Function of electrode coating

Constant Current Characteristics

Constant Current Characteristics

Constant Voltage Characteristics

Open-circuit voltage

✓ Open-circuit voltage (abbreviated

as OCV or VOC ) is the difference of

electrical potential between two terminals

of a device when disconnected from any

circuit.

✓ There is no external load connected. No

external electric current flows between the terminals.

Straight Polarity Reverse Polarity

Electrode is connected with the negative terminal of the power source and base metals are connected with the positive

terminal.

Base metals are connected with the negative terminal of the power source and electrode is

connected with the positive terminal.

Under sufficient potential difference, electrons liberate from the tip of the

electrode and strike the base plate surface.

Here electrons liberate from base plate surface and strike the electrode tip.

2/3rd of the total arc heat is generated near base plate and rest is generated at electrode

tip.

2/3rd of the total arc heat is generated at electrode tip and rest is generated near base

plate.

Proper fusion of the base metal can be achieved easily. So it eliminates the lack of

fusion and lack of penetration defects.

Due to less heat generation near base plate, incomplete fusion of the base plate may

occur.

Straight Polarity Reverse Polarity

In case of consumable electrodes, filler metal deposition rate is quite low.

Filler metal deposition rate is quite high as greater portion of heat is generated at

electrode tip.

Arc voltage and arc stability does not depend on work material emissivity.

Arc voltage and arc stability significantly depend on work material emissivity.

Arc cleaning action (oxide cleaning) is poor. Arc cleaning action is good.

Inclusion defects may arise if base plate surfaces are not cleaned properly prior to the

welding.

Due to good arc cleaning action, tendency of inclusion defects reduces.

DCSP may cause high distortion and broader HAZ in the welded component.

Distortion is less with DCRP and also HAZ is narrow.

DCSP is not suitable for welding thin plates. DCSP is suitable for welding thin plates.

Metals with high melting temperature (such as stainless steel, titanium) can be suitably

joined by DCSP.

Metals with low melting temperature (such as copper, aluminum) can be suitably joined by

DCSP.

(GATE – 16 – SET – 2)

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