**1. Introduction**

In this chapter, we will first introduce you to the field of welding processes using different welding variables examples. We will then provide an introduction to the classification of welding variables. Although most engineering programs or mechanical engineering programs require students to take welding technology courses, you should approach your study of welding technology as more than a mere requirement. Thorough knowledge of welding processes will make you a better engineer and designer. Welding science underlies all technological advances and an understanding of the basics of welding and its applications will not only make you a better engineer but will help you during the production process. In order to be a perfect designer, you must learn what welding will be appropriate to use in different applications. Also, in this chapter, previous works related to the current study are discussed. Various welding techniques will be presented. Finally, studies focused on welding and the effect of welding variables on stainless steel will be discussed. GTAW is considered

one of the most productive welding methods since it is used in the welding of metals with high thickness. For this reason, it is used in the heavy industry and shipbuilding industry.

The shielding gas interacts with the base material and with the filler material, if any, to produce the basic strength, toughness, and corrosion resistance of the weld. It also affects weld bead shape and penetration pattern [1, 2]. Successful GTAW weldments of Monel 400 and AISI 304 were developed using ER304, ERNiCrMo-3, and ERNiCrMo-4 welding wires [3]. The tensile strength and yield strength of ERNiCrMo-3 weldments were comparable to those of parent metals. Tensile strength and yield stress of dissimilar ERNiCrMo-3 weld joints were better than ER304 and ERNiCrMo-4 weldments. Also, the effect of welding wires on the characteristics of dissimilar welding of SS316 L and carbon steel A516 GR 70 was studied [4] using three different filler materials ER80-Ni1, ER309L, and ER NiCrMO-3 (Inconel 625). Inconel 625 was found more suitable to weld dissimilar SS316 L and carbon steel A516 GR 70. Best results concerning UTS, and hardness were obtained using Inconel 625 as a welding electrode. The effect of welding electrodes on the characteristics of dissimilar AISI 420 and 304 L welds was studied [5] using three different filler rods ER312, ER316 L, and ER2209. The last rod produced welds with the highest impact toughness and lowest hardness. Kanigalpula et al. [6] developed mathematical models using central composite design methodology 'CCD' to determine the process variables that produce more stable weld bead geometry and microhardness in the electron beam welding process. Hackenhaar et al. [7] applied Box-Behnken design 'BBD' to investigate the effect of gas metal arc welding 'GMAW' parameters (wire feed speed, welding speed, and arc voltage) based on 3 responses (melting efficiency, bead on plate, and melting area of T-joint) in GTAW butt welding of 6.35 mm thick AISI 1010 steel plates. The melting efficiency showed a direct relationship with heat flow extraction in weld joint, thus, of joint geometry. Melting efficiency is lower for T-joint regardless used equation.
