JPH04291908A - Manufacturing method of rare earth permanent magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing rare earth permanent magnets, particularly a method for manufacturing rare earth permanent magnets having magnetic anisotropy by hot working, and in particular R (where R is at least one of the rare earth elements including Y). 1), Fe (iron), and B (boron).

0002

2. Description of the Related Art Conventionally, there have been mainly the following methods for manufacturing these rare earth-iron (transition metal) based high-performance permanent magnets.

(1) Sintering method (Japanese Unexamined Patent Publication No. 59-46008) (2) Rapid cooling method (Unexamined Japanese Patent Publication No. 59-211)
549) (3) Hot press (JP 60-100402 A) (4) Hot working method (JP 62-276803 A) (1), (2), and (3) production of permanent magnets The method requires turning the alloy into powder, but R-Fe-B
Since the alloy is highly active against oxygen, oxidation becomes even more intense when it is powdered, and the oxygen concentration in the sintered body inevitably increases. Also, when molding the powder, molding aids must be used, which remain in the form of carbon within the magnet body. Oxygen and carbon contained in this magnet significantly reduce the corrosion resistance and magnetic performance of the R-Fe-B magnet. Moreover, these manufacturing methods not only require complicated steps and expensive equipment, but also have poor production efficiency and increase the manufacturing cost of the magnet.

[0004] The method (4) for producing a permanent magnet has a simple manufacturing process, and since the magnet alloy is sealed in a capsule and subjected to hot working, the concentration of oxygen contained therein is low. Since it can be processed in the atmosphere, there is no need to control the atmosphere during processing, and the manufacturing cost is low. However, there is a problem in that the degree of freedom in shape is low and processing costs such as cutting and grinding become high depending on the shape of the magnet. Regarding this problem, JP-A-2-2
No. 52,219 discloses a method of punching a plate-shaped magnet material in a semi-molten state. This takes advantage of the property that the magnet material has an extremely brittle R2Fe14B intermetallic compound as its main phase, but also contains a grain boundary phase with a low melting point, and is in a semi-molten state at higher temperatures, making it susceptible to plastic deformation. It is something.

[0005]

[Problems to be Solved by the Invention] However, the above-mentioned press punching process has the problem that cracks tend to occur due to delicate conditions such as temperature, speed, and thickness of the plate material, resulting in a very low yield. The present invention solves the above-mentioned drawbacks of the conventional press working of permanent magnets, and its purpose is to provide a high-performance, low-cost permanent magnet.

[0006]

[Means for Solving the Problems] The method for producing a rare earth permanent magnet of the present invention uses R (R is at least one kind of rare earth elements including Y), Fe (iron), and B (boron) as basic constituents. When performing hot press punching of a plate-shaped rare earth permanent magnet material produced through a manufacturing process consisting of casting, hot working, and heat treatment, the plate material is fixed between the plate holder placed around the punch and the die. However, the punching process is performed with the part to be punched sandwiched between a bottom plate presser placed in the die and a punch, with the punch and die being heated in advance or constantly as the case requires.

[0007]

[Operation] That is, the present invention improves the yield, precision, and shear surface condition when stamping a plate-shaped magnetic alloy made by a method that does not include powder processes such as casting, hot working, and heat treatment. It is something to do.

[0008] The material is pressurized in the thickness direction between the plate holder and the die, and shear deformation is caused in the plate thickness direction while the material is pressurized between the inverse plate holder and the punch. At this time, the frictional force acting on the upper and lower pressure surfaces generates high hydrostatic pressure on the plate material, thereby preventing cracks from occurring and at the same time making it difficult for fractured surfaces to occur, improving processing accuracy.

[0009] Furthermore, by heating a mold such as a die or a punch, it is possible to prevent a drop in temperature or unevenness in the material due to contact between the material in a semi-molten state and the mold, thereby preventing the occurrence of cracks. can.

0010

[Examples] Examples of the present invention will be described below. FIG. 1 is a schematic diagram of the press punching die and permanent magnet material of the present invention. In the figure, 1 is a magnet sample, 2 is a punch, 3 is a plate holder, and 4
5 is a die, 5 is a bottom plate holder, and 6 is a plate holder and a spring attached to the bottom plate holder. (Example 1) First, using an induction heating furnace in an argon atmosphere, Pr17
Melting an alloy with a composition of Fe76.5B5Cu1.5,
Next, casting was performed to obtain a cast sample having a structure with an average grain size of columnar crystals of 15 μm and a length of 150 mm, a height of 140 mm, and a thickness of 20 mm. At this time, rare earth, iron, and copper raw materials with a purity of 99.9% were used, and boron was ferroboron.

Next, this cast sample length 145 mm×
It is cut and ground into a billet with a height of 38 mm and a thickness of 18 mm, placed in an SS41 sheath, and sealed by welding. This was heated in a furnace at 950° C. for 1 hour, and rolled for 6 passes at a reduction rate of 20%. After cooling, the sheath was removed and a sample of 20 mm x 20 mm x 2 mm was prepared by machining.

[0012] This plate-shaped sample was heated to 100% in an inert gas.
After heating in a 0℃ furnace for 3 to 5 minutes, press punching was performed using several molds as shown in Table 1, and a diameter of 16 mm was obtained.
It was formed into a disc-shaped magnet. The clearance between the punch and die was 0.2 mm, and the processing speed was 80 pieces/min. The table also shows the occurrence of cracks in the sample at that time. FIG. 1 is a schematic diagram of the mold.

[0013]

[Table 1]

When mold A without plate holder 3 and bottom plate holder 5 was used, the sample completely cracked. Mold B, C
When only one of the plate holder 3 and the bottom plate holder 5 was used as shown in the figure, cracks were completely eliminated and the number of cracks was considerably reduced, but cracks were still visible on the back of the sample. In the case of mold D using both the plate holder 3 and the bottom plate holder 5, there were almost no cracks, and the punched surface had good smoothness and dimensional accuracy.

(Example 2) Using the same rolled sample as in Example 1, the sample was heated to 1000°C using the mold shown in FIG.
Press punching was performed using a mold heated to the temperature shown in . The results for each mold temperature are shown in the same table. The higher the mold temperature, the fewer the number of cracks.

[0016]

[Table 2]

[0017]

[Effects of the Invention] As explained above, the method for producing a rare earth permanent magnet of the present invention has the following effects.

(1) By using a plate holder and a bottom plate holder, cracking of the magnet is prevented and dimensional accuracy is improved. (2) By heating the mold, the temperature of the magnet material is prevented from decreasing and the occurrence of cracks is suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a press die in Examples 1 and 2 of the present invention.

[Explanation of symbols]

1 Magnet sample 2 Punch 3. Board presser 4 Die 5 Bottom plate presser 6 Spring

Claims (2)

[Claims] [Claim 1] The basic constituents are R (R is at least one rare earth element including Y), Fe (iron), and B (boron), and is produced by a manufacturing process consisting of casting, hot working, and heat treatment. For rare earth permanent magnets, when hot press punching is performed on a plate-shaped permanent magnet material, the plate material is fixed with a plate holder, and the press punching is performed with the punched part sandwiched between the bottom plate holder and the punch. A method for producing a rare earth permanent magnet characterized by: 2. The method of manufacturing a rare earth permanent magnet according to claim 1, wherein the punch and die are heated in advance or constantly in the processing method.