14.1 PARALLEL MAGNETIC FIELD

According to the Flemming’s left hand rule, the arc, under the influence of parallel field will be deflected towards right or left across the weld bead length depending upon the direction of the parallel field (forward or backward). Keeping this in mind the findings of the earlier investiga­tors may be analysed. Deminskii and Dyatlov have reported work on aluminium-magnesium alloys using the GMA process and alternating parallel magnetic field. They found the arc oscillated across the weld axis. Bachelis & Mechev found that on increasing the magnetic field - strength, penetration into the parent metal decreased and weld-width increased. Serdyuk confirmed the above findings and found further that with parallel field fine droplets trans­ferred with improved heat distribution perpendicular to weld seam.

14.2 TRANSVERSE MAGNETIC FIELD

According to the Flemming’s left hand rule the arc under the influence of this type of field will be deflected forward or backward depending upon the direction of the magnetic lines of force and the polarity of the welding system. Work of the earlier investigators may be analysed keeping this in mind.

Kovalev showed that the transverse magnetic field can be used for automatically regu­lating the depth of penetration. Hicken and Jackson found beneficial effects of constant trans­verse magnetic field when the arc was deflected forward with respect to the electrode travel speed. It was possible to increase welding speed four times and still obtain welds free from undercuts. Weld width was found to reduce with increase in magnetic field during stainless steel welding. For aluminium, however, weld width increased with increase in magnetic field (0 - 50 gauss). Mandelberg successfully increased the welding speed of submerged arc welding process. Kornienko found they for hard facing, required depth of penetration on higher cur­rents and deposition rates could be obtained using transverse magnetic field. Sheinkin found the application of transverse magnetic field to increase the productivity of the submerged arc welding process used for making butt joints between prepared edges.