A method for electron beam cold hearth melting and continuous casting of refractory high-entropy alloy hollow rod blanks

Abstract

The present application relates to a method for electron beam cold hearth melting and continuous casting of hollow rod blanks of refractory high-entropy alloys, in particular, two electron guns are used for heating, the first electron gun is used for injecting the alloy material into a ring-shaped crystallizer after remelting in the cold hearth, and the second electron gun is used for keeping the alloy liquid at the top of the ring-shaped crystallizer heated, so that the alloy liquid maintains sufficient heat and good fluidity, flows from the top to the bottom of the ring-shaped crystallizer, and the ring-shaped crystallizer has a water cooling effect, so that the alloy liquid gradually cools down, solidifies at the ingot head, and continuously solidifies to obtain the hollow rod blank through the bottom support of the ingot drawing mechanism placed below the crystallizer at a certain speed. The present application solves the technical problem of the hollow rod blank of the high-melting-point alloy prepared by the existing electron beam cold hearth melting method, eliminates the drilling process in seamless pipe production, realizes short-process pipe blank manufacturing, and improves the production efficiency and material utilization.

Description

Technical Field

[0001] This invention relates to a method for melting and forming refractory high-entropy alloys, specifically to a method for continuously casting hollow billets of refractory high-entropy alloys using an electron beam cooling bed. Background Technology

[0002] Refractory high-entropy alloys typically refer to a class of novel alloys with titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten as their main constituent elements. These alloys possess comprehensive advantages such as high strength, high hardness, high wear resistance, high temperature resistance, and radiation resistance, thus showing broad application potential in aerospace structural components, missile warheads, nuclear reactor structural materials, wear-resistant materials, biomedical materials, shipbuilding and marine engineering materials, and thermoelectric materials. However, the diverse composition of these alloys, their high and varied melting points, high reactivity, and sensitivity to impurities present challenges to their production and preparation.

[0003] The main methods for preparing refractory high-entropy alloys include mechanical alloying, laser cladding, electric arc melting, cold crucible induction melting, and electron beam cold bed melting. Among these, electric arc melting, cold crucible induction melting, and electron beam melting are currently the most widely used methods. However, for refractory high-entropy alloys with melting points exceeding 2000℃, electric arc melting and cold crucible induction melting can only produce alloys with relatively small sizes, making it difficult to achieve continuous forming of large ingots. In contrast, vacuum electron beam melting, with its high heating temperature, large superheat, and good molten metal fluidity, can achieve continuous forming of large ingots with high production efficiency. Furthermore, in practical engineering applications, many refractory high-entropy alloys require their fabrication into tubing, such as warhead casings, nuclear reactor cooling water pipes, and rocket engine nozzles. Currently, seamless tubing of refractory alloys is typically obtained by machining solid ingots, drilling, forging, and rolling, a complex process with low material utilization. Therefore, casting hollow refractory high-entropy alloy ingots can eliminate machining and drilling processes in pipe production, enabling short-process billet manufacturing. However, existing electron beam cold-bed melting methods produce refractory high-entropy alloys in plates or bars; the preparation of hollow billets requires a ring crystallizer, but the shrinkage during solidification and cooling of the hollow billet easily leads to core seizure and ingot pulling failure. Therefore, the preparation of hollow refractory alloy billets remains a blank. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention matches the ingot pulling speed and the feeding speed to rationally control the liquid level of the molten metal in the crystallizer, ensuring that the solidified hollow billet leaves the ingot core before significant shrinkage occurs, thus preventing core seizing. Based on this, this invention provides a process method suitable for electron beam cold hearth melting to produce hollow billets of refractory high-entropy alloys with titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten as the main constituent elements.

[0005] A method for continuously casting hollow billets of refractory high-entropy alloys using an electron beam cold bed melting process is characterized by comprising the following steps:

[0006] (1) Weigh the corresponding mass of refractory high-entropy alloy material according to the size requirements of the target hollow bar billet, and clean it thoroughly;

[0007] (2) According to the material and the size of the cooling bed, a portion of the above alloy material is placed in the feeding hopper and the other portion is laid in the cooling bed in the electron beam melting furnace. According to the size of the target hollow bar billet, an annular crystallizer is selected and installed below the pouring port of the cooling bed. The annular crystallizer includes a cylindrical water-cooled outer ring and a cylindrical water-cooled inner core. A pulling mechanism is set below the annular crystallizer. A pulling head is placed on the bottom support of the pulling mechanism. The pulling head is made of the alloy of the target hollow bar material. Its size is selected according to the size of the target hollow bar billet. Corresponding to the annular structure between the outer ring and the inner core of the annular crystallizer, the pulling head is engaged with the bottom support of the pulling mechanism. The bottom support of the pulling mechanism is moved upward so that the pulling head part enters the annular crystallizer. The furnace door is closed.

[0008] (3) The electron beam melting furnace is pre-evacuated to below 10 Pa, and then the electron beam melting furnace is evacuated to a high vacuum of 5 × 10 Pa. -2 Below Pa;

[0009] (4) Start the first electron gun located above the cooling bed to heat the alloy material placed in the cooling bed, start the second electron gun located above the crystallizer to heat the drawing head, and gradually increase the input power until the material in the cooling bed and the surface of the drawing head are completely melted;

[0010] (5) Select the stable heating power of the first electron gun according to the melting point and size of the material, and select the stable heating power of the second electron gun according to the melting point of the molten material and the diameter of the crystallizer. After the first electron gun and the second electron gun are working stably, start the feeding motor to push the alloy material in the feeding bin to the cooling bed, and maintain a feeding speed of 5-10 mm / min to feed the alloy material so that it melts and continues to flow into the annular crystallizer.

[0011] (6) Based on the speed at which the molten alloy flows into the crystallizer, the billet pulling mechanism is set to a pulling speed of 2-5 mm / min so that the melting of materials, solidification of the molten metal in the crystallizer, and pulling of the billet downward by the billet pulling mechanism can be carried out continuously throughout the entire system.

[0012] (7) After the ingot pulling mechanism pulls the bottom support to the specified position, it stops scanning the electron beam. After the furnace cools to 50°C, the upper part of the furnace body and the lower part of the furnace body are separated. The lower furnace body, hollow ingot and crystallizer core are pushed out of the furnace body through the hydraulic transmission device. Then the core located on the upper part of the ingot is removed, the ingot pulling head and the bottom support of the ingot pulling mechanism are separated, and the refractory high entropy alloy hollow bar billet is taken out.

[0013] Preferably, the scanning strategy adopted by the first electron gun is as follows: the electron beam width is 1.5~5mm, the scanning frequency is 200Hz, the scanning area is rectangular, its length is at least 100mm larger than the width of the feeding bin, its width is equivalent to the width of the cooling bed, and the scanning area is located at the center of the cooling bed.

[0014] Preferably, the scanning strategy of the second electron gun is as follows: the electron beam width is 1.5~5mm, the scanning frequency is 200Hz, the scanning area is annular, the outer diameter of which is 5~15mm smaller than the outer ring diameter of the crystallizer, and the inner diameter is 5~15mm larger than the inner core diameter of the crystallizer.

[0015] Preferably, the pulling speed and feeding speed are such that the height of the molten metal level in the annular crystallizer is maintained between 30 mm and 40 mm.

[0016] The beneficial effects of the technical solution provided by this invention are as follows: This invention provides a process method for preparing high-melting-point alloy hollow billets by electron beam cold hearth melting, which eliminates machining and drilling processes in seamless pipe production, realizing short-process billet manufacturing, thereby improving production efficiency and material utilization; This invention uses an electron beam as a heating source for melting, with a high heating temperature, which can realize the preparation of hollow billets of metal materials with melting points of 2000℃ and above; The use of continuous casting for the preparation of hollow billets can realize the preparation of billets with large length-to-diameter ratios. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0018] Figure 2 This is a schematic diagram of the annular crystallizer structure in this invention;

[0019] In the diagram: 1-Feeding bin, 2-Cooling bed, 3-Ring crystallizer, 4-1-Electron gun 1, 4-2-Electron gun 2, 5-Alloy material, 3-1-Water-cooled outer ring, 3-2-Water-cooled inner core, 6-Bottom support of the ingot pulling mechanism, 7-Ingot pulling head. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to specific embodiments. Unless otherwise specified, the implementation methods described are conventional methods. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0021] The refractory high-entropy alloy in this invention refers to a new type of alloy with titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten as the main constituent elements.

[0022] The method for producing hollow billets of refractory high-entropy alloys by electron beam cold bed melting provided by the present invention mainly involves heating with two electron guns. The first electron gun 4-1 is used to inject the alloy material 5 into the annular crystallizer 3 after remelting in the cold bed 2. The second electron gun 4-2 is used to keep the alloy liquid at the top of the annular crystallizer 3 heated, so that it maintains sufficient heat and good fluidity, flowing from the top to the bottom of the annular crystallizer 3. At the same time, the annular crystallizer has a water cooling effect, so that it gradually cools down and solidifies on the drawing head 7. Meanwhile, the continuous solidification of the metal liquid is achieved by pulling down the bottom support 6 of the drawing mechanism placed below the crystallizer at a certain speed to obtain the hollow billet.

[0023] like Figure 1 As shown, the feeding bin 1 is located above the cooling bed 2 on one side, part of which is in the electron beam melting furnace. It can push the alloy material 5 to the top of the cooling bed 2. The alloy material 5 from the feeding bin 1 enters the cooling bed 2 and is heated by the first electron gun 4-1, causing the alloy material 5 to melt. It then flows through the pouring port of the cooling bed 2 into the annular crystallizer 3 below. The annular crystallizer 3 includes an outer cylindrical water-cooled outer ring 3-1 and an inner cylindrical water-cooled inner core 3-2. The water-cooled outer ring 3-1 and the water-cooled inner core 3-2 are coaxial, and there is a hollow ring between them. The annular crystallizer 3 has a ring structure in which the molten alloy material 5 flows into the annular structure between the water-cooled outer ring 3-1 and the water-cooled inner core 3-2 through the casting port of the cooling bed 2. A pulling mechanism is provided below the annular crystallizer 3, and a pulling head 7 is placed on the bottom support 6 of the pulling mechanism. The pulling head is made of the alloy material of the target hollow rod material, i.e., the alloy material 5. The pulling head 7 corresponds to the annular structure between the water-cooled outer ring 3-1 and the water-cooled inner core 3-2 of the annular crystallizer 3. The bottom of the pulling head 7 is engaged with the bottom support 6 of the pulling mechanism. Preferably, the pulling head 7 and the bottom support 6 of the pulling mechanism are connected by a dovetail groove or a positioning pin.

[0024] The electron gun, cooling bed 2, and annular crystallizer 3 are all located in the electron beam melting furnace, and the ingot pulling mechanism is sealed to the melting furnace.

[0025] The annular crystallizer 3 and the drawing head 7 are selected according to the size of the target hollow billet. The annular structure between the water-cooled outer ring 3-1 and the water-cooled inner core 3-2 of the annular crystallizer 3 is the same size as the annular structure of the target hollow billet. That is, the inner diameter of the water-cooled outer ring 3-1 is the outer diameter of the target hollow billet, and the outer diameter of the water-cooled inner core 3-2 is the inner diameter of the target hollow billet. The corresponding drawing head 7, except for the part that is locked with the bottom of the mechanism base 6, is also an annular structure with the same inner and outer diameters.

[0026] like Figure 2 As shown, before the casting begins, the casting head 7 is partially inserted into the annular crystallizer 3 by moving the casting mechanism base 6 upward. During casting, to prevent the alloy material 5 from solidifying and shrinking, thus clinging to the top of the water-cooled inner core 3-2 of the crystallizer, the casting speed and feeding speed are strictly controlled to ensure that the liquid level in the annular crystallizer 3 always meets the following relationship: 30mm ≤ (water-cooled inner core length L - distance H from liquid level to the top of the crystallizer) ≤ 40mm.

[0027] The specific process is as follows:

[0028] 1. Weigh out the appropriate mass of refractory high-entropy alloy material 5 according to the size requirements of the target hollow bar billet, and clean it thoroughly;

[0029] 2. Place a portion of the cleaned alloy material 5 into the feeding bin 1 of the electron beam melting furnace, and the other portion into the cooling bed 2. Move the bottom support 6 of the ingot pulling mechanism upward so that the ingot pulling head 7 enters the annular crystallizer 3, and close the furnace door. The weight of the material placed in the feeding bin 1 and the cooling bed 2 is determined according to the material, the size of the prepared metal rod, the size of the cooling bed, and the metal density to ensure that the cooling bed is filled with molten metal. Then feed the material, melt it, and the molten metal can pass through the cooling bed and flow into the crystallizer. The remaining part is placed into the feeding bin 1.

[0030] 3. Pre-evacuate the electron beam melting furnace to below 10 Pa, then evacuate it to a high vacuum of 5 × 10 Pa. -2 Below Pa;

[0031] 4. Start the first electron gun 4-1 located above the cooling bed to heat the alloy material 5 placed in the cooling bed, and start the second electron gun 4-2 located above the crystallizer 3 to heat the pulling head 7, gradually increasing the input power until the alloy material 5 in the cooling bed 2 and the surface of the pulling head 7 are completely melted.

[0032] 5. After the first electron gun 4-1 and the second electron gun 4-2 are working stably, start the feeding motor and feed at a speed of 5-10 mm / min to melt the alloy material 5 and continuously flow into the crystallizer 3 through the casting port of the cooling bed 2.

[0033] 6. Based on the speed at which the molten metal flows into the crystallizer 3, set the billet pulling speed to 2-5 mm / min, so that the melting of materials, solidification of the alloy liquid in the crystallizer 3, and pulling of the billet downward by the billet pulling mechanism can be carried out continuously throughout the entire system.

[0034] 7. After the ingot pulling mechanism pulls the bottom support 6 to the specified position, it stops electron beam scanning. After the furnace cools to 50°C, the upper and lower parts of the furnace body are separated. The lower furnace body, hollow ingot and crystallizer water-cooled inner core 3-2 are pushed out of the furnace body through the hydraulic transmission device. Then the water-cooled inner core 3-2 located on the upper part of the ingot is removed. Subsequently, the ingot pulling head 7 and the bottom support 6 of the ingot pulling mechanism are separated, and the refractory high-entropy alloy hollow billet is taken out.

[0035] The scanning strategy adopted by the first electron gun 4-1 is as follows: the electron beam width is 1.5~5mm, the scanning frequency is 200Hz, the scanning area is rectangular, its length is at least 100mm larger than the width of the feeding chamber 1, its width is equivalent to the width of the cooling bed 2, and the scanning area is located in the center of the cooling bed.

[0036] The scanning strategy of electron gun 2 is as follows: electron beam width 1.5~5mm, scanning frequency 200Hz, and the scanning area is annular. Its outer diameter is 5~15mm smaller than the outer ring diameter of crystallizer 3, and its inner diameter is 5~15mm larger than the inner ring diameter of crystallizer 3, in order to avoid the electron beam bombarding the surface of crystallizer 3 and causing equipment burnout. Its inner and outer diameters are 5~15mm smaller than the inner and outer diameters of the annular crystallizer.

[0037] The selection of the stable heating power of the first electron gun 3-1 is determined by the melting point and size of the alloy material 5 being smelted. Based on the melting state of the metal during smelting, it ensures that the material can continuously melt and that the molten metal in the cooling bed can continuously flow into the annular crystallizer. Generally, the higher the melting point and the larger the size, the higher the stable heating power should be; conversely, the lower the melting point and the smaller the size, the lower the stable heating power should be. The optimal choice is to ensure that the material can continuously melt and that the molten metal in the cooling bed can continuously flow into the annular crystallizer. The selection of the stable heating power of the second electron gun 3-2 is determined by the melting point of the smelted material and the diameter of the crystallizer. The selection principle is the same as above, ensuring that the solution in the crystallizer remains molten and that no solidified shell forms on the inner and outer walls of the crystallizer.

[0038] The molten metal is still in a molten state when it reaches the crystallizer, but as the bottom support of the crystallizer is pulled down, the liquid in the crystallizer will also move downwards, and new molten metal will be added in. The molten metal at the bottom will be heated less and begin to solidify. This is a dynamic and continuous process.

[0039] Solidification rate (mass solidified per unit time) = pull-down speed × crystallizer cross-sectional area × molten metal density; replenishment rate of molten metal = molten metal inflow rate - solidification rate.

[0040] The production method is further illustrated below through examples.

[0041] Example 1: The refractory high-entropy alloy is composed of the following components in molar percentage: titanium 35%, zirconium 10%, hafnium 20%, niobium 10%, and tantalum 25%. Its density is 10.5 g / cm³, and its melting point is ~2100℃. The refractory high-entropy alloy is supplied in bulk form with a diameter of 50 mm and a height of 60 mm.

[0042] In one implementation method, the hollow bar blank prepared has the following dimensions: outer diameter 200mm, inner diameter 100mm, and length 500mm.

[0043] This embodiment provides a method for producing hollow bar billets of refractory high-entropy alloys, including the following steps:

[0044] S1. Weigh 125kg and 25kg of alloy materials respectively, clean them and place them in the feeding silo 1 and cooling bed 2 respectively. Select and place the annular crystallizer 3 and the pulling head 7. Move the bottom support 6 of the pulling mechanism upward so that the pulling head 7 enters the annular crystallizer 3 and is adjusted to a suitable position before closing the furnace door.

[0045] S2. Pre-evacuate the electron beam melting furnace to below 10 Pa, then evacuate the electron beam melting furnace to a high vacuum of 5 × 10 Pa. -2 Below Pa;

[0046] S3. Start the electron gun 1 located above the cooling bed to heat the alloy material placed in the cooling bed, and start the electron gun 2 located above the crystallizer to heat the pulling head 7. Gradually increase the input power until the material in the cooling bed and the surface of the pulling head are completely melted.

[0047] S4. After electron gun 1 and electron gun 2 are working stably, start the feeding motor and feed at a speed of 5 mm / min to melt the alloy material and allow it to continue flowing into the crystallizer.

[0048] S5. Based on the flow rate of the molten metal into the crystallizer, set the billet pulling speed to 2 mm / min to ensure continuous material melting, solidification of the molten metal in the crystallizer, and downward pulling of the billet by the billet pulling mechanism. The flow rate of the molten metal is determined based on the cross-sectional area of ​​the crystallizer and the downward pulling speed.

[0049] S6. After the ingot pulling mechanism pulls the bottom support to the specified position, it stops electron beam scanning. After the furnace cools to 50°C, the upper and lower parts of the furnace body are separated. The lower furnace body, hollow ingot and inner core are pushed out of the furnace body through the hydraulic conveying device. Then the core rod on the upper part of the ingot is removed, and then the bottom support is removed to obtain a refractory high entropy alloy hollow billet.

[0050] The scanning strategy employed by the first electron gun 4-1 is as follows: an electron beam width of 3mm, a scanning frequency of 200Hz, and a rectangular scanning area with a length of 250mm and a width of 110mm. This is 50mm wider than the feed hopper and roughly the same width as the cooling bed, with the scanning area located at the center of the cooling bed. The scanning strategy of the second electron gun 4-2 is as follows: an electron beam width of 3mm, a scanning frequency of 200Hz, and a ring-shaped scanning area with an inner diameter of 190mm and an outer diameter of 110mm. The outer diameter is 10mm smaller than the outer ring diameter of the crystallizer and 10mm larger than the inner ring diameter of the crystallizer, effectively preventing the electron beam from bombarding the crystallizer surface and causing equipment burnout.

[0051] The first electron gun 4-1 has a power of 100~120kW during stable heating to ensure that the material can continue to melt and that the molten metal in the cooling bed can continuously flow into the annular crystallizer; the second electron gun 4-2 has a power of 110~130kW during stable heating to ensure that the solution in the crystallizer remains molten and that no solidified shell is formed on the inner and outer annular walls of the crystallizer.

[0052] In embodiment two, the refractory high-entropy alloy is composed of the following components in molar percentage: titanium 25%, zirconium 25%, hafnium 25%, and niobium 25%. Its density is 8.5 g / cm³, and its melting point is ~1950℃. The refractory high-entropy alloy is in the form of a block with a diameter of 50 mm and a height of 60 mm.

[0053] In one embodiment, the hollow bar blank prepared has the following dimensions: outer diameter 200mm, inner diameter 100mm, and length 500mm.

[0054] This embodiment provides a method for producing hollow bar billets of refractory high-entropy alloys, including the following steps:

[0055] S1. Weigh 100kg and 15kg of alloy material respectively, clean them, and place them in the feeding silo and cooling bed respectively. After placing the ingot head and adjusting it to the appropriate position, close the furnace door.

[0056] S2. Pre-evacuate the electron beam melting furnace to below 10 Pa, then evacuate the electron beam melting furnace to a high vacuum of 5 × 10 Pa. -2 Below Pa;

[0057] S3. Start the electron gun 1 located above the cooling bed to heat the alloy material placed in the cooling bed, and start the electron gun 2 located above the crystallizer to heat the pulling head. Gradually increase the input power until the material in the cooling bed and the surface of the pulling head are completely melted.

[0058] S4. After electron gun 1 and electron gun 2 are working stably, start the feeding motor and feed at a speed of 6 mm / min to melt the alloy material and allow it to continue flowing into the crystallizer.

[0059] S5. Based on the speed at which the molten metal flows into the crystallizer, set the billet pulling speed to 3 mm / min, so that the entire system can continuously melt the material, solidify the molten metal in the crystallizer, and pull the billet downwards.

[0060] S6. After the ingot pulling mechanism pulls the bottom support to the specified position, it stops electron beam scanning. After the furnace cools to 50°C, the upper and lower parts of the furnace body are separated. The lower furnace body, hollow ingot and inner core are pushed out of the furnace body through the hydraulic conveying device. Then the core rod on the upper part of the ingot is removed, and then the bottom support is removed to obtain a refractory high entropy alloy hollow billet.

[0061] The scanning strategy employed by electron gun 1 is as follows: electron beam width 3mm, scanning frequency 200Hz, and a rectangular scanning area with a length of 250mm (50mm wider than the feed hopper) and a width of 110mm (comparable to the width of the cooling bed). The scanning area is located at the center of the cooling bed. The scanning strategy of electron gun 2 is as follows: electron beam width 3mm, scanning frequency 200Hz, and a ring-shaped scanning area with an inner diameter of 190mm and an outer diameter of 110mm. The outer diameter is 10mm smaller than the outer ring diameter of the crystallizer and 10mm larger than the inner ring diameter of the crystallizer, effectively preventing the electron beam from bombarding the crystallizer surface and causing equipment burnout.

[0062] The electron gun 1 has a stable heating power of 80~100kW to ensure that the material can be continuously melted and the molten metal in the cooling bed can be continuously flowed into the annular crystallizer; the electron gun 2 has a stable heating power of 90~110kW to ensure that the solution in the crystallizer remains molten and no solidified shell is formed on the inner and outer annular walls of the crystallizer.

[0063] In embodiment three, the refractory high-entropy alloy is composed of the following components in molar percentage: titanium 40%, zirconium 20%, vanadium 25%, niobium 8%, and Al 7%. Its density is 5.4 g / cm³, and its melting point is ~1650℃. The refractory high-entropy alloy is in the form of a block with a diameter of 50 mm and a height of 60 mm.

[0064] In one embodiment, the hollow bar blank prepared has the following dimensions: outer diameter 200mm, inner diameter 100mm, and length 600mm.

[0065] This embodiment provides a method for producing hollow bar billets of refractory high-entropy alloys, including the following steps:

[0066] S1. Weigh 80kg and 10kg of alloy materials respectively, clean them, and place them in the feeding silo and cooling bed respectively. After placing the ingot head and adjusting it to the appropriate position, close the furnace door.

[0067] S2. Pre-evacuate the electron beam melting furnace to below 10 Pa, then evacuate the electron beam melting furnace to a high vacuum of 5 × 10 Pa. -2 Below Pa;

[0068] S3. Start the first electron gun 4-1 located above the cooling bed to heat the alloy material placed in the cooling bed, and start the second electron gun 4-2 located above the crystallizer to heat the pulling head 7. Gradually increase the input power until the material in the cooling bed and the surface of the pulling head are completely melted.

[0069] S4. After the first electron gun 4-1 and the second electron gun 4-2 are working stably, start the feeding motor and feed at a speed of 7 mm / min to melt the alloy material and allow it to continue flowing into the crystallizer.

[0070] S5. Based on the speed at which the molten metal flows into the crystallizer, set the billet pulling speed to 4 mm / min, so that the entire system can continuously melt the material, solidify the molten metal in the crystallizer, and pull the billet downwards.

[0071] S6. After the ingot pulling mechanism pulls the bottom support to the specified position, it stops electron beam scanning. After the furnace cools to 50°C, the upper and lower parts of the furnace body are separated. The lower furnace body, hollow ingot and inner core are pushed out of the furnace body through the hydraulic conveying device. Then the core rod on the upper part of the ingot is removed, and then the bottom support is removed to obtain a refractory high entropy alloy hollow billet.

[0072] The scanning strategy adopted by the first electron gun 4-1 is as follows: the electron beam width is 2.5mm, the scanning frequency is 200Hz, the scanning area is rectangular, the length is 250mm, which is 50mm larger than the width of the feeding bin 1, and the width is 110mm, which is comparable to the width of the cooling bed. The scanning area is located in the center of the cooling bed.

[0073] The scanning strategy of the second electron gun 4-2 is as follows: the electron beam width is 2.5mm, the scanning frequency is 200Hz, and the scanning area is annular with an inner diameter of 190mm and an outer diameter of 110mm. The outer diameter is 10mm smaller than the outer ring diameter of the crystallizer and 10mm larger than the inner ring diameter of the crystallizer, which effectively avoids the electron beam from bombarding the surface of the crystallizer and causing the equipment to burn out.

[0074] The first electron gun 4-1 has a stable heating power of 60~70kW to ensure that the material can continue to melt and that the molten metal in the cooling bed can continuously flow into the annular crystallizer; the second electron gun 4-2 has a stable heating power of 70~80kW to ensure that the solution in the crystallizer remains molten and that no solidified shell is formed on the inner and outer annular walls of the crystallizer.

Claims

1. A method for continuously casting hollow billets of refractory high-entropy alloys using an electron beam cooling bed, characterized in that, Includes the following process: S1. Weigh the corresponding mass of refractory high-entropy alloy material according to the size requirements of the target hollow billet, and clean it thoroughly. S2. Based on the material and cooling bed dimensions, place a portion of the aforementioned alloy material in the feeding hopper and the other portion in the cooling bed within the electron beam melting furnace. Select an annular crystallizer according to the dimensions of the target hollow billet and install it below the casting port of the cooling bed. The annular crystallizer includes a cylindrical water-cooled outer ring and a cylindrical water-cooled inner core. A pulling mechanism is set below the annular crystallizer, and a pulling head is placed on the bottom support of the pulling mechanism. The pulling head is made of the alloy of the target hollow billet material, and its size is selected according to the dimensions of the target hollow billet. Corresponding to the annular structure between the outer ring and the inner core of the annular crystallizer, engage the pulling head with the bottom support of the pulling mechanism, move the bottom support of the pulling mechanism upward, so that the pulling head part enters the annular crystallizer, and close the furnace door. S3. The electron beam melting furnace is pre-evacuated to below 10 Pa, and then the electron beam melting furnace is evacuated to a high vacuum of 5 × 10 Pa. -1 Below Pa; S4. Start the first electron gun located above the cooling bed to heat the alloy material placed in the cooling bed, and start the second electron gun located above the crystallizer to heat the drawing head. Gradually increase the input power until the material in the cooling bed and the surface of the drawing head are completely melted. S5. Select the stable heating power of the first electron gun according to the melting point and size of the material, and select the stable heating power of the second electron gun according to the melting point of the molten material and the diameter of the crystallizer. After the first electron gun and the second electron gun are working stably, start the feeding motor to push the alloy material in the feeding bin to the cooling bed, and maintain a feeding speed of 5-10 mm / min to make the alloy material melt and continue to flow into the annular crystallizer. S6. Based on the speed at which the molten alloy flows into the crystallizer, the billet pulling mechanism is set to a pulling speed of 2-5 mm / min, so that the melting of materials, solidification of the molten metal in the crystallizer, and the downward pulling of the billet by the billet pulling mechanism can be carried out continuously throughout the entire system. S7. After the ingot pulling mechanism pulls the bottom support to the specified position, it stops scanning the electron beam. After the furnace cools to 50°C, the upper part and the lower part of the furnace body are separated. The lower furnace body, hollow ingot and crystallizer core are pushed out of the furnace body through the hydraulic conveying device. Then the core located on the upper part of the ingot is removed, the ingot pulling head and the bottom support of the ingot pulling mechanism are separated, and the refractory high entropy alloy hollow billet is taken out.

2. The method for continuous casting of refractory high-entropy alloy hollow billets using an electron beam cooling bed according to claim 1, characterized in that, The scanning strategy adopted by the first electron gun is as follows: the electron beam width is 1.5~5mm, the scanning frequency is 200Hz, the scanning area is rectangular, its length is at least 100mm larger than the width of the feeding bin, its width is equivalent to the width of the cooling bed, and the scanning area is located in the center of the cooling bed.

3. The method for continuous casting of refractory high-entropy alloy hollow billets using an electron beam cooling bed according to claim 1, characterized in that, The scanning strategy of the second electron gun is as follows: the electron beam width is 1.5~5mm, the scanning frequency is 200Hz, and the scanning area is annular. Its outer diameter is 5~15mm smaller than the outer ring diameter of the crystallizer, and its inner diameter is 5~15mm larger than the inner core diameter of the crystallizer.

4. The method for continuous casting of refractory high-entropy alloy hollow billets using an electron beam cooling bed according to claim 1, characterized in that, The pulling speed and feeding speed keep the height of the molten metal level in the annular crystallizer between 30mm and 40mm.

Images