STT welding the surface tension transfer process developed by Lincoln Electric of Cleveland, Ohio has helped solve a fixing problem for welders working on the roof of the new Bluewater shopping centre at Greenhithe, near Dartford, Kent.
Difficulties arose when it came to fabricating steel dumb-bells to strengthen beams for the roof trusses. The procedure involved welding 110mm plate to tubing of 20mm wall thickness. With conventional MIG welding, the difference in material thicknesses prevented sufficient penetration of the root weld into the material. As a result, the fabrication failed under testing.
Unlike the usual MIG method, STT welding controls the electrode current precisely during the entire welding cycle. The system can change electrode current in microseconds. It is neither a constant current nor constant voltage system, but is a welding mode where the electrode current is based on the instantaneous heat requirements of the arc.