Magnesium alloy semi-continuous casting hollow round ingot and crystallizer device for preparing round ingot thereof

Abstract

The application provides a magnesium alloy semi-continuous casting hollow round ingot and a crystallizer device for preparing the round ingot, and belongs to the field of magnesium alloy casting. The crystallizer device is added with a crystallizer inner core which is connected with a crystallizer outer ring through a bridge arm, so that the inside of the crystallizer presents a ring shape. The liquid guide pipe has a metal liquid outlet, and the metal liquid is uniformly injected into each crystallization area. A cooling water pipe is connected in the bridge arm, connected into the crystallizer inner core, and a ring-shaped cooling water nozzle is added at the lower end of the inner core. The application aims at the problems of high machining cost of magnesium alloy hollow round ingot and imperfect machining allowance utilization system, improves the structure of the crystallizer, the liquid guide pipe and the water cooling system of the semi-continuous casting equipment, adjusts the distribution of the substance field and the temperature field in the semi-continuous casting process, and realizes the preparation of high-quality hollow magnesium alloy semi-continuous casting ingot. The inner and outer rings of the ingot have fine grains and uniform structure, the machining amount of the magnesium alloy hollow round ingot preparation is reduced, the material utilization rate is improved, and the application prospect is wide.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy casting, and specifically relates to a magnesium alloy semi-continuous casting hollow round ingot and a crystallizer device for preparing the round ingot. Background Technology

[0002] Magnesium alloys, as the lightest structural metal materials, possess advantages such as high specific strength, high specific stiffness, excellent vibration damping and noise reduction performance, good electromagnetic shielding, and excellent machinability. They can replace traditional steel and aluminum alloys and have broad application prospects in aerospace, aviation, and automotive fields. Among them, seamless magnesium alloy tubes, due to their uniform mechanical properties and high production efficiency, can be used to manufacture weapon cylinders, underground pyrolysis tubes, and tubular components for rail transit equipment, etc., with broad market prospects and significant application value.

[0003] Currently, horizontal double-action forward extrusion presses are the mainstream method for mass production of seamless magnesium alloy tubes. Compared to vertical extrusion presses, this type of equipment can produce longer cylinder lengths and has a wider range of applications compared to reverse extrusion presses. It is the main equipment used by many large light alloy processing plants in China for the production of seamless tubes. Horizontal double-action forward extrusion presses require hollow round ingots as raw materials. Since there is currently no mature method for preparing hollow round ingots for magnesium alloys, solid round ingots need to be hollowed out for preparation, resulting in a significant waste of high-quality raw materials. Current preparation methods require excessive melting volumes, leading to uneven solute distribution, severe chemical element loss, coarse grains, and severe macroscopic segregation. Magnesium alloys have high viscosity and poor fluidity in the molten state, making it difficult to fill the mold under conventional casting processes, which easily leads to hot cracking and affects the yield of magnesium alloy round ingots. Furthermore, due to the slow cooling of the internal structure of large-sized solid ingots, the inner ring structure after processing into hollow ingots generally has coarse grains and large second-phase sizes, increasing the difficulty of stress field control during deformation processing and making it difficult to control the shape properties of the seamless tubes. Summary of the Invention

[0004] The purpose of this invention is to fill the gap in current mature methods for preparing hollow magnesium alloy ingots, providing a semi-continuous casting method for magnesium alloy hollow ingots and a crystallizer device for preparing the ingots. The crystallizer device includes an inner core, connected to the outer ring of the crystallizer via bridge arms, creating a ring-shaped interior. A liquid outlet is located at the lower end, allowing molten metal to be evenly injected into each crystallization region. A cooling water pipe is connected to the inner core of the crystallizer via the bridge arms, and an annular cooling water spray nozzle is added at the lower end of the inner core. This invention addresses the problems of high machining costs and an imperfect system for utilizing machining residues in magnesium alloy hollow ingots. By improving the structure of the crystallizer, liquid guide pipe, and water cooling system in the semi-continuous casting equipment, and adjusting the distribution of the material and temperature fields during the semi-continuous casting process, this invention achieves the preparation of high-quality hollow magnesium alloy ingots through semi-continuous casting. The ingot has fine grains and a uniform microstructure in both the inner and outer rings, reducing the machining workload in the preparation of hollow magnesium alloy ingots and improving material utilization, thus showing broad application prospects.

[0005] The technical solution provided by this invention is as follows:

[0006] <First Aspect>

[0007] A crystallizer apparatus for preparing semi-continuous casting hollow round ingots of magnesium alloy, the crystallizer apparatus comprising:

[0008] The crystallizer inner core is a hollow cylinder, and the crystallizer inner core is provided with an inner core water inlet and an inner core water outlet; the inner core water inlet channel and the inner core water outlet are connected.

[0009] The crystallizer inner core is coaxially sleeved with a crystallizer outer ring, and the crystallizer outer ring is provided with an outer ring water inlet and an outer ring water outlet.

[0010] A hollow bridge arm connects the inner core of the crystallizer and the outer ring of the crystallizer.

[0011] Two adjacent bridge arms, the outer ring of the crystallizer, and the inner core of the crystallizer together form a crystallization region. A liquid guide pipe is provided in the crystallization region, through which molten metal is injected. An outlet is provided at the lower end of the liquid guide pipe, so that the molten metal is evenly distributed into the crystallizer.

[0012] The inner core water inlet channel extends from the outer ring of the crystallizer through the cooling water pipe in the bridge arm to the inner core of the crystallizer.

[0013] The inner core water outlet is located at the bottom of the crystallizer inner core, and the inner core water outlet is distributed circumferentially along the bottom of the crystallizer inner core to form an annular cooling water spray nozzle.

[0014] A protective gas inlet is provided on the outer wall of the crystallizer's outer ring; the protective gas inlet is connected to the crystallization area through the outer ring of the crystallizer.

[0015] The core of the crystallizer is made of oxygen-free copper alloy.

[0016] <Second aspect>

[0017] This invention also provides a method for preparing a magnesium alloy semi-continuous casting hollow round ingot, comprising the following steps:

[0018] S1. Batching: Weigh the raw materials according to the composition of the magnesium alloy ingot;

[0019] S2. Melting: The weighed raw materials are put into the melting furnace for melting. After melting, the magnesium alloy melt is transferred to the refining furnace.

[0020] S3. Refining: Add magnesium alloy refining agent to the refining furnace, and after refining, transfer the magnesium alloy melt to the holding furnace;

[0021] S4. Preliminary Refinement and Heat Preservation: Add grain refiner to the heat preservation furnace and allow it to stand for heat preservation.

[0022] S5. Solidification: Transfer to the apparatus described above for preparing semi-continuous casting hollow round ingots of magnesium alloy for crystallization and solidification to obtain semi-continuous casting hollow round ingots of magnesium alloy.

[0023] In step S4, the heat preservation temperature is 720±30℃, and the temperature is left to stand for 5 to 30 minutes.

[0024] In step S5, the solidification temperature is 700±30℃, the billet pulling speed is 10~50mm / min, and the liquid level in the crystallizer is 30~150mm.

[0025] In one embodiment of the present invention, the inner diameter of the crystallizer is 100-800 mm and the outer diameter is 200-1000 mm.

[0026] Steps S2, S3, S4, and S5 are all performed under an inert gas atmosphere.

[0027] This invention also provides a method for preparing a magnesium alloy semi-continuous casting hollow round ingot; specifically including the following steps:

[0028] S1. Batching: Weigh the raw materials according to the composition of the magnesium alloy ingot;

[0029] S2. Melting: The weighed raw materials are put into the melting furnace for melting. After melting, the magnesium alloy melt is transferred to the refining furnace.

[0030] S3. Refining: Add magnesium alloy refining agent to the refining furnace, and after refining is completed, transfer the magnesium alloy melt to the holding furnace.

[0031] S4. Preliminary Refinement and Heat Preservation: Add grain refiner to the heat preservation furnace and allow it to stand for heat preservation.

[0032] S5. Solidification: Solidify in the crystallizer device provided above to finally obtain a semi-continuously cast magnesium alloy hollow round ingot.

[0033] Furthermore, in step S4, the heat preservation temperature is 720±30℃, and the temperature is left to stand for 5 to 30 minutes.

[0034] Furthermore, in step S5, the solidification temperature is 700±30℃, the drawing speed is 10~50mm / min, and the liquid level in the crystallizer is 30~150mm. The inner diameter of the crystallizer is 100~800mm, and the outer diameter is 200~1000mm.

[0035] Furthermore, steps S2 to S5 are all performed under an inert atmosphere.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention provides a crystallizer device for semi-continuous casting of magnesium alloy hollow round ingots. Based on the traditional semi-continuous casting equipment, a crystallizer core is added, which realizes the efficient and stable preparation of semi-continuous casting of magnesium alloy round ingots and promotes the lightweight process of aerospace and other industries.

[0038] (2) The present invention provides a device and preparation method for a magnesium alloy semi-continuous casting hollow round ingot, which reduces the amount of melting in the hollow ingot casting process, avoids problems such as uneven solute distribution and severe macroscopic segregation, and improves the product quality of magnesium alloy hollow ingot.

[0039] (3) The present invention provides a device and preparation method for a magnesium alloy semi-continuous casting hollow round ingot. In view of the problem of high viscosity and poor fluidity of magnesium alloy in molten state, the pouring method is improved on the basis of traditional semi-continuous casting equipment. Four liquid outlets are used for pouring, which reduces the tendency of hot cracking and improves the production qualification rate of magnesium alloy hollow round ingot.

[0040] (4) The present invention provides a device and preparation method for a magnesium alloy semi-continuous casting hollow round ingot, which improves the water cooling method, realizes that the inner ring structure of the hollow round ingot has small grain size and second phase size, and the inner and outer ring structures are consistent, which can realize the precise shape control of seamless tubes, improve the product preparation qualification rate, and effectively promote the lightweight process in aerospace, rail transportation and other fields. Attached Figure Description

[0041] 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:

[0042] Figure 1 This is a schematic diagram of the crystallizer device provided by the present invention;

[0043] Figure 2 This is an internal metallographic image of the semi-continuously cast high rare earth magnesium alloy ingot in Example 2;

[0044] Figure 3 This is an external metallographic image of the semi-continuously cast high rare earth magnesium alloy ingot in Example 2.

[0045] Explanation of reference numerals in the attached figures:

[0046] Crystallizer outer ring 1, outer ring water inlet 6

[0047] Liquid outlet 2, outer ring water outlet 7

[0048] Bridge arm 3, inner core outlet 8

[0049] Crystallizer inner core 4, protective gas inlet 9

[0050] Inner core water inlet 5. Detailed Implementation

[0051] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0052] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0053] Example 1

[0054] This embodiment provides a crystallizer apparatus for preparing semi-continuous casting hollow round ingots of magnesium alloy, such as... Figure 1 As shown, the crystallizer apparatus includes:

[0055] The crystallizer inner core 4 includes a hollow cylinder; the crystallizer inner core 4 is provided with an inner core water inlet channel 5 and an inner core water outlet 8, and the inner core water inlet channel 5 and the inner core water outlet 8 are connected.

[0056] The crystallizer inner core 4 is coaxially sleeved with a crystallizer outer ring 1, and the crystallizer outer ring 1 is provided with an outer ring water inlet 6 and an outer ring water outlet 7.

[0057] A hollow bridge arm 3 connects the inner core 4 of the crystallizer and the outer ring 1 of the crystallizer; in this embodiment, the bridge arm 3 is provided with four bridges.

[0058] The crystallization area is formed by any two adjacent bridge arms 3 along the circumference of the inner core 4 of the crystallizer, the outer ring 1 of the crystallizer, and the inner core 3 of the crystallizer. A liquid guide pipe is provided in the crystallization area, through which molten metal is injected into the crystallization area. The lower end of the liquid guide pipe is equipped with a liquid outlet 2, which allows the molten metal to flow evenly into the crystallizer. The liquid outlet 2 is located at a 45° position between the two bridge arms, and protective gas is introduced in real time during the semi-continuous casting process.

[0059] The inner core water inlet channel extends from the outer ring 1 of the crystallizer through the cooling water pipe in the bridge arm 3 to the inner core 4 of the crystallizer.

[0060] The inner core outlet 8 is located at the bottom of the inner core 4 of the crystallizer, and the inner core outlet 8 is distributed circumferentially along the bottom of the inner core 4 of the crystallizer, forming an annular spray nozzle.

[0061] A protective gas inlet 9 is provided on the outer wall of the outer ring 1 of the crystallizer; the protective gas inlet 9 is connected to the crystallization area through the outer ring 1 of the crystallizer.

[0062] The crystallizer core 4 is made of oxygen-free copper alloy and is connected to the crystallizer outer ring 1 through four bridge arms 4, making the inside of the crystallizer ring-shaped.

[0063] The outer ring cooling method is the same as that of a regular solid ingot crystallizer, and the inner and outer cooling water pipes are not connected.

[0064] Example 2

[0065] This embodiment provides a method for preparing a magnesium alloy semi-continuous casting hollow round ingot. The round ingot prepared by this method has an outer diameter of 450 mm, an inner diameter of 225 mm, and a billet weight of 800 kg. The components and their mass percentage content are as follows: Gd is 9%; Y is 3%; Zn is 2%; Zr is 0.5%; and the balance is Mg and unavoidable impurity elements (<1%).

[0066] The method for preparing the magnesium alloy semi-continuous casting hollow round ingot includes the following steps:

[0067] S1. Weigh the raw materials according to the composition of the magnesium alloy ingot, including 245kg pure Mg, 500kg Mg20Gd, 150kg Mg30Y, 80kg Mg-30Zr, and 25kg pure Zn;

[0068] S2. Add magnesium ingots to the smelting furnace, and add other raw materials (Mg20Gd, Mg30Y, pure Zn) at 720℃-760℃. Stir until completely melted. After smelting, transfer the magnesium melt to the refining furnace.

[0069] S3. Raise the melt temperature to 710℃, select JDMJ as the refining agent, refine for 5 minutes, skim off the surface slag after refining, and transfer the magnesium melt to the holding furnace after refining.

[0070] S4. Keep the furnace at a constant temperature and add Mg-30Zr master alloy. The holding temperature is 710℃. Let it stand for 15 minutes.

[0071] S5. The magnesium alloy melt is transferred into the crystallizer through the liquid guide tube of the preparation device for semi-continuous casting hollow round ingot of magnesium alloy in Example 1 for solidification. The solidification temperature is 680℃, the casting speed (pulling speed) is 30mm / min, and the liquid level height in the crystallizer is 100mm. Finally, a semi-continuous casting magnesium alloy ingot is obtained.

[0072] The magnesium alloy ingot has fine and uniform grains inside and out. The inner grain size of the round ingot is about 51 μm, and the average grain size of the outer grain size is about 55 μm.

[0073] Example 3

[0074] This embodiment provides a method for preparing a magnesium alloy semi-continuous casting hollow round ingot. The round ingot prepared by this method has an outer diameter of 500 mm, an inner diameter of 300 mm, and a billet weight of 800 kg. The components and their mass percentage content are as follows: Gd is 12%; Zn is 1%; Zr is 0.4%; and the balance is Mg and unavoidable impurity elements (<1%).

[0075] The method for preparing the magnesium alloy semi-continuous casting hollow round ingot includes the following steps:

[0076] S1. Weigh the raw materials according to the composition of the magnesium alloy ingot, including 258 kg of pure Mg, 650 kg of Mg20Gd, 80 kg of Mg-30Zr, and 12 kg of pure Zn;

[0077] S2. Add magnesium ingots to the smelting furnace, and add other raw materials (Mg20Gd, Mg30Y, pure Zn) at 720℃-760℃. Stir until completely melted. After smelting, transfer the magnesium melt to the refining furnace.

[0078] S3. Raise the melt temperature to 710℃, select JDMJ as the refining agent, refine for 5 minutes, skim off the surface slag after refining, and transfer the magnesium melt to the holding furnace after refining.

[0079] S4. Keep the furnace at a constant temperature and add Mg-30Zr master alloy. The holding temperature is 710℃. Let it stand for 15 minutes.

[0080] S5. The magnesium alloy melt is transferred into the crystallizer through the liquid guide tube of the preparation device for semi-continuous casting hollow round ingot of magnesium alloy in Example 1 for solidification. The solidification temperature is 680℃, the casting speed (pulling speed) is 30mm / min, and the liquid level height in the crystallizer is 100mm. Finally, a semi-continuous casting magnesium alloy ingot is obtained.

[0081] Testing revealed that the magnesium alloy ingot had fine and uniform grains both inside and out, with the inner grain size of the round ingot being approximately 59 μm. The microstructure was as follows: Figure 2 As shown, the average size of the outer grains is approximately 63 μm, and the microstructure is as follows: Figure 3 As shown.

[0082] Example 4

[0083] This embodiment provides a method for preparing a magnesium alloy semi-continuous casting hollow round ingot. The round ingot prepared by this method has an outer diameter of 800 mm, an inner diameter of 500 mm, and a billet weight of 800 kg. The components and their mass percentage content are as follows: Gd is 2%; Zr is 0.4%; and the balance is Mg and unavoidable impurity elements (<1%).

[0084] The method for preparing the magnesium alloy semi-continuous casting hollow round ingot includes the following steps:

[0085] S1. Weigh the raw materials according to the composition of the magnesium alloy ingot, including 795 kg of pure Mg, 125 kg of Mg20Gd, and 80 kg of Mg-30Zr;

[0086] S2. Add magnesium ingots to the smelting furnace and add (Mg20Gd) at 720℃-760℃. Stir until completely melted. After smelting, transfer the magnesium melt to the refining furnace.

[0087] S3. Raise the melt temperature to 710℃, select JDMJ as the refining agent, refine for 5 minutes, skim off the surface slag after refining, and transfer the magnesium melt to the holding furnace after refining.

[0088] S4. Keep the furnace at a constant temperature and add Mg-30Zr master alloy. The holding temperature is 710℃. Let it stand for 15 minutes.

[0089] S5. The magnesium alloy melt is transferred into the crystallizer through the liquid guide tube of the preparation device for semi-continuous casting hollow round ingot of magnesium alloy in Example 1 for solidification. The solidification temperature is 680℃, the casting speed (pulling speed) is 30mm / min, and the liquid level height in the crystallizer is 100mm. Finally, a semi-continuous casting magnesium alloy ingot is obtained.

[0090] Tests revealed that the magnesium alloy ingot has fine and uniform grains both inside and out. The inner grain size of the round ingot is approximately 63 μm, while the average grain size of the outer grain size is approximately 58 μm.

[0091] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0092] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A crystallizer apparatus for preparing semi-continuous casting hollow round ingots of magnesium alloy, characterized in that, The crystallizer apparatus includes: The crystallizer core (4) is a hollow cylinder. The crystallizer core (4) is provided with a core water inlet (5) and a core water outlet (8). The core water inlet channel and the core water outlet (8) are connected. The crystallizer inner core (4) is coaxially sleeved with a crystallizer outer ring (1), and the crystallizer outer ring (1) is provided with an outer ring water inlet (6) and an outer ring water outlet (7); A hollow bridge arm (3) connects the inner core (4) of the crystallizer and the outer ring (1) of the crystallizer; Two adjacent bridge arms (3), the outer ring (1) of the crystallizer, and the inner core (4) of the crystallizer together form a crystallization area. A liquid guide pipe is provided in the crystallization area, through which liquid metal is injected into the crystallization area. A liquid outlet (2) is provided at the lower end of the liquid guide pipe, so that the liquid metal is evenly distributed into the crystallizer. The inner core water inlet channel extends from the outer ring (1) of the crystallizer through the cooling water pipe in the bridge arm (3) to the inner core (4) of the crystallizer.

2. The crystallizer apparatus according to claim 1, characterized in that, The inner core outlet (8) is located at the bottom of the crystallizer inner core (4), and the inner core outlet (8) is distributed circumferentially along the bottom of the crystallizer inner core (4) to form an annular spray nozzle.

3. The crystallizer apparatus according to claim 1, characterized in that, A protective gas inlet (9) is provided on the outer wall of the outer ring (1) of the crystallizer; the protective gas inlet (9) is connected to the crystallization area through the outer ring (1) of the crystallizer.

4. The crystallizer apparatus according to claim 1, characterized in that, The crystallizer core (4) is made of oxygen-free copper alloy.

5. A method for preparing a magnesium alloy semi-continuous casting hollow round ingot, characterized in that, Includes the following steps: S1. Batching: Weigh the raw materials according to the composition of the magnesium alloy ingot; S2. Melting: The weighed raw materials are put into the melting furnace for melting. After melting, the magnesium alloy melt is transferred to the refining furnace. S3. Refining: Add magnesium alloy refining agent to the refining furnace, and after refining, transfer the magnesium alloy melt to the holding furnace; S4. Preliminary Refinement and Heat Preservation: Add grain refiner to the heat preservation furnace and allow it to stand for heat preservation. S5. Solidification: The semi-continuous casting hollow round ingot of magnesium alloy is prepared by crystallization and solidification in any one of the crystallizer devices according to claims 1-4 to obtain a semi-continuous casting hollow round ingot of magnesium alloy.

6. The preparation method according to claim 5, characterized in that, In step S4, the heat preservation temperature is 720±30℃, and the temperature is left to stand for 5 to 30 minutes.

7. The preparation method according to claim 5, characterized in that, In step S5, the solidification temperature is 700±30℃, the casting speed is 10~50mm / min, and the liquid level in the crystallizer is 30~150mm.

8. The preparation method according to claim 5, characterized in that, Steps S2, S3, S4, and S5 are all performed under an inert gas atmosphere.

9. A magnesium alloy semi-continuous casting hollow round ingot prepared by any one of claims 5-8.

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