JPH0671554A - Magnetic polishing method - Google Patents

Abstract

PURPOSE:To secure an excellently efficient and good surface roughness by performing 'rough polishing' with a composite abrasive grain containing NbC and/or Al2O3 as a hard grain, and then doing 'finish polishing' with another composite abrasive grain containing TiC, SiC and/or WC as the hard grain in succession. CONSTITUTION:At the time of magnetic polishing by means of a composite abrasive grain between a ferromagnetic body and a hard grain, first 'rough polishing' is performed by a composite abrasive grain containing NbC and/or Al2O3 as this hard grain. 'Finish polishing' is carried out by another abrasive grain containing TiC, SiC and/or WC as the hard grain. Thus, a mirror finished surface of excellently efficient and good surface roughness is securable by means of magnetic polishing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic polishing method. More specifically, the present invention relates to a magnetic polishing method capable of forming a mirror surface such as a metal surface.

[0002]

2. Description of the Related Art Conventionally, abrasive grains produced by compounding hard particles of an abrasive with a ferromagnetic substance are used to generate a polishing pressure in a magnetic field to polish a surface of a metal part or the like. The magnetic polishing method is known. This polishing method is attracting attention because it is useful as a means for automating and simplifying the finishing of the die surface.

This magnetic polishing is characterized in that an order finishing roughness of less than μm can be obtained even if a relatively coarse abrasive grain of several hundreds of μm is used. This means that the abrasive grains bonded by magnetic force during polishing. It is considered that the particles have a flexible processing behavior as a whole and that the matrix of the ferromagnetic material phase-separates and relaxes the processing strain received by the particles of the hard abrasive component under stress. .

In the magnetic polishing method having such characteristics, the composite state of the hard abrasive particles and the ferromagnetic material of the matrix influences the polishing accuracy and also has a great influence on its life. Since it has been clarified that the particles are present, various ideas have been made for the abrasive grains for magnetic polishing. For example, in the past, hard particles of abrasives were mixed with ferromagnetic powders and sintered to produce, but hard particles were made to be ferromagnetic to improve the polishing characteristics and the life of the abrasives. The applicant has also proposed an abrasive grain for magnetic polishing, which is bound by a matrix composed of a melt by a plasma arc of the body (JP-A-2-224967).

Despite the progress of such concrete studies, it is not always clear about the above-mentioned magnetic polishing method regarding the relationship between the composition of the abrasive grains and the polishing performance, and the relationship between the life of the abrasive grains and the productivity. The reality is that it is not. In particular, in the case of the abrasive grains produced by melting by the above-mentioned plasma arc, it was not enough in terms of so-called precision finishing in spite of its excellent life and polishing performance. In fact, it has been found that, for example, when NbC is used as hard abrasive particles, even if a raw material having a small particle size is used, the size thereof is several times that in the manufacturing process. For this reason, the polishing performance cannot be judged by the composition of the abrasive grains based on the particle size as the raw material of the hard particles, and even in the case of this NbC, the surface roughness of the surface to be polished exceeds a certain level. There was a problem of not becoming.

Therefore, the present invention has been made in view of the above circumstances, solves the problems of the conventional magnetic polishing, and provides a sufficient basis for the relationship between the abrasive composition and the polishing performance. It is an object of the present invention to provide a new magnetic polishing method capable of performing mirror polishing as well as possible.

[0007]

In order to solve the above-mentioned problems, the present invention is to use NbC and / or Al _{2 in} magnetic polishing with composite abrasive grains of a ferromagnetic material and hard particles.
A magnetic polishing method is characterized in that rough polishing is carried out with a composite abrasive grain containing O ₃ as hard particles, and then final polishing is carried out with a composite abrasive grain containing TiC, SiC and / or WC as hard particles.

In this method, the hard particles as the abrasive are, as described above, NbC and / or Al ₂ O ₃ in the rough polishing and TiC, SiC and / or the final polishing.
Alternatively, WC is used, but the ratio of the abrasive grains to the ferromagnetic material is not limited in a strict sense, but NbC and / or Al ₂ O ₃ 40 to 70 is used.
Volume% and ferromagnet 60-30 volume% abrasive grains, Ti
It is also preferable to use 60 to 90% by volume of C, SiC and / or WC and 40 to 10% by volume of a ferromagnetic substance as abrasive grains.

In rough polishing, NbC and Al ₂ O ₃ are used alone or in combination with a ferromagnetic material, and in finish polishing, TiC, SiC and WC are used individually or in any combination thereof. Is compounded with a ferromagnetic material to form abrasive grains, which are used for magnetic polishing. At this time, it is preferable to set the composition ratio within the above range together with the composition of the abrasive grains. NbC and / or Al ₂ O ₃ hard particles, Ti
When the hard particles of C, SiC and / or WC are below or above the above range, the magnetic action is too strong,
Or, because they are too weak, the characteristic rough and finish polishing of these particles is not sufficient.

NbC, Al ₂ O ₃ , and further TiC,
Abrasive grains containing hard particles of the present invention, such as SiC and WC, can be produced by mixed sintering, but as already proposed by the present applicant, a ferromagnetic substance such as iron and hard particles are treated by plasma arc. Those manufactured by bonding by a melting method are preferably used. That is because NbC, Al ₂
O ₃ is a grain having a larger diameter than the raw material in this production and is therefore useful as an abrasive grain for rough polishing. On the other hand, TiC, SiC, and WC are grains even in the production process using a plasma arc. There is no growth in diameter, no enormous growth,
This is because the grain size of the raw material powder is maintained, so that polishing with a predetermined surface roughness can be planned and performed with the raw material powder having a predetermined particle size.

In fact, the method of the present invention allows for excellent magnetic polishing. For ferromagnetic materials, iron,
It goes without saying that iron alloys and other appropriate materials can be used. Hereinafter, examples will be shown and described in more detail.

[0012]

Example 1 Iron powder and NbC powder (average particle size 3 μm) were used in a volume ratio of 35/6.
Mix at 5 and mold. This was melted in a plasma arc melting furnace, cooled and solidified. This was crushed to obtain abrasive grains having a particle diameter of 212 to 300 μm.

The grain size of NbC in the abrasive grains was about 25 μm.
It was Using this, the magnetic polishing of the S55C steel surface is performed.
It was conducted under the following conditions. Shaft diameter: 20 mm Rotation speed: 2000 rpm Gap with work: 1.4 mm Magnetic flux density: 1T Abrasive grain amount: 2.5 g Polishing time: 15 minutes As a result, R_maxThe surface of 3.2 μm is R_max0.9μ
It was polished to m. Example 2 Volume ratio of iron powder and TiC powder (average particle size 5 μm) is 35/6
Mix in 5, mold, melt and solid as in Example 1 above.
And pulverize to obtain abrasive grains with a particle size of 212-300 μm.
It was The grain size of TiC in the abrasive grains was about 5 μm.

Using these abrasive grains, the surface of S55C steel (R _max 3.4 μm) was magnetically polished in the same manner as in Example 1 above, and it was polished to R _max 0.1 μm. Example 3 Iron powder and SiC powder (particle size 8 μm) were mixed and molded at a volume ratio of 40/60, and plasma arc melting was carried out in the same manner as in Example 1. The solidified product was crushed to obtain abrasive grains having a particle size of 150 to 212 μm. The SiC in the abrasive grains had a grain size of about 8 μm.

When polishing was performed in the same manner as in Example 1 using the abrasive grains, the surface having R _{max of} 2.7 μm had a R _{max of} 0.1.
Polished to 5 μm. Example 4 The surface of S55C steel was magnetically polished using the NbC-Fe abrasive grains of Example 1, and then further magnetically polished using the TiC-Fe abrasive grains of Example 2.

The polishing conditions at this time are the same as in Example 1 in the case of rough polishing with NbC-Fe abrasive grains.
In the case of finish polishing with Fe abrasive grains, the same procedure as in Example 1 was performed except that the polishing time was 5 minutes. By this polishing, the surface of R _{max of} 5.2 μm was polished to R _{max of} 0.1 μm. Example 5 When polishing was performed using the SiC-Fe abrasive grains of Example 3 in place of the TiC-Fe abrasive grains in Example 4, R _{max was obtained.}
The 5.2 μm surface was polished to 0.17 μm. Magnetic polishing was performed according to various abrasive grains and conditions in accordance with Examples 6 to 10 . The results are shown in Tables 1 and 2.

It can be seen that in each case, excellent polishing performance was obtained.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

As described in detail above, according to the present invention, a mirror surface having excellent efficiency and good surface roughness can be obtained by magnetic polishing.

Claims (4)

[Claims] 1. Magnetic polishing with a composite abrasive grain of a ferromagnetic material and hard particles, rough polishing is performed with a composite abrasive grain containing NbC and / or Al ₂ O ₃ as hard particles, and then TiC, SiC and / or Alternatively, a magnetic polishing method is characterized in that finish polishing is carried out with a composite abrasive containing WC as hard particles. 2. NbC and / or Al ₂ O ₃ 40-
Abrasive particles of 70% by volume and 60 to 30% by volume of a ferromagnetic material,
TiC, SiC and / or WC 60-90% by volume,
The magnetic polishing method according to claim 1, wherein polishing is performed with abrasive grains of 40 to 10% by volume of a ferromagnetic material. 3. The magnetic polishing method according to claim 1 or 2, wherein the abrasive grains are composed of hard particles bonded by a matrix made of a melt of a metal containing a ferromagnetic material. 4. The magnetic polishing method according to claim 3, wherein the magnetic polishing is performed by plasma arc melting.