Care must be taken to ensure that the weld pool is positioned, relative to the top dead centre, so that freezing of the pool and the associated molten slag takes place effectively in the flat position at the top dead centre. Similarly the flux must be retained in position and prevented from falling away from the weld zone. The tendency for weld pool and slag spillage is aggravated by using high heat inputs, particularly with smaller diameter work pieces. Figure 1 shows three possible positions of the electrode and of these, position 2 usually gives the best results as regards bead appearance and slag removal. Position 1 gives the worst bead appearance and such an arrangement can be difficult to control on small diameter workpieces as the molten slag tends to run ahead of the arc.
Fig.1 Electrode positions for circumferential welding and resulting bead shapes
|External diameter of workpiece, mm||Electrode displacement, mm|
Fig.2 Electrode displacements from TDC for circumferential welding