SU1364454A1 - Method of producing abrasive articles - Google Patents

Abstract

This invention relates to the manufacture of an abrasive tool. The purpose of the invention is to improve the quality of the abrasive article. The shaping of the abrasive tool is carried out in two stages, the first of which involves static pressing to ensure a density of 0.6-0.7 of the density of the finished product. In the second stage, the resulting billet is subjected to a shock wave with a power of 0.75-1.00 MW / g of powder, and the heat treatment is carried out at a temperature of 1800-1850 ° C for 2-4 hours. The second stage is repeated 5-7 time. Dynamic loading can be carried out by an electro-hydraulic shock wave. 1 hp f-ly, 3 tab. (ABOUT

Description

with

Oi 4 4

cm

The invention relates to the manufacture of an abrasive tool, preferably for finishing difficult-to-machine materials.

The purpose of the invention is to increase the quality of the abrasive product.

A method of making abrasive products includes preparing a mixture of ceramic materials, for example, electrocorundum, and subsequent two-stage pressing of the workpiece by static pressing to a density of 0.6-0.7 of the density of the finished product and subsequent dynamic loading of the workpiece with a shock wave of 0.75-1.00 MW / g of the weight of the ceramic material (electrocorundum powder). The process of making an abrasive product is completed by heat treatment of it at 1800-1850 ° C for 2-4 hours. Dynamic loading is repeated 5-7 times using an electro-hydraulic shock.

Shaping from the batch of products in two stages allows to obtain a more ordered structure of the abrasive product. The static pressing carried out in the first stage makes it possible to improve the conditions for the passage of the shock wave in the medium, since the velocity of propagation of the shock wave (sound velocity) is directly proportional to the density of the medium. When the charge is dynamically loaded with an electrohydraulic shock wave at the second stage of formation, the density of the abrasive article is further increased, and, in addition, the process of plastic deformation of the charge grains begins and, as a result, the contact surfaces of the grains arise and develop intensively. The formation of developed contact surfaces is explained by the mechanical connection of individual charge grains and the initiation of the surface diffusion process, when the mutual attraction of individual grains is due to atomic bonds. When the dynamic loading is repeated several times, the sizes of the grains in the abrasive article redistribute. The size distribution of the grains is approaching a uniform, the grains take on a needle-like shape. Such a form of cutting grains of an abrasive article is most preferable for finishing because of the cutting and developed cutting surface of the grains. During the subsequent heat treatment, diffusion along the contact surfaces of the grains proceeds more intensely, at the points of contact of individual grains, necks form, which grow until the residual stresses resulting from dynamic loading during the formation of the charge disappear.

Under dynamic loading with an electrohydraulic shock wave, the specific power less than 0.75 MW / g of weight is prepared0

0 g / j 5 0 5

However, with a number of loading cycles of less than 5, the compact is loose, with a large number of surface and bulk defects, and in some cases is scattered into powder. The size of the grains obtained under these conditions of compacts lies within 0.67-0.82 of the grain size of the original ceramic powder, the relative porosity is within 10-14.5% by volume and the shape of the grains is close to a ball (the isometric coefficient is within 0 , 76-0.66). The use of such a tool in metalworking does not provide a gain compared with the tool used in industry, and in some cases known technical solutions provide the best results.

When a compact is loaded with an electrohydraulic shock wave of a specific power of more than 1.00 MW / g of the weight of the prepared mixture with more than 7 cycles, the compact is too dense, with a small number of pores, the grain of such a tool is 28-30% less than the grain of the original ceramic powder. Due to the intensive crushing of the grains, their shape is close to spherical, which reduces the efficiency of metal processing. Abrasive products made in this way do not provide high processing performance.

Testing of the abrasive product obtained by the proposed method is carried out when machining steel 40X in the state of normalization (HB 229) by electrochemical grinding with a remote cathode tool. When processing, an electrolyte of composition is used, wt%: .NaNOa 20%; NaNO2 0.2; H2O 79.8. Electrochemical grinding provides the following processing modes for the processing: process current density 5.0 operating voltage 12 V; rotational speed of the grinding wheel 20 m / s; the speed of rotation of the part is 50 m / min; longitudinal feed 5.0 m / min; transverse, circle feed 12 µm / dx.

Example 1. For the manufacture of an abrasive article, a mixture is prepared from electrocorundum powder of a single grain size, for example, 250 microns (from 200 to 250 microns according to GOST 3647-80). Pour the prepared mixture into the mold and carry out static pressing for 30 seconds. The density of the compact is 0.6 of the density of the finished product. Then, not removing the static load, dynamic loading of the prepared charge with an electrohydraulic shock wave of a specific power of 0.75 MW / g is carried out. Dynamic loading is repeated 5 times at constant power. The compact is then removed from the mold and fed to a heat treatment furnace. Pressing has minor chips on sharp edges. Heat treatment is carried out at 1800 ° C for 2 hours.

The obtained abrasive product has a compressive strength of 50 MPa; when tested by the method of electrochemical grinding, the specified abrasive product allows to achieve processing performance in the described modes up to 1100 mm / min. Abrasive wear 16. The abrasive article obtained in this way can be used for finishing. Processing performance

The density of the compact is 0.3 percent of the density of the finished product. Then, not removing the static load, a single dynamic loading with an electrohydraulic shock wave of a specific mosh.nosti 0.70 MW / g of the weight of the prepared mixture. The resulting compact is removed from the mold. Further processing of the abrasive product is impractical because the pressing does not hold the shape. Obtained by

when using the described abrasive 0 described modes, the product applied to the product in comparison with the known composition-finishing can not be.

It is 102%, tool wear is reduced by 1.31 times.

Example 2. The mixture prepared as in Example 5. The mixture prepared according to Example I was poured into a mold and static pressing was carried out for 60 seconds.

measure 1, poured into the mold and carried out. The density of pressing is 0.7 of the density compaction within 40 s. of the finished product. Then, do not remove the compactness density is 0.64 of the density of the finished product. Then, not removing the static load, the electrohydraulic

the shock wave of the specific mosh.nost 20 loading is repeated 8 times with an unchanged level of 0.87 MW / g of the weight of the prepared mixture. Di st oh mosh Then the pressing is extracted; the loading is repeated 6 times from the mold and fed to the furnace.

unchanged mosh, nosti. Then pressing due to heat treatment. Pressing pulls well out of the mold and feeds into the mold, chips and visible trash not

for heat treatment. Pressing has no has. Thermal treatment is carried out

static load, dynamic loading of electro-hydraulic shock wave of specific power of 1.05 MW / g of weight of the prepared shear is carried out. Dynamic appointing single chips on sharp edges. Heat treatment is carried out at 1825 ° C for 3 hours. The resulting abrasive article has a compressive strength of 55 MPa, when tested by the method

at 1900 ° C for 5 hours. The resulting abrasive article is not suitable for use in metalworking, since it is partially melted during heat treatment and does not remain on the surface.

electrochemical grinding achieves-ZO rezhush, their grains.

The processing performance is similar to the described examples of wires 1150, which is 2.3 times higher than the performance of the known. The wear of the abrasive product 14, which is 1.8 times lower than the known wear.

Example 3. A mixture prepared by loading, with a temperature of measure 1, is poured into a mold and by wire heat treatment.

d t experiments on the manufacture of abrasive products with different durations of static pressing, the number of cycles and the specific power of the dynamic

d t static pressing for 50 s. The density of the compact is 0.7 of the density of the finished product. Then, not removing the static load, the electro-hydraulic shock wave of a specific power of 1.00 MW / g of the weight of the prepared mixture is dynamically loaded. Dynamic loading is repeated 7 times at constant power. The compact is then removed from the mold and fed to a heat treatment furnace. Pressing holds its shape well, has no chipping and visible cracks. Thermal treatment is carried out at 1850 ° C for 4 hours. The resulting abrasive product has a compressive strength of 60 MPa, and when tested by the method of electrochemical grinding, processing performance of 1200 is achieved, which is 2.4 higher than with the use of the known. Wear the product 14, which is 1.8 times lower than when using a known tool.

Example 4. The mixture prepared according to Example 1 was poured into a mold and static pressing was carried out for 20 seconds.

The density of the compact is 0.3 percent of the density of the finished product. Then, not removing the static load, a single dynamic loading with an electrohydraulic shock wave of a specific mosh.nosti 0.70 MW / g of the weight of the prepared mixture. The resulting compact is removed from the mold. Further processing of the abrasive product is impractical because the pressing does not hold the shape. Obtained by

In the described modes, the product cannot be used for finishing.

The density of the compact is 0.7 of the density of the finished product. Then don't take off

the loading is repeated 8 times with the same mosh. Then, the pressing is removed by static load; the electrohydraulic shock wave is loaded dynamically with a specific power of 1.05 MW / g of the weight of the prepared shear. Dynamic has Thermal treatment is carried out

at 1900 ° C for 5 hours. The resulting abrasive article is not suitable for use in metalworking, since it is partially melted during heat treatment and does not remain on the surface.

loading, heat treatment temperature.

d t experiments on the manufacture of abrasive products with different durations of static pressing, the number of cycles and the specific power of the dynamic

0

five

In tab. 1 shows the results of experiments to determine the interval of static pressing.

As follows from the table. 1, the optimum static pressing time is in the range of 30-50 seconds. With static pressing for less than 30 seconds, the density of the compact is 0.3 of the density of the finished product, and in the pressed mixture no conditions are created that are sufficient for subsequent dynamic loading. The relative porosity of the mixture in the mold is 16% by volume, which is close to the bulk density of the ceramic powder. As you know, the speed of sound in the powder is small and the impact, - on the wave fades, not having time to go through the pressed material. With static pressing for more than 50 seconds, the pressing density is 0.7 of the density of the finished product and is a constant value, independent of the pressing time. 5 Since the increase in the time of static pressing for more than 50 s does not give a gain in the quality of pressing, it is impractical to increase the time of static pressing

0

above the interval of 30-50 s (compacting density 0.6-0.7 of the density of the finished product).

In tab. 2 summarizes the results of experiments to determine the range of optimal dynamic loading modes of the pressed abrasive article.

As follows from the table. 2, the optimum specific power of dynamic loading is within 0.75 - 1.00 MW / g of the weight of the prepared mixture, and the optimal number of loading cycles is 5-7.

When the electrohydraulic shock wave is loaded dynamically, the specific power density is less than 0.75 MW / g of the weight of the prepared mixture with the number of loading cycles of less than 5, the compact is loose, with a large number of surface and bulk defects, and in some cases is dispersed into powder. The size of the grains obtained under these conditions of compacts lies within 0.67–0.82 of the grain size of the source material, the relative porosity is within 10–14% by volume, and the grain shape is close to a ball (the isometry coefficient is 0.76 -0.66).

. When the compact is loaded with an electrohydraulic shock wave of a specific power of more than 1.00 MW / g of the weight of the prepared mixture with the number of loading cycles of more than 7, the compact is too thick, with a small number of pores, the grain of such a tool is 28-30% less than the grain of the original ceramic powder. Due to the intense crushing of the grains, their shape approaches spherical, which reduces the efficiency of metal processing by such a tool. Abrasive products made by the above method do not provide high processing performance, the durability of the described abrasive products is higher than that of the known 70-90%.

0

0

five

0

five

0

In tab. 3 shows the results of determining the optimal heat treatment conditions.

From tab. 3 shows that heat treatment should be carried out at 1800-1850 ° C for 2-4 hours

With a baking temperature of less than 1,800 ° C and a heat treatment time of less than 2 hours, the abrasive products have low strength and, as a result, are unsuitable for use in metal processing.

At a sintering temperature of more than 1850 ° C, the probability of melting of the abrasive article increases, as the temperature becomes close to the melting point of the original ceramic powder. As the heat treatment increases over 4 hours, the likelihood of the abrasive product melting also increases. In addition, with an increase in heat treatment time of more than 4 hours, the volumetric porosity of abrasive products decreases dramatically due to "shrinkage, which can reach 7-12%.

Claims (2)

1. A method of manufacturing abrasive products, in which, when shaping a billet onto electrocorundum powder, dynamic loading with a shock wave is exhibited, after which the billet is subjected to heat treatment, characterized in that, in order to improve the quality of the product, firstly electrocorundum powder is formed to static density to 0 , 6-0.7 of the density of the finished product, the power of the shock wave is 0.75-1.00 MW / g of powder, and the heat treatment is carried out at 1800- 1850 ° C for 2-4 hours, while the effect is Darnay wave repeated 5-7 times at a constant its capacity. 2. A method according to claim 1, characterized in that the dynamic loading is provided by an electro-hydraulic shock wave. powder for 30- for 10- for 4- for 4- 50 hours- 13 hours-8 hours- 8 parts tei tei 0.96 0.87 0.85 0.83 0.83 16 15.2 15.0 14.8 14.8 0.3 0.6 0.64 0.7 0.7 Table S about. X sa a CZECH f so about O. nj (U b and a "o , Well and and J3 o l s e-ex t-ш о о 1О о н с н о to about about z: f- 2 ü about C) o. S vs: :: g S o o