KR20070088209A - Magnetic fluid grinding technique - Google Patents

Abstract

A magnetic fluid grinding method is provided to optimize the size of diamond grains used as abrasive grains and the composition ratio of abrasive grains and magnetic grains. A magnetic fluid grinding method is characterized in that a workpiece is cemented carbide and diamond grains are used as abrasive grains for grinding the workpiece. The size of diamond grains is #300 or greater, and the composition ratio of abrasive grains to magnetic grains is 45 to 55 weight%. The magnetic flux density is 0.2 to 0.6 Tesla, and grinding speed is 450 to 1650 rpm.

Description

Carbide alloy self polishing method by diamond grains {Magnetic fluid grinding technique}

1 is a schematic view showing a state that the workpiece is polished by the magnetic abrasive material

2 is a view showing the force acting on the magnetic abrasive material

3 is a schematic photo of a self-polishing apparatus

Figures 4a, 4b, 4c is a result of the self-polishing embodiment of the magnetic polishing device

5 is a result of self-polishing using GC particles

6A, 6B, and 6C show results of self-polishing using diamond particles.

7A and 7B are surface photographs of a cemented carbide alloy using GC particles and diamond particles

The present invention relates to a self-polishing method, and more particularly, to a cemented carbide self-polishing method using diamond particles.

Self-polishing is a processing method in which a magnetic polishing material comprising a magnetic material and abrasive grains as a component is used while magnetic polishing materials are arranged in a linear line along a line of magnetic force while pressing the workpiece by magnetic force. This self-polishing method is effective for grinding or removing burrs on a three-dimensional free-form surface, a cylindrical workpiece, a pipe inner pipe, etc., because the magnetic abrasive material is processed while pressing the unevenness of the workpiece, unlike the conventional method using a grinding tool.

By the way, the final idea of the part requiring high precision dimensions is complicated and various parts of the part is difficult to perform the final idea by the conventional polishing method, in most cases rely on manual work. As a polishing method to solve this problem, a polishing method using magnetic fluid has been developed and partially utilized, but a magnetic polishing method for cemented carbide has not been developed yet.

Accordingly, an object of the present invention is to provide a cemented carbide self-polishing method using diamond grains for polishing a cemented carbide component, even among components requiring high precision dimensions.

The present invention relates to a self-polishing method, and more particularly, to a cemented carbide self-polishing method using diamond particles.

Self-polishing is a processing method in which a magnetic polishing material composed of a magnetic material and abrasive grains as a component is used while the magnetic polishing material, which is arranged linearly along the lines of magnetic force, compresses the workpiece by magnetic force. This self-polishing method is effective for grinding or removing burrs on a three-dimensional free-form surface, a cylindrical workpiece, a pipe inner pipe, etc., because the magnetic abrasive material is processed while pressing the unevenness of the workpiece, unlike the conventional method using a grinding tool.

Magnetic abrasive material has a form in which the magnetic material and the abrasive grains are simply mixed with the metallized form, while the one-piece type has disadvantages such as difficulty in manufacturing and use restrictions, while the simple mixed type simply mixes the magnetic material and the abrasive grain. It is a form.

The simple mixed magnetic abrasive material is a mixture of magnetic material and abrasive grains in oil, and the oil is placed between the magnetic material and abrasive grains to transfer the compressive force of the magnetic material to the abrasive grains, which has a great effect on the polishing performance.

1 is a schematic view showing the work of polishing the workpiece by the magnetic abrasive material, magnets having different polarities are arranged on both sides of the work to generate a magnetic force, and the generated magnetic force is transmitted to the magnetic abrasive material to compress the workpiece. Then, the workpiece is rotated and vibrated up and down to be polished so as to be relative to the magnetic abrasive material and the workpiece.

2 is a view showing the force acting on the magnetic abrasive material, showing how the magnetic force plays a role in the polishing, one magnetic particle under the magnetic field is the combined force of the magnetic force (Px) in the direction of the magnetic field line (Px) and the magnetic force (Py) in the direction of the isoline line Will receive power. At this time, the force that the magnetic particles compress the abrasive particles is Pb which is the component force of the force Pa of the magnetic force. The main component Ph and the distribution force Pv, which are the components of Pb, act on polishing. Therefore, the magnetic force of the magnet may be adjusted to have various polishing pressures. However, since the magnetic force is expressed by the polishing pressure through the magnetic abrasive material, the magnitude of the magnetic force received by the particles under the magnetic field varies depending on the type of magnetic abrasive material, that is, the type of the magnetic particles. It is necessary to know that the proper grinding pressure can be controlled.

In addition, since the abrasive particles are not polished only by pressing the workpiece, there must be a relative movement between the abrasive particles and the workpiece in the compressed state. To this end, first, the workpiece is rotated to be continuously polished, and the workpiece is moved up and down to have a complicated polishing trajectory.

(Example 1)

The abrasive force acting between the abrasive grain and the workpiece is an element directly related to the abrasive performance, but the self-polishing apparatus shown in FIG. 3 is not a type of directly applying the abrasive force to the workpiece, but is a method of applying the abrasive force according to the viscosity change of the magnetic abrasive material. In addition, it is necessary to consider the strength of magnetic flux density and the magnitude of polishing force according to the polishing conditions.

The magnetic polishing apparatus shown in FIG. 3 includes a motor capable of rotating a workpiece, a chuck capable of chucking the workpiece, an electromagnet and a permanent magnet generating a magnetic field, a limit switch capable of adjusting a vertical movement vibration width of the workpiece, Each member is comprised with the column fixed.

The motor can rotate up to 1800rpm using an AC motor, and the vertical motion (oscillation) frequency of the workpiece is fixed at 0.15 Hz.

The workpiece is a solid cemented carbide rod with a length of 120 mm, a diameter of 10 mm and a hardness of HRc 74.

Magnetic particles were used by Lord's products, which are commonly used, and abrasive particles were GC # 60, # 100, # 180, # 320 and diamonds # 800, # 1500, # 3000, and # 8000. The mixing ratio of the magnetic particles and the abrasive particles was carried out by mixing at 25, 40, 50, 57% by weight ratio. The rotational speed of the main shaft was 450, 750, 1050, 1350rpm, and the magnetic flux density of the electromagnet was 0, 0.1. 0.2. Variable to 0.6 Tesla.

The GC particles are green carbide particles, and the material component is SiC, which is one of the types of particles used in the grinding wheel.

In this embodiment, the polishing force can be obtained by the following equation.

Where P is the net power consumption, F is the polishing force, and V is the workpiece rotation speed.

Figures 4a, 4b, 4c is a result of the embodiment, Figure 4a is a view showing a change in polishing force according to the magnetic flux density, the greater the magnetic flux density, the stronger the bond between the magnetic particles and the higher the viscosity of the magnetic abrasive material, the magnetic flux density The larger the value, the greater the polishing force.

Figure 4b is a view showing the polishing force according to the size of the abrasive grains, the smaller the abrasive grains, the greater the number of abrasive grains acting on the workpiece, the polishing force was greater.

Figure 4c is a view showing a change in the polishing force according to the mixing rate of the abrasive particles, when only composed of the magnetic particles there is no element that prevents the binding between the magnetic particles, the adhesion force of the magnetic particles and the workpiece was large, the polishing force was greatly shown.

As the blending ratio of the abrasive grains increases, the abrasive grains act as impurities in the magnetic particle chain, thereby decreasing the binding force. However, as the number of abrasive grains acting on the workpiece increases, the number of abrasive grains pressed into the workpiece increases, thereby increasing the polishing force. As a result, the polishing rate of 50% of the compounding ratio was higher than that of the blending rate of 40% .As the compounding rate of 57%, the bonding force of the magnetic particles was lower than that of the abrasive grains. This became small.

Therefore, the best polishing conditions were found to be optimal when the ratio of abrasive grains to magnetic particles was about 45-55wt%.

(Example 2)

FIG. 5 shows magnetic flux density of 0.2, 0.6 Tesla, abrasive grain size # 320, abrasive grain mixing ratio 1: 1 for magnetic particles, polishing speed is 1350rpm, polishing time which is considered to be the optimum polishing condition for polishing cemented carbide using GC particles. Is 60 minutes, and the surface roughness according to the polishing time is shown. As shown in FIGS. 5A and 5B, the surface roughness was not improved to Rmax of 0.2 μm or less even after polishing 60 minutes with GC particles, which is economical by improving the surface roughness by self-polishing cemented carbide with GC particles. Indicates that there is no.

(Example 3)

The same conditions as in Example 2 were carried out except that the abrasive particles were diamond particles.

Figure 6a is the magnetic flux density of 0.2, 0.6 Tesla, abrasive grain size # 1500, # 3000, abrasive grain mixing ratio for magnetic particles 1: 1, polishing rate is 1350rpm, polishing time is 60 minutes, the polishing surface roughness according to the polishing time The figure shown. As shown in FIG. 6A, when the magnetic flux density is 0.6 Tesla, the polishing surface roughness was greatly improved, which shows the same tendency as the GC particles used in Example 2.

FIG. 6B is a view showing the roughness of the polishing surface according to the size of the abrasive grains, showing the results of polishing with abrasive grain size # 800, # 1500, # 3000, # 8000. In the case of GC particles, the degree of improvement of the polished surface roughness was different according to the particle size, but in the case of polished with diamond particles, the variation of the polished surface roughness according to the particle size was small. This is because the hardness of the diamond particles and the particle size is more than # 800, the number of particles acting on the workpiece is more than a certain size, so that when the particle size is more than # 800, the change in the roughness of the polishing surface according to the particle size is small.

FIG. 6C is a graph showing the results of polishing at 450, 750, 1050, 1350, 1650 rpm, magnetic flux density 0.6T, abrasive grain compounding ratio 1: 1 for magnetic particles, and abrasive grain size # 800. As shown, the surface roughness was the best when the polishing speed was 1050, 1650rpm. The lower the polishing speed, the greater the grinding force, but the smaller the rotational speed of the workpiece. This result is shown by the correlation of the amount of rotation of the polishing force with the polishing rate.

7a and 7b are photographs of the surface of the cemented carbide solid rod self-polishing using the GC particles and diamond particles, 1 using diamond particles compared to the photograph 7a of the polishing surface self-polishing for 7.5 hours using the GC particles 1 The photographic surface 7b of the self-polished polishing surface for a time was very smooth and the polishing surface roughness was also very good.

As described in each of the above-described embodiments, the most suitable polishing conditions for the cemented carbide use abrasive grains as diamond particles, but the mixing ratio of the abrasive grains to the magnetic particles is 45-55wt%, particle size # 300 or more is most suitable. .

In addition, the magnetic flux density of 0.2 ~ 0.6 Tesla, polishing rate of 450 ~ 1650rpm is most suitable.

As described above, in the present invention, diamond particles are used as the abrasive particles to grind the cemented carbide parts among the components requiring high precision, but the size of the diamond particles and the combination of the abrasive particles and the magnetic particles are used. It provides the most suitable self-polishing method for polishing cemented carbides such as ratio.

Claims (2)

In a magnetic polishing method in which a magnetic polishing material comprising a magnetic material and abrasive grains as components is polished while pressing a workpiece by magnetic force, the magnetic polishing material arranged linearly along a magnetic force line, The workpiece is a cemented carbide, and the abrasive grains for polishing the workpieces use diamond particles, the particle size of which is more than # 300, and the proportion of the abrasive grains to the magnetic particles is 45 to 55 wt%. Cemented carbide self polishing method The method of claim 1, Carbide carbide polishing method using diamond particles characterized in that the magnetic flux density is 0.2 ~ 0.6 Tesla and the polishing speed is between 450 ~ 1650rpm

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