SU814563A1 - Exothermic mixture for heating copper and aluminium alloy casting heads - Google Patents

Description

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The invention relates to casting production, namely to compositions of exothermic mixtures for heating the profits of castings from copper-aluminum based alloys.

Exothermic mixtures are known for heating the profits of castings, which contain aluminum powder, iron ore, manganese ore, fluorspar, refractory clay, Schmotm binder (technical fish glue) and water Ø.

However, this exothermic mixture has a high onset temperature of thermochemical reactions, a long incubation period before the onset and spontaneous thermochemical reactions occur and is not suitable for heating the profits of castings from copper and aluminum base alloys, besides it has relatively low physical and mechanical properties.

Closest to the proposed technical essence and the achieved result is an exothermic mixture for heating the profit of castings from copper and aluminum alloys, containing aluminum powder or chips, a crumb from an aluminum-magnesium alloy, iron oxide or iron ore, an oxygen-containing oxidant with a decomposition temperature below 500 ° C (potassium nitrate), charcoal, sawdust, building plaster, refractory clay, fireclay and binder C21

0

Despite the available indication of the onset of exothermic reactions of 400-700 ° C, for a further known mixture fire is characteristic only at a temperature corresponding to the upper limit of the specified temperature range.

The choice of iron ore or scale as the main oxidizing agent in extracts for heating profits from non-ferrous alloys leads to long-term heating before the ore oxidant decomposes and a significant lengthening of the time before thermochemical reactions begin.

five

The presence in the mixture of sawdust, gradually coking under the action of the heat of the metal profit, contributes to the expenditure of oxygen released during decomposition

0 potassium silicate, on their burning and deteriorates the oxygen balance of thermochemical reactions. Construction gypsum in the mixture increases the hygroscopicity of products. In addition, when drying products at temperatures of about 180 ° C, their strength is significantly reduced by converting gypsum dihydrate to hemihydrate. In the case of high-temperature decomposition of gypsum, sulfur gases are released, which is also a negative factor. The purpose of the invention is to increase the efficiency of thermal work in relation to the production of castings from aluminum and copper alloys. The goal is to achieve an exothermic mixture for heating the profit of castings from copper and aluminum alloys, including a reducing agent based on aluminum and magnesium, ore oxidizer, an oxygen-containing oxidizer with a decomposition temperature less than, refractory clay, refractory filler and bonding, different from that what. it contains manganese ore as an ore oxidant and additionally contains fluoride in the following ingredients, wt%: Aluminum-based reducing agent and magnesium 13, 5-18, nor Manganese ore 40.0-52, oxygen-containing oxidizer with decomposition temperature less than 500 C 0.5-6.0 Sodium fluoride 0.5-1.5 4.0-6.5 Clay refractory Refractory filler10, 0-25, Binder4.0-6.0 As a reducing agent based on aluminum and magnesium the mixture according to the present invention contains a grains of an aluminum-magnesium alloy containing magnesium y ke 3,5-15,0 wt.%. The choice of an aluminum-magnesium alloy with a certain content of magnesium (3.5–15.0% Md) as a reductant is caused by the fact that magnesium contributes to the formation of a loose surface on the surface of grains, and this reduces the temperature of the onset of chemical reactions. Porosity required to reduce the onset temperature of reactions is obtained when the content of an aluminum-magnesium alloy is at least 3.5% magnesium. With an increase in the magnesium content in the alloy above 15 /)%, the flow of thermochemical reactions occurs violently, which leads to a decrease in the metal condition of the profit of heat. When the content in the mixture is less than 13.5% of an aluminum-magnesium alloy, thermochemical reactions do not proceed or proceed very slowly, which does not provide the necessary heating of the metal in profit. With an increase in the grits content of more than 18.5% of the reaction, they flow rapidly and the heat released is lost unproductively. The use of manganese ore, consisting mainly of manganese dioxide, as the main oxidant, is due to the fact that its decomposition temperature with oxygen absorption is within 620-780 s, which is significantly lower than the decomposition temperature of blacksmith or iron ore. Together with oxidants having a decomposition temperature below 500 ° C, manganese ore provides oxygen for the oxidation reactions of the reducing agent. When the content of manganese ore is less than 40.0%, the oxygen released during its decomposition is not enough for thermochemical reactions to take place. An increase in its content of more than 52.0% leads to an excess of the amount of oxygen that has passed in and to an excessively rapid thermochemical reactions. Entering into the composition of exothermic mixtures of oxidizing agents with a decomposition temperature lower than 500 ° C is due to the fact that they facilitate ignition of the mixture at temperatures that are cast in aluminum or copper. In tab. Figure 1 shows the chemical compounds that can be used as oxidizing agents with a low decomposition temperature and their decomposition temperatures. These compounds have a favorable effect on the onset temperature of thermochemical reactions when their content in the mixture exceeds 0.5%. When their content is more than 6.0%, oxygen is released quickly and by the time the reactivity of the aluminum-magnesium alloy is acquired, oxygen is removed from the reaction zone and has little effect on it. Sodium fluoride is introduced into the mixture to facilitate the destruction of the acid film on the surface of the grains of the reducing agent. In addition, its presence contributes to an increase in the binding of 1x properties of liquid glass and an increase in strength properties.

mixes. When the content of sodium fluoride is less than 0.5%, its effect on the activation of the reducing agent and the increase in the strength properties of the mixtures is insignificant, while at. an increase in its content by more than 1.5, a decrease in the strength properties of the sleeves and shells is observed.

As a refractory filler, any substances that are not directly involved in the thermochemical course can be introduced into the mixture. reactions. An example of such fillers is quartz sand, diatomaceous earth, expanded perlite, and other materials. The content of the refractory filler determines the temperature obtained during the course of thermochemical reactions. If the content of fillers is less than 10.0%, then the temperature of the reactions is high, the reaction products are obtained in a liquid state, and the effect of the exothermic mixtures on reducing the amount of profits is reduced. When zoomed. the content of fillers is more than 25.0%, the specific heat output of the mixtures is insufficient for the spontaneous thermochemical reactions in the shells and this does not allow to reduce the size of the heated bottom plates.

Refractory clay is introduced into the composition

-Mixes to obtain the necessary strength properties in the raw state. When its content is less than 4.0%, the strength in the raw state is low, and with an increase in its content of more than 6.5%, a noticeable increase in the strength in the raw state is not observed. Bentonite can be used instead of refractory clay.

Liquid glass is used as the primary binder. When the content of liquid glass is less than 4.0%, the strength properties are low, and if its content is more than 6.0%, no further increase in the strength properties is observed.

In tab. 2 shows the compositions of mixtures known and proposed.

Properties of the mixtures are given in table. 3

From the data table. 3, it follows that the proposed exosmix has a lower temperature for the onset of the thermochemical reaction and increased heat output, which increases the efficiency of the thermal work of profit in the manufacture of castings from aluminum and copper alloys.

Table

T decomposed190

240 ni “C Aluminum powder or chips Krupka from aluminum-magnesium 15.0 16.0 alloy13.5 Manganese ore 50.0 52.0 48.0 Iron ore Charcoal Sawdust 0,65 0,8 Sodium fluoride Oh, 5 Sodium nitrate 2, 0 0.5 Manganese-acid potassium 21.85 22.2 Quartz sand 24.0 Fire-resistant gly4, 0 5.0 Na5.0

380

400 535 600

Table 3.0 13-15 17.0 18.0 18.5 40.0 1080 46.0 10-15 6-12 1.01.251.5 6.04.03.0 25.0 .19.4520 5 6.46,06,5

5.0

6.0 5,04,6 4,3 Volumetric weight, kg / cm 2,15 2,21 2,24 Compressive strength in the wet state) kgf / cm 0,5 0,52 0,54 Compressive strength in dry condition; kgf / cm 16.0 18.2 17.3 Tensile strength, in a dry state, kgf / cm 4.8 4.95 4.7 Starting temperature of the prote Formula of the invention

1. Exothermic mixture for heating the profits of castings from copper and aluminum alloys, including a reducing agent based on aluminum and magnesium, an ore oxidizer, an oxygen-containing oxidizer with a decomposition temperature of less than 500 ° C, clay

Continued table. 2

4.0

1-5 30-35

15-20 2

Table 3

refractory, refractory filler and binder, characterized in that, in order to increase the efficiency of thermal work profits, it contains manganese ore as an ore oxidizer and additionally contains sodium fluoride in the following ratio of ingredients, weight. %: 2.27 2.30 0.60 0.62 Not less than 0.3 15.8 15.6 15.4 4.1 4.0 Not less than 5.0

Restorer Fia-based aluminum and magnesium. 13,5-18,5 Manganese ore. 40.0-52.0 Oxygen-containing oxidizing agent with a decomposition temperature of less than 500С0.5-6.0 Sodium fluoride 0.5-1.5 Refractory clay 4.0-6.5 Refractory filler 10.0-25.0 Binder4, 0-6.0 2. An exothermic mixture, OO Claim 1, is different in that

as a reducing agent based on aluminum and magnesium, it contains a semolina from an aluminum-magnesium alloy with a magnesium content in the semolina of 3.515.0% by weight.

Sources of information taken into account in the examination

1. USSR author's certificate No. 433957, class, B 22 O 27/06, 1972-.

2. Exothermic mixtures for heating the profits of castings from copper alloys. The compositions of the mixtures. Machine Engineering Norms MH 2689-61. Standartgiz, M., 1962.

Claims (2)

Claim 1. An exothermic mixture for heating the profits of castings made of copper and aluminum alloys, including a reducing agent based on aluminum and magnesium, an ore oxidizing agent, an oxygen-containing oxidizing agent with a decomposition temperature of less than 500 ^₽ C, refractory clay, refractory filler and a binder, characterized in that, for the purpose of increase the efficiency of the thermal work of profit, it contains manganese ore as an oxidizing agent and additionally contains sodium fluoride in the following ratio of ingredients, 65 wt. %: 81.4563 Reducer based on aluminum and NII Oxygen Manganese Ore 13.5-18.5 40.0-52.0 oxidizing agent with tempera- decomposition less than 500 ° C 0.5-6.0 Sodium fluoride 0.5-1.5 Refractory clay 4.0-6.5 Fireproof floor carrier 10.0-25.0 Binder 4.0-6.0 2. The exothermic mixture according to claim 1, characterized in that, as a reducing agent based on aluminum and magnesium, it contains grains of aluminum-magnesium alloy with a magnesium content in the grains of 3,515.0 wt.%.