Possibility of controlling the reverse side bead formation during electron beam welding by detection and control of the eleccron beam current which pierces through the base plate (the piercing beam current) has been investigated.
Three types of electron beam welding machines were used in this study. The first one is a 6 kW (150 kV×40 mA) high vacuum type, the second is a 15 kW (30 kV×500 mA) low vacuum type, and the third is a 42 kW (60 kV×700 mA) high vacuum type machine respectively. All welding were performed in the flat position.
It was concluded from the study that,
(1) It is possible to form smooth and stable reverse side bead by controlling the piercing beam current.
(2) There is a large fluctuation in the wave form of the piercing beam current. When the piercing beam current signal is integrated by an integrator with appropriate time constant, the mean value of the signal can be adopted as the monitoring signal for the formation of appropriate reverse side beads.
(3) A test controller of the piercing beam current was attached to the 15 kW (30 kV × 500 mA) EB welding machine, and bead-on-plate welding tests were performed on carbon steel pipe (SGP) of 15 mm in thickness. Smooth and stable reverse side beads are formed when the mean of the piercing beam current is 15 to 20 mA, the focus coil current is 2.94 A and welding speed is 400 to 500 nun/min.
