What issues should be noted when starting an arc?

Semi automatic CO2 welding usually uses the burst arc ignition method. Before starting the arc, it is necessary to select an appropriate starting position to maintain a certain distance

between the welding wire and the workpiece. Press the start button on the welding gun, and the welding wire will be sent in and come into contact with the workpiece. The welding wire

will melt and explode under the action of a large short-circuit current, igniting the arc.

The key to reliable arc striking is to make the welding wire slightly contact the workpiece. If the contact is too tight or poor, it can cause the welding wire to burn out too long, leading to

severe splashing and insufficient melting depth at the arc striking point. Therefore, the following points should be noted:

① Before starting the arc, the extension length of the welding wire must be adjusted appropriately to maintain a distance of 2-3mm between the welding wire end and the weldment, and

the distance between the conductive nozzle and the weldment is 10-15mm, as shown in Figure (a). The operation method is to press the control switch on the welding gun and jog the wire

feed, so that the extended length of the welding wire is less than the distance between the nozzle and the workpiece by 2-3mm.

② If there is a metal melt ball at the end of the welding wire, it must be cut off with pliers, otherwise it can easily cause serious splashing and weld defects at the arc starting point, and even

difficult to achieve reliable arc starting.

③ After the welding wire comes into contact with the workpiece, the welding gun tends to be pushed up by the welding wire. Therefore, it is necessary to apply slight force to press down the

welding gun to prevent the arc from extinguishing due to elongation.

④ When welding important welds or automatic welding, it is best to add a striking arc plate and strike the arc on the striking arc plate.

⑤ If the arc striking plate cannot be added, during semi-automatic welding, the arc is generally struck at a distance of 10-20mm from the starting welding end. After the arc stabilizes, the arc

is moved towards the starting welding end, as shown in Figure (b).

In general, the initial welding end is prone to defects such as excessive weld bead and insufficient penetration. To avoid these defects, first elongate the arc slightly, preheat the end appropriately,

and then compress the arc to its normal length for normal welding. To avoid defects such as incomplete penetration, penetration, and porosity at the arc initiation point of the weld.

⑥ If the arc striking plate cannot be added, during automatic welding, it is generally necessary to move quickly at the arc striking point to obtain a narrower weld bead and create conditions for the

weld bead joint.