JPH01212706A - Manufacture of magnetic material - Google Patents

Abstract

PURPOSE:To obtain a magnetic material having excellent magnetic characteristic by sintering after molding by injecting mixed material mixing metal powder with binder composing of polypropylene, diethyl phthalate, vinyl acetate copolymer, etc., under the prescribed condition. CONSTITUTION:The binder for injection molding composing of wt.% of 25-35% polypropylene, 5-10% dibutyl phthalate or diethyl phthalate, 10-15% paraffin wax and the balance ethylene vinyl acetate copolymer, is prepared. The metal powder having -400 mesh particle size is mixed with 15-40% the above binder. Successively, the binder is removed under reducing atmosphere to the injection molding body made of this mixed material. Further, the molding body after removing the binder, is sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a magnetic material by injection molding and sintering metal powder, and a binder for injection molding.

[Conventional technology] Magnetic materials include pure iron, permalloy, silicon steel, permendur, etc., but most are made by processing rolled steel into the required shape by punching, laminating, bending, etc. using a press. ing. In addition, some materials are also used that are press-formed and sintered using a powder metallurgy method.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional techniques, it is not possible to create complex shapes using plate materials. There is a sintering method that improves this point, but even in this case, it can be applied to some extent in the vertical direction (pressure direction), but it cannot be applied in the lateral direction (perpendicular to the pressure direction). has the problem that there are restrictions on its manufacturing method. The present invention is intended to solve such problems, and its purpose is to provide a method of manufacturing easily at low cost with a large degree of freedom in shape.

[Means for Solving the Problems] The first method of manufacturing a magnetic material of the present invention is to blend and mix 400 mesh under metal powder and a binder of 15 to 40% by weight, and then mix the mixture. The method is characterized by injection molding, removing the binder from the injection molded body in a reducing atmosphere, and then sintering the molded body after the binder has been removed.

In addition, the second method for producing a magnetic material of the present invention is to use 25 to 35% polypropylene (hereinafter abbreviated as PP) in terms of weight%;
5 to 50% of one of dibutyl phthalate (hereinafter abbreviated as DBP) or diethyl phthalate (hereinafter abbreviated as DEP)
It is characterized by using an injection molding binder having a blending composition of 10% paraffin wax, 10 to 15% paraffin wax, and the rest of ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA).

Furthermore, the third method of manufacturing a magnetic material according to the present invention is characterized in that the surface of the metal powder is treated with a coupling agent diluted in an alcohol solution.

[Function] As the metal powder, various metal powders obtained by manufacturing methods such as reduction method, electrolysis method, spraying method, pulverization method, etc. can be applied, and the particle size of the metal powder is determined by the fluidity when injection molding. 400 meshes or less is desirable. Powder having a particle size of 10 μm or less is desirable in order to obtain a product with a complicated shape, reduce the load on the manufacturing equipment, improve fluidity, and improve sinterability. Powder having a particle size of 400 mesh or more is not desirable because the mixture of metal powder and binder will not flow well and injection molding will be difficult.

The binder must be compatible with the raw material powder and have good moldability, and at the same time must be easily decomposed, vaporized, and removed in a short time during sintering without adversely affecting the molded product. If the amount of binder is too small, the fluidity will deteriorate and not only will it put a heavy load on the injection molding machine, but it will also not be possible to mold it into a predetermined shape. On the other hand, if the amount of binder is too large, there will be no problem with molding, but the binder may not be removed sufficiently during the process from wax removal to sintering, and the binder may remain, adversely affecting the performance of the molded product, and the binder may foam and mold. In the present invention, there is no possibility of damaging the shape of the body.
The amount of binder was adjusted to 15 to 40% by modifying the surface of the metal powder with a coupling agent to obtain fluidity with a lower amount of binder.

The binder has good wettability with the metal powder, mixes uniformly, has good fluidity, and can be easily injection molded.The binder also has to be thermally decomposed continuously and has good decomposition properties. It is necessary to maintain the content and leave no residue after decomposition.

The binder will be explained below from this point of view.

a) EVA This is a thermoplastic resin that has excellent fluidity and degreasing properties, and has the ability to maintain the shape of the injection molded product while other components are thermally decomposed and removed during binder removal. . If the blending amount is less than 40%, it becomes impossible to obtain fluidity or the ability to maintain the shape of the injection molded product during binder removal. In addition, if it is more than 61%, it will remain in the sintered body after debinding and deteriorate the magnetic performance, and it will cause foaming etc. during debinding, which will have a negative effect on the shape retention of the injection molded product, so it was set at 40 to 60%. .

b) PP This component is also a thermoplastic resin like EVA, and has properties similar to those of the resin, but the feature of this component is that it has a lower thermal decomposition temperature than EVA. By adjusting these components, thermal decomposition of the binder during binder removal progresses gradually, and the binder is removed while maintaining the shape of the injection molded article. From this, if it is less than 25% and more than 36%, thermal decomposition will not occur continuously and damage the injection molded product.
~35%.

c) DBP, DEP These components have the effect of improving compatibility with the binder and homogenizing the binder. If it is less than 5%, no effect will be observed, and if it is more than 11%, the injection molded product will be damaged when the binder is removed, so the content was set at 5 to 10%.

d) Paraffin wax It has the effect of improving the fluidity during injection molding, improving the wettability of the metal powder and binder, and homogenizing the blended mixture. Less than 10% has no effect, and 16%
If it is more than that, the shrinkage of the wax during injection molding becomes large and the dimensional accuracy deteriorates, so 10 to 15% is desirable.

e) Coupling agent By promoting the bonding between two or more different materials and improving the wettability between the metal powder and the binder, it increases fluidity and improves moldability, as well as lowering the binder content and improving binder removal properties. Surface treatment of metal powder is carried out for the purpose of achieving this. There are silane-based and titanium-based materials, but titanium-based materials are more effective in improving fluidity and reducing binder content.

On the other hand, since silane-based materials do not leave ash after sintering, they can be used when lower impurity levels are desired.

[Example] This will be explained in detail in the following examples.

[Example-1] As raw material powder, carbonyl iron powder of 10 μm or less (average particle size of 3.2 μm (Fisher, Sub, Siv, Sizer (F, S, S, S)) or less is the same),
The same nickel powder (average particle size 2.5 μm) and the same cobalt powder (average particle size 1.5 μm) were prepared, and each powder was immersed in a solution of a titanium-based coupling agent diluted in alcohol, and then dried to form a metal. The surface of the powder was treated. These metal powders were mixed to have the composition shown in Table-1, and
The binder having the composition shown in Table 1 was added in the amount shown in Table 1, and was heated to 135°C using a pressure kneader.
The mixture was mixed for a period of time, cooled, and then ground to obtain a mixture with an average particle size of 2 mm. Next, the obtained mixture was molded using an injection molding machine with an injection temperature of 160°C and an injection pressure of 00Kg/Cm2.
A ring-shaped sample with a diameter of 45 mm and a diameter of 5 mm was molded. The ring sample was heated at 20°C/h in a hydrogen atmosphere for 5 days.
After heating to 00°C to remove binder, heat to 1200°C
Sintering was carried out for 4 hours. Note that after the binder removal was completed, the temperature was not maintained, and the temperature was raised to the sintering temperature at a rate of about 12° C./min. Magnetism was measured on the obtained sintered body using a DC magnetization measuring machine with an excitation coil and a search coil each wound with 50 turns. Table 2 shows the results of density measurement using the Archimedes method. In comparison with the present invention, pure iron, permalloy (45Ni-Fe), permendur (
50Co-Fe) was used.

In the method of the present invention, no abnormality was observed in the molded product during the molding, dewaxing, and sintering steps. Moreover, the sintered body can be obtained with a relative density of about 95%, and its magnetic properties are comparable to those of soluble materials.

[Example 2] 45Ni-Fe alloy powder (average particle size 4.6 μm), 50Fe-Co (
The obtained 0 alloy powder (average particle size 4.9 μm) was surface-treated with a titanium-based coupling agent, and a binder having the composition shown in Table 3 was added in the amount also shown in Table 3. Using a pressure kneader, the mixture was mixed at 135°C for 1 hour, cooled, and then crushed to obtain a mixture with an average particle size of 2 mm. At 00Kg/cm2, φ33×φ45x
A ring-shaped sample with a diameter of 5 mm was molded. The ring sample was heated to 500°C in a hydrogen atmosphere at a rate of 20°C/h to remove the binder, and then sintered at 1200°C for 4 hours. Magnetism was measured on the obtained sintered body using a DC magnetization measuring machine with an excitation coil and a search coil each wound with 50 turns. Table 4 shows the results of density measurement using the Archimedes method.

Even when alloy powder was used, a product equivalent to Example 1 was obtained.

[Effects of the Invention] As described above, according to the present invention, metal powder of 400 mesh or less is surface-treated with a coupling agent, mixed with a binder whose main component is a thermoplastic resin, and then injection molded. By obtaining the required shape and sintering the compact, a sintered magnetic material with excellent magnetic performance can be obtained. This makes it possible to easily and inexpensively manufacture thin and complex-shaped parts, such as the core yoke of a stepping motor or the lens actuator yoke of a CD, for example.

Although the present invention has been described in terms of a method for manufacturing magnetic materials, this method can also be applied to mechanical parts and the like.

that's all Applicant: Seiko Epson Corporation ,・'cho Representative Patent Attorney Mogami and 1 other person, 2QC, -

Claims (3)

[Claims] (1) After blending and mixing 400 mesh under metal powder and 15 to 40% binder by weight, the mixture is injection molded, the injection molded body is debindered in a reducing atmosphere, and then A method for producing a magnetic material, comprising: sintering the molded body after removing the binder. (2) As the binder, by weight, 25 to 35% polypropylene, 5 to 10% of one of dibutyl phthalate or diethyl phthalate, 10 to 15% of paraffin wax, and the remaining ethylene vinyl acetate copolymer. 2. The method for producing a magnetic material according to item 1, characterized in that an injection molding binder having a blended composition is used. (3) The method for producing a magnetic material according to item 1, characterized in that the surface of the metal powder is treated with a coupling agent diluted in an alcohol solution.