RU2071865C1 - Method for preparation of liquid glass binder - Google Patents

Abstract

FIELD: foundry; manufacture of liquid glass binder for cores and moulds. SUBSTANCE: liquid glass binder is made using dust wastes of ferrocilicium production melting furnaces. First pulp is prepared by mixing water with alkali solution with subsequent heating of mixture to reaction starting point. Either pulp or water solution of alkaline metal hydroxide, and or their mixture can be heated. Binder of required modulus and density is produced. Moulds and cores of mixtures with such binder are easy to shakeout. EFFECT: enlarged operating capabilities. 1 tbl

Description

 The invention relates to foundry, in particular to a method for producing a liquid-glass binder used for the manufacture of cores and molds, and may also find application in other economic sectors.

A known method of producing liquid glass is a duplex process in which a mixture of quartz sand and soda is melted at a temperature of 1400 1450 ^o C, followed by dissolution of the resulting silicate blocks at a vapor pressure of 5 8 atm [1] [2]
This technology is associated with high energy costs, and the composition of the glass does not allow to obtain easily destroyed when knocking out rods and shapes.

There is also known a one-stage method for producing liquid glass, the essence of which is to prepare a working suspension (crushed quartz sand, a solution of caustic soda) and its subsequent processing in an autoclave at a pressure of 25 atm. and a temperature of 215 ^o C for 2 hours. 45 min [1] [2] The obtained liquid glass has the previously described disadvantages.

The closest technical solution to the proposed one is a method for producing a silicate binder based on amorphous modifications of silica [2] The essence of the method consists in the use of silica gel (waste production of aluminum fluoride salts) or ground diatomite. In both cases, amorphous silica modifications are mixed with alkali and heated to 40 - 85 ^° C with constant stirring for 20 70 minutes. In this process, a silicate binder is formed during the cooking process (chemical interaction of SiO ₂ and, for example, NaOH).

 The described method is associated with high energy costs (the duration of the cooking process, crushing of diatomite), as well as the inability to get easily destroyed when knocking rods and shapes.

 The aim of the invention is to obtain a binder providing easy knockout of molds and cores, as well as reducing costs when it is received.

 The goal is achieved by the fact that pulp is prepared from the pulverized waste from smelting furnaces of ferroalloy plants containing silicon dioxide, which is mixed with an aqueous solution of alkali metal hydroxide. To obtain a binder, the pulp or the hydroxide solution and / or their mixture is heated to a temperature that ensures the onset of a chemical reaction to form a liquid glass binder.

 The method can be implemented in several ways.

 Scheme 1.

 1.2. Preparation of pulp from dusty waste (a variant is possible when high-temperature dust comes directly from the filters of the treatment plants of furnaces).

 1.2. Preparation of an alkali metal hydroxide solution.

 1.3. Dosing of components (can be done after heating).

 1.4. Heating one of the components or both to a temperature ensuring the start of the reaction during mixing.

 1.5. Mixing the pulp of an alkali metal hydroxide with the simultaneous course of the reaction and exposure to completion of the binder formation reaction.

 1.6. Unloading the binder and its sediment.

 Scheme 2.

 2.1. Pulp preparation from dusty waste (preheating possible).

 2.2. Preparation of an alkali metal hydroxide solution (preheating is possible).

 2.3. Dosing of components.

 2.4. Mixing pulp with an alkali metal hydroxide solution.

 2.5. Heating to the temperature of the beginning of the reaction and holding to its completion (usually does not exceed several minutes).

 2.6. Unloading the binder sucks.

 Scheme 3.

 3.1. Pulp preparation from dusty waste.

 3.2. Preparation of alkali metal hydroxide.

 3.3. Dosing of components.

 3.4. Mixing pulp with alkali metal hydroxide.

 3.5. Heating to the temperature of the beginning of the reaction (it is possible to combine in time with mixing).

 3.6. The unloading of the binder (can be combined in time with the reaction of the formation of the binder and with mixing) it sucks.

 Scheme 4.

 4.1. Preparation of an alkali metal hydroxide solution.

 4.2. Dosing of dust and hydroxide solution.

 4.3. Mixing dust with a hydroxide solution.

 4.4. Heating to the temperature of the beginning of the reaction and holding to its completion.

 4.5. The unloading of the binder (can be combined in time with the reaction of formation of the binder) and its sediment.

 The above schemes are not a complete list of possible options for conducting the process, but show a number of acceptable options.

The reaction of the formation of a binder in all the described schemes begins at a heating temperature of not higher than 60 ^o C and proceeds with the release of a significant amount of heat, which allows to reduce energy costs only for the start of the process. In the future, the reaction proceeds without energy consumption.

 The heat generated causes intense evaporation and therefore violent foaming, therefore it is necessary to constantly suppress the foam.

 The choice of the ratio of the components involved in the reaction (silicon dioxide, alkali metal hydroxide), as well as the amount of water, makes it possible to obtain a liquid-glass binder of the required module and density (taking into account errors). At the same time, the value of the binder module can be changed by the subsequent introduction of the required amount of alkali into the binder and mixing until the composition is averaged.

 Example 1. Obtaining a liquid glass binder using dusty waste from melting furnaces produced by ferrosilicon was carried out by mixing dusty waste or pulp containing dusty waste with an alkali solution, followed by heating the mixture to the temperature at which the reaction began (according to the above schemes).

 The previously described schemes for producing a liquid glass binder were implemented.

 The content of silicon dioxide in dusts was 80–96%. The rest was oxides of iron, aluminum, calcium, magnesium, and manganese.

 In all cases, a liquid-glass binder was obtained with the required (taking into account errors) properties (modulus, density, viscosity). The time to obtain the binder in laboratory and industrial conditions during batch production did not exceed 10 minutes. The dusty wastes of two weeks, two months and a year ago were subjected to analysis.

 The test results of the properties of mixtures containing 94% sand and 6% binder are given in the table. As can be seen from the table, the resulting binder can be used in foundry to obtain cores and molds. It has properties no worse than those described in the prototype.

 Example 2. In addition, in order to reduce the cost of obtaining a liquid glass binder as a component containing alkali metal hydroxides, leached waste from precision casting was used.

 A liquid glass binder with properties similar to those described in the table was obtained according to schemes 2 and 3.

 Rods and mixtures obtained using a liquid glass binder (table) were used for the manufacture of cast iron and steel castings. In all cases, rods and molds are obtained that meet technological requirements. Castings met all technical requirements. It was found that the rods and molds made using a liquid-glass binder obtained from ferroalloy waste products, after their contact with molten metal, partially lose their strength, which leads to a significant improvement in their knockability.

 The above description shows that the proposed technical solution has the following advantages.

 To obtain a liquid-glass binder, dusty waste from ferroalloy furnaces and leachate from precision casting foundries, other waste with similar properties that pollute the environment can be used.

Upon receipt of the liquid-glass binder, only the preliminary heating of the components to the temperature of the onset of the chemical reaction of the formation of the binder (not higher than 60 ^o C) is necessary. Further maintenance of the energy condition for the reaction proceeds due to the heat generated.

 Compared with the prototype, there is no need for crushing the material, which eliminates the additional energy costs.

 Increases productivity in the production of a binder, due to the possibility of separating the operations of mixing, dosing and aging for the duration of the reaction.

 There is an opportunity to obtain a cheap binder through the use of production waste and reduce energy costs for the preparation of components and in the production of a binder.

 The resulting products (rods and molds) do not pollute the environment and, being crushed to the required grain size, can be reused for the same purpose.

Claims (1)

 A method of producing a liquid glass binder, comprising mixing a material containing silicon dioxide with an aqueous solution of alkali metal hydroxide and heating, characterized in that the material containing silicon dioxide is used in the form of pulverized waste ferroalloy furnaces from which the pulp is prepared, and the pulp is heated or an aqueous solution of alkali metal hydroxide and / or a mixture thereof to a temperature ensuring the onset of a chemical reaction.

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