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FIELD OF INVENTION
The invention relates to an arc-melting furnace with a single arc for melting of
non-conductive mineral oxides to produce low-volume of fused welding flux.
BACKGROUND OF THE INVENTION
Welding fluxes are used as shielding medium to protect the atmospheric
contamination in submerged arc welding and electroslag welding methods. These
welding fluxes are made up of mineral oxides like quartz sand, manganese di-
oxide, bauxite, calcium carbonate, calcium fluoride and de-oxidants. The mixture
i
of a known composition from the mineral oxides are loaded in to a furnace and
melted by different energy sources to form a homogenous molten slag. The
molten slag is then quenched to obtain a welding flux with further processing. At
present, industries are using either a gas-fired furnace, three phase arc melting
furnace or a continuous discharge furnace for the manufacturing of fused
welding fluxes.
Japanese Patent JP02217196, titled "Manufacture of fused type flux for low
hydrogen and low bulk density submerged arc welding" discloses a method for
manufacturing of submerged arc welding flux. This method teaches as to how
the development of defect at the time of welding can be prevented by utilizing
C02 gas generated during the manufacture of fused type flux, in particular at the
time of solid decomposition reaction in the metal carbonate, and till foaming of
the flux. In this method, raw materials of mineral oxides is melted in a melting
furnace, the metal carbonate having 20-40 mesh grain size is blown together

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with gas having 5-10kg/cm2 pressure during tapping or after tapping. By this
method, the flux is foamed with the generated C02 gas and the fused type flux
for low hydrogen and low bulk density submerged arc welding is produced. The
initiation of defect of blow hole and pitting at the time of welding can be
prevented. This invention deals with a method of processing a welding flux and
does not deal with..the furnace design for the manufacture of welding fluxes^
United States Patent 4094630, deals with an apparatus for curing bonded
welding flux wherein the flux is passed along a series of vibrating inclined planes.
Gas fired radiant heaters are positioned above the planes to heat the flux, with
combustion gases and vapor being driven off from the flux passing upwardly
between the radiant heaters and the flux covered planes.
United States Patent 2331419, deals with melting of powder metals and alloy
powders only, which are conductive and the design of furnace is not for non
conductive mineral oxides.
At present, commercially available melting furnaces for the manufacture of
welding fluxes have a minimum capacity of around 250kg only. Such furnaces
require around 500KVA continuous energy with around 150 volt three phase arc
at 2000 to 3000 amperes current. The energy requirement and the capital cost is
very high. To reduce this high cost and energy and to produce low volume of
fused welding fluxes in the range of 25 to 100kg batches, a suitable furnace is
needed by the art.

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0B3ECTS OF THE INVGENTION
It is therefore an object of the invention to propose an apparatus for" the
manufacture of low volume of fused welding flux using qonconductive mineral
oxides as raw material.
Another object of the invention is to propose an apparatus for the manufacture
of low volume of fused welding flux using nonconductive mineral oxides as raw
material, which can melt the mineral oxides with a single arc produced between
two graphite electrodes.
A still another object of the invention is to propose an apparatus for the
manufacture of low volume of fused welding flux using nonconductive mineral
oxides as raw material, which employs a standard single phase AC transformer.
Yet another object of the invention is to propose an apparatus for the
manufacture of low volume of fused welding flux using nonconductive mineral
oxides as raw material, which constitutes a simple user friendly single arc
furnace with minimum operating steps.
A still further object of the invention is to propose a process for manufacturing of
fused welding flux using non-conductive mineral oxides.
A further object of the invention is to propose an apparatus for the manufacture
of low volume of fused welding flux using nonconductive mineral oxides as raw
material, which is efficient and cost-effective.

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The description, which follows, is to be understood as only illustrative of a
particular form of this invention. However, such a particular form is only an
exemplary embodiment and this invention is not intended to be taken
restrictively to this example alone.
SUMMARY OF THE INVENTION
Accordingly, there is provided an apparatus for the manufacture of low-volume
fused flux by using nonconductive mineral oxides, comprising a furnace shall or
a melting crucible interposed in an outer shell (1), the outer shell (1) being
formed of a water-cooled inner shell (4), and a lining layer (3), the furnace shall
being supported by a stand (17), at least one top graphite electrode (15) and
one bottom graphite electrode (5), the top electrode (15) being placed on an
electrode holder (16) which is movably fixed on one hand to the stand (17), the
top graphite electrode (15) being enabled by an electric motor (12) to undertake
a vertical movement via a chain (13) which is connected to a gear box, the
electric holder (16) on the other hand being connected to the gear box; and a
cooling arrangement in the form of a tube (7) into a water cooled chamber
assembly (2), the crucible being fitted with a plurality of pivots (9) on the outer
shell (1), the outer shell (1) being provided with a top cover (6) which allows
manual tilting to feed raw-material charge.
The invention further discloses an apparatus for carrying out the method of the
invention.
The invented furnace also enables to melt and process mineral oxides for other
laboratory and industrial applications.

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According to this invention, a single arc is produced by a graphite electrode. This
single phase arc requires only around lOOvolt at lOOOampere current for
achieving the melting. For this purpose, a suitable standard single phase AC
transformer is employed.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 of the invention illustrates the cross sectional view of the apparatus for
the manufacture of fused welding fluxes according to the invention.
Figure 2 shows the top view of the furnace shell / melting crucible according to
the invention.
Figure 3 shows the overall view of the arc melting furnace with an electrode
moving mechanism. .
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in figure-1 the apparatus consists of a furnace shell / melting crucible
which is contained in an outer shell (1) made up of a water cooled inner shell (4)
and a lining layer (3) for insulation and thermal barrier. The furnace shell/melting
crucible is fitted with a bottom graphite electrode (5) at the bottom. A cooling
arrangement (7) is provided through a tube (7) into a water cooled chamber
assembly (2). The crucible is fitted with a plurality of pivots (9) on the outer shell
(1) to facilitate securing on a structure (17) as shown in Figure 3. The furnace
shell (1) is provided with a top cover / lid (6) which can be manually opened to
facilitate feeding of raw material charge.

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Figure-2 shows the pivot positions (9), the cooling water inlet tube (7) and a
water outlet tube (10) after circulation in the water cooled chamber assembly
(2). A spout (11) is provided on the top of the shell to facilitate pouring of
molten slag after melting.
As shown in figure-3 the furnace shell / melting crucible is rested on a stand
(17). An electrode holder (16) is fitted to the stand (17). A top graphite electrode
(15) is fitted on to'the electrode holder (16) to facilitate up and down movement
for arcing and melting. The movement of the top graphite electrode (15) is
controlled by an electric motor (12). The electrode holder (16) is connected with
a gear box through a chain (13) for easy movement of the graphite electrode
(15). A single phase AC transformer connection is provided to the top graphite
electrode (15) with a ground cable connection to the bottom graphite electrode
(15). This is a portable apparatus requiring no grouting and shall be relocated
with ease.
As per the predetermined formulation, 25 to 30 kg of mineral oxides are mixed
thoroughly using a mechanical'mixture to get a homogenous mix, which is
known as charge. The mineral oxides shall be in the powder form. A check is run
for the electrical connections, cooling water supply and the electrode movement
before starting the melting.

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The power supply is switched on, and the top graphite electrode (15) is moved
towards the bottom graphite electrode (5) to create the arc. The movement of
the graphite electrode (15) is facilitated by the electric motor (12). After the arc
is established, start feeding the charge is commenced, and the charge is allowed
to melt progressively. Once, sufficient quantity of molten slag pool is formed
through melting, the arc gets quenched automatically. In the absence of the arc,
electricity starts flowing through the molten slag pool. The graphite electrode
(15) is progressively moved up and further charge is manually added into the
furnace shell. The top cover (6) should be opened only during the charging of
raw materials and to be kept in closed condition to avoid heat radiation during
melting. The total melting time will be varying depending on the chemical
formulation of the raw material charge. However, it takes around 60 minutes to
90 minutes for melting a full charge of 25 to 30kg of mineral oxides.
During the process of melting the mineral oxides in the above said melting
furnace, the outlet water (10) temperature should be closely monitored. The
outlet water temperature should be controlled within about 60 to 70°C by
adjusting the inlet water flow. For maintaining this, the cooling water inlet
temperature (7) should be around room temperature or should not exceed 30°C
with a line pressure between 4 to 6psi. During the melting, the water-cooling
arrangement in the inner shell (4), will be creating a self lining in the inner
surface of the inner shell (4). This is due to the solidification of the molten slag
to a thickness of around 3 to 5mm, which is in contact with the inner shell (4).

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After completion of melting, suitable quantity of de-oxidisers are added as per
the requirement. At the end of the melting process, the furnace shell (1) can be
tilted with a lever to facilitate pouring of the molten slag through the spout (11).
The spout (11) is lined with high temperature materials to protect the surface.
The molten slag shall be quenched on a water-cooled plate or into the water
chamber (2). The resultant product with lumps are then suitably ground and
used as fused welding flux for achieving shielding either by Submerged arc
welding process or Electroslag welding process.
More than 100 batches were melted with 25 to 30kg charge to verify the
performance of the above said single arc-melting furnace. The results were
highly satisfactory.

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WE CLAIM:
1. An apparatus for the manufacture of low-volume fused flux by using
nonconductive mineral oxides, comprising:
-a furnace shell or a melting crucible interposed in an outer shell (1)^ the
outer shell (1) being formed of a water-cooled inner shell (4), and a lining layer
(3), the furnace being supported by a stand (17);
- at least one top graphite electrode (15) and one bottom graphite
electrode (5), the top electrode (15) being placed on an electrode holder
(16) which is movably fixed on one hand to the stand (17), the top
graphite electrode (15) being enabled by an electric motor (12) to
undertake a vertical movement via a chain (13) which is connected to a
gear box, the electric holder (16) on the other hand being connected to
the gear box; and .
- a cooling arrangement in the form of a tube (7) disposed into a water
colled chamber assembly (2), the crucible being fitted with a plurality of
pivots (9) on the outer shell (1), the outer shell (1) being provided with a
top cover (6) which allows manual tilting to feed raw-material change.
2. An apparatus as claimed in claim 1, wherein the outer shell (1) comprises a
spout (11) for top-loading of the molten slag after melting.

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3. An apparatus as claimed in claim 1, wherein a water outlet tube (10) is
provided for exiting of the water after circulation in the water cooled chamber
assembly (2).
4. A process for the manufacture of low-volume fused flux by using non-
conductive mineral oxides, comprising the steps of:

- preparing a charge by homogeneous mixing of mineral oxides in a powder
form;
- moving the top graphite electrode towards the bottom graphite electrode
to establish an arc; ' i
- feeding the charge progressively to form a sufficient quantity of molten
slag pool through melting leading to automatic quenching of the arc;
- progressively moving the top graphite electrode on the reverse direction
to allow manual loading of further charge;
- closing the top cover of the shell which was opened during loading of the
charge, and allow a predetermined time for melting of a specified quantity
of the charge; ■:

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- monitoring and controlling the outlet water temperature in the range of
about 60 to 70°C by adjusting the temperature and pressure of inlet water
respectively within 30°C and between 4 to 6 psi;
- adding a suitable quantity of de-oxidisers after completion of melting;
- tilting the furnace shell at the end of the melting to facilitate pouring of
the molten slag through the spout;
- quenching of the molten slag into the water chamber; and '
- taking-out the resultant product in a lump form from the furnace and
ground to produce the fused welding flux.
5. A process as claimed in claim 4, wherein the predetermined time for melting is
around 60 to 90 minutes for a specified quantity of 25 to 30 kg of mineral
oxides.
6. An apparatus for the manufacture of low-volume fused flux by using
nonconductive mineral oxide as substantially described and illustrated herein
with reference to the accompanying drawings.
7. A process for the manufacture of low-volume fused flux by using non-
conductive mineral oxides as substantially described and illustrated herein with
reference to the accompanying drawings.

The invention relates to an apparatus for the manufacture of low-volume fused
flux by using nonconductive mineral oxides, comprising a furnace shell or a
melting crucible interposed in an outer shell (1), the outer shell (1) being formed
of a water-cooled inner shell (4), and a lining layer (3), the furnace being
supported by a stand (17), at least one top graphite electrode (15) and one
bottom graphite electrode (5), the top electrode (15) being placed on an
electrode holder (16) which is movably fixed on one hand to the stand (17), the
top graphite electrode (15) being enabled by an electric motor (12) to undertake
a vertical movement via a chain (13) which is connected to a gear box, the
electric holder (16) on the other hand being connected to the gear box, and a
cooling arrangement in the form of a tube (7) disposed into a water cooled
chamber assembly (2), the crucible being fitted with a plurality of pivots (3) on
the outer shell (1), the outer shell (1) being provided with a top cover (6) which
allows manual tilting to feed raw-material change.