Welding Principles and Applications 7th chapter 12 Q 13 is

Welding : Principles and Applications - 7th chapter 12 Q 13, is there any problem with using a shielding gas on an ECAW electrode?

Solution

Shield gas are semi inert gas that are commonly used with notably gas metal arc welding and gas tungsten arc welding. The purpose is to protect the weld area from oxygen and water vapour. The electrode are manufacture in three general types, those having cellulose coating, those having mineral coating and those coating have combination of both the combination of mineral and cellulose The cellulose coating are composed of soluble cotton with small amount of potassium, sodium or titanium and some cases added minerals. The mineral consists of sodium silicate, metallic oxides clay and inorganic substances.

The welding electrodes produces a reducing gas shield around the arc. This prevents atmospheric oxygen and nitrogen from combination of weld metal, the oxygen combines with the molten metal, removing alloying elements and cause porosity. Nitrogen cause brittleness, low ductility and in some cases low strengthened poor resistance to corrosion.

In certain elements or oxides are present in electrode coatings, the arc stability will be affected. In bare electrodes the compositions and uniformity of the wire is a important factor to be consider.

We can use ECAW electrode but it consider following parameter:-

1 – Force between the molten metal and the end of the electrodes.

2 – Temperature and voltage control because welding electrodes produce a reducing gas shield around the arc, this prevents atmospheric oxygen or nitrogen from contain the weld metal