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Verfügbare Sprachen
•
C
ELLULOSE
•
A
A
RC
IR
•
C
T
ONTINUOUS
16
WELDING MODE
16.1 MMA WELDED WITH COATED ELECTRODE
16.1.1
I
NSTALLATION
Connect the electrode holder and the earth clamp to the
output sockets of the machine according to the polarity
required by the manufacture of the electrode that you
wish to use.
CAUTION! Make sure that the electrode does not touch
any metal part at all, since in this welding mode, the
output sockets of the machine are live.
16.1.2
M
W
W
MA
ELDED
ITH
To obtain good welds, it is necessary to weld on clean
metal
pieces,
which
contaminating agents. In preparing the edges to be
welded, take into account the thickness, type of joint,
position of weld and the requirements of the project.
Normally the edges are prepared in a "V" shape; but with
thicker items, it is recommended to have "X" shaped
edges (backweld) or "U" shaped edges (no backweld).
The manufacturers of the electrodes specify the optimum
welding current for each type of electrode. The type of
electrode to be used depends on the thickness of the
material to be welded and on its position.
Insert the chosen electrode into the electrode holder. To
strike the electric arc, rub the electrode against the
material to be welded connected to the earth (ground)
clamp. Once the arc is struck, lift the electrode holder
slowly to the normal welding distance.
To strike the arc better, an initial current is supplied which
is higher (hot-start) compared to the welding current. The
electrode on melting deposits in the form of drops onto
the piece to be welded and its outer coating is consumed
supplying the shielding gas for the welding.
To facilitate the fluidity of the welding arc, while the drops
are coming off, which can cause a short circuit between
the electrode and the weld pool, a momentary increase in
the welding current (arc-force) is given, thus preventing
the arc from going out.
If the electrode stays stuck to the piece to be welded,
there is an anti-stick function that, after a certain short-
circuit time, cuts off the power to the generator. Thus you
can detach the electrode without damaging it.
When the coating electrodes are used, you need to
remove the dross from the welding after every pass.
General information for choosing the electrode are given
in the table below; we remind the operator that all data
are for the purpose of information only.
E
n
E
n
W
IG
ELDING
C
E
OATED
LECTRODE
are
free
of
rust
or
g
l
i
s
h
g
l
i
s
h
4
0
0
P
o
w
4
0
0
P
o
w
THICKNESS
OF
MATERIAL
(mm)
1,5 ÷ 3
3 ÷ 5
5 ÷ 12
>12
16.1.3
C
ELLULOSE
This kind of electrode melts a large quantity of base
material offering a good penetration after the first pass
and minimizing slags in the bath. It is ideal for machining
tubes.
They are fitted with a covering made of organic material
(cellulose) associated to deoxidizing elements (Mn and
Si). Thus, containing a large quantity of H in the arc, they
require a relatively higher arc tension.
The covering allows a strong spatter of metal from the
other
electrode into the bath; it is therefore possible to weld in
any position, even with narrow edges.
The electrodes offer the deepest penetration (up to twice
the diameter of the electrode, plus 2 mm).
16.1.4
S
CARFING
Scarfing is carried out by an electrode-holder torch which
directs an air jet towards the fusion zone of the material
removing the latter from the piece.
The electrode is composed of a mixture of coal, graphite
and binders, covered by copper.
This operation is performed to cut steel, cast iron and
copper alloys and to carry out superficial operations such
as grooves or crack removing.
The electrode shall be pushed following the cutting
direction to facilitate material removing; inclination
depends on the depth of the incision desired.
The angle varies between 15° and 70° for surface
finishing and scarfing; between 35° and 70° for grooves
and between 70° and 80° for cutting.
The distance between the electrode tip and the torch
must not be higher than 15 cm; this distance must be
reduced to a half if non- ferrous materials are machined.
Here is a table indicating the currents required according
to
the
electrode
recommended).
∅ ELECTRODE
(mm)
4
4.76
6.35
8
9.5
12.7
15.8
19
8
8
e
r
P
u
l
s
e
e
r
P
u
l
s
e
∅
ELECTRODE
CURRENT (A)
(mm)
2
2,5
3,25
4
C
OVERINGS
size
(the
maximum
MINIMO (A)
80
110
150
200
300
600
800
1200
WELDING
40 ÷ 75
60 ÷ 110
95 ÷ 140
140 ÷ 190
current
is
MASSIMO (A)
150
200
350
450
600
1000
1200
1600
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