A casting method for low-segregation fine-grained ingots of high-melting-point metals

Abstract

The application relates to the technical field of ingot casting, in particular to a casting method of a low-segregation fine-grain ingot of high-melting-point metal, which comprises the following steps: S1: melting and heat preservation; S2: height adjustment and rotation starting; S3: flow guiding and cloth rotating and temperature uniformizing; S4: lifting and continuous casting: after the start of the casting, the metal rod is lifted at a slow speed while maintaining rotation, and the rotating torque M of the metal rod is continuously measured; if M is greater than or equal to F, the metal rod is lifted, the PLC controls the continuous tilting of the melting pot, the tilting degree matches the lifting height, the metal melt in the melting pot flows into the mold along the metal rod, the amount of the metal melt in the mold is kept consistent, and the ingot is formed until the forming of the ingot is completed; and S5: arc starting and temperature supplementing. The designed casting method of the low-segregation fine-grain ingot of high-melting-point metal improves the temperature and the uniformity of the composition in the ingot casting process through flow guiding, heat conduction and stirring of the metal rod, and a low-segregation ingot mainly composed of fine equiaxed crystals can be obtained.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ingot casting, in particular to a casting method of a low-segregation fine-grain ingot of high-melting-point metal. BACKGROUND

[0002] At present, for special alloys and rare and precious metals and other materials, many ingots are still produced by casting method; the ingot is manufactured by pouring the molten metal into a permanent or reusable mold; the ingot can be further machined into various new shapes; the ingot is a cast structure, and in the stable state, the metal grows in a dendritic manner in the traditional casting, and composition segregation and coarse columnar crystals are prone to occur in the solidification process.

[0003] The segregation is mainly caused by the solute redistribution of the alloy in the solidification process, the columnar crystal solidification segregation is obvious, and the fine equiaxed crystal solidification can improve the segregation. The segregation in the solidification structure can be extremely low by keeping the un-solidified melt at a lower and controllable state and rapidly solidifying with the aid of mechanical stirring.

[0004] The patent document with the application number 201711302710.X discloses a melt electromagnetic stirring type low-pressure casting device and a casting method, which comprises a melting furnace, a crucible, a sealing ring, an air inlet and exhaust and pressure signal interface, a cover plate, a vacuum air source and an electric control pneumatic stop valve; further comprising a side strong magnet, a bottom strong magnet and a variable frequency power supply; the side strong magnet is located around the melting furnace, the bottom strong magnet is the bottom of the melting furnace, and the two strong magnets are electrically connected with the variable frequency power supply; the side strong magnet and the bottom strong magnet adopt a coil structure.

[0005] For the related technology in the above, the inventors believe that the melt electromagnetic stirring type low-pressure casting device and the casting method designed by the inventors drive the metal liquid in the melting furnace to move in the form of electromagnetic stirring, but the penetration depth of the electromagnetic stirring is limited by the skin effect of the induced current, the effect of the electromagnetic stirring on the metal liquid in the middle region of the melting furnace is extremely small, the temperature equalization effect of the metal liquid in the middle region of the melting furnace is poor, and the forming quality of the ingot is affected. SUMMARY

[0006] In order to improve the forming quality of the ingot, the application provides a casting method of a low-segregation fine-grain ingot of high-melting-point metal, which adopts the following technical scheme:

[0007] A casting method of a low-segregation fine-grain ingot of high-melting-point metal, comprising

[0008] S1: melting and heat preservation: heating the solid metal to form a metal melt, and keeping the temperature of the metal melt above the melting point at all times;

[0009] S2: Height Adjustment and Rotation Start: A metal rod is placed coaxially 5-20mm above the bottom wall of the forming cavity of the mold to drive the metal rod to rotate; the metal rod is made of the same material as the molten metal and is coaxial with the mold.

[0010] S3: Flowing and Spinning for Temperature Equalization: The molten metal obtained in step S1 flows into the forming cavity of the mold along the metal rod until the lower end of the metal rod is submerged in the molten metal in the mold for 5-15mm, and the molten metal in the mold is driven to flow by rotation.

[0011] S4: Lifting the rod and continuous casting: Set the lifting torque F and continuously measure the rotational torque M of the metal rod. If M < F, make the metal rod rise at a basic speed of 1-3 mm / s while continuously rotating. If M ≥ F, lift the metal rod 5-10 mm. During the process, control the molten metal obtained in step S1 to continuously flow into the mold along the metal rod at a matching speed so that the amount of molten metal in the mold remains consistent. The metal rod is always inserted into the molten metal until the ingot is formed.

[0012] By adopting the above technical solution, the solid metal is first heated until it is completely melted to form a molten metal. The temperature of the molten metal is then maintained above its melting point to keep it in a liquid state. A metal rod is coaxially positioned 5-20 mm above the bottom wall of the mold and driven to rotate. The molten metal obtained in step S1 flows along the metal rod into the forming cavity of the mold. During the flow of the molten metal into the mold, some heat is transferred to the outside through the metal rod. The rotating metal rod, through strong stirring, breaks up the primary dendrites in the molten metal within the mold and provides a large number of nuclei to generate fine equiaxed crystals. Furthermore, the strong stirring can homogenize the alloy composition in the molten metal and reduce segregation. Simultaneously, as the metal rod rotates, the hotter molten metal, due to its lower viscosity, is thrown closer to the inner wall of the mold cavity, where cooling capacity is strong. The colder molten metal, due to its higher viscosity, falls closer to the center of the mold, where cooling capacity is weak. Under the rotation of the metal rod, the difference in cooling capacity between the central and edge regions in the horizontal direction is reduced. Simultaneously, the metal rod bears part of the heat dissipation of the molten metal in the central region of the mold, further reducing the difference in cooling rate between the central and edge regions. A lifting torque F is set, and the rotational torque M of the metal rod is continuously measured during its rotation. When the solidified structure in the central region of the mold approaches the end of the metal rod, the rotational torque M of the metal rod increases significantly. If the rotational torque M of the metal rod is less than the set lifting torque F, the metal rod rises at a lower basic speed and maintains rotation. If the rotational torque M of the metal rod is greater than or equal to the set lifting torque F, the metal rod is lifted 5-10 mm from the mold. Simultaneously, the molten metal obtained in step S1 is controlled to continuously flow into the mold along the metal rod at a matching speed, ensuring that the amount of molten metal in the mold remains consistent until the entire ingot is formed. During the entire casting process, the metal rod rises at a lower speed, and the casting continues uninterrupted to avoid possible stratification during solidification, thus obtaining a continuous and complete ingot.

[0013] The designed casting method for low-segregation, fine-grained ingots of high-melting-point metals has the following advantages: First, the rotation of a metal rod ensures uniform and controllable solidification of the molten metal within the mold in both time and space. Second, the solidification status of the molten metal within the mold can be directly sensed by measuring the rotation torque of the metal rod, thereby controlling the casting speed accordingly. Third, the strong stirring of the metal rod breaks up primary dendrites and refines the grains, improving segregation. Fourth, the flow-guiding effect of the metal rod reduces splashing of the molten metal during casting. Fifth, continuous casting with controlled flow facilitates rapid solidification of the molten metal to obtain a fine-grained structure. Sixth, the heat conduction and rotation of the metal rod further reduce the cooling rate difference between the central and edge regions of the molten metal, improving ingot quality. Seventh, the method is simple in structure and low in cost.

[0014] Optional, also includes

[0015] S5: Arc Initiation and Temperature Compensation: After all the molten metal is poured into the mold, control the metal rod to be raised to 5-10mm above the surface of the molten metal and stop rotating. Power is supplied to the metal rod so that an electric arc is formed between the lower end of the metal rod and the surface of the molten metal to delay the solidification of the liquid surface.

[0016] By adopting the above technical solution, after all the molten metal obtained in step S1 is poured into the forming cavity of the mold, the casting of the ingot enters the final stage. At this time, the heat dissipation rate of the top of the molten metal in the mold is relatively fast. In order to avoid the top area of ​​the ingot solidifying too early and forming a solid shell, the metal rod is raised to 5-10mm above the molten metal surface and power is supplied to the metal rod so that an electric arc is formed between the lower end of the metal rod and the molten metal. The electric arc discharge provides heat replenishment for the top of the molten metal surface to delay the solidification of the surface shell. The designed step S5 can avoid the formation of shrinkage cavities inside due to the rapid solidification of the top of the molten metal during the casting final stage.

[0017] Optionally, the metal rod is configured as a hollow tube.

[0018] By adopting the above technical solution, the metal rod designed as a hollow tube can control its own heat dissipation effect and the ability to spin molten metal, thus avoiding premature solidification of the molten metal in the center area of ​​the mold due to excessive heat dissipation and cooling capacity of the metal rod.

[0019] Optionally, the mold includes a water-cooled metal mold section and a ceramic mold section, the water-cooled metal mold section and the ceramic mold section are coaxially arranged, and the water-cooled metal mold section is located below the ceramic mold section.

[0020] By adopting the above technical solution, the mold is designed with segmentation to reduce the heat dissipation rate at the top during the later stage of pouring, thereby flattening the liquidus line in the final stage of metal molten solidification.

[0021] Optionally, steps S1-S4 are all performed under a pressure of 40-60 Pa.

[0022] By adopting the above technical solution, the S1-S4 steps designed to be carried out under a gas pressure of 40-60Pa can reduce the splashing of molten metal during casting and also reduce convection.

[0023] Optionally, the metal rod rotates at a speed of 2-5 revolutions per second.

[0024] By adopting the above technical solution, a metal rod with a rotation speed of 2-5 revolutions per second can stir the molten metal in the mold while reducing the splashing of molten metal caused by excessive rotation speed of the metal rod.

[0025] Optionally, the duration of the electric arc in S5 is 5-8 seconds.

[0026] By adopting the above technical solution, an electric arc with a duration of 5-8 seconds can be designed to reduce the interference of heating on the metallographic structure of the ingot when the top of the molten metal in the delayed mold solidifies.

[0027] Optionally, the relationship between the outer diameter D of the metal rod, the tube thickness H of the metal rod, and the inner diameter R of the mold cavity is: D = 0.25R = 10H.

[0028] By adopting the above technical solution, a balance can be achieved between the metal rod's flow-guiding capacity, heat conduction capacity, stirring capacity, and the outer diameter of the metal ingot.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. A casting method for low-segregation, fine-grained ingots of high-melting-point metals is designed. The method comprises the following points: First, the rotation of a metal rod ensures uniform and controllable solidification of the molten metal within the mold in both time and space. Second, the solidification status of the molten metal within the mold can be directly sensed by observing the rotation torque of the metal rod, thereby controlling the casting speed accordingly. Third, the strong stirring of the metal rod breaks up primary dendrites and refines the grains. Fourth, the flow-guiding effect of the metal rod reduces splashing of the molten metal during casting. Fifth, continuous casting with controlled flow rate minimizes the formation of columnar crystals, facilitating rapid solidification of the molten metal to obtain a fine-grained structure. Sixth, the heat conduction and rotation of the metal rod further reduce the cooling rate difference between the central and edge regions of the molten metal, improving ingot quality. Seventh, the method features a simple structure and low cost.

[0031] 2. The designed casting method for low-segregation fine-grained ingots of high-melting-point metals uses arc discharge to reheat the top of the molten metal surface to delay the solidification of the molten metal shell, which can avoid internal shrinkage cavities caused by the rapid solidification of the top of the molten metal surface during the final stage of casting.

[0032] 3. The designed casting method for low-segregation fine-grained ingots of high-melting-point metals can control the heat dissipation effect of the metal rod itself and the ability to swirl and distribute the molten metal, thus avoiding premature solidification of the central area of ​​the mold due to excessive heat dissipation and cooling capacity of the metal rod. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the initial casting stage of this application;

[0034] Figure 2 This is a schematic diagram of the state during the arc discharge warming stage of this application;

[0035] Figure 3This is a cross-sectional view of the ingot prepared in Example 1 of this application;

[0036] Figure 4 This is a cross-sectional view of the ingot prepared in Comparative Example 1 of this application.

[0037] Reference numerals: 1. Crucible; 2. Vacuum furnace; 3. Lifting rod; 4. Metal rod; 5. Mold; 51. Water-cooled metal mold section; 52. Ceramic mold section; 6. Electric contactor; 7. Arc power supply. Detailed Implementation

[0038] The following is in conjunction with the appendix Figures 1-2 This application will be described in further detail.

[0039] This application discloses a casting method for a low-segregation fine-grained ingot of a high-melting-point metal.

[0040] Reference Figure 1 and Figure 2 A device for forming low-segregation fine-grained ingots of high-melting-point metals includes at least a vacuum furnace, a vacuum induction furnace, a PLC controller, a tilting motor, a rotary motor, a crucible, a mold, an arc power supply, an electrical contactor, a lifting rod, and a metal rod. The crucible, mold, and metal rod are all located inside the vacuum furnace. The vacuum induction furnace heats the solid metal in the crucible by electromagnetic induction. The lifting rod and the metal rod are coaxially welded, and the lifting rod passes through and is rotatably connected to the vacuum furnace. The rotary motor is located outside the vacuum furnace and is connected to the lifting rod to drive the lifting rod to rotate.

[0041] Reference Figure 1 and Figure 2 In order to achieve a balance between the flow-guiding capacity, heat conduction capacity, and stirring capacity of the metal rod 4 and the size of the ingot, the metal rod 4 is set as a hollow tube; and the relationship between the outer diameter D of the metal rod 4, the tube thickness H of the metal rod 4 and the inner cavity diameter R of the mold 5 is: D = 0.25R = 10H.

[0042] Reference Figure 1 and Figure 2 In the later stage of ingot casting, in order to prevent the temperature of the molten metal in the forming cavity of mold 5 from dissipating too quickly, mold 5 includes a water-cooled metal mold section 51 and a ceramic mold section 52. The water-cooled metal mold section 51 and the ceramic mold section 52 are coaxially arranged, and the water-cooled metal mold section 51 is located below the ceramic mold section 52. In this embodiment, the water-cooled metal mold section 51 is made of copper, and the ceramic mold section 52 is made of magnesium oxide.

[0043] Reference Figure 1 and Figure 2One end of the arc power supply 7 is electrically connected to the water-cooled metal mold section 51, and the other end is electrically connected to the lifting rod 3 through the electric contactor 6. When the metal rod 4 is raised to 5mm above the top of the molten metal surface and stops rotating, the electric contactor 6 and the lifting rod 3 automatically close to form a closed circuit with the water-cooled metal mold section 51.

[0044] A casting method for a low-segregation fine-grained ingot of a high-melting-point metal includes:

[0045] S1: Melting, pressure regulation, and heat preservation;

[0046] S11: Melting and heat preservation: Solid metal is contained in a crucible 1 and heated in a vacuum induction furnace until all the solid metal in the crucible 1 is melted to form a molten metal. The power of the vacuum induction furnace is maintained so that the temperature of the molten metal in the crucible 1 is always 100-150 degrees Celsius higher than its own melting point. In this embodiment, the temperature of the molten metal is 120 degrees Celsius higher than its own melting point.

[0047] S12: Pressure regulation: In order to reduce splashing caused by low air pressure during casting and the significant convection effect caused by high air pressure on the heat dissipation rate of the ingot, a low-pressure environment of 40-60Pa is provided for the entire casting process of low segregation fine-grained ingots through vacuum furnace 2, with 50Pa being preferred.

[0048] S2: Adjust height, start rotation;

[0049] S21: Height adjustment: The metal rod 4 is coaxially set 5-20mm above the bottom wall of the forming cavity of the mold 5, preferably 10mm, wherein the material of the metal rod 4 is the same as the material of the molten metal;

[0050] S22: Start rotation: Drive the metal rod 4 to start rotating. The rotation speed of the metal rod 4 is 2-5 revolutions / second, preferably 3 revolutions / second;

[0051] S3: Flowing and Spinning: The PLC controller and the tilting motor are used to control the tilting of the crucible 1, so that the molten metal in the crucible 1 flows into the forming cavity of the mold 5 along the metal rod 4; until the lower end of the metal rod 4 is submerged in the molten metal in the forming cavity of the mold 5 by 5-15mm, and the molten metal in the forming cavity of the mold 5 is driven to flow by rotation.

[0052] S4: Lifting rod, continuous casting;

[0053] S41: Lifting Rod: After casting begins, the lifting rod rises at a basic speed of 1-2 mm / s and maintains rotation. The lifting rod torque F is set, and a rotary motor and lifting rod 3 are used to drive the metal rod 4. The lifting rod 3 is coaxially welded to the metal rod 4, and the lifting rod 3 is conductive. When the rotary motor approaches the stall current, the rotational torque of the lifting rod 3 reaches F. The rotational torque M of the metal rod 4 is indirectly measured by continuously measuring the current of the rotary motor. The rotational torque M of the metal rod 4 is compared with the lifting rod torque F. If M ≥ F, the metal rod 4 rises 5-8 mm at a speed of 3-4 mm / s. During the lifting process, the metal rod 4 remains inserted into the molten metal in the mold.

[0054] S42: Continuous casting: According to the position of the lifting rod, the furnace motor controls the slow and continuous tilting of the crucible 1, so that the molten metal in the crucible 1 flows continuously along the metal rod 4 into the forming cavity of the mold 5, and the amount of molten metal in the forming cavity of the mold 5 remains constant.

[0055] S5: Arc Initiation and Temperature Compensation: After all the molten metal in the crucible 1 has been poured into the forming cavity of the mold 5, the metal rod 4 is raised until the lower end of the metal rod 4 is 5-10 mm above the top of the molten metal surface in the mold 5 and then stops rotating, preferably 5 mm; the electric contactor 6 is used to contact the lifting rod 3, and a closed circuit is formed between the lifting rod 3, the metal rod 4, the arc power supply 7 and the mold 5, so that an electric arc is formed between the lower end of the metal rod 4 and the molten metal surface and lasts for 5-8 seconds to delay the solidification of the liquid surface; in this embodiment, the duration of the electric arc is preferably 6 seconds.

[0056] The implementation principle of the casting method for a low-segregation fine-grained ingot of a high-melting-point metal according to an embodiment of this application is as follows: First, the solid metal in the crucible 1 is heated by induction heating in a vacuum induction furnace until the fixed metal is melted. Then, the induction power of the vacuum induction furnace is kept constant to keep the molten metal in the crucible 1 in a liquid state. Then, the gas pressure in the vacuum furnace 2 is adjusted to 50 Pa to reduce the splashing caused by too low gas pressure during casting and the significant convection caused by too high gas pressure, which affects the heat dissipation rate of the ingot.

[0057] Then, the metal rod 4 is lowered by the lifting rod 3 until the distance between the lower end of the metal rod 4 and the bottom wall of the forming cavity of the mold 5 is between 5-20mm. At the same time, the metal rod 4 is driven to start rotating. Then, the crucible 1 is tilted to pour out the molten metal in the crucible 1 and flow into the forming cavity of the mold 5 along the metal rod 4. During the process of the molten metal flowing into the forming cavity of the mold 5 along the metal rod 4, some of the heat is transferred to the outside through the metal rod 4. The rotating metal rod 4 breaks up the primary dendrites in the molten metal in the forming cavity of the mold 5 by strong stirring, and provides a large number of nuclei to generate fine equiaxed crystals. Furthermore, strong stirring can homogenize the alloy composition in the molten metal and avoid compositional segregation.

[0058] Meanwhile, as the metal rod 4 rotates, the hotter molten metal, due to its lower viscosity, is thrown to a position close to the periphery of the forming cavity of the mold 5, where the cooling capacity is strong. The molten metal near its melting point, due to its higher viscosity, falls to a position close to the center of the mold 5, where the cooling capacity is weak. Under the rotation of the metal rod 4, the difference in cooling capacity between the central and edge regions in the horizontal direction is reduced. At the same time, the metal rod 4 undertakes part of the heat dissipation of the molten metal in the middle region of the mold 5, further reducing the difference in cooling rate between the molten metal in the middle and edge regions.

[0059] During the rotation of metal rod 4, the rotational torque of metal rod 4 is indirectly obtained by measuring the current of the CNC motor. When the solidified structure in the central region of mold 5 approaches the end of metal rod 4, the rotational torque of metal rod 4 increases significantly. A lifting torque F is set. If the rotational torque M of metal rod 4 is less than the set lifting torque F, metal rod 4 rises at a basic speed of 1-2 mm / s and continues to rotate. If the rotational torque M of metal rod 4 is greater than or equal to the set lifting torque F, metal rod 4 is lifted by lifting rod 3. The tilting of crucible 1 is always related to the lifting of the rod. The molten metal in crucible 1 flows along metal rod 4 into the forming cavity of mold 5. The amount of molten metal in the forming cavity of mold 5 remains constant until the entire ingot is formed.

[0060] After all the molten metal in the crucible 1 is poured into the forming cavity of the mold 5, the ingot casting process enters the final stage. At this time, the heat dissipation rate at the top of the molten metal is relatively fast. In order to avoid the top area of ​​the ingot solidifying too early and forming a solid shell, the metal rod 4 is raised to 5-10mm above the molten metal surface, the arc power supply 7 is turned on, and an arc is formed between the metal rod 4 and the molten metal in the forming cavity of the mold 5, which lasts for 5-8 seconds. The arc discharge provides heat to the top of the molten metal surface to delay the solidification of the surface shell. Then, the ingot is obtained by natural cooling and solidification.

[0061] Preparation Example 1

[0062] S1: Melting and holding: Heat 20 kg of platinum-rhodium alloy (PtRh20) until it is completely melted to form a platinum-rhodium alloy melt, and keep the temperature of the platinum-rhodium alloy melt 120°C above the melting point;

[0063] S2: Adjustment and Rotation: A metal rod 4 is coaxially positioned 10mm above the bottom wall of the forming cavity of mold 5, driving the metal rod 4 to rotate; the metal rod 4 is made of the same material as the molten metal, and is coaxial with mold 5. The outer diameter of the metal rod 4 is 25mm, and the tube thickness is 2.5mm. The inner cavity dimensions of the water-cooled copper mold section are 75*100*130mm (length*width*height), and the inner cavity dimensions of the magnesium oxide mold section are 75*100*70mm (length*width*height).

[0064] S3: Draining and Spinning for Temperature Equalization: The platinum-rhodium alloy melt obtained in step S1 flows into the forming cavity of mold 5 along metal rod 4 until the lower end of metal rod 4 is submerged 10mm into the platinum-rhodium alloy melt in mold 5, and the platinum-rhodium alloy melt in mold 5 is driven to flow by rotation.

[0065] S4: Lifting the rod and casting: The basic lifting speed of the rod is 2 mm / s; set the lifting torque F and continuously measure the rotational torque M of the metal rod 4. If M < F, the metal rod 4 rises at the basic lifting speed and maintains rotation; if M ≥ F, the metal rod 4 is lifted by 6 mm; the platinum-rhodium alloy melt obtained in step S1 continues to flow into the mold 5 along the metal rod 4, and its casting speed is controlled to match the lifting speed of the metal rod 4, so that the amount of platinum-rhodium alloy melt in the mold 5 remains consistent until the ingot is formed.

[0066] S5: Arc Initiation and Temperature Compensation: After the platinum-rhodium alloy melt is completely poured into mold 5, control the metal rod 4 to be raised to 5mm above the surface of the platinum-rhodium alloy melt and stop rotating. Power is supplied to the metal rod 4 so that an electric arc is formed between the lower end of the metal rod 4 and the surface of the platinum-rhodium alloy melt and lasts for 6 seconds. The discharge current is 900A to delay the solidification of the liquid surface.

[0067] Comparative Example 1

[0068] S1: Heat 20 kg of platinum-rhodium alloy until it is completely melted, and make the temperature of the platinum-rhodium alloy melt 75°C higher than its own melting point. Gradually and slowly pour the platinum-rhodium alloy melt into a vertical water-cooled copper mold. The total pouring time is 50 seconds.

[0069] Comparative Example 2

[0070] S1: Heat 20 kg of platinum-rhodium alloy until it is completely melted, and make the temperature of the platinum-rhodium alloy melt 75°C higher than its melting point. Gradually and slowly pour the platinum-rhodium alloy melt into a vertical water-cooled copper mold, and at the same time make the platinum-rhodium alloy melt in the vertical water-cooled copper mold flow by electromagnetic stirring.

[0071] Performance test data

[0072] Table 1. Comparison of Detection Data

[0073] Standard sample Macroscopic density (g / cm3) Relative density Shrinkage and porosity Preparation Example 1 18.3 97.6％ No Comparative Example 1 16.2 86.2％ Yes Comparative Example 2 17.4 92.7％ Yes

[0074] Based on the preparation examples 1, 1, and 2, and in conjunction with Table 1, it can be seen that the ingots processed using the embodiments of this application have significantly higher macroscopic and relative densities than the ingots prepared using 1 and 2, indicating that the ingots prepared using the processing method of this application have fewer shrinkage cavities and porosity.

[0075] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A casting method of a low-segregation fine-grained ingot of a high-melting-point metal, characterized by, comprising S1: melting, holding: heating the solid metal to all melt to form a metal melt, and keeping the metal melt temperature above the melting point at all times; S2: adjusting height, rotating: placing a metal rod coaxially above the bottom wall of the forming cavity of the mold by 5-20 mm, and driving the metal rod to rotate; wherein the metal rod is made of the same material as the metal melt, and the metal rod is coaxial with the mold; S3: guiding flow, rotating cloth, and uniform temperature: flowing the metal melt prepared in step S1 along the metal rod into the forming cavity of the mold until the lower end of the metal rod is immersed in the metal melt in the mold by 5-15 mm, and the metal melt in the mold is driven to flow by rotating; S4: lifting rod, continuous casting: setting the lifting torque F and continuously measuring the rotating torque M of the metal rod, if M < F, the metal rod is continuously rotated while rising at a basic speed of 1-3 mm / s; if M ≥ F, the metal rod is lifted by 5-10 mm, and the metal melt prepared in step S1 is continuously flowed into the mold at a matching speed to keep the amount of metal melt in the mold consistent, and the metal rod is always immersed in the metal melt until the ingot is formed.

2. The casting method of a low-segregation fine-grained ingot of a high-melting point metal according to claim 1, characterized by, Further comprising S5: arc starting and temperature compensation: after the metal melt is completely poured into the mold, the metal rod is lifted to 5-10 mm above the liquid surface of the metal melt and stopped rotating, and the metal rod is powered to form an electric arc between the lower end of the metal rod and the liquid surface of the metal melt to delay the liquid surface solidification.

3. The casting method of a low-segregating fine-grained ingot of a high-melting point metal according to claim 1, characterized by, The metal rod is provided as a hollow tube.

4. The casting method of a low-segregating fine-grained ingot of a high-melting point metal according to claim 1, characterized by, The mold comprises a water-cooled metal mold section and a ceramic mold section, the water-cooled metal mold section and the ceramic mold section are coaxially arranged, and the water-cooled metal mold section is located below the ceramic mold section.

5. The casting method of a low-segregation fine-grained ingot of a high-melting point metal according to claim 1, characterized by, The steps S1-S4 are all carried out under a gas pressure of 40-60 Pa.

6. The casting method of a low-segregating fine-grained ingot of a high-melting point metal according to claim 1, characterized by, The rotating speed of the metal rod is 2-5 revolutions per second.

7. The casting method of a low-segregating fine-grained ingot of a high-melting point metal according to claim 2, characterized by, The duration of the electric arc in S5 is 5-8 seconds.

8. The casting method of a low-segregating fine-grained ingot of a high-melting point metal according to claim 3, characterized by, The relationship between the outer diameter D of the metal rod, the tube thickness H of the metal rod, and the size R of the mold inner cavity is: D=0.25R=10H.

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