SU1759532A1 - Method of making casting molds - Google Patents

Abstract

Use: foundry, namely in the manufacture of casting molds in a pulsed way by burning a mixture of natural gas with air. SUMMARY OF THE INVENTION: In the method, the molding mixture is compacted with gas-impulse pressure obtained from burning a mixture of natural gas with air together with a gaseous additive in the form of gases promoting in relation to explosive combustion in an amount from 0.2 to 1% of the volume of the gas-air mixture.

Description

The invention relates to a foundry, in particular, to methods for producing casting molds by pulsed pressure by burning a mixture of natural gas with air.

The aim of the invention is to increase the efficiency of the compaction process by reducing the burning time and increasing the pressure gradient.

Natural gas with methane content from 85 to 98% according to GOST 5542-78 and gaseous additives were used for research. Saturated hydrocarbons (ethane, butane, propane - according to GOST 5542-78), unsaturated hydrocarbons (ethylene, acetylene), nitrates in the form of methyl nitrite according to GOST 26184-84, nitrates (isopropylnitrate, cyclohexylnitrate - according to GOST

26184-84). nitro compounds (nitroethane. nitropropane - according to GOST 7234-79).

The studies were performed on an experimental setup. Natural gas mixed with air in a stoichiometric ratio and an additive, for example from saturated hydrocarbons, in the form of ethane in a given ratio, for example 0.25% of a mixture of natural gas with air (by volume), were fed into the volume for burning the combustible mixture through the metering device. The additive is dispensed uniformly in volume. From the point source of ignition, the resulting mixture ignited. By means of a highly sensitive piezoelectric pressure sensor of the design of the Institute of Chemical Physics of the USSR Academy of Sciences with a preamplifier and a storage oscillograph C8-13, the pressure change with time was determined

cl

ate with

which made it possible to determine the pressure gradient, and by the nature of the oscillograms to judge the course (kinetics) of the combustion process.

Similarly, studies were carried out when the amount of this or another of the above additives supplied in volume with a combustible mixture of natural gas with air was changed.

As a result of the research, it was found that the addition of these gaseous substances up to 0.2% had practically no effect on the pressure gradient, i.e. The pressure gradient practically does not differ from the pressure gradient obtained by burning the natural gas with air according to the prototype and does not exceed 18-27 MPa / sec.

With the introduction of the above additives in the amount of 0.2-1%, a significant increase in the pressure gradient occurs.

(Ј) compared to the prototype. In particular, with the introduction of ethane in the amount of 0-2% () increases by 3 times, and

O t

its introduction in the amount of 0.5 and 1% --- age-1R. dr

respectively 7.5 and 15 times.

Similar results were obtained using propane or butane instead of ethane. When ethylene or acetylene is introduced

in the amount of 0.9 and 1% --Ј- increases by 20

U z

times compared to the prototype. Similar- -V- 20 times received

increase

ig

with the introduction of methyl nitrite or isopropyl nitrate or cyclohexyl nitrate in the amount of 0.2%, and with the increase of these

components to 0.9-1% - increases in

100 times. The introduction of additives in the form of nitroethane or nitropropane in an amount of 0.2% increases

Ael

dr

compared to the prototype 10 times. and in

the amount of 0.9-1%, respectively, 50 times.

The greatest effect on the increase in the pressure gradient is achieved with the joint introduction of several of the above additives. In particular, with the joint introduction of ethane and propane, respectively, in quantities of 0.2 and 0.1% increases 9 times, with about t

co-injection of ethane, propane and ethylene by -Ј- increases 13 times, and joint

About

the introduction of ethane, ethylene and nitroethane by 0.2% increases & - 20 times.

About t

2%

When the gaseous components of these substances are fed above a concentration of 1%, there is a disturbance in the normal combustion regime.

The increase in the pressure gradient of the invention due to the addition of additives is due to the reduction of the combustion time. (Mainly by reducing the ignition time). According to prototype 0, the combustion cycle is 0.02-0.025 s, and according to the invention, it decreases the more, the more the pressure gradient increases. For example, with the addition of ethane, propane 5 or butane in the amount of 0.2%, the pressure gradient increases by 3 times, and the burning time decreases by 3 times and equals 0.006-0.008 s. With the joint introduction of ethane and propane in amounts of 0.2% and 0.1%, the combustion time 0 is 0.0025 s, i.e. is reduced by a factor of 9 compared to the prototype.

The use of the proposed method of making casting molds by gas-impulse action with the introduction of additional gas components or their mixtures in comparison with the existing methods provides the following advantages:

increasing the efficiency of the compaction process 0 by reducing the burning time and increasing the pressure gradient;

increasing the competitiveness of the proposed method compared to air-pulse;

increase in the degree of stabilization of the pressure gradient, process reliability.

Claims (3)

1. A method of making casting molds, including filling the model-tooling with a mixture, filling the working cavity of the pulse head with natural gas to obtain a stoichiometric ratio of the gas-air mixture, igniting the latter and sealing the molding mixture with the energy of the air-gas mixture that differs from In order to increase the efficiency of the compaction process by reducing the combustion time and increasing the pressure gradient, a portion of the promoters are introduced into the gas-air mixture explosive combustion of gases in the amount of 0,2-acetylene, methyl nitrite, isopropyl nitrate, 1.0% of the volume of the gaic airborne mixture. Nitroethane, nitropropane. 2. The method according to claim 1, characterized by 3. The method according to claim 2, wherein by the fact that, as ghomotous gases, that the promoting gases are introduced, ethane, propane, butane, ethylene, 5 are different or in total.