Abstract: Method and an apparatus whereby electron beam deep welding can be performed at pressures of more than 10 millibars, especially under atmospheric conditions, without the need for complex apparatus. This is achieved by guide surfaces disposed between a seam and an electron beam source, so as to reflect the diverging electrons and at the same time reduce the free access of the ambient gas atmosphere. The electron reflection and the simultaneous blocking off of gases is achieved by guide surfaces substantially parallel and symmetrical with the beam axis which extend along the beam for at least ten millimeters. The distance between the guide surfaces through the center of the electron beam is greater than the diameter which the beam has upon entering into the higher pressure area.