RU2433032C1 - Mass for production of abrasive wheel - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to grinding and may be used for production of high-porous abrasive tools, for deep grinding. Proposed mass comprises abrasive grain, ceramic binder, temporary binder, filler made up of hollow silica-alumina spherical particles, combustible filler and moistener. Additionally, it includes 250-1000 mcm-dia emery spheres with spongy internal structure and bulk density of 1.4-1.7 g/cm³.

EFFECT: higher processing quality.

2 tbl

Description

The invention relates to the production of an abrasive tool, namely a highly porous abrasive tool made of electrocorundum on a ceramic bond, intended for deep grinding.

The technological properties of the abrasive mass are determined by its miscibility, flowability, formability, tendency to form lumps, strength and edge resistance of the molded raw workpiece. In addition, the abrasive mass must ensure minimal shrinkage of the product during the firing process and stability of characteristics in the volume of each abrasive tool and in the batch of tools. Particular importance is attached to such indicators as hardness and mass imbalance (imbalance), due to the fact that one of the areas of application of a highly porous abrasive tool is the deep grinding of the surfaces of gas turbine engine blades made of heat-resistant nickel alloys, where defects in the machined surfaces are unacceptable.

Known mass for the manufacture of a porous abrasive tool containing a ceramic bond, abrasive grains, electrocorundum spherical particles, burnable filler in an amount of 0.1-0.5 of the volume content of abrasive grains, while the electrocorundum particles are introduced into the mass in an amount of 0.25-2 , 0 from the volumetric content of the burnable filler (see IPC B24D 3/14, description of the invention to the USSR copyright certificate No. 1685695, publ. 10.23.1991).

A disadvantage of the known mass is the high cost of electrocorundum hollow spherical particles, which significantly affects the final cost of the finished abrasive tool from this mass.

In addition, the tendency of these particles to segregate with other components of the mass, their “floating” when mixed due to the lower bulk density of the particles relative to the bulk density of the abrasive grain does not allow to achieve a uniform distribution of these particles throughout the volume of the abrasive mass and to obtain high-quality from it abrasive tool.

Closest to the claimed technical solution is the mass for the manufacture of an abrasive tool, including an abrasive, a ceramic bond, a filler in the form of hollow spherical particles of aluminosilicate with a size in the range from 5 to 500 microns and in an amount of 2-200 vol.% Abrasive, or additionally filler in in the form of heat-resistant hollow spherical particles of electrocorundum in an amount of 5-100% of the volume content of aluminosilicate filler, or additionally a filler in the form of hollow spherical particles of fusible glass in an amount 5-100% volume content of aluminosilicate filler, or additionally burnable filler in an amount of 5-250% volume content of aluminosilicate filler, or a mixture of the above additional fillers taken in a total content of 5-250% relative to the volume content of aluminosilicate filler (see IPC B24D 3/18, B24D 3/34, description of the invention to the patent of the Russian Federation No. 2152298, publ. 07/10/2000) - the closest analogue.

However, the disadvantage of the above abrasive mass and the abrasive tool made from it is the high unevenness of the distribution of mass components by volume, which significantly affects the performance of the tool, especially imbalance and hardness.

The technical result of the claimed invention is to increase the technological properties of the mass and quality of the finished abrasive tool.

The essence of the technical solution lies in the fact that the mass for the manufacture of an abrasive tool, including abrasive grain, a ceramic binder, a temporary binder, a filler in the form of hollow aluminosilicate spherical particles, a burnable filler and a humidifier, additionally contains spherical corundum with a diameter of 250-1000 microns with a spongy internal structure in the form of spheres with internal porosity and bulk density of 1.4-1.7 g / cm ³ .

Spherical corundum with a spongy internal structure, introduced into the abrasive mass as a filler, allows to improve the miscibility of the abrasive mass, to ensure imbalance of the wheel at an acceptable level during its wear during operation, as well as a more uniform circle hardness throughout the volume. This is achieved due to a more uniform distribution of pores, abrasive grain and fillers in the finished abrasive tool.

In combination with aluminosilicate hollow spherical particles, spherical corundum with a spongy structure improves the flowability of the abrasive mass, which allows for better placement of the abrasive mass into the mold, its compressibility, and reduced shrinkage of the obtained abrasive tool during its firing.

Sponge corundum with a spongy structure is a by-product of the production of electrocorundum, therefore, it is much cheaper than grinding grain, which, along with a decrease in the amount of expensive abrasive grain in the formulation, can significantly reduce the cost of the resulting abrasive tool.

The specified limit values of bulk density of 1.4-1.7 g / cm ³ provide the best stability of the properties of the abrasive tool throughout the volume. At a bulk density below 1.4 g / cm ^3, spherocorundum is prone to segregation and, when mixed in a mixer, tends to “float” with aluminosilicate hollow spherical particles fixed to it with an adhesive. At a bulk density above 1.7 g / cm ^3, spherocorundum loses its spongy structure and ceases to participate in the grinding process in the finished abrasive tool.

The indicated diameter values are due to the fact that when the diameter is less than 250 microns, the ratio of open and closed pores changes to open, which reduces the technological characteristics of the abrasive tool at a given size of abrasive grain. Exceeding the diameter of 1000 μm also leads to a deterioration in the technological characteristics of the tool due to a change in the ratio of open and closed pores to the side of closed ones.

Thus, the specified limiting values of bulk density and dimensions of spherical corundum with a spongy structure are optimal for achieving a technical result.

Moreover, when mixing the mixture, the interaction of hollow spherical particles of aluminosilicate and spherical corundum with the formation of a structure that eliminates the destruction of thin aluminosilicate particles during the pressing process and provides a more uniform distribution of the components of the mixture and pores in the finished abrasive tool, which also improves its performance.

The abrasive mass is obtained in a known manner. In a mixer, for example, of the type SM-200, abrasive grain, a ceramic binder, a temporary binder, a burnable filler are mixed, and a filler from a mixture of spherical corundum with a sponge structure, hollow spherical particles of aluminosilicate and adhesive is introduced into the resulting mixture.

The abrasive tool is molded by compression. First, the abrasive mass is poured into the mold, leveled and pressed with a force, for example, 70-200 kg / cm ² . After pressing, the preform is kept under natural conditions depending on its size for 40-48 hours, then dried at 40-50 ° C and fired at a temperature of 1240 ° C ± 10 ° C.

After firing, the workpiece is machined to give it the desired geometry.

After machining, control operations are carried out to verify deviations from those specified in the normative documentation on geometric dimensions, hardness, imbalance, appearance, as well as on mechanical strength by scrolling at a test speed on a test bench of the SIP-800 type.

Table 1 shows examples of masses compiled in accordance with the claimed technical solution, and table 2 shows the technical characteristics of the obtained abrasive tool.

Table 1 The composition of the abrasive masses No. p / p The composition of the abrasive mass Example 1 Example 2 Example 3 (volume%, reduced to circle volume) one. Abrasive grain + spherocorundum with a spongy internal structure: - size 400 μm + spherocorundum size 1000 μm (bulk density 1.68 g / cm ³ ) 46 - size 250 μm + spherocorundum size 500 μm (bulk density 1.59 g / cm ³ ) 42 - size 160 μm + spherocorundum size 250 μm (bulk density 1.45 g / cm ³ ) 38 2. Humidifier 6.7 5.3 4.8 3. Ceramic bond K-5 10.5 14.5 fourteen four. Burning out filler (fruit stone KF-40, size 400 microns) 9.5 12 fourteen 5. Temporary Binder (Dextrin) 5 5 5 6. Aluminosilicate hollow thin-walled spherical particles 5-500 microns in size 10 11.5 13 7. Spherical corundum with a spongy internal structure - size 1000 μm (bulk density 1.68 g / cm ³ ) 7 - size 500 μm (bulk density 1.59 g / cm ³ ) 8 - size 250 μm (bulk density 1.45 g / cm ³ ) 6 8. Natural pores rest rest rest

table 2 Characteristics of an experienced abrasive tool No. p / p Characteristic Example 1 Example 2 Example 3 one. Circle shape Direct profile Direct profile Direct profile 2. Outer diameter mm 300 300 300 3. Height mm 40 40 40 four. Diameter of a landing hole, mm 76 76 76 5. Grain abrasive grain 25A 25A 25A 6. The size of the abrasive grain, microns 400 250 160 7. Structure 8 10 12 8. Ceramic bunch K5 K5 K5 9. Hardness I (M2) I (M2) I (M2) 10. Mass Unbalance Class 2 2 2 eleven. The mass imbalance value allowed by GOST 3060-86 twenty 16 16 12. The value of mass imbalance, actual eighteen 16 fourteen

For experimental verification of the claimed invention of the three compositions of the experimental abrasive mass shown in table 1, were made on one abrasive wheel with the characteristics listed in table 2.

The stability of mass imbalance (imbalance) was verified as follows.

Abrasive wheels made from experimental abrasive masses after machining, dimensional control and mechanical strength tests were checked for imbalance on the balancing stand using the method of measuring unbalanced masses in accordance with GOST 3060-86 “Grinding wheels”. Permissible unbalanced masses and measurement results are shown in table 2.

Then, to simulate wear during continuous dressing with a diamond roller during deep grinding, abrasive wheels were grind in diameter on a special RT-102 machine to smaller diameters: from a diameter of 300 mm to a diameter of 275 mm, then to a diameter of 250 mm and so on to diameters of 225 mm and 200 mm. After each grinding, the wheels were checked again at the stand. In each case, the mass imbalance corresponded to normative values.

Thus, the inventive mass for the manufacture of an abrasive tool in comparison with known analogues allows to exclude the occurrence during operation of the abrasive wheels mass imbalance (imbalance) above the permissible values as the circles wear in diameter.

Claims (1)

A mass for the manufacture of an abrasive tool, including abrasive grain, a ceramic binder, a temporary binder, a filler in the form of aluminosilicate hollow spherical particles, a burnable filler and a humidifier, characterized in that it further comprises spherical corundum in the form of spheres with a diameter of 250-1000 μm with a spongy internal structure and bulk density of 1.4-1.7 g / cm ³ .