Each discharge in electrical discharge machining (EDM) generates a plasma with a temperature of several thousands of degrees, which not only evaporates and melts the electrode material, but also applies forces on the molten pool. To determine the role of the discharge plasma on the molten pool dynamics, this study used high-speed photography technology and the finite element method (FEM) to investigate the discharge process. The observation results of the discharge process without an external magnetic field demonstrate that the randomly moving plasma caused the movement of the molten pool, which can have an influence on the removal of the molten material and the final crater topography. It is thought that the randomly moving plasma applied a moving pressure and a moving shear force on the molten pool, causing its movement. The discharge process was observed under an external transverse magnetic field, which indicated that under the action of the Lorentz force, the plasma did not move randomly but moved along the direction of the Lorentz force. The molten pool flowed along the trailing direction of the plasma, and large molten materials were removed from the molten pool along the same direction. The transverse magnetic field influenced the removal of the molten material and the movement of the molten pool by influencing the plasma which actually applied a pressure and a shear force on the molten pool. Finally, the simulation results demonstrate that under the action of the plasma pressure, the molten material was extruded from the molten pool, and the bulge around the discharge crater was generated gradually, forming a deep and bowl-shaped discharge crater with a static plasma and a shallower and larger diameter discharge crater with a moving plasma.

放电加工（EDM）中的每次放电都会产生具有数千度温度的等离子体，该等离子体不仅会蒸发和熔化电极材料，而且还会在熔池上施加力。为了确定放电等离子体在熔池动力学中的作用，本研究使用高速摄影技术和有限元方法（FEM）来研究放电过程。没有外部磁场的放电过程的观察结果表明，随机运动的等离子体引起了熔池的移动，这可能对熔融材料的去除和最终的坑口形貌产生影响。据认为，随机移动的等离子体在熔池上施加了移动压力和移动剪切力，导致其移动。在外部横向磁场下观察到放电过程，这表明在洛伦兹力的作用下，等离子体不是随机移动而是沿洛伦兹力的方向移动。熔池沿等离子体的尾流方向流动，并且沿相同方向从熔池中除去大量的熔融材料。横向磁场通过影响实际上在熔池上施加压力和剪切力的等离子体来影响熔液的去除和熔池的运动。最后，仿真结果表明，在等离子压力的作用下，熔融材料从熔池中挤出，并逐渐在放电弹坑周围产生凸起，