SU975379A2 - Method of producing abrasive articles - Google Patents

Description

The invention relates to the manufacture of an abrasive tool. According to the main author. St. V is a known method for the manufacture of abrasive products, in which a mixture of ceramic powder materials is prepared and the formation of a mixture of products by an explosive shock wave followed by heat treatment. A mixture of electrocorundum powders with the ratio of the main fraction (500-1000 µm) and additional (less than 500 to 180 µm) from 60 to kQ% is taken as the charge and the powder of the blowing agent in the amount of the volume of the additional fraction of electrocorundum the shock wave of a mixture of powders of electrocorundum, obtained by an industrial method and having a significant number of microcracks and lattice defects, leads to a large crushability of electrocorundum grains, some of which lose their cutting th because of the small capacity, causing quality sharply deteriorates abrasive articles. The purpose of the invention is to increase the abrasive ability of the products. This goal is achieved by the addition of copper powder with a dispersity of 1.0 to the mixture of ceramic flux materials. 10.0 microns in an amount of 10-25 with respect to the volume of the charge, after which the mixture is annealed at 800-950 ° C for 2 hours, followed by the introduction of a blowing agent by known methods. The uniform distribution of copper by the charge volume allows, in the process of annealing at 800-950 ° C for 2 hours, to make a firm setting (welding) over the contact surfaces of copper

with grains of electrocorundum, i.e. how to surround the electrocorundum grains with a thin copper sheath, which, upon subsequent pressing with a shock wave, reduces to a large extent the crushability of the electrocorundum grains, retaining small particles of the grains during their plastic deformation; obtained by an industrial method and therefore containing a significant number of microcracks, alternating internal stresses, which, when pressed by a shock wave, leads to a significant crushing of grains and the appearance of grains, due to their smallness, cutting of internal stresses and healing of microcracks occur, leading to an increase in plastic properties of grains of electrocorundum, and, consequently, to a decrease in the degree of crushing during pressing by a shock wave, which is why the quality of abrasive products made by the proposed method, improves. In addition, the introduction of copper powder into the mixture makes it possible to make the finished abrasive product conductive and it can be used for electrochemical grinding, a wire processing process without additional cathode devices.

The choice of the volume ratio of the mixture and copper powder 10–25 is due to the presence of an optimal contact surface, which is used to weld the electrocorundum and copper grains during annealing.

The sizes of the copper powder grains were chosen to obtain a strong joint between the copper and the electrocorundum grains along the microroil contact surfaces during the annealing process, and in order to obtain a homogeneous porous conductive body during the subsequent sintering.

J The proposed method of making abrasive products is as follows.

A mixture of ceramic powder materials is prepared, which includes grains of the electrocorundum main fraction (500–1000 µm) and an additional (500–180 µm) with the ratio of the main fraction to the additional one. Copper powder is introduced into the mixture;

thoroughly mixed and annealed.

A pore-forming agent is then introduced into the mixture and the whole mixture is compacted according to the ampoule circuit by a shock wave arising from an explosive charge with a thickness of 70-110 mm of the ammonite explosive, which is covered with the ampoule with the mixture and which provides a pressure of 600-900 kbar. Thermal treatment - sintering (13001800 ° C) for 2-8 hours ensures the formation of pores of the optimal size and quantity by sublimation of the coater.

Testing of the abrasive product obtained by the proposed method was carried out during the processing of steel ZZHMUA method of electrochemical grinding. When processing, an electrolyte of the following composition was used,%: Sodium nitrate 15 Sodium nitrate 0 2

5 WaterElite

Electrochemical grinding was carried out at a technological current density of 100-130 A / cm, voltage

0 6-12 V, longitudinal feed of 2.0 m / min, transverse feed of 0.002-0.005 mm / per turn, at a speed of rotation of a circle of 30 m / s, a speed of rotation of a part of 7.5 m / min, the electrolyte consumption was 5 liters / min

Example 1 For the manufacture of an abrasive article, a powder of pure copper with a grain size of 1.0 µm is added to the mixture of grains of electrocorundum.

an amount of 10 of the batch volume, annealing at 800 ° C for 2.0 hours, then a pore former is added and compression is carried out by a shock wave generated by the explosion of an explosive charge, which is enclosed in an ampoule with copper and blowing agent. The obtained abrasive product is subjected to sintering. The number of grains not participating in the cutting of the NPI (size 1 micron or less) reaches 8 to the product volume, the number of microcracks on the thin section of the grain (in to the total grain area trapped in the section of the thin section) is 15%, the welding strength of copper and electrocorundum after annealing 12 kgf / mm, the abrasive product has a uniform electrical conductivity throughout the volume.

Example 2. For the manufacture of an abrasive article, a powder of pure copper with a grain size of 10 µm was added to the mixture of electrocorundum grains in an amount of 25 by volume of the mixture, produced at 950 ° C for an hour, then a blowing agent was added and the shock wave formed during the explosion of the explosive charge, which is enclosed in an ampoule with the electrocorundum grains, copper and a blowing agent entering into it. The obtained abrasive product is subjected to sintering. The number of grains that are not involved in cutting (1 μm or less in size) reaches 2.01 by the volume of the product, the number of microcracks on the thin section of the grain (in to the total grain area trapped in the section of the thin section) is 4.0, the welding strength of copper and electrocorundum after annealing, it reaches 17 kgf / mm, the abrasive product has a uniform electrical conductivity but throughout the volume.

Similarly to the examples described, experiments were carried out with different initial fractions and the ratio of copper and grains of electrocorundum in different modes of annealing.

The results of the experiments are presented in the table.

As follows from the table, the optimal amount of copper powder by volume of grains of electrocorundum is 10–251, and its dimensions are 1.0–10 µm. In addition, the optimal modes of annealing are 800–950 ° C with a duration of 2 m. The number of grains not participating in the cutting due to smallness (1 µm or less) reaches 2–8, the number of microcracks on the thin section of the grain (in the total area of the grain trapped in the section of the thin section is 4-15%, the welding strength of 1 unit and electrocorundum is 12-17 kgf / mm, the product is electrically conductive throughout the volume evenly.

As follows from the table, the size of copper powder to 1.0 μm, the amount of its less than 101 relative to volume

grains of electrocorundum, annealing the mixture at temperatures up to 800 ° C for a duration of less than 2.0 hours does not lead to an improvement in the quality of the abrasive product, since the number of grains is large,

5 participating in the cutting (size 1 micron or less), there is no healing of microcracks in the grains of the electrocorundum obtained industrially, we have low strength welding of copper and electrocorundum, the entire volume of the abrasive product is electrically conductive in sections unevenly by volume.

With an increase in the granularity of copper powder over 10 µm and its amount over 25 relative to the volume of grains of electrocorundum upon annealing at 1000 ° C for 4.5 hours, the quality of the abrasive product deteriorates as the annealing temperature becomes very close to the melting point of copper, and it, beginning to be very strongly softened and even partially melted, ceases to be evenly distributed in volume, accumulating on one side of the compact (below), the strength of the combination of copper and electrocorundum decreases.

Claims (1)

The technical and economic efficiency of the invention is expressed in increasing the productivity of the treatment. The invention The method of manufacturing abrasive products according to ed. St. No. characterized in that, in order to increase the abrasive ability of the products, copper powder with dispersion of 1.0-10 microns in an amount of 10-25% by volume of the charge is added to the mixture, after which the mixture is annealed at 800-950 ° C within 2-4 hours. Sources of information taken into account during the examination 1. USSR author's certificate V 67341 6, cl. B 24 O 17/00, 1977.