RU2076038C1 - Moulding mixture for production of abrasive tool - Google Patents

Abstract

FIELD: production of abrasive tools of electrocorundum materials based on ceramic binder. SUBSTANCE: Mixture has, mass %: 49,0 - 62.7 of grinding grain of white electrocorundum with graininess of 40, 50 as main fraction of grinding material; 12.0 - 16.0 of grinding fine grain with graininess of 10, 12 and 1,3 - 3,0 of fine grinding micro grains with graininess of M5, M7 as additional fraction of white electrocorundum; 18.5 - 24.5 of ceramic binder; 5.0 - 6.0 of liquid glass and 0.5 - 1.5 of И-20А industrial oil used as plasticizer. EFFECT: improved quality of abrasive tools of electrocorundum materials based on ceramic binder. 2 tbl

Description

 The invention relates to the field of production of abrasive tools from electrocorundum materials on a ceramic bond, in particular, ball grinding heads designed for machining bevels of bolt holes in railway rails.

 Currently, the processing of bolt holes is carried out using milling cutters with carbide inserts, which do not satisfy consumers due to marriage (burns, cracks) of the treated surfaces.

 For processing rails, an abrasive tool can be used, which in this case should have high hardness, strength and stability of the geometric shape.

 Known molding mixture to obtain an abrasive tool [1] containing, by weight. ceramic bond 7.0 13.5; water glass 3.5 4.5; dextrin 1 2; micropowder abrasive grit M10-M20 3,5 11 and grinding the rest. However, grinding wheels made of this mass have insufficient strength and hardness for our purpose.

 Closest to the invention in technical essence and the achieved result is the mass (molding mixture) for the manufacture of abrasive tools [2] based on electrocorundum of several granularities, which include, wt. grinding 60 64; grinding material (grinding and micro grinding powders) 17 26; ceramic bunch the rest. (Prototype). Electrocorundum with a grain size of 40.25 and 16 is used as a grinding wheel. But this mixture, due to increased shrinkage during firing, does not provide the tool made from it with the stability of a geometric shape (ball) and due to internal stresses of the required strength.

 The molding mixture for the manufacture of an abrasive tool in accordance with the invention includes a ceramic bond, liquid glass, electrocorundum with a grain size of 40, 50, grinding powders with a grain size of 10.12, thin micro-grinding powders with a grain size of M5, M7 and plasticizer oil industrial I-20A in the following ratio of components, wt.

Ceramic bond 18.5 24.5
Liquid glass 5.0 6.0
Electrocorundum grit 40.50 49.0 62.7
Sanding powder with a grain size of 10.12 12.0 16.0
Fine microsize powders with grain size M5, M7 1.3 3.0
Plasticizer oil industrial 0.5 1.5
Boundary limits of the content of the components of the molding mixture are determined experimentally and due to the need to create a high-strength tool with a high degree of hardness and a stable geometric shape, as well as the requirements of the manufacturability of the process of manufacturing circles.

 The introduction of electrocorundum with a grain size of 40.50 in the amount of 49.0 62.7 and ceramic ligaments in the amount of 18.5 to 24.5 wt. provides a stable abrasive tool of the required degree of hardness T1-CT. An increase in the ligament content and, accordingly, a decrease in the amount of electrocorundum lead to the appearance of a marriage in the form of smelting and deformation of the tool; a decrease in the binder content and an increase in the content of the grinding material reduces the hardness.

 The introduction of water glass in the specified interval is due to obtaining a mixture of the necessary moisture and strength of the raw material without changing the alkali content in the bundle. An increase in the content of liquid glass in the mixture leads to deformation of the preforms during firing; reduction to decrease the moisture content of the mixture, formability and strength of raw products.

 The introduction of electrocorundum into the molding mixture of grinding and microsulfur powders filling the voids between the grains of the main electrocorundum fraction helps to reduce the shrinkage of the tool blank during firing. In addition, up to 15 wt. aluminum oxide (of which white electrocorundum is composed) passes (adheres) to the melt, which subsequently enters the solid solution of the compounds forming the binder. Thus, on the one hand, the geometric shape of the product is ensured, which is important when obtaining a ball grinding head, on the other hand, the adhesion of the bond to the grinding material is sharply increased, which helps to increase the mechanical strength of the tool.

 Boundary limits of the content of polished and micro-polished electrocorundum powders are due to the need to obtain a tool with high mechanical strength and low shrinkage of the workpiece during firing. The introduction of them in large quantities leads, due to the high reactivity of the electrocorundum, to obtain a deformed fused tool; a decrease in their content causes a decrease in the strength of the tool below the permissible limit.

 The introduction of the plasticizer in the indicated amount leads to a decrease in the pressure exerted on the molded product, an increase in the strength and stiffness of the dried products, which helps to reduce molding and thermal stresses and, accordingly, the marriage of products after drying. Changing the content of the plasticizer in the direction of increase increases the moisture content of the mixture and reduces the strength of the raw material, and a decrease does not give the necessary plasticization effect during the manufacturing process of the tool.

 When implementing the invention, grinding abrasive, grinding and micro grinding powders of electrocorundum are used as an abrasive according to GOST 3647-80; as a plasticizer industrial oil I-20A according to GOST 20799-75; as a ceramic bond, a bond of the K20M brand according to TU 2-036-984-86, usually used in the manufacture of an abrasive tool; as glass - soda glass in accordance with GOST 13078-81.

 The molding mixture is prepared as follows. The calculated amount of white electrocorundum with a grain size of 40 or 50 is loaded into the mixer, moistened with liquid glass, the required amount of grinding powder with a grain size of 10 or 12 and a fine micro-powder M5, M7 are added and mixed for 10 15 minutes, then the ceramic binder is loaded and mixed for 15 20 minutes . A plasticizer is added to the resulting mixture and mixed again for 15 to 20 minutes. The finished mixture is wiped through a sieve with a mesh size of 1 mm.

 The composition of the mixture are given in table 1.

G8 samples are molded from the resulting mixture and fired at a temperature of 1200-1250 ^o C. Then, by known methods, the hardness of the samples, their shrinkage during firing and the tensile strength, which evaluate their mechanical strength, are determined. The results of comparative tests of samples of the proposed composition and prototype are given in table.2.

 An analysis of the results of comparative tests shows that the molding mixture according to the invention allows, due to less shrinkage during firing due to the rational packing of electrocorundum of different grain sizes, by 10 25% to increase the mechanical strength of the products, to obtain a tool with a high degree of hardness. In addition, the invention allows to eliminate the marriage of fusion and deformation of the tool.

 The tool of the proposed mixture can be manufactured at any abrasive plant using existing equipment. Non-deficient and non-toxic components are used for its production.

Claims (1)

 Molding mixture for the manufacture of an abrasive tool, including a ceramic bond, liquid glass, as an abrasive an electrocorundum with a grain size of 40 and grinding powders, characterized in that the mixture further comprises an electrocorundum with a grain size of 50, grinding powders with a grain size of 10, 12, thin micro-grinding powders with a grain size of M5, M7 and an oil plasticizer I-20A in the following ratio of components, wt. Ceramic bond 18.5 24.5
Liquid glass 5.0 6.0
Electrocorundum with grit size 40, 50 49.0 62.7
Sanding powders with grain size 10, 12 12.0 16.0
Thin micro-powders with grain size M5, M7 1.3 3.0
Plasticizer oil industrial I-20A 0.5 1.5v

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