Happenings

A.- Quality: To maintain a high standard of performance all alloys are melted and fabricated from selected raw materials under technical supervision throughout. This ensures that silver brazing alloys grades conform to their appropriate specification, not only in chemical composition, but in their freedom from harmful trace impurities and other undesirable features. In addition the research and development departments are involved in the investigation of advanced production procedures, improved methods of quality control and the development of new silver brazing and techniques.

Availability:

The alloys detailed here have been selected to give a comprehensive range of properties suitable for practically every general brazing application. Other grades can be supplied provided that the quantities justify special melting and fabrication. A wide variety of forms are available including sheet, foil, strip, rod, wire, rings, pellets, discs and washers.  

A.- Unfortunately, there is no inviolate rule which allows the most appropriate alloy to be selected and several factors may determine the choice. Main points to be taken into consideration include: size and shape of the components, parent metal composition, anticipated joint tolerances, joint configuration, heating method, heating rate strength and mechanical properties required, pressure tightness of the joint and above all, the cost of the brazing alloy.

In a limited number of cases specific requirements dictate the alloy to be used, e.g. where the need to withstand corrosive environments or high temperatures, etc. in service, over rules all other considerations.

A.- Basically because they offer a unique combination of low melting point, excellent fluidity and capillary flow when molten joints of high strength and ductility are obtained with a minimal alloy usage. The operating temperatures are around 200 C lower than those of the non-silver bearing brazing alloys, resulting in significant reduction of the brazing cycle, restricting oxidation and limiting distortion.

They are also of particular importance when heat-sensitive materials are to be joined. The silver brazing process is extremely flexible; almost any form of heating can be used to produce joints on a wide variety of parent metals.

A further important feature is their ability to form thin neat fillets requiring very little post-brazing cleaning. The combination of great strength without sacrificing ductility, coupled with low melting points and the wide range of material which can be joined, has brought silver brazing alloys into ever increasing use.

A.- Silver brazing alloys comprise a wide range of silver bearing compositions normally containing copper, zinc, phosphorous and in many cases, cadmium. For certain applications, limited additions of other elements, e.g. nickel, tin, etc. may be introduced.

These alloys exhibits high tensile strengths at room temperature 390-540 N/mm2 (25/35 tons. f/in2) with relatively low melting points (600-850 c) and are capable of joining a wide variety  of parent metals, both ferrous and non-ferrous.

This includes most commonly available engineering materials and many specialized alloys with the general exception of those melting under approximately 650 C (e.g. aluminum and zinc based alloys.)

A.- Brazing is defined as a process of joining generally applied to metals in which, during or after heating, molten filler metal is drawn into or retained in the space between closely adjacent surfaces of the parts to be joined by capillary attrition. 

In general the melting point of the filler metal is above 500º C, but always below the solids of the parent material. Brazing should not be confused with soft soldering in which the filler metals melt below 500º C. Too often silver brazing is called silver soldering which is incorrect.