Question: Electrode size selection

Date 06-27-2005 14:19

First review the WPS to see what your options are. The best selection is generally up to the welder. As electrode diameter increases, the current goes up. As the current increases, the technique needed to control the weld is more difficult. So, ultimately, the ability of the welder dictates the optimum electrode size (within the WPS parameters).

Charles

By G.S.Crisi (****)

Date 06-27-2005 17:32

The choice depends also on the thickness of the material to be welded (plate, pipe etc.).
Nobody would think of using a 4 mm (3/16") electrode to weld a quarter inch (6,4 mm) thick plate. It would burn the chamfers. Also, nobody would think of using a 3 mm (1/8") electrode to weld an inch (25 mm)thick plate. It would take too a long time to complete the weld. In these cases, it's advisable to make the root and the following two or three passes with a 3 mm electrode and the rest with 4 mm.
Giovanni S. Crisi
Sao Paulo - Brazil

By swnorris (****)

Date 06-27-2005 22:16

Good points by chall and the Professor. Large electrodes permit welding at high currents and high deposition rates. Therefore, use the largest electrode practical consistent with good weld quality. Electrode size is limited by many factors, but the most important considerations are: High currents increase penetration. Therefore, electrode size is limited on sheet metal and with root passes where burnthrough can occur. In general, the maximum electrode size practical for vertical and overhead welding is 3/16", with 5/32" electrode being the maximum size for low hydrogen electrodes. High DC current increases arc blow. When arc blow is a problem, either use AC or limit the current. Joint dimensions also sometimes limit the electrode diameter that will fit into the joint.
AWS D1.1 prequalified requirements for maximum electrode diameters are: Flat fillets 5/16" (except roots), grooves 1/4" (except roots), 3/16" root. horizontal: 1/4" flat fillets, 3/16" groove. Vertical and overhead 3/16" (except for 5/32" for EXX14 and low hydrogen electrodes).