JPS63221965A - Method and device for polishing pipe material - Google Patents

Abstract

PURPOSE:To polish both inner and outer surfaces of a pipe and perform deburring as well as to perform such polishing that is excellent in working properties even if the pipe is long in size and has a step difference and a hole or the like, by feeding plastic magnets to the inner part of a pipe material and magnetic abrasives to both the inner and outer parts, while installing a magnetic field to be relatively rotated to the pipe material, and polishing it. CONSTITUTION:Plural pieces of plastic magnets 1 are fed to the inside of a pipe P and magnetic abrasives to both inner and outer parts of the pipe P respectively, while magnetic poles 7a and 7b are set up at the outside at an interval of 180 deg., and they are opposed to the peripheral surface via a clearance. If so, these plastic magnets 1 are aligned according to polarity, and these magnetic abrasives 40 are oriented among these plastic magnets 1, an inner and outer surfaces of the pipe P and these magnetic poles 7a and 7b, forming a magnetic abrasive brush. And, when the pipe P is relatively rotated and driven to each magnetic field of these magnetic poles 7a and 7b, both inner and outer surfaces are uniformly polishable even in the case of a long pipe or a workpiece with a step difference and a hole or the like. Further, deburring work or the like is also sufficiently performed, whereby such polishing of good working properties as there are no scattering of abrasive grains and nonoccurrence of dust can be done.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is for polishing the inner or outer surfaces of pipe materials such as sanitary pipes, various piping materials, cylinders, linear motion bearing cages, etc. The present invention relates to a method and apparatus for polishing pipe materials using a magnet and a granular magnetic abrasive material.

[Background of the invention]

The inner surfaces of pipes used in food, drug, and fine chemical manufacturing equipment are treated to prevent bacteria, impurities, and substances passing through from adhering to them, and to facilitate sterilization and cleaning.
It needs to be polished to a near-mirror finish. Similarly, the outer surface of the pipe must be polished to prevent the adhesion of germs, to facilitate sterilization and cleaning, and to improve its appearance. Stainless steel acid sanitary pipes are commonly used as this type of pipe. Due to the usage problems mentioned above,
The surface roughness of this sanitary pipe after polishing is required to be approximately Ryaax = 2.5 pLm or less at the maximum height.

[Problem that the invention seeks to solve]

Conventionally, a puff polishing machine or a belt polishing machine has been used for polishing sanitary pipes. However, when polishing the inner surface of a long pipe using a puff polishing machine, a long rotation shaft is required to rotate the puff at high speed within the pipe. As the rotation axis becomes longer, the pressure applied by the puff to the inner surface of the pipe tends to become uneven. Furthermore, when using a belt polisher, the polishing belt moving at high speed inside the pipe must apply pressure uniformly over the entire length of the pipe, but when polishing a long pipe, the pressing force of the polishing belt is insufficient. It tends to be uniform. Therefore, in polishing operations using a puff polisher or a belt polisher, it is difficult to ensure uniformity of the surface roughness of the inner surface of the pipe after polishing. Especially when using a belt grinder, Rmax
= It is difficult to obtain a surface roughness of less than 2 p, m. Furthermore, in the polishing work on the two sides, there is a risk that the abrasive grains will scatter, and dust is likely to be generated. Recently, the automation of polishing the outer surface of pipes using puffs has progressed, but measures are needed to prevent the scattering of abrasive grains and the generation of dust.

Furthermore, pipe materials other than pipes, such as engine cylinders and direct-acting bearing cages, may have differences in level or
There are protrusions and depressions, and some are even partially perforated. If only the conventional method described above is used for polishing such pipe materials, sufficient polishing cannot be performed, and deburring cannot be performed satisfactorily.

The present invention solves the above-mentioned conventional problems, and can be applied to long pipes such as sanitary pipes, or processed products with steps and holes such as engine cylinders and bearing cages. A pipe material that can not only be polished to a uniform, near-mirror finish on the inner or outer surfaces, but also capable of sufficient deburring work, and that can be polished with good workability without scattering abrasive grains or generating dust. The present invention aims to provide a polishing method and apparatus.

[Specific means for solving the problem] The present invention supplies a plastic magnet made of a combination of resin and a magnetic material and a granular magnetic abrasive material to the inside of a pipe material, which is an object to be polished, and A magnetic field is provided that rotates along the outer peripheral surface of the pipe material relative to the pipe material, the plastic magnet is rotated following the magnetic field, and the inner surface of the pipe material is polished by the magnetic abrasive material oriented between the plastic magnet and the pipe material. A method for polishing a pipe material, and a method in which a magnetic pole that forms a magnetic field that rotates along the outer peripheral surface of a pipe material that is an object to be polished and rotates relative to the pipe material, and a resin and a magnetic material supplied into the pipe material are combined. This is a tube material polishing device that is composed of a plastic magnet and a granular magnetic abrasive material.

[For production]

In the present invention, a plastic magnet supplied inside the tube is held by a magnetic field from magnetic poles facing the outer surface of the tube. In addition, the granular magnetic abrasive material supplied into the tube material is
A magnetic polishing brush with magnetic abrasive material oriented is formed on the inner surface of the tube, attracted around the plastic magnet and interposed between the plastic magnet and the inner surface of the tube. A plastic magnet within the tube is driven to rotate relative to the tube by a rotating magnetic field that rotates relatively along the outer circumference of the tube, and the inner surface of the tube is polished by the magnetic polishing brush. For example, in the case of a long pipe, by moving the polishing position in the axial direction, the inner surface of the vibrator can be uniformly polished over its entire length. Alternatively, in the case of thin rings and bearing cages, the inner surface can be polished uniformly regardless of unevenness, and deburring can be performed efficiently. In this polishing operation, the magnetic field applied from outside the tube is not necessarily uniform with respect to the plastic magnet, and either end of the plastic magnet inside the tube is drawn to the inner surface of the tube. However, at this time, a magnetic abrasive material is interposed between the plastic magnet and the inner surface of the tube material, and the hardness of the plastic magnet is low, so that the inner surface of the tube material is not damaged. Furthermore, if a magnetic abrasive material is oriented between the outer surface of the tube and the magnetic pole located on the outside, it is possible to polish not only the inner surface but also the outer surface of the tube at the same time.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical cross-sectional view showing the inside of a vibrator in a pipe polishing method and apparatus according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line n-II in FIG. 1, and FIG. FIG. 4 is a side view showing an example of the overall structure of the polishing apparatus, and FIG. 5 is a sectional view taken along the line v--2 showing the structure of the magnetic pole in the apparatus shown in FIG.

The illustrated embodiment shows a method and apparatus for polishing a straight and long pipe P as an example of a pipe material to be polished. This pipe P is a pipe made of a non-magnetic material such as stainless steel, and the polished pipe is used as a sanitary vibrator in equipment for producing food, medicine, fine chemicals, and the like.

In the first embodiment shown in FIGS. 1 and 2, inside the pipe P,
A plurality of plastic magnets 1 are supplied. This plastic magnet 1 is a composite (bonding) of a ferrite magnetic material and a rare earth magnetic material using a resin. In this embodiment, each plastic magnet 1 has a rectangular parallelepiped shape, and is anisotropically magnetized as shown in FIG. 3, with one end serving as a N pole and the other end serving as an S pole. .

Further, a magnetic abrasive material 40 is supplied into the pipe P. This magnetic abrasive material 40 is made by mixing iron powder with a reaction product of aluminum oxide and iron, for example, and further mixing polishing oil for lubrication and cooling as necessary.

Magnetic poles 7a and 7b are provided on the outside of the pipe P.

The magnetic poles 7a and 7b are arranged at an interval of 180 degrees, and each faces the outer peripheral surface of the pipe P with a gap therebetween. Each of the magnetic poles 7a and 7b has a polarity of N pole or SF1, and the plurality of plastic magnets 1 in the pipe P are aligned according to the polarity of the magnetic poles 7a and 7b. Then, the magnetic abrasive material 40 in the pipe P is gathered around the plastic magnet l, and is oriented between the plastic magnet 1 and the inner surface of the pipe P to form a magnetic abrasive brush, as shown in FIG. be done. In this first embodiment, a magnetic abrasive material 40 is also supplied between the outer surface of the pipe P and the magnetic poles 7a, 7b, and this magnetic abrasive material 40 creates a magnetic flux between the magnetic poles 7a, 7b and the plastic magnet 1. A magnetic polishing brush is also formed on the outer surface of the pipe P.

In the overall configuration of the apparatus shown in FIGS. 4 and 5, the polishing portion of a long pipe P is supported by casters 11 placed on a pedestal IO. This caster 11 is
For example, it is composed of a pole made of a soft material that comes into contact with the outer peripheral surface of the pipe P, and a spring that presses the pole against the pipe P. The casters 11 are arranged at intervals in the axial direction across the polishing work part of the pipe P, and at each support part, the casters 11 are arranged so that they can support the outer peripheral surface of the pipe P from three directions, for example. It is located. The casters 11 allow the pipe P to move axially and rotate.

Further, a U-shaped yoke 7 is installed on the pedestal 10, and each of the magnetic poles 7a and 7b is formed by an end of this yoke 7 (see FIG. 5). Further, an excitation coil 20 is wound around the yoke 7, and the current flowing through the excitation coil 20 causes the ends of the yoke 7, that is, the magnetic poles 7a and 7b, to have north and south polarities.

The left end of the pipe P in the drawing is supported on a movable frame 30. This movable frame 30 is movably installed on a rail 31 using wheels 32 and 33. One wheel 33 is a driving wheel, and a motor Mb provided on the movable frame 30
The motive power is transmitted via the belt 34, so that the movable frame 30 can move linearly on the rails 31.

The left end of the pipe P is held by a chuck 35 that is directly connected to a motor Me with a speed reducer. The pipe P is rotationally driven by this motor Mc. Furthermore, the motor Me is fixedly mounted on the vibration base 36. The vibration base 36 is supported on the pedestal 30 by a linear motion bearing 37 so as to be movable in the left-right direction in the figure. The vibrating base 36 is vibrated and driven in the left-right direction in the figure by a vibrating mechanism composed of, for example, a motor Md and a cam 38. As a result, the pipe P is vibrated in the axial direction at a frequency of, for example, 15 Hz and an amplitude of about 5 mm. It is also possible to use this vibration mechanism with a structure other than that shown in the figure.

Next, the pipe polishing work will be explained.

The end of the pipe P made of a non-magnetic material such as stainless steel, which is the object to be polished, is attached to the movable frame 3 as shown in FIG.
The polishing work part is held by the chuck 35 on the mount 1.
It is held on casters 11 on 0. Further, a plurality of rectangular parallelepiped plastic magnets 1 and a magnetic abrasive material 40 shown in FIG. 1 are supplied into the pipe P. The magnetic abrasive material 40 is attracted to each of the plurality of plastic magnets 1, and the plastic magnets 1 themselves are also attracted to each other, so the plastic magnet 1 and the magnetic abrasive material 40 can be supplied into the pipe P as one lump. can. Further, in this first embodiment, as shown in FIGS. 1 to 3, the magnetic abrasive material 40 is also supplied between the outer surface of the pipe P and the magnetic poles 7a and 7b.

When the coil 20 on the stand 10 is energized, for example, the yoke 7
One magnetic pole 7a, which is the end of the magnetic pole 7a, is the north pole, and the other magnetic pole 7b is the south pole. Multiple plastic magnets 1 inside the pipe P
1 and 2 depending on the polarity of the magnetic poles 7a and 7b.
They are arranged in the state shown in the figure. Also, due to the magnetic field between the magnetic poles 7a and 7b and the plastic magnet 1, the magnetic abrasive material 40 in the pipe P is oriented on the inner surface of the pipe, and this magnetic abrasive material 40 causes the magnetic abrasive brush that contacts the inner surface of the vibrator to become oriented. It is formed. At this time, the plurality of plastic magnets l located inside the pipe P have left and right magnetic poles 7a and 7.
The plastic magnet 1 is not necessarily held at the center position by the magnetic poles 7a and 7b, but depending on the imbalance of magnetic flux density and the arrangement of the plastic magnets 1, the plastic magnet 1 is attracted toward either the magnetic pole 7a or 7b.

Therefore, either end of the plastic magnet l (for example, the end on the A side in FIG. 1), which has become a lump due to its own polarity, comes into contact with the inner surface of the pipe. however,
Since the magnetic abrasive material 40 is attracted to the periphery of the plastic magnet 1, the magnetic abrasive material 40 intervenes between the plastic magnet 1 and the inner surface of the pipe where it comes into contact with the inner surface of the pipe. It never hits the inside of the pipe directly. Furthermore, even if the plastic magnet 1 directly hits the inner surface of the pipe, damage to the inner surface of the pipe P can be avoided because the hardness of the plastic magnet 1 itself is low. At the end of the plastic magnet 1 that is away from the inner surface of the pipe P (for example, the end on the B side in FIG. 1), the magnetic abrasive material 40 is oriented by the magnetic flux between this end and the inner surface of the pipe. , a magnetic abrasive brush is formed that contacts the inner surface of the pipe.

During the polishing work, the motor M on the movable frame 30 shown in FIG.
e, the pipe P is driven to rotate relative to the magnetic field of the magnetic poles 7a and 7b. Due to this rotational movement, the magnetic pole 7
The plastic magnet 1 held by the magnetic fields from a and 7b rotates relative to the pipe P, and the magnetic polishing brush made of the magnetic abrasive material 40 formed between the plastic magnet 1 and the inner surface of the vibrator rotates. Slide on the inner surface of the pipe P,
The inner surface of the pipe is polished. At this time, magnetic poles 7a, 7
Even if the plastic magnet l is biased in one direction inside the pipe P due to an imbalance in the strength of the magnetic field from b, and one end of the plastic magnet 1 is attracted to the inner surface of the pipe P, the plastic magnet 1 and the pipe Since the magnetic abrasive material 40 is interposed between the inner surface of P and the inner surface of P, this magnetic abrasive material 4
0 acts as a rolling bearing, and the plastic magnet 1 is able to slide smoothly against the inner surface of the pipe. Also, the magnetic abrasive material 4 supplied to the outer surface of the pipe P
0 is oriented by the magnetic field of the magnetic poles 7a and 7b, this magnetic polishing brush slides on the outer circumferential surface of the pipe P, and the outer surface of the pipe P is simultaneously polished.

Further, simultaneously with the rotation of the pipe P, the movable frame 30 is moved to the right in the figure by the force of the motor Mb, and the polishing portion of the pipe P is gradually moved to the left along the axis. This causes the magnetic pole 7a.

The opposing position of 7b will gradually move in the axial direction of the pipe P. The plastic magnet l and the magnetic abrasive material 40 are also moved in the axial direction inside the pipe P by the movement of the relative positions of the magnetic poles 7a and 7b. Then, the polishing position by the magnetic polishing brush gradually moves in the axial direction of the pipe P.

Furthermore, in order to perform the polishing operation efficiently, a movable stand 30 is installed.
The upper motor Md rotates, and the vibration base 36 is vibrated in the left-right direction in the figure by the cam 38, giving vibration to the pipe P in the axial direction. By applying vibration to the pipe P, the magnetic polishing brush made of the magnetic abrasive material 40 can be slightly slid in the axial direction relative to the inner and outer surfaces of the pipe P, so that efficient polishing work can be performed. Become.

In this embodiment, instead of rotating the pipe P, the magnetic poles 7a and 7b may be rotated along the outer periphery of the pipe P, or the magnetic poles 7a and 7b may be rotated along the outer periphery of the pipe P.

7b and the pipe P may be rotated in opposite directions.

FIG. 6 (side sectional view) and FIG. 7 (longitudinal sectional view) show a second embodiment of the present invention.

In this second embodiment, one plate-shaped plastic magnet l is inserted into the pipe P. Also, magnetic abrasive material 40
is supplied to the inside and outside of the pipe P. As in the first embodiment, the plastic magnet l is a composite (bonding) of ferrite magnetic material and rare earth magnetic material with resin, and one end is an N pole and the other end is an S pole. It is magnetized to have polarity.

In this embodiment, by rotating the pipe P relative to the magnetic poles 7a and 7b, the plastic magnet 1 is rotated within the pipe P, and the inner surface of the pipe P is rotated in the same manner as in the first embodiment. is polished. At the same time, the outer surface of the pipe P is also polished.

Moreover, in the embodiment shown in FIGS. 6 and 7, the magnetic poles 7a and 7b
At the tip of the pipe P, there is a groove 8a extending in the axial direction of the pipe P;
A plurality of notches 8b are formed perpendicular to a.

By providing the grooves 8a and notches 8b at the tips of the magnetic poles 7a and 7b, the area of the magnetic poles 7a and 7b facing the pipe P can be reduced, and the density of the magnetic flux extending to the plastic magnet 1 can be increased. Therefore, it is possible to form a magnetic polishing brush using the strongly oriented magnetic abrasive material 40.

FIG. 8 (side sectional view) and FIG. 9 (longitudinal sectional view) show a third embodiment of the present invention.

In this embodiment, small pieces of plastic magnets 1 are fixed to both ends of a ferromagnetic metal plate 21. Due to the relative rotation between the pipe P and the magnetic poles 7a and 7b, the metal plate 21 and the plastic magnet 1 integrated therewith within the pipe P rotate relative to the pipe P.

The magnetic abrasive material 40 is attracted to the plastic magnet 1, and a magnetic abrasive brush is formed between the end of the metal plate 21 and between the plastic magnet 1 and the inner surface of the pipe. In this embodiment, since the passage resistance of the magnetic flux in the ferromagnetic metal plate 21 is small, the magnetic flux density between the metal plate 21, the plastic magnet l, and the magnetic poles 7a and 7b facing outside the pipe is high. This makes it possible to form a magnetic polishing brush using the strongly oriented magnetic abrasive material 40. Furthermore, as the magnetic flux density increases, the metal plate 21 and the plastic magnet 1 can more easily follow the rotation of the magnetic poles 7a and 7b.

FIG. 10 shows a fourth embodiment of the invention.

In this embodiment, a plurality of magnetic poles 22 are arranged at equal pitches around the outer periphery of the pipe P, and a coil 23 is wound around each of them. A current is sequentially passed through the coil 23, and the magnetic poles 22 sequentially have N or S polarity, so that a clockwise rotating magnetic field is formed around the outer periphery of the pipe P. The same plastic magnet 1 and magnetic abrasive material 40 as shown in the embodiments of FIGS. 6 and 7 are supplied into the pipe P. A clockwise rotating magnetic field is formed on the outer surface of the pipe P, and the pipe P itself is rotated in the counterclockwise direction, so that the magnetic abrasive material is oriented between the plastic magnet 1 and the inner surface of the pipe P. By 40 magnetic polishing brushes,
The inner surface of the pipe is polished. Note that this fourth embodiment is similar to the ninth embodiment.
Unlike the embodiments shown in the figures, only the inner surface of the pipe P can be polished, and the outer surface cannot be polished.

In addition, in the above embodiment, when the pipe P is polished by the apparatus shown in FIGS. 4 and 5, the mounts 10 are arranged at multiple locations, and the polishing work is simultaneously performed at multiple locations where each mount 10 is provided. is also possible. This makes it possible to efficiently polish the entire long pipe P in a short time.

Further, the object to be polished is not limited to the straight pipe P shown in each of the above embodiments, but various pipe materials such as various piping materials, engine cylinders, and direct-acting bearing cages can be polished. In addition, since soft polishing can be performed using a magnetic polishing brush, it is possible to polish steps, protrusions, depressions, etc. on the inner and outer surfaces of the tube material, and even those with holes can be polished.

At the same time, it is also possible to remove burrs from each of the above locations.

Next, the results of actual polishing work will be explained.

The polishing work is carried out using the equipment shown in Figs. 1 to 5.
The experiment was carried out without applying the excitation operation by the excitation mechanism Md and 38 shown in FIG.

Pipe P is stainless steel acid, outer diameter 38,1
mm, and wall thicknesses of 1 and 2 mm were used. The surface roughness before polishing is the maximum height Rmax = 6JL on the inner surface of the pipe.
m, center line average roughness Ra = 0.6 gm, and Rmax = 4. OpLm, Ra =0.57
It was bm.

The plastic magnet 1 is a composite of rare earth magnetic material with resin, has a cubic shape of 5 mm square, and is anisotropically magnetized. The number of plastic magnets l is the same as each magnetic pole 7a in FIG.

18 pieces were supplied per 1 cm in the axial length of the pipe 7b.

The magnetic abrasive 40 is made by mixing iron powder with a reaction product of aluminum oxide and iron, and has a minimum particle size of 44ILm, a maximum particle size of 1105IL, and an average particle size of 80pm. Approximately 30g of the inside of the pipe P,
Approximately 30 g was applied to the outer surface. At the same time, apply a polishing liquid to the inner and outer surfaces of the pipe P for about 30 minutes. 0g was supplied.

The magnetic poles 7a and 7b are approximately 1.5 mm from the outer surface of the pipe P.
When the magnetic poles 7a and 7b and the pipe P were rotated at a relative rotation speed of about 150 rpm while separated and facing each other for polishing work, the roughness of the inner surface of the pipe P was Rmax.
= 0.8 pLm, Ra = 0.10 JLm, and the roughness of the outer surface is Rmax = 1.3 JLm, Ra = 0
．． I was able to finish it at 10pm.

〔Effect of the invention〕

As described above, according to the present invention, the following effects can be achieved.

(1) By simply supplying a plastic magnet and a magnetic abrasive material into the tube and moving the tube relative to the magnetic field, polishing operations can be performed on the inner or outer surfaces. In other words, polishing can be performed by simply inserting a plastic magnet or the like into the tube material, making the work easy.

(2) Even if the object to be polished is a long pipe, the inner or outer surfaces can be polished uniformly.

(3) Polishing is possible even if the pipe material has steps, protrusions, depressions, or holes on its inner and outer surfaces.

It is also possible to remove gaps such as steps.

(4) Since the magnetic abrasive material is attracted to the plastic magnet, the magnetic abrasive material can be supplied without scattering by simply inserting a lump in which both materials are attracted into the tube. Furthermore, it is also easy to discharge the pipe material after polishing.

(5) Even if the magnetic field from the magnetic poles that sandwich the pipe material is unbalanced, the plastic magnet is biased to one side within the pipe material, and one end of the plastic magnet is attracted to the inner surface of the pipe material, the magnetic field around the plastic magnet is Since the magnetic abrasive material is attached, the magnetic abrasive material always comes into contact with the inner surface of the tube material. Furthermore, even if the plastic magnet hits the inner surface of the tube, the inner surface of the tube will not be damaged because the hardness of the plastic magnet is low. In addition, when the plastic magnet and the inner surface of the pipe material move relative to each other, the magnetic abrasive material interposed between them rolls, so the sliding friction resistance between the plastic magnet and the inner surface of the pipe material decreases, and the plastic magnet moves against the inner surface of the pipe material. It becomes relatively easy to move.

(6) If a plurality of small pieces of plastic magnets are used as in the first embodiment shown in Figs. You can deal with it by changing it. In addition, when multiple plastic magnets are used, only a few are facing the inner surface of the tube with magnetic abrasive material interposed between them, so even if these few become worn out, the other magnets will not be worn out. , overall, the usable life period becomes longer.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing the inside of a pipe in a pipe polishing method and apparatus according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a formation of a magnetic polishing brush. FIG. 4 is a side view showing the overall structure of the pipe polishing device; FIG. 5 is a sectional view taken along the line V-■ in FIG. 4 showing the magnetic pole structure; 7 is a side sectional view showing the inside of a pipe, showing a second embodiment of the present invention, FIG. 7 is a longitudinal sectional view of FIG. 6, and FIG. 8 is a side sectional view showing the inside of a pipe, showing a third embodiment of the invention FIG. 9 is a longitudinal cross-sectional view of FIG. 8, and FIG. 10 is a cross-sectional view showing the structure of a magnetic pole, showing a fourth embodiment of the present invention. P... Straight pipe which is an example of pipe material, 1... Plastic magnet, 7a, 7b... Magnetic pole, lO... Frame, ll... Caster, 22... Magnetic pole forming a rotating magnetic field. , 23... Coil, 30... Moving frame, Mb
...Motor for moving the pipe in the axial direction, Mc
...Motor that rotates the pipe, 40...Magnetic abrasive material.

Claims (8)

[Claims] (1) A plastic magnet made of a combination of resin and magnetic material and a granular magnetic abrasive material are supplied inside the tube material that is the object to be polished, and rotated along the outer peripheral surface of the tube material and relative to the tube material. A method for polishing a tube material, in which a magnetic field is provided to rotate the plastic magnet following the magnetic field, and the inner surface of the tube material is polished by the magnetic abrasive material oriented between the plastic magnet and the tube material. (2) The method of polishing a tube material according to claim 1, wherein the plastic magnets are small pieces and a plurality of them are supplied inside the tube material. (3) The method for polishing a tube material according to claim 1, wherein the plastic magnet is slightly smaller than the inner diameter of the tube material, and one plastic magnet is supplied in the tube material. (4) A plastic magnet formed by combining a magnetic pole that forms a magnetic field that rotates along the outer circumferential surface of a tube material that is an object to be polished and rotates relative to the tube material, and a resin and a magnetic material that are supplied into the tube material; A pipe material polishing device consisting of granular magnetic abrasive material. (5) The apparatus for polishing a tube material according to claim 4, wherein the magnetic pole is provided to face the outer surface of the tube material, and a rotation mechanism for rotating the tube material relative to the magnetic field is provided. . (6) A plurality of magnetic poles are provided at equal pitches along the outer peripheral surface of the tube material, and a coil that sequentially magnetizes the plurality of magnetic poles to form a magnetic field that rotates relative to the tube material is provided. A pipe material polishing apparatus according to claim 4 is provided. (7) The apparatus for polishing a tube material according to claim 4, wherein the plastic magnet is a small piece, and a plurality of plastic magnets are supplied inside the tube material. (8) The tube material polishing apparatus according to claim 4, wherein the plastic magnet is slightly smaller than the inner diameter of the tube material, and one plastic magnet is supplied inside the tube material.