Welding in Magnetic Fields

[MontejanoWelder]

i m welding water heaters, when torch is close to the end the arc deflect.
i think that is for magnetic field in .
some one told me that i can change from DC to AC, to dissmiss this problem

What parameters i need to change? filler metal, flux, voltage, current?

welding parameters are:
travel speed 100 in*min
current 34-35amp
voltage 21-28 volts
feed speed 94 in * min
base metal 1008 1.5 mm thickness