There are two operating methods for vertical electrode arc welding: one is welding from bottom to the top, called upward vertical welding; the other is welding from top to the bottom, called downward vertical welding. At present, the most widely used method in production is downward vertical welding.
1. Upward Vertical Welding
l) In upward vertical welding, a smaller diameter electrode (2.5mm~4mm) and a smaller welding current (10%~15% smaller than that of flat butt welding) should be selected, so as to obtain smaller and faster cooling/ solidification molten pool, which can prevent molten metal trickled down.
2) Short-arc welding is adopted, the arc length is not greater than the diameter of the electrode. The arc blowing force is used to support the molten pool, and the short-arc operation is also beneficial to the droplet transfer.
3) The working angle of the electrode is 90°, and the forward inclination angle is -10~-30°, that is, the electrode is inclined in the opposite direction of the welding direction, so that the arc blowing force generates an upward thrust on the molten pool to prevent the molten metal from dripping down.
4) In order to facilitate right-handed operation and better observe the molten pool, the welder's body should not be directly facing the weld bead, but slightly to the left.
2. Downward Vertical Welding
The downward vertical welding method is only suitable for the welding of thin plates and less important structures, because the molten metal and slag in downward vertical welding are more likely to fall than upward vertical welding, and the weld is prone to defects such as slag inclusions and pores. The downward vertical welding method is characterized by fast welding speed. The penetration depth is shallow, the fusion width is narrow, it is not easy to burn through, the weld bead shape is beautiful, and the operation is simple.
Its operating points are as follows:
1) Welding current should be moderate to ensure good fusion;
2) When welding, make the electrode perpendicular to the surface of the weldment and use the direct strike method to ignite the arc. The electrode uses a large forward angle of the electrode, about 30~40°, and uses the arc blowing force to support the molten pool to prevent the molten metal from dripping down;
3) Use the straight line method in electrode traveling and avoid lateral swinging as much as possible. However sometimes slightly swinging laterally is needed to obtain good fusion between the two sides of the weld and the base metal.
4) It is best to use specially designed electrodes for downward vertical welding (such as 6013VD) with relatively high slag viscosity. In addition to AC welding machines, ordinary DC arc welding machines should be welded with DC reverse connection.
