RU2621204C2 - Method of producing metallic powder with mechanical treatment of cylindrical billet - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes placing the billet coaxially with one of the abrasive heads fixed in the housing of the grinding disc, bringing the billet into rotation and grinding it to obtain a metal powder by abrading a rotating grinding disc. The grinding of the billet is carried out with the supply of liquid nitrogen to the treatment zone, the mode of which is determined from the predetermined ratio, depending on the tensile strength of the grinding billet material.

EFFECT: reducing the spread of the average size of the resulting particles, producing the particles less than 5 mcm, reducing metal losses.

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Description

The invention relates to the field of metallurgy, and in particular to the production of metal powders by abrasion with an abrasive tool.

Existing methods for producing powders are divided into mechanical and physicochemical (Technology of metals and materials science. / Under the editorship of LF Usova. - M .: Metallurgy, 1987, p. 121).

Of the mechanical methods currently used, such as spraying a jet of molten metal (RF patent 2199734, IPC G01N 7/48, 02/27/2003) and metal cutting by producing particles, rather than drain chips.

The disadvantage of the method of spraying the melt is the high energy consumption for heating and melting the metal, as well as the need to create a protective atmosphere for the melt.

For the production of powders, various methods of grinding metals by cutting are also carried out using mills and crushers (Gert Schubert "Aufbereitung metallischer Sekundarrohstoffe", VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1984).

A known method in which the production of metal powder is carried out by milling the workpiece (patent RU No. 2203773, IPC B23C 3/04, 2003).

As the closest analogue of the invention, a method for producing a metal powder by machining a workpiece disclosed in patent RU 146455 U1, B22F / 04, 10.10.2014, in which a method for producing metal powders from a cylindrical workpiece comprises placing the workpiece coaxially with one of the abrasive heads, can be adopted. fixed in the housing of the grinding disk, bringing into rotation the aforementioned workpiece and its grinding to obtain a metal powder by abrasion by a rotating grinding disk.

The disadvantages of the known methods are the large variation in the size of the resulting particles, the inability to obtain particles of the same size and to obtain particles less than 100 microns due to the high temperatures associated with the need to increase the processing speed, which increases the fire hazard. In addition, when using this method, the cylindrical metal residue after milling is 1-1.5%.

The technical result of the invention is to reduce the dispersion of the average size of the obtained particles and to ensure the possibility of obtaining particles less than 5 microns, as well as reducing metal loss.

The specified technical result is achieved by the fact that in the method of producing a metal powder by machining a cylindrical workpiece comprising placing the workpiece coaxially with one of the abrasive heads fixed in the housing of the grinding disk, bringing the said workpiece into rotation and grinding it to obtain metal powder by abrasion by a rotating grinding disk, according to the claimed technical solution, the grinding of the preform is carried out with the supply of liquid nitrogen to the treatment zone, the mode of which is determined from relationship

,

,

where a is the average size obtained from the workpiece particles, microns;

V is the rotation speed of the grinding disk, m / s;

S is the feed rate of the grinding disc, mm / min;

k is a correction factor selected from the range 1300-195000 depending on the tensile strength of the material of the crushed billet (σ _in , MPa), the lower value of which from this range corresponds to the material with the highest tensile strength.

In FIG. 1 shows a diagram of the mutual arrangement of the workpiece and the grinding disk.

In FIG. 2 is a view along arrow A in FIG. one.

The specific value of the coefficient k is determined from the graph (Fig. 3), the values of which were obtained experimentally.

The method is as follows: depending on the required size of the obtained particles, the required feed rate of the grinding disk (S) is determined from the ratio

, (1)

, (one)

where a is the average size obtained from the workpiece particles, microns;

V is the rotation speed of the grinding disk, (selected in the range from 200 to 300), m / s;

It was experimentally established that at a speed of the grinding disk V <200 m / s, the average size of the obtained powder varies in the range from 5 μm to 10 μm, and at a speed of rotation of the grinding disk V> 300 m / s there is a danger of rupture of the grinding disk.

S is the feed rate of the grinding disc, mm / min;

k is the correction factor, depending on the tensile strength (σ _in , MPa) of the material of the crushed workpiece.

It was experimentally established that the coefficient k varies from 1300 to 195000, and a smaller value of the coefficient k of this range corresponds to the material with the highest tensile strength.

The blank 1 is fixed in the clamping device 2 coaxially to one of the abrasive heads 3. The abrasive heads are fixed on the grinding disk 4. The clamping device 2 is located on the machine bed (not shown in the drawing). The mechanical method for producing metal powders is that the workpiece 1 is rotated, then the grinding disk 4 is rotated by means of a drive mounted on a carriage located on the machine plate with the possibility of reciprocating movement. After the grinding disk 4 reaches a predetermined rotation speed, the preform 1 is cooled with liquid nitrogen, which is supplied from the cryogenic reservoir through the thermal hose continuously during the entire abrasion process.

The grinding disk 4 is fed to the workpiece 1 with a calculated feed (S) until contact with the workpiece 1 is fixed in the clamping device coaxially with one of the abrasive heads 2, resulting in grinding of the workpiece 1 by abrasion.

To unload the powder from the grinding chamber, a particle capture device, for example a blower, is used, connected to a device for collecting crushed material. After abrasion of the workpiece, the device is turned off and the ground material is removed from the collection device. The cycle repeats.

Consider an example of calculating the feed rate of the grinding disk according to the mathematical formula (1) with the dimensions of the variables included in it. To obtain a metal powder with a size from 0.7 μm to 3 μm, a cylindrical rod of a neodymium magnet (tensile strength σ = 80 MPa) with a length of 100 mm was used as the initial workpiece. By the formula (1), the necessary feed rate of the grinding disk (S) was determined. Then the workpiece was fixed in the clamping device coaxially with one of the abrasive heads. Since the task is to obtain an average powder size in the range from 0.7 μm to 3 μm, it is advisable to take a grinding disc speed of 300 m / s. From the graph of FIG. 3, obtained experimentally, we select the correction factor k corresponding to σ _{in the} processed material. For a neodymium magnet, the correction factor is k = 48752.84.

выразим подачу мелющего диска

, From the formula

express the feed of the grinding disc

,

where a is the average size obtained from the workpiece particles, microns;

V is the rotation speed of the grinding disc 300 m / s;

S is the feed rate of the grinding disc, was 0.62 mm / min.

k is a correction factor selected from the range 1300-195000 depending on the tensile strength of the material of the crushed billet (σ _in , MPa), the lower value of which from this range corresponds to the material with the highest tensile strength.

Calculations show that the dimensions of the left and right parts of the mathematical expression are 0.62 mm / min = 0.62 mm / min.

In the process of obtaining the powder, a grinding disk with built-in grinding heads with a diameter of 16 mm was used.

After the grinding disk reaches the set rotation speed, the workpiece is cooled with liquid nitrogen, which is supplied from the cryogenic reservoir through the thermal hose continuously during the entire abrasion process.

The grinding disk is fed to the workpiece until contact is made with the workpiece fixed in the clamping device coaxially with one of the abrasive heads, resulting in grinding of the workpiece by abrasion. The powder formed during abrasion was absorbed through a special air mechanism into the assembly chamber. The cylindrical residue of the preform after abrasion was 1.5 mm, which corresponds to ~ 1-1.5% of the total length of the preform. To unload the powder from the grinding chamber, a particle capture device, for example a blower, is used, connected to a device for collecting crushed material. After abrasion of the workpiece, the device is turned off and the ground material is removed from the collection device. The yield of finished powder was ~ 98.5-99.0% of the total length of the workpiece. The resulting powder had an average particle size of from 0.7 μm to 3 μm. The cycle repeats.

The inventive method is shown by the example of obtaining powder from a neodymium magnet. However, this does not limit its scope. The method can be used to obtain powders of any solid materials.

The preparation of the preform powder was carried out according to the scheme shown in FIG. one.

The inventive method provides waste-free processing of the workpiece, reducing the size dispersion of the resulting particles and making it possible to obtain particles of less than 5 μm, and the addition of liquid nitrogen reduces the likelihood of high temperatures arising from abrasion at high speeds, therefore, there is no possibility of fire hazard in the process. It was experimentally shown that the inventive method allowed to obtain particles of the same size and obtain particles less than 5 microns.

Claims (6)

A method of producing a metal powder by machining a cylindrical workpiece, including placing the workpiece coaxially with one of the abrasive heads fixed in the grinding disc body, rotating said workpiece and grinding it to produce metal powder by abrasion by a rotating grinding disk, characterized in that the workpiece is ground with the supply of liquid nitrogen to the treatment zone, the mode of which is determined from the ratio

, where a is the average size obtained from the workpiece of the powder particles, microns; V is the rotation speed of the grinding disk, m / s; S is the feed rate of the grinding disc, mm / min; k is a correction factor selected from the range 1300-195000 depending on the tensile strength of the material of the crushed workpiece (σ _in , MPa), the lower value of which from this range corresponds to the material with the highest tensile strength.

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