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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
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