Improvements in or relating to the Joining of Pieces or Articles of Aluminium or Aluminium Alloy.
Year: 1899

page_text: Date of Application, 4th Dec., 1899-Accepted, 27th Jan., 1900
Improvements in or relating to the Joining of Pieces or Articles of
Aluminium or Aluminium Alloy.
We, MAX SCHMIDT, Manager, and GESELLSCHAFT FÜR ELEKTRISCHE METALL-
BEARBEITUNG, G. m. b. H., both of Leipziger Strasse, 101-102", Berlin, Germany,
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:-
It has heretofore been usual, when soldering or welding aluminium, to remove
the oxide formed on the parts to be united, either by dissolving the said oxide
or converting it into a fusible slag with the aid of a reducing flux. Although such
chemical cleaning of the metal may suffice for soldering purposes when the solder
is of suitable composition, it is found to be insufficient at the high temperature
required for welding. Sometimes in the welding of aluminium pieces
aluminium alloy, liquid aluminium has been poured into the seam between the
surfaces to be united after the said surfaces have been chemically treated.
.
or
Now this invention has for object to effect the joining of pieces of aluminium or
aluminium alloy without the necessity of employing a reducing flux either alone
or in conjunction with the addition of liquid metal.
For this purpose, after heating the surfaces to be united to a suitable tempera-
ture, a solid body of high fusion point is inserted between the said surfaces, and
caused to engage frictionally therewith. By moving the said body along the seam
in such frictional engagement, the thin layers of oxide or oxide and slag formed
on the surfaces of the metal are removed, and clean surfaces produced for the
welding which may be effected without pressure or hammering.
Instead of employing only one solid body, more than one such body may be
employed, particularly in cases where the surfaces to be joined are large
To avoid injury to the metal surfaces during the removal of the oxide, the
solid body should be as smooth as possible where it will come in contact with the
surfaces in question; the said solid body may conveniently be in the shape of a
stick or rod. Rods made of compressed carbon or platina are suitable for this
purpose.
Metals of high fusion point, as, for instance, iron, which would have an
injurious effect on the aluminium or aluminium alloy, are unsuitable for the
purpose. Metal which easily form alloys with aluminium should also be avoided,
except in cases where it would not be objectionable for the seam to contain such
alloys. The method just described may, if desired, be used in conjunction with a
chemically reducing treatment. In the mechanical process, the operative surface
of the frictional body or tool soon becomes rough in consequence of the adhering
oxide, but in order to obtain good results, it is necessary that the said tool be
kept smooth and pointed. Accordingly, we sometimes supplement the mechanical
method hereinbefore described by an electrolytic action so that the oxidation
products, or part of them, are decomposed, and the oxygen liberated by such

page_text: decomposition, together with the undecomposed oxidation products, are removed
mechanically.
In carrying out this part of the invention, the tool is connected to one pole of a
source of electricity the other part of which is connected to a conducting support
on which the pieces or articles to be united are placed, the connections being such
that the tool will constitute the anode and the articles to be joined constitute,
partly or wholly, a divided cathode, so that the metal liberated by the decomposi-
tion of the oxide can be utilised in the welding whilst the oxygen simultaneously
liberated at the anode will be either mechanically removed as such, or as an
oxidation product of carbon.
In order to avoid formation of electric arcs at the moment of making or breaking
contact, the current employed is of low potential, and large in quantity so as to
obtain considerable heating effect. Although the electrolytic method may not
effect the complete decomposition of the aluminium oxide, the quantity of this
substance present will be lessened, and the welding also facilitated, as a result of
the increased temperature produced by the current.
When employing the mechanical process only, the tool should be so operated as
to produce friction on the metal surfaces, but in the case of the electrolytic process,
it is sufficient merely to draw the tool along the seam or joint, without appreciable
pressure.
The accompanying illustration represents diagrammatically, apparatus used for
welding electrolytically according to this invention.
A and B represent the parts to be welded together, and C the seam produced by
placing together the edges to be united, which edges have been jumped, upset, or
thickened, in order that the joint may be subsequently hammered after welding
without unduly thinning it. "D represents the support which is provided with a
groove E to enable the joint or parts adjacent thereto to expand downwards under
the action of the heat and any pressure by which the parts may be forced together.
F represents the tool which may be drawn through the seam, by mechanical
means or by hand. G represents the source of electricity, and H, a rheostat. The
arrows J indicate the direction of the current, and the arrow K, the direction
of movement of the tool. For any further heating of the edges to be united that
may be necessary, any known and suitable source of high temperature, as, for
example, the oxy-hydrogen flame, or electric arcs, may be utilized, and may
serve either to heat the surfaces to be welded by direct contact therewith or by
indirect means. In the latter case, the source of heat is applied to the tool which
is thus raised to and maintained at a sufficient temperature, and is also of such
shape and nature as to convey the heat to the seam; the tool may be a platinum
rod which is pointed at one end but is above the point so thick that it can take up
the necessary heat. Such indirect heating is particularly advantageous when the
source of heat is stronger than desirable, as, for instance, when welding thin
plates. The tool must, in such cases, be composed of non-fusible material, as, for
example, alloys of platinum.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, we declare that what
we claim is:-
1. In the uniting of surfaces of aluminium or aluminium alloy by fusion,
freeing the said surfaces from oxide or slag or both by the frictional action of one
or more smooth tools of refractory material, substantially as set forth.
2. In the uniting of surfaces of aluminium or aluminium alloy by fusion,
cleansing the surfaces to be united by means of the electrolytic decomposition of
some or all of the oxide present, whether or not in combination with the frictional
action of one or more smooth tools of refractory material, substantially as set forth.
3. In the uniting of surfaces of aluminium or aluminium alloy by fusion,
freeing the said surfaces from oxide or slag or both by means of a tool or tools

page_text: of refractory material and the indirect heating of the surfaces through the medium
of the said tool or tools, substantially as set forth.
4. Electrolytic apparatus for effecting the union of pieces of aluminium, or
aluminium alloys constructed, arranged, and operating as hereinbefore described
with reference to and shown in the accompanying drawing.
ecem
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.
Dated this 4th day of December 1055.
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.