In the
process of manufacturing the welding is main process in fabrication. The
Electrode required for welding is also plays major role in the quality of
welding. As per the material and other requirement the electrodes are used with
different sizes and different grades of electrodes are being used as the type
of fabrication work.
The electrodes classification is done
on the basis of different parameters such as chemical properties strength etc,
Let we discuss the classification of electrodes as per AWS A5.1 .
1) The prefix “E” indicates Arc welding
electrodes.
2) Out of four numbers mentioned on
electrodes the first two numbers & Five numbers of electrodes the first
three numbers indicates the minimum requirement of tensile strength.
For example,
1) E-60XX : Indicates the minimum
tensile strength 60,000 PSI.
2) E-70XX : Indicates the minimum tensile strength 70,000 PSI.
3) E-80XX : Indicates the minimum
tensile strength 80,000 PSI, and so on.
3) The Third digit in four numbers and
Fourth digit in five digits mentioned on electrode is indicates welding
position by which welding is done.
If the number on that
place is 1 it means Welding prefer for all position.
If the number on that
place is 2 it means that Welding prefer for Flat position and horizontal
fillets.
4) The last two digits indicated the
coating type, polarity and current requirements. The following digits shown the
type and requirements as shown,
1) 10 : 10 number means the electrode
suitable for all types of welding positions the coating contein cellulose.
2) 11 : The number 11 is similar type
but the difference is that specially used for only AC supply, we can also used
that type of electrodes with DS supply but welding quality and weldability
expense.
3) 12 : The 12 number indicates which is
suitable for all type of welding positions but mainly used in flat position and
horizontal position.
4) 13: The number 13 indicated used in
all type of welding positions. Can be used with both supply as AC and DC .
5) 14 : The 14 number indicates increase
in efficiency, such type of electrode contain coating iron powder. Can be used
with AC and DC(+) and DC(-).
6) 15 : The number 15 is shows suitable for
all welding positions, can we used with DC(+) supply only.
7) 16 : The 16 number indicated similar
type used with AC supply and DC(+) supply.
8) 18 : The 17 number indicated
increased efficiency and can be used with AC and DC(+) supply.
For example shown below,
Pic01.
9) 20 : The number 20 indicates that
suitable for flat position, such type of grade contain large amount of iron
oxide, can be used with AC,DC(+) and DC(-) supply.
10)
24
: The 234 number indicates that use in flat position. Can be used with AC,DC(+)
and DC(-) supply.
11)
27
: The 27 number type grade contain acid type contact electrode. Can be used
with AC and DC(-) supply.
12)
28
: The 28 number type electrode suitable for flat position, efficiency higher
than EXX18 electrode, can be used with AC and DC(-) supply.
Proper welding procedures required
following parameters,
A) Correct Current. : If supplied
current is very high or very low then its badly effect on weld of the joint.
If supplied current too
high then the electrode melts fast and because of that molten pool is large and
irregular shape.
If supplied current too
low then there is not enough heat to melt the base metal and because of that
the molten pool is too small and irregular. The change in current that is too
low or too high impact on molten pool as pool is irregular.
B) Correct length of arc. : If the
voltage is too high or arc is too long then metal melts off the electrode is
large that effects the poor fusion between original metal and deposited metal.
C) Correct size of electrode : The large
numbers of factors may affected by the size of electrode such as type, preparation
of joint, position, the ability of electrode to carry the hight current without
loss of metal and maintain the original properties after welding.
D) Travel speed : For good welding the
speed of welding required adequate as if the Speed of welfing is too high then
the pool does not long enough also impurities locked in and if the speed of
welding is too slow then the metal piles up and the weld bead is wide.
E) Angle of electrode : The angle of electrode
id very important in fillet welding. The angle between plates make improve
quality of weld if correct electrode angle.
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