JPH01212702A - 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 ethylene vinyl acetate copolymer, low density polyethylene, etc., under the prescribed condition. CONSTITUTION:The binder for injection molding composing of wt.% of 40-60% ethylene vinyl acetate copolymer and/or low density polyethylene, 25-35% ester polymethacrylate copolymer, 5-10% dibutyl phthalate or diethyl phthalate and the balance parrafine wax, 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 conventional techniques as described above, it is not possible to create a complicated 1-way shape using a plate material. There is a sintering method as a method that improves this point, but in this case also the vertical direction (
It can be applied to some extent in the pressure direction (pressure direction), but it can be adapted to a certain extent in the lateral direction (pressure direction).
There is a problem in that there are restrictions on the manufacturing method in the direction perpendicular to the pressing direction. 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.

The second method for producing a magnetic material of the present invention is to use one or two of ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) and low-density polyethylene (hereinafter abbreviated as LDPE) in weight%. 40 to 60%, 25 to 35% of polymethacrylic acid ester copolymer (hereinafter abbreviated as PME), and 5 to 1% of one of dibutyl phthalate (hereinafter abbreviated as DBP) or diethyl phthalate (hereinafter abbreviated as DEP).
The binder is characterized by being an injection molding binder consisting of 0% paraffin wax and the remainder being paraffin wax.

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, it must be easily decomposed, vaporized, and removed during sintering in a short period of time without adversely affecting the molded product. If the amount of binder is too small, the fluidity will be poor and the injection molding machine will be subjected to a large load, but the molding will not be able to be molded into the desired 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. This can result in damage to the shape of the body. In the present invention, the surface of the metal powder is modified with a coupling agent to obtain fluidity with a lower binder, thereby increasing the amount of binder to 15 to 40%.

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 from this point of view below.

a) EVA, LDPE These are thermoplastic resins, and have excellent fluidity and degreasing properties, and also have the ability to maintain the shape of the injection molded product while other components are thermally decomposed and removed during binder removal. has. 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) PME This component is also a thermoplastic resin like EVA and LDPE, and its hair quality also has the same effect as the above resins, but the characteristic of this component is that it has a lower thermal decomposition temperature than EVA and LDPE. It is a point to have. 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 the content is less than 25% or more than 36%, thermal decomposition will not occur continuously and the injection molded product will be damaged, so the content was set at 25 to 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 the content is above 10% to 15%, the wax shrinks rapidly during injection molding, resulting in poor dimensional accuracy.

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 the 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. Surface treatment of metal powder was performed. These metal powders were mixed into the composition shown in Table 1, and the composition shown in Table 1 was also prepared.
A binder having the composition shown in Table 1 was added in the amount shown in Table 1, mixed for 1 hour at 135° C. using a pressure kneader, cooled and pulverized 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, an injection pressure cuff of 00 kg/cm2, and a diameter of 3 mm.
A ring-shaped sample of 3×φ45×t5 mm was molded.

The ring sample was heated to 500°C in a hydrogen atmosphere at a temperature increase of 20°C/h to remove the binder, and then heated to 1200°C.
Sintering was performed at C for 4 hours. 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. The magnetism of the obtained sintered body was measured using a DC magnetization measuring machine using an excitation coil and a search coil each wound with 50 turns. Table 2 shows the results of density measurement using the Archimedes method. For comparison with the present invention, molten pure iron, permalloy (45Ni-Fe), and permendur (50Co-Fe) were used.

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

[Example-2] As raw material powders, 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. The mixture was mixed for 1 hour at 135°C using a pressure kneader, 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 at an injection temperature of 160°C.
Injection pressure cuff 00Kg/cm2, φ33×φ45
A ring-shaped sample with xt5mm was molded. The ring sample was heated to 500°C in a hydrogen atmosphere at a rate of 20°C/h.
After the binder was removed by heating to 1,200° C., sintering was performed 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.

Table 3 Table 4 [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 and blended with a binder whose main component is a thermoplastic resin. After mixing, the required shape is obtained by injection molding, and the molded body is sintered to obtain a sintered magnetic material having excellent magnetic performance. This makes it possible to easily and inexpensively manufacture thin, complex-shaped parts such as the core yoke of a stepping motor or the lens actuator yoke of a CD, etc.

Although the present invention has been described with respect to 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 Representative Patent Attorney Mogami and 1 other person

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, in weight percent, 40 to 60% of one or two of ethylene vinyl acetate copolymer and low density polyethylene, 25 to 35% of polymethacrylate copolymer, dibutyl phthalate or diethyl 2. The method for producing a magnetic material according to claim 1, characterized in that an injection molding binder is used which has a blend composition of 5 to 10% of one kind of phthalate and the remainder of paraffin wax. (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.