TITLE: A novel method for developing nano-particle coated highly conductive electrode
wire.
FIELD OF INVENTION:
This invention relates to a novel method for developing nano-particle coated highly
conductive electrode wire.
Such electrodes are produced by the newly developed technology of binary composite
metallic ion deposition or nano-blanketing with metallic ions on the micro-structure of
the electrode wire.
BACKGROUND OF THE INVENTION:
The conventional industrial practice is to use a copper coating over wire electrode to get
the properties of conductivity, feedability and corrosion resistance required for welding.
However, despite its many advantages the copper plated wire has many drawbacks [1,2,
3]. The melting point of copper is 1083°C and it vaporizes easily at ultra high
temperature during welding operation generating copper fumes which pose a health
hazard. A few studies of the metal transfer mode during welding process using high
speed camera have revealed that a copper-coated wire droplet is not in spherical form but
is in the form of an ellipsoid which is elongated along the droplet transfer direction. Due
to a higher surface tension caused by the presence of copper a reduction in the diameter
of the droplet is not possible. This causes instantaneous short circuit between droplet and
molten pool and results in an increased spatter generation. Furthermore, the copper
plating is softer than the steel wire surface and thus inevitably peels off from the surface
due to the friction between wire and the welding tip and hence causes welding instability

due to clogging of torch. Finally, potentially hazardous chemicals such as H2SO4 and
CuSO4 are used during copper plating. In the view of above, the present invention has
developed and applied a new coating which eliminates health hazards and at the same
time, results in lower spatter generation during welding, improved feedability through
welding torch nozzle and gives a higher shelf life to the wire electrode.
A number of studies have been carried out towards overcoming the disadvantages of
using copper coating. Most of them aim at eliminating copper coating and use the solid
wire with a modified surface to obtain better properties.
Y Kim and J Lee [1] (US Patent 6696170 B2) imparted a proper degree of roughness to
the wire surface to ensure wire feedability instead of promoting smoothness to the wire
surface as pursued in conventional copper free wires. This copper-free wire has worked
faces, meaning faces drawn with a die and unworked faces continued in the
circumferential direction on a wire surface. Feedability and arc stability are improved by
providing the wire with a certain degree of concave roughness corresponding to the inner
surface of the contact tip hole so that convex portions of the contact tip hole can remain
in stable contact with the worked faces of the wire.
Kurokawa et al [2] (US Patent 6054675 A) have described a similar invention with no
copper plating. A wire electrode with specified chemistry is applied with at least one
compound serving as an arc stabilizer and selected from the group consisting of a
potassium compound and a cesium compound in such a way that the relative proportion
of the compounds are maintained in a certain ppm range. The invention, it is claimed,
results in good welding properties such as reduced spatter and good arc stability during
welding.
Ito et al [3] (US Patent 2003/0085211 Al) have also described a plating-free solid wire for
arc welding. The wire is provided with pits having an opening on circumferential surface
of the wire and being wider inside than at the opening. Each pit contains sulfide and an
oil containing polyisobutene present in an amount of 0.1 g to 2 g per 10 kg of wire. These
ensure good feedability and lubricating properties and fewer spatters.

Yamaoka et al [4] (US Patent 6989510 B2) have claimed that a non-copper plated solid
wire has resulted in excellent feedability and a reduced amount of spatter generated
during CO2 gas shielded arc welding when welded at a relatively low current. The
method involves maintaining the ten point average roughness (Rz) of the wire surface
between 0.10 to 9.0 µm and the Vickers micro hardness (Hv 91g)) between 125 and 310.
Yukio et al [5] (US Patent 6906286 B2) have disclosed a similar solid wire for arc
welding which includes a flat portion of wire surface with no copper plating, wherein the
Vickers microhardness (Hv) of the flat portion and the arithmetic roughness average (Ra)
are controlled to certain desired levels.
There are other similar inventions as described in the above mentioned patents where a
copper free wire electrode is used with various modifications on the surface. JP-A No.
104883/1999 describes a copper-free wire on the surface of which a K compound and
M0S2 are allowed to be present for further reducing the spatter. Wires without copper
plating and use of similar lubricating powder have also been proposed in Japanese Patent
Registration No. 2682814. Korean Patent No. 134857 enhances the feedability through
roughness control.
The present invention is different from all the prior art mentioned in the sense that copper
is replaced by another coating formulation, as described in the subsequently, which
imparts superior welding properties to the wire electrode.
OBJECTS OF THE INVENTION:
An object of this invention is to propose a method for developing nano-particle coated
highly conductive electrode wire;
Another object of this invention is to propose a method for coating of nano-sized particle
to be used in GMAW by adopting a procedure of binary composite metallic ion
deposition or nano-blanketing of the surface micro structure of the electrode wire;

Still another object of this invention is to propose a nano-particle coating welding rod
which minimizes the environmental and health hazards posed by conventional Cu-coated
electrode making process and welding operations, by developing novel eco-friendly,
nano-particle coated electrodes;
Yet another object of this invention is to propose a cost effective process to produce
electrodes with desirable surface coating
Further object of this invention is to propose an user-compatible electrode.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a novel method for developing nano-particle
coated wire electrode comprising:
subjecting the wire electrode to the step of hot water blanching in a water tank at a
temperature ranging from 40°C to 100°C;
Thereafter the treated wire is passed through the composition of 'Coflex' at a temperature
range of 30 ° C to 100 ° C at pH > 7.
The same coated wire electrode goes through the second step of coating with 'Coplex'
and followed by foam squeezing to remove the excess coating, and then through the third
step of hot air blasting to cure the coated wire electrode.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
The invention will now be more particularly illustrated by means of the accompanying
drawing which represents a sectional view of the set-up for ensuring continuous
production of electrode wire with a metal coating other than copper. The set-up

comprises a large tank or cistern divided into four compartments marked A, B, C and D
respectively, where (1) is the point of intake, (2) shows stabilizer fluid, (3) is the
temperature controller, (4) shows the conductive fluid maintained at a desired
temperature, (5) depicts immersion heated thermostatical control, (6) is the foam
squeezer, either brush or tube type, (7) is hot air nozzle optionally carrying a foam
squeezer, (8) shows the outlet for the treated wire, (9) shows the overall tank or cistern
which is divided into four compartments A, B, C, D having partitions, (10) shows the
location of the dice and (11) shows the region housing the spindle.
DETAILED DESCRIPTION OF THE INVENTION:
The foregoing aims and objectives are fulfilled by the present invention which provides
novel eco-friendly user-compatible electrodes having coating of nano-sized metal
particles which usually avoid a coating of copper.
The subject investigation also relates to a process for the production of the aforesaid
electrodes which comprises:
1) Passing the carbon steel or alloy steel wire through a dice of desired orifice.
2) Passing the wire through a bath of wetting agent like sodium stearate or similar
metal soap-based oil leading to a dimensional reduction, known as wet drawing.
3) Allowing the thus reduced wire to pass through a succession of compartments/
chambers in a tank containing chemicals for facilitating deposition of nano-size
metal particles onto the wire rod.
4) Treating the coated wire by air jetting and/ or squeezing or sponging and.
5) Finally treated wire is sent for winding in a spool followed by packaging. The
spools are cooled after stabilization of the surface before final packaging.
The deposition technique is not only unique, but also novel which adopts a liquid phase
metallurgical nano treatment for achieving a uniform coating of the electrode wire. As
indicated earlier, metal ion deposition takes place by nano ion blanketing on the wire

surface at predetermined speed to control the deposition pattern. The technique is
particularly suited for imparting coating on steel wire by leading the wire through
different compartments sequentially at a predetermined speed to control the deposition
pattern. The metal(s) may be either in the form of metallic ion or ionic salt and the metal
ions may be single, dual or in composite forms. The metals may be selected from, inter
alia, aluminium, barium, cadmium, iron, magnesium, molybdenum, nickel, silicon,
titanium, vanadium, silver, gold, zinc, sodium, potassium and silicates or fluorides of
metals. Preferably the ions are not in elementary or particulate form but in soluble ion
form and their deposition result in a coating thickness in the range 0.0001 urn to 0.5 urn.
It has been observed, both through tests conducted in the laboratories as wells as welding
work on shop floor, such coated welding rods generate much lesser degree of volumes of
gases and fumes, maintaining excellent atmospheric conditions and ensuring welding
pattern.
The substrate material used on which the coating formulations are applied to develop the
new welding rod is the conventionally used carbon steel wire. The dimensional
characteristics are controlled by drawing processes where wet drawing is performed by
drawing the wire while immersed in a wetting agent selected from sodium stearate,
vegetable oils or metallic soaps of zinc, cadmium, magnesium or tin. The drawn wire is
passed through a series of liquid baths used in different compartments of a tank specially
designed for this purpose equipped with facilities for stirring, agitating, bubbling and/ or
heating. Subjecting wire to the sequences of operations evolved as constituent steps for
the overall processes of this invention leads to a product having either shiny or matte
lustrous appearance with a predetermined deposition pattern when viewed through a high
powered microscope or through an SEM picture with high resolution.
The said tank is made of steel with suitable lining or inside coating. Compartments or
baths A, C and D have got heating arrangements, and bath B is equipped with a stirring
or churning mechanism. The walls of the compartments are made of heat conducting
materials which ensures heat equilibrium inside the said set-up.

The weld wire after drawing passes through bath A containing 20-200 litres of water,
maintained at 40-100 °C. The treatment not only quenches the weld wire surface after
wet drawing but also opens up the microstructure of the surface for further treatment in
bath B containing 20-200 litres of a proprietary composition developed by the co-
inventor towards this end, named 'Coflex' (a trade mark) [6]. The bath B is maintained
between 30-100 °C and the contents of bath B are under constant stirring and metal salts
present therein, often in colloidal form, get adsorbed by the weld wire.
Coflex is a mixture of alkali or alkaline earth metal hydroxides or carbonates extended
with borax in presence of ethylene glycol, propylene glycol and silicon oil of desirable
molecular weight range along with alkali metallic salt of an abietic or citric acid and
other alkaline electrolyte ion exchangers. All the ingredients are taken in a reactor under
nitrogen blanketing and continuously stirred for one to two hours, maintaining the
temperature at an optimum range of 70 °C to 100 °C, leading to a hydrolytic reaction.
The resulting solution, Coflex is a colloidal alkaline stabilizing liquid capable of
imparting desirable surface characteristics, leading to the formation of microstructure
facilitating deposition of eco-coated metal ions thereon. An approximate analysis of
Coflex is given below:


Thereafter the weld wire is led through bath C filled with another proprietary
formulation, 'Coplex', a trade mark owned by the co-inventor [7], and the bath is
equipped with heating as well as stirring arrangements. Bath C contains around 20-200
litres of Coplex and is maintained at a temperature ranging between 30 °C and 100 °C.
Coplex comprises of a reaction product of citric or oxalic acid, water and air-bubbled
phosphoric and other mineral acids in presence of alcohol, glycol, metal salts, extenders
and leveling agents. The right formulation is arrived at by putting proportionate amounts
of the ingredients in a reactor and stirring the mass for about two hours, under heated
conditions (temperature around 80 °C). For Coplex a suitable catalyst is triethyl amine
borate and extenders are selected from glycerol, propylene glycol, butanol and the like. It
is essentially an acidic organo-metallic ester, comprising the following constituents:
i) Organic acid, e.g. citric acid, oxalic acid and/ or phthalic acid;
ii) Inorganic acid or derivatives thereof, H3PO4;
iii) Soluble metal salts in amounts of 0.001% to 1.0% per litre: Metal salts like
manganese < 0.001-1% (preferable), aluminium, nickel, titanium, lithium, etc.
iv) Extending agent - either an alkaline compound or ethanol-extended glycerol;
v) Ester-forming compound - ethylene glycol, propylene glycol or glycerine;
vi) Silicone oil < 0.001-1%
vii) Zinc chromate < 0.001-1%
viii) Alkali/ alkaline chromate < 0.001 -1 %
ix) Oxo compound and
x) Highly oxygenated de-ionized water - q.s.

The physical characteristics of both the formulations, Coflex and Coplex are summarised
below:

The weld wire leaving bath C enters into compartment D, which is also filled with the
above mentioned solution Coplex and is also heated. The weld wire subsequently passes
through a die, hot air nozzle and foam squeezer, which is then led to the tension drum and
thereafter for final winding. After the sequence of treatments noted above, the treated
weld wire is subjected to oxygen/ air blasting to effect rapid surface curing.
The baths C and D, apart from having a heating mechanism also has a moving spindle on
which the weld wire from bath B wraps around the spindle wheel for improving upon the
resident or wetting time. The spindle imparts a continuous agitation for bringing about
proper dispersion/ distribution of the contents of the bath, e.g. organo-metallic ester in a
liquid form, maintained at a temperature varying between 30 °C and 100 °C. Thereafter

the weld wire passes through the dice under air jetting nozzle and then led to the foam
squeezing or sponging with cotton cloth swab. The excess carbonaceous material and dirt
thus get removed creating a good surface dispersion before air blasting. The dry wire is
then led to the tension drum followed by winding in the spool. The spools are cooled
after stabilization of the surface before final packing.
The principal features of the application of nano-sized coating over the weld wire may be
summarized as follows:
i) Treatment with lubricants, e.g. sodium stearate, vegetable oils or metallic soaps
during diametrical reduction of the weld wire and then its movement into the
treatment baths,
ii) Hot water blanching of the weld wire surface prepares the wire for treatment in
bath B containing the proprietary composition COFLEX™ containing a solution
or colloidal dispersion in aqueous medium, reddish white in colour and
comprising triethylamine extended with either ethylene or propylene glycol and
silicone oil in presence of sodium, potassium and magnesium salt or mixture
thereof, at a pH exceeding 7 and maintained at temperature between 30 °C and
100 °C.
iii) Bath C containing proprietary composition COPLEX™ which is greenish white in
colour with a strong acidic behavior and basically is an organo-metallic ester.
Successive treatments of the weld wire by proprietary products 'Coflex' and 'Coplex'
bring about a number of desirable properties, most important of which is adhesivity and
reaction characteristics of the weld wire surface, which facilitates formation of a uniform
coating on the surface thereof.
The wire electrode of the current invention is environment friendly, results in lower
spatter generation during welding, ensures good feedability with better lubrication and no
flaking and has a higher shelf life compared to the conventional copper coated wire
electrode.
Additional modifications and improvements on the present invention will be apparent to
those skilled in the art. Thus the particular combination of parts of the reaction vessel

described and illustrated herein is not intended as limitations of alternatives within the
spirit and scope of the invention.

WE CLAIM:
1. A novel method for developing nano-particle coated wire electrode comprising:
subjecting the wire electrode to the step of hot water blanching in a water tank at a
temperature ranging from 40°C to 100°C;
treating the wire electrode with a proprietary composition at pH>7 and temperature
ranging from 30 °C to 100 °C;
subjecting the coated wire electrode to the step of coating with a proprietary composition
at a temperature ranging from 30 °C to 100 °C;
foam squeezing the wire electrode to remove excess coating;
drying the coated wire electrode; and
curing the wire electrode.
2. The method as claimed in claim 1, wherein said composition comprises: Sodium - 10
to 20 g/1; Potassium or modified potassium 10 to 20 g/1; Manganese - 10 to 20 g/1;
Silicone Oil - 5 to20 g/1; Ethylene Glycol - 10 to 20 g/1; Propylene Glycol - 10 to 20 g/1;
Glycerin 10 -20 g/1; Abietic acid or Citric acid 2-5 g/1.
3. The method for coating a wire electrode as claimed in claim 1, wherein the wire
electrode is surface cured by subjecting it to oxygen
4. The method for coating a wire electrode as claimed in claim 1, wherein the wire
electrode is surface cured by subjecting it to hot air blasting.
5. The method for coating a wire electrode as claimed in claim 1 further comprising the
step of treating the wire electrode with a lubricant.

6. The method for coating a wire electrode as claimed in claim 5, wherein the lubricant
is selected from the group consisting of sodium stearate, vegetable oils and metallic
soap solutions.
7. The method for coating a wire electrode as claimed in claim 1, wherein the wire
electrode is subjected to skin past wet drawing.
8. The method as claimed in claim 1, wherein said comprises organic acid, inorganic
acid or derivatives thereof; < 0.001 - 1 % soluble metal salts extending agent; ester
forming compound; < 0.001 - 1 % Silicon oil; < 0.001 - 1 % Zinc Chromate; < 0.001
- 1 % Alkali; < 0.001 - 1 % Alkaline Chromate; Oxo-compound and highly
oxygenated de-ionized water.
9. The method as claimed in claim 8, wherein the organic acid is selected from the group
consisting of Citric Acid, Oxalic Acid and Pthalic Acid.
10. The method as claimed in claim 8, wherein the inorganic acid is air bubbled
phosphoric acid.
11. The method as claimed in claim 8, wherein the metallic salt is silicate of the metals
selected from the group consisting of aluminum, barium, cadmium, iron, manganese,
magnesium molybdenum, nickel, silicon, titanium, vanadium, silver, gold, zinc,
sodium and potassium.

12. The method as claimed in claim 8, wherein the metallic salt is fluoride of the metals
selected from the group consisting of aluminum, barium, cadmium, iron, manganese,
magnesium molybdenum, nickel, silicon, titanium, vanadium, silver, gold, zinc,
sodium and potassium.
13. The method as claimed in claim 1, wherein coating thickness on the wire electrode is
in the range of 0.0001 µm to 0.5 µm.