A high-temperature superconducting strong magnetic field homogenization heat treatment method and device for large-size rare earth magnesium alloy ingots

Abstract

The application provides a high-temperature superconducting strong magnetic field homogenization heat treatment method and device for a large-size rare earth magnesium alloy ingot, the large-size rare earth magnesium alloy ingot contains an LPSO phase, and the method comprises the following steps: placing a large-size rare earth magnesium alloy ingot with a diameter greater than 400 mm in a direct-current static magnetic field, rotating the ingot to cut the magnetic force lines in the direct-current static magnetic field, performing electromagnetic induction heating for 12 minutes, taking out the rare earth magnesium alloy ingot after the electromagnetic induction heating is completed, and cooling the rare earth magnesium alloy ingot to room temperature; wherein the direct-current static magnetic field is generated by a magnet made of high-temperature superconducting wire, and the strength of the direct-current static magnetic field is greater than or equal to 1T. The high-temperature superconducting strong magnetic field homogenization heat treatment method for the large-size rare earth magnesium alloy ingot provided by the application greatly improves the temperature uniformity in the large-size ingot, shortens the heating and holding time, thereby effectively improving the microstructure uniformity and performance consistency of the ingot and preventing coarse grain microstructures caused by long-time heating.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy material preparation technology, specifically to a high-temperature superconducting strong magnetic field homogenization heat treatment method and apparatus for large-size rare earth magnesium alloy ingots. Background Technology

[0002] Magnesium alloys are the lightest metallic structural materials in practical applications. Replacing aluminum alloys with magnesium alloys can achieve weight reductions of over 25% without altering the structural design, making them a significant potential lightweight application in aerospace and transportation. However, compared to aluminum alloys, traditional commercial magnesium alloys have lower mechanical properties, limiting their application scope and volume.

[0003] Rare earth elements possess unique 4f electron structures, extremely high chemical reactivity, and large atomic radii, leading to unique chemical and physical properties in rare earth alloys. Adding rare earth elements (such as Gd and Y) with significant solid solution strengthening and age-hardening effects to magnesium alloys can greatly improve alloy strength, but results in poor ductility. Introducing Zn into Mg-Gd-Y rare earth magnesium alloys forms a long-period packed-order structure (LPSO phase), which can significantly improve the material's ductility and machinability without significantly reducing alloy strength. Deformed rare earth magnesium alloys containing the LPSO phase exhibit excellent strength, toughness, and machinability.

[0004] Currently, conventional homogenization methods for magnesium alloys are not applicable to large-size rare-earth magnesium alloy ingots containing LPSO phase, which greatly limits the widespread application of high-performance wrought rare-earth magnesium alloys containing LPSO phase. The main challenges in the homogenization heat treatment process for conventional large-size wrought rare-earth magnesium alloy ingots containing LPSO phase are: 1) The addition of Zn leads to the preferential formation of more blocky LPSO phases at grain boundaries during casting, which significantly reduces the plasticity of the ingot; 2) Improper settings of parameters such as holding time and heating rate result in uneven heating of the ingot, preventing the effective and sufficient dissolution of the blocky LPSO phases at grain boundaries, thus affecting the overall performance of the material; 3) Slow heat transfer and uneven temperature in large-size ingots lead to uneven diffusion of high-content rare-earth elements and uneven dissolution and transformation of the second phase, reducing the performance uniformity and stability of large-size castings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature superconducting strong magnetic field homogenization heat treatment method and apparatus for large-size rare-earth magnesium alloy ingots. By employing low-frequency induction heating technology under a high-temperature superconducting strong magnetic field, low-frequency, high-penetration-depth electromagnetic induction heating is achieved, significantly improving temperature uniformity in large-size ingots and shortening heating and holding time. This effectively improves the microstructure uniformity and performance consistency of the ingots, prevents coarse grain structures caused by prolonged heating, solves the technical difficulties in the conventional homogenization process of large-size rare-earth magnesium alloy ingots, improves the forging machinability of the ingots, and provides a foundation for subsequent high-ratio plastic forming to obtain high-performance forgings.

[0006] The first aspect of the present invention provides a high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots, wherein the large-size rare earth magnesium alloy ingots contain LPSO phase, and includes the following steps: placing the large-size rare earth magnesium alloy ingots in a DC static magnetic field, rotating the large-size rare earth magnesium alloy ingots to cut the magnetic lines of force in the DC static magnetic field, electromagnetic induction heating for 12 minutes, and after the electromagnetic induction heating is completed, removing the rare earth magnesium alloy ingots and cooling them to room temperature.

[0007] The DC static magnetic field is generated by a magnet made of high-temperature superconducting wire, and the strength of the DC static magnetic field is greater than or equal to 1T.

[0008] In one embodiment, the rotational speed of the large-size rare earth magnesium alloy ingot is 100 revolutions per minute.

[0009] In one embodiment, the diameter of the large-size rare earth magnesium alloy ingot is Φ≥400mm.

[0010] In one embodiment, the large-size rare earth magnesium alloy ingot is composed of Gd: 8.0-12.0%, Y: 2.5-4.5%, Zn: 0.5-2.0%, Zr: 0.3-0.6%, with the remainder being Mg and unavoidable impurity elements, calculated by mass percentage.

[0011] In one embodiment, before placing the large-sized rare earth magnesium alloy ingot in a DC static magnetic field, the process includes melting and preparing the ingot: according to the set composition requirements of the rare earth magnesium alloy, pure metal and rare earth intermediate metal are added to the melting furnace, and the alloy components are melted into a metal melt before semi-continuous casting is carried out.

[0012] In one embodiment, pure metallic magnesium is added to the smelting furnace. After the resistance heating device is turned on and the magnesium melts, metallic zinc is added to the smelting furnace. The smelting furnace is heated to 740±5°C, and then magnesium-gadolinium master alloy and magnesium-yttrium master alloy are added to the smelting furnace. The furnace is heated to above 770°C, and then magnesium-zirconium master alloy is added. After the master alloy melts, the solution is stirred and slag is removed every 30 minutes. A refining agent is added during the last stirring. When the temperature of the smelting furnace is reduced to 700±5°C, the uniform molten metal in the furnace is semi-continuously cast to prepare large-size rare earth magnesium alloy ingots.

[0013] In one embodiment, during the preparation of large-size rare earth magnesium alloy ingots, the purity of metallic magnesium is 99.95%, the purity of metallic zinc is 99.99%, the mass percentage of gadolinium in the magnesium-gadolinium master alloy is 87.0%, the mass percentage of yttrium in the magnesium-yttrium master alloy is 30.0%, and the mass percentage of zirconium in the magnesium-zirconium master alloy is 30.0%.

[0014] A second aspect of the present invention provides a high-temperature superconducting strong magnetic field homogenization heat treatment apparatus for large-size rare-earth magnesium alloy ingots, used to realize the above-mentioned high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare-earth magnesium alloy ingots. The apparatus includes:

[0015] Support frame;

[0016] A rotating drive shaft is rotatably mounted on the support frame;

[0017] A rotary driven shaft is rotatably mounted on the support frame, and the central axis of the rotary driving shaft coincides with the central axis of the rotary driven shaft;

[0018] A billet rotating fixture, wherein two billet rotating fixtures are provided, and the two billet rotating fixtures are respectively mounted on the rotating drive shaft and the rotating driven shaft;

[0019] A large-size rare earth magnesium alloy ingot, wherein the two ends of the large-size rare earth magnesium alloy ingot in the axial direction are respectively clamped on the ingot rotation jig on the rotating drive shaft and on the ingot rotation jig on the rotating driven shaft;

[0020] A drive motor is connected to the rotating drive shaft, and the drive motor drives the rotating drive shaft to rotate.

[0021] A high-temperature superconducting magnet south pole, wherein one high-temperature superconducting magnet south pole is provided;

[0022] The high-temperature superconducting magnet has a north pole, and one high-temperature superconducting magnet north pole is provided. The high-temperature superconducting magnet north pole and the high-temperature superconducting magnet south pole are respectively located on both sides of the radial direction of the large-size rare earth magnesium alloy ingot.

[0023] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0024] 1. The addition of Zn to rare earth magnesium alloys leads to the preferential formation of more blocky LPSO phases at grain boundaries during the casting process. Improper settings of parameters such as holding time and heating rate result in uneven heating of the ingot, which prevents the blocky LPSO phases at grain boundaries from dissolving effectively and fully. Furthermore, the slow heat transfer and uneven temperature of large-sized ingots can lead to uneven diffusion of high-content rare earth elements and uneven dissolution and transformation of the second phase. These factors reduce the performance uniformity and stability of large-sized castings and affect the overall performance of the material. In the homogenization heat treatment method of the present invention, a strong magnetic field generated by a magnet wound with a high-temperature superconducting cable is used to perform low-frequency, high-penetration-depth electromagnetic induction heating. Specifically, firstly, the two ends of a cylindrical rare-earth magnesium alloy ingot are fixed on a rotating fixture, and then rotation is started and the speed is stabilized. Then, a DC static magnetic field of about 1T is generated between the magnets wound with the high-temperature superconducting cable. By cutting the magnetic lines of force through the low-frequency rotation of the ingot, the ingot is electromagnetically heated by induction. This can achieve low-frequency, high-penetration-depth electromagnetic induction heating, which can significantly improve the temperature uniformity in large-size ingots and shorten the heating and holding time. This effectively improves the uniformity of the ingot's structure and properties, prevents coarse grain structure caused by long-term heating, and obtains magnesium alloy ingots with uniform composition and excellent subsequent forging machinability.

[0025] 2. The homogenization heat treatment method provided by the present invention is applicable to large-size rare earth magnesium alloy ingots containing LPSO with a diameter Φ≥400mm. It preferably uses a high-temperature superconducting magnet to achieve a DC static magnetic field of more than 1T, so that the ingot is heated evenly and the microstructure and performance are not uniform due to temperature inhomogeneity. It is suitable for mass processing of large-size rare earth magnesium alloy ingots under industrial conditions. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0027] Figure 1 This is a schematic diagram of the high-temperature superconducting strong magnetic field homogenization heat treatment device for large-size rare earth magnesium alloy ingots in this invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1: Rotating drive shaft; 2: First billet rotating fixture; 3: High-temperature superconducting magnet south pole; 4: Cylindrical magnesium alloy billet; 5: Rotating driven shaft; 6: Second billet rotating fixture; 7: High-temperature superconducting magnet north pole. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] In this embodiment of the invention, all directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0033] The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots of the present invention is particularly suitable for rare earth magnesium alloy ingots with a diameter Φ≥400mm. Due to the addition of Zn in rare earth magnesium alloys, more blocky LPSO phases are preferentially formed at the grain boundaries during the casting process. However, improper setting of parameters such as holding time and heating rate can lead to uneven heating of the ingot, and the blocky LPSO phases at the grain boundaries cannot be effectively and fully dissolved. Furthermore, the slow heat transfer and uneven temperature of large-size ingots can result in uneven diffusion of high-content rare earth elements and uneven dissolution and transformation of the second phase.

[0034] The present invention will now be described with reference to specific embodiments and comparative examples.

[0035] Example 1

[0036] See Figure 1 This embodiment provides a high-temperature superconducting strong magnetic field homogenization heat treatment device for large-size rare earth magnesium alloy ingots, comprising:

[0037] Support frame;

[0038] Rotary drive shaft 1 is rotatably mounted on the support frame;

[0039] The driven shaft 5 is rotatably mounted on the support frame, and the central axis of the driving shaft 1 coincides with the central axis of the driven shaft 5.

[0040] The billet rotating fixture has two fixtures, namely the first billet rotating fixture 2 and the second billet rotating fixture 6. The first billet rotating fixture 2 and the second billet rotating fixture 6 are respectively mounted on the rotating drive shaft 1 and the rotating driven shaft 5. The first billet rotating fixture 2 and the second billet rotating fixture 6 have the same structure.

[0041] Large-size rare earth magnesium alloy ingot 4, which is a cylindrical structure, has its two ends clamped in the axial direction on the first ingot rotating fixture 2 and the second ingot rotating fixture 6, respectively.

[0042] The drive motor is connected to the rotating drive shaft and drives the rotating drive shaft to rotate.

[0043] High-temperature superconducting magnet south pole 3, one high-temperature superconducting magnet south pole is set up;

[0044] The high-temperature superconducting magnet has a north pole of 7. There is one high-temperature superconducting magnet north pole. The high-temperature superconducting magnet north pole and the high-temperature superconducting magnet south pole are respectively located on both sides of the radial direction of the large-size rare earth magnesium alloy ingot.

[0045] After the device in this embodiment is started, the drive motor is started, and a magnetic field is generated by forming a large current in the high-temperature superconducting wire. A DC static magnetic field is formed between the south pole 3 and the north pole 7 of the opposing high-temperature superconducting magnet, and most of the cylindrical magnesium alloy billet 4 is in the magnetic field.

[0046] The rotation of the drive shaft 1 by the drive motor drives the first billet rotation fixture 2 to realize the rotation of the cylindrical magnesium alloy billet 4. The second billet rotation fixture 6 and the driven shaft 5 are the driven ends, maintaining stable rotation.

[0047] A cylindrical, large-sized rare-earth magnesium alloy ingot is rotated and cut with magnetic lines of force to achieve induction heating.

[0048] Once heating is complete, turn off the current and stop the rotating motor, thus ending the heating process.

[0049] Example 2

[0050] This embodiment provides a high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare-earth magnesium alloy ingots, using the apparatus provided in Embodiment 1, and includes the following steps:

[0051] Step 1: Fix the two ends of the cylindrical rare earth magnesium alloy ingot with a diameter of 400mm in the axial direction onto two ingot rotating jigs, and then start rotating and stabilize the speed.

[0052] Step 2: Start the drive motor to generate a DC static magnetic field of about 1T between the magnets wound with high temperature superconducting cables. The magnetic lines of force are cut by the low-frequency rotation of the ingot and electromagnetic induction heating for 12 minutes.

[0053] Step 3: After heat treatment, remove the rare earth magnesium alloy ingot and cool it to room temperature by blowing air.

[0054] The high-temperature superconducting strong magnetic field homogenization heat treatment method in this embodiment is applicable to rare earth magnesium alloy ingots with the following composition: calculated by mass percentage, the composition of the rare earth magnesium alloy ingot is Gd: 8.0-12.0%, Y: 2.5-4.5%, Zn: 0.5-2.0%, Zr: 0.3-0.6%, with the remainder being Mg and unavoidable impurity elements.

[0055] Before step one, the process includes smelting and preparing ingots: Based on the specified composition requirements of the rare earth magnesium alloy, calculate the weights of the following metals: magnesium ingots with a purity of 99.95%, zinc ingots with a purity of 99.99%, a gadolinium master alloy with 87.0% gadolinium by mass, a yttrium master alloy with 30.0% yttrium by mass, and a zirconium master alloy with 30.0% zirconium by mass. Add the pure magnesium ingots to the smelting furnace, turn on the resistance heating device, and wait until the magnesium is completely melted before adding more metal to the furnace. After adding zinc ingots and heating the furnace to 740±5℃, magnesium-gadolinium master alloy and magnesium-yttrium master alloy are added. The furnace temperature is then raised to above 770℃ before adding magnesium-zirconium master alloy. Once the master alloys are completely melted, the solution is stirred and slag is removed every 30 minutes, for a total of three stirrings. A refining agent is added during the final stirring. The furnace temperature is then set to 700℃. When the furnace temperature drops to 700±5℃, the uniform molten metal is semi-continuously cast to produce large-size rare-earth magnesium alloy ingots. Using this casting method, large-size rare-earth magnesium alloy ingots will not crack.

[0056] Comparative Example 1

[0057] This comparative example provides a homogenization heat treatment method for large-size rare earth magnesium alloy ingots, including the following steps:

[0058] The heat treatment furnace is rapidly heated to 500-520℃ at a heating rate of 100℃ / h for preheating. Then, the semi-continuous casting ingot prepared in Example 2 is cooled to 200℃ by forced air cooling and quickly transferred to the preheated homogenization heat treatment furnace. Homogenization heat treatment is carried out at 520-525℃ and held for 10-12 hours. After being taken out, it is cooled to room temperature by forced air cooling.

[0059] The mechanical properties of the semi-continuous casting ingots prepared in Example 2, as well as the ingots after homogenization heat treatment in Example 2 and Comparative Example 1, were tested. The corresponding mechanical property data are shown in the table below:

[0060]

[0061] The mechanical property data above show that, compared with Comparative Example 1, Example 2 not only has significantly improved strength and plasticity, but also has small performance differences between the core and the edge of the ingot, and high performance consistency. This also shows that the heat treatment method of the present invention is suitable for large-sized magnesium alloy ingots and significantly eliminates the performance differences of large-sized magnesium alloy ingots.

[0062] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare-earth magnesium alloy ingots, wherein the large-size rare-earth magnesium alloy ingots contain an LPSO phase, characterized in that... The large-size rare earth magnesium alloy ingot is placed in a high-temperature superconducting strong magnetic field homogenization heat treatment device for high-temperature superconducting strong magnetic field homogenization heat treatment, including the following steps: placing the large-size rare earth magnesium alloy ingot in a DC static magnetic field, rotating the large-size rare earth magnesium alloy ingot to cut the magnetic lines of force in the DC static magnetic field, electromagnetic induction heating for 12 minutes, after the electromagnetic induction heating is completed, the rare earth magnesium alloy ingot is taken out and cooled to room temperature. The DC static magnetic field is generated by a magnet made of high-temperature superconducting wire, and the strength of the DC static magnetic field is greater than or equal to 1T. The high-temperature superconducting strong magnetic field homogenization heat treatment device for the large-size rare earth magnesium alloy ingot includes: Support frame; A rotating drive shaft is rotatably mounted on the support frame; A rotary driven shaft is rotatably mounted on the support frame, and the central axis of the rotary driving shaft coincides with the central axis of the rotary driven shaft; A billet rotating fixture, wherein two billet rotating fixtures are provided, and the two billet rotating fixtures are respectively mounted on the rotating drive shaft and the rotating driven shaft; A large-size rare earth magnesium alloy ingot, wherein the two ends of the large-size rare earth magnesium alloy ingot in the axial direction are respectively clamped on the ingot rotation jig on the rotating drive shaft and on the ingot rotation jig on the rotating driven shaft; A drive motor is connected to the rotating drive shaft, and the drive motor drives the rotating drive shaft to rotate. A high-temperature superconducting magnet south pole, wherein one high-temperature superconducting magnet south pole is provided; The high-temperature superconducting magnet has a north pole, and one high-temperature superconducting magnet north pole is provided. The high-temperature superconducting magnet north pole and the high-temperature superconducting magnet south pole are respectively located on both sides of the radial direction of the large-size rare earth magnesium alloy ingot.

2. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 1, characterized in that, The rotation speed of the large-size rare earth magnesium alloy ingot is 100 revolutions per minute.

3. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 1, characterized in that, Large-size rare earth magnesium alloy ingots have a diameter Φ≥400mm.

4. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 1, characterized in that, The composition of the large-size rare earth magnesium alloy ingot, calculated by mass percentage, is Gd: 8.0-12.0%, Y: 2.5-4.5%, Zn: 0.5-2.0%, Zr: 0.3-0.6%, with the remainder being Mg and unavoidable impurity elements.

5. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 4, characterized in that, Before placing large-sized rare earth magnesium alloy ingots in a DC static magnetic field, the process includes melting and preparing the ingots: according to the set composition requirements of rare earth magnesium alloys, pure metals and rare earth intermediate metals are added to the melting furnace, and the alloy components are melted into a molten metal before semi-continuous casting.

6. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 5, characterized in that, Pure magnesium is added to the smelting furnace. After the resistance heating device is turned on and the magnesium melts, zinc is added to the smelting furnace. The furnace temperature is raised to 740±5℃. Magnesium-gadolinium master alloy and magnesium-yttrium master alloy are then added to the smelting furnace. The furnace temperature is raised to above 770℃ before magnesium-zirconium master alloy is added. After the master alloy melts, the solution is stirred and slag is removed every 30 minutes. A refining agent is added during the last stirring. When the temperature of the smelting furnace is lowered to 700±5℃, the uniform molten metal in the furnace is semi-continuously cast to prepare large-size rare earth magnesium alloy ingots.

7. The high-temperature superconducting strong magnetic field homogenization heat treatment method for large-size rare earth magnesium alloy ingots according to claim 6, characterized in that, In the preparation of large-size rare earth magnesium alloy ingots, the purity of metallic magnesium is 99.95%, the purity of metallic zinc is 99.99%, the mass percentage of gadolinium in the magnesium-gadolinium master alloy is 87.0%, the mass percentage of yttrium in the magnesium-yttrium master alloy is 30.0%, and the mass percentage of zirconium in the magnesium-zirconium master alloy is 30.0%.

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