Vacuum induction melting furnace broken scale device and application thereof

Abstract

The present application relates to the field of vacuum induction melting furnace production, in particular to a kind of vacuum induction melting furnace broken scale device and its application, the broken scale device includes roll and roll rotation axis, the roll rotation axis is connected in roll, the roll rotation axis is connected in fixed platform by height adjusting mechanism, the height adjusting mechanism can be self-adapting height adjustment, to change the distance between the roll and cooling disc, the fixed platform is fixed on the induction melting furnace.The roll of the present application is in full contact with alloy scale, can reach the effect of fully broken scale, provides smaller size scale for subsequent powder making process, improves the hydrogen embrittlement treatment of powder making process and the hydrogen absorption effect of furnace charge.

Description

Technical Field

[0001] This invention relates to the field of auxiliary equipment for vacuum induction melting furnaces, specifically to a device for crushing scales in a vacuum induction melting furnace and its application. Background Technology

[0002] Neodymium iron boron rare earth permanent magnet materials have excellent magnetic properties and are widely used in medical magnetic resonance imaging, computer hard disk drives, audio equipment, mobile phones, home appliances, automobiles, wind power generation and other fields. With the rapid development of low-carbon and environmentally friendly economy and electronic technology, the demand for neodymium iron boron rare earth permanent magnet materials is increasing day by day.

[0003] The production process of neodymium iron boron rare earth permanent magnet materials includes smelting, ingot casting, powder making, and sintering. Smelting involves heating various metals to melt them into a molten liquid and homogenizing it to form an alloy liquid. Ingot casting involves pouring the molten alloy liquid into a certain shape and size to form an alloy ingot with a certain microstructure, namely alloy flakes. Powder making involves crushing the alloy flakes and processing them through air jet milling to form alloy powder. After pressing the alloy powder into a blank and sintering it, neodymium iron boron rare earth permanent magnet materials (also known as Nd-Fe-B permanent magnets) are obtained.

[0004] Extensive practical experience has demonstrated that the microstructure of the alloy ingot has a significant impact on the structure and properties of the final Nd-Fe-B permanent magnet. The presence of dendritic α-Fe and isolated blocky Nd-rich phases in the alloy ingot leads to variations in powder composition during the early, middle, and late stages of the air jet milling process, resulting in excessive residual powder, uneven powder particle size, and irregular powder shape. Consequently, only a portion of the liquid phase is sintered during the sintering process. Furthermore, the non-uniform distribution of isolated blocky Nd-rich phases along grain boundaries and the uneven grain size result in reduced magnetic properties and poor consistency in the Nd-Fe-B permanent magnet, leading to a low yield of the prepared Nd-Fe-B permanent magnets.

[0005] To address the aforementioned issues, vacuum induction melting furnaces are now widely used to produce alloy flakes, replacing alloy ingots prepared by melting and casting. The microstructure of the alloy flakes meets the following requirements: no α-Fe or blocky Nd-rich phases appear in the alloy flakes produced by vacuum induction melting furnaces, and the Nd-rich phases are distributed along Nd2Fe. 14 The plate-like grain boundaries of the B phase are uniformly distributed; there are no amorphous regions or ultrafine (<0.1μm) equiaxed grain regions; the interior of the alloy flakes in the vacuum induction melting furnace is columnar crystal, and it is a penetrating fine columnar crystal, which can effectively improve the yield of Nd-Fe-B permanent magnets.

[0006] In the vacuum induction melting furnace production process, to facilitate hydrogen embrittlement and fragmentation during powder production, the alloy flakes detached from the quench rolls need to be broken into smaller structures during melting, casting, and cooling. Currently, methods such as... Figure 1The diagram shows multiple plow-shaped devices used to crush alloy flakes. These devices move up and down at a fixed rate in conjunction with the rotation of a cooling disc to crush the alloy flakes. However, due to the small contact area between the crushing devices and the alloy flakes, and the relatively weak pressure exerted by the crushing devices, the crushing effect is poor. A large number of alloy flakes are difficult to crush to the standard size, resulting in problems such as low furnace loading, poor hydrogen absorption, and low pulverization efficiency in the hydrogen embrittlement crushing process during powder production. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a device for crushing alloy flakes in a vacuum induction melting furnace. By installing a grinding roller after the quenching roller in the melting furnace and using a cooling disc to drive the grinding roller to rotate, the grinding roller can fully contact the alloy flakes (hereinafter referred to as flakes) to achieve the effect of fully crushing the flakes. This provides smaller-sized flakes for subsequent powdering processes, thereby increasing the furnace loading and hydrogen absorption effect of the hydrogen embrittlement treatment in the powdering process.

[0008] The purpose of this invention is to provide a device for crushing scales in a vacuum induction melting furnace, comprising a grinding roller and a grinding roller shaft. The grinding roller shaft is connected to the grinding roller and is connected to a fixed platform via a height adjustment mechanism. The height adjustment mechanism can adaptively adjust the height to change the distance between the grinding roller and the cooling disc. The fixed platform is fixed on the induction melting furnace.

[0009] According to an embodiment of the present invention, the height adjustment mechanism includes a mounting vertical beam and a rotating shaft connecting arm. The top end of the mounting vertical beam is connected to a fixed platform, and the bottom end is movably connected to the rotating shaft connecting arm. The end of the rotating shaft connecting arm away from the mounting vertical beam is connected to the roller rotating shaft.

[0010] In use, the connection angle between the mounting beam and the rotating shaft connecting arm can change depending on the contact state between the roller and the cooling disc.

[0011] According to an embodiment of the present invention, the roller shaft is connected to the shaft connecting arm via a shaft clamp.

[0012] According to an embodiment of the present invention, the rotating shaft connecting arm and the rotating shaft clamp are connected by a fixing member. Preferably, the roller rotating shaft is clamped or sleeved with the rotating shaft clamp.

[0013] According to an embodiment of the present invention, a mounting slot is provided at the connection between the mounting vertical beam and the rotating shaft connecting arm. The top end of the rotating shaft connecting arm is embedded in the mounting slot, and a self-locking nut passes through the mounting slot to fix the rotating shaft connecting arm. The rotating shaft connecting arm can rotate around the self-locking nut as an axis to adaptively adjust the distance between the roller shaft and the fixed platform.

[0014] According to an embodiment of the present invention, the roller shaft is inserted into the roller, and both ends of the roller shaft protrude from the roller.

[0015] Preferably, the roller shaft is inserted into the lower part of the roller.

[0016] According to an embodiment of the present invention, the roller shaft is inserted into the roller at the transverse center of both ends of the roller and at one-quarter to one-half of the longitudinal length.

[0017] According to an embodiment of the present invention, the bottom of the grinding roller is in contact with the upper surface of the cooling disk of the vacuum induction melting furnace, and the grinding roller is provided with a plurality of crushing teeth, the crushing teeth including a toothed ring portion and a spacer ring portion, the spacer ring portion being disposed between adjacent toothed ring portions, and a plurality of crushing blades being disposed on the outer periphery of the toothed ring portion.

[0018] According to an embodiment of the present invention, the longitudinal section of the crushing blade is trapezoidal or triangular. When it is triangular, the end angle of the blade is 15 to 60°, preferably 20 to 50°, for example 30° or 45°.

[0019] According to an embodiment of the present invention, the length of the spacer ring is 3-5 cm, and preferably the toothed ring and the spacer ring are integrally formed.

[0020] Another object of the present invention is to provide a vacuum induction melting furnace with a scale crushing device, comprising a furnace body, a cooling disc and the aforementioned scale crushing device, wherein the crushing roller in the scale crushing device is located on top of the cooling disc, and the fixed platform is connected to the furnace body.

[0021] Preferably, the smelting furnace further includes multiple plow-shaped devices located above the cooling disc, and the multiple plow-shaped devices can move up and down relative to the cooling disc.

[0022] Another object of the present invention is to provide a method for preparing Nd-Fe-B permanent magnets in a vacuum induction melting furnace with a scale-breaking device, comprising the following steps:

[0023] S1. Add the raw materials to a vacuum induction melting furnace to melt and cast alloy flakes;

[0024] S2. Place the alloy flakes on the cooling disc;

[0025] S3. Use multiple plow-shaped devices and a scale-breaking device to break the alloy scales on the cooling disc to obtain fragments;

[0026] S4. The fragments are sequentially subjected to hydrogen crushing and air jet milling to obtain powder.

[0027] S5. The powder is shaped under an orientation magnetic field and then sintered to obtain an Nd-Fe-B permanent magnet.

[0028] Beneficial effects

[0029] The scale crushing device of this invention can change the connection angle between the vertical beam and the rotating shaft connecting arm according to the thickness of the scales, thereby changing the distance between the roller rotating shaft and the fixed crossbeam. This allows the roller to fully press against the scales on the surface of the cooling disc. During the casting and cooling process, the cooling disc carrying the scales rotates at a uniform speed, rotating relative to the roller. The roller contacts the scales on the cooling disc and presses the scales under gravity. At the same time, the roller rotating shaft is located at the lower part of the roller, increasing the downward force of the roller, thus fully crushing the scales. It can crush scales with a maximum single-sided size of about 35 mm to a maximum single-sided size of 10 mm, reaching the qualified standard size for hydrogen embrittlement treatment in the powder making process. In addition, compared with the prior art, where a large number of alloy scales are difficult to crush to the standard size, resulting in a low furnace charge and poor hydrogen absorption effect in the hydrogen embrittlement crushing treatment in powder making, this invention can increase the furnace charge by 17% and advance the violent hydrogen absorption reaction by about 25 minutes, resulting in a more complete hydrogen absorption effect. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of multiple plow-shaped devices;

[0031] Figure 2 A schematic diagram of the scale crushing device in the vacuum induction melting furnace in Embodiment 1 of the present invention;

[0032] Figure 3 for Figure 2 The left view.

[0033] In the attached diagram, the components represented by each number are as follows:

[0034] 1-Fixed crossbeam, 2-Installation vertical beam, 3-Self-locking nut, 4-Installation slot, 5-Spindle connecting arm, 6-Spindle clamp, 7-Clamp fixing nut, 8-Grinding roller, 9-Grinding roller shaft, 10-Cooling disc, 11-Furnace body. Detailed Implementation

[0035] The structure and application of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0036] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example 1

[0039] like Figure 2 and Figure 3 As shown, a device for crushing scales in a vacuum induction melting furnace includes a roller shaft 9, a roller 8 connected to the roller shaft 9, the roller 8 being placed on a cooling disc 10, the bottom of the roller 8 contacting the upper surface of the cooling disc 10, the end of the roller shaft 9 passing through the roller 8 and connected to a height adjustment mechanism, the top of the height adjustment mechanism being connected to a fixed crossbeam 1.

[0040] In this embodiment, the grinding roller 8 has a cylindrical structure and is provided with several crushing teeth. Each crushing tooth includes a toothed ring portion and a spacer ring portion. The spacer ring portion is disposed between adjacent toothed ring portions. Several crushing blades are disposed on the outer periphery of the toothed ring portion. The longitudinal section of the crushing blades is triangular, and the end angle of the blades is 15-60°, preferably 20-50°, such as 30° or 45°. The length of the spacer ring portion is 3-5cm. The toothed ring portion and the spacer ring portion are integrally formed. The grinding roller shaft 9 is inserted into the grinding roller 8, and both ends protrude from the grinding roller 8. In order to increase the downward pressure of the grinding roller 8, in this embodiment, the grinding roller shaft 9 is inserted into the lower part of the grinding roller 8. For example, the position where the grinding roller shaft 9 is inserted into the grinding roller 8 is located at the transverse center of both ends of the grinding roller 8 and at one-quarter to one-half of the longitudinal length.

[0041] A fixed crossbeam 1 is positioned above the roller 8. The fixed crossbeam 1 is connected to the end of the roller shaft 9 via a mounting vertical beam 2 and a rotating shaft connecting arm 5. The top end of the rotating shaft connecting arm 5 is connected to the bottom of the fixed crossbeam 1 via the mounting vertical beam 2. The bottom end of the rotating shaft connecting arm 5 is fixed to the end of the roller shaft 9 via a rotating shaft clamp 6. In this embodiment, both ends of the roller shaft 9 pass through the roller 8 and are connected to the rotating shaft clamp 6. The connection between the roller shaft 9 and the rotating shaft clamp 6 is, for example, a snap-fit ​​or a sleeve-fit.

[0042] See Figure 3 As shown, the rotating shaft connecting arm 5 is movably connected to the mounting vertical beam 2. For example, a mounting slot 4 is provided at the connection between the mounting vertical beam 2 and the rotating shaft connecting arm 5. The top of the rotating shaft connecting arm 5 is embedded in the mounting slot 4 of the mounting vertical beam 2. The self-locking nut 3 passes through the mounting slot 4 to connect the rotating shaft connecting arm 5 to the mounting vertical beam 2. The rotating shaft connecting arm 5 can rotate around the self-locking nut 3 as an axis. The fixed crossbeam 1 is connected to the furnace body 11, which stabilizes the entire device. In use, the rotating shaft connecting arm 5 is inserted into the mounting slot 4, and then the self-locking nut 3 is inserted to connect the rotating shaft connecting arm 5 to the mounting vertical beam 2.

[0043] See Figure 3 As shown, the shaft clamp 6 is sleeved on the end of the roller shaft 9 that extends out of the roller 8. The lower part of the shaft connecting arm 5 is connected to the shaft clamp 6 through the clamp fixing nut 7. The shape of the lower part of the shaft connecting arm 5 is adapted to the shaft clamp 6, for example, it is a semi-circular structure that can cover 1 / 2 of the shaft clamp 6.

[0044] Before the scale crushing device of the vacuum induction melting furnace of the present invention crushes the scales, the scale crushing device is first installed between the fixed crossbeam 1 and the cooling disc 10. The rotating shaft connecting arm 5 rotates according to the distance between the fixed crossbeam 1 and the cooling disc 10, adaptively adjusting the height of the scale crushing device so that the grinding roller 8 presses against the surface of the cooling disc 10. The quenching roller throws the cast alloy scales onto the cooling disc 10. When the cooling disc 10 rotates, the grinding roller 8 moves relative to the cooling disc 10 and crushes and crushes the alloy scales on the cooling disc 10. Furthermore, during the rolling process, when the thickness of the alloy flakes is uneven, the rotating shaft connecting arm 5 can rotate adaptively, allowing the rolling roller 8 to adjust up and down according to the thickness of the alloy flakes, thus avoiding rigid collision between the rolling roller 8 and the cooling disc 10. The surface of the rolling roller 8 is covered with multiple rings of shaped crushing teeth spaced 3-5cm apart, which increases the friction between the rolling roller 8 and the cooling disc 10, improves the degree of crushing of the metal flakes, and allows the rolling roller 8 to maintain a relatively uniform rotation speed, fully crushing the metal flakes to achieve the qualified standard size for hydrogen embrittlement. This solves the problem of small contact area between the plow-shaped crushing device and the alloy flakes, and insufficient downward pressing force, thereby improving the furnace loading capacity and hydrogen absorption effect of the hydrogen embrittlement treatment in the powder making process.

[0045] Example 2

[0046] A vacuum induction melting furnace, see Figure 2 As shown, it includes a furnace body 11, a cooling disc 10, a scale-crushing device as described in Example 1, and multiple plow-shaped devices (not shown in the figure). The crushing roller 8 in the scale-crushing device is located on top of the cooling disc 10, the fixed crossbeam 1 in the scale-crushing device is connected to the furnace body 11, and the multiple plow-shaped devices are located above the cooling disc 10 and can move up and down relative to the cooling disc 10.

[0047] Example 3

[0048] A method for preparing Nd-Fe-B permanent magnets using the vacuum induction melting furnace of Example 2 includes the following steps:

[0049] S1. The raw materials are added to a vacuum induction melting furnace to obtain alloy flakes.

[0050] S2. Place the alloy flakes on the cooling disc 10.

[0051] S3. Use multiple plow-shaped devices and a crushing scale device to crush the alloy scales on the cooling disc 10 to obtain fragments.

[0052] S4. The fragments are sequentially subjected to hydrogen crushing and air jet milling to obtain powder.

[0053] S5. The powder is shaped under an orientation magnetic field and then sintered to obtain an Nd-Fe-B permanent magnet.

[0054] The step S1 casting includes the following steps: heating and melting the raw material under vacuum to obtain an alloy liquid, pouring the alloy liquid through an intermediate ladle onto a water-cooled rotating roller, and cooling the alloy to form alloy flakes after being cooled by the rotating roller.

[0055] Comparative Example 1

[0056] In this comparative example, in addition to using, Figure 1 Apart from the multiple plow-shaped devices shown breaking the alloy scales, the other steps are the same as in Example 3.

[0057] The maximum size of the fragments after crushing the alloy flakes in Comparative Example 1 was 35 mm on one side; the maximum size of the fragments after crushing the alloy flakes in Example 3 was 10 mm on one side. Compared with Comparative Example 1, the furnace loading of Example 3 was increased by 25%, the hydrogen absorption reaction in step S3 was advanced by 30 minutes, the hydrogen absorption effect was more complete, and the powdering efficiency was significantly improved.

[0058] The specific embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above exemplary embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing Nd-Fe-B permanent magnets using a vacuum induction melting furnace equipped with a scale-breaking device, characterized in that: The vacuum induction melting furnace with a scale-crushing device includes a furnace body, a cooling disc, and a scale-crushing device. The flake crushing device includes a grinding roller and a grinding roller shaft. The grinding roller shaft is connected to the grinding roller and is connected to a fixed platform via a height adjustment mechanism. The height adjustment mechanism can adaptively adjust the height to change the distance between the grinding roller and the cooling disc. The grinding roller in the flake crushing device is located on top of the cooling disc, and the fixed platform is connected to the furnace body. The method includes the following steps: S1. Add the raw materials to a vacuum induction melting furnace and melt them to obtain alloy flakes; S2. Place the alloy flakes on the cooling disc; S3. Use multiple plow-shaped devices and a scale-breaking device to break the alloy scales on the cooling disc to obtain fragments; S4. The fragments are sequentially subjected to hydrogen crushing and air jet milling to obtain powder. S5. The powder is shaped under an orientation magnetic field and then sintered to obtain an Nd-Fe-B permanent magnet.

2. The method according to claim 1, characterized in that, The height adjustment mechanism includes a mounting beam and a rotating shaft connecting arm. The top end of the mounting beam is connected to a fixed platform, and the bottom end is rotatably connected to the rotating shaft connecting arm. The end of the rotating shaft connecting arm away from the mounting beam is connected to the roller rotating shaft.

3. The method according to claim 2, characterized in that, The roller shaft is connected to the shaft connecting arm via a shaft clamp.

4. The method according to claim 2, characterized in that, The rotating shaft connecting arm and the rotating shaft clamp are connected by a fixing component, and the roller rotating shaft is clamped or sleeved with the rotating shaft clamp.

5. The method according to claim 2, characterized in that, A mounting slot is provided at the connection between the mounting vertical beam and the rotating shaft connecting arm. The top of the rotating shaft connecting arm is embedded in the mounting slot. A self-locking nut passes through the mounting slot to fix the rotating shaft connecting arm. The rotating shaft connecting arm can rotate around the self-locking nut as an axis to adaptively adjust the distance between the roller shaft and the fixed platform.

6. The method according to any one of claims 1 to 5, characterized in that, The roller shaft is inserted into the roller, and both ends of the roller shaft protrude from the roller. The roller shaft is inserted into the lower part of the roller.

7. The method according to claim 6, characterized in that, The roller shaft is inserted into the roller at the transverse center of both ends of the roller, and at one-quarter to one-half of the longitudinal length.

8. The method according to any one of claims 1 to 5, characterized in that, The bottom of the roller is in contact with the upper surface of the cooling disc of the vacuum induction melting furnace. The roller is provided with a number of crushing teeth, each crushing tooth including a toothed ring portion and a spacer ring portion. The spacer ring portion is disposed between adjacent toothed ring portions, and a number of crushing blades are disposed on the outer periphery of the toothed ring portion.

9. The method according to claim 8, characterized in that, The longitudinal section of the crushing blade is trapezoidal or triangular. When it is triangular, the end angle of the blade is 15~60°.

10. The method according to any one of claims 1 to 5, characterized in that, The smelting furnace also includes multiple plow-shaped devices located above the cooling disc, and these devices can move up and down relative to the cooling disc.

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