KR101091565B1 - Magnetic abrasive powder and method manufacturing the same - Google Patents

Abstract

The present invention relates to a magnetic abrasive powder for abrasive processing for mirror surface processing of the surface difficult to process special pipes, pipes, tubes, etc.,

Magnetic metal powder and

Composed of a mixed powder coated on the surface of the magnetic metal powder

The mixed powder is a mixture of a metal powder and a carbide-based powder, the metal powder provides a magnetic abrasive powder which is a metal oxide powder is reduced sintered and a method of manufacturing the same.

The magnetic abrasive powder according to the present invention has an effect of excellent economic efficiency while exhibiting sufficient polishing pressure and excellent polishing ability.

Magnetic abrasive maching, Internal abrasive, Magnetic metal, Carbide, Reduction sintering

Description

MAGNETIC ABRASIVE POWDER AND METHOD MANUFACTURING THE SAME

The present invention relates to a magnetic abrasive used in the magnetic polishing method in which the abrasive is pressed onto the polishing surface by the force of a magnet to perform polishing. More specifically, a sufficient polishing pressure can be expressed by the magnetic force, thereby increasing the polishing efficiency. The present invention relates to a magnetic abrasive powder having excellent polishing performance and a method of manufacturing the same.

Recently, in the field of semiconductor, nuclear, medical, and aerospace technology, many researches and developments have been made on the polishing method for mirror surface processing of special pipes, pipes, tubes, etc. which are difficult to process.

The abrasive machining method can be roughly classified into a so-called contact polishing method for processing an abrasive tool in contact with a workpiece and a non-contact polishing method using electrical or chemical properties of the workpiece.

Here, the non-contact polishing method, which is distinguished from the contact polishing method, leaves fine processing traces on the surface of the object to be processed, and these processing traces form irregularities, resulting in impurities remaining, resulting in lower cleanliness and precision of the product. In order to solve the problem of the polishing method. Non-contact polishing methods include electrolytic polishing to improve the surface roughness of the workpiece by using the difference in corrosion rate according to the surface irregularities, and chemical polishing to chemically dissolve and smooth the uneven portions of the workpiece.

This non-contact polishing method has the advantage of improving the cleanliness and precision of the object to be processed compared to the contact polishing method, but in the case of electrolytic polishing using an electrolytic solution (phosphate, chromic acid, nitric acid, etc.) by the electrolytic solution discarded after use The environment is polluted, and even in the case of chemical polishing, various chemical solutions are used, which causes a problem of environmental pollution.

Therefore, a powder polishing method has been developed that can solve the environmental pollution problem in the non-contact polishing method and at the same time increase the processing accuracy and cleanliness. The powder polishing method uses fine particles as an abrasive, and induces abrasion by injecting the abrasive with a strong air pressure and impinges on the object, and a method of polishing by polishing a magnetic abrasive material having a magnetic property with the object. There is this

The self-polishing method is a method of compressing a magnetic abrasive material, which combines a magnetic element that can be pressed onto an inner surface of a pipe or the like with a polishing element that can polish an inner surface of a pipe, by a magnetic force to the polishing surface, thereby performing a polishing process. It is used for polishing the inner surface of metal and the plane of metal. In particular, the self-polishing method on the inner surface of the pipe causes non-uniform magnetic field distribution inside the pipe due to the magnetic poles installed on the outside of the non-magnetic pipe, and generates polishing pressure between magnetic particles and magnetic poles introduced into the pipe. Relative motion occurs between the magnetic particles and the inner surface is polished.

Looking at the conventional technology related to such a self-polishing method, Korean Unexamined Patent Publication No. 193-0012195 describes a polishing method and apparatus using magnetic force. The patent discloses a polishing apparatus for polishing non-ferrous metals and precious metals using magnetic force, comprising: polishing a magnet having a predetermined interval radially on a disk rotated by rotation of a motor, and forming a processing space thereon. In the processing space of the apparatus and the workpiece, a workpiece and a plurality of thin, short pin-shaped polishing members are mixed at an appropriate ratio, and the disk below is rotated to rotate the disk under the force of the magnet arranged on the disk. A polishing method is disclosed in which the polishing member rubs against the surface of the workpiece during flow to give luster. The polishing method of the patent is a basic example of magnetic polishing, and the driving unit may allow the abrasive to be processed into the polished body by the force of the magnetic force without direct contact. However, when a magnet is arranged on such a disc, there is a disadvantage that only the external processing of the flat surface can be performed.

In Korean Patent Publication No. 0159741, a self-polishing window and a method thereof are described. The patent uses a helical magnet having a spirally formed magnetic pole as a magnetic force generating means to act on the workpiece, thereby reducing the working time in a wide range of work and focusing on the areas where the polishing effect is hardly exhibited. It has been shown that workability can be improved compared to conventional methods by allowing machining. However, when machining this type of spiral magnet is expensive, and when used for the processing of the pipe, the spiral magnet must enter the inner surface of the pipe, there is a problem that the magnet is polished.

Korean Patent Publication No. 10-0395168 discloses a self-polishing device. The device of this patent is a device for processing the inner surface of a pipe; An iron core rotatably installed in a state where the tip portion is inserted into the inner surface of the pipe, with the magnetic abrasive particles concentrated between the inner surface; A coil installed around the iron core to generate a magnetic force by application of a current; And rotating means for rotating the iron core; A plurality of radially extending disk-shaped radially extending portions are formed at the front end portion of the iron core at predetermined intervals, and a magnetic force line is formed radially at the front end portion. According to the patent, it is possible to increase the polishing efficiency by rubbing the self-polishing particles on the inner surface more efficiently than the conventional method. However, when the inner surface of the pipe is polished, the radial disk must be processed while turning with the abrasive, so the tip and the disk must be well processed according to the diameter of the pipe. Despite being a processed product, it is consumable, and there is a disadvantage in that it is economically expensive to replace frequently.

In order to overcome these shortcomings, research is being conducted to improve the characteristics of the abrasive while polishing the inner surface of the pipe by a conventional self-polishing method. In particular, recently, by using electrolytic iron powder as a method for increasing the adhesion between the abrasive and the polishing surface to increase the polishing efficiency to increase the polishing efficiency, it has been attempted to increase the polishing efficiency in the conventional magnetic polishing apparatus.

Therefore, the present invention requires a study on economically abrasive abrasives that can be pressed against the inner surface of a pipe or the like sufficiently to exhibit sufficient polishing pressure, have a high hardness, and exhibit sufficient polishing effects.

One aspect of the present invention is a magnetic abrasive powder capable of polishing an inner surface of a pipe or the like, the magnetic abrasive powder exhibiting sufficient polishing pressure by the magnetic force of the magnetic polishing machine and exhibiting excellent polishing ability and excellent economic efficiency, and a manufacturing method thereof. It is to provide.

The present invention is a magnetic metal powder and

Composed of a mixed powder coated on the surface of the magnetic metal powder

The mixed powder is a mixture of metal powder and carbide-based powder, the metal powder provides a magnetic abrasive powder is a metal oxide powder is reduced sintered.

In addition, the present invention comprises the steps of wet mixing magnetic metal powder, metal oxide powder and carbide-based powder to prepare a mixture;

Adding a binder to the mixture and then stirring the mixture;

Preparing a slurry by adding a silane coupling agent to the stirred mixture and then stirring the mixture;

Drying the slurry to prepare an aggregate; And

It provides a method for producing a magnetic abrasive powder comprising the step of reducing sintering the aggregate in a reducing atmosphere.

Since the magnetic abrasive powder of the present invention is inexpensive and uses a ferromagnetic material, the magnetic abrasive powder is strongly attracted to the permanent magnet of the magnetic polishing machine so that a strong polishing pressure can be exerted on the inner surface of the pipe, thereby exhibiting sufficient polishing pressure. In addition, by using a carbide-based powder material with high hardness as the abrasive particles it can exhibit excellent polishing power.

In addition, the magnetic abrasive powder of the present invention improves the bonding force between the magnetic element and the polishing element through the process of reducing the fine metal oxide, thereby increasing the service life of the magnetic abrasive, thereby reducing the replacement of the abrasive, thereby having an economically superior effect.

The present inventors deeply studied a magnetic abrasive that can increase the adhesion between the abrasive and the polishing surface to increase the polishing pressure, and as a result, the metal oxide and the carbide-based powder are agglomerated on the surface of the magnetic metal powder. By reducing sintering, the surface of the magnetic metal powder is coated with a combination of a metal oxide reduced metal powder and a carbide-based powder, so as to invent a magnetic abrasive powder which is excellent in crimping performance and polishing power by a magnet and can be used for a long time. Came to.

Hereinafter, the magnetic abrasive powder of the present invention will be described in detail.

The present invention is a magnetic metal powder and

Composed of a mixed powder coated on the surface of the magnetic metal powder

The mixed powder is a mixture of metal powder and carbide-based powder, the metal powder provides a magnetic abrasive powder is a metal oxide powder is reduced sintered.

As shown in FIG. 2, the metal oxide powder has a shape in which the carbide-based powder and the metal powder are mixed with the carbide-based powder particles and mixed with the carbide-based powder to coat the magnetic metal powder having a relatively large particle size. Have

In the present invention, the magnetic metal powder and the metal powder are not necessarily the same, the magnetic metal powder corresponds to the magnetic element in the magnetic abrasive particles and corresponds to the core of the magnetic abrasive particles, and the metal powder will be described below. As described above, the particle diameter is smaller than that of the magnetic metal powder, and the oxide metal is reduced.

The magnetic metal powder of the present invention uses a ferromagnetic material in order to press the magnetic metal powder strongly on the polishing surface by the force of the magnet during magnetic polishing. Iron powder, electrolytic iron powder, etc., which exhibit ferromagnetic properties, may be used. At this time, the average particle diameter of the magnetic metal powder is preferably about 50 ~ 500㎛.

The magnetic abrasive powder of the present invention has a form in which a metal powder and a carbide powder are mixed and coated on the surface of the magnetic metal powder. As will be described below, the metal powder and the carbide-based powder is a metal oxide powder and the carbide-based powder is mixed with the metal oxide powder is reduced to the metal powder through a reduction sintering treatment in the state coated on the surface of the magnetic metal powder will be. At this time, the average particle diameter of the metal powder and the carbide powder is preferably about 5 ~ 50㎛.

The metal oxide powder may be iron oxide or a metal oxide mixed with the iron oxide component, and the carbide-based powder may be silicon carbide (SiC), titanium carbide (TiC), tungsten carbide (WC), or the like.

Hereinafter, the manufacturing method of the magnetic abrasive powder which is this invention is demonstrated in detail.

Magnetic abrasive powder of the present invention comprises the steps of wet mixing magnetic metal powder, metal oxide powder and carbide-based powder to prepare a mixture;

Adding a binder to the mixture and then stirring the mixture;

Preparing a slurry by adding a silane coupling agent to the stirred mixture and then stirring the mixture;

Drying the slurry to prepare an aggregate; And

The aggregate is prepared through reduction and sintering in a reducing atmosphere.

First, the magnetic metal powder, the metal oxide powder, and the carbide powder are wet mixed to prepare a mixture.

The magnetic metal powder may be iron powder, electrolytic iron powder, or the like exhibiting ferromagnetic properties. The average particle diameter of the magnetic metal powder preferably has an average particle diameter of 50 ~ 500㎛ in consideration of the surface roughness after polishing of the polishing object to be polished.

Preferably, the metal oxide powder is a metal oxide reduced to the same material as the metal component of the magnetic metal powder, and the metal oxide powder is preferably 5 to 50 µm having a smaller particle size than the magnetic metal powder.

The solvent used in the wet mixing is distilled water, alcohols such as ethanol, aromatic hydrocarbons such as benzene, toluene, xylene, cyclic hydrocarbons such as cyclohexanone, linear hydrocarbons such as hexane, acetone and The same ketones, esters such as ethyl acetate, and the like can be used, and are not particularly limited as long as they do not chemically react with the raw material powder.

After adding a binder to the mixture, it is sufficiently stirred. The binder may be polyvinyl alcohol, polyvinyl butyral, or the like dissolved in the solvent. As the binder, cellulose such as ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, carboxymethyl cellulose, and hydroxypropyl cellulose may be used.

After the binder is added, it is preferable to stir for 10 minutes to 10 hours at a temperature of about 40 ~ 60 ℃.

A silane coupling agent is added to the stirred mixture, followed by stirring to prepare a slurry. Since the silane coupling agent is not dissolved in distilled water, an alcohol such as ethanol, into which the silane coupling agent may be dissolved, is added together.

The silane coupling agent has two or more different reactors in its molecular structure. One is a methoxy group, an ethoxy group, etc. which can chemically bond with an inorganic substance, and the other is an epoxy group, a vinyl group, an acryl group, an amino group, a mercapto group, etc. which can chemically bond with a binder which is an organic polymer. Thus, the silane coupling agent serves to increase the adhesion or bonding force between materials with significantly different material properties, such as organic and inorganic materials. The silane coupling agent serves to enhance the bonding force between the magnetic metal powder particles, the metal oxide powder particles and the carbide-based powder particles.

Epoxy silane, methyl trimethoxy silane, methyl triethoxy silane, etc. can be used as said silane coupling agent. In addition, as the silane coupling agent, an epoxy silane coupling agent, a vinyl silane coupling agent, an acrylic silane coupling agent, an amino silane coupling agent, a mercapto silane coupling agent, or the like may be used.

Examples of the epoxy silane coupling agent include 2- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, and the like. The vinyl silane coupling agent includes vinyl trichlorosilane, vinyl tris (2-methoxyethoxy) silane, vinyl triethoxy silane, vinyl trimethoxy silane, and the like. Methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and the like, and the amino silane coupling agent includes N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N- 2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-amino Propyltriethoxysilane and the like, and the mercapto silane coupling agent is 3-mercapto Ropil trimethoxysilane, there may be mentioned a silane such as 3-mercapto-propyltriethoxysilane.

The content of the silane coupling agent is preferably 0.01 to 3.0% by weight based on the total weight of the mixture. If the content of the silane coupling agent is less than 0.01% by weight, the effect of strengthening the adhesion is not sufficient, and even more than 3.0% by weight, it is difficult to expect any more adhesion strengthening effect.

The slurry is dried to prepare aggregates. It is preferable to perform the said drying at the temperature of 150-200 degreeC. As a drying apparatus for manufacturing the aggregate, a spray dryer is preferable. The spray dryer sprays the slurry containing the powder particles and rotates with the force of the hot air to dry quickly. At this time, drying is performed in about several tens of seconds or less.

Spraying the slurry using the spray drier flies into small droplets. In this case, the spray is sprayed not only by the pressure of the nozzle but also by the rotation of the atomizer of the nozzle, and when small droplets fly by the centrifugal force at this time, a spherical particle is formed around the coarse particles. Therefore, compared with the case of the other method, the metal oxide and the carbide-based powder can be evenly adhered around the magnetic metal powder, thereby improving the efficacy of the magnetic abrasive.

The dried aggregate is reduced and sintered in a reducing atmosphere. This reduces the metal oxide powder.

As a reducing atmosphere gas, a gas containing hydrogen (H ₂ ), for example, hydrogen (H ₂ ) gas, hydrogen (H ₂ ) gas and nitrogen (N ₂ ) gas, hydrogen (H ₂ ) gas, argon (Ar) gas, etc. Can be used. The heat treatment is preferably performed at a temperature of 600 ~ 1000 ℃. If the heat treatment temperature is less than 600 ℃ may not be sufficiently reduced, if it exceeds 1000 ℃ is not economical in terms of energy costs.

In addition, the heat treatment is preferably performed for about 30 minutes to 5 hours. If the heat treatment time is short, the reduction may not be made sufficiently, if too long heat treatment time is not economical in terms of energy costs. In the heat treatment process, since the binder is made of an organic material, it is burned away.

The metal oxide powder prepared by the above method may be present in agglomerated form, and may be used as a magnetic abrasive of a desired size through a grinding process in order to be used as a magnetic abrasive.

The metal oxide is reduced to metal by the heat treatment in the reducing atmosphere. For example, when the iron oxide powder is used as the metal oxide powder and the electrolytic iron powder is used as the magnetic metal powder, the iron oxide powder is present with the carbide particles and is reduced to iron in the reduction and sintering process so as to become one with the electrolytic iron. It serves as a mold to improve the bond strength with.

Therefore, the carbide-based powder particles are bound to the electrolytic iron powder particles having a large particle size, and thus have a shape as if the carbide-based powder particles are coated on the electrolytic iron powder particles.

Hereinafter, the present invention will be described in detail through examples. However, the present invention is not limited to the following examples. 　　

(Example)

1. Preparation of Magnetic Abrasive Powder

First, 500 g of electrolytic iron powder (Iron particles, large purified gold) was well beaten with a 150 mesh standard mesh to prepare the magnetic abrasive powder (inventive material) of the present invention, thereby obtaining 340 g of electrolytic iron powder having an average particle diameter of about 100 μm.

300 g of the electrolytic iron powder was added to a 2,000 ml beaker, 50 g of silicon carbide powder (Silicon carbide, particle size -400 mesh, manufactured by Aldrich) and 1000 ml of distilled water were added thereto, mixed well with a stirrer, and iron oxide powder (Iron oxide, 50 g of a powder having an average particle diameter of about 20 µm, mixed with a 400 mesh standard mesh, was mixed.

After mixing for about 1 hour 5g of polyvinyl alcohol (Poly vinyl alcohol, Junsei) was added and stirred while dissolving at a temperature of 50 ℃ for 2 hours. The mixture obtained at this time was cooled to room temperature and further stirred for 30 minutes while slowly adding a solution of 5 g of an epoxy silane coupling agent (Shin-Etsu Silicone) and 50 g of ethanol.

The metal particle slurry thus obtained was dried using a spray dryer (180 ° C., 5000 rpm) to obtain a metal particle aggregate. The resultant metal particle aggregates were heated at a rate of 10 ° C./min up to 800 ° C. while introducing a mixed gas of nitrogen and hydrogen in a reducing atmosphere electric furnace, and then heat-treated at 800 ° C. for 1 hour to reduce iron oxide, thereby reducing the surface of silicon carbide. 350g of abrasive powder firmly attached to the obtained was obtained. A schematic diagram of the magnetic abrasive powder produced by the above method is shown in FIG. 2.

Unlike the magnetic abrasive of the present invention, the conventional self-polishing material powder (conventional material) is 300 g of electrolytic iron powder having an average particle diameter of about 100 μm and iron and alumina, which are obtained by hitting 500 g of electrolytic iron powder (Iron particle, large crystal gold) with a 150 mesh standard mesh. 75 g of commercially available magnetic abrasive particles (WA particles, an average particle diameter of about 80 µm and a large purified gold) were used.

2. Self-polishing experiment

A magnetic polishing test was conducted using the invention and the prior art. A schematic diagram of the polishing apparatus used is shown in FIG. This device is installed by fixing the pipe using the chuck of the lathe and fixing the magnetic field generating yoke composed of Neodymium permanent magnet (Fe-Nb-B) to the rotary chuck. As the permanent magnet rotates around, it transmits the magnetic force to the abrasive in the pipe so that the inner surface can be polished.

First, magnetic polishing experiments were conducted using the invention. 50 cm of a stainless 316L pipe having a diameter of 23 mm and a surface roughness Ra 0.9 µm was charged into the polishing apparatus, and 30 g of the invention material was gradually introduced into the pipe by using an input device, and the inner surface of the pipe was polished for 5 minutes by rotating the permanent magnet. .

After polishing using the invention, the surface roughness of the inner surface of the pipe became 0.2 µm in Ra value.

In addition, a magnetic polishing experiment was conducted using the conventional material. In this case, the polishing apparatus used was the same as the above apparatus, but differed only in the used abrasive. 50 cm of a stainless 316L pipe having a diameter of 23 mm and a surface roughness Ra 0.9 µm was charged into the polishing apparatus, and the inner surface of the pipe was polished for 5 minutes by rotating the permanent magnet while gradually inserting 30 g of the conventional material into the pipe using a feeding device. .

The surface roughness of the inner surface of the pipe after polishing using the conventional material was 0.5 µm in Ra value. It can be seen from the above results that the invention had better polishing force.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the apparatus which magnetically grinds a pipe inner surface using the magnetic abrasive powder of this invention.

Figure 2 is a schematic diagram showing an example of the present invention magnetic abrasive powder.

Claims (11)

Magnetic metal powder and Composed of a mixed powder coated on the surface of the magnetic metal powder The mixed powder is a metal powder and a carbide-based powder is mixed, the metal powder is a metal oxide powder is reduced and sintered, The magnetic metal powder is iron powder or electrolytic iron powder, and the metal oxide powder is iron oxide powder.  The magnetic abrasive powder of claim 1, wherein the carbide-based powder is at least one selected from the group consisting of silicon carbide (SiC), titanium carbide (TiC), and tungsten carbide (WC). delete The magnetic abrasive powder according to claim 1, wherein the average particle diameter of the magnetic metal powder is 50 to 500 µm, the average particle diameter of the metal powder is 5 to 50 µm, and the average particle diameter of the carbide powder is 5 to 50 µm. Preparing a mixture by wet mixing magnetic metal powder, metal oxide powder, and carbide powder; Adding a binder to the mixture and then stirring the mixture; Preparing a slurry by adding a silane coupling agent to the stirred mixture and then stirring the mixture; Drying the slurry to prepare an aggregate; And Reducing and sintering the aggregate in a reducing atmosphere Method of producing a magnetic abrasive powder comprising a. The method of claim 5, wherein the solvent used for the wet mixing is any one selected from the group consisting of distilled water, alcohols, aromatic hydrocarbons, cyclic hydrocarbons, linear hydrocarbons, ketones, and esters. . The method of claim 5, wherein the binder (polyvinyl alcohol), polyvinyl butyral, ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, carboxy methyl cellulose and hydroxy A method for producing a magnetic abrasive powder, which is any one selected from the group consisting of lofil cellulose. The method of claim 5, wherein the silane coupling agent comprises at least two reactors selected from the group consisting of a methoxy group, an ethoxy group, an epoxy group, a vinyl group, an acryl group, an amino group, and a mercapto group. The method for producing a magnetic abrasive powder according to claim 5, wherein the silane coupling agent is added in an amount of 0.01 to 3.0 wt% based on the total mass of the mixture. The method of claim 5, wherein the drying is performed at a temperature of 150 ° C. to 200 ° C. using a spray dryer. The method of claim 5, wherein the reducing atmosphere is carried out in a reducing atmosphere of any one of hydrogen gas, hydrogen and nitrogen gas, hydrogen and argon gas, and the reducing sintering is a magnetic heat treatment for 30 minutes to 5 hours at a temperature of 600 ~ 1000 ℃ Method for producing abrasive powder.

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