles, the particle size is <10mm; when the alloying element is added in the form of intermediate alloys, the size of the intermediate alloy block sample is less than 50mm; the added alloying element is copper, silicon or iron; (3) Inert gas protection: After the alloying elements are added, adjust the medium frequency power to cool the aluminum liquid to 710-730℃; introduce high-purity argon gas through the gas inlet of the vacuum furnace cover. The O2 content in the high-purity argon gas is ≤0.2ppm, and the dew point of the purified water of argon gas is ≤-80℃. Open the gas outlet at the top of the vacuum furnace cover. (4) In-furnace refining and degassing: Turn on the rotor to stir and refine the aluminum liquid. After refining, raise the stirring rotor and check that the temperature of the aluminum liquid is 720-730℃. Prepare for aluminum liquid casting. (5) Aluminum liquid casting: After the vacuum baffle valve connected to the aluminum flow channel of the vacuum furnace is opened, the rotating chute and the fixed chute are connected, the rotating shaft of the vacuum furnace is tilted, and the aluminum liquid begins to be cast through the flow channel; the aluminum liquid level is stable during the casting process, the oxide scale on the upper part of the aluminum liquid in the furnace is intact, and the aluminum liquid is cast in the dark.

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