POLARITIES USED IN ARC WELDING
Welding power sources supply either AC OR DC
used both forms in general. In case of DC the current flows in one direction
only but in case of AC current the current flow in reverse in every cycle When the electric circuit is created the welder
turn on the positive pole or negative pole this property is called polarity. Polarity
plays major role in welding because the right polarity affects the strength and
quality of weld and the wrong polarity results the spatters, bad penetration
etc.
Two types of polarity consisting
one is positive polarity and other is negative polarity.
1)
NEGATIVE POLARITY (DCEN) :
Pic01
Negative polarity
also called as straight polarity, in this polarity the power base and base
metal connected to the positive terminal and electrode connected to the negative
terminal.
The electrons moves
from electrode with high velocity to work-piece The materials with high melting temperature
such as stainless steel , titanium is easily joint by DCEN polarity. 2/3rd of the total arc heat is generated near base plate and
rest is generated at electrode. Filler metal deposition rate is low as
compared to DEEP polarity. One thing noted that DCEN not suitable for welding
of thin plates.
Advantages :
1) In TIG (Tungsten) Welding less chance of tungsten inclusion.
2) Thick plates can also be joint properly with DCEN polarity.
3) High melting points material good for DCEN.
Disadvantages :
1) Due to low deposition productivity is low.
2) Not suitable for welding thin plates.
3) Distortion level is high.
Advantages :
1) In TIG (Tungsten) Welding less chance of tungsten inclusion.
2) Thick plates can also be joint properly with DCEN polarity.
3) High melting points material good for DCEN.
Disadvantages :
1) Due to low deposition productivity is low.
2) Not suitable for welding thin plates.
3) Distortion level is high.
2)
POSITIVE POLARITY (DCEP) :
Pic02
Pic02
Positive polarity
also called as straight polarity, in this polarity the power base and base
metal connected to the negative terminal and electrode connected to the positive
terminal.
Here electrons move from work
piece to electrode The materials with low melting temperature such
as copper, aluminum is easily joint by DCEP polarity. . 2/3rd of the total arc heat is generated at electrode and rest is generated near base
plate. Filler metal deposition rate is high because large heat generated
at electrode end. DCEP is suitable for welding of thin plates.
Advantages :
1) Less chance of inclusion defects.
2) fast welding due to high consumption of electrode.
3) suitable for join Low melting points materials.
Disadvantages :
1) non consumables electrodes short life with DCEP.
2) Incomplete penetration.
3) Incomplete melting.
Advantages :
1) Less chance of inclusion defects.
2) fast welding due to high consumption of electrode.
3) suitable for join Low melting points materials.
Disadvantages :
1) non consumables electrodes short life with DCEP.
2) Incomplete penetration.
3) Incomplete melting.
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