The safe and effective storage and disposal of high level waste and spent fuel is a high priority for many countries worldwide. In order to store vitrified high level waste in steel canisters in a facility 500 m underground, welding process has to be developed for the closure of nuclear waste canisters.
In the current work, welding of 25 mm thick A516 Gr.70 steel plate was carried out using 30 kW fiber laser and 50 kV electron beam, respectively, for canisters closure application. The effect of laser welding speed on weld penetration was investigated. The microstructure of the weld metal and heat-affected zone was characterized. The micro-hardness across the weld joint was determined. The results showed that a 30 kW laser could produce a full penetration weld at 1.3 m/min without defects which is faster than electron beam welding did at 0.64 m/min. Under those welding conditions, both the laser and electron beam weld metals contained acicular ferrite and bainite, the maximum hardness in laser weld was around 250-300 HV, and 300-350 HV for electron beam weld.