JPH04206805A - Manufacture of rare earth element-fe-b based magnet excellent in magnetic characteristics and corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method of a rare earth element-Fe-B based magnet satisfying magnetic characteristics and corrosion resistance, by a method wherein, after alloy powder composed of specified component composition is molded with pressure in a static magnetic field and turned into a magnetically anisotropic state, hot static water pressure treatment is performed in a vacuum or an inert gas atmosphere in a specified temperature range. CONSTITUTION:When the title rare earth element-Fe-B based magnet is manufactured, alloy powder composed of the following is molded with pressure; one or more kinds of rare earth elements selected out of Pr and Nd whose total amount is 29-34wt.%, B of 0.8-1.0wt.%, one or more kinds of elements selected out of a group composed of Ga, In and Sn whose total mount is 0.2-0.8wt.%, and Fe and inevitable impurities as the residual part. After the above molded body is turned into a magnetically anisotropic state, hot static water pressure treatment is performed in a vacuum or an inert gas atmosphere in the temperature range of 850-1100 deg.C. As the result, a high density rare earth element-Fe-B base magnet having composition composed of a first phase of rare earth element-Fe-B system and a low melting point phase of rare earth element-(one or more kinds selected out of Ga, In, and Sn) system wrapping the first phase is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses rare earth element -F which has excellent magnetic properties and corrosion resistance.
Regarding the method for producing an e-B magnet, in detail, it contains Pr and/or Nd as a rare earth element, and further contains Ga. In
, Sn, and has excellent magnetic properties and corrosion resistance.

[Prior Art] Rare earth magnets are attracting attention as the third type of permanent magnet after ferrite magnets and alnico magnets. This rare earth magnet is expected to exhibit excellent magnetic performance that can contribute to the miniaturization and higher precision of electrical products and precision equipment, and is making active progress in both physical property research and production. .

Among them, the ones that have been particularly promising in recent years are permanent magnets made of rare earth elements - transmuted elements - B systems such as Nd-Fe-B and Pr-Fe-B, and recently Cu and Ag have been used as the fourth constituent element. You can also add it as a
Adding additive elements is also being considered. The permanent magnet composition targeted by the present invention has (Pr, Nd) -Fe-B as a basic component, and 1 selected from Ga, In, and Sn.
(Pr, Nd)-Fe-B
ternary system 61 of the system (hereinafter abbreviated as R-Fe-B system magnet)
For convenience, I will discuss one stone as a representative example.

Known methods for manufacturing R-Fe-B magnets include sintering 0 alloy powder, and making quenched flakes into pound magnets using thermoplastic resin, etc. ,
No matter which method is used, the properties expected of the R-Fe-B 1i11 stone have not been fully exhibited.

By the way, R-Fe-B magnets are also known to have poor corrosion resistance, and this tendency is particularly noticeable in magnets to which Nd is added, and improving this corrosion resistance is also an important issue.

From the viewpoint of improving the corrosion resistance of R-Fe-B magnets, a technique such as that disclosed in JP-A No. 61-270308 has also been proposed. This technique performs shot blasting on the magnet surface to remove the surface layer, and then deposits an AI thin film on this surface by ion blasting. For example, Japanese Patent Application Laid-Open No. 120002/1983 discloses that a vapor phase plating layer is formed on the surface of the magnet material and
A method of improving corrosion resistance by forming a diffusion layer between a hard layer and the surface of a magnet material is disclosed.

In addition to the above, various surface treatment techniques have been proposed to improve corrosion resistance. Table 1 below summarizes the characteristics of various surface treatment techniques.

It is known that the pinholes and adhesion of the surface coating layer formed on the surface of R-Fe-B magnets are affected by various factors listed below (for example, Dempa Shimbun 197
Published on 9.10.5).

(1) Content of B ridge phase (2) Content of oxides (e.g. neodymium oxide and praseodymium oxide) (3) Voids present in the magnet material (4) Foreign matter mixed in by raw materials and processes , plating pretreatment, plating treatment, plating conditions, etc. are selected depending on the degree of each of the above factors (1) to (4).
Although some corrosion resistance effects have been obtained, none of these methods directly improves the above factors, and it largely depends on the chemical properties of the plating layer.

[Problems to be Solved by the Invention] The purpose of the present invention is to explore the requirements for improving magnetic properties and corrosion resistance, and to develop an R-
An object of the present invention is to provide a method for manufacturing Fe-B magnets.

[Means for Solving the Problem] The present invention that achieves the above object is based on rare earth element -Fe-
In manufacturing the B-based magnet, one or more rare earth elements selected from Pr and Nd: 29 to 34% by weight in total B: 0.8 to 1.0% by weight From the group consisting of Ga, In, and Sn 1 f selected
Elements higher than ffi: total amount 0,2~O,a weight% balance +
An alloy powder consisting of Fe and unavoidable impurities is press-molded in a static magnetic field to make the compact magnetically anisotropic, and then subjected to hot isostatic pressure in a temperature range of 850 to 1100°C in a vacuum or inert gas atmosphere. By processing, a structure consisting of a rare earth element-Fe-B system first phase and a rare earth element-(1 fffi or more selected from Ga, In, Sn) system low melting phase phase surrounding the first phase is formed. The purpose is to obtain a high-density rare earth element -Fe-B magnet with R-Fe-B, which has excellent magnetic properties and corrosion resistance.
This is a method for producing B-series 6 mushroom stones.

[Function] The present invention is configured as described above, but in short, an alloy powder having a predetermined composition is pressure-molded in a static magnetic field, the compact is made magnetically anisotropic, and then Hot isostatic pressure treatment (hereinafter referred to as HIP treatment) in a temperature range of 850 to 1100"C in a gas τ atmosphere produces a magnet material in which the above-mentioned voids are eliminated or reduced, and the magnetic properties of the magnet material are improved. and improved durability.

The magnet targeted by the present invention contains as an essential component one or more selected from the group consisting of Ga, In, and Sn, and these are extremely effective in improving magnetic properties. In other words, the addition of Ga, Sn, In, etc.
2Fez+B (atomic ratio, e.g. Pr2Fe+aB>
The first phase (hereinafter sometimes simply referred to as the first phase)
The R-ridge thin film phase or grain boundary phase is formed around the R-ridge, and as a result, during pressure molding, the crystal orientation of the first phase is very well aligned in the static magnetic field, and the magnetic flux density (Br) and coercive force (IH
It not only contributes to the improvement of c), but also contributes to corrosion resistance by reducing the number of pores.

The alloy composition constituting the R-Fe-B magnet of the present invention will be explained.

First, as rare earth elements, lanthanoid rare earth elements have been widely used so far, but in the present invention, Pr and/or Nd are used as particularly effective among these elements.

As mentioned above, rare earth elements include Pr and/or N.
d is used, but the composition range is 2, singly or in total.
It is necessary to set the content to 9 to 34% by weight, and if it is less than 29% by weight, a cubic crystal structure having the same structure as α iron results, resulting in a decrease in iHc, etc., and good magnetic properties cannot be obtained. On the other hand, if the upper limit exceeds 34% by weight, it will lead to excessive R-rich phase and insufficient volume fraction of the first phase, which will manifest as a decrease in magnetic flux density, making it impossible to exhibit good magnetic properties. .

B needs to be 0.8 to 1.0% by weight; if it is less than 0.8% by weight, the volume fraction of the first phase will be insufficient, leading to a decrease in magnetic flux density. On the other hand, regarding the upper limit, R, which does not have magnetic properties,
The content was limited to 1.0% by weight from the viewpoint of preventing a decrease in iH due to the appearance of the -Fe4-84 phase.

Elements such as Ga, Tn, and Sn need to be added to a total weight of 0.2 to 0.8%8, and less than 0.2% by weight (Ga, S
The R-rich phase containing n, In) decreases, and the crystal orientation of the first phase becomes insufficient. If it exceeds 0.8% by weight, the R-rich phase containing (Ga, Sn, In) will be excessive and the volume fraction of the first phase will be insufficient, leading to a decrease in magnetic flux density.

Incidentally, there have been reports of cases in which Ga was added to conventional powder sintered magnets.
(≧15 KOe was not obtained.Also, powder sintered magnets with Sn addition have been reported, or in this case, the addition was made to lower the sintering temperature, and Dy was added to reduce iHc to -F. Ga is added in a composite manner, and AI is also added to enhance the magnetic properties of the grain boundaries.
.

With the appropriate total addition amount of In, Sn, etc. of about 0.2 to 0.8% by weight, sufficient effects have not been obtained with conventional powder sintered materials.

On the other hand, in the magnet material of the present invention, by adding the manufacturing process described above and detailed later, it is possible to maximize the effect even with the above-mentioned amount of addition. In this way, Ga.

One of the features of the present invention is that the effects of addition of In, Sn, etc. are maximized.

In addition to the above-mentioned essential components, the magnet of the present invention basically consists of Fe and unavoidable impurities. Although Fe is an essential element for forming a magnetic phase, a portion (for example, about 20% by weight) of Fe may be replaced with a transition element such as Co or Mn.

Furthermore, in addition to the "double", about 2% by weight of A1, Si, etc. may be included, and it is good to try to improve the iH (iH) by adding a small amount that does not reduce the residual magnetic flux density.

The HIP treatment temperature when carrying out the present invention is 850 to 110
It is necessary to set the temperature to 0°C. If the HIP treatment temperature is less than 850°C, sufficient sintering will not be achieved, and if it exceeds 1100°C, coarsening and melting of crystal grains will occur, making it impossible to obtain good magnetic properties. In addition, the atmosphere for I(IP treatment) needs to be a vacuum or an insoluble gas atmosphere from the viewpoint of preventing oxidation of the powder during treatment.

The HIP treatment pressure is preferably 400 kgf-cm-2 or more. That is, Figure 1 is a graph showing the relationship between HIPIA burial conditions (temperature, pressure) and apparent density. I understand whether it is better to set it to 2 or more.

In the present invention, it is also effective to perform heat treatment at 400 to 600°C after HIPfi filling. That is, by this heat treatment, the structure is made finer, and the characteristics of the magnet can be further improved. Furthermore, in relation to the temperature conditions of the HIP treatment, by employing this heat treatment, even if the HIP treatment temperature is lowered and the magnetic properties are slightly inferior, it is possible to recover them.

[Example] Example: An alloy ingot having the composition shown in Table 2 was produced by arc melting, coarsely pulverized in a stamp mill, and then finely pulverized to 3 to 4 μm in a jet mill.

Table 2 After filling the obtained fine powder into a metal capsule, it was pressure-molded at 5 tons/am' while anisotropic in a magnetic field.
After degassing at °C, the container was sealed. Then, in an Ar gas atmosphere,
After raising the temperature to 00°C, the pressure was gradually increased and held for 30 minutes, and the pressure was further increased to 11,000 at and the temperature was raised to 1,050°C, and HIP treatment was performed for 1 hour under these conditions. After cooling to room temperature,
A heat treatment was performed at 80° C. for 2 hours to produce a magnet material of the present invention.

When we investigated the magnetic properties of the obtained magnet material, we found that the following
The results shown in the table were obtained.

Table 3 As is clear from the results, it can be seen that the magnet material obtained by the present invention exhibits excellent magnetic properties. This is thought to be due to the HIP treatment achieving higher density of the magnetic material. Incidentally, when the density of the obtained magnetic material was measured, it was 7.68 g/cc, which was a value corresponding to approximately 100% of the apparent density. After ion blating the 10 μm AI film, the corrosion resistance of the magnet material was investigated by a salt water spray test, and it was confirmed that it had excellent corrosion resistance.

Comparative Example 1 An alloy ingot having the composition shown in Table 4 was produced by arc melting and treated in the same manner as in Example 1 to obtain a fine powder of 3 to 4 μm.

Table 4 The obtained fine powder was made anisotropic in a magnetic field and was heated to 5 tons/c.
After being press-formed by m2, it was sintered at 1080° C. for 6 hours, cooled to room temperature, and then heat-treated at 480″C for 2 hours to produce 6!1 stone.

When we investigated the magnetic properties of the obtained magnet material, we found that the following
The results shown in the table were obtained.

Table 5 It is clear from a comparison of Table 5 and Table 3 above that the magnetic properties of the magnet materials obtained by the powder sintering method are inferior to those obtained by the method of the present invention. I understand very well. This is thought to be because it is difficult to achieve high density of the magnet material using the powder sintering method, and this appears as a decrease in the 1i11 characteristics. Incidentally, when the density of the obtained magnetic material was measured, it was 7.34z/cc, which was a value corresponding to approximately 96% of the apparent density. When the corrosion resistance was investigated in the same manner as in Example 1, it was found that the corrosion resistance was not as excellent as that obtained in Example 1.

Example 2 An alloy ingot having each composition shown in Table 6 below was produced by arc melting, and a fine powder was obtained from it in the same manner as in Example 1.
Using this fine powder, a magnet material was manufactured according to Example 1,
The magnetic properties of the obtained magnet material were investigated. The result is the 6th
It can be seen from the table that the magnetic properties of magnet materials (examples) to which Ga, In, Sn, etc. are added are better than those of magnet materials containing Cu. This is as described above.

This is believed to be because the addition of In, Sn, etc. significantly lowers the melting point of the second phase of the magnet material composition, and this is because it surrounds the first phase thinly and uniformly.

[Effect of the invention] The present invention is configured as described above, and includes Ga.

By performing HIP treatment using rare earth-Fe-B alloy powder containing Tn, Sn, etc. as essential components, high density can be achieved and rare earth-Fe-B magnets with excellent magnetic properties and corrosion resistance can be obtained. It was done.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between HIP processing conditions (temperature, pressure) and apparent density.

Claims (1)

[Claims] In producing a rare earth element-Fe-B magnet, one or more rare earth elements selected from Pr and Nd: 29 to 34% by weight in total B: 0.8 to 1.0% by weight One or more elements selected from the group consisting of Ga, In, and Sn: 0.2 to 0.8% by weight in total The balance: An alloy powder consisting of Fe and unavoidable impurities is press-molded in a static magnetic field. After making the molded body magnetically anisotropic, it is subjected to hot isostatic pressure treatment in a temperature range of 850 to 1100°C in vacuum or an inert gas atmosphere, thereby forming the first phase of the rare earth element-Fe-B system and the first phase of the rare earth element-Fe-B system. To obtain a high-density rare earth element-Fe-B magnet having a structure consisting of a low melting point phase of a rare earth element (one or more selected from the group consisting of Ga, In, and Sn) surrounding one phase. A method for producing a rare earth element-Fe-B magnet characterized by excellent magnetic properties and corrosion resistance.