RU1780969C - Copper and copper-base alloy solder flux - Google Patents

Abstract

Usage: soldering copper and its alloys. SUMMARY OF THE INVENTION: The flux contains the following components, May. %: ammonium chloride 12-14; sodium tetrafluoroborate 29.2 - 33.5; potassium tetrafluoroborate 10.2-11.7; sodium tetraborate 8.8-9.4; zinc chloride the rest. 2 tab.

Description

The invention relates to brazing, in particular, to the composition of a flux for structural brazing of copper and its alloys with lead-based solders.

For the low-temperature brazing of copper and its alloys, a large number of organic fluxes are used, for example, PDFs, FKSp, LTI-120 and others, but the maximum temperature of their activity is limited by carbonization of organic substances or the interaction of acids with metal and transition to salts at temperatures above 270 - 350 ° C. Fluxes dramatically lose activity. Soldering (at a melting point of 300-350 ° C) is difficult and sometimes impossible.

Of the fluxes having industrial applications, the most acceptable flux FDFS.

Flux PDFs is highly corrosive and is recommended for soldering in the temperature range 200-350 ° C. The lack of flux PDFs composition, wt.%:

Orthophosphorna

acid (density 1.7) 20 - 25

Acid sol

diethylamine 20 - 25

Ethylene Glycol

it is that at temperatures 270 - a decline in activity begins. The decrease in flux activity occurs due to:

a) transforming orthophosphoric acid into meta- and polyphosphoric acids, which are less active in brazing processes, at a temperature above 200 ° C, reacting them with a soldered metal to form phosphates and thickening with transfer to anhydride;

b) decomposition of ethylene glycol (Bp + 200 ° C) and its binding to polyphosphoric acids and intensification of the thickening process in the range of 250-300 ° C;

c) the interaction of diethylamine hydrochloride with the base (soldered) metal above 220 ° С, orthophosphoric acid and it. products interacting with soldered metal and solder.

All the above interactions of the components of the flux in the soldering process

h

00

about y about y

this leads to the fact that at temperatures above 300 ° C the flow of the solder into the gap worsens while maintaining a sufficiently bright surface of the solder due to carbonization of the organic component of the flux and the oxidation of the solder by carbon.

The closest in technical essence to the claimed flux is the flux of the composition, wt.%:

KF20 - 25

V20z10-18

Cdcl25-13

NaCI4-10

Eutectic

Na2B40y + KBF4 45-60 designed for high temperature brazing of copper and nickel alloys. It is highly active, water soluble, corrosive with a temperature range of activity of 430-650 ° C and is intended for soldering with solders with melting points of 450-650 ° C. But this flux is not suitable for soldering with lead solders with a melting point of 280 to 350 ° C.

The aim of the present invention is to provide a flux with a temperature range of activity of 330-450 ° C and increased heat resistance during the soldering process.

This goal is achieved by the fact that in the flux (prototype), instead of boric anhydride, potassium fluoride and cadmium chloride, sodium tetrafluoroborate is introduced in the form of a ternary eutectic mixture NaBRi - KBRi - -NaaBO. As the chlorine-containing components, a ZnCte-NH4CI eutectic mixture was used in the following component ratios, wt.%:

Ammonium chloride 12.4 - 14.0 Sodium boro-fluoride 29.2 - 33.5 Potassium boro-fluoride 10.2 - 11.7 Sodium tetrabo-acid 8.2 - 9.4

Zinc Chloride

The flux has a temperature range of activity of 330 - 450 ° С and provides high-quality soldering with lead solders of ПСр1.5 grades. PSr2.5 and others, copper and its alloys; can be used for soldering in furnaces and gas burners.

The introduction of sodium tetrafluoroborate into flux, forming potassium tetrafluoroborate and sodium tetraborate, a low-melting eutectic with a ratio of components, wt.%: 61.3 NaBF4; 21.5 KBF 17.2 N22840 and a melting point can reduce the temperature range of the flux activity (proto-ip) while maintaining fluidity.

With a eutectic content of less than 47.6% (NaBF4 29.2%; KBF4-10.2%; Na2B407-8.2%), the flux activity decreases, with a eutectic content of more than 54.6% (NBF / j33, 5%; KBF4 - 11.7%, No. 2840 -9.4%) the flux delaminates during melting, the corrosion of the surface increases at high activity, the smooth solder flow line is disturbed,

0 Zinc chloride in an amount of 33 - 36.5 wt.% Promotes better wetting of the surface of copper and copper alloys with molten solders while maintaining the uniformity of the molten flux. At

5 higher zinc chloride flux smokes. Below 33%, the flow of solder in the metal becomes uneven.

When the content of ammonium chloride

0 below 12.4% the flux loses homogeneity in the molten state, above 14.3% it smokes heavily (decomposes). Violation of the eutectic ratio with zinc chloride (27.3 wt.% NH4CI, 72.7% ZnCte)

5 leads to a deterioration in the flux property: when the NH4CI content is less than eutectic, the surface will gain luster, which indicates poor spreading. When NhMCI is higher than eutectic-flux

0 smokes, ter uniformity during melting.

In order to test the properties of the flux, 5 formulations were tested that differ in substance content. The compositions of Iss5 investigated fluxes are given in table. 1. The chemical composition of the options for flux F400 are presented in table. i.

The criterion for assessing the activity of this flux is the solder spreadability coefficient (PSr1.5, PSr2.5, PSKVi86) along the soldered surface and viability. The measurement results are presented in table. 2. The coefficient of spreadability of the holes on copper and brass at 400 ° C is given in table. 2.

5 The use of the proposed flux provides high-quality structural soldering in the temperature range 330 - 450 ° C using lead solders melting at 270 - 350 ° C

0 on products made of copper, brass and other copper alloys, expands the possibility of step soldering in the manufacture of complex parts.

Improving the wettability of soldered surfaces provides high quality soldering, higher strength characteristics of the solder joint. So, for example, copper butt joints, brazed with PSr1.5 solder with flux PDFs at 330 - 350 ° C, showed a tensile strength of 51.78

MPa on copper and 55.11 MPa on brass. Samples brazed with the same solder with the proposed flux showed a strength of 63.35 MPa on copper and 67.95 MPa on brass.

After corrosion tests, the strength of the soldered joints with FFFS flux 45.79 MPa and 35.3 MPa, respectively, with the proposed flux 63.15 MPa and 65.12 MPa. Gas-flame soldering with PSr2.5 solder with the use of flux PDFs is impossible, and with the proposed one it provides strength on copper of 52.27 MPa, and on brass - 56.88 MPa.

Brazing in a furnace provides less porous, stronger solder joints.

The good solubility of the flux components provides ease of removal of flux residues after tinning and brazing.

Metallographic studies have shown that lower porosity, better flow into the gap and a greater spreading coefficient are provided by using fluxes of compositions 2, 3, 4. Solders have a strong metallic luster, which indicates a good deoxidation of their surface.

For fluxes of compositions 2, 3, 4, the activity range is 330-450 ° C. At heating temperatures above 450 ° C, the fluxes thicken and the soldered copper surface is oxidized.

The developed flux is water soluble, corrosive. Flux residues are easily removed after soldering by rinsing in hot and cold water.

The proposed flux provides high-quality brazing of copper and its alloys with lead-silver solders in the temperature range 330 - 450 ° C for 10-15 minutes.

In technology, the economic effect when applying the invention is expressed in obtaining high-quality solder joints when using solders of the ПСр1.5, ПСр2.0, ПСр2.5ТТ1СрЗ grades and increasing the product service life during operation in the temperature range 200 - 270 ° С, increasing the corrosion resistance of steam compounds

Claims (1)

Formula of the invention A flux for brazing copper and its alloys containing a eutectic mixture of zinc and ammonium chlorides, characterized in that, in order to achieve a temperature range of activity of 330-450 ° C and to increase the heat resistance of the flux during brazing, it further comprises a eutectic mixture of potassium tetrafluoroborates , sodium and sodium tetraborate in the following ratio, wt.%: Ammonium chloride 12.4 - 14.0 Sodium tetrafluoroborate 29.2 - 33.5 Potassium tetrafluoroborate 10.2-11.7 Sodium tetraborate 8.8 - 9.4 Zinc Chloride Table 1 table 2