EFFECT OF MAGNETIC STEERING OF THE ARC ON CLAD QUALITY IN SUBMERGED-ARC STRIP CLADDING

Submerged arc strip cladding is often used when thickness of clad material is required. The productivity of this process has been improved by the use of higher welding currents and wider strips. The associated problems were arc blow, increased penetration and poor bead characteristics. Dilution is the parameter that controls almost all qualities of cladding. Magnetic steering reduces penetration, and hence, dilution and arc blow control. Stainless steel cladding on mild steel is often used to impart corrosion resistance. In such situations, the clad quality is specified by corrosion resistance, ferrite content and good fusion between clad metal and base metal. This paper discusses results of an investigation on the effect of an oscillating magnetic field used to steer the arc in submerged arc strip cladding using 60 X 0.5-mm 309L stainless steel strips, with varying magnetizing flux intensity and dwell time. The resulting test pieces were evaluated for parameters that imparted the best clad quality and the results indicate the following: 1) Magnetic steering of the arc reduces dilution and corrosion rate. 2) Magnetic steering of the arc permits use of higher currents for a given dilution level, thus increasing productivity. 3) Clad metal microstructures of a desirable type are obtained when the arc is magnetically steered. 4) Use of 309L strips for single layer cladding appears to be satisfactory since ferrite content lies between 5 to 10% for a variety of welding conditions. 5) The corrosion rate (microns per 24 hours) is linearly related to the dilution percentage of the clad metal.