Final answer:
Gas metal arc welding and flux cored arc welding can operate with or without a shielding gas, while electrogas welding and submerged arc welding require a shielding gas.
Step-by-step explanation:
The gas metal arc welding process can operate with or without a shielding gas. In this process, a consumable metal electrode is used and an inert gas, such as argon or helium, may be used as a shielding gas to protect the weld pool from atmospheric contamination. However, some variations of gas metal arc welding, such as metal-cored arc welding, do not require a shielding gas.
The flux cored arc welding process can also operate with or without a shielding gas. This process uses a tubular electrode filled with flux, which produces a shielding gas when heated. However, some flux cored wires are designed to operate without a shielding gas.
On the other hand, the electrogas welding process and submerged arc welding process both require a shielding gas. The electrogas welding process uses a consumable metal electrode and a flux to generate the shielding gas. The submerged arc welding process uses a solid or tubular electrode and a flux, with a continuous blanket of granular flux being fed over the weld zone to provide shielding.