RU2506147C2 - Pelletised iron-aluminium thermit - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to thermit welding and can be used for production of thermit iron from iron oxides. Iron-aluminium thermit is produced as pellets using nitrocellulose as a binder containing the following components, in wt %: aluminium - 21-23, iron oxide - 72-74, nitrocellulose - 2-6, Novolk flux - 0.3-1.0. Thermit ensures smooth combustion reaction without spread of initial mix.

EFFECT: improved metal phase separation from slag, higher yield of pure metal.

2 dwg, 1 tbl

Description

The invention relates to the field of thermite welding. The invention can also be applied to processes associated with obtaining pure iron from its oxides.

The known composition of termite, consisting of aluminum 65-75%, iron oxide 15-25% and graphite 7-15% [1].

However, this composition is characterized by a high ignition temperature, low yield of termite metal and difficulties in the separation of slag.

As the closest prototype of the claimed invention adopted aluminum termite containing aluminum 20-22%, iron oxide 60-63% and aluminum oxide 15-20% [2].

The disadvantage of this composition is the poor phase separation of the metal from the slag.

The technical result, the solution of which the present invention is directed, is to improve the phase separation of metal from slag and increase the yield of pure metal.

The required technical result is achieved by the fact that the iron-aluminum termite containing aluminum 21-23% and iron oxide 72-74%, according to the authors, is obtained by forming a thermite mixture in the form of granules, while it contains a synthetic binder nitrocellulose in an amount of 2-6% and Nocolok flux in an amount of 0.3-1.0%.

The proposed composition of granular iron-aluminum termite is used to obtain metal in plants designed to ignite the termite from below. Granulation significantly increases the gas permeability of the thermite mixture and when ignited from below it does not give rise to a flame and eliminates the spread of the thermite mixture and its combustion products.

To prepare the termite, powders of aluminum and iron oxide are used in a mass ratio of 1: 3. The mass fraction of the binder (on dry weight) is 2-6%, and the mass fraction of flux is not more than 1% of the total termite mass.

To prepare the termite, a 10% solution of nitrocellulose in acetone is used, which is mixed with powders of aluminum, iron oxide and flux. After partial evaporation of the solvent, granules of 5-7 mm in size are made from the mixture by wiping through a net, which are dried until the solvent is completely removed.

To obtain granules, it is necessary to introduce at least 2 weight percent nitrocellulose into the mixture.

The binder content in an amount of from 2% to 6% in the granules of the initial charge does not significantly affect the reaction rate, however, with an increase in its content, the rate increases slightly.

The introduction of a binder in an amount of more than 6 weight percent is not advisable if the task is not to obtain granules of special strength.

Table 1 shows examples of termite compositions indicating the ingredients included in their composition.

Table 1 Examples of termite compositions Structure
Property Composition number 1 Composition number 2 Composition number 3 Composition No. 4 Aluminum% 21 23 22 23 Iron oxide,% 73 74 73 72 Nitrocellulose,% 5.7 2,3 4.3 4.0 Flux Nocolok,% 0.3 0.7 0.7 1,0 Mass burning rate, g / s 4.7 4.1 4.4 4.0

The combustion of granular iron-aluminum termite using nitrocellulose as a binder is characterized by a quiet reaction and the absence of a spread in the initial mixture and reaction products.

Figure 1 shows the effect of nitrocellulose content on the mass burning rate of a granulated thermite mixture.

Nocolok flux is a eutectic mixture of potassium fluoroaluminates KAlF ₄ and KAlF ₆ and is used for brazing aluminum alloys.

The flux content significantly affects the burning rate, reducing it with an increase in the flux content. The amount of flux should not exceed 1%, since this significantly increases the likelihood of stopping the reaction. The recommended flux content is 0.5% by weight of the mixture.

In figure 2. The effect of the Nocolok flux content on the mass burning rate of a granulated thermite mixture is shown.

In addition to influencing the reaction rate, Nocolok flux reduces the ignition temperature, improves the phase separation process and increases the yield of pure metal.

The proposed set of essential features is not known from available sources of information of the prior art, from which it is not obvious for a specialist in thermite welding, and can be serially reproduced in production, that is, meets the criteria of patentability.

Literature

1. A.S. USSR No. 508362, publ. 10/17/1973, class B23K 23/00.

2. A.S. USSR No. 475234, publ. 04/10/1972, class B23K 23/00.

Claims (1)

An aluminum-aluminum termite containing aluminum and iron oxide, characterized in that it is obtained by forming a thermite mixture in the form of granules, while additionally containing a synthetic binder nitrocellulose and Nocolok flux in the following ratio, wt.%:
Aluminum 21-23 Iron oxide 72-74 Nitrocellulose 2-6 Gumboil Nocolok 0.3-1.0

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