A method for preparing samarium-iron alloy with reduced samarium volatilization

Abstract

The invention discloses a method for preparing a samarium-iron alloy with reduced samarium volatilization, and belongs to the technical field of alloy preparation. Excess samarium is added to the raw materials, and the high-melting-point raw materials and the low-melting-point raw materials are melted twice during the smelting process. The high-melting-point raw materials and a small amount of samarium are melted first, and a small amount of samarium and high-melting-point raw materials such as Fe are used to form an alloy with a lower melting point. The excess samarium and the low-melting-point raw materials are then added for a second time, and the alloy melt can be formed after rapid melting. When the molten alloy is cast onto a cooling roller, the rotation speed of the cooling roller is controlled to form Sm2Fe 17 Phase, and finally the cooled alloy sheet is homogenized to eliminate the impurity phase. The samarium-iron alloy prepared by the preparation method of the present invention can effectively reduce the volatilization of samarium and control the cost, and the content of the impurity α-Fe phase of the formed samarium-iron alloy is low.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy preparation, and in particular relates to a method for preparing a samarium-iron alloy capable of reducing the volatilization of samarium. Background Art

[0002] Sm 2 Fe 17 N x As a permanent magnetic material with good temperature stability and excellent magnetic properties, the potential application value of rare earth permanent magnets has gradually attracted people's attention. Smelting samarium iron alloy is the preparation of Sm 2 Fe 17 N x It is the first step in the development of rare earth permanent magnet materials. Therefore, the preparation of samarium-iron alloy is an important research direction.

[0003] Existing methods for preparing samarium-iron alloys mainly include reduction diffusion, mechanical alloying and induction melting, etc. These methods are usually carried out at high temperatures to ensure sufficient reaction between samarium and iron. The samarium in samarium-iron alloy is a rare earth element with unique chemical properties. The melting point of samarium is lower than that of iron, about 1072°C, and it is easy to volatilize during high-temperature smelting, which brings great challenges to the preparation of samarium-iron alloys.

[0004] Samarium, one of the raw materials for preparing samarium-iron alloy, is easily oxidized. 2 O 3 The melting point is very high, and it is extremely difficult to decompose during the smelting process. It will also introduce harmful element oxygen. In order to reduce the oxidation of samarium, researchers have proposed a method of adding a protective atmosphere during the smelting process to reduce the contact between samarium and air. At the same time, in order to reduce the impact of samarium volatilization on the alloy structure, excess samarium is compensated in the raw material ratio to make up for the loss of metallic samarium during the smelting process, ensuring that the final smelted alloy is a uniform phase composition of Sm 2 Fe 17 The existing compensation amount of alloy is mostly between 20-30%, which will greatly increase the cost of raw materials. Designing a suitable method to reduce the volatilization of samarium can reduce production costs while ensuring that the appearance of impurities is avoided. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a samarium-iron alloy with reduced samarium volatilization, so as to solve the problem of samarium volatilization in the preparation process of the samarium-iron alloy.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The present invention provides a method for preparing a samarium-iron alloy with reduced samarium volatilization, comprising the following steps:

[0008] Step 1, prepare raw materials according to the element ratio in the samarium-iron alloy chemical formula;

[0009] Step 2: Put the high melting point raw material and part of samarium into the crucible of the vacuum rapid solidification furnace, and preheat the crucible after evacuating the vacuum;

[0010] Step 3, heating the raw materials in the crucible under the protection of argon atmosphere until they melt into liquid state, adding the remaining samarium and low melting point raw materials into the crucible, and after all the raw materials in the crucible are melted, heating and cooling are performed for reaction, and after the reaction is completed, casting is prepared;

[0011] Step 4: The molten alloy is poured onto the cooling roller through the tundish and runner to form a continuous samarium-iron alloy sheet, which falls onto a water-cooled plate for cooling;

[0012] Step 5: After the alloy sheet is cooled to room temperature, it is placed in a vacuum heat treatment furnace and evacuated to 1×10 -2 Pa, heat to 1100℃ and keep warm for 5h, stop heating and cool to room temperature;

[0013] The chemical formula of the samarium-iron alloy is Sm 2 Fe 17 or Sm 2 Fe 17-x A x , wherein 0.01≤x≤2, and A includes at least one of Co, Al, Cu, Ga, Nd, Dy, and Nb.

[0014] Adding some samarium to the crucible is to accelerate the melting of iron. If there are only high-melting-point raw materials such as iron in the crucible, it will take a long time and very high temperature to melt it completely. Adding a small amount of samarium with a low melting point can form a low-melting-point alloy with iron after this part of the samarium melts, thereby accelerating the melting of iron. Moreover, the amount of samarium is small and the amount of volatility is also small.

[0015] Furthermore, the amount of metal samarium added is increased when preparing the raw materials, and the mass of metal samarium added per mole of samarium-iron alloy is 15.036 g to 30.072 g.

[0016] Furthermore, the high melting point raw material is at least one of Fe, Co, Dy and Nb; and the low melting point raw material is at least one of Sm, Al, Cu, Ga and Nd.

[0017] Furthermore, the mass of the partial samarium is 20wt% to 50wt% of the total amount of added samarium.

[0018] Furthermore, the pressure in the furnace after vacuuming in step 2 is below 0.1 Pa, the heating power for preheating the crucible is 15 kW, and the preheating time is 10 min.

[0019] Furthermore, the heating power of the heating under the protection of argon atmosphere is 35 kW.

[0020] Furthermore, the specific steps of the temperature raising and lowering heating reaction are as follows:

[0021] Set the heating power to 25 kW and maintain constant temperature for 3 minutes, then set the heating power to 40 kW, detect the temperature of the alloy melt in the crucible, and the reaction ends when the temperature reaches 1400°C to 1500°C.

[0022] Furthermore, the rotation speed of the cooling roller is 1 to 3 r / min.

[0023] When the liquid temperature is close, the faster the water-cooling roller rotates, the faster the alloy sheet cools in the high temperature section and the thinner the thickness. However, if the cooling speed is too fast, the alloy liquid will not have time to form Sm 2 Fe 17 The phase is cooled and becomes the α-Fe phase. When the water-cooling roller rotates slowly, the alloy sheet cools slowly in the high temperature section. The thicker the sheet is, the more time the alloy liquid has to form the Sm phase. 2 Fe 17 When the alloy sheet is thicker, the surface area is small, which reduces the volatilization of low-melting-point metals on the one hand and reduces surface oxidation on the other.

[0024] Furthermore, the cooling method of the water cooling plate includes water cooling and air cooling. The dual cooling method of water cooling and air cooling can cool the alloy sheet to room temperature as quickly as possible, reducing oxidation during the cooling process.

[0025] Beneficial effects of the present invention:

[0026] (1) The present invention proposes a method of secondary feeding in a rapid solidification furnace. After the high melting point raw material (such as iron) is completely melted, the low melting point raw material (such as samarium) is put into the crucible, the samarium is melted in the shortest time, and strip casting is performed to produce samarium-iron alloy. This method can not only effectively reduce the volatilization of samarium, but also improve production efficiency and reduce energy consumption.

[0027] (2) In the smelting process of the present invention, long-term refining is not required, and the low-melting-point raw materials evaporate less.

[0028] (3) In the process of rapid solidification and cooling, the water-cooling roller rotates slowly, which is beneficial to the alloy phase formation, and the alloy sheet is thicker, which reduces the volatilization area of ​​the low-melting-point raw materials on the one hand, and reduces surface oxidation on the other hand.

[0029] (4) The present invention places the alloy sheet after rapid solidification casting in a vacuum heat treatment furnace for homogenization treatment to eliminate impurities and form relatively pure Sm 2 Fe 17 Mutually. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Figure 1 It is a schematic diagram of the XRD test results of the alloy sheet of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] Step 1: Press Sm 2 Fe 17 Prepare the raw materials in a stoichiometric ratio. In addition, the samarium content in the raw materials is calculated based on the increase of 15.036g of metal samarium per mole of samarium iron alloy. The iron raw material is an iron rod with a purity of 99%, and the metal samarium is selected as samarium particles with a purity of 99.9%, with a particle size of 1 to 10 mm.

[0035] Step 2: Put 40wt% of the total amount of Fe and samarium in the weighed raw materials into the crucible of the vacuum quick-setting furnace, and evacuate the furnace. When the pressure in the furnace is below 0.1Pa, stop evacuating the furnace, set the heating power to 15kW, and preheat the crucible for 10min;

[0036] Step 3: Fill with argon gas for atmosphere protection, increase the heating power of the quick-setting furnace to 35kW, and after all the raw materials in the crucible are melted into liquid, put the remaining samarium into the crucible, and after the low-melting-point raw materials are completely melted, reduce the heating power to 25kW, and increase the heating power to 40kW after 3 minutes. Test the alloy melt in the crucible. When the temperature reaches 1400℃-1500℃, the reaction is over and ready for casting;

[0037] Step 4: The molten samarium iron alloy is poured onto the cooling roller through the tundish and runner to form a continuous samarium iron alloy sheet. The cooling roller speed is set at 2r / min, so that the alloy forms Sm 2 Fe 17 Phase, and falls onto the water cooling plate below;

[0038] Step 5: After the alloy sheet falls onto the water cooling plate, it is cooled by water cooling + air cooling to cool it to room temperature as quickly as possible;

[0039] Step 6: After the alloy sheet cools to room temperature, place it in a vacuum heat treatment furnace and evacuate it to 1×10 -2 Pa, heat to 1100℃ and keep warm for 5h, stop heating and cool to room temperature.

[0040] Take a few relatively flat alloy sheets, test their thickness at different locations, calculate the average value, and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1. The schematic diagram of the XRD test results of the alloy sheet of this embodiment is shown in Figure 1 .

[0041] Example 2

[0042] Compared with Example 1, in this embodiment, step 1 is carried out according to Sm 2 Fe 16.5 Co 0.5 The raw materials were prepared in a stoichiometric ratio. In addition, the samarium content in the raw materials was increased by 15.036 g of metal samarium per mole of samarium-iron alloy. The Co raw material was a cobalt metal block with a purity of 99%, and was placed in a crucible together with Fe. The other steps were the same as in Example 1.

[0043] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0044] Example 3

[0045] Compared with Example 1, in this embodiment, step 1 is carried out according to Sm 2 Fe 16.5 Al 0.5 The raw materials are prepared in a stoichiometric ratio. In addition, the samarium content in the raw materials is increased by 15.036 g of metal samarium per mole of samarium-iron alloy. The Al raw material is an aluminum metal block with a purity of 99%, and is placed in a crucible together with the remaining samarium. The other steps are the same as in Example 1.

[0046] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0047] Example 4

[0048] Compared with Example 1, the speed of the cooling roller in step 4 of this embodiment is set to 1 r / min, and the other steps are the same as Example 1.

[0049] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0050] Example 5

[0051] Compared with Example 1, in step 4 of this embodiment, the speed of the cooling roller is set to 3 r / min, and the other steps are the same as in Example 1.

[0052] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0053] Example 6

[0054] Compared with Example 1, in step 1 of this embodiment, the samarium content in the raw material is increased by calculating the amount of metallic samarium increased by 30.072 g per mole of samarium-iron alloy, and the other steps are the same as in Example 1.

[0055] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0056] Example 7

[0057] Compared with Example 1, in step 1 of this embodiment, the samarium content in the raw material is increased by calculating the amount of metallic samarium increased by 24.0576 g per mole of samarium-iron alloy, and the other steps are the same as in Example 1.

[0058] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0059] Example 8

[0060] Compared with Example 1, in step 2 of this embodiment, 20 wt% of metal samarium with a total addition amount of Fe and samarium is put into the crucible of the vacuum rapid solidification furnace, and the other steps are the same as in Example 1.

[0061] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0062] Example 9

[0063] Compared with Example 1, in step 2 of this embodiment, 50 wt% of the total amount of Fe and samarium added is put into the crucible of the vacuum rapid solidification furnace, and the other steps are the same as in Example 1.

[0064] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0065] Comparative Example 1

[0066] Compared with Example 1, in step 1 of this comparative example, Sm 2 Fe 17Prepare the raw materials in stoichiometric ratio, put samarium and Fe into the crucible together, without secondary addition, the specific steps are as follows:

[0067] Step 1: Press Sm 2 Fe 17 Prepare the raw materials in stoichiometric ratio. In addition, the samarium content in the raw materials is calculated by adding 15.036g of metal samarium per mole of samarium iron alloy. The iron raw material is an iron rod with a purity of 99%, and the metal samarium is selected as samarium particles with a purity of 99.9%, with a particle size of 1 to 10mm, and the excess samarium is 5wt%;

[0068] Step 2: Put the weighed Fe and samarium in the raw materials into the crucible of the vacuum quick-setting furnace and evacuate the furnace. When the pressure in the furnace is below 0.1 Pa, stop evacuating the furnace and set the heating power to 15 kW to preheat the crucible for 10 minutes.

[0069] Step 3: Fill with argon gas for atmosphere protection, increase the heating power of the quick-setting furnace to 35kW, and after all the raw materials in the crucible are melted into liquid, reduce the heating power to 25kW. After 3 minutes, increase the heating power to 40kW, test the temperature of the alloy melt in the crucible, and the reaction is completed when the temperature reaches 1400℃-1500℃, and prepare for casting;

[0070] Step 4: The molten samarium iron alloy is poured onto the cooling roller through the tundish and runner to form a continuous samarium iron alloy sheet. The cooling roller speed is set at 2r / min, so that the alloy forms Sm 2 Fe 17 Phase, and falls onto the water cooling plate below;

[0071] Step 5: After the alloy sheet falls onto the water cooling plate, it is cooled by water cooling + air cooling to cool it to room temperature as quickly as possible;

[0072] Step 6: After the alloy sheet cools to room temperature, place it in a vacuum heat treatment furnace and evacuate it to 1×10 -2 Pa, heat to 1100℃ and keep warm for 5h, stop heating and cool to room temperature.

[0073] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it; take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0074] Comparative Example 2

[0075] Compared with Example 1, the speed of the cooling roller in step 4 of this comparative example is set to 5 r / min, and the other steps are the same as Example 1.

[0076] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0077] Comparative Example 3

[0078] Compared with Example 1, the samarium content in the raw material of step 1 in this comparative example is not increased, and the other steps are the same as those in Example 1.

[0079] Take several relatively flat alloy sheets, test their thickness at different locations, calculate the average value and record it. Take another sample to test its Sm content and XRD phase analysis. The test results are shown in Table 1.

[0080] Table 1

[0081]

[0082] It can be seen from Table 1 that relatively pure Sm 2 Fe 17 Alloy sheet.

[0083] In Examples 1, 4, and 5, as the speed of the water-cooling roller decreases, thicker alloy sheets can be obtained, wherein the Sm content is higher and the α-Fe phase ratio is lower. In combination with Comparative Example 2, it can be seen that when the speed of the water-cooling roller is too fast, the alloy sheet is very thin, the cooling speed is too fast, the Sm content is low, and the α-Fe phase is too high.

[0084] In Examples 1, 6, 7 and Comparative Example 3, as the excess amount of samarium increases, the Sm content of the alloy sheet increases, the proportion of the α-Fe phase decreases, and a purer Sm2Fe17 phase can be obtained.

[0085] In Example 1 and Comparative Example 1, the comparison between the secondary charging and the simultaneous charging shows that, under the same raw material conditions, the secondary charging can reduce the volatilization of Sm, the α-Fe phase ratio of the alloy sheet is significantly lower, and the Sm content is greatly increased.

[0086] In Examples 1, 8, and 9, the more Sm is placed in the crucible, the more Sm volatilizes during the smelting process, and thus the Sm content in the alloy sheet is reduced.

[0087] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a samarium-iron alloy with reduced samarium volatilization, characterized in that: The steps include: Step 1, prepare raw materials according to the element ratio in the samarium-iron alloy chemical formula, increase the amount of metal samarium input when preparing the raw materials, and increase the mass of metal samarium in each mole of samarium-iron alloy by 15.036 g to 30.072 g; Step 2: Put the high melting point raw material and part of samarium into the crucible of the vacuum rapid solidification furnace, and preheat the crucible after evacuating the vacuum; Step 3, heating the raw materials in the crucible under the protection of argon atmosphere until they melt into liquid state, adding the remaining samarium and low melting point raw materials into the crucible, and after all the raw materials in the crucible are melted, heating and cooling are performed for reaction, and after the reaction is completed, casting is prepared; Step 4: The molten alloy is poured onto the cooling roller through the tundish and runner to form a continuous samarium-iron alloy sheet, which falls onto a water-cooled plate for cooling; Step 5: After the alloy sheet is cooled to room temperature, it is placed in a vacuum heat treatment furnace and evacuated to 1×10 -2 Pa, heat to 1100℃ and keep warm for 5h, stop heating and cool to room temperature; The chemical formula of the samarium iron alloy is Sm2Fe 17 or Sm2Fe 17-x A x , wherein 0.01≤x≤2, A includes at least one of Co, Al, Cu, Ga, Nd, Dy, and Nb; The rotation speed of the cooling roller is 1 to 3 r / min.

2. The method for preparing a samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The high melting point raw material is at least one of Fe, Co, Dy and Nb; the low melting point raw material is at least one of Sm, Al, Cu, Ga and Nd.

3. The method for preparing a samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The mass of the partial samarium is 20wt% to 50wt% of the total amount of added samarium.

4. The method for preparing a samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The pressure in the furnace after evacuation in the step 2 is below 0.1 Pa, the heating power for preheating the crucible is 15 kW, and the preheating time is 10 min.

5. The method for preparing a samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The heating power of the heating under the protection of argon atmosphere is 35 kW.

6. The method for preparing samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The specific steps of the temperature rise and fall heating reaction are as follows: The heating power was set to 25 kW for 3 min, and then the heating power was set to 40 kW. The temperature of the alloy melt in the crucible was detected. The reaction ended when the temperature reached 1400°C to 1500°C.

7. The method for preparing samarium-iron alloy with reduced samarium volatilization according to claim 1, characterized in that: The cooling method of the water cooling plate includes water cooling and air cooling.

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