RU2014211C1 - Foundry sand for abrasive tool making - Google Patents

Abstract

FIELD: abrasive tools. SUBSTANCE: foundry sand has synthetic corundum abrasive, kaolin, feldspar, talc, temporary binder, water and boroncalcium frit at the ratio of feldspar and frit 1:(1.3-2.2). Foundry sand has the following composition, wt.-%: synthetic corundum abrasive 69.9-90.1; kaolin 1.3-8.3; feldspar 0.9-7.1; talc 0.05-1.7; water 0.45-3.9; temporary binder 0.7-4.9, and boroncalcium frit 1.8-11.9. EFFECT: enhanced quality of foundry sand. 2 tbl

Description

 The invention relates to the production of abrasive tools, in particular to a molding mixture for the manufacture of high-strength tools from micro-grinding powders and grinding powders of electrocorundum with a grain size of 8, 6, M63, M40.

A known molding mixture for an abrasive tool made of micro-grinding powders and grinding powders with a grain size of 6 and 8 (technological process TP 1900013.01201.0000). It has the following ratio of components, wt.%:
Electrocorundum material 70.0-88.0
Dry Dextrin 0.9-3.6
Water 1.3-3.6
Ceramic bond 12.5-25.0
The disadvantage of the tool made from the specified molding sand is the inability to use it when grinding at a speed above 35 m / s, in addition, the tool has insufficient microstability.

Closest to the claimed is the mass for the manufacture of abrasive tools, including the following components, wt.%:
Electrocorundum 50-60
Kaolin 7-13
Bentonite 3-7
Boron glass 2-5
Crystalline silicon 4-10
Feldspar Else
The specified mass allows you to get the tool with the required characteristics and strength sufficient for its operation at an operating speed of 60 m / s.

 However, it does not provide the necessary edge resistance and, therefore, the persistent operating time. This is due to the fact that, in addition to electrocorundum and ligament components that form connecting bridges in the tool (kaolin, concrete, boron glass and feldspar), it contains 10-15% of the mass of crystalline silicon electrocorundum. Silicon-reinforced ligament bridges are highly durable and provide increased tool strength. But when grinding threads on taps with a tool from a known mass, durable silicon-containing areas cause burns, circles are greased. To restore their cutting ability, frequent editing is required, which reduces the tool life.

 The purpose of the invention is to increase the edge resistance and mechanical strength of the tool.

For this, the molding mixture for the manufacture of an abrasive tool contains electrocorundum grinding material, kaolin, feldspar, temporary binder, moisturizer, as well as talc and boron-calcium frit. In this case, feldspar and boron-calcium frit are introduced in the ratio 1: (1.3-2.2), and the components of the mixture in the following ratio, wt.%:
Electrocorundum material 69.9-90.1
Kaolin 1.3-8.3
Feldspar 0.9-7.1
Talc 0.05-1.7
Water 0.45-3.9
Temporarily binder 0.7-4.9
Calcium Frit 1.8-11.9
While boron-calcium frit contains, wt.%:
SiO ₂ 41.0 ± 0.5
Al ₂ O ₃ 12.5 ± 0.2
B ₂ O ₃ 25.0 ± 0.5
CaO 12.5 ± 0.5
Na ₂ O 6.5 ± 0.2
K ₂ O 2.5 ± 0.2
The difference from the prototype is the use of a mixture of boron-calcium frit, as well as the introduction into the mixture as a temporary binder dextrin, and as a humidifier - water. The molding properties of the prototype are ensured by the introduction of liquid glass, which for molding mixtures from electrocorundum of the grit indicated in the application does not provide uniform mixing of the components, which does not allow to obtain a tool with sufficient mechanical strength.

 The proposed composition of the moldable mixture provides an abrasive tool for multi-thread thread grinding operations on semi-automatic thread grinding machines at a speed of 60 m / s.

 The content of the components in the molding sand within the specified limits makes it possible to obtain abrasive tools from grinding and micropowders with grains of 8, 6, M63, M40 with a hardness range from “soft” to “hard”.

 The choice of boundary limits for the content of components in the molding sand was determined experimentally, it is due to the need to obtain products having sufficient strength immediately after molding, in dried form and strength after firing.

 When the content of electrocorundum material is more than 90.1 wt.%, The product cannot be molded by the method of semi-dry pressing; if the content of abrasive material is less than 69.9 wt.%, then the products do not have the required strength for grinding at a speed of 60 m / s.

 A decrease in kaolin content of less than 1.3 wt.% Makes the mixture unplastic, and the raw materials of the product have low mechanical strength, which leads to marriage of products; exceeding the content of kaolin of more than 8.3 wt.% does not ensure the receipt in the finished tool of strong glassy bridges connecting the grains of abrasive material.

 The decrease in the content of feldspar below 0.9 wt.% Makes the composition refractory, and exceeding the specified limit of 7.1 wt.% Leads to a decrease in the strength of the samples.

 Changing the range of permissible talc content above 1.7 wt.% Or less than 0.05 wt.% Makes the samples not strong enough.

 An increase in water content above 3.9 wt.% Leads to clumping of the molding mixture, and when the water content decreases below 0.45 wt.%, Freshly formed articles are not strong enough.

 The decrease in the content of the temporary binder below 0.7 wt.% Leads to low stickiness of the mixture and, accordingly, low strength raw; the excess of the amount of temporary binder above 4.9 wt.% affects the molding properties of the mixture, it is distributed unevenly, and the products have uneven hardness.

 The limiting ratios of feldspar and frit are selected according to the results of determining the strength of the samples; the products have the necessary strength to operate at a speed of 60 m / s only with a frit content exceeding the content of feldspar by 1.3-2.2 times.

 Examples of specific performance.

 The preparation of the molding mixture for the manufacture of thread-grinding abrasive tools of type 450 x 25 x 228.6 of chromium-titanium electrocorundum with a grain size of N 6 is as follows.

 A portion of the abrasive (69.9 wt.%) Is moistened with water (3.8 wt.%) And mixed with dextrin (0.8 wt.%) And a mixture of kaolin (8.3 wt.%), Feldspar (4.9 wt.%), talc (0.3 wt.%) and powder of boron-calcium glass (11.9 wt.%) with a ratio of field cap and frit of 1: 1.3, respectively.

The mixture is wiped through a mesh N 320 or N 400, weigh the required sample and put into the mold, form a circle on the press with a force of 100 tons, the molded product is dried and fired in a tunnel oven at 1200-1220 ^about C.

 Variants of compositions for obtaining molding sand are given in table. 1, there is also given data on the physico-mechanical properties of samples from molding mixtures of the proposed composition and prototype.

 Operational tests of the tool from molding mixtures of the proposed composition were carried out on a thread-grinding semiautomatic device mod. "Matrix-79" for taps processing operations.

 The results of comparative tests are given in table. 2.

 An analysis of the results of comparative tests (Tables 1 and 2) shows that the circles made of the molding mixture of the proposed composition have mechanical strength, which ensures their operation at an operating speed of 60 m / s and, in contrast to the prototype circles, high service life.

Claims (1)

FORMING MIXTURE FOR THE PRODUCTION OF ABRASIVE TOOLS, including electrocorundum grinding material, kaolin, feldspar, a temporary binder and a moisturizer, characterized in that, in order to increase the edge resistance and mechanical strength of the tool, talcum and boron-calcium frit are introduced into the mixture, and - water, with feldspar and frit introduced in a ratio of 1: 1.3 - 2.2, and the components of the mixture introduced in the following ratio, wt.%:
Electrocorundum grinding material 69.9 - 90.1
Kaolin 1.3 - 8.3
Feldspar 0.9 - 7.1
Talcum 0.05 - 1.7
Water 0.45 - 3.9
Temporary binder 0.7 - 4.9
Boric-calcium frit 1.8 - 11.9

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