Ratio INV130, Инструкция по эксплуатации, Страница: 13 / 16

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• The manufacturing characteristics of these machines guarantee a high grade of arc stability with respect to length
variations from the electrode caused by the welder’s hand.
• The electrode is made up of two basic parts:
a) The core which is the same type of base material (aluminium, iron, copper, steel, stainless steel) and provides
material to make the join.
b) The coating, which is made of various mineral and organic substances mixed together and with the functions of:
Gas protection. One part of the coating is activated at arc temperature and moves air away from the area, creating a
column of ionised gas which protects the melted material.
Provision of agglutinating and dross materials: A part of the coating melts and provides elements which combine with
the core material in the fusion process.
The main types of coating are:
Rutile coatings. These coatings lend the seam a better appearance and they are widely used. Welding may be carried
out using both AC and DC currents with both polarities.
Basic coatings. These are used essentially for high quality mechanical welding, although the arc tends to spatter and
the appearance of the seam is less attractive than that of rutile coated. DC current is generally used with the electrode
at the positive connection (reverse polarity), although there are some basic electrodes for AC currents. The basic
coatings are sensitive to humidity and therefore should be stored in a dry place inside sealed boxes. You are reminded
that steels with carbon content of over 0.6 must be welded with special electrodes.
Acid coatings. These coatings provide high grade welding and can be used with AC or DC with a electrode-clamp on at
the negative terminal (direct polarity). The molten weld is highly liquid and so the electrodes are basically suited to flat
welding.
THE CHOICE OF ELECTRODE
The choice of the diameter of the electrode depends on the thickness of the material, on the type of joint, and on the
position of the weld. When “positive” welds are made the molten weld tends to fall due to gravity, and therefore use of a
small diameter electrode is recommended for repeated welds. Large diameter electrodes need high welding currents to
provide an adequate thermal energy.
THE CHOICE OF WELDING CURRENT
The stability and continuity of the weld mean that work can be carried out with low value currents in difficult conditions.
The following table shows the minimum and maximum current which can be used for carbon steel welding.
ELECTRODE DIAMETER WELDING CURRENT
mm Min Max
1,6 25A 50A
2 40A 70A
2,5 60A 110A
3,25 100A 140A
4 140A 180A
WELDING SCHEME WITH COATED ELECTRODE
1 - Connect the earth clamp to the negative terminal on the welding machine (-).
2 - Connect the electrode holder to the positive terminal (+).
3 - Insert the electrode into the electrode-holder clamp.
4 - Connect the machine to the electrical supply.
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– Adjust the potentiometer in a suitable position in order to begin welding