RU2455140C1 - Method of making flux for soldering aluminium and its alloys - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention may be used in making flux for soldering aluminium and its alloys. Flux comprises mix of salts of potassium chloride, sodium chloride, lithium chloride, potassium fluoride, aluminium fluoride, sodium carbonate, and binding agent from polyisobutylene and white spirit. Hydrogenated salts of lithium, potassium and sodium are used at the following ratio of components in wt %: potassium chloride 20.0-21.5, sodium chloride 9.5-10.1, hydrate lithium chloride 14-16.8, bihydrate potassium fluoride 5.4-5.6, aluminium fluoride 3.0-3.8, decahydrate sodium carbonate 2.0-3.0, polyisobutylene 0.5-1.5, and white spirit making the rest. Said mix is minced, mixed and filled into graphite crucible. Said mix is heated to 800°C and cured for 4 h. Produced melt is cooled, minced, sieved through 50-150 mcm-screen and mixed with binding agent. Better homogenising and possibility to produce melt at lower temperature.

EFFECT: simplified and accelerated process.

Description

The invention relates to brazing, and in particular to methods for manufacturing fluxes for brazing aluminum and its alloys.

A method is known from the prior art for preparing a flux for brazing aluminum from potassium chloride, sodium chloride, lithium chloride, potassium fluoride, aluminum fluoride, sodium carbonate, polyisobutylene and white spirit, according to which the flux components are melted sequentially when they are introduced into the melt alternately (see ac SU 1611662, class B23K 35/24, published 07.12.1990).

The disadvantage of this method is that for the melting of the most refractory component requires a temperature above 1040 ° C, i.e. To implement the method, it is necessary to use a crucible made of heat-resistant and corrosion-resistant material, which in practice causes considerable difficulties due to the high corrosive activity of flux components for both metals (including titanium and platinum) and ceramics.

The objective of the invention is to remedy this drawback. The technical result consists in simplifying and accelerating the production of flux. The problem is solved, and the technical result is achieved by the fact that according to the proposed method for the preparation of flux for brazing aluminum using hydrogenated salts of lithium, potassium and sodium in the following ratio of components, wt.%:

salt mixture:

potassium chloride 20.0-21.5 sodium chloride 9.5-10.1 monohydrate lithium chloride 14-16.8 two-water potassium fluoride 5.4-5.6 aluminum fluoride 3.0-3.8 sodium carbonate decahydrate 2.0-3.0

binder:

polyisobutylene 0.5-1.5 White Spirit rest,

the ground salt mixture is mixed and poured into a graphite crucible, the crucible is covered with a graphite lid, the mixture is heated in the crucible to 800 ° C and held for 4 hours, then it is cooled, the melt is ground, sieved through a sieve of 50-150 microns and mixed with a binder in the form of a solution of polyisobutylene in white spirit.

According to the invention, instead of anhydrous salts of lithium chloride, potassium fluoride and sodium carbonate, lithium chloride monohydrate (monohydrate), potassium fluoride, two-water and sodium carbonate decahydrate are used. Instead of sequential melting of the components, it is proposed to co-heat the mixture (which speeds up production), while a homogeneous melt is obtained even at a temperature of 750-800 ° C. These differences are due to the fact that when the mixture is heated, partial dissolution of the components in crystallization water occurs (with further heating, the water evaporates), which improves the homogenization of the mixture and allows melt to be obtained at a lower temperature. Thus, it becomes possible to use graphite crucibles that do not contaminate the flux with corrosion products, and production is simplified. The specified ratio of components and the dispersion of the melt provide the necessary activity and homogeneity of the flux.

The flux is prepared as follows:

1. Prepare a binder by dissolving polyisobutylene in white spirit.

2. Prepare a mixture of salts, for which grind the packed lumps of salts, weigh and mix thoroughly, pour the resulting mixture into a graphite crucible, cover the crucible with a graphite lid.

3. Set the crucible in the muffle furnace, set the heating temperature to 800 ° C.

4. Heat the mixture of salts to the indicated temperature, hold for 4 hours, cool with the oven.

5. Remove the melt, grind, sift through a sieve of 50-150 microns.

6. Mix with a solution of polyisobutylene.

The flux obtained by this method allows reliable soldering of structural products from aluminum and its alloys.

Claims (1)

A method of preparing a flux for brazing aluminum and its alloys containing a mixture of salts of potassium chloride, sodium chloride, lithium chloride, potassium fluoride, aluminum fluoride, sodium carbonate and a binder of polyisobutylene and white spirit, characterized in that hydrogenated salts of lithium, potassium and sodium in the following ratio of flux components, wt.%:
potassium chloride 20.0-21.5 sodium chloride 9.5-10.1 monohydrate lithium chloride 14-16.8 two-water potassium fluoride 5.4-5.6 aluminum fluoride 3.0-3.8 sodium carbonate decahydrate 2.0-3.0 polyisobutylene 0.5-1.5 White Spirit rest,
the ground salt mixture is mixed and poured into a graphite crucible, the crucible is covered with a graphite lid, the mixture is heated in the crucible to 800 ° C and held for 4 hours, then it is cooled, the melt is ground, sieved through a sieve of 50-150 microns and mixed with binder in the form of a solution of polyisobutylene in white spirit.