An Improved Solder for Aluminium.
Year: 1892

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by J. W: RICHARDS, Metal Refiner and Dealer,
Delaware Metal Refinery, 18th Washington Avenue, Philadelphia, Pennsyl-
vania, U.S.A.]
An Improved Solder for Aluminium.
WILLIAM ARCHIBALD BRIGGS Chemical Engineer 4 Erskine Terrace Dundee
Scotland, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
A certain new and useful solder for aluminium surfaces whereof the following
is a Specification. Heretofore much difficulty has been experienced in soldering
aluminium surfaces to one another, or to other metals, owing to the fact that with
the solders heretofore used; a film of oxide persistently forms with such rapidity
that the solvents or fluxes used, fail to thoroughly eliminate it. Even though
the film of oxide is exceedingly thin; in fact imperceptible to the eye, it prevents
the perfect union of the solder with the metal, and hence impairs the closeness &
strength of the joint. I have found that by diffusing throughout the solder itself.
a deoxidising or reducing agent of the proper character, and thus subjecting the
aluminium surfaces to the action of such reagent during the period of actual
contact with the melted solder, deoxidation can be effected as part of the act of
soldering, and hence no opportunity is afforded for the formation of a new film of
oxide. The deoxidising or reducing agent should be one which under the conditions
of use has a greater affinity for oxygen than is possessed by the other ingredients
of the solder, and whose oxide is not liable to form a film or otherwise interfere
with the integrity of the soldered joint. The reagent which I have found most
desirable for this purpose is phosphorus, which when present in a proper solder
even as a minute percentage suffices to effect the reduction of the oxide in the
manner above indicated. The compound which I have found best adapted to act
both as a vehicle for the reducing agent and as a solder also, is an alloy of
aluminium, zinc, & phosphor tin and I prefer to prepare the same as follows:-
I melt one part (by weight) of metallic aluminium in a suitable crucible, and
then add thereto eight parts of zinc. In a separate crucible, I melt thirty two
parts of tin, and add to it one part of five per cent. (5%) phosphor tin so as to
reduce the percentage of phosphorus therein. I then pour the diluted phosphor-tin
into the melted alloy of zinc & aluminium. 'Stir well, & as soon as the compound
is homogenous, I pour it into suitable bars for use. The proportions above given
are those which I have found most suitable for general use, either with a blowpipe
or an ordinary soldering iron; but they may be varied with the following results :-
viz., an increased percentage of tin will give a lower melting point, whilst an
increased percentage of aluminium and zinc will make a stronger solder.
While I have given the above formulæ as indicating the best embodiment of my
invention known to me, I do not limit myself to the use of phosphorus or phosphor-
tin; nor in case of these ingredients for the solder do I limit its composition to
the precise proportions above mentioned, since it will possess the qualities which
make it specifically useful in this connection whenever the deoxidising reagent is
present in sufficient quantity to deoxidise the surfaces during the soldering, even
though the proportions of the ingredients be varied. Furthermore the above
described method of preparing the solder is not to be understood as essential, but
is simply indicated as convenient, because the five per cent. phosphor-tin is readily
obtainable in the market and is easily diluted in the manner specified.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
--
1. As a solder for aluminium, an alloy of aluminium and zinc having incor-
porated therein a reducing agent whose affinity for oxygen is greater than that of
aluminium or zinc under the conditions of use, and whose oxide is substantially
non-film-forming.
2. As a solder for aluminium, an alloy of aluminium, zinc, & phosphor-tin,
substantially as set forth.
W. A. BRIGGS.