RU2307859C2 - Binder for producing abrasive parts and tools (variants) - Google Patents

Abstract

FIELD: binders used for making abrasive parts and tools.

SUBSTANCE: binder is formed during process of treating hydrocarbon gas in pyrolysis condition inside pores of blank of abrasive product. Binder contains, mass%: technical carbon, 0.01 - 3 %; pyrocarbon or pyrocarbon with fibrous carbon, the balance. Hydrocarbon gas may contain in addition 0.15 vol% of acetylene.

EFFECT: possibility for using abrasive product with such binder for highly effective cutting of hard alloy without dressing of tool.

3 cl, 1 tbl, 3 ex

Description

The invention relates to the production of abrasive elements and tools on organic binders, including from powders of superhard materials.

Currently, the largest volume of abrasive tools on organic binders is made from binders based on phenol-formaldehyde and polyamide resins. These products have a relatively low level of operational properties (dimensional stability, grinding coefficient) caused by low values of heat resistance, chemical resistance and thermal conductivity of these binders, their high coefficients of linear thermal expansion.

Significantly higher performance properties have abrasive products on the binder (options) described in the patent of the Russian Federation [1], which is two combinations of solid pyrolysis products of carbon-containing gases (wt.%):

- fibrous carbon - 0.1-99.5; pyrocarbon - rest; -fibrous carbon - 0.1-99.51, pyrocarbon and diamond - the rest.

A binder is formed as a result of heat treatment of a "raw" porous workpiece of an abrasive tool in a carbon-containing gas environment. During this treatment, solid products of carbon-containing gas pyrolysis (binder) are deposited in the pore structure of the abrasive tool blank (in its volume), which solidly consolidate the powdery ingredients of the abrasive product formulations. This invention is selected as an analogue.

During the operation of any abrasive tool, blunting of abrasive grains occurs. At the same time, due to an increase in the load on dull grains, their removal (tearing) out of the working layer should occur. At the same time, the abrasive tool continues to work with the previous productivity (self-sharpening mode). If the abrasive grains are held by the binder very firmly (high adhesion) and it has high mechanical strength, then there is a gradual increase in cutting forces, a decrease in grinding performance.

The formation of carbon black is known to be a voluminous process. If we take into account that the specific surface area of the abrasive product subjected to saturation is rather high, then during the pyrolysis of pure natural gas in the pore structure of the product, the formation of carbon black (soot) is unlikely [2]. It was shown in [4] that, during the thermal decomposition of acetylene, the growth rate of pyrocarbon on the surface is much lower than the growth rate of carbon black. Therefore, if acetylene is added to natural gas at a concentration of 0.1-0.3 vol.% [3], carbon black in the form of separate microparticles begins to be emitted in the pore structure simultaneously with pyrocarbon. This observation is proposed to be used in the present invention for introducing carbon black into a binder. Its amount in the binder, necessary to interrupt the growth of pyrocarbon and reduce its adhesion to abrasive grains, is from 0.01 to 3 wt.%. With more carbon black, the density of the binder decreases and the grinding coefficient decreases significantly. The operation of introducing carbon black into the binder is proposed to be carried out in two stages: at the beginning of the saturation process and in its middle. After each stage of the introduction of carbon black, thermal oxidative degradation of carbon black, pyrocarbon and fibrous carbon on the surface of abrasive products should be carried out. At the same time, the places (pores) of gas entry into the product volume are “opened”. Thermo-oxidative degradation is realized by supplying carbon dioxide, water vapor, etc. to the reactor. Further improvement of this type of binders was carried out in the RF application [5]. It describes two options for binders:

- pure pyrocarbon; - epitaxial diamond - 0.1-60 wt.%; pyrocarbon - the rest.

At the same time, the disadvantages associated with the negative consequences of introducing the formation of fibrous carbon (diamond graphitization) into the circles of metal catalysts were eliminated and the completeness of filling the pore structure of abrasive products with carbon-based gas pyrolysis products was increased. This invention is selected as a prototype: a binder for the manufacture of abrasive elements and tools based on the products of pyrolysis of carbon-containing gases.

During the pyrolysis of carbon-containing gases, the formation of the following products is possible: carbon black (soot), pyrocarbon, fibrous carbon, epitaxial diamond.

The binders described in the prototype contain either pure pyrocarbon or pyrocarbon mixed with epitaxial diamond. Pyrocarbon is deposited in the pore structure of raw abrasive products in the form of "microcones" starting from the initial surface and oriented normally to the growth surface. The material is highly textured and anisotropic [2]. Given the high adhesion of pyrocarbon to the surfaces of abrasive materials, the binder firmly holds abrasive grains and does not allow them to be removed when the cutting edges are dull. An additional resistance to the removal of grains is provided by the powdered components of the fillers, “impregnated” with strong binders (both in the analogue and in the prototype).

If microparticles of isometric shape can be delivered to the growth zone of pyrocarbon during saturation, then, being included in the growing structure of pyrocarbon, they will be the growth sites of new “microcones” of pyrocarbon and will reduce the contact surface of pyrocarbon with abrasive grains (reduce adhesion). In this way, the retention strength of the abrasive grains can be controlled in a controlled manner. Additionally, the resulting "bimodal" structure leads to high isotropic properties of the binder. The role of a "breaker" of pyrocarbon growth can be performed by carbon black (soot) under certain technological conditions of the saturation process. To qualitatively and quantitatively evaluate the composition of the proposed binder, experiments were conducted on model formulations of abrasive products.

The objective of the present invention was to increase during operation of abrasive products grinding performance inherent in the initial period of operation, the technical result being the optimization of the structure, mechanical properties of the binder and its adhesion to abrasive grains.

For this, a binder based on a mixture of products of pyrolysis of carbon-containing gases contains, wt.%:

- carbon black - 0.01-3%, pyrocarbon - the rest;

- carbon black - 0.01-3%, pyrocarbon and fibrous carbon - the rest;

- carbon black - 0.01-3%, pyrocarbon, fibrous carbon and diamond - the rest;

- carbon black - 0.01-3%, pyrocarbon and diamond - the rest.

The components of the binder can be doped with boron, silicon, titanium and other chemical elements and compounds, or mixtures thereof.

As shown by the results of long-term operation of a diamond tool (according to the prototype), a steady, very undesirable decrease in grinding performance depending on the operating time is observed when cutting a hard alloy. With abrasive treatment of other, harder materials, an even greater reduction in grinding performance is observed. In these cases, it is necessary to interrupt the work and to make the editing of the tool to restore its cutting ability. In addition, it should be borne in mind that in the process of dressing, up to 20-30% of the volume of the circle can be removed to the sludge.

Cutting wheels according to the proposed technical solution and prototype were made of the same compositions:

- diamond powder AC ₆ 80/63 - 46 wt.%

- white aluminum oxide M3 - 54 wt.%

The starting powders were mixed and plasticized. Cutting wheels 1A8 115 × 85 mm, 0.7 mm high were pressed from them. After drying at 200 ° C and carbonization at 800 ° C, the cutting wheels were saturated in natural gas at 1000 ° C at atmospheric pressure. Using optical and electron microscopy methods, thermogravimetric studies, it was found that the binder in the prototype consists entirely of pyrocarbon.

According to the invention, carbon black was additionally introduced into the binder in an amount of 0.3, 3.0 and 3.5 wt.% Due to different time of saturation with natural gas with the addition of 0.15 vol.% Acetylene. The tests were carried out under conditions of cutting carbide VK8 with a hardness of 87.5 HRA. Before the tests, a single dressing of the circles was carried out with a soft bar of green silicon carbide. The working speed of the circles is 25 m / s, the load on the circle is 10 Newtons. During the tests, the circles were intensively cooled with a 3% solution of caustic soda.

The test results are presented in table No. 1:

Grinding (cutting) productivity, [cm ² / min] (numerator), grinding coefficient (denominator). Technology At the beginning of the experiment In 10 minutes In 30 minutes In 40 minutes Prototype 1.9 / 200 1.7 / 200 1.3 / 210 0.9 / 220 Experimental No. 1 (0.3 wt.% Carbon black) 2.1 / 190 2,0 / 205 2,0 / 210 1.95 / 205 Experimental No. 2 (3.0 wt.% Carbon black) 2,3 / 160 2,3 / 170 2.25 / 165 2,2 / 180 Experimental No. 3 (3.5 wt.% Carbon black) 2,5 / 30 2.6 / 25 2,5 / 30 2,4 / 35

The test results showed that when the content of carbon black in the binder is more than 3 wt.%, There is a catastrophic decrease in performance due to a strong decrease in the adhesion of the binder to abrasive grains and its overall softening. Smaller quantities of carbon black in the binder have a positive effect on the performance properties of abrasive products. The cutting performance of hard alloy (after 40 minutes of operation) of the experimental composition No. 1 is more than twice as high as that of the prototype. At the same time, there is no need to interrupt work and make expensive editing of the tool.

Information sources

1. RF patent No. 2164425, B24D 3/00, C08J 5/14, 5/04, 2001.

2. R.G. Avarbe. Chemical gas-phase deposition of refractory structural materials. Leningrad, GIPH, 1976, p. 9.

3. P.A. Tesner. The formation of carbon from hydrocarbons in the gas phase, M., Chemistry, 1972.

4.S. S.Abadzhaev, P.A. Tesner, V.U. Shevchuk. Gas industry, No. 10, 36, 1969.

5. Application of the Russian Federation No. 2001134226/02, B24D 3/20, 18/00, 2003.

Claims (3)

1. The binder formed during the processing of hydrocarbon gas in the conditions of pyrolysis in the pores of the workpiece of an abrasive product, characterized in that the binder has the following composition, wt.%: Carbon black 0.01-3 Pyrocarbon rest 2. The binder according to claim 1, characterized in that the hydrocarbon gas additionally contains 0.15 vol.% Acythylene. 3. A binder formed during the processing of hydrocarbon gas under conditions of pyrolysis in the pores of an abrasive product blank, characterized in that the binder has the following composition, wt.%: Carbon black 0.01-3 Pyrocarbon and Fibrous Carbon rest