CN109909465B - A method for inhibiting high temperature ordering of samarium cobalt alloys with high iron concentration - Google Patents

Abstract

The invention relates to a method for inhibiting high-temperature ordering of high-iron-concentration samarium cobalt alloy, which mainly comprises the following steps: the method comprises two steps of mother alloy preparation and mother alloy post-treatment, melt rapid quenching and high-temperature stabilization treatment are adopted, a 1:7H structure is obtained in a main phase of the high-iron-concentration samarium-cobalt mother alloy, and generation of a 2:17 ordered phase is successfully inhibited. The method can be applied to the preparation process of the high-iron-concentration samarium cobalt magnet, has low improvement consumption on the conventional process, and is beneficial to large-scale application.

Description

A method for inhibiting high temperature ordering of samarium cobalt alloys with high iron concentration

technical field

The invention relates to the technical field of preparation of rare earth permanent magnet materials, in particular to a preparation method of a high iron concentration 2:17 type samarium cobalt permanent magnet material.

Background technique

The 2:17 type samarium cobalt permanent magnet material has been widely used in equipment with complex thermal and magnetic environments such as electron traveling wave tubes, magnetic bearings, engines, generators and ion thrusters due to its excellent temperature characteristics. Research on 2:17 type samarium cobalt permanent magnet materials with high iron concentration has been covered in recent journal literature. Taking the magnet with the composition Sm(Co _1-uvw Fe _u Cu _v Zr _w ) _z as an example, it is generally believed that the iron concentration When it exceeds 25at% (or subscript u>0.32), the cellular organization of the magnet is damaged, and a complete cellular structure cannot be formed. The existing improvement methods are mainly: adjusting the process to suppress the precipitation of the second phase or adjusting the composition to obtain the optimal single phase components to prepare high iron concentration magnets. Taking the research results of Toshiba as an example, the process for preparing high iron concentration (Fe content subscript u=0.35 or atomic concentration ratio 31at%) samarium cobalt permanent magnet material is a traditional powder metallurgy process, in which the alloy is prepared by induction melting, the result It is shown that even with the precise control of the heat treatment process, it is still difficult to obtain a single-phase 1:7H structure in the main phase of the magnet, and there is always a 2:17R ordered phase, which affects the performance of the magnet. The Ningbo Institute of Advanced Materials, Chinese Academy of Sciences adjusted the magnet composition to suppress the existence of the 2:17R ordered phase at a lower Fe concentration (subscript u=0.28, atomic concentration ratio 25%), but it is not conducive to the promotion of magnets with higher Fe concentrations.

In the present invention, it is found through analysis that a 2:17R ordered phase already exists in the master alloy ingot with a high iron concentration. Obtained 2:17 type samarium cobalt permanent magnet rapid quenching sheet, successfully inhibited the generation of 2:17R ordered phase, and through subsequent high temperature stabilization treatment, the alloy was transformed into a single-phase 1:7H structure, which can be used for subsequent crushing and milling to prepare high Performance magnets.

SUMMARY OF THE INVENTION

Technical problem to be solved:

In view of the deficiencies in the prior art, the present invention provides a method for inhibiting the high-temperature phase ordering of a high-iron concentration 2:17 type samarium-cobalt magnet, thereby obtaining a high-temperature single-phase 1:7H structure. Specifically, it is to provide a post-processing process for an alloy ingot in a powder metallurgy process. The process includes making the alloy ingot solidify at an extremely fast cooling rate by a solution rapid quenching method to suppress the appearance of an ordered alloy in the alloy ingot. Subsequent high temperature stabilization treatment is performed to stabilize the metastable solidified phase to form a high temperature phase of 1:7H. The alloy treated by this method inhibits the generation of ordered 2:17 phase and can provide the required high-temperature 1:7H solid solution phase for magnet preparation.

A method for inhibiting high-temperature ordering of samarium-cobalt alloys with high iron concentration, the specific steps are as follows:

1) Preparation of master alloy

Mix Sm, Co, Cu, Fe and Zr according to the chemical formula ratio, and the chemical formula composition is expressed as Sm(Co _{1-uv- w} Fe _u Cu _v Zr _w ) _z , wherein u=0.32～0.40, v=0.05～0.08, w=0.01～0.03, z=7.4～8.0, then placed in the water-cooled copper crucible of the vacuum melting furnace, the easily burnt Sm was placed at the bottom of the crucible, evacuated to 2×10 ^-3 ～5×10 ^-3 Pa, Fill the furnace with high-purity argon gas, stop the gas after the vacuum degree in the furnace rises to 0.8×10 ⁵ Pa, repeat the smelting for 3 to 4 times under the conditions of working voltage 30V～45V, working current 600A～800A, and cooling to obtain alloy ingot.

In the preparation of the above Sm(Co _1-uvw Fe _u Cu _v Zr _w ) _z alloy, the actual amount of Sm content is 3% to 5% more than the theoretical addition amount.

The vacuum melting furnace is an electric arc melting furnace or an induction melting furnace.

2) Post-treatment of master alloy

Quick quenching of melt: put the alloy ingot into a quartz tube with a flat nozzle of 0.1-0.5mm, place it in the furnace body and connect it with the spray gun, vacuum it to 3×10 ^-3 Pa, and then fill it with high-purity argon gas When the pressure of the furnace body is -0.04Pa, after repeated pumping and washing three times, the spray gun is filled with 0.03Pa high-purity argon gas, and the high-purity argon gas in the furnace body is charged to the furnace body pressure of -0.04Pa, so that the gap between the spray gun and the furnace body is set to -0.04Pa. Keep the pressure difference of 0.07Pa, open the water-cooled copper wheel to keep the speed at 3～25m/s, and heat the alloy ingot to 1300～1500℃ by induction. After the alloy is completely melted and stabilized, quickly open the air valve of the spray gun to make the alloy The molten liquid is quickly sprayed onto the surface of the rolling copper wheel, and rapidly solidifies into a quick-setting sheet with a thickness of 0.1-0.3 mm.

High-temperature stabilization treatment: put the quick-setting sheet obtained in the above-mentioned melt quenching step in a high-vacuum furnace, the furnace body vacuum is 2×10 ^-3 ~ 5×10 ^-3 Pa, filled with argon, and then pumped to 2× 10 ^-3 to 5×10 ^-3 Pa, heated to a solution temperature T _st = 1120 to 1145° C., and quenched after solution for 2 to 8 hours to obtain a high iron concentration samarium cobalt alloy.

Further, during the rapid quenching of the melt in the step 2), the induction heating temperature of the alloy ingot is 1350-1400°C.

Further, when the melt is rapidly quenched in step 2), the speed of the water-cooled copper wheel is controlled at 3-10 m/s.

Further, during the high temperature stabilization treatment in the step 2), the solution treatment time is 4-6 hours.

Further, the main phase in the high iron concentration samarium cobalt alloy has a 1:7H structure, and the volume percentage of the ordered phase 2:17 phase content is 0-0.3%.

Further, the 1:7H twin width of the disordered main phase in the high iron concentration samarium cobalt alloy is 2.0-2.4 nm.

In the invention, a single-phase 1:7H phase structure can be obtained through the post-processing method of the master alloy, and the 2:17 phase existing in the high-temperature phase of the high-iron concentration samarium-cobalt magnet can be suppressed. This process has two advantages. One is that the main phase of samarium cobalt with high iron concentration can be prepared. The solid solubility of each alloy element in the main phase is the highest, and there is basically no precipitation; Suppress the ordering of atoms (especially Co-Co, Fe-Fe atom pairs) in the main phase 1:7H, inhibit the formation of the 2:17R phase, and avoid the incomplete cellular organization of the magnet. The invention needs to control the speed of the copper drum to obtain an extremely fast cooling speed. Too slow cooling speed will lead to insufficient cooling speed and cannot achieve the purpose of suppressing the formation of the 2:17R phase. The water-cooled copper drum speed of the invention is 3m/s～25m/s . At the same time, high temperature stabilization treatment is required in the process. The structure of the alloy after rapid melt quenching is actually an ordered phase of 2:17H. Although there is no ordered 2:17R phase, 2:17H is not the subsequent high-temperature solid solution 1:7H phase, so it is necessary to High-temperature solid solution 1:7H phase is obtained by high-temperature stabilization treatment, and there are differences in solidification morphology in different cooling parts of the ingot due to the difference in cooling rate. High-temperature stabilization treatment is also beneficial to homogenize the solidified structure, which is beneficial to the powder in the later magnet preparation process. Broken body.

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

The invention obtains the main phase of the high iron concentration single-phase 1:7H alloy through technical innovation, and suppresses the unnecessary 2:17 phase. The method can be applied to the preparation process of the high iron concentration samarium cobalt magnet, and the improvement of the conventional process is less expensive, which is favorable for large-scale application.

Description of drawings

FIG. 1 is an XRD pattern of the alloy of Example 1. FIG.

FIG. 2 is an XRD pattern of the alloy of Comparative Example 1. FIG.

FIG. 3 is the microstructure of the alloy of Example 1. FIG.

FIG. 4 is the microstructure of the alloy of Comparative Example 1. FIG.

FIG. 5 is an XRD pattern of the alloy of Comparative Example 2. FIG.

FIG. 6 is the TEM micro-domain morphology of the main phase of Example 1. FIG.

FIG. 7 is the TEM micro-domain morphology of the main phase of Comparative Example 2. FIG.

FIG. 8 is an XRD pattern of the alloy of Comparative Example 3. FIG.

Detailed ways

Example 1

1) Preparation of master alloy

Sm, Co, Cu, Fe and Zr were mixed according to the chemical formula ratio of Sm(Co _0.58 Fe _0.34 Cu _0.06 Zr _0.02 ) _7.8 , and then placed in a water-cooled copper crucible of a vacuum melting furnace. Vacuum to 2×10 ^-3 ～ 5×10 ^-3 Pa, fill the furnace with high-purity argon gas, and stop charging after the vacuum degree in the furnace rises to 0.8×10 ⁵ Pa. The working voltage is 30V～45V, and the working current is 600A Under the condition of ~800A, the smelting is repeated 3 to 4 times, and the alloy ingot is obtained by cooling.

2) Post-treatment of master alloy

Melt quick quenching: put the alloy ingot into a quartz tube with a 0.5mm wide spout, and place it in the furnace body to connect with the spray gun. The vacuum was pumped to 3×10 ^-3 Pa, and then filled with high-purity argon until the furnace pressure was -0.04Pa. After repeated pumping and washing three times, the spray gun was filled with 0.03Pa high-purity argon, and the furnace was filled with high-purity argon. The pressure into the furnace body is -0.04Pa, so that the pressure difference between the spray gun and the furnace body is maintained at 0.07Pa, the water-cooled copper wheel is turned on, and the speed is kept at 5m/s, and the alloy ingot is induction heated to 1400 ℃, until the alloy is completely After melting and stabilizing, quickly open the air valve of the spray gun, so that the alloy melt is quickly sprayed onto the surface of the rolling copper wheel, and quickly solidifies into a quick-setting sheet with a thickness of 0.1mm.

High temperature stabilization treatment: put the quick-setting sheet obtained in step 2) in a high vacuum furnace, the vacuum of the furnace body is 4 × 10 ^-3 Pa, filled with argon, and then pumped to 4 × 10 ^-3 Pa, and heated to solid solution Temperature T _st =1145 ℃, quenched after 6 hours of solid solution.

Comparative Example 1

Compared with Example 1, Comparative Example 1 only used step 1) to prepare the master alloy, and did not perform the master alloy post-treatment process of step 2).

Comparative Example 2

Compared with Example 1, Comparative Example 2 omits the solution rapid quenching step in the process step 2) post-treatment of the master alloy in Example 1, and the rest adopts the same composition and process as Example 1.

Comparative Example 3

Compared with Example 1, Comparative Example 3 omits the high temperature stabilization treatment step in the process step 2) master alloy post-treatment of Example 1, and the rest adopts the same composition and process as Example 1.

The comparison of the alloys obtained in Example 1 and Comparative Example 1, Comparative Example 2, and Comparative Example 3 can be described with reference to FIGS. 1 to 8 . It can be seen from Figure 1 and Figure 2 that the master alloy prepared by the process of Example 1 has no secondary phase 2:17R in the main phase (volume fraction 0), but if the alloy is not treated, as shown in Comparative Example 1, the master alloy There will be 8% (volume fraction) of the 2:17R ordered phase in the magnet. If the master alloy in Comparative Example 1 is used for subsequent magnet preparation, the ordered 2:17R phase will inevitably remain in the magnet, resulting in Degradation of magnet performance.

3 and 4, the main phase in the alloy treated in Example 1 is 1:7H phase, but the main phase in Comparative Example 1 is 2:17R, and the composition segregation is more serious. For magnet powder In terms of body fragmentation, such component segregation will affect the powder quality.

FIG. 5 is the XRD pattern analysis of the alloy in Comparative Example 2. It can be seen from the figure that about 20% of the 2:17R ordered phase exists in the alloy. It shows that the 1:7H phase can be obtained only by using the solution rapid quenching and high temperature stabilization treatment at the same time. For Comparative Example 2, due to the existence of the 2:17R phase in the master alloy, the diffusion of the 2:17R phase was intensified after the high temperature stabilization treatment, resulting in aggravated ordering. FIG. 6 is a high-resolution image of the 1:7H phase in Example 1. It can be seen that the twin width of the main phase 1:7H phase is 2.0 to 2.4 nm wide. 7 shows that the width of the main phase 1:7H twin in Comparative Example 2 reaches more than 10 nm, and the width of some regions reaches more than 20 nm, indicating that the degree of disorder of the main phase in Example 1 is higher than that in Comparative Example 2.

Figure 8 is the XRD pattern analysis of the alloy in Comparative Example 3. It can be seen from the figure that the 2:17R phase does not appear in the alloy without the high temperature stabilization treatment, but there is a part of the 2:17H phase with a content of 22% . It shows that the high temperature stabilization treatment can further transform the ordered 2:17H structure into the main phase 1:7H.

Example 2-4

The process steps of Examples 2-4 are the same as those of Example 1, but the components of the prepared magnets are different according to the u in the chemical formula Sm(Co _{1-uv- w} Fe _u Cu _v Zr _w ) _z , and the specific components are as shown in Table 1. Show.

Table 1

The above examples fully demonstrate that the process of the present invention can suppress the generation of the 2:17R ordered phase in the high iron concentration samarium cobalt alloy. According to the results in the literature, when the magnet has a 2:17R ordered phase, the magnet will form an incomplete cell-like structure after aging, and the coercivity will decrease rapidly. Using the process of the present invention to process the ingot, the generation of 2:17 has been suppressed, which shows the advantage of this process in the preparation of magnets with high Fe concentration.

Although exemplary embodiments of the present invention have been described for purposes of illustration, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Carry out various modifications, additions and substitutions, etc., and all these changes should belong to the protection scope of the appended claims of the present invention, and the various steps in the various departments and methods of the products claimed in the present invention can be combined arbitrarily. form together. Accordingly, the description of the embodiments disclosed in the present invention is not intended to limit the scope of the present invention, but to describe the present invention. Accordingly, the scope of the present invention is not limited by the above embodiments, but is defined by the claims or their equivalents.

Claims (6)

1. A method for inhibiting high-temperature ordering of high-iron-concentration samarium-cobalt alloy comprises the following specific steps:

1) preparation of master alloy

Mixing Sm, Co, Cu, Fe and Zr according to the formula proportion, and the chemical formula composition is represented as Sm (Co)_1-u-v-wFe_uCu_vZr_w)_zWherein u is 0.32-0.40, v is 0.05-0.08, w is 0.01-0.03, z is 7.4-8.0, then placing the crucible in a water-cooled copper crucible of a vacuum melting furnace, placing Sm easy to burn into the bottom of the crucible, and vacuumizing to 2 x 10^-3～5×10^-3Pa, filling high-purity argon into the furnace body, and increasing the vacuum degree in the furnace to 0.8 multiplied by 10⁵Stopping inflating after Pa, repeatedly smelting for 3-4 times under the conditions of working voltage of 30-45V and working current of 600-800A, and cooling to obtain an alloy ingot;

when the raw materials are mixed, the actual addition amount of Sm is 3-5% more than the theoretical addition amount;

the vacuum smelting furnace is an electric arc smelting furnace or an induction smelting furnace;

2) post-treatment of master alloy

Melt rapid quenching: putting the alloy cast ingot into a quartz tube with a flat nozzle with the seam width of 0.1-0.5 mmIs arranged in a furnace body and connected with a spray gun, and is vacuumized to 3 multiplied by 10^-3Pa, then filling high-purity argon until the pressure of the furnace body is-0.04 Pa, repeatedly pumping and washing for three times, filling high-purity argon of 0.03Pa into the spray gun, filling high-purity argon into the furnace body until the pressure of the furnace body is-0.04 Pa, keeping the pressure difference of 0.07Pa between the spray gun and the furnace body, opening the water-cooling copper wheel to keep the speed of the water-cooling copper wheel at 3-25 m/s, carrying out induction heating on the alloy cast ingot to 1300-1500 ℃, after the alloy is completely melted and stabilized, quickly opening an air valve of the spray gun to quickly spray the alloy melt onto the surface of the rolling copper wheel, and quickly solidifying the alloy melt into a quick-setting sheet with the thickness of 0.1-0.;

high-temperature stabilizing treatment: putting the rapid hardening sheet obtained in the melt rapid quenching step into a high vacuum furnace with the vacuum of the furnace body being 2 multiplied by 10^-3～5×10^-3Pa, filling argon, pumping to 2X 10^-3～5×10^-3Pa, heating to a solid solution temperature T_stAnd (3) quenching after solid solution at 1120-1145 ℃ for 2-8 h to obtain the high-iron-concentration samarium cobalt alloy.

2. The method of claim 1, wherein: and during melt rapid quenching in the step 2), the induction heating temperature of the alloy ingot is 1350-1400 ℃.

3. The method of claim 1, wherein: and in the step 2), during melt rapid quenching, the speed of the water-cooling copper wheel is controlled to be 3-10 m/s.

4. The method of claim 1, wherein: and in the step 2), during high-temperature stabilization treatment, the solution treatment time is 4-6 h.

5. The method of claim 1, wherein: the high-iron-concentration samarium cobalt alloy has a 1:7H structure as a main phase, and the volume percentage of 2:17 phases in an ordered phase is 0-0.3%.

6. The method of claim 1, wherein: the width of the disordered 1:7H twin crystal in the high-iron-concentration samarium cobalt alloy is 2.0-2.4 nm.

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