Page 120 - CITS - Welder - Trade Theory

WELDER - CITS

Effects of moisture pickup and backing of electrode

Objectives : At the end of this lesson you shall be able to
• explain about special purpose electrodes and their application
• state the necessity of baking a coated electrode
• store and handle the electrode properly for better weld quality.

Storage of electrodes: The efficiency of an electrode is affected if the covering becomes damp.
a Keep electrodes in unopened packets in a dry store.
b Place packages on a duckboard or pallet, not directly on the floor.
c Store so that air can circulate around and through the stack.
d Do not allow packages to be in contact with walls or other wet surfaces.

e The temperature of the store should be about 5°C higher than the outside shade temperature to prevent
condensation of moisture.
f Free air circulation in the store is as important as heating. Avoid wide fluctuations in the store temperature.
Where electrodes cannot be stored in ideal conditions place a moisture-absorbent material (e.g. silica-gel) inside
each storage container.
Store and keep the electrodes (air tight) in a dry place.
Bake the moisture affected/prone electrodes in an electrode drying oven at 110-150°C for one hour before using.
(Fig 1)

Fig 1

Electrode coating can pick up moisture if exposed to atmosphere.
Baking electrodes: Water in electrode covering is a potential source of hydrogen in the deposited metal and
thus may cause
a Porosity in the weld
b Cracking in the weld.

Indications of electrodes affected by moisture are:
a White layer on covering.
b Swelling of covering during welding.
c Disintegration of covering during welding.

d Excessive spatter
e Excessive rusting of the core wire.

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CITS : CG & M - Welder - Lesson 27 - 30 CITS : CG & M - Welder - Lesson 27 - 30