SU764909A1 - Method of making boron-fluoride fluxes - Google Patents

Description

The invention relates to soldered production, in particular, to methods for producing boron fluoride fluxes, used mainly for brazing stainless steels, as well as for heat-resistant and copper alloys with silver solders.

A known method for producing boron fluoride fluxes containing cadmium U potassium fluoride and boron anhydride by mechanical mixing of previously prepared dehydrated components fll.

The disadvantages of this method are the lack of homogeneity of the mixture and the need for separate preliminary preparation of all components of the fluxes, which reduces the productivity of their manufacture. 20

A known method for producing boron fluoride fluxes by mixing substances containing elements or ions, optionally. required to form flux components. In order to increase the homogeneity of the flux and reduce its cost, the starting materials are mixed in an aqueous solution, and the components of the flux formed as a result of a chemical reaction are isolated by drying the solution. Jq

In order to obtain boron fluoride fluxes containing potassium fluoride, potassium borfluoride and boric anhydride, the required amount of hydrofluoric acid is mixed with the whole amount of boric acid necessary to produce potassium fluoride, potassium borfluoride and boric anhydride by a known method. The resulting acid solution is neutralized with potassium hydroxide, the suspension is dehydrated, and the mixture is ground 2.

The disadvantage of the known method is the inconsistency of the phase composition of the mixture obtained with the phase composition of the fluxes indicated in the recipe, which adversely affects the quality of the soldering. In the preparation of the flux, all the co-mixes simultaneously. The amount of hydrofluoric and boric acids needed to produce potassium fluoride, potassium fluoride and boric anhydride, i.e. boric acid is taken in excess from the required hydrofluoric acid to produce hydrofluoric acid, in which case the reaction of hydrofluoric acid and boric acid leads to

HBF, large amounts of hydroxy acids 3.

After neutralization of the acid solution with potassium hydroxide, a mixture is formed, which is made of hydroxy acid derivatives and, in a small amount, potassium fluoride and potassium fluoride. As a result, after drying the mixture, a flux is obtained that does not correspond to the phase composition indicated in the recipe.

The purpose of the invention is to create a method for manufacturing boron fluoride fluxes that improve the quality of soldering by ensuring that the phase composition of the flux corresponds to the prescription one. This goal is achieved. We can say that boric acid is injected in an amount necessary to produce potassium bortofluoride, and the rest of it is obtained after neutralizing the solution.

The presence of an excess of hydrofluoric acid in the solution at the stage of the interaction of hydrofluoric and boric acids contributes to the rapid and complete formation of boron fluoride ion, and at the stage of neutralization with caustic potassium, due to the strong salting out effect, potassium fluoride is quantitatively solid. Upon completion of potassium boron fluoride release, neutralization of excess hydrofluoric acid occurs to form potassium fluoride. The resulting mixture of boron fluoride and potassium fluoride is injected with the remaining amount of boric acid to form boric anhydride upon drying. Since neither potassium fluoride nor potassium boron fluoride interact with boric acid to a temperature of 400-450 ° C, when the mixture is dried, the phase composition of the resulting flux does not change and corresponds to that specified in the recipe. The method is carried out as follows.

A calculated amount of hydrofluoric acid is poured into the viniplast tank or reactor, while maintaining the temperature at 10 -, boric acid is added, taken as the basis for obtaining the required amount of potassium fluoride fluoride. After the addition of boric acid, the mixture is stirred for 2-4 hours at room temperature. Then within 2 to 8 hours the solution is neutralized with a calculated amount of potassium (the final pH of the solution is 7 and boric acid is loaded to form the required amount of boric anhydride. The resulting suspension is discharged into a steam heated mixer and dried. Dry

The product is calcined in a rotary kiln at 300 -.

According to chemical, thermographic, and X-ray phase analyzes, the product is a mixture of potassium fluoride, potassium fluorosporic and boric anhydride without admixture of other phases.

Example. To obtain 100 kg of flux 209 (formulation, wt.% KBF 23 + 2, KF 42 + 2, 35 + 2), 72.5 kg of 40% hydrofluoric acid, 73.7 kg of 95% boric acid and 53.5 kg of 95% caustic potash.

In the gummed reactor 500 l, pour 72.5 kg of hydrofluoric acid, cool to 10-15 ° C and, maintaining this temperature, load 11.3 kg of boric acid. The solution is kept under stirring for 2 hours, then neutralized for 2-2.5 hours with 53.5 kg of 95% sodium hydroxide, adding it in small portions until.

The suspension consisting of calipho-fluoric acid and potassium fluoride is stirred for 0.5 h and the boric acid residue (62.4 kg) is charged. The mixture is agitated for about 5 hours and discharged into a steam-heated mixer. Packing and drying is carried out at 120-130 ° C to obtain a dry, crumbly powder, which is then calcined in an oven at 300-350 ° C and crushed,

The elementary and phase compositions of the obtained flux are given in table. one.

EXAMPLE 2. To obtain 100 k of the flux 284 (formulation, wt.% KBFt, 40 + 2, KF 35 ± 2, 25 + 2), 93.6 kg of 40% hydrofluoric acid, 64, 3 kg of 99.5% boric acid and 54.2 kg of 95% potassium hydroxide.

Under the conditions of Example 1, 93.6 kg of hydrofluoric acid and 19.7 kg of boric acid were successively introduced into the solution. The mixture of the resulting acids agitates for 3.5 hours and 54.2 kg of potassium hydroxide is neutralized, and then 44.6 kg of boric acid are added. After drying, evaporation and calcination, a flux was obtained corresponding to the elemental and phase compositions (see Table 1).

Chemical methods for producing fluxes are much more economical than methods for producing fluxes by mechanical mixing, since cheaper reagents are used to prepare fluxes (see Table 2).

The proposed method does not require further development; it has been tested in laboratory and industrial conditions.

Table

Flux 209 According to the proposed method 35.2 12.8 28.0 Ost. According to well-known35, 1 12.9 27.8 Ost. By mixing the initial components, 35, 3 12.8 27.7 Ost. comrade

Flux 284

By the proposed method 36.0 11.1 35.7 Ost. According to known35, 7 11.2 35.7 Ost. Nomu by mixing the original components, 36, 0 11.3 35.6 Ost. comrade

x)

Note: the rest is hydroxy acid derivatives. Note:

40.3 34.9 24.8

Table2, the anhydrous KF consumption is 0.42 tons, the table shows the consumption KF 2HjO 0.68. Since anhydrous KF is not produced by the industry, the cost of dehydration is not included in the table. 23.2 41.9 34.5 13.5 27.0 8.5 3.0 42.0 35.0 32.5 25.0 7.6 40.0 35.0 25.0

Claims (3)

1.Lashko N.F., Lashko S.V. The ration of metals. M., Mechanical Engineering, 1967, p. 275. 2.Vulik A.I., Statsenko A.A., Makovetsky M.I., Mimsky S.A. Industry of chemical reagents. M., IREA, 1963, p. 18. 3.Ryss IG Chemistry of fluorine and its inorganic compounds. M., State Chemistat, 1956, p. 444-455.