Cathode hangers

A cathode for electrolytic refining or electro-winning of copper is disclosed. The cathode comprises a steel hanger bar having a copper cladding and a flat stainless steel starter sheet with a plurality of lugs formed along its upper edge secured to the hanger bar. Alternating lugs are bent, in opposite directions to abut and engage the side faces of the copper-clad hanger bar and are welded to the copper cladding. The lugs can be welded to the bar upper face or to the bar side faces and may have a stainless steel strip explosion bonded to the copper cladding interposed between the lugs and the copper cladding for welding of the lugs to the stainless steel strip.

BACKGROUND OF THE INVENTION 
This invention relates to cathode for use in the electrolytic recovery of 
copper and, more particularly, relates to cathode starter sheets formed of 
stainless steel for electrorefining or electrowinning of copper. 
The use of the cathodic stainless steel starter sheets as a replacement for 
thin sheets of high purity copper in the electrolytic recovery of copper 
is described in Canadian Pat. No. 910844 issued Sept. 26, 1972. The 
starter sheets are secured to hanger bars by means of mechanical fasteners 
such as bolts or rivets which pass through lugs formed at the top of the 
sheets. Mechanical fasteners however are prone to corrosion and may 
provide poor electrical conductivity between cathode components. 
Canadian Pat. No. 936835 issued Nov. 13, 1973, which relates to a cathode 
similar in structure to the cathode shown in Canadian Pat. No. 910844, 
discloses shrink-fitted corrosion-resistant insulating material enveloping 
the vertical side edge of the cathode plate. 
A stainless steel starter sheet is also disclosed in Canadian Pat. No. 
1150669 issued July 26, 1983. This patent discloses a stainless steel 
starter sheet welded by its upper edge to the underside of a stainless 
steel hanger bar. 
Conventional electrorefining and electrowinning plants which use copper 
starter sheets have an existing supply of iron hanger bars. In that 
stainless steel starter sheets are not easily welded to iron, mild steel 
or copper-clad bars, however, it normally is not practicable to use 
existing bars in a conversion to a stainless steel starter sheet system. 
Welding of stainless steel to copper clad iron hanger bars by conventional 
use of monel, inconel or copper (1% tin) as filler material has not proven 
successful. Both monel and copper (1% tin) welds exhibit excessive 
corrosion in the electrolyte and inconel welds cause deformation of the 
hanger bar and perforation of copper cladding to expose the core metal. 
It is an object of the present invention, therefore, to provide a novel 
re-usable cathode starter sheet of stainless steel joined to a copper clad 
iron hanger bar thereby permitting retrofit and use of existing iron 
hanger bars with substantial savings. 
It is another object of the present invention to provide a method of 
welding stainless steel starter sheets to copper clad iron hanger bars 
whereby the hanger bars are not deformed by twisting or bending during the 
welding operation so that the starter sheets will be suspended vertically 
from the hanger bars. 
A further object of the present invention is the provision of a cathode 
structure which provides good mechanical connection between the stainless 
steel starter sheets and copper clad hanger bars to enhance weldability of 
the starter sheets to the hanger bars and to provide optimum electrical 
contact therebetween. 
STATEMENT OF THE INVENTION 
In its broad aspect, the cathode of the present invention for use in 
electrorefining or electrowinning of copper comprises a steel hanger bar 
having a rectangular cross-section with flat upper and lower surfaces and 
flat opposite side surfaces, a copper cladding enveloping said hanger bar, 
said hanger bar having end portions adapted to be seated on electrical 
contacts, a flat stainless steel starter sheet having an upper edge with 
plurality of lugs formed along said upper edge, alternate lugs along said 
upper edge being bent outwardly in opposite dirctions and upwardly to abut 
and engage opposite side faces of the copper clad hanger bar, said lugs 
being welded to the copper cladding whereby said stainless steel starter 
sheet is rigidly secured to the hanger bar substantially perpendicular to 
and centrally aligned with the hanger bar lower surface. 
In a preferred embodiment of the invention, the stainless steel lugs are 
bent inwardly at their upper distal ends to overlap the upper face of the 
copper clad hanger bar for welding to the copper cladding on said bar 
upper face. 
In another embodiment of the invention, the lugs are welded to the side 
faces of the copper clad hanger bar. 
In either of the aforementioned embodiments of the invention, a stainless 
steel strip may be interposed between the alternating lugs and the copper 
clad hanger bar, said stainless steel strip being explosion bonded to the 
copper cladding and the stainless steel lugs being welded to the stainless 
steel strip. 
A copper wire or rod containing, by weight, 3.43% Si, 1.0% Mn and 0.17% Fe 
has been found to provide a good filler metal for securing the stainless 
steel lugs to the copper cladding. 
The invention will now be described in detail with reference to the 
accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIGS. 1 and 2, the embodiment of the stainless steel 
cathode illustrated therein comprises a hanger bar 10 having an iron or 
mild steel core 12 with a copper cladding 14 tightly enveloping or bonded 
to core 12 from one end of the bar to the other. Copper cladding 14 
preferably has a thickness in the range of about 2 mm to about 4 mm, 
preferably about 3 mm. 
An austenitic stainless steel plate or starter sheet 16 preferably formed 
of 316L stainless steel has a plurality of oppositely bent lugs 18, 20 
formed along its upper edge initially diverging upwardly and outwardly at 
22, 24 and then extending parallel to the plane of the sheet 16 close to 
or abutting side faces 26, 28 of copper clad hanger bar 10 to receive bar 
10 therebetween. The free or distal ends 30, 32 of lugs 18, 20 are bent 
inwardly through at least about 90.degree., preferably about 93.degree., 
for alignment of the terminus 33 of each lug substantially with the center 
line of the upper face 34 of hanger bar 10 for welding of said edges to 
the copper cladding, as depicted most clearly in FIG. 2 by fillet welds 
36. Sheet 16 thus is mechanically supported by the distal ends 30, 32 of 
lugs 18, 20 which bear on upper surface 36 of hanger bar 10 and are 
rigidly secured thereto by the welds 36 to ensure good electrical 
conductivity and to ensure that the vertical plane of sheet 16 is in 
alignment with the vertical center line of the hanger bar, depicted by 
numeral 38, and is maintained perpendicular to the under surface 40 of the 
said hanger bar. 
The opposite ends 42, 44 of hanger bar 10 extend laterally beyond the side 
edges 46, 48 of sheet 16 to permit seating of the hanger bar 10 on 
electrical support contacts in an electrowinning or electrofining cell, 
well known in the art and not shown. 
FIG. 3 illustrates another embodiment of the invention shown in FIG. 1 
wherein an intermediary stainless steel strip 44 is interposed between 
distal ends 30, 32 of lugs 18, 20 and the upper surface 34 of hanger bar 
10 along the length thereof. Strip 44 preferably is explosion bonded to 
the copper cladding enveloping bar 10 to provide a good electrical and 
mechanical contact between strip 44 and the bar 10. The distal ends 30, 32 
of lugs 18, 20 would, therefore, be welded to strip 44 by fillet welds 37, 
thus facilitating the effective welding of the sheet to the hanger bar. 
FIG. 4 illustrates another embodiment of our invention in which copper clad 
hanger bar 10 has a stainless steel sheet 50 secured thereto by means of 
lugs 52, 54 and 56 welded to the opposite side faces 26, 28 of the hanger 
bar, as shown more clearly in FIG. 5. Lugs 52, 54 and 56 have outwardly 
diverging oppositely inclined portions 58, 60 and 62, respectively 
terminating in distal portions 64, 66 and 68 which are parallel to and 
closely about the opposite side faces 26, 28 of the hanger bar 10 for 
welding directly thereto by welds depicted by numeral 74 or for welding to 
intermediary stainless steel strips 70, 72 interposed between the lugs and 
the side faces as shown in FIG. 6. Stainless steel strips 70, 72 
preferably are explosion bonded to the side faces 26, 28 of the hanger bar 
to provide good electrical and mechanical contact therewith and to 
facilitate welding of the lugs to the hanger bar by welds depicted by 
numeral 76. 
It has been found that low-temperature welds 36, 37 in the embodiments of 
FIG. 1 and welds 74, 76 in the embodiments of FIG. 4 can be made without 
warping or bending of the hanger bars and without perforation of the 
copper cladding by use of high silicon copper such as LINDE 26 (Trade 
Mark) filler wire having, by weight, 3.43% Si, 1.00% Mn and 0.17% Fe, the 
balance Cu. Welding wire having a diameter not greater than about 0.05 
inches, preferably about 0.035 inches, applied by MIG arc welding under 
100% argon shielding gas at 1.13 Cubic meters/hr applying 230 amperes at 
27 volts (+ or -5%) by a pulse power supply using a ESAB LAK Pulse-Arc 350 
(Trade Mark) machine with wire feed at 285 mm/sec (+ or -10%) provided 
suprisingly good welds which were corrosion-resistant in the electrolyte. 
The hanger bars were rigidly clamped at each end during welding and were 
substantially free of bending or twisting with flat stainless steel sheets 
secured thereto after completion of the welding operation. 
It is believed the use of staggered lugs allowed possible distortion in the 
sheets due to expansion, notwithstanding the selection of relatively 
low-temperature filler metal, to be oriented in opposite directions along 
the top of the blank and thus be effectively cancelled. The embodiments of 
FIG. 1 which have about 20 "opposed" lugs bent over the hanger bar were 
particularly resistant to distortion, the 3.degree. angle of the lug to 
the plane of the upper bar surface obviating torsional deformity of the 
stainless steel sheet. 
The present invention provides a number of important advantages. Steel or 
iron hanger bars can be used with stainless steel starter sheets by means 
of copper cladding the hanger bars and employing a novel sheet hanger 
configuration in combination with welds using copper-silicon filler metal 
to provide a warp-free structure which hangs vertically in electrorefining 
or electrowinning cells. Electrical conductivity and mechanical integrity 
of the resulting cathode structures are satisfactory and provide efficient 
electrolytic recovery of metal. 
It will be understood, of course, that modifications can be made in the 
embodiments of the invention illustrated and described herein without 
departing from the scope and purview of the invention as defined by the 
appended claims.