Hi Bill,

Actually, submerged arc welding can be applied in three different modes: semiautomatic, automatic, and machine. As you know, semiautomatic welding is done with a hand held gun, and automatic welding is done with equipment that performs the welding operation without requiring a welding operator to continually monitor and adjust the controls. Machine welding employs equipment that performs the complete welding operation.
sofi-bj:
To elaborate a little on what Bill said, the sub arc process uses an arc or arcs between a bare metal electrode or electrodes and the weld pool. The arc and molten metal are shielded by a blanket of granular flux on the workpiece. The process is used without pressure and with filler metal from the electrode and sometimes from a supplemental source, i.e. welding rod, flux, or metal granules. Some of the factors that need to be considered as to whether to use sub arc or not are the chemical composition and mechanical properties required of the final deposit, the thickness of the base metal to be welded, joint accessability, the position in which the weld to be made, and the frequency or the volume of welding to be performed.