Stainless steel assemblies may be brazed for water and corrosive fluid services
 and for high temperature applications.  For water and fluids, silver brazing
 alloys of the AWS BAg series, as they are commonly termed, melting between
 1145 and 1600F are used.  Since the strength of the silver brazing alloys
 falls off rapidly above 500F, nickel base brazing alloys are used for high
 temperature service.  Brazing temperatures for the AWS BNi series range
 between 1700 and 2150F.

Brazing alloys are available in a wide variety of forms:  rod, wire, powder,
 sheet and strip.  There are also a wide variety of preformed shapes that are
 designed to provide the precise amount of brazing alloy required for the
 joint.  Additionally, there are brazing pastes consisting of a binder, powder
 and often a flux.

Joint design and diametrical clearance have a major influence on the strength
 of the joint.  In general, the tighter the fit, the stronger the joint.
 Clearances between 0.001 and 0.003" are normal.  Wider clearances may be
 required to insure flow in deep joints or flow with less fluid alloys.

Brazing fluxes are necessary, unless brazing is done in special furnaces with
 protective atmospheres.  The flux covers the metal surface area to be brazed,
 shielding the surface from further oxidation and reducing surface oxides.
 Removal of the oxides allows capillary action to distribute the filler alloy
 uniformly throughout the joint.  Fluxes are available in powder, liquid and
 paste form, and are compounded to melt at different temperatures.  Fluxes are
 selected to melt just below the melting point of the filler alloy so that
 they will act as temperature indicators for the correct brazing temperature.

By their nature, fluxes are corrosive and the flux residue must be removed
 from the joint immediately after brazing in order to prevent corrosion of the
 stainless steel joint.  Cleaning is done by scrubbing in hot water, by
 chemical or mechanical means, or some combination of these three cleaning
 operations.  As part of the cleaning operation, it is usually desirable to
 use an alkaline solution late in the cleaning cycle in order to neutralize
 any residual fluorides or chlorides from the flux.  Thorough cleaning of all
 flux residues is essential to prevent corrosion of brazed joints.

Common silver brazing and high temperature brazing alloys used with stainless
 steel are identified in the tables obtained from the Joining Menu.


Additional information on brazing stainless steel is available in:

   Metals Handbook, Ninth Edition, Vol. 6, "Welding, Brazing and
    Soldering", ASM Metals Park, Ohio 44073.

   Handy and Harman, 850 A 3rd Ave., New York, New York.

   Wall Colmonoy Corporation, 19345 John R Street, Detroit, MI.
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