JPH01318217A - Manufacture of permanent magnet for magnetron - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics and mechanical strength by using a hot processing and heat treatment together with melting and casting R-TM-B alloy being employed as a basic process. CONSTITUTION:After melting and casting an alloy which basically consists of a rare-earth element including Y, a transition metal and boron, a template ingot is subject to hot processing at 500 deg.C or more. Namely, an alloy of Pr17Fe76 Cu3B4 is melted as a composition of magnet, casted into a template made by using a soft magnetic material template 2, a cover is welded at the upper part after cooling, is heated to 950 deg.C, and hot-processing and hot-drawing machining is performed. Then, heat processing is performed to obtain an attached body of a permanent magnet 1 and the soft magnetic material template. After cutting the obtained attached body into a desired shape, a yoke 3 is sealed. Thus, a compact magnetron with a magnetic characteristics of approximately 7 times larger than that of ferrite magnet can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a permanent magnet for a magnetron used in a magnetron such as a microwave oven in industrial equipment and the like.

[Prior Art] Conventionally, magnetrons have used ferrite, alnico, rare earth sintered magnets, and the like.

[Problems to be Solved by the Invention] However, conventional permanent magnets for magnetrons have had the following problems.

When using ferrite magnets, their magnetic properties are far inferior to those of rare earth magnets, so in order to compensate for this, it was necessary to construct a large number of magnets and a large magnetic circuit to focus the magnetic flux.

When alnico magnets are used, there is a problem in that the magnets have extremely small coercive force, which requires magnetization after the magnetic circuit is installed.

When a rare earth sintered magnet is used, although the magnetic properties are sufficiently satisfactory, there is a problem that the raw material cost and manufacturing cost are large, making the magnet very expensive.

In addition, when manufacturing rare earth iron boron based sintered magnets with low raw material costs by the sintering method, a process of turning the alloy into powder is essential, but R-T M-B alloys are extremely sensitive to oxygen. It is active, so when it goes through the process of powdering, the surface area increases, oxidation becomes intense, and the oxygen temperature in the sintered body inevitably increases.Also, when molding the powder, it is difficult to use materials such as zinc stearate. A molding aid must be used, and although it is removed before the sintering process, it remains in the magnet in the form of carbon for several moments, impairing the magnetic performance of the R-T M-B magnet. There is a problem of lowering the value.

The molded body after press molding with the addition of a molding aid is called a green body. This is very fragile and difficult to handle, and therefore, it is a major drawback that it takes considerable effort to neatly arrange them in the sintering furnace.

Furthermore, in order to obtain an anisotropic magnet, press molding must be performed in a magnetic field, which requires large equipment such as a magnetic field power source and a coil.

Because of the above drawbacks, generally speaking, R-TM-B
Manufacturing sintered magnets of the R-TM-B type not only requires expensive equipment, but also reduces production efficiency and increases the manufacturing cost of the magnets.
It was not possible to take advantage of the advantages of the system magnet.

Furthermore, all conventional magnets were manufactured as a single magnet and then fixed to yokes, structural members, etc. by means of adhesives, etc.; There was also the serious problem of the magnet coming off.

Therefore, the present invention is intended to solve such problems, and its purpose is to melt and cast R-TM-B alloy as a basic process, and to use hot working and heat treatment in combination to improve magnetic properties. The purpose of the present invention is to provide a permanent magnet for a magnetron that has excellent properties, high mechanical strength, and low cost.

[Means for Solving the Problems] In order to solve the above problems, the method for manufacturing a permanent magnet for a magnetron of the present invention includes R (where R is at least one rare earth element including Y), a transition metal, and boron. The method is characterized in that after melting and casting an alloy whose basic components are, the cast ingot is hot worked at a temperature of 500° C. or higher.

In addition, the magnetic alloy is melted and cast, the cast ingot is then covered with a soft magnetic material, hot worked at a temperature of 500°C or higher, and then heat treated at a temperature of 250°C or higher to form a joined body of the permanent magnet and the soft magnetic material. It is characterized in that it is manufactured and then subjected to post-processing such as cutting so that a part of the soft magnetic material portion of the joined body remains as a structural member or a magnetic circuit.

Alternatively, a process of melting the magnet alloy and casting it into a mold made of a soft magnetic material or a material used to bond with the magnet, hot working the cast ingot together with the mold at a temperature of 500°C or higher, and then heating it at a temperature of 250°C or higher. Heat treatment is performed to produce a joined body of the permanent magnet and the mold material, and further, one part of the mold material part of the joined body is
It is characterized by post-processing such as cutting so that the portion remains as a structural member or magnetic circuit.

A longitudinal cross-sectional view of a magnetic circuit using magnets, 1 is a rare earth,
A patented magnet featuring a transition metal and boron, 2 a soft magnetic mold, and 3 a yoke.

Table 1 shows the composition of the magnet alloy of this example.

Table 1 However, the composition of the magnet is not limited to the composition shown in Table 1, and the rare earth metals include Y, La, Ce, Pr, and N.
d%Sm, Eu%Gd, Tb%Dy.

HOlEr, Tm, Yb, Lu are listed as candidates,
One or a combination of two or more of these may be used. The highest magnetic properties are obtained with Pr. Practically, therefore, Pr, Pr-Nd, Ce-Pr-Nd alloys, etc. are used.

Candidates for the transition metal include Fe, Co, NiS Cu, etc., and one or more of these may be used in combination. In addition, small amounts of additive elements such as heavy rare earths Dy, 'rb, etc., A1, Si,
Mo, Ga, etc. are effective in improving coercive force.

The main phase of R-T M-B permanent magnet is R2T M + a
This is the B compound phase. Therefore, if R is less than 8 at%, the above compounds will not be formed and high magnetic performance will not be obtained.On the other hand, if R is more than 30 at%, the non-magnetic R-rich phase will increase and the magnetic properties will deteriorate. Significantly decreased.

Therefore, the appropriate range for R is 8 to 30 atomic %.

However, in order to form a cast magnet, it is preferably 8 to 25 atomic %.

B is an essential element for forming the R2TM Ia B compound phase, and if it is less than 2 atom%, it becomes a rhombohedral R-TM system, so a high coercive force cannot be expected, and if it exceeds 28 atom%, B The amount of non-magnetic phase containing increases, and the residual magnetic flux density decreases significantly. However, for cast magnets, B is preferably 8 atomic % or less; if it exceeds this, a fine R2TM14B compound phase cannot be obtained unless special cooling is performed, and an appropriate coercive force cannot be obtained.

A1, Ga, etc. exhibit the effect of increasing coercive force. However, since A1 and Ga are non-magnetic elements, increasing the amount added lowers the residual magnetic flux density. If it exceeds 6 atomic %, the residual magnetic flux density will be lower than that of hard ferrite, and the purpose of the rare earth magnet cannot be achieved.Therefore, the amount of Al added should be 15 atomic % or less, and the amount of Ga should be 6 atomic % or less.

The alloy having the composition shown in Table 1 is melted, poured into a U-shape constructed using a soft magnetic mold 2, and after cooling, a lid is welded to the upper part.
It was heated to 0°C and hot rolled. Then, heat treatment was performed to obtain a joined body of the permanent magnet 1 and the soft magnetic mold 2. The magnetic properties of this permanent magnet 1 are shown in Table 2.

The obtained joined body was cut into a desired shape, and then a yoke 3 was fixed thereon to form a permanent magnet magnetic circuit for a magnetron.

[Effects of the Invention] As described above, the method for manufacturing a permanent magnet for a magnetron according to the present invention is sufficient by simply subjecting a cast ingot to hot working and heat treatment, which facilitates mass production, without going through the steps of crushing and sintering. It is possible to obtain a high coercive force, significantly reduce the production process of permanent magnets, and provide a low-cost permanent magnet for magnetrons.

Furthermore, as a magnetic property, the maximum energy product of Example 1
Since it has a magnetic property of 16 to 17 (MGOe), about seven times that of conventional ferrite magnets, it is possible to construct a small magnetron.

In addition, joining magnets to other structural members is generally difficult due to the poor machinability of magnets, but in the present invention, since soft magnetic molds are solid phase joined to both sides of the magnet, screw holes are drilled into the mold parts. By these methods, the ease of assembling the entire magnetic circuit can be greatly improved.

The manufacturing method of the present invention is also effective for manufacturing permanent magnets for devices such as traveling wave tubes that control charged particles using a static magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a permanent magnet for a magnetron manufactured by the manufacturing method of the present invention. 1... Permanent magnet 2... Soft magnetic mold 3... York and above Applicant Seiko Epson Co., Ltd. agent Patent attorney Kisanbe Meiki and 1 other person Figure 1

Claims (3)

[Claims] (1) In the method for manufacturing a permanent magnet for magnetron, R
(wherein R is at least one rare earth element including Y), a transition metal, and an alloy whose basic components are boron are melted and cast, and then the cast ingot is hot worked at a temperature of 500°C or higher. A method for manufacturing permanent magnets for magnetrons. (2) Process of melting and casting the magnetic alloy, then covering the cast ingot with a soft magnetic material, performing hot working at a temperature of 500°C or higher, and then heat treatment at a temperature of 250°C or higher to join the permanent magnet and the soft magnetic material. Claim 1, characterized in that a body is manufactured and further post-processing such as cutting is performed so that a part of the soft magnetic material portion of the joined body remains as a structural member or a magnetic circuit.
A method for manufacturing a permanent magnet for a magnetron described in . (3) The process of melting the magnet alloy and casting it into a mold made of a soft magnetic material or a material used for bonding with the magnet. The method is characterized in that a bonded body of a permanent magnet and a mold material is produced by heat treatment at a high temperature, and further post-processing such as cutting is performed so that a part of the mold material portion of the bonded body remains as a structural member or a magnetic circuit. A method for manufacturing a permanent magnet for a magnetron according to claim 1.