GB1558673A - Brazing alloys - Google Patents

Description

(54) BRAZING ALLOYS (71) We, THE SHEFFIELD SMELTING COMPANY LIMITED, of P.O. Box 28, Royds Mills, Windsor Street, Sheffield S4 7WD, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to brazing alloys.

It is advantageous to employ in the brazing of metals a brazing alloy having a relatively low melting point and for this reason, silver alloys containing copper, zinc and cadmium are conventionally used since such alloys may have melting points as low as about 600"C. However these cadmiumcontaining silver brazing alloys can produce toxic hazards by virtue of the presence therein of cadmium. To avoid this disadvantage, it has recently been proposed, in United States Patent No. 3,862,838, to use as a brazing alloy a silver alloy containing copper, zinc and optionally tin but no cadmium. We have found, however, that whilst such cadmium-less brazing alloys normally exhibit favourable brazing characteristics, they are nevertheless not satisfactory when applied to assemblies with rather poorly fitting joints, that is their gap filling properties are inadequate.

It is an object of the present invention to provide a brazing alloy which will exhibit adequate gap filling properties with both ferrous and non-ferrous metals.

We have surprisingly found that by incorporating both tin and nickel in specific proportions in a silver brazing alloy containing copper and zinc, good gap filling properties of the brazing alloy may be obtained whilst maintaining the melting range and general brazing characteristics of the alloy.

Thus in accordance with the invention there is provided a brazing alloy consisting, of apart from impurities, from 25 to 55 weight percent of silver, from 20 to 40 weight percent of copper, from 20 to 35 weight percent of zinc, from 0.1 to 5 weight percent of tin and from 0.1 to 5 weight percent of nickel.

Advantageously the brazing alloy consists of 40 to 50% silver, 20 to 30% copper, 25 to 30% zinc, 1 to 3% tin and 0.5 to 3% nickel.

The following Examples illustrate brazing alloys in accordance with the invention.

EXAMPLE 1 A brazing alloy was produced having the following composition:- by weight Silver 45% Copper 25% Zinc 26% Tin 2% Nickel 2% The foregoing brazing alloy is ductile and may be fabricated in any of the various forms conventionally employed for silverbrased brazing alloys. It has a melting range of 665 to 725"C. and is capable of providing joints made in ferrous or non-ferrous metals which have improved high temperature strength compared with silver-based brazing alloys containing no nickel.

EXAMPLE 2 A brazing alloy was produced having the following composition: by weight Silver 45% Copper 25% Zinc 25.5% Tin 3% Nickel 1.5% This alloy has a melting range of 635 to 710"C.

EXAMPLE 3 A brazing alloy was produced having the following composition: by weight Silver 50%, Copper 21.5 Zinc 27% Tin 1% Nickel 0.5% This alloy has a melting range of 660 to 680"C.

WHAT WE CLAIM IS: 1. A brazing alloy consisting of, apart from impurities, from 25 to 55 weight percent of silver, from 20 to 40 weight percent of copper, from 20 to 35 weight percent of zinc, from 0.1 to 5 weight percent of tin and from 0.1 to 5 weight percent of nickel.

2. A brazing alloy as claimed in Claim 1, consisting of 40 to 50% silver, 20 to 30 ," copper, 25 to 30% zinc, 1 to 3% tin and 0.5 to 3% nickel.

3. A brazing alloy as described in the foregoing Example 1.

4. A brazing alloy as described in the foregoing Example 2.

5. A brazing alloy as described in the foregoing Example 3.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. EXAMPLE 3 A brazing alloy was produced having the following composition: by weight Silver 50%, Copper 21.5 Zinc 27% Tin 1% Nickel 0.5% This alloy has a melting range of 660 to 680"C. WHAT WE CLAIM IS:

1. A brazing alloy consisting of, apart from impurities, from 25 to 55 weight percent of silver, from 20 to 40 weight percent of copper, from 20 to 35 weight percent of zinc, from 0.1 to 5 weight percent of tin and from 0.1 to 5 weight percent of nickel.

2. A brazing alloy as claimed in Claim 1, consisting of 40 to 50% silver, 20 to 30 ," copper, 25 to 30% zinc, 1 to 3% tin and 0.5 to 3% nickel.

3. A brazing alloy as described in the foregoing Example 1.

4. A brazing alloy as described in the foregoing Example 2.

5. A brazing alloy as described in the foregoing Example 3.