本文通过电子束形状的测定试验,研究了低真空下束流、偏压和聚焦电流变化对束焦点直径及其位置的影响,由于束流增大时焦点位置上移,指出了厚板电子束焊接中传统的“小束流对中对焦,大束流焊接”工艺方法的不合理性。本文还着重研究了在13.332Pa、133.32Pa 的低真空范围内,工作室真空度变化对于束形状的影响。并提出了确定束焦点直径及其位置的经验公式。 In this paper, the effects of beam current, bias voltage and focusing current under low vacuum on the beam focal spot diameter and its position are studied. The focal position of the beam is increased when the beam current increases. The Irrationality of the Traditional “Small Beam Flow Alignment, Big Beam Welding” Process Method in Welding. This paper also focuses on the influence of the change of working chamber vacuum on beam shape in the low vacuum range of 13.332Pa and 133.32Pa. An empirical formula for determining the beam focus diameter and its position is proposed.