ARC WELDING In arc welding the intense heat

ARC WELDING

� In arc welding the intense heat required for joining the metals is obtained from an electric arc. � Transformers are mainly used as arc welding machines. � These machines supply high electric currents at low voltages & an electrode is used to produce the necessary arc. � The arc is formed between the actual workpiece and an electrode (stick or wire) that is manually or mechanically guided along the joint. � The electrode serves as the filler rod. � Arc melts the surfaces so that the metals to be joined are actually fused together.

FLUX � Weld strength – Cr, V, Ni, Co � Arc stabilizers - Ca. O, Mn. O � Slag formation compound – ferrous oxide � Deoxidizing element - Al, Graphite, Silica

Principle of Arc is generated between two conductors of electricity, cathode & anode, when they are touched to establish the flow of current and then separated by a small distance. Arc is sustained electric discharge through the ionized gas column, called plasma, between the two electrodes. (An arc is an electric current flowing between two electrodes through an ionized column of gas. A negatively charged cathode and a positively charged anode create the intense heat of the welding arc. Negative and positive ions are bounced off of each other in the plasma column at an accelerated rate. )

Functions of Arc q Arc provides the heat needed to melt the electrode and the base metal q It also supply the means to transport the molten metal from the tip of the electrode to the work. (a drop of molten metal touches the molten metal pool and is drawn into it)

In addition to the welding machine, certain accessories are needed for carrying out the welding work. Electrode holder is connected to the end of the welding cable and holds the electrode. It should be light strong and easy to handle and should not become hot while in operation. The jaws of the holder are insulated offering protection from electric shock.

Ground clamp It is connected to the end of the cable and clamped to the workpiece (table on which workpiece is placed) to complete the circuit.

Chipping hammer & wire brush They are used for removing slag formation on welding Face shield A face shield is used to protect eyes and face from the arc and from spatter of flying particles of hot metal