The shielding gas used in an arc welding process has a significant influence on the overall performance of the welding system. These gases are argon, helium, oxygen, hydrogen, nitrogen, and carbon dioxide. This article discusses the shielding gas selection criteria for plasma arc welding, gas metal arc welding, and flux cored arc welding. It describes the basic properties of shielding gases, namely, dissociation, recombination, reactivity potential, oxidation potential, and gas purity. The article also provides information on the influence of the shielding gas on weld mechanical properties and self-shielded flux cored arc welding.

Laser has found its applications in cutting, drilling, and shock-peening operations of manufacturing industry because of its accurate, safe, and rapid cutting property. This article provides an account on the fundamental principles of laser cutting (thermal), drilling, and shock-peening processes of which emphasis is placed on thermal laser cutting. It details the principal set-up parameters, such as the laser beam output, nozzle design, focusing optic position and characteristics, assist gases, surface conditions, and cutting speed. A discussion on the types of gas, supply system, purity level, and flow rates of lasing and assist gases is also provided. The article also describes the metallurgies and other key material considerations that impact laser-cutting performances and includes examples of laser cutting of nonmetal materials.

The shielding gas used in a welding process has a significant influence on the overall performance of the welding system. This article discusses the basic properties of a shielding gas in terms of ionization potential, thermal conductivity, dissociation and recombination, reactivity/oxidation potential, surface tension, gas purity, and gas density. It describes the characteristics of the components of a shielding gas blend. The article discusses the selection of shielding gas for gas-metal arc welding (GMAW), gas-tungsten arc welding (GTAW), and plasma arc welding (PAW), as well as the influence of shielding gas on weld mechanical properties. It concludes with a discussion on flux-cored arc welding.