Abstract: Two mathematical models are developed to describe the oscillating amplitude of the plasma arc along the metal surface and the heat flow density distribution of plasma arc on the metal surface respectively.The behavior of plasma arc jet under an external transverse sinusoidal alternating magnetic field imposed perpendicular to the plasma current is analyzed theoretically,and the effect of process parameters such as gas flow rate,arc current,magnetic flow density and the distance from the nozzle outlet to the anode workpiece on the form and distribution of plasma arc are also in vestigated.The results show that it is feasible to control the shape and heat flow density of the plasma arc for the transverse alternating magnetic field,which can expand the area of plasma arc thermal treatment and flat the heat flow density upon the workpiece.Furthermore,the oscillating amplitude of plasma arc increases and the heat flow density gradient upon the workpiece decreases with the magnetic flow density enhancing.However,an overly strong magnetic field coil results in the plasma arc unstable.Under the same magnetic flow density,less gas flow rate and arc current,longer distance from the nozzle outlet to the anode causes the oscillating amplitude to increase.Contrarily,the more gas flow rate and arc current,the more heat flow density peak increases.Moreover,longer distance from nozzle outlet to workpiece descends the heat flow density peak.