Modified flux system in cored electrode

Abstract

A welding system and cored welding electrode composition is disclosed for performing a short arc welding process between an advancing wire electrode and a workpiece. The system comprises a power source with a controller for creating a current pulse introducing energy into the electrode to melt the end of the electrode and a low current quiescent metal transfer section following the end of the melting pulse during which the melted electrode short circuits against the workpiece; a timer to measure the actual time between the end of the pulse and the short circuit; a device for setting a desired time from the pulse to the short circuit; a circuit to create a corrective signal based upon the difference between the actual time and the desired time; and, a circuit responsive to the corrective signal to control a given parameter of the current pulse.

What is claimed is: 
     
         1 . A self-shielded flux cored arc welding (FCAW-S) electrode particularly adapted for forming welds having reduced levels of contaminants using an AC waveform, the electrode fill having an alloy/flux system comprising:
 from ˜35 wt % to ˜55 wt % barium fluoride;   from ˜2 wt % to ˜12 wt % lithium fluoride;   up to ˜15 wt % lithium oxide;   up to ˜15 wt % of barium oxide; and   from ˜5 wt % to ˜20 wt % iron oxide.   
     
     
         2 . The electrode as defined in  claim 1 , the alloy/flux system further comprising:
 up to ˜25 wt % of at least one deoxidation and denitriding agent selected from the group consisting of aluminum, magnesium, titanium, zirconium, and combinations thereof.   
     
     
         3 . The electrode as defined in  claim 1  wherein the alloy/flux system further comprises:
 up to ˜8 wt % barium carbonate. 
 
     
     
         4 . The electrode as defined in  claim 1  wherein the alloy/flux system further comprises:
 up to ˜8 wt % lithium carbonate. 
 
     
     
         5 . The electrode as defined in  claim 1  wherein the alloy/flux system further comprises:
 up to ˜5 wt % calcium oxide. 
 
     
     
         6 . The electrode as defined in  claim 1  wherein the alloy/flux system further comprises:
 up to ˜5 wt % silicon oxide. 
 
     
     
         7 . The electrode as defined in  claim 1  wherein the alloy/flux system further comprises:
 up to ˜5 wt % manganese oxide. 
 
     
     
         8 . The electrode of  claim 2  wherein the alloy/flux system further comprises:
 up to ˜8 wt % barium carbonate; 
 up to ˜8 wt % lithium carbonate; 
 up to ˜5 wt % calcium oxide; 
 up to ˜5 wt % silicon oxide; and 
 up to ˜5 wt % manganese oxide. 
 
     
     
         9 . The electrode of  claim 1  wherein the electrode fill constitutes
 from ˜18 wt % to ˜24 wt % of the electrode. 
 
     
     
         10 . A flux cored electrode adapted to form a weld metal having a minimum Charpy V-Notch toughness of 60 J at −20° C. upon short arc welding, the electrode comprising a core having an alloy/flux system comprising:
 from ˜35 wt % to ˜55% wt % barium fluoride; 
 from ˜2 wt % to ˜12 wt % lithium fluoride; 
 up to ˜15 wt % lithium oxide; 
 up to ˜15 wt % barium oxide; and 
 from ˜5 wt % to ˜20 wt % iron oxide. 
 
     
     
         11 . The electrode as defined in  claim 10  wherein the alloy/flux system further comprising
 up to ˜25 wt % of a deoxidation and denitriding agent selected from the group consisting of aluminum, magnesium, titanium, zirconium, and combinations thereof. 
 
     
     
         12 . The electrode as defined in  claim 10  wherein the electrode further comprises:
 up to ˜8 wt % barium carbonate. 
 
     
     
         13 . The electrode as defined in  claim 10  wherein the electrode further comprises:
 up to ˜8 wt % lithium carbonate. 
 
     
     
         14 . The electrode as defined in  claim 10  wherein the electrode further comprises:
 up to ˜5 wt % calcium oxide. 
 
     
     
         15 . The electrode as defined in  claim 10  wherein the electrode further comprises:
 up to ˜5 wt % silicon oxide. 
 
     
     
         16 . The electrode as defined in  claim 10  wherein the electrode further comprises:
 up to ˜5 wt % manganese oxide. 
 
     
     
         17 . The electrode as defined in  claim 10  wherein the alloy/flux system further comprises:
 up to ˜8 wt % barium carbonate; 
 up to ˜8 wt % lithium carbonate; 
 up to ˜5 wt % calcium oxide; 
 up to ˜5 wt % silicon oxide; and 
 up to ˜5 wt % manganese oxide. 
 
     
     
         18 . A flux cored electrode adapted to produce weld metal having a tensile strength greater than 90 ksi upon short arc welding, the electrode comprising a core having an alloy/flux system comprising:
 from ˜35 wt % to ˜55% barium fluoride;   from ˜2 wt % to ˜12 wt % lithium fluoride;   up to ˜15 wt % lithium oxide;   up to ˜15% barium oxide; and   from ˜5 wt % to ˜20 wt % iron oxide.   
     
     
         19 . The electrode as defined in  claim 18  wherein the alloy/flux system further comprising
 up to ˜25 wt % of a deoxidation and denitriding agent selected from the group consisting of aluminum, magnesium, titanium, zirconium, and combinations thereof. 
 
     
     
         20 . The electrode as defined in  claim 18  wherein the electrode further comprises:
 up to ˜8 wt % barium carbonate. 
 
     
     
         21 . The electrode as defined in  claim 18  wherein the electrode further comprises:
 up to ˜8 wt % lithium carbonate. 
 
     
     
         22 . The electrode as defined in  claim 18  wherein the electrode further comprises:
 up to ˜5 wt % calcium oxide. 
 
     
     
         23 . The electrode as defined in  claim 18  wherein the electrode further comprises:
 up to ˜5 wt % silicon oxide. 
 
     
     
         24 . The electrode as defined in  claim 18  wherein the electrode further comprises:
 up to ˜5 wt % manganese oxide. 
 
     
     
         25 . The electrode as defined in  claim 18  wherein the alloy/flux system further comprises:
 up to ˜8 wt % barium carbonate; 
 up to ˜8 wt % lithium carbonate; 
 up to ˜5 wt % calcium oxide; 
 up to ˜5 wt % silicon oxide; and 
 up to ˜5 wt % manganese oxide.