Suspension smelting equipment with downward pulling tube function and tube blank preparation method

Abstract

The present invention discloses a suspension smelting device and a method for preparing a tube billet with a downward tube drawing function. The device comprises a crucible structure consisting of a smelting zone and a solidification zone, and is equipped with a tube drawing mechanism composed of a main crystallizer and a tube head crystallizer. This device enables the tube billet to be smoothly drawn from the lower opening of a water-cooled copper crucible. The device's structure and operation first form a tube head flange in the tube head crystallizer. Next, the main crystallizer is raised to the crucible's solidification zone, causing the molten pool between the main crystallizer and the solidification zone to solidify and form a tube wall. The lower end of the tube wall engages the tube head flange, while the upper end contacts the liquid in the molten pool. The tube head crystallizer then grasps the tube head flange and drives the tube wall downward, allowing the molten pool to feed into the solidification zone, causing the tube wall to grow and extend. The drawn tube billet has an inner cross-sectional shape and dimensions determined by the cross-sectional shape of the main crystallizer, while its outer cross-sectional shape is identical to the inner cross-sectional shape of the crucible's solidification zone. The length of the tube billet is determined by the amount of material added to the crucible.

Description

Technical Field

[0001] The present invention relates to the field of smelting and casting of metals and alloys, and in particular to a suspension smelting device with a tube-pulling function and a tube blank preparation method. Background Art

[0002] Vacuum electromagnetic levitation melting technology (hereinafter referred to as "levitation melting") is an advanced material preparation technology. This technology avoids the contamination of the crucible material to the molten pool and eliminates the limitation of the crucible material on the melting temperature. Therefore, it is particularly suitable for melting active metals and alloys, refractory metals and alloys, as well as high-purity and ultra-pure metals and alloys.

[0003] The high-tech market is driving demand for pipes made from these high-end materials, such as magnetron sputtering targets, each of which can cost tens of thousands of yuan. Traditional methods for producing pipes involve rolling with a cross-rolling mill and threading with a pipe threading machine. However, the production volumes of high-end pipes cannot meet the requirements of these thermal processing techniques. Furthermore, many high-end materials exhibit poor thermoplasticity, making them impractical for hot working. Therefore, such high-end pipes should be produced using a casting method followed by suspension melting. However, conventional gravity casting techniques are nearly impossible to produce pipe blanks. This is because gravity casting requires a core rod placed in the mold. While the liquid metal injected into the mold solidifies from its melting point, the core rod cools at a lower temperature and experiences much less radial contraction than the material being cast. Consequently, the core rod exerts significant resistance to the shrinkage of the pipe blank during the cooling process, resulting in virtually all gravity-cast pipe blanks experiencing longitudinal cracking, preventing the production of intact pipe blanks. In addition, similar to the defects such as shrinkage, porosity, looseness, and cracks produced in ingots prepared by gravity casting, these metallurgical defects will also appear in gravity cast tubes. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of longitudinal cracking of the tube billet that is inevitable with gravity casting technology, and to eliminate metallurgical defects such as shrinkage cavities, porosity, looseness, and cracks that are common in gravity cast products. More importantly, this invention targets high-end materials and is a technology developed in suspension smelting equipment. It requires that during the entire tube billet drawing process, including melting, solidification, and cooling, no crucible materials or mold materials such as ceramic, quartz, and graphite are used. This eliminates the contamination of the tube metal by these materials and the restrictions they impose on melting and tube making temperatures. The present invention adopts the following technical solutions:

[0005] On the one hand, the present invention adopts a suspension melting device with a tube pulling function, comprising a vacuum furnace body, and a melting device and a tube pulling device installed in the vacuum furnace body;

[0006] The smelting device includes a water-cooled copper crucible and an induction coil, wherein the induction coil surrounds the water-cooled copper crucible;

[0007] A smelting zone is formed in the water-cooled copper crucible, and the position of the smelting zone corresponds to the position of the induction coil, and a solidification zone is formed below the smelting zone;

[0008] The tube drawing device includes a main crystallizer, a main crystallizer elevator, a tube head crystallizer and a tube drawing machine, wherein:

[0009] The main crystallizer is located in the solidification zone and has an outer diameter smaller than the inner diameter of the solidification zone; the main crystallizer is located in the inner hole of the bottom plate ring of the tube head crystallizer, and the upper end surface of the main crystallizer is aligned with or slightly higher than the upper end surface of the inner hole of the bottom plate ring and lower than the bottom surface of the water-cooled copper crucible; an initial cavity is formed between the portion of the main crystallizer located in the tube head crystallizer and the inner wall of the tube head crystallizer surrounding it;

[0010] A main crystallizer elevator comprises a first pull rod and a first driver, wherein the first pull rod is mounted on the bottom surface of the main crystallizer, extends downward through the vacuum seal to the bottom of the vacuum furnace body, and is connected to the first driver;

[0011] The tube head crystallizer is located at the bottom of the water-cooled copper crucible and includes a main body ring and a bottom plate ring arranged in an upper and lower manner. The main body ring includes a tube diameter section at the upper section and a flange section at the lower section. The cross-sectional shape and size of the inner hole of the tube diameter section are the same as the cross-sectional shape and size of the solidification zone. The inner hole of the flange section is larger than the inner hole of the tube diameter section. The bottom plate ring has an inner hole, and the shape and size of the inner hole match those of the main crystallizer.

[0012] The pipe drawing machine includes a drawing table, a second drawing rod and a second driver. The drawing table is installed on the lower end surface of the bottom plate ring, and the second drawing rod is installed on the bottom surface of the drawing table. The second drawing rod extends downward through the vacuum seal to the bottom of the vacuum furnace body and is connected to the second driver.

[0013] In another aspect, the present invention provides a method for preparing a tube blank using the aforementioned suspension smelting apparatus, the method comprising:

[0014] Step 1: The induction coil is energized to melt the material in the water-cooled copper crucible and keep it warm for a period of time, so that the bottom of the molten pool falls into the starting cavity formed by the crystallizer, and cools and solidifies on the upper surface of the main crystallizer and the flange section of the tube head crystallizer to form the flange of the tube blank;

[0015] Step 2: Start the first drive and slowly raise the main crystallizer so that the upper end surface of the main crystallizer rises and enters the solidification zone, so that the liquid metal is cooled and solidified on the outer periphery of the main crystallizer in the lower section of the solidification zone, forming the tube wall of the tube blank above the flange;

[0016] Step 3: Start the second driver, drive the second pull rod and the pulling table to drive the tube head crystallizer to move slowly downward. The tube head crystallizer drives the tube wall connected to the flange downward through the tube flange inside it. The molten pool in the smelting zone gradually flows downward through the gap between the main crystallizer and the inner wall of the solidification zone, and solidifies under the cooling effect of the main crystallizer and the inner wall of the solidification zone, so that the tube wall of the tube continues to grow and the length gradually increases.

[0017] Step 4: When the surface of the molten pool in the water-cooled copper crucible drops significantly, the height of the main crystallizer is appropriately increased to raise the position of the remaining molten pool to a position corresponding to the induction coil;

[0018] Step 5: When the surface of the remaining molten pool approaches the end face of the main mold, the induction coil stops energizing, the tube head mold continues to move downward, and the main mold rotates at a certain speed;

[0019] Step 6: When the tube billet stops growing, continue to pull down the tube head crystallizer, pull the broken end of the tube wall to the bottom of the lower mouth of the water-cooled copper crucible, and lower the main crystallizer to the bottom of the tube head crystallizer. At this time, you can open the furnace door of the vacuum furnace body, take out the tube head crystallizer and the tube billet, and then take out the tube billet from the tube head crystallizer.

[0020] The present invention has the following advantages:

[0021] In the tube drawing process, there is no core rod to prevent the radial contraction of the tube wall during the cooling process of the tube blank, so the radial thermal stress formed in the entire tube drawing process is small, eliminating the problem of overall longitudinal cracking that occurs when casting the tube blank using gravity casting technology.

[0022] The tube blanks produced by the tube drawing process are dense and free of the casting defects common in gravity casting. This is because the solidification process is sequential, from bottom to top. Liquid metal continuously feeds the solid-liquid interface as it develops upward, resulting in no shrinkage, porosity, or looseness in the drawn tube blanks. The temperature difference in the drawn tube blank is also from bottom to top, and the tube blank shrinks axially during cooling. Since its upper end is free, the thermal stress generated during cooling is minimal, and the probability of transverse cracks is also very small.

[0023] The apparatus of this invention eliminates the use of materials such as ceramic, quartz, and graphite for crucibles and molds during the melting and ingot drawing processes, thus avoiding contamination from these materials and eliminating the limitations on the production temperature imposed by these materials. This is of great significance for the melting and tube drawing process of high-purity metals, active metals, refractory metals, and alloys based on these metals.

[0024] The technology of the present invention can prepare tube blanks with the same or different shapes of inner and outer cross-sections after utilizing the auxiliary crystallizer, can prepare tube blanks with coaxial inner and outer walls, can use the same crucible to prepare tube blanks with different cross-sectional shapes and different cross-sectional sizes, and can also obtain a high tube drawing speed by lengthening the length of the auxiliary crystallizer.

[0025] After the equipment of the present invention is equipped with a continuous feeding device and a casting extension cylinder, ingots and tubes of large lengths can be continuously produced, and high production efficiency can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the overall diagram of the suspension smelting equipment;

[0027] Figure 2 This is a diagram of a melting device and a tube drawing device according to the first embodiment;

[0028] Figure 3 This is a diagram of a tube drawing device according to embodiment 1;

[0029] Figures 4a to 4f This is a flow chart of tube blank preparation in embodiment 1;

[0030] Figure 5a ~c is a diagram of the tube drawing device in the second embodiment;

[0031] Figure 6 Added a drawing of the extension tube for implementation modes 1 and 2;

[0032] Figure 7 This is a diagram of a continuous feeder for implementation modes one and two.

[0033] Among them, 1-water-cooled copper crucible, 2-induction coil, 3-vacuum furnace body, 4-induction power supply, 5-vacuum unit, 6-cooling system, 7-control system, 8-melting zone, 9-solidification zone, 10-molten pool, 11-main crystallizer, 12-first pull rod, 13-first drive, 14-tube head crystallizer, 15-pulling table, 16-second pull rod, 17-second drive, 20-main body ring, 21-tube diameter section, 22-flange section, 23-bottom plate ring, 24-sandwich structure, 25-initial cavity, 26-flange, 2 7-tube wall, 28-tube blank, 30-auxiliary crystallizer, 31-temperature measuring window, 32-infrared thermometer, 33-displacement sensor, 35-temperature sensor, 36-tension sensor, 37-continuous feeder, 38-tube extension tube, 39-feeding barrel, 40-feeding tube, 41-pusher, 42-rotation drive, 43-material, 44-push rod, 45-spiral blade, 46-weight sensor, 47-feeding barrel, 48-feeding valve, 49-feeding tube, 50-liquid level probe, 51-tube blank heater. DETAILED DESCRIPTION

[0034] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0035] Implementation method one:

[0036] like Figure 1 As shown, the levitation melting equipment includes a water-cooled copper crucible 1, an induction coil 2, a vacuum furnace 3, a vacuum unit 4, an induction power supply 5, a cooling system 6, and a control system 7. The water-cooled copper crucible 1 is installed in the vacuum furnace 3. After the vacuum unit 4 evacuates the vacuum furnace 3, the high-frequency current generated by the induction power supply 5 is input into the induction coil 2 surrounding the crucible. The resulting high-frequency electromagnetic field heats and melts the material in the water-cooled copper crucible 1. The cooling system 6 supplies cooling water to the water-cooled copper crucible 1, the induction coil 2, the vacuum furnace 3, the vacuum unit 4, and the induction power supply 5 to protect these devices. After the vacuum furnace 3 is evacuated, a protective gas, such as argon, can be filled into the vacuum furnace 3. In practice, most levitation melting processes are performed under argon protection. The control system 7 can be equipped with a PLC module to automatically control the operation of the equipment.

[0037] In this embodiment, if Figure 2 As shown, the tube pulling function is achieved by a tube drawing device. Specifically, the tube drawing device includes a melting device, a main crystallizer 11, a main crystallizer elevator, a tube head crystallizer 14, and a tube drawing machine. The melting device includes a water-cooled copper crucible 1 and an induction coil 2. The melting device is installed in a vacuum furnace 3.

[0038] In this embodiment, the water-cooled copper crucible 1 is used to complete the smelting process. The crucible wall can be made of a crucible used in conventional suspension smelting equipment in the prior art. For example, the crucible is made of a metal material, preferably copper or oxygen-free copper. To allow the electromagnetic field to penetrate the crucible wall and enter the crucible interior, the crucible is processed into a petal structure. To prevent the copper crucible from burning at high temperatures, a cooling circuit is built into each petal. The water-cooled copper crucible 1 in this embodiment differs from conventional water-cooled copper crucibles in the prior art in that it only includes a cylindrical crucible wall and lacks a crucible bottom.

[0039] In this embodiment, the water-cooled copper crucible 1 is divided into two working zones in the vertical direction. The upper working zone corresponds to the position of the induction coil 2, where the material is melted to form a molten pool 10. The lower zone is the area at the bottom of the molten pool 10 where cooling and solidification begin. These zones comprise the melting zone 8 and solidification zone 9 of the crucible, respectively. In one embodiment, the cross-sectional shape and dimensions of the solidification zone 9 can be the same as or different from those of the melting zone 8. In one embodiment, the cross-sectional shape of the solidification zone 9 can be circular, square, rectangular, polygonal, or other shapes. It will be appreciated that the cross-sectional shape and dimensions depend on the desired cross-sectional shape and dimensions of the outer surface of the tube blank. The height of the solidification zone 9 should ensure that the molten metal forms a surface solidification layer of a certain thickness after descending into this zone. To this end, the height of the solidification zone 9 is 1 / 8 to 4 / 5 of the total height of the water-cooled copper crucible 1, with 1 / 2 to 2 / 3 being optimal.

[0040] In this embodiment, if Figure 3 As shown, the main crystallizer 11 is located in the solidification zone 9 during the tube drawing process. The molten metal pool 10 cools and solidifies while flowing through the surface of the main crystallizer 11, forming the inner wall of the tube 28. It will be understood that the cross-sectional shape and size of the main crystallizer 11 are determined by the cross-sectional shape of the inner wall of the tube 28 to be produced. Its outer diameter is smaller than the inner diameter of the solidification zone 9, and the difference between the outer diameter of the main crystallizer 11 and the inner diameter of the solidification zone 9 is slightly greater than the thickness of the tube 28 to be produced.

[0041] In this embodiment, the main crystallizer 11 is made of a metal material, such as stainless steel, a high-temperature alloy, titanium, a titanium alloy, and copper, with copper being the preferred material. A cooling circuit is provided in the main crystallizer 11 to cool the molten metal and protect the main crystallizer from high temperatures.

[0042] In this embodiment, the main mold elevator, which enables the main mold 11 to be raised and lowered, comprises a first tie rod 12 and a first actuator 13. The first tie rod 12 is mounted on the bottom surface of the main mold 11 and is capable of supplying cooling water to the main mold 11. The first tie rod 12 extends downward through a vacuum seal to the underside of the vacuum furnace body 3 and is connected to the first actuator 13. In this embodiment, the first actuator 13 can be driven by various means, such as an electric motor, hydraulics, or pneumatics. The first actuator 13 can also have a rotation function.

[0043] In this embodiment, if Figure 3As shown, the tube head crystallizer 14 is located at the bottom of the water-cooled copper crucible 1 at the beginning of the tube drawing process and has an annular structure. The tube head crystallizer 14 includes a main body ring 20 and a bottom plate ring 23, and the two are assembled into a whole. The main body ring 20 includes a tube diameter section 21 located in the upper section and a flange section 22 located in the lower section. The shape and size of the cross section of the inner hole of the tube diameter section 21 are the same as the shape and size of the cross section of the solidification zone 9, and depend on the shape and size of the outer periphery of the cross section of the tube blank to be prepared. At the beginning of the tube drawing process, the main body ring 20 is sealed and connected to the bottom of the water-cooled copper crucible 1. The shape and size of the cross section of the inner hole of the flange section 22 depend on the requirements for the flange of the tube blank to be prepared, and are larger than the inner hole of the tube diameter section 21. The bottom plate ring 23 is provided with an inner hole, and the shape and size of the inner hole match those of the main crystallizer 11 ( Figure 3 viewing angle), that is, depends on the cross section of the inner wall of the tube blank to be produced.

[0044] In this embodiment, both the main body ring 20 and the bottom plate ring 23 are provided with a sandwich structure 24, and a cooling circuit is formed in the sandwich.

[0045] In this embodiment, at the beginning of the tube drawing process, the main mold 11 is coaxially positioned with the tube head mold 14 within the inner bore of the bottom plate ring 23, sealing the path for molten metal leakage. The main mold 11 is able to move up and down within the inner bore. The upper end surface of the main mold 11 is aligned with or slightly higher than the upper end surface of the inner bore of the bottom plate ring 23, and is lower than the bottom surface of the water-cooled copper crucible 1. The portion of the main mold 11 located within the tube head mold 14 and the surrounding inner wall of the tube head mold 14 form a cavity, referred to in this embodiment as the initial cavity 25. The tube head mold's primary function is to contain the molten metal at the bottom of the molten pool 10, allowing it to cool and solidify within the initial cavity 25, forming the flange and bottom plate at the lower end of the tube blank. Its second function is to, during the subsequent tube drawing phase, grasp the tube blank flange as it descends, pulling the molten pool 10 above the flange and bottom plate downward, thereby forming a tube wall of gradually increasing length. During the tube drawing process, the flange at the end of the tube billet acts as a gripper for drawing the tube billet down.

[0046] In this embodiment, combined with Figure 3 As shown, the tube drawing machine is a device that draws the tube head mold downward. It includes a drawing platform 15, a second tie rod 16, and a second actuator 17. The drawing platform 15 is mounted on the lower end surface of the base ring 23. The second tie rod 16 is mounted on the bottom surface of the drawing platform 15 and is capable of supplying water to the tube head mold 14. The second tie rod 16 extends downward through a vacuum seal to the bottom of the vacuum furnace body 3 and is connected to the second actuator 17. The second actuator 17 can be driven by various means, such as motor, hydraulic, or pneumatic, but is preferably driven by a servo motor.

[0047] As shown in FIG4 , the preparation process of drawing a tube blank in this embodiment is as follows:

[0048] Step 1: Start the induction power supply 5 to melt the material and keep it warm for a period of time, so that the bottom of the molten pool 10 falls into the starting cavity 25 formed by the crystallizer, and cools and solidifies on the upper surface of the main crystallizer 11 and the flange section 22 of the tube head crystallizer 14 to form the flange 26 of the tube blank 28. Figure 4a .

[0049] Step 2: Start the first drive 13 and slowly raise the main crystallizer 11. The upper end surface of the main crystallizer 11 is raised to enter the solidification zone 9 of the crucible, so that the liquid metal is cooled and solidified on the outer periphery of the main crystallizer 11 in the lower section of the solidification zone 9, forming a tube wall 27 on the flange 26 of the tube blank. Figure 4b .

[0050] Step 3: Start the second driver 17, drive the second pull rod 16 and the pulling platform 15 to drive the tube head crystallizer 14 to move slowly downward. The tube head crystallizer 14 drives the tube wall 27 connected to the flange 26 downward through the tube flange 26 inside it. The molten pool 10 in the crucible melting zone 8 gradually flows downward through the gap between the main crystallizer 11 and the inner wall of the crucible solidification zone 9, and solidifies under the cooling effect of the main crystallizer 10 and the crucible wall, so that the tube wall of the tube continues to grow and the length gradually increases. Figure 4c .

[0051] Step 4: When the surface of the molten pool 10 in the crucible is significantly lowered, the height of the main crystallizer 11 is appropriately increased, and the position of the remaining molten pool 10 is raised to the position corresponding to the induction coil 2 to improve the heating effect and maintain the melting state of the material. Figure 4d .

[0052] Step 5: When the surface of the remaining molten pool 10 approaches the end face of the main crystallizer 11, the material is too small to be affected by the electromagnetic field and solidifies. The upper end of the tube 28 stops growing due to lack of molten metal replenishment, and the tube wall is broken. At this time, the induction power supply 5 can be turned off. The tube head crystallizer 14 continues to move downward, while the main crystallizer 11 rotates at a certain speed. This rotation can release the adhesion between the tube wall 27 formed by drawing and the surface of the main crystallizer 11, reduce the resistance to drawing the tube, and improve the quality of the tube. Figure 4e .

[0053] Step 6: After the induction power supply 5 is turned off and the tube blank 28 stops growing, it is necessary to continue to pull down the tube head crystallizer 14 and pull the broken end of the tube wall 27 to the bottom of the crucible. Then, lower the main crystallizer 11 to the bottom of the tube head crystallizer 14. At this time, the door of the vacuum furnace body 3 can be opened to take out the tube head crystallizer 14 and the tube blank 28. Then, take out the tube blank 28 from the tube head crystallizer 14. Figure 4f .

[0054] The shape and size of the inner cross-section of the tube blank 28 obtained by the above-described technique are determined by the cross-section of the main crystallizer 11, and the outer cross-section is determined by the inner cross-section of the tube diameter section 21 of the main ring of the tube head crystallizer, which is the same as the inner cross-section of the crucible solidification zone 9. The length of the tube blank 28 is determined by the amount of material added to the crucible.

[0055] Implementation method 2:

[0056] As another embodiment, as shown in Figure 5, the purpose is to prepare a tube blank 28 whose shape and outer diameter are different from the inner shape and inner diameter of the crucible solidification zone 9. To achieve this purpose, an auxiliary crystallizer 30 needs to be added. The auxiliary crystallizer 30 is annular and is installed at the bottom of the water-cooled copper crucible 1, coaxial with the crucible. When the auxiliary crystallizer 30 is used, only the melting zone 8 is provided in the water-cooled copper crucible 1, and no solidification zone 9 is provided. The auxiliary crystallizer 30 becomes the crucible solidification zone. It can be understood that the cross-sectional shape and size of the inner hole of the auxiliary crystallizer 30 should be designed according to the shape and size of the outer cross section of the tube blank 28 to be prepared. The auxiliary crystallizer 30 can be divided into three cases according to its inner diameter: smaller than the inner diameter of the lower mouth of the crucible, see Figure 5a ; larger than the inner diameter of the crucible bottom but smaller than the outer diameter of the crucible bottom, see Figure 5b ; and greater than the outer diameter of the crucible, see Figure 5c When the inner diameter of the auxiliary crystallizer 30 is larger than the outer diameter of the crucible, the diameters of the upper and lower inner holes of the auxiliary crystallizer 30 are not equal, the diameter of the upper section of the hole must be smaller than the outer diameter of the lower opening of the crucible, and the shape and size of the cross section of the lower section should be consistent with the shape and size of the outer cross section of the tube blank 28 to be prepared.

[0057] In this embodiment, the cross-sectional shape and size of the main crystallizer 11 still depend on the shape and size of the inner cross-section of the tube blank 28 to be prepared. The tube head crystallizer 14 is arranged on the lower end face of the auxiliary crystallizer 30. The shape and size of the inner hole cross-section of the tube diameter section 21 of the tube head crystallizer 14 are the same as the inner cross-section of the auxiliary crystallizer 30, and the shape and size of the inner hole cross-section of its bottom plate ring 23 match the main crystallizer 11.

[0058] In this embodiment, the main crystallizer 11 is located in the inner hole of the bottom plate ring 23 of the tube head crystallizer 14, and its upper end face is aligned with or slightly higher than the upper end face of the inner hole of the bottom plate ring 23, and is lower than the upper end face of the auxiliary crystallizer 30, forming a starting cavity 25 between the tube head crystallizer 14 and the main crystallizer 11.

[0059] In this embodiment, the tube blank drawing process is similar to the process in the first embodiment, specifically:

[0060] Step 1: After the induction power supply 4 is started, the bottom of the molten pool 10 falls into the starting cavity 25 between the main crystallizer 11 and the tube head crystallizer 14 after passing through the auxiliary crystallizer 30, forming the flange 26 of the tube blank 28.

[0061] Step 2: Raise the main crystallizer 11 so that the upper end surface of the main crystallizer 11 rises and enters the auxiliary crystallizer 30, so that the liquid metal cools and solidifies in the gap between the main crystallizer 11 and the auxiliary crystallizer 30, forming the tube wall 27 of the tube blank above the flange 26.

[0062] Step 3: Move the tube head crystallizer 14 slowly downward. The tube head crystallizer 14 drives the tube wall 27 above it to move downward through the tube blank flange 26. The molten pool 10 in the crucible flows downward and solidifies under the cooling effect of the main crystallizer 11 and the auxiliary crystallizer 30, so that the length of the tube blank 28 gradually increases.

[0063] The subsequent steps are exactly the same as the tube drawing process in the first embodiment, until the tube drawing process is completed and the tube blank 28 is taken out.

[0064] In this embodiment, water is primarily used as the cooling medium in the petals of the water-cooled copper crucible 1, in the main crystallizer 11, in the main ring 20 and bottom plate ring 23 of the tube head crystallizer, and in the auxiliary crystallizer 30. In this case, the water circuit must have a closed structure to prevent water from leaking into the vacuum furnace body 3. If accelerated cooling is required, dry ice, liquid nitrogen, liquid oxygen, liquid argon, liquid helium, or other liquid inert gases may also be used as the cooling medium. When using an inert gas such as liquid argon or liquid helium as the cooling medium, holes can be opened in the surface of the crystallizer to allow the low-temperature gas to directly cool the surface of the molten pool.

[0065] In the first and second embodiments described above, the height of the crucible solidification zone 9 (embodiment 1) should ensure that the molten metal forms a surface solidification layer of a certain thickness when it descends into this section. If the solidification zone 9 is too short, the molten metal will be pulled out of the crucible before it is fully solidified, causing leakage during the tube drawing process. If the solidification zone 9 is too long, it will increase the resistance during the tube drawing process, causing cracks in the tube blank 28, or even causing the tube blank to break. Taking these factors into consideration, the height of the solidification zone 9 can be designed within a range of 1 / 8 to 4 / 5 of the total height of the water-cooled copper crucible 1, with a range of 1 / 2 to 2 / 3 being optimal. When the auxiliary crystallizer 30 is used (embodiment 2), there is no solidification zone in the crucible. In this case, the height of the auxiliary crystallizer 30 needs to be designed. The design principles are the same as those for designing the height of the crucible solidification zone 9. That is, the height of the auxiliary crystallizer 30 can be designed within a range of 1 / 8 to 4 / 5 of the total height of the water-cooled copper crucible 1, with a range of 1 / 2 to 2 / 3 being optimal.

[0066] In the above-mentioned embodiments one and two, after determining the height of the solidification zone 9 (or the auxiliary crystallizer 30), in order to ensure the smooth progress of the tube drawing process and the quality of the ingot, it is necessary to control the molten pool temperature and the tube drawing speed (i.e., the pulling speed of the tube head crystallizer 14). Too high a melting temperature will cause insufficient solidification of the molten pool in the solidification zone 9, resulting in leakage of molten metal during tube drawing; too low a melting temperature will cause the molten pool to solidify before entering the solidification zone 9, and the molten metal cannot be smoothly replenished into the solidification zone, resulting in interruption of the tube drawing process. The melting temperature should be controlled within the range of 30 to 300°C above the melting point of the material, and the best range is 80 to 150°C above the melting point of the material. In order to control the melting temperature, a temperature measuring window 31 is provided on the top of the vacuum furnace body 3, and an infrared thermometer 32 is installed on the temperature measuring window 31, see Figure 6 The temperature of the molten pool 10 is measured using an infrared thermometer 32. Based on the measured temperature, the molten pool temperature is adjusted by varying the output power of the induction power supply 5. A more convenient method for adjusting the molten pool is to set a closed-loop control mode in the induction power supply 5, set a control value for the molten pool temperature, and input the measured temperature into the power supply's PID module for processing, thereby automatically controlling the power.

[0067] In the above-mentioned embodiments 1 and 2, the tube drawing speed also needs to be strictly controlled: if the speed is too fast, the molten metal entering the solidification zone 9 will leave the lower mouth of the water-cooled copper crucible 1 before it is completely solidified, causing the molten metal to leak, or cause greater stress in the tube wall, resulting in cracks, damaging the surface quality of the tube blank, or even breaking the tube blank; if the speed is too slow, the time the molten metal stays in the solidification zone 9 will be prolonged, resulting in an expansion of the solidification range, and the molten metal cannot smoothly enter the solidification zone 9, which will also cause the tube drawing process to be interrupted. In addition, a too slow tube drawing speed will also reduce production efficiency. The tube drawing speed should be determined based on the characteristics of the material of the tube and the diameter of the prepared tube blank 28, and should be selected within the range of 0.1 to 100 mm / min, with a commonly used range of 1 to 20 mm / min. See. Figure 6 The displacement sensor 33 installed on the second pull rod 16 and located below the furnace body measures the displacement and pulling speed of the tube blank when it is pulled downward. The speed value is input into the PLC module and compared with the set value to control the driver of the tube drawing machine.

[0068] In the above-mentioned embodiments 1 and 2, at the beginning of tube drawing, the initial tube drawing speed is set first. During the tube drawing process, the tube drawing speed needs to be adjusted according to the tube blank temperature and the tube drawing stress. The tube blank temperature refers to the surface temperature of the tube blank 28 at the lower end of the water-cooled copper crucible 1 or the lower end of the auxiliary crystallizer 30. The temperature should be controlled within the range of 20 to 200°C below the melting point of the material, and preferably within the range of 50 to 100°C. The tube blank temperature is measured by a temperature sensor 35. The temperature sensor 35 can be a thermocouple sensor installed at the lower end of the water-cooled copper crucible 1 or the lower end of the auxiliary crystallizer 30, see Figure 6, or you can use an infrared thermometer installed on the temperature measuring window of the furnace door. The temperature measuring points can be 1, 2, 3 or more, and the measurement value of the highest temperature point shall prevail.

[0069] In the first and second embodiments described above, the tube drawing stress refers to the tensile stress induced in the tube wall of the tube blank 28 during the tube drawing process. This stress is generated within the crucible solidification zone 9 or within the auxiliary crystallizer 30 and is caused by the friction of the tube wall of the drawn tube blank moving along the inner wall of the solidification zone 9 or the auxiliary crystallizer 30. The tube drawing stress is controlled to be 1 / 10 to 1 / 5 of the ultimate strength of the tube blank 28 material at a temperature 50°C below the melting point. The tube drawing stress can be measured using a tension sensor 36 installed at the lower end of the second drawbar 26 of the tube drawing machine, see [Referring to FIG. 1]. Figure 6 The drawing stress can be calculated based on the pulling force and the cross-sectional area of the tube wall. The measured tube temperature and drawing stress values are input into the control system's PLC module for processing, which then outputs instructions to the tube drawing machine's driver to adjust the tube drawing speed. If the tube temperature is too high or the stress is too high, the drawing speed should be reduced; if the temperature is too low or the stress is too low, the drawing speed can be increased. Control methods include manual control and various automatic control methods, with program control technology being preferred.

[0070] In the above embodiments 1 and 2, a continuous tube drawing device and method are also designed for the bottom tube drawing technology: a continuous feeder 37 is set on the top of the vacuum furnace body 3, and a tube drawing extension tube 38 is added at the bottom. Figure 6-7. Specifically, the continuous feeder 37 is used to add granular materials, including a feeding barrel 39, a feeding pipe 40, a pusher 41 and a rotary driver 42. The sealed feeding barrel 39 is installed on the furnace cover of the vacuum furnace body 3 in a horizontal form, and the material 43 to be added is loaded in the material tank 47; the feeding pipe 40 is sealedly installed under the front section of the feeding barrel 39, and extends into the interior of the vacuum furnace body 3 through a vacuum seal, so that the feeding barrel 39 is connected to the vacuum furnace body 3, and the pipe mouth of the feeding barrel 39 is located above the water-cooled copper crucible 1; the pusher 41 includes a pushing rod 44 and a spiral blade 45 installed around the pushing rod 44, and the pushing rod 44 extends out of the feeding barrel 39 from the rear end of the feeding barrel 39 in a sealed manner; the rotary driver 42 is installed behind the feeding barrel 39, and its transmission shaft is connected to the end of the pushing rod 44. When the rotary actuator 42 is activated, it drives the push rod 44 and spiral blade 45 in the feeding barrel 39 to rotate, pushing the material in the feeding barrel 39 into the feeding tube 40. The material then moves along the feeding tube 40 and falls into the crucible 1. By adjusting the rotation speed of the rotary actuator 42, the speed at which the material 43 is fed into the crucible can be changed. A weight sensor 46 can be installed below the feeding barrel 39. After the measured value of the material weight change is input into the PLC module of the control system, the driver speed can be adjusted to control the feeding speed and amount of material added. If a large amount of material needs to be added, a material tank 47 can be installed above the feeding barrel in a sealed manner to accommodate a larger amount of material 43. The bottom of the material tank 47 is sealedly connected to the feeding barrel 39 via a feed valve 48 and a feed tube 49. When material needs to be added to the feeding barrel 39, the feed valve 48 is opened to allow the material 43 in the material tank 47 to fall into the feeding barrel 39.

[0071] In the first and second embodiments described above, the tube extension tube 38 is provided to accommodate long tube blanks 28. It is sealed and mounted at the bottom of the vacuum furnace body 3, communicating with the furnace interior and located below the water-cooled copper crucible 1. With the extension tube 38 installed, the second actuator 17 is mounted below the tube extension tube 38. The second pull rod 16 sealably extends through the bottom of the tube extension tube 38, extending upward into the vacuum furnace body 3 and engaging the tube head mold 14 via the drawing platform 15.

[0072] It is understood that when using continuous tube drawing technology, the aforementioned parameters still need to be monitored and controlled, including melting temperature, ingot drawing speed, tube temperature, and tube drawing stress. However, the difference is that the liquid level of the molten pool 10 also needs to be monitored and controlled. If the liquid level is too low, the temperature at the bottom of the molten pool 10 will be too high, causing molten metal leakage when the tube head crystallizer 14 descends, resulting in a failure in the ingot drawing process. Further decreases in the liquid level will lead to electromagnetic load mismatch, a decrease in the molten pool 10 temperature, or even incomplete melting of the material, causing the ingot drawing process to be interrupted or difficult. If the liquid level is too high, the melting temperature will decrease, incomplete melting of the material, or the temperature at the bottom of the molten pool will be too low, which will also cause a failure in the ingot drawing process or damage the surface quality of the drawn tube. The height of the molten pool liquid level is controlled to be 1 / 3 to 4 / 5 of the height of the melting zone 8 in the crucible, and preferably 1 / 2 to 2 / 3 of the height of the melting zone 8 in the crucible.

[0073] In the above-mentioned embodiments 1 and 2, after the pulling speed is determined, the liquid level can be controlled by limiting the feeding speed. The liquid level control process includes: measuring the liquid level, inputting the liquid level data into the control system's PLC module, comparing it with the set liquid level, determining the operating speed of the feeding driver according to the program in the module, and issuing a driving speed instruction to the rotary driver 42. The liquid level is measured using a liquid level probe 50 installed on the temperature measuring window 31 at the top of the furnace body. There are many methods for measuring the liquid level, such as ultrasonic ranging, laser ranging, radar (electromagnetic wave) ranging, etc. The present invention designs two methods for measuring the liquid level using a camera. Method 1 is to install a camera on the temperature measuring window 31 at the top of the vacuum furnace body 3, use the camera to capture an image of the water-cooled copper crucible 1, input the image into the PLC module, compare the liquid surface position with the size of the crucible petals, and calculate the liquid level height. Method 2 is to use two cameras to simultaneously capture the interior of the water-cooled copper crucible 1, and calculate the liquid level height based on the liquid surface position in the image and the distance and angle between the two cameras.

[0074] In the above-mentioned embodiments 1 and 2, Figure 6 As shown, a tube heater 51 is also provided. It is installed below the water-cooled copper crucible 1 or below the auxiliary crystallizer 30, surrounding the tube 28 being drawn. The heater can use either resistance heating or induction heating, and the heating temperature is adjustable. The heater's height depends on the required heat treatment range for the drawn ingot. Its purpose is to eliminate thermal stresses in the drawn ingot or to achieve the desired phase structure. Specific embodiment:

[0076] The present invention provides a specific embodiment to facilitate a better understanding of the present invention.

[0077] This embodiment is an example of preparing a high-purity zirconium metal rotary target. Figure 1-2The suspension smelting-continuous tube drawing equipment uses an induction power supply with a power of 300kW and a frequency of 10kHz. In this equipment, the tube drawing device consists of four parts: the main crystallizer, the main crystallizer elevator, the tube head crystallizer, and the tube drawing machine.

[0078] In the equipment, the water-cooled copper drawn tube crucible with a petal structure is cylindrical, with an inner diameter of 120mm and a height of 250mm, and is installed in a stainless steel vacuum furnace body.

[0079] The tube head mold is assembled from a main ring and a base ring. The main ring is divided into a pipe diameter section and a flange section. The upper pipe diameter section has an inner diameter of 123mm and a height of 20mm; the middle flange section has an inner diameter of 160mm and a height of 20mm; and the base ring has an inner diameter of 100mm and a height of 30mm. Both the main ring and the base ring have a water jacket. The tube head mold is mounted on the drawing table of the tube drawing machine. A tie rod is connected to the drawing table at its upper end and extends through a vacuum seal to the bottom of the vacuum furnace to connect to the tube head mold's drive.

[0080] The main mold is a closed cylinder housed within the tube head mold. It has an outer diameter of 99.5 mm and a height of 30 mm. Its outer edge and the inner edge of the tube head mold form an annular space—the starting cavity. The main mold's cylindrical structure provides a channel for circulating cooling water. The upper end of the pull rod of the main mold elevator is connected to the main mold. The lower end is raised to the bottom of the vacuum furnace through a vacuum seal and then connected to the main mold's drive.

[0081] In the furnace body, a resistance heater with an inner diameter of 200 mm is installed at a distance of 50 mm below the tube head crystallizer.

[0082] Before operation, adjust the position of the tube head mold so that its upper end face is in close contact with the lower end face of the crucible. Adjust the position of the main mold into the tube head mold so that its upper end face is aligned with the upper end face of the inner hole of the tube head mold bottom plate ring. After loading 15kg of terbium metal raw material into the crucible, start the resistance heater and heat it to 600℃, then maintain the temperature.

[0083] The furnace is then evacuated and filled with argon, and the induction power supply is activated to heat the crucible. After 8 minutes, the crucible is completely melted and then held warm for 2 minutes. The bottom of the molten pool flows into the annular space between the tube head mold and the main mold, where it cools and solidifies, forming the flange and end cap of the tube blank. Following these operations, the main mold is simultaneously raised so that its upper end is 20 mm above the lower end of the crucible. The tube head mold is then lowered while maintaining the power output of the induction power supply. The pull rod is then controlled to move at a speed of 50 mm / min. During this process, the bottom of the molten pool cools and solidifies as it passes over the outer surface of the main mold, joining the flange and end cap already formed in the tube head mold to form the tube wall. As the pull rod continues to move downward, the tube head mold pulls down the tube flange, driving the already formed tube wall, which is bonded to the flange, downward. The bottom of the molten pool, above the upper end cap, also moves downward, cooling and solidifying as it passes over the surface of the main mold, increasing the length of the tube wall. The tube blanks drawn from each are heat treated while passing through the heater.

[0084] During the tube drawing process, the surface of the molten pool in the crucible continuously descended. When the remaining molten pool weighed approximately 2 kg, it solidified due to insufficient mass to support the induction power supply. As the tube head mold continued to descend, the upper end of the tube wall separated from the solidified material, at which point the induction power supply was shut off. The induction power supply operated for a total of 18 minutes. The tube head mold continued to descend, and when the upper end of the tube was below the heater, the resistance heater was turned off.

[0085] After the tube billet has cooled, open the vacuum furnace door, drive the main mold down to a level below the head mold, remove the head mold from its pulling table, and then remove the tube billet, along with the head mold, out of the furnace. Remove the bottom plate ring of the head mold to remove the tube billet.

[0086] The resulting tube blank has an outer diameter of approximately 122 mm, an inner diameter of approximately 99 mm, a thickness of approximately 11.5 mm, a length of approximately 430 mm, and weighs approximately 10 kg. Both the inner and outer surfaces are relatively smooth and free of cracks. After removing the flange and upper end cap, the remaining length is approximately 400 mm. The upper and lower end surfaces show that the blank is dense, free of defects such as shrinkage cavities, porosity, and looseness. Machining the tube blank yields a sputtering target with an inner diameter of 100 mm, an outer diameter of 120 mm, a thickness of 10 mm, and a length of approximately 400 mm. The remaining material from the removed flange, end cap, and crucible is uncontaminated and can be recycled.

[0087] The foregoing is an example of the best mode of carrying out the present invention. Any portion not described in detail herein is common knowledge within the skill of one of ordinary skill in the art. The scope of protection of the present invention is determined by the claims. Any equivalent transformation based on the technical teachings of the present invention is also within the scope of protection of the present invention.

Claims

1. A suspension melting device with a tube pulling function, comprising a vacuum furnace body, a melting device and a tube pulling device installed in the vacuum furnace body; The smelting device includes a water-cooled copper crucible and an induction coil, wherein the induction coil surrounds the water-cooled copper crucible; It is characterized in that A melting zone is formed in the water-cooled copper crucible, and the position of the melting zone corresponds to the position of the induction coil, and a solidification zone is formed below the melting zone; The tube drawing device includes a main crystallizer, a main crystallizer elevator, a tube head crystallizer and a tube drawing machine, wherein: The main crystallizer is located in the solidification zone and has an outer diameter smaller than the inner diameter of the solidification zone; the main crystallizer is located in the inner hole of the bottom plate ring of the tube head crystallizer, and the upper end surface of the main crystallizer is aligned with or slightly higher than the upper end surface of the inner hole of the bottom plate ring and lower than the bottom surface of the water-cooled copper crucible; an initial cavity is formed between the portion of the main crystallizer located in the tube head crystallizer and the inner wall of the tube head crystallizer surrounding it; A main crystallizer elevator comprises a first pull rod and a first driver, wherein the first pull rod is mounted on the bottom surface of the main crystallizer, extends downward through the vacuum seal to the bottom of the vacuum furnace body, and is connected to the first driver; The tube head crystallizer is located at the bottom of the water-cooled copper crucible and includes a main body ring and a bottom plate ring arranged in an upper and lower manner. The main body ring includes a tube diameter section at the upper section and a flange section at the lower section. The cross-sectional shape and size of the inner hole of the tube diameter section are the same as the cross-sectional shape and size of the solidification zone. The inner hole of the flange section is larger than the inner hole of the tube diameter section. The bottom plate ring has an inner hole, and the shape and size of the inner hole match those of the main crystallizer. The pipe drawing machine includes a drawing table, a second drawing rod and a second driver. The drawing table is installed on the lower end surface of the bottom plate ring, and the second drawing rod is installed on the bottom surface of the drawing table. The second drawing rod extends downward through the vacuum seal to the bottom of the vacuum furnace body and is connected to the second driver.

2. The suspension smelting equipment according to claim 1, characterized in that: The water-cooled copper crucible is divided into a melting zone and a solidification zone in the height direction, wherein the melting zone corresponds to the position of the induction coil, and the solidification zone is located below the melting zone.

3. The suspension smelting equipment according to claim 1, characterized in that: The tube drawing device also includes an auxiliary crystallizer installed at the bottom of the water-cooled copper crucible. The melting zone extends to the bottom end of the water-cooled copper crucible in the water-cooled copper crucible. The melting zone corresponds to the position of the induction coil, and a solidification zone is formed in the auxiliary crystallizer.

4. The suspension smelting equipment according to claim 3, characterized in that: The inner diameter of the auxiliary crystallizer is smaller than the inner diameter of the lower opening of the water-cooled copper crucible; or, larger than the inner diameter of the lower opening of the water-cooled copper crucible but smaller than the outer diameter of the lower opening of the crucible; Or, it is larger than the outer diameter of the water-cooled copper crucible, the inner hole of the auxiliary crystallizer has unequal diameters at the upper and lower ends, the diameter of the upper section of the hole is smaller than the outer diameter of the lower end of the water-cooled copper crucible, and the shape and size of the lower section match the tube blank to be prepared.

5. The suspension smelting equipment according to claim 3, characterized in that: The tube head crystallizer is arranged on the lower end face of the auxiliary crystallizer. The shape and size of the inner hole cross section of the tube diameter section of the tube head crystallizer are the same as those of the auxiliary crystallizer. The shape and size of the inner hole cross section of its bottom plate ring match those of the main crystallizer. The upper end face of the main crystallizer is lower than the upper end face of the auxiliary crystallizer.

6. The suspension smelting equipment according to claim 1 or 2, characterized in that: The height of the solidification zone is 1 / 8 to 4 / 5 of the total height of the water-cooled copper crucible.

7. The suspension smelting equipment according to claim 6, characterized in that: The height of the solidification zone is 1 / 2 to 2 / 3 of the total height of the water-cooled copper crucible.

8. The suspension smelting equipment according to claim 1, characterized in that: A continuous feeder is provided on the top of the vacuum furnace body, and a tube extension tube is added at the bottom. The tube extension tube is sealed and installed at the bottom of the vacuum furnace body, communicated with the furnace, and located below the water-cooled copper crucible.

9. A method for preparing a tube blank, using the suspension smelting equipment according to any one of claims 1 to 8, characterized in that: The preparation method comprises: Step 1: The induction coil is energized to melt the material in the water-cooled copper crucible and keep it warm for a period of time, so that the bottom of the molten pool falls into the starting cavity formed by the crystallizer, and cools and solidifies on the upper surface of the main crystallizer and the flange section of the tube head crystallizer to form the flange of the tube blank; Step 2: Start the first drive and slowly raise the main crystallizer so that the upper end surface of the main crystallizer rises and enters the solidification zone, so that the liquid metal is cooled and solidified on the outer periphery of the main crystallizer in the lower section of the solidification zone, forming the tube wall of the tube blank above the flange; Step 3: Start the second driver, drive the second pull rod and the pulling table to drive the tube head crystallizer to move slowly downward. The tube head crystallizer drives the tube wall connected to the flange downward through the tube flange inside it. The molten pool in the smelting zone gradually flows downward through the gap between the main crystallizer and the inner wall of the solidification zone, and solidifies under the cooling effect of the main crystallizer and the inner wall of the solidification zone, so that the tube wall of the tube continues to grow and the length gradually increases. Step 4: When the surface of the molten pool in the water-cooled copper crucible drops significantly, the height of the main crystallizer is appropriately increased to raise the position of the remaining molten pool to a position corresponding to the induction coil; Step 5: When the surface of the remaining molten pool approaches the end face of the main mold, the induction coil stops energizing, the tube head mold continues to move downward, and the main mold rotates at a certain speed; Step 6: When the tube billet stops growing, continue to pull down the tube head crystallizer, pull the broken end of the tube wall to the bottom of the lower mouth of the water-cooled copper crucible, and lower the main crystallizer to the bottom of the tube head crystallizer. At this time, you can open the furnace door of the vacuum furnace body, take out the tube head crystallizer and the tube billet, and then take out the tube billet from the tube head crystallizer.

10. The method for preparing a tube blank according to claim 9, wherein: In step 1, the smelting temperature of the material in the water-cooled copper crucible is 30 to 300° C. higher than the melting point of the material; In step 3, the tube head crystallizer moves downward at a tube drawing speed of 0.1 to 100 mm / min; In step 3, the tube temperature is controlled within a range of 20 to 200° C. below the melting point of the material; the tube drawing stress is controlled within a range of 1 / 10 to 1 / 5 of the strength limit of the tube material at a temperature 50° C. below the melting point; and the tube drawing speed is adjusted during the tube drawing process according to the tube temperature and the tube drawing stress.

11. The method for preparing a tube blank according to claim 10, wherein: In step 1, the smelting temperature of the material in the water-cooled copper crucible is 80 to 150° C. higher than the melting point of the material.

12. The method for preparing a tube blank according to claim 10, wherein: In step 3, the tube head crystallizer moves downward at a tube drawing speed of 1 to 20 mm / min.

13. The method for preparing a tube blank according to claim 10, wherein: In step 3, the temperature of the tube is controlled within the range of 50 to 100° C. lower than the melting point of the material.

14. The method for preparing a tube blank according to claim 9 or 10, wherein: The height of the molten pool liquid level is maintained at 1 / 3 to 4 / 5 of the height of the smelting zone.

15. The method for preparing a tube blank according to claim 14, wherein: The height of the molten pool liquid level is maintained at 1 / 2 to 2 / 3 of the height of the smelting zone.

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