Arc welding
From Halopedia, the Halo wiki
Arc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. The welding region is sometimes protected by some type of inert or semi-inert gas, known as a shielding gas, and/or an evaporating filler material. The process of arc welding is widely used because of its low capital and running costs.
In Halo canon, it is assumed that the Arc welder is used for roughly the same purposes since its introduction in the late 1800's, which is quite simply welding two or more pieces of ferrous metal together using an alternating current.
